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Development of a computer-controlled device to quantitatively measure the degree of spasticity at a subject’s… Aitchison, Jeffrey R. 1996

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D E V E L O P M E N T O FA C O M P U T E R - C O N T R O L L E D DEVICE TO QUANTITATIVELY MEASURE THE DEGREE OF SPASTICITY A T A SUBJECT'S  ANKLE  by Jeffrey R. Aitchison B.Sc. University of Manitoba, 1992  A T H E S I S S U B M I T T E D IN P A R T I A L F U L F I L L M E N T OF T H E REQUIREMENTS O F T H E D E G R E E OF MASTERS O F APPLIED  SCIENCE  in T H E F A C U L T Y O F G R A D U A T E STUDIES  Department of Mechanical Engineering We accept this thesis as conforming to the required standard  T H E U N I V E R S I T Y O F BRITISH C O L U M B I A December, 1996 © Jeffrey Aitchison, 1996  In  presenting  degree freely  at  this  the  thesis  in  University of  partial  fulfilment  of  of  department  this or  publication of  thesis for by  his  or  requirements  British Columbia, I agree  available for reference and study. I further  copying  the  agree  scholarly purposes may her  representatives.  that the  be  It  this thesis for financial gain shall not  is  of  M&MAA)\rArt.  The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  an  granted  by the  understood  be allowed  t2Vrt/-A//rA&JJ£  advanced  Library shall make  that permission for  permission.  Department  for  that  it  extensive  head  of  copying  my or  without my written  ABSTRACT  The objective of this thesis project was to develop a device to quantitatively measure the degree of spasticity at a subject's ankle, and to use this device to find a means to determine a quantified measure of spasticity.  The device imposes a controlled passive rotation of a  subject's ankle joint, while simultaneously recording the resulting resistive torque and associated electromyographic ( E M G ) muscle activity.  Comparative analysis of Data from  subjects with and without spasticity were compared to identify response characteristics and parameters which could be associated with the presence and/or severity of spasticity. These differences were evaluated by modeling the data with a mathematical equation representing spasticity response.  Parameters of the equation were then analyzed, and two of the four  parameters deemed to be robust, reliable indicators of spasticity, were plotted to create a diagnostic model and curve for distinguishing between test subjects with and without spasticity.  The perpendicular distance of the data points from the model curve can then be  utilized as a quantified measure of spasticity.  This quantified measure of spasticity was  found to correlate with clinical evaluations. The analysis of variance test determined a 7 . 8 % probability that the sets of data, from subjects with and without spasticity, were from the same population, indicating that there was a significant difference between the two data sets . Thus it is concluded that a diagnostic model has been developed which shows potential as a means to quantify spasticity.  Table of Contents  TABLE OF CONTENTS  ABSTRACT  "  LIST OF TABLES  vi  LIST OF FIGURES  vii  ACKNOWLEDGMENTS  ix  CHAPTER 1: INTRODUCTION  1  1.1  Definition of Spasticity  2  1.2  Measurement of Spasticity  4  1.3  Research Objectives  5  1.4  Thesis Overview  8  CHAPTER 2: LITERATURE REVIEW  10  2.1  Overview  10  2.2  Current understanding of spasticity  11  2.2.1  Stretch reflex  12  2.2.2  Muscle stiffness  13  2.2.3  Effects of spasticity  18  2.3  Clinical measurement of spasticity  ,  19  2.4  Quantification of spasticity  22  2.4.1  Device assisted methods of measurement  24  2.4.2  Motor controlled measurement  27  2.5  Initial Prototype Development  36  2.6  Conclusions and Summary  39  -iii-  Table of Contents  C H A P T E R 3: D E V I C E A N D P R O T O C O L D E V E L O P M E N T  42  3.1  Overview  42  3.2  Limitations of the Prototype Device  42  3.3  System Development  44  3.3.1  Required Design Modifications to the Motor  46  3.3.2  Required Design Modifications to the Driveline  49  3.3.3  Safety Components  50  3.3.4  Control Software Design  56  3.3.5  Design Modification to the Data Acquisition System  58  3.4  Testing Procedures  C H A P T E R 4: D A T A A N A L Y S I S , R E S U L T S A N D D I S C U S S I O N  61  66  4.1  Overview  66  4.2  Data Analysis  66  4.3  Evaluation of Results  68  4.3.1  Evaluation of Data from Subjects Without Spasticity  72  4.3.2  Evaluation of Data from Subjects With Spasticity  77  4.3.3  Comparison of Data from Subjects With and Without Spasticity  86  4.3.4  Quantification of Results  94  4.4  Statistical Significance of the Test Results  4.5  Comparisons with Previous Work  101  4.6  Summary  102  C H A P T E R 5: C O N C L U S I O N A N D R E C O M M E N D A T I O N S F O R F U T U R E W O R K  99  104  5.1  Conclusions  104  5.2  Recommendations for Future Work  106  REFERENCES  110  APPENDIX A - DESIGN CALCULATIONS  117  APPENDIX B - COMPUTER CODE  120  -iv-  Table of Contents  APPENDIX C - ETHICS REVIEW INFORMATION  136  APPENDIX D - DATA ANALYSIS CODE  139  -v-  Table of Contents  List of Tables  Table 2.3-1  Ashworth scale for grading spasticity [35]  20  Table 2.3-2 Modified Ashworth scale for grading spasticity [36]  21  Table 3.3.3-1: Variable slippage clutch testing results  51  Table 3.3.3-2: Shear pin testing results  55  Table 4.3.3-1 Equation parameters for each test subject at various velocities  91  Table 4.3.4-1 Quantified measurements of spasticity for all subjects  97  -VI-  List of Figures  List of Figures  Figure 1.1-1  3  Schematic representation of the effects of spasticity  Figure 2.2.2- 1 Three element muscle model [21]  14  Figure 2.2.2- 2 Passive and reflex stiffness mechanisms [22]  15  Figure 2.2.2- 3 Model basic to visco-elastic properties of muscle and tendon [20]  16  Figure 2.6-1  Example of Trapezoidal Position vs. Time Profiles  37  Figure 3.3-1  Schematic diagram of the computer-controlled system to quantitatively measure spasticity  Figure 3.3.1--1 System response comparison of the two stepper motors  45 47  Figure 3.3.3--1 Relationship between the ordinal scale on the variable slippage clutch and actual torque values  52  Figure 3.3.3--2 Schematic of testing jig used to measure torque to failure of shear pins 53 Figure 3.3.3--3 Torque to failure results compared to fitted equation  54  Figure 3.4-1  64  Depiction of the rotation of the ankle joint during testing  Figure 4.3-1 Typical resistive torque versus time curve of a subject without spasticity at 207s..  68  Figure 4.3.1--1 Resistive torque responses of a subject without spasticity to passive rotation about the ankle joint within a test session (207s)  73  Figure 4.3.1--2 Averaged torque response of a subject without spasticity to a passive rotation about the ankle joint at 207s  74  Figure 4.3.1--3 Comparison of averaged torque vs. time curves of different velocities  75  Figure 4.3.1--4 Averaged torque vs. normalized time curves of different velocities  76  Figure 4.3.1 -5 Control E M G response (207s), including position of the test (in green)..77 Figure 4.3.2 -1 Resistive torque responses of a subject with spasticity to passive rotation about the ankle joint within a test session (407s)  78  Figure 4.3.2 -2 Average torque vs. time curves of three subjects with varying degrees of spasticity at 307s  19  -vii-  List of Figures  Figure 4.3.2-3 M i l d spasticity E M G activity correlated with position of test (507s)  81  Figure 4.3.2-4 Severe spasticity E M G activity correlated with position of test (507s).... 81 Figure 4.3.2-5 Velocity dependence of spasticity  83  Figure 4.3.2-6 Self induced clonus  84  Figure 4.3.2-7 Spasms occurring during testing  85  Figure 4.3.3-1 Data input to M a t l a b ®  88  Figure 4.3.3-2 Typical equation curve fitted to resistive torque data from a subject without spasticity (407s)  89  Figure 4.3.3-3 Typical equation curve fitted to resistive torque data from a subject with spasticity (607s)  89  Figure 4.3.3-4 Response parameter versus damping parameter for all velocities tested 93 Figure 4.3.4-1 Response parameter versus damping parameter for all velocities tested separated by delineating curve  95  -Vlll-  List of Figures  ACKNOWLEDGMENTS  There have been many people involved in the development of the device to quantitatively measure spasticity at the ankle and I would like to take this opportunity to thank those people and organizations that contributed to the success of this project.  First and foremost I would  like to thank the Natural Sciences and Engineering Research Council of Canada who provided funding for the project making the research possible.  Secondly I would like to  thank my supervisor, Dr. Doug Romilly, who provided financial assistance and the necessary mechanical engineering expertise to make this research a success, and who proved to be an excellent proof reader.  Thank you also to Dr. Cecil Hershler who provided the necessary  medical expertise and to Dr. Ray Gosine for his efforts and guidance.  O f course, none of the  research would have been possible without the test subjects or the testing facilities in the C I C S R building. I would also like to thank my fellow lab members who were always ready to lend a hand and give advice when called upon.  Finally, I would like to thank my wife,  Laurie, for her patience and help.  -IX-  Chapter 1: Introduction  CHAPTER 1: INTRODUCTION  Spasticity is a debilitating condition which limits the abilities and daily activities of millions of people, young and old. Individuals with spasticity are restricted in their movement by the uncontrolled reflex actions of their own muscles.  Essentially someone with spasticity has  their own muscles working against them as they try to move their limbs. Spasticity is often associated with head and spinal cord injuries, stroke, multiple sclerosis, and cerebral palsy. Individuals with the aforementioned conditions are often very debilitated and, what should be noted is that the impairment associated with these conditions is often due to spasticity. Numerous treatments for spasticity do exist, ranging from exercise to drugs and surgery, but they are all limited to clinical trials and conjecture.  None of the treatments are universally  successful nor is there a known cure and, as a result, effective treatments for spasticity are needed to alleviate this condition. In order to determine whether the treatments and therapies are successful, one must be able to monitor day-to-day changes and this requires the ability to accurately and reliably measure the progress of the condition.  The mechanisms causing  spasticity are not fully understood and as a result, there is no general agreement on the most suitable way to measure spasticity.  Generally, the evaluation of spasticity is based on  qualitative or semi-qualitative clinical observations which are of limited usefulness. Spasticity is currently measured clinically by subjective,  manual methods  which are unsuited to  quantifying incremental day-to-day changes in severity required to evaluate new treatments. The most common clinical method of assessing spasticity involves manually manipulating the  1  Chapter 1: Introduction  joint and subjectively assessing the degree of resistance to this passive stretch based on an ordinal scale of 0 (no spasticity) to 4 (severe spasticity).  This generally accepted method of  evaluating spasticity is entirely unsuitable as it is both subjective and uses much too gross a scale. In order to effectively study spasticity, it is essential to have an objective, quantitative method of measuring spasticity. A t this point it would be useful to review the characteristics of spasticity.  1.1  Definition of Spasticity  Spasticity can be defined as a velocity and position dependent reflex resistance to passive stretching of the involved muscles.  One of the more commonly accepted definitions of  spasticity from the literature was put forward by Lance [1], who described spasticity as "a motor disorder characterized by velocity-dependent increases in tonic stretch reflexes ('muscle tone') with exaggerated tendon jerks resulting from hyper-excitability of the stretch reflex as one component of the upper motor neuron syndrome".  Motion of our limbs is accomplished when electric signals from the brain reach the agonist muscles via motor neurons. In normal circumstances, the agonist muscles contract (see Figure 1.1-1) causing movement while the antagonist muscles are inhibited and provide no resistance to the movement.  On the other hand, a person with spasticity will also have impulses sent to  the antagonist muscles, making them active, resulting in increased muscle tone and resistance to voluntary movement and passive stretch.  2  Chapter 1: Introduction  Without Spasticity  With Spasticity  Relax  Uncontrolled reciprocal contraction  Figure 1.1-1 Schematic representation of the effects of spasticity  When a healthy person moves their arm, as shown in Figure 1.1, their agonist muscle (in this case the biceps) contracts and at the same time their antagonist muscle (the triceps) will relax allowing smooth and uninhibited movement.  O n the other hand, if someone with spasticity  were to try to do the same thing, the biceps muscle will contract to try and initiate movement but the triceps muscle might also contract, rather than staying relaxed, thus inhibiting the arm's movement.  This symptom also occurs when the arm is passively moved (i.e. the  individual is trying to relax) by someone else.  In cases where an individual suffers from  severe spasticity, their muscle contractions can be so uncontrollable that they can be completely debilitated and unable to move themselves.  Other characteristics which are  occasionally observed in conjunction with spasticity are clonus, which is a series of repetitive muscle contractions elicited by a rapidly applied, but maintained stretch, and the Clasp Knife  3  Chapter 1: Introduction  phenomenon, which is a sudden relaxation of the involved muscle following a strong reflex resistance to a maintained stretch [2, 3].  1.2  Measurement of Spasticity  Measurement of spasticity has been a troublesome issue for many years. Because so little is known about the causes and mechanisms of spasticity, there is no general agreement as to the most appropriate way to measure spasticity.  However, no-one disagrees that some means of  quantifying spasticity in an accepted and dependable manner is necessary to determine suitable treatments and therapies for the disease.  The most common forms of spasticity measurement in use today are based on qualitative or semi-qualitative clinical observation. One of the more commonly employed tests to evaluate spasticity is the Modified Ashworth test which involves manually manipulating the joint and qualitatively assessing the degree of passive resistance based on an ordinal scale ranging between low and severe. Unfortunately, these recognized methods for evaluating spasticity are unsuited to quantifying incremental day-to-day changes in severity which would be required to evaluate new treatments and therapeutic intervention. In order to study the effectiveness of therapeutic intervention for spasticity, it is essential to have an objective, quantitative method of measuring spasticity.  Devices developed with the intent of quantifying spasticity do exist, but none of them have been entirely successful in providing an acceptable measurement of spasticity. Some of the  4  Chapter 1: Introduction  tests using these devices are subjective and do not provide therapists with the ability to distinguish and record small changes in a patient's condition. In many cases devices developed to measure spasticity have relied upon manual manipulations which limits the objectivity and repeatability of the test. Several motor driven, computer-controlled systems to measure spasticity exist, but they are limited either by design or application such that they have not been accepted as a suitable protocol for quantifying spasticity.  The ankle is particularly troublesome to test for spasticity due to its geometry.  Determining  resistance is more difficult while testing at the ankle because its range of movement ( R O M ) is typically less than half of that of the elbow. Also, since the lever arm available to the tester is shorter at the ankle than the elbow, subtle differences in encountered resistance may be more difficult to detect [4]. However, because the ankle plays an important role in gait [5, 6], posture [7], and activities of daily living, it is an important joint to evaluate for spasticity even though it may be more difficult to test clinically. For these very reasons the ankle joint was chosen  as the joint of interest for this research project.  Since testing  will be  accomplished using a computer-controlled device, some or all of the difficulties encountered by manual manipulation of the joint should be eliminated.  1.3  Research Objectives  The ultimate goal of this project is to provide the ability to suitably measure the degree of spasticity of an individual, in a quantifiable manner, which would allow the results of therapeutic intervention and treatment to be evaluated.  This, in turn, would result in the  5  Chapter 1: Introduction  development of better treatments for spasticity and potentially a better understanding of the nature of spasticity.  More immediate objectives were set for this project, which were to be  achieved at different stages throughout the course of the research. Objectives to be met in the design phase of the project are outlined below.  •  The short term objective was to develop and validate a computer-controlled device to quantitatively measure the degree of spasticity at the ankle in a clinical application.  •  The device had to perform the testing in a safe manner and required redundant safety features to protect the test subjects.  •  This device had to be flexible enough to accommodate testing based on various measurement protocols (e.g. load controlled rotation, displacement/velocity controlled rotation etc.) so that a method chosen as most suitable for measuring spasticity could be accommodated.  •  The device had to be portable so that it could be taken to the patients to be tested in the event that they were bed bound or unable to travel to a clinic.  •  The device had to be able to test subjects in different positions such as standing, sitting, and prone.  •  The device had to have the ability to test subjects while simulating the effects of the subject's weight on the joint being tested.  In this manner, the effect of the muscles  balancing response on spasticity could be investigated. •  The device had to be flexible enough to be able to test different limbs so that it could be used to test knees and elbows as well as the ankle.  6  Chapter 1: Introduction  Throughout the testing phase of the research a number of milestones were to be achieved to establish the capabilities and effectiveness of the testing system.  The following were  required or desired:  •  The device had to reliably measure the resistive torque at the ankle.  •  The device had to distinguish between joints with and without spasticity.  •  The device had to be able to distinguish different levels of spasticity.  •  The device should be able to observe and record clonus and other phenomena associated with spasticity.  •  These measurements should be repeatable on a trial-to-trial and day-to-day basis within a statistically acceptable envelope.  •  B y evaluating the data collected using the device, be able to establish a means of quantifying spasticity and be able to effectively  use this technique to differentiate  spasticity severity.  Ultimately the testing phase of the project lead us to the current long term objective which is to use this device to determine a reliable method for the evaluation and measurement of spasticity to aid in the diagnosis and treatment of spasticity. The importance of this long term objective is evidenced by the lack of understanding of the mechanisms of spasticity and the inability of current measurement techniques to provide a suitable measurement which would significantly aid in the diagnosis and treatment of this debilitating condition.  7  Chapter 1: Introduction  We propose that this device will be able to diagnose, assess, and help rehabilitate people who are suffering from spasticity.  This device will aid the health care provider in performing  these tasks by doing much of the work previously done by the care provider and then by subsequently acting as a home exercise device to help rehabilitate the patient.  This will  reduce the cost associated with diagnosing and evaluating spasticity while at the same time providing a more accurate and quantifiable evaluation of the condition. Similarly the cost of rehabilitating the patient can be significantly reduced by allowing the patient to self rehabilitate at home or in the clinic thereby reducing the workload of physical therapists and other health care professionals.  The end result of these objectives is the ability to suitably  measure the results of therapeutic intervention and treatment, and, through the better understanding of the mechanisms of spasticity, to develop superior treatments for this condition.  1.4  Thesis Overview  In the following chapters the entire research project is reviewed and discussed.  Chapter 2  reviews the literature and includes more detailed background information on the current understanding of spasticity and its effects, as well as how spasticity is currently measured clinically. A l s o included in Chapter 2 is a critique of other researcher's attempts to quantify spasticity, including a prototype of the current device, and how their work relates to the current research project.  Chapter 3 covers all aspects of the experimental procedure  including design of the device, safety concerns, control of the device, data acquisition, and testing protocol. Chapter 4 discusses the data obtained using the device and includes an in  8  Chapter 1: Introduction  depth analysis of the results as well as a thorough discussion of the significance of the data and results.  Chapter 4 also includes a suggested means to quantify spasticity based on the  collected data. Chapter 5 evaluates the research project with respect to the original objectives and suggests future work which would contribute to the work undertaken for this project.  9  Chapter 2: Literature R e v i e w  CHAPTER 2: LITERATURE REVIEW  2.1  The  Overview  information in this chapter expands on the motivation for the project and reviews  information vital to developments discussed in the following chapters. This review includes, but is not limited to information relevant to the understanding of spasticity, current clinical measurement of spasticity, and attempts to quantify spasticity.  Not all measurement systems  reviewed were designed to measure spasticity at the ankle, but because of the limited amount of research reported in this area, it was found useful to review the literature where measurement of spasticity or joint stiffness in general was the focus.  This literature review covers a number of important areas regarding spasticity and its measurement.  Firstly, the current understanding of spasticity and how it affects people who  suffer from it is discussed to help explain why this project was undertaken and why there is so much difficulty associated with spasticity measurement.  In order to understand spasticity  measurement, one must first understand the physical aspects of spasticity such as stiffness and reflex response.  From this understanding, a model of the spasticity phenomenon can be  determined. Clinical measurement of spasticity is currently performed and these techniques are discussed in some detail. The shortcomings of clinical measurements of spasticity led to early  10  Chapter 2: Literature Review  attempts to quantify spasticity, which were largely unsuccessful, and to more recent computercontrolled measurement techniques.  The current literature review highlights earlier problems  with spasticity measurement which can hopefully be avoided and reveals some of the more useful measurement techniques. These techniques were used by the Rehabilitation Engineering and Clinical Technology ( R E A C T ) research group to develop a prototype device to measure spasticity, which is also discussed.  2.2  Current understanding of spasticity  There are many schools of thought as to the best way to measure spasticity and much disagreement exists over the suitability of various measurement techniques [8]. This follows from the lack of understanding of the nature of spasticity.  Panizza et al [9]recognizes this  situation and states; "Currently, physicians usually have very little difficulty in the diagnosis of spasticity in most of their patients, but the problem arises when quantitative considerations must be added, probably because spasticity is not a simple entity but a syndrome originating from a variety of disorders confirmed by Levin  [10]  The literature does not adequately address these issues as is who writes; "As yet there is  no literature addressing the  reproducibility of the existing barrage of clinical evaluations of spasticity  and reflex /  measurement. Also not clear is whether or not a systematic relationship might exist between these multiple indices of spasticity." A s a result, the exact pathophysiological mechanisms underlying spasticity still remain obscure [11].  11  Chapter 2: Literature R e v i e w  2.2.1  Stretch reflex  A stretch reflex is a monosynaptic reflex evoked by a sudden increase in muscle length, resulting in a contraction of the stretched muscle. The reflex is controlled by stretch receptors called muscle spindle organs, located in the muscle. The muscle spindles respond to both the velocity of lengthening (dynamic stretch, or angular velocity), and to the actual length of the muscle (static stretch, or angular position) [12].  The response of the muscle spindles to  dynamic and static stretch means that the stretch reflex consists of two components, the phasic and tonic stretch reflex. The phasic component of the stretch reflex responds to rapid stretching of the muscle, whereas the tonic component of the stretch reflex is the response to a slower stretch of the muscle [11]. The tonic stretch reflex is also modulated by the size of stretch and the length of the muscle at which the stretch occurs [13, 14, 15].  In the presence of spasticity, the sensitivity of the stretch reflex is exaggerated and the subject is unable to control the reflex which responds to the stretching of muscle, whether appropriate or not [11]. There are two measurable parameters which can be altered in the stretch reflex which could account for the reflex mediated increase in resistance associated with spasticity [16]. The reflex threshold is the angular threshold at which the stretch reflex occurs. This threshold is manifested clinically as the 'catch point' at which the resistance to a manual stretch abruptly increases.  If this reflex threshold was reduced, a smaller and/or slower motion would be  sufficient to reach the reflex threshold at which point the reflex torque or force of the muscle increases in proportion to the increasing muscle length.  Another possible disturbance of the  stretch reflex is the reflex gain, which is characterized by an abnormal increase in reflex force  12  Chapter 2: Literature Review  with increasing rotation of the joint without significant change in the reflex threshold angle. In quantitative terms, the angular stiffness, which is a measure of stretch reflex gain, is increased above normal at the point where the reflex response occurs. It has been found that the stretch reflex activity varies with ankle position [12].  2.2.2  M u s c l e stiffness  "Stiffness" is broadly defined as the incremental force evoked by a unit displacement.  In  terms of spasticity measurement, it is often considered torque over angular displacement, obtained by simply dividing the incremental change in force or moment by the corresponding displacement as if the curve was linear. The spring-like properties of muscles are believed to play an important role in maintaining human vertical posture, both during locomotion, and in control of muscular activity.  In order to describe and study these properties, researchers in  the field of biomechanics frequently use the well established physical notion of stiffness described above.  The applicability of this term for describing such complex objects as  muscles, tendons, and joints is not obvious although measurement of mechanical properties (stiffness, viscosity, impedance etc.) of passive joints, albeit not easy, does not meet with conceptual difficulties [17]. A basic understanding and definitions of the terms that are being measured, as well as an understanding of the limitations of the definitions, are required to ensure that meaningful results, which can be compared with other research, are obtained.  Stiffness, defined as the total mechanical resistance to an externally imposed change in joint angle, is the result of the combined contributions of passive tissues and active contractile  13  Chapter 2: Literature R e v i e w  properties of the involved muscles and tendons, so the presence of increased stiffness cannot be automatically contributed to an enhanced stretch reflex [18, 19, 20].  One has to consider  the model of the muscles and reflex mechanism to help understand what occurs when a joint rotation takes place.  When the length of a passive muscle exceeds the resting length,  increased resistance is provided by the connective tissue known as the parallel elastic components (PEC) according to the well known Hill model [21].  B y definition, P E C are  responsible for muscle stiffness when contractile components do not generate force.  The  stiffness of the whole activated muscle is determined by its P E C as well as the series elastic components (SEC).  A common three element muscle model is shown in Figure 2.2.2-1  (including the contractile components (CC)).  A viscous element is also assumed in the  model.  Figure 2.2.2-1 Three element muscle model [21]  When a joint is rotated to a given angle at varying angular velocities, the slope of the curve relating muscle force to angle of joint displacement (muscle length), commonly referred to as the stiffness, is contributed to by both the intrinsic stiffness of the muscles as well as the reflex response. This response is similar to a simple spring which generates a restoring force that is  14  Chapter 2: Literature Review  proportional to its change in length.  It has been considered that an increase in the intrinsic  mechanical stiffness of the muscle is responsible for the increased resistance noted in spasticity. However this hypothesis, involving a change in intrinsic muscle properties, does not easily account for many established findings such as enhanced phasic muscle stretch reflexes which indicate that motorneuron excitability is increased [16]. This type of response would have to be caused by a latent reflex loop, which is taken into consideration in the following models.  Kearney described ankle mechanics in terms of a model having a linear passive pathway in parallel with a non-linear, velocity dependent reflex pathway as shown below [22].  POSITION  PASSIVE MECHANICS  PASSIVE TORQUE  ANKLE TORQUE  DELAY VELOCITY  REFLEX TORQUE  Figure 2.2.2-2 Passive and reflex stiffness mechanisms [22]  In this case the phasic stretch reflex response, dependent on velocity, is delayed, roughly 40 milliseconds, behind the intrinsic stiffness of the muscle-tendon complex.  15  Chapter 2: Literature R e v i e w  The figure below shows another model of the stiffness properties of muscles [20]. model incorporates the linear visco-elastic  This  properties of the muscle and tendon and includes  a latent reflex loop. The active components of this model, i.e., the reflex loop, influence the behavior of the model through five parameters; gain, latency, phase shift, natural frequency, and damping ratio. The active component is mathematically represented by a second order, low pass system function.  It is this contribution of the active component which is  exaggerated in spasticity [20]  Spindle  Tendon elasticity  Muscle elasticity  /  Muscle viscosity  V  Muscle friction  / / /  Reflex loop  /  Contractile mechanism  A  i _  Figure 2.2.2-3 Model basic to visco-elastic properties of muscle and tendon [20]  "Dynamic stiffness"; a term adopted by Kirsch et al [23] is used to describe the overall relationship between the dynamic, nonlinear force and an imposed displacement.  This term  was adopted because an external displacement imposed on a muscle or limb elicits a force or moment that generally has both static (intrinsic muscle stiffness) and dynamic (reflex response stiffness) components which results in a nonlinear response.  The term was  introduced in an attempt to clear up the confusion created by the casual use of "joint  16  Chapter 2: Literature Review  stiffness". The nonlinear nature of the neuromuscular system results in estimates of dynamic stiffness that are heavily dependent upon the definition used and the type of experimental data obtained [23].  The functional significance of different measures of muscle stiffness can  be usefully evaluated by recognizing the limits of each type of measure and the mechanisms giving rise to the observed behavior.  There are a number of proposed models to describe the stiffness of a human joint, whether suffering from spasticity or not. Each of the models attempts to accurately model what is an impossibly complicated system full of nonlinearities. The model developed by Kearney [22] is clearly expressed in Figure 2.2.2-2 as a function of the input position.  In this case the  output torque is a function of both the input position and the input velocity subject to a delay. This model fits well with the commonly accepted definition of spasticity.  From the  perspective of this project, the most relevant stiffness model is the Kearney model. Adopting this model for this project would require some means to mathematically express this nonlinear system.  The non-linearity of the model arises from the delayed velocity contribution  which was found to be lagging approximately 40 milliseconds behind the initial position input [22, 23]. This short delay is significant in the research done by Kearney as the testing perturbations were less than 40 milliseconds, and data gathering was only half a second long at 200 H z . However, the testing proposed for the current project is of much longer duration so the 40 ms delay may be ignored. This allows the model to be approximated with a second order system. The mathematical equation for this approximation will be a second order linear differential equation of the form,  17  Chapter 2: Literature R e v i e w  dT  de  dt  dt  2  2  2  where 0 is the input angle or position, T is the output torque, and t is time.  In this case, the resistive torque will depend upon four parameters related to the joint. The gain parameter, K, will be dependent on the intrinsic stiffness of the joint.  The response  parameter, oo , will be related to the rapidness of the output torque curve matching the input n  position and the damping parameter,  will be related to the viscous elements within the  joint. The velocity component, V, will be related to reflex response due to the speed of the test and is indicative of the velocity dependence of spasticity.  The fifth parameter, A, is the  acceleration gain, and is assumed to be zero.  2.2.3  Effects of spasticity  Spasticity represents one of the most crucial impairments for individuals with central nervous system disease [16] and it affects over six million people each year [24].  The main concern  of people with spasticity is usually their loss of strength and dexterity, plus increased muscle stiffness which obstructs movement.  The weakness brought on by spasticity is due to a loss  of voluntary muscle strength or a depression of motor function.  This degree of weakness  may differ for different muscle groups and for different diseases associated with spasticity. The loss of dexterity  associated  with spasticity  [25]  is most  significant  during  fine  movements and results in an inability to make independent movements as well as a slowing  18  Chapter 2: Literature Review  of the rate of voluntary muscle contraction [11].  This lack of coordination and muscle  weakness ultimately reduces the subject's quality of life.  Spasticity results in impairment of postural control, mobility and function [26].  Spasticity  interferes with voluntary movements causing them to be performed clumsily with the limb adopting abnormal or awkward posture. [27].  Involuntary, often painful spasms may also occur  The level of spasticity is known to be affected by a number of factors including  anxiety, depression, fatigue, ambient temperature, the use of drugs, body position, as well as by the comfort of the subject [28].  Spasticity disrupts activities of daily living for those  affected and limits the efficacy of physical therapy by resisting therapeutic movement [29, 30].  The reduction of spastic hypertonia is mandatory to improve the individual's level of  function [31].  Rehabilitation for individuals suffering from spasticity is very difficult  without a reduction in the severity of the spasticity.  2.3  Clinical measurement of spasticity  Although caregivers have little difficulty in diagnosing spasticity due to its well established characterization, its measurement by a reliable, well accepted means has challenged both clinicians and researchers, and quantification remains elusive.  One of the most obvious and  consistent characteristics of spasticity is an increased resistance to passive stretch.  As a  result, clinicians often evaluate the severity of spasticity by applying a manual passive stretch to a muscle group and observing the encountered resistance.  In the past, spasticity was  popularly assessed using an ordinal scale of M i l d , Moderate, or Severe.  19  Chapter 2: Literature Review  The most common method for clinically assessing spasticity in use today, is the Ashworth Scale or the Modified Ashworth Scale  [32,  33].  Almost all studies  monitoring the  effectiveness of therapeutic or drug treatment for spasticity monitor their progress using this scale [32, 33, 34], sometimes in conjunction with electromyography ( E M G ) which measures the activity of a muscle. The Ashworth scale, named after its creator in 1964 [35], uses a five point ordinal scale for grading the resistance encountered while passively stretching the muscle (Table 2.3-1). The scale is a nonlinear method of qualitatively assessing the severity of a subject's spasticity, and because of this, results are usually clustered in the middle of the scale.  Grade  Description  0  N o increase in muscle tone.  1  Slight increase in muscle tone, giving a "catch" when the affected part(s) is moved in flexion or extension  2  More marked increase in muscle tone but affected part(s) easily flexed.  3  Considerable increase in muscle tone: Passive movement difficult.  4  Affected part(s) rigid in flexion or extension.  Table 2.3-1 Ashworth scale for grading spasticity [35]  In  1987  Bohannon and Smith presented a modified version of the Ashworth scale  appropriately called the Modified Ashworth Scale ( M A S ) [36]. This version of the Ashworth Scale had an additional grading (1+) and slightly altered definitions (see Table 2.3-2). Their study supported the reliability between testers of a manual test of elbow flexor muscle  20  Chapter 2: Literature R e v i e w  spasticity using the M A S . Although this finding contrasts with the idea that subjective methods for assessing spasticity are unreliable, the results of such testing are far too gross to detect incremental changes in the disease, nor are they suitable for comparison with other clinician's results.  Indeed, Bohannon and Smith write: "We believe that the reliability we  obtained can be attributed, in part, to our experience and extensive mutual testing and discussion. Without such collaboration, different results might have been obtained."[36]  Grade  Description  0  N o increase in muscle tone.  1  Slight increase in muscle tone, manifested by a catch and release or by minimal resistance at the end of the range of motion when the affected part(s) is moved in flexion or extension.  1+  Slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less than half) of the R O M .  2  More marked increase in muscle tone through most of the R O M , but affected part(s) easily moved.  3  Considerable increase in muscle tone, passive movement difficult.  4  Affected part(s) rigid in flexion or extension.  Table 2.3-2 Modified Ashworth scale for grading spasticity [36]  Sloan et al performed an independent study of the M A S and found that it provides a satisfactory clinical measure of spasticity in the upper limb [37].  The results were not as  good for lower limb spasticity and thus Sloan et al concluded that the M A S does appear useful for testing spasticity of the upper limbs but questioned its validity for testing lower limb spasticity.  21  Chapter 2: Literature Review  A further study by Allison et al testing spasticity at the ankle plantarflexors (as they were cited by Bohannon and Smith as one muscle group which may be more difficult to assess lent some qualified support to the continued use of the M A S ) [4, 33]. However they felt that the reliability of the test for spastic plantarflexors may be less than optimal due to mixed results for intrarater reliability and poor interrater reliability. They concluded: "Although marginal reliability has been demonstrated in this study, a larger question which has not been addressed is whether a qualitative ordinal scale is an acceptable measure, regardless of its reliability." [33].  There is a certain amount of discomfort associated with the use of an ordinal scale to assess spasticity.  Terminology used in the M A S table contribute to poor interrater reliability.  Adjectives such as 'slight', 'minimal', 'considerable', and 'difficult' are ambiguous and invite varied interpretations. Even deliberate attempts to address these ambiguities by testers failed to alleviate tester's discomfort with the level of subjectivity inherent in the scale [33]. It has been found that manual scales, such as the M A S , suffer from a clustering effect with most patients in the middle grades [16]. However, the modified Ashworth scale remains the main method of evaluation of spasticity in routine practice.  2.4  Quantification of spasticity  The importance of quantifying spasticity has never been greater than it is today.  Numerous  treatments, therapies and drugs are undergoing testing to determine their suitability to alleviate spasticity.  These  treatments  require reliable, quantitative  means  to  assess  day-to-day  22  Chapter 2: Literature R e v i e w  incremental improvements or increases in the severity of spasticity. A t the same time there are increasing demands on therapists to document clinical treatment outcomes for reimbursement by third party payers such as insurance companies and government health providers [4, 38]. This required treatment outcome documentation depends on measures with demonstrated reliability [4] such as a means to quantitatively measure spasticity.  The literature offers a  variety of alternatives for measuring spasticity but no single method seems to be widely used [39,40].  This has been confirmed by a recent survey [38] which indicates that health care  professionals did not measure spasticity although it was regarded as an important issue.  In a review of the available literature, the device controlled quantitative methods for the measurement of spasticity can be divided into two groups; 1) those methods of measurement which have some non-automated component, which could introduce variation between measurements, and 2) those which were entirely automated and therefore more reproducible. Those in the first category are generally superior to the qualitative and semi-qualitative methods currently used to clinically evaluate spasticity, but they still introduce unnecessary variability into the measurement.  While those in the second category provide a higher level of  repeatability, unfortunately none have been entirely successful in providing an accepted measurement of spasticity, nor do they meet the criterion for this research project. The various quantitative measurements categories.  of spasticity are divided into several  different  Non-automated methods of measurement such as dynamometers and goniometers  are discussed in Section 2.4.1, while fully automated methods of quantifying spasticity are discussed in Section 2.4.2.  23  Chapter 2: Literature R e v i e w  2.4.1  Device assisted methods of measurement  Perhaps the most basic means of 'quantifying' spasticity is the use of electromyography ( E M G ) to record the relative activation of the involved muscles which is then correlated to the degree of spasticity.  A number of researchers [39, 41, 42, 43, 44] have used E M G  analysis as a means to objectively quantify spasticity with some measure of success. However,  the repeatability of E M G  is generally poor due to the use of surface/skin  electrodes which can never be applied with precision to the same location [38].  Another  shortcoming of E M G lies in its inability to distinguish between voluntary muscle activity and spontaneous, involuntary muscle activity due to spasticity [39].  Other limitations of E M G  measurement to determine muscle activity around a joint include the inability to include all of the involved muscles around complex joints such as the ankle, and the fact that muscle activity alone does not constitute a measure of the degree of spasticity. E M G does contribute to the understanding of the muscle behavior associated with spasticity and, correlated with other measures, can be a powerful tool, but on its own it simply has too many limitations.  Another method of quantifying spasticity, which has been in use for many years is the pendulum test [45, 46]. The leg is dropped from full extension and allowed to swing freely with the patient lying in a supine position. The swings are recorded, occasionally with E M G measurements, and the position vs. time data is used to determine the degree of spasticity. The recorded knee movement is usually a sinusoidal pattern of angular motion which can be modeled mathematically to differentiate between a limb with spasticity and one without. This mathematical model questionably assumes that the mechanical properties of the knee  24  Chapter 2: Literature R e v i e w  extensor and flexor muscles are equal and that the model can be treated as a simple linear second order system. However, muscle stiffness and viscosity vary with the degree of muscle excitation and muscle length. [16]. Despite these flaws Katz found the pendulum test to be a practical and reproducible measure of spasticity  [40].  Other research also found that  consecutive trials of the pendulum have quite good reliability's (r=0.96) [47].  However,  some concern over the transferability of the pendulum test has been expressed.  Undefined  definitions needed to perform the pendulum test have led to incorrect interpretation of results and lack of repeatability over time [48].  Another shortcoming is that this test is only used to  test the quadriceps muscle and is unsuited for measuring other muscle groups [38].  Hand held dynamometers have often been used to measure spasticity [49,50,51].  Typically  they are used to measure the resistance of a voluntary muscle contraction (recording the maximum value) and are therefore more suited to measuring strength or weakness.  In one  case a hand held dynamometer was used to push the subject's passive limb about its joint at approximate speeds, while the device recorded the maximum resistive torque [50].  The use  of hand held dynamometers provides only approximate angular velocity and only a single measure  of the  maximum resistive  torque and therefore  obviously  cannot  meet  the  requirements for objectivity demanded by this research project.  Another technique makes use of the isokinetic dynamometer to restrict joint motion to a constant velocity.  Some commercially available units such as the K I N C O M Dynamometer  [32, 50, 52, 53, 54] and the Cybex II [42, 55, 56, 57, 58] have been used in attempts to  25  Chapter 2: Literature R e v i e w  measure spasticity.  However, dynamometers are used to restrict velocity rather than  controlling it and therefore are not as consistent as a computer-controlled motor driven device.  In the event that the velocity is too low, the dynamometer will not increase the  velocity, nor will it maintain a constant velocity with 100% accuracy. The K I N C O M [54] is typically used for strength measurements  and has a passive  mode which allows  the  measurement of spasticity. However, a severe limitation is that it is not portable. The work done by Ensberg [32] correlated the slope (work done) results of a computer-controlled K I N C O M with a clinical assessment using the Ashworth scale with little success (r = 0.28). Other researchers used only the end values of the torque curves [50], ignoring most of the data, or manually rotated the joint, relying on the dynamometer to restrict movement [52] resulting in velocities of unknown accuracy. The Cybex II requires the subject to lie on their back on a table with the subject's knee at the edge of the table and the lower portion of the leg in the device. Movement of the knee joint is then used to elicit spasticity. This device is often used in conjunction with the pendulum test [47, 55]. In other research using the Cybex II, the subject was required to perform a voluntary movement which was restricted by the dynamometer [59]. In this research, the voluntary movement cannot be considered objective, or repeatable.  After a review of the device assisted methods of measurement it is obvious that all of these available techniques for quantifying spasticity cannot meet the objectivity requirements demanded by this project because none are fully governed by the devices used. In addition several of the techniques only provide one measurable point of data from which spasticity is  26  Chapter 2: Literature R e v i e w  quantified which results in the loss of potentially important data.  Finally, some off the  devices require a voluntary contraction which is sometimes not possible and cannot be considered entirely objective.  2.4.2  Motor controlled measurement  In order to have a completely objective and entirely reproducible test for the measurement of spasticity, controlled displacement must be applied to the limb.  One of the easiest and most  effective methods to provide controlled passive manipulation of the ankle is to use a motor. Several motorized devices to measure spasticity have been developed and are discussed below.  There are two main methods used for testing for spasticity using a computer-controlled motorized device. The first method rotates the joint through a sinusoidal velocity profile while recording the response. The second more common method (and subsequently adopted for this project) rotates the joint through a fixed rotation at a constant velocity while recording the response. This latter method is known as the ramp and hold method, referring to the velocity profile generated by the joint rotation.  This method closely duplicates the motion used in  common clinical testing discussed in Section 2.3.  Both of these methods have been  implemented with varying success and are reviewed, along with some less common techniques, within this section.  Several researchers have attempted to measure the severity of spasticity using a computercontrolled, servo-motor driven device to impose a sinusoidal oscillating movement to the joint  27  Chapter 2: Literature R e v i e w  at different frequencies, which is met by a corresponding cyclically changing force from the joint [19, 29, 59, 60].  The reasoning behind adopting this method of measuring spasticity is  that sinusoidal oscillations produce more readily repeatable and consistent stimuli than the ramp method.  However, in order to effectively isolate the torque due to the reflex response, the  inertia of the limb, inertia and drag of the measurement system, and the contribution of the passive properties of the tissues have to be considered. While a concern, these contributions can be roughly approximated and removed from the final results thus providing a measured spasticity response of reasonable accuracy.  One device, using sinusoidal movement, was used to quantify spasticity based on frequency dependent changes in viscous and elastic stiffness [19].  Torque values representing ankle  resistance as a function of ankle displacement were reduced to two components; 1) the in phase resistance due to elastic stiffness and 2) the 9 0 ° out of phase resistance due to viscosity. These two components of the resistive torque were determined by using a Fourier analysis to decompose the combined torque response into their sinusoidal components. The vector sum of these components was considered to be the total ankle stiffness and the final path length of the total stiffness values was used to represent the overall degree of ankle spasticity.  This path  length was determined by plotting the total stiffness vectors for all frequencies tested, and then adding together the distance between each consecutive vector apex.  Longer path lengths  resulted from frequency dependent variations in the ankle stiffness which were attributed to the velocity dependence of spasticity and were considered to be related to the degree of spasticity. Test-retest reliability was shown to be good for subjects with spasticity at high frequencies (11  28  Chapter 2: Literature R e v i e w  Hz). However lower frequencies, especially below 7 H z , showed either lower stiffness due to viscosity for the subjects with spasticity, or inconclusive results. A t higher frequencies (11 Hz) it was concluded that spasticity could be quantified, but some of the earlier conclusions at lower frequencies lend a measure of doubt. A drug evaluation study [29] which employed the device produced results which showed that, for the same subject, day-to-day variations in the degree of quantified spasticity ranged from as little as 0% to as high as 56% for the 9 subjects, with an average day-to-day variation of 22%. Variations of this magnitude cannot be representative of a reliable and repeatable method for the measurement of spasticity.  Other studies, using similar techniques, have been undertaken, but the objective of the research was to simply investigate the properties [60] or the stretch reflex [59] of ankle joints with and without spasticity rather than determine a means to quantitatively measure the degree of spasticity.  The results of Rack et al [59] were somewhat inconclusive as they concluded;  "Spastic subjects showed relatively stereotyped responses, with evidence of a vigorous spinal stretch reflex. The responses of limbs without spasticity were variable; there was little reflex response to the first cycles, but as the movement continued the reflex responses increased and often came to resemble the responses of spastic limbs."  Patterns of stretch reflex activity  provoked by sinusoidal oscillations of the ankle joint were studied by Rebersek et al [60]. Their device consisted of an electrohydraulic position controlled servo-system.  The intent of their  research was not to develop a clinical tool for the evaluation of spasticity, but rather to determine the muscle length dependence of a spastic reflex response.  They found that in the  case of carefully controlled experimental conditions, an acceptable repeatability of results can  29  Chapter 2: Literature Review  be achieved using the sinusoidal oscillation technique. They concluded that the resistance to passive movement was highly dependent on the muscle length at which it was tested. This is commonly acknowledged to be the case. In either study, no attempt was made to quantify the results.  Problems associated with using a sinusoidal movement are numerous. It is not clear whether such an unnatural movement could be considered as an effective means of assessing spasticity, nor can it be directly compared to current clinical methods of testing such as the modified Ashworth scale. Using a sinusoidal movement also necessitates the use of servo-motors rather than stepper motors which could also result in some discrepancies in the repeatability of the movement, as servo-motors use feedback controlled positioning. Similarly, sustained repeated movements for a period of time, over a number of test frequencies, could result in fatigue of the subject which could cause unforseeable effects on the degree of spasticity.  The repeated  movement could also result in training effects over time.  Inertia is another problem associated with using sinusoidal oscillations of a joint to measure spasticity.  The forces generated by inertia are proportional to the acceleration of the limb.  Therefore, sinusoidal motion forces are related to the square of the frequency of the oscillations so for large oscillations, the motion must be restricted to quite slow movements, and as a result, the effects of rapid stretching cannot be discerned. On the other hand, for rapid movement, the oscillations must be quite small, and the motion restricted to a few degrees, providing limited information [61].  In addition, research has suggested that the reflex response is strongly  30  Chapter 2: Literature Review  nonlinear and that on-going movements inhibit the reflex action in proportion to their average velocity [22, 62, 63] thus constant oscillations may actually inhibit the reflex response which is being measured.  In contrast, the ramp and hold technique closely duplicates common clinical testing.  Several  groups of researchers have made use of this technique by implementing a computer-controlled motor driven device to quantitatively measure stiffness about a joint. Some have simply been used on healthy subjects to measure passive stiffness properties [64, 65] while others have been used to evaluate spasticity [16, 18, 19, 40, 66, 67, 68].  The work done by Sinkjaer's group  [19,66] used a unique approach in which the subject's ankle was subjected to a perturbation (or small movement) of between one and seven degrees for periods of 450 ms followed by a 450 ms release period, then repeated. This is similar in practice to the sinusoidal motion discussed earlier because it subjects the joint to oscillations at a frequency of approximately 67 H z , but in principal is quite different. In fact the perturbations are essentially a ramp and hold technique since the velocity of the joint returns to zero after approximately 50 ms and is held at that position for the remaining 400 ms of each cycle. The technique could be accurately described as using ramp and hold oscillations.  However, because a servo-motor was used, there was a  considerable acceleration and deceleration phase such that the velocity profile was not a true ramp and could be best described as 'step-like'.  In addition, the tests were performed to  investigate reflex response during a voluntary contraction (i.e. the subjects were asked to match a torque level preset on an oscilloscope and were asked not to attempt to adjust the torque  31  Chapter 2: Literature R e v i e w  during the stretch and release periods) rather than during a passive stretch which more closely conforms to the definition of spasticity.  The research came up with a single stiffness value  representing the degree of spasticity. Some of the results were contradictory. Intrinsic stiffness increased for the subjects with spasticity, but the reflex stiffness was zero for the patients and increased up to 50% for the subjects without spasticity. Although this type of measurement is quite useful for investigating properties of the stretch reflex, the very small and brief perturbations require very accurate measurements which might not be typically used in a clinical setting. Also not all subjects are able to perform a voluntary contraction as many would have no control over the limb being tested. Voluntary contractions also introduce unnecessary variability to the measurements and produce an increased non-reflex resistance and torque. The relationship between the degree of voluntary contraction, increase in reflex response and change in passive properties is not known so results of this testing are subject to even further unknowns.  A group of researchers led by Katz [16, 40] have developed a device most closely related to the device used for this project. The device utilized a computer-controlled servo-motor to rotate the subject's elbow joint through a ramp and hold velocity profile while recording the resulting resistive torque and E M G activity. The device was developed to study stretch reflex dynamics in spastic elbow muscles [67, 68] and used ramp and hold rotations of the forearm in the horizontal plane.  This research tested both passive and voluntary stretch of the involved  muscles and found that, contrary to earlier studies, stretch evoked torque displays a relatively  32  Chapter 2: Literature R e v i e w  weak dependence on stretch velocity. The research concluded that increased tone in subjects with spasticity was likely due to a decrease in reflex threshold rather than a velocity dependent increase in stretch reflex responsiveness.  Further work by the same group used the device to quantitatively measure the degree of spasticity at the elbow [16, 40].  The results from the spasticity measurement device were  correlated with clinical measures of spasticity.  The use of the device to measure reflex  threshold angles at speeds of 307s and 607s significantly correlated with clinical estimates of spasticity using the Ashworth scale.  However, they acknowledged that there were some  unresolved difficulties with the measurement of reflex threshold. Estimating the onset angle of muscle activity from low levels of E M G is technically difficult, and different muscles will show different reflex responses so that identical muscles need to be measured each time, which is in itself difficult. The researchers conceded that occasional E M G tracings were eliminated due to uncertainty. use.  These problems make this type of analysis difficult and undesirable for clinical  In order to avoid these difficulties they chose to use a more practical approach by  measuring the torque at some specified joint angle just before the end of the constant velocity ramp stretch. This was done because stiffness was not considered to be a significant variable thus the torque measured at a predetermined angle should be closely dependent on the reflex threshold.  However, correlation between this method of quantifying spasticity and clinical  testing was shown to be not statistically significant. In conclusion, they suggested that torque measures would be more useful as a means of measuring spasticity.  33  Chapter 2: Literature R e v i e w  Later work done by Given [17] was very similar to this project. Subjects with spasticity were tested at both the ankle and the elbow at speeds between 207s and 607s.  The research was  interested exclusively in 'passive' stiffness of the joints which, by their definition, excluded any results which showed any E M G activity of the muscles.  The research had some success in  quantifying spasticity using the slope of the torque vs. time curve, representing stiffness, at the elbow, but had some difficulty at the ankle because of curvilinear nature of the torque vs. time cures from the ankle.  Unfortunately, ignoring results showing E M G activity precludes the  proper measurement of the reflex response which manifests itself as uncontrolled muscle activity and can be monitored by observing changes in E M G .  The current research project is  interested in reflex response of the muscles and would include these results.  One of the most unusual attempts to objectively measure spasticity, developed by Walsh, is based on the theory that the best way to measure spasticity is to measure the motion of the limb induced by varying the force applied to it [61, 69]. The theory is based on the idea that the limb exhibits a resonance and it is this resonant frequency that reflects the degree of muscle tone or spasticity according to the equation:  where: / i s the resonant frequency K is the muscle stiffness J is the inertia  34  Chapter 2: Literature Review  The device used by Walsh, accomplishes the testing by applying a sinusoidal torque to the passive joint at a continuously changing frequency, while the position and velocity of the joint are also recorded. The resonant frequency for the limb (i.e. the point at which the peak to peak oscillations of the position and velocity of the limb are greatest) is then used to find muscle stiffness.  This method was developed to provide a simple means of evaluating spasticity  without having to deal with the effects of inertia of the limb and to easily evaluate the spasticity at varying inputs (in this case the level of torque).  This method for the measurement of  spasticity has been successfully correlated with electromyography ( E M G ) of the affected muscles which determines the firing of the motor units in the muscle (i.e.: the activity of the muscle). However, the method of measurement does not follow from the current understanding of the mechanisms of spasticity and as a result it has not received much support. Similarly, the quantification provides only one number (the resonant frequency) from which to determine the degree of spasticity.  Some additional work has been done by a group of researchers [22, 23, 62, 63, 70, 71, 72] who have expanded on the theories put forward by Walsh.  Although their research has not  been used to measure spasticity at the ankle, they have contributed to the pool of knowledge in the measurement of stiffness about the human ankle. Their research compared mechanical and reflex  response  superimposed  evoked by a standardized pulse  stochastic  perturbations.  The results  displacement  with and without  demonstrated that, under certain  conditions, passive joint movement alters stretch reflex gain. Even healthy stretch reflexes can generate substantial torque (approaching 10 Nm). Stretch reflex gain was significantly  35  Chapter 2: Literature R e v i e w  modulated during changes in voluntary contraction, increasing with level of contraction and decreasing as the subject relaxed.  The magnitude of response was shown to depend non-  linearly on a number of factors (amplitude and duration of pulse, angle of the ankle joint, and the level of voluntary contraction). Similar results were found by another research group in Germany [73] using similar techniques and the results were corroborated by Sinkjasr [19, 66] who, using slightly different techniques, concluded that the similarities between their work indicated that stiffness is relatively independent of the type of perturbation, whether it is a consistent step-like perturbation or the pseudo-random stretch as was Kearney's.  2.5  Initial Prototype Development  In order to quantitatively measure spasticity at the ankles of patients in several positions, at variable angular speeds, and to obtain a plot of torque versus time for each of these speeds, a prototype computer-controlled spasticity measurement device was developed. system was built prior to this thesis project and initial testing  The prototype  showed that  successful  quantitative measurements of an applied resistive torque could be obtained.  The prototype device was developed by the R E A C T research group over a period of several years [74].  The device was able to effectively record resistive torque data to passive stretch  about the ankle [74].  T o achieve these measurements, test subjects inserted their foot into a  special foot pedal designed to securely hold the foot in place. The foot pedal was designed so that it was adjustable to allow the subject's ankle to line up with the axis of rotation of the device.  A computer-controlled stepper motor provided torque, increased via a worm gear  36  Chapter 2: Literature R e v i e w  reducer, engaged through an electric clutch and a torque transducer shaft, to rotate the subject's foot in a controlled manner. In doing so, the subject's ankle was rotated through a predetermined rotation and velocity  profile while  resistive torque measurements  were  recorded.  The initial prototype spasticity testing was planned in order to avoid extraneous reflex muscle activity, in which case the stiffness of the ankle joint would be measured at velocities less than 207s. This meant that the maximum angular velocity of the rotation was to be co  max  = 0.35 rad/s.  The testing protocol was developed to passively rotate the subject's ankle joint through a series of repeated trapezoidal position vs. time profiles while recording the resultant resistive torque. A n example of one of the trapezoidal position vs. time profiles is shown in Figure 2.6-1.  0  1  2  3  4  5  6  7  8  9  10  11  T i m e (sec)  Figure 2.6-1 Example of Trapezoidal Position vs. Time Profiles  37  Chapter 2: Literature R e v i e w  In order to accurately manipulate the joint through a desired velocity profile while being subjected to a constantly varying resistive torque, a sufficiently powerful stepper motor was desired.  According to the information available at the time, a torque of 11 N m had been  recorded at the ankle of a patient with severe spasticity.  Since there was much uncertainty  associated with spasticity measurement values, it was decided to use a design factor of two so the torque required to overcome the spastic response was approximately 22 N m . The loading effects of the system measured at no load were approximately 2 N m . This accounted for the friction in the system as well as the gravity effects of the foot pedal at maximum extension. The gravity effects of the foot are already taken into account in the torque to overcome the passive resistance. In addition the torque of the stepper motor was geared down by 30:1 using a worm gear reducer with a conservatively estimated 50% efficiency.  Using these specifications,  the maximum torque required from the motor was determined to be 1.68 N m at 10.5 rad/s. The calculations are shown in Appendix A . A Pacific Scientific motor/driver/indexer package was selected to power the system. This motor met the power requirements to drive the system at the maximum angular velocity of 10.5 rad/s. With 1.8 7step the motor would have to run at:  CO max =  10.5rads/ s ^ 360° „. * = 554steps I s ISPIstep 2K A  At this maximum velocity, the motor provides approximately 1.94 N m of torque which was more than sufficient to power the system.  The package included an integrated programmable  indexer/high efficiency bipolar M O S F E T driver combination.  The specifications  for the  stepper motor package far exceeded those required for the system.  38  Chapter 2: Literature R e v i e w  Although the prototype device existed, it lacked certain features that made it unsuitable for the defined application.  Substantial modifications to the prototype were therefore necessary to  meet the specifications for the current project. In order to determine the exact nature of the changes required, specifications for the current device needed to be defined and corresponding design changes needed to be completed.  2.6  Conclusions a n d S u m m a r y  Spasticity is little understood and a means to measure the effects of spasticity would greatly aid in its understanding.  The physical aspects of spasticity such as stiffness and reflex  response are easily grasped and understood but have been troublesome to model accurately. A number of complicated models exist which attempt to describe the torque response of spasticity.  One of the existing models was chosen for this project and was approximated  with a second order system.  Clinical measurements have proven to be unsuitable for accurate measurement of spasticity. This has lead to a number of attempts to quantify spasticity using device assisted techniques. Use of E M G measurements to quantify spasticity has proven troublesome and difficult. Repeatability of E M G is generally poor and E M G activity is unable to distinguish between voluntary muscle activity and activity due to spasticity. In addition it is unable to include all of the involved muscles, nor does muscle activity alone constitute a measure of the degree of spasticity.  The pendulum test has proven reliable but only measures the quadriceps muscle  and is unsuited for measuring other muscle groups. There has also been some concern over  39  Chapter 2: Literature R e v i e w  the transferability of the pendulum testing protocol. Hand held dynamometers provide only approximate angular velocity and only a single measure of the maximum resistive torque. This is partly addressed by isokinetic dynamometers such as the Cybex II and the K I N C O M . However, the isokinetic dynamometer is used to restrict velocity rather than controlling it. In some cases the systems rely on voluntary movement which is too variable for a truly objective test.  Motor controlled measurement techniques identified into two categories;  those which employed sinusoidal oscillations, and those which employed ramp and hold position profiles.  Sustained sinusoidal movement is both an unnatural movement and is not  analogous to current clinical testing. Using a sinusoidal movement also necessitates the use of servo-motors rather than stepper motors which could also result in some discrepancies in the repeatability of the movement. constant inertia of the limb.  Another problem associated with sinusoidal movements is the  The use of the ramp and hold technique closely models current  clinical practices which are the benchmark against which quantified tests will be measured. B y using a ramp and hold technique, inertia effects are eliminated during the constant velocity stretch.  Several researchers have used ramp and hold techniques to investigate spasticity.  some cases voluntary contractions of the subjects were required.  In  It is felt that voluntary  contractions introduce too much of an unknown into the testing process.  The relationship  between the degree of voluntary contraction, increase in reflex response and change in passive properties is not known.  Two research groups employed a device very similar to the current  project device. Only one of the groups made an effort to quantify spasticity.  Their device was  used to measure reflex threshold angles which were correlated with the degree of spasticity. However, because of difficulties associated with the measurement of reflex threshold the  40  Chapter 2: Literature Review  correlation between their quantifying spasticity and clinical testing was shown to be not statistically significant.  In conclusion, this group suggested that torque measures were a more  useful means of measuring spasticity.  In keeping with that advice, the current project uses a  stepper motor controlled, ramp and hold technique to collect resistive torque data in response to a passive rotation of the ankle joint. It was decided that a stepper motor should be used for the movement control as it provides exact movement control rather that feedback control. The analysis of the experimental data will also be a significant factor in successfully determining a quantitative measure of spasticity.  Attempts to measure spasticity in this manner have already  been attempted by the R E A C T research group using a prototype device which measured the resistive torque due to a passive stretch by a computer-controlled stepper motor and the ramp and hold technique.  41  Chapter 3: Device and Protocol Development  CHAPTER 3: DEVICE AND PROTOCOL DEVELOPMENT  3.1  Overview  This chapter covers the current project's design, and method of operation, of the device developed to quantitatively measure spasticity at the ankle. A n initial prototype design [74] of a device created prior to the current work was found to be insufficient for the testing to be done for this project.  A s a result, portions of the device were redesigned to meet the  specifications of the new device and a testing protocol was developed for use with the new device.  Safety concerns were also addressed in the redesign and corresponding safety  procedures were included in the testing protocol.  Once the design and protocol were  completed, the control system and data acquisition system were developed along with a routine for data formatting and processing.  3.2  Limitations of the Prototype Device  The prototype device lacked a number of features which made it unsuitable for the current project.  The original testing was to be done at much slower speeds than required by the  current project, which meant a more powerful motor would be required.  Safety for test  42  Chapter 3: Device and Protocol Development  subjects, which is a serious concern, was not properly addressed by the prototype device. The prototype driveline was improperly supported and suffered from poor tolerances making accurate measurements impossible.  The control system of the prototype had a poor user  interface, had reliability problems, and was not comprehensive enough to meet the newer protocol requirements. More specifically, the prototype control system was very rudimentary and merely controlled the device to perform one of a few very specific tests which were determined to be unsuitable for the current project.  In addition, simultaneous E M G  measurements were not previously considered, and the device was not equipped for position measurement.  In order to properly redesign the device to meet the current project objectives, a set of design specifications were identified as provided below.  •  A torque output of at least 2.04 N m at 31.5 rad/s.  •  A variable maximum applied resistive torque which could be adjusted for each test subject (by the use of a variable slippage clutch, for example).  •  Maximum safe torque limits monitored by the control software which must have the capability to stop testing if the limits are met or exceeded.  •  A mechanical 'last resort' safety mechanism (such as a shear pin or a ball detente).  •  A precise and reliable driveline.  •  A means to record angular position measurements of the ankle.  43  Chapter 3: Device and Protocol Development  •  A means to obtain and record E M G activity of the involved muscles.  •  A user-friendly, and reliable control system.  •  A control system which can properly accommodate the new testing protocol.  Based on these specifications, the current project requires a motor to overcome resistive torque as high as 2.04 N m at speeds of up to 31.5 rad/s. This requires an upgraded stepper motor, and perhaps a new controller/indexer for the new motor.  More stringent safety  standards are also required for the new device in order to meet university ethics requirements for human testing and to ensure the safety of the test subjects.  In order to obtain meaningful  data, the new device requires a precise driveline arrangement and must be able to collect and store position data as well as E M G activity data to correlate with the spastic reflex torque response.  A n upgraded control system capable of accommodating the more rigorous testing  protocol of the current project will also be necessary.  Finally, in order for clinicians and  therapists to use the device, a more user-friendly interface software program will also need to be developed.  3.3  System Development  After substantial design and development work, a measurement system to meet the objectives of this project has been constructed; a schematic of this system is shown in Figure 3.3-1.  44  Chapter 3: Device and Protocol Development  Figure 3.3-1  Schematic diagram of the computer-controlled system to quantitatively measure spasticity  In a similar manner as the prototype system, but with substantial improvements,  this  measurement system has been designed such that the motor-powered, computer-controlled apparatus can be used to simultaneously measure the resistive torque, ankle position, and muscle activity due to a passive stretch about the ankle joint.  T o accomplish this, subjects  would insert their foot into a molded plastic and foam form mounted to a pedal-type platform specially designed to hold the foot securely in place without exposing the subject's foot to any cold metal. The pedal is adjustable, both vertically and horizontally, so that the axis of rotation of the ankle can be properly aligned with the axis of rotation of the device.  The  maximum angular range of motion ( R O M ) and allowable torque for each individual subject, measured prior to initial testing, will be stored by the computer for future control system comparisons to be used as a safety shutdown if required. Ankle joint rotation is provided via  45  Chapter 3: Device and Protocol Development  a computer-controlled stepper motor, with its torque increased via a worm gear reducer, and engaged  through an electric  clutch.  predetermined rotation and velocity  This  system  profile while  measurements are simultaneously recorded.  will  move  both resistive  the  ankle through a  torque  and position  A t the same time, electromyography ( E M G )  measurements can be taken of the relevant muscle (gastroc soleus) to determine the extent of electrical activity associated with activity of the muscle, for correlation with spastic response. The computer control of the device allows testing to be undertaken at different velocities and duplicate tests to be performed to assess test-to-test and day-to-day reproducibility.  While the basic prototype device concept was used as the basis for the device used in the current project, the inherent limitations of the prototype device necessitated a number of substantial design changes.  These changes to the prototype were performed in five areas;  motor changes, driveline changes, safety component changes, control software changes, and data acquisition system changes.  3.3.1  REQUIRED DESIGN MODIFICATIONS TO THE MOTOR  A stepper motor, as opposed to a servo-motor, was chosen as the best means to power the device because a stepper motor provides accurate position and velocity control without the necessity of a feedback loop.  A stepper motor will provide identical velocity profiles every  rotation. If a servo-motor were chosen, it might not provide consistent velocity profiles under a varying resistive torque.  A servo-motor would perform the rotation but might provide an  46  Chapter 3: Device and Protocol Development  improper velocity profile due to insufficient power or poor feedback control, a condition which could be difficult to identify.  Because of a number of reasons the chosen prototype stepper motor did not provide sufficient power to properly rotate the ankle. Reasons included the higher than expected resistive torque due to spasticity, which was as high as 25 N m rather than 11 N m as originally measured, and the fact that tests were now required to be performed at speeds as high as 607s rather than 207s. A t higher speeds the power provided by a stepper motor reduces dramatically. Because of budgetary constraints combination.  it was impractical to purchase another stepper motor/controller  Pacific Scientific provided a range of stepper motors which operated using the  same controller/indexer combination, so the most powerful stepper motor which operated using the current indexer was purchased.  The system response using this new stepper motor was  found to be superior to that provided by the original stepper motor (see Figure 3.3.1-1). 3 53-i 0  0  New Motor Old Motor  0  Speed (steps/sec)  Figure 3.3.1-1 System response comparison of the two stepper motors  47  Chapter 3: Device and Protocol Development  Most of the testing was done at a maximum velocity of 307s (500 steps/s or 15.75 rad/s) and maximum torques were approximately 25 N m . A t this velocity the stepper motor was required to provide a minimum torque of 1.99 N m to overcome a 25 N m resistive torque at the ankle. According to Figure 3.3.1-1 the stepper motor provides approximately 2.72 N m of torque at this velocity which was deemed sufficient for the research testing. A t test velocities of up to 607s the motor must provide at very least 2.04 N m of torque (calculated in Appendix A ) and in fact, provides exactly 2.04 N m of torque which was deemed marginally suitable for the application. However, in cases where the passive resistance was quite high, testing at speeds as high as 607s was impossible.  The new stepper motor was selected such that it would be sufficiently powerful to accurately follow the desired velocity profile against the expected varying resistive torque. The total range of motion of the device had to be capable of meeting the available range of motion for a human ankle joint. The mean values of ankle rotation for the general population are 3 5 ° flexion and 3 8 ° extension for a total range of motion of 7 2 ° .  It was decided that a minimum range of  motion for the system was 9 0 ° . However, given that the device had to accommodate testing of different joints, with a subject in a variety of positions, it was deemed appropriate for the device to have a range of motion of a full 3 6 0 ° .  The stepper motor torque was geared down using a 30:1 worm gear reducer. This allowed the use of a cheaper and lighter stepper motor which provides smoother rotation at the foot pedal, while the choice of gearing avoids the problems associated with resonance at the desired  48  Chapter 3: Device and Protocol Development  driving speeds. Typically the natural frequency of a stepper motor is in the range of 90 to 160 steps/s. The device currently operates between 330 and 1000 steps/s (which translates to 207s to 60 7s at the ankle).  3.3.2  Required Design Modifications to the Driveline  Several components of the driveline needed to be redesigned.  The couplings were poorly  designed in the prototype between the stepper motor and the worm gear reducer, the electric clutch and the torque transducer shaft, and the torque transducer shaft and the foot pedal shaft. The poorly designed couplings of the prototype device were held with only a set screw to transmit torque.  The set screw often slipped when subjected to applied torque.  For  example, the foot pedal shaft was only 12.5 mm in diameter and so, with only a set screw to couple it to the torque transducer shaft, the transmitted torque values were large enough to cause the set screw to score the foot pedal shaft.  In addition, the couplings were poorly fit  and of low tolerance so the driveline suffered from 10-20  degrees of backlash.  redesigned couplings all used keyed shafts with proper tolerances. slippage and considerably reduced the backlash problem.  The  This eliminated driveline  The prototype device bearing  supports were all single bearing supports which did not adequately support the driveline under load and required the driveline to carry a bending moment in certain regions, especially with the subject's foot loading the foot pedal.  T o correct this problem the driveline was  redesigned with dual bearing supports allowing each bearing support to independently carry the load.  49  Chapter 3: Device and Protocol Development  3.3.3  Safety Components  Safety was a major concern during the design and implementation of the device.  Since the  subject's foot was to be securely strapped into a device driven by a motor, numerous safety measures were deemed necessary in order to ensure the subject's safety. Computer control of the device provided the first level of safety. Before testing began, the device was used to record the subject's maximum voluntary contraction. A percentage of this value was then used as a limit for the recorded torque during the testing. The control software included a feedback loop from the torque transducer and if the maximum pre-set torque levels were exceeded, the control software would immediately shut down the stepper motor to prevent possible injury to the subject.  Similarly there were 'panic' switches provided which either the subject or the  tester could use to terminate a test at anytime if they felt uncomfortable. In the initial prototype, the electric clutch was intended to be employed as a safety device as it would slip if the transmitted torque exceeded a maximum value. The prototype's clutch was designed to slip at approximately 30 N m which may be sufficiently low to test individuals with sturdy ankles, but for many individuals this slippage torque was too high to ensure safety.  In addition, in  some cases where resistive torque values higher than 30 N m might be encountered, the slippage torque could be too low to allow proper testing. The solution to these problems was to replace the clutch with a variable slippage electric clutch.  The new clutch would slip  proportionally to the supply voltage which could be varied by the user.  The new clutch  offered a selectable slippage torque from 0 to 50 N m , allowing the slippage torque to be reset for each new test subject as required. If the amount of resistive torque exceeded a pre-set safe level, the clutch would slip preventing excessive torque from reaching the subject's  50  Chapter 3: Device and Protocol Development  ankle. Since the clutch is an entirely separate system from the computer control of the device and is set by the tester for each individual prior to testing, it provides an additional fail-safe unaffected by a potential failure of the computer-control.  The variable slippage of the clutch is set by the tester by modulating the power supplied to the clutch. This is accomplished by choosing the supply voltage based on ordinal settings, from 1 to 10, on the power supply. These ordinal settings are correlated with torque values in Newton meters as shown in Table 3.3.3-1.  The correlated values were obtained by  comparing the torque levels recorded by the device during slippage at a given level on the clutch, averaged over five recordings, each recording being at least 20 measurements.  Setting on clutch  Recorded torque at  Extrapolated torque for  slip (Nm)  common settings (Nm)  1  0.0  (0.0)  2  2.1  2.1  2.5  7.4  2.75  10.0  3  12.3  12.7  3.25  15.3  3.5  18.0  3.75  20.6  4  23.2  23.2  4.25  25.9  4.5  28.5  4.75  31.2  5  33.8  33.9  Table 3.3.3-1: Variable slippage clutch testing results  51  Chapter 3: Device and Protocol Development  The calibration curve for presetting torque values was found to be; T = 10.56C -19 where T represents the ensuing torque (Nm) and C represents the equivalent ordinal settings on the clutch power supply. A graph of the results is shown in Figure 3.3.3-1.  Caculated X  Experimental  Ordinal Clutch Values  Figure 3.3.3-1 Relationship between the ordinal scale on the variable slippage clutch actual torque values  In the worst case scenario, i f a control and electrical failure should occur, a mechanical torque limit is ensured by the use of a shear pin which w i l l break thereby ensuring the safety of the subject and providing a fail-safe system. The coupling between the torque transducer and the foot pedal shaft is secured with a pin linking overlapping shafts. that it can serve as a mechanical "fuse".  This pin is sized so  If an "absolute" safe torque limit is exceeded  (assuming all other safety mechanisms fail) this mechanical "fuse" w i l l break thus halting the device.  M a k i n g the device operational again is a simple matter of replacing the pin.  The  52  Chapter 3: Device and Protocol Development  'strength' of this mechanical fuse can be modulated by the use of different size shear pins in order to accommodate the different ankle strengths of various subjects.  The torque required to shear the shear pins was determined by experimental testing using a jig identical to the coupling between the torque transducer and the foot pedal shaft.  Shear pins,  made of 1/4 inch 6061-T6 aluminum rod were radially grooved to varying inner diameters at the point where the couplings joined using a 1/16 inch radius tool.  Figure 3.3.3-2 shows a  schematic of the jig used to test the shear pins and a depiction of a shear pin.  XX  XX ^  Shear pin inserted here  A Torque  Figure 3.3.3-2 Schematic of testing jig used to measure torque to failure of shear pins  The tests were conducted using an Aries Model 2 0 0 - D B B - U 200 lb. S-Beam tension load cell and  recorded using a Houston Instruments Series 2000 Omnigraph X - Y recorder while  applying torque manually using a large wrench.  The averages of the measured results were  found to be exponential and fit a curve of;  T=3.2D  295  53  Chapter 3: Device and Protocol Development  where T represents torque (Nm) required to shear the shear pin and D represents the equivalent diameter (mm) at the radial groove of the shear pin. A graph of the results is shown in Figure 3.3.3-3.  Figure 3.3.3-3 Torque to failure results compared to fitted equation  It was expected that the relationship between the diameter at the radial groove of the shear pin and the torque required to shear the pin would be exponentially related to the diameter cubed. Because of the radial groove at the interface of the coupling, the forces on the shear pin would be, strictly speaking, an applied moment rather than a shear force. In this case, the torque required to 'shear' the pin should be related to bending of a short beam [75, 76] affected by the stress concentration factor, due to the decreasing radial groove diameter. In fact, the relationship was proportional to D  2 95  . Table 3.3.3-2 shows the results of shear pin  testing averaged from five measurements.  54  Chapter 3: Device and Protocol Development  Diameter of shear  Grooved  Average torque  Extrapolated  pin (mm)  diameter (mm)  required to shear  torque required to  (Nm)  shear (Nm)  (6061-T6 Al) 6.35  2.54  5.0  5.0  6.35  3.81  16.7  16.6  6.35  4.06  20.0  6.35  4.32  24.0  6.35  4.57  28.3  6.35  4.83  33.3  6.35  5.08  38.7  38.7  Table 3.3.3-2: Shear pin testing results  The results were interpolated to determine the torque required to shear pins of differing radial groove depths in order to determine the size of shear pin required for any individual test subject.  A selection of shear pins was available before the testing took place so that the  appropriately sized pin could be selected for each subject.  Conservatively sized shear pins  were to be used when the exact size was not available.  The final safety aspect of the design was to provide mechanical stops on the device which can be set manually by the tester based on the subject's joint limits.  These mechanical stops  prevent the device from exceeding the joint limits as determined in the pretest subject joint limit test.  55  Chapter 3: Device and Protocol Development  3.3.4  C o n t r o l Software Design  The control software provides an interface for the physician or other user of the device to conduct testing and data acquisition. The control software guides the user through the testing protocol, and when required, initiates data acquisition, and automatically determines and initiates a program which activates the stepper motor.  Control software changes required a  completely new control system utilizing a M i c r o s o f t ® Windows environment for ease of use. The Windows-based event-oriented  programming graphically allows the user to chose a  selection of options resulting from previous decisions.  The new stepper motor controller  required a new communication protocol as did the new data acquisition board.  A more  rigorous testing protocol was also programmed into the new software including stepper motor control options, stepper motor programming, more flexible data acquisition, and better file management.  The new  software also included a feedback  loop from the torque  transducer to a comparator function in the control software which ensures the test is terminated if maximum torque levels are exceeded.  If the maximum torque levels are  exceeded, the control software would immediately shut down the stepper motor to prevent possible injury to the subject.  The  control software for the device was  initially written in ' C and Pascal and was  subsequently rewritten in Visual Basic 3.0 in order to run the software in the M i c r o s o f t ® Windows environment.  A number of issues regarding programming in a M i c r o s o f t ®  Windows environment needed to be addressed.  The control software makes use of several  second party packages including those which run the data acquisition board (discussed in  56  Chapter 3: Device and Protocol Development  Section 3.3.5) and two Visual Basic V B X ' s (a Visual Basic 'custom control' which provides a number of built in features to assist programming) to facilitate the control of the stepper motor and the data acquisition system.  The public domain communication Visual Basic  control, V B C O M M . V B X Version 2.0 for Visual Basic 3.0, by Mark Gamber (August 1992), was used to set up RS-232 serial port communication with the stepper motor controller, send commands to the controller, receive replies from the controller and perform additional similar functions.  Since M i c r o s o f t ® Windows uses a 57 millisecond internal clock, Visual Basic  timers can only be activated every 1000 ms/s / 57 ms = 16 H z and therefore could not reliably control timing of the data acquisition and motor control.  A s a result, the high speed timer  control, H I T I M E . V B X , from Mabry software was substituted to control the timing of the data acquisition and motor control.  The Hitime control allowed timing to take place at one  millisecond intervals so the timing of the data acquisition would have no more than 2.5% error.  The event-oriented nature of M i c r o s o f t ® Windows programming makes the software  self  explanatory. Each time an event takes place, the software responds by presenting the user with new choices resulting from the previous decision.  Each of the users choices is graphically  represented as a push button, text box, or option button selection. B y simply selecting the next appropriate choice, a new set of choices is presented.  More detailed information on the  program can be found in Appendix B which contains the source code for the device control software.  57  Chapter 3: Device and Protocol Development  Data files are recorded and stored by the computer as T A B delimited A N S I files (text files where the data is divided by the T A B character; H E X 0x09). Separate files are recorded for position (degrees), resistive torque (Nm), and E M G activity (percentage of maximum output) for each test. Each of the files includes the measured data recorded every 40 milliseconds as well as important header information such as the total range of the test and the maximum allowable torque. Velocity of the test and the order of the tests, along with the initials of the individual tested and the type of data are indicated by the title of the data file. For example, file names ending in e, p, t indicate electromyography, position, and resistive torque data respectively. The second last digit in the name indicates the order of the test (starting at zero) while the preceding two characters indicate the speed of the test in degrees per second. Any preceding characters (up to three) are input by the tester to identify the subject. The data files all have the extension *.dat (for example jra301t.dat). importing them into either M i c r o s o f t ®  The data files are post-processed by  Excel or M a t l a b ®  depending on the type of  processing required.  3.3.5  Design Modification to the Data Acquisition System  Data acquisition drivers are used to initialize, and control the data acquisition board.  The  control of the data acquisition board entails initiating each data acquisition cycle to collect the raw torque, position, and E M G data which is passed on to the control software for filtering and storage. Data acquisition refinements required replacing the prototype data acquisition board with a faster board which had a driver usable within a M i c r o s o f t ® Windows operating environment.  The device had to be modified to include angular position and E M G  58  Chapter 3: Device and Protocol Development  measurements, and amplifiers for the torque transducer and E M G signals were required. Data acquisition is done using a C I O - A D 0 8 (Computer Boards Inc.) data acquisition board. The board offers eight 12 bit A / D channels (a bit underrated for this application because of the resolution - a 16 bit board would be more suitable), 3 digital inputs, 4 digital outputs, and three 16 bit down counters.  Input frequencies up to 2.5 M H z can be handled by the board. A / D  conversion time is typically 25  microseconds  and using the supplied software  throughputs of up to 4000 samples/sec can be attained operating under B A S I C . software receives three channels, sampling at 2000 samples per second.  driver,  The control  The 12 bit analogue  inputs offer full scale +/- 5 V , with a resolution of 2.44 millivolts. The Computer Boards Inc. Universal Data Acquisition and Control Library Revision 3.0 is used to acquire the data and control the A / D board. The Universal Library provides a M i c r o s o f t ® Windows dynamic link library file (cbw.dll) which is used by calling functions from the Visual Basic application to initialize the board and to collect data from the board. Once the data has been received from the data acquisition board, the computer sends the data to user written comparator functions to determine if the resistive torque data is within the safe limits established earlier, and then stores the data to file.  The data acquisition system records the following data (refer to Figure 3.3-1):  •  One analogue signal from the strain gauge bridge located on the torque transducer shaft  •  One analogue signal from the potentiometer integrated into the coupling between the foot pedal and the torque transducer shaft  59  Chapter 3: Device and Protocol Development  •  One analogue signal from the E M G amplifier collected from electrodes attached to the subject's lower leg  Torque is measured by strain gauges on the torque transducer shaft.  The strain gauge signal  processing and design is discussed in Appendix A . The torque measurements are amplified, converted to digital and sent to the computer to be recorded. The amplified signal is converted to torque (Nm) in the control software using a predetermined calibration constant.  The torque  data is then reduced to the resistive torque by subtracting the inertial and frictional torque due to the driveline and foot pedal, adjusted for velocity and angular position. The bandwidth of the strain gauge was designed to be sufficiently large so that feedback from the gauge can be used to immediately stop the stepper motor in the event the resistive torque approaches an unsafe level. Assuming a common 200 steps/rev stepper motor operating at 5 rev/s, the stepper would be performing 1000 steps/s in order to rotate the ankle joint at the specified 607s. The strain gauge would have to operate at a minimum of 2000 H z to stop the stepper before the next pulse. A suitable bandwidth for the strain gauge was determined to be at least 2000 H z .  At the same time as resistive torque measurements take place, the potentiometer measures the angular displacement of the joint. These measurements are also sent to the computer via the same A / D board. The signal from the potentiometer is simply converted in the control software to degrees of rotation using a pre-calibrated correction constant.  E M G Electrodes affixed to the test subject's lower leg passively register small electrical impulses (voltages) which indicate activity of the muscle being monitored. The E M G signal  60  Chapter 3: Device and Protocol Development  passes through a G R A S S P5 Series A . C . Pre-Amplifier to the control computer where it is calibrated to a zero mean, rectified, and converted to a percentage of the maximum voluntary contraction E M G .  3.4  Testing Procedures  A n important aspect of the testing is the protocol used to acquire measurements.  Initial  testing of the device was to be done on subjects without spasticity to assess the repeatability of the device and its suitability as a clinical measurement device, as well as to provide data on a control group for future comparison with a group with spasticity.  Subjects with  spasticity were then to be tested to assess spastic response to ankle rotational velocity. Electromyography was to be utilized to detect muscle firing patterns for correlation with spastic response, resistive torque data.  This was to be used to identify increases in stretch  reflex resistance associated with extraneous muscle activity.  This information was to be  gathered on a variety of subjects exhibiting spasticity and correlated with both day-to-day, person-to-person, and possibly within disease groups.  The goal is to better understand the  effect of these factors on spastic response and to provide recommendations for minimizing and/or treating spasticity in a hospital environment.  Testing procedures or protocols for using the device as a measurement tool are reviewed below. A l l subjects provided informed consent before testing took place.  The consent forms and  information provided to each subject are shown in Appendix C . Initially the subject should be made as comfortable and relaxed as possible. They should be seated comfortably, at the proper  61  Chapter 3: Device and Protocol Development  height with the foot pedal in the horizontal position.  Before any testing takes place, E M G  electrodes will be placed on the relevant muscles (of the shin and calf) according to testing protocols established for the electromyography.  The testing protocol for this device is currently established as follows:  1.  The subject is to be in one of two or three positions; i) Seated with the upper leg horizontal and the knee joint at 9 0 ° . ii) Lying prone with the leg straight. iii) Standing with the testing foot resting on the device, and with the subject's weight equally distributed between each leg, in order to simulate the effects of the subject's weight on spasticity.  2.  Position the foot pedal so that the subject's ankle joint coincides with the axis of rotation of the foot pedal and strap the subject's foot firmly in place.  Ensure that the  foot pedal is level.  3.  Determine the maximum safe torque for the subject's ankle. This is done by the subject applying a maximum force voluntary contraction to the foot pedal while the computer records the torque output.  The maximum safe torque limit is then set to 90% of the  maximum level. This maximum safe torque limit is then entered into a control software routine which monitors the torque at the ankle and disengages the motor if the  62  Chapter 3: Device and Protocol Development  maximum torque limit is met or exceeded.  This value is also used to select the  appropriate shear pin and variable clutch safety settings to ensure the subject's safety.  4.  Determine the range of motion for the subject's ankle. The computer-controlled stepper motor rotates the subject's ankle until some discomfort occurs or until the maximum safe torque limit for that subject is reached while the computer records the angles corresponding to the joint limits. This stage must be repeated for each position of the subject.  Once the joint limits are established and recorded by the computer for each  subject position, they can be used to construct the testing  velocity profiles for  subsequent testing. Physical stops on the foot pedal can also be set to limit the range of motion of the device within the safe joint limits to ensure the subject's safety.  5.  T o begin the testing procedure, the tester is simply asked to choose one of seven velocities for the ramp and hold testing. 207s, 307s, 407s, 507s, or 607s.  The seven velocity options are 57s,  107s,  The computer automatically designs a velocity  profile for each chosen velocity defined by the established joint limits.  The control  software configures, downloads, and launches a program in the stepper motor controller and initiates data acquisition to collect the data from the torque transducer, the potentiometer, and the E M G transducer. Data is recorded and stored in the computers memory for post processing.  6.  The actual manipulation of the ankle by the device will start at 0 ° (with the ankle joint at 9 0 ° to the subject's lower leg) and proceed through the ankle's dorsi-flexion range to  63  Chapter 3: Device and Protocol  Development  the maximum joint limit as illustrated in Figure 3.4-1. The testing performs a ramp and hold test which means that the ankle joint is rotated at a constant velocity through the viable range of motion. A t the end of the range of motion, the joint is held at the extent of its range for four seconds in order to detect any beats of clonus and to determine the steady state resistive torque. If clonus is present the ankle will rhythmically spasm and the torque and frequency will be recorded by the computer.  The joint is then slowly  returned to the starting position in preparation for the next test. This procedure is likely to be the primary function of the device as it fulfills the requirements conceived for the project.  This test would be used to establish how spasticity can be defined using the  data collected by the device.  Figure 3.4-1 Depiction of the rotation of the ankle joint during testing  It should be noted that, for the purposes of this project, any future reference to range of test refers to a testing rotation as shown in Figure 3.4-1. Also, references to maximum range refer  64  Chapter 3: Device and Protocol Development  to the subject's maximum range in dorsi-flexion as depicted in Figure 3.4-1. Starting position, or neutral position refers to the subject's ankle joint being 9 0 ° to the lower leg, as it is labeled as  'Begin Test'  in the figure.  Ideally clonus testing would determine the torque level at which clonus occurs, measure the length of time the clonus continues, measure the spasm torque from the clonus, and the frequency of the spasms.  The device should be able to perform all these tests at different  patient positions considering effects of the subject's weight and so forth. This would require an in-depth study which goes beyond the scope of the current project. In the future, a simple test for clonus could be incorporated into the device to test the feasibility of further clonus testing.  Data could also be collected for variations of the above test using different knee joint angles to investigate the position dependence of spasticity, and with the subject standing to study the effect of the subject's weight on spasticity of the ankle.  Continued clinical testing of the  spasticity measurement device will be directed towards developing a family of resistive torque versus time curves which reflect the characteristics of spasticity and to provide proof of the clinical usefulness of the device.  65  Chapter 4: Data A n a l y s i s , Results and Discussion  CHAPTER 4: DATA ANALYSIS, RESULTS AND DISCUSSION  4.1  Overview  The device has been utilized to collect data from groups of people with and without spasticity. Initial testing on subjects without spasticity was used to assess the suitability and repeatability of the device, as well as provide data as a control group for future comparison. Subjects with spasticity were then tested to assess variations in spastic response.  This data  was carefully analyzed to determine any relevant trends indicating spasticity.  The data  within subjects having spasticity was also examined to determine variations of those trends with the degree of spasticity.  B y exploiting indications of spasticity which varied with  degree of spasticity, a means to model the observed variations of the data was determined and used to quantify the degree of spasticity.  A statistical analysis of the data collected by the  device was performed to assess the potential of this measure as a reliable, quantifiable, statistical indicator for spasticity.  4.2  Data Analysis  The chosen protocol for testing of the device involves two stages.  In the first stage, the  subject's ankle is rotated through a predetermined arc, corresponding to the subject's joint limit  66  Chapter 4: Data Analysis, Results and Discussion  in dorsi-flexion, at a specified number of selected velocities.  During the second stage, the  subject's ankle is held stationary at the maximum extent of the arc for four seconds.  The first  part of the testing is done to evaluate the velocity dependence of spasticity and elicit a resistive torque to the movement. The second portion of the testing is used to observe the reaction of the joint when held at the limit of dorsi-flexion which allows the determination of the steady state gain with respect to the position and velocity input. In addition, the second stage of the test may induce clonus which manifests itself as regular oscillations of the joint. The severity of the clonus response is often used as an indicator of the degree of spasticity.  The resistive torque, position, and E M G data retrieved from the testing was transferred to a M i c r o s o f t ® Excel spreadsheet for analysis. Curves of resistive torque versus time, and E M G response vs. time were plotted. The torque data curves within a testing session were averaged and plotted. In addition, the time for each test was normalized so that the ramp time was one second for any velocity and for any range of ankle rotation.  This allowed for a visual  comparison of results from tests at different velocities in order to determine if there was a significant velocity dependence in the results. Data was also plotted against position, and E M G activity in order to correlate the results with angular motion of the joint and activity of the muscle.  The data from M i c r o s o f t ® Excel was ported to M a t l a b ® in order to fit an equation relating the input position with the output (resistive torque) over time.  Parameters of this equation were  then analyzed for use as indicators of the severity of spasticity. The parameter data was then  67  Chapter 4: Data Analysis, Results and Discussion  compared to a curve separating data from subjects with and without spasticity using M a p l e ® . The results of the comparison were used as a quantitative indicator of the degree of spasticity.  The following sections explain in detail the procedures leading up to and including the analysis of the data and the determination of a quantitative measure of spasticity.  Also included is a  statistical analysis of the results reviewing the reliability of the testing data and the results.  4.3  Evaluation of Results  Torque versus time curves are the most obvious method of analyzing the test data. A typical resistive torque versus time curve of a subject without spasticity is shown in Figure 4.3-1.  0  1  2  3  4  5  6  Time (sec)  Figure 4.3-1 Typical resistive torque versus time curve of a subject without spasticity at 20°/s  68  Chapter 4: Data A n a l y s i s , Results and Discussion  The two stages in the testing process, the velocity dependent section and the hold period at the extent of the range section, (divided at point A ) can be considered separately or together in the analysis of the data. O f potential interest in the resistive torque versus time curves are a number of salient features which have, in the past, been considered as an indicator or measure of spasticity.  These features include the maximum resistive torque, the slope of the velocity  dependent curve, the area under the two portions of the curve (Torque vs. Position - total energy expended), the reflex threshold, reflex gain, onset and amplitude of the E M G response, and inconsistencies  in the smooth torque profile such as uncontrolled oscillations, or the  number and strength of clonus beats. Considerations of the E M G data which can indicate the degree of spasticity include the bandwidth of the E M G results, deviations and number of excursions from the average bandwidth, and the maximum bandwidth.  Correlation of the  E M G data with the resistive torque data can also be done to try to differentiate between the spastic response and the intrinsic stiffness of the ankle joint. If significant E M G activity is observed during a passive stretch, then a spastic reflex response must be present. However, if little or no E M G activity takes place, the observed resistance is due solely to the intrinsic stiffness of the ankle joint.  The most obvious and commonly used parameter among the traditional measures of spasticity is the maximum torque value obtained during the test.  The maximum torque value is  considered a large influencing factor in common clinical scales such as the Modified Ashworth Scale ( M A S ) .  Clinical testing provides a more general feel for the resistance that is then  translated into a qualitative feel for the behavior of the joint.  In the current test results, the  maximum torque was affected by the range of angular motion of the test, and possibly by other  69  Chapter 4: Data A n a l y s i s , Results and Discussion  more esoteric factors such as comfort, or fatigue of the subject. Moreover, there did not appear to be any correlation of maximum torque values with the degree of spasticity, and in fact, maximum torque values were, in some cases, higher for subjects without than with spasticity. A s a result, maximum torque values cannot be used as a realistic indicator of spasticity.  The gradient of the increasing torque vs. time curve was analyzed to determine if it could be indicative of the resistance to movement with respect to the velocity and extent of the angular motion.  However, this requires that the increase in the resistive torque with movement be  linear, the data collected showed this area of the curves to be quite non-linear. In addition, the value of the slope is subject to the vagaries of range of motion and the velocity of the test. Finally, to use slope to describe spasticity demands that, at a certain velocity, the maximum torque value must be related to the degree of spasticity, which has not proven to be the case. A s a result, the slope does not appear to be a useful means of quantifying spasticity.  Reflex threshold is defined as the angular threshold at which the stretch reflex occurs and is identified as the point where the resistance to manual stretch abruptly increases.  If the reflex  threshold is reduced, a smaller and/or slower motion would be sufficient to reach the reflex threshold at which point the reflex torque or force of the muscle shows a marked increase with increasing muscle length. The onset of an abrupt increase in torque can prove very difficult to determine given the somewhat inconsistent nature of the torque curves.  Moreover, it is not  clear whether people with little or no spasticity even have a reflex threshold (except for one which may activate to prevent over-rotation of the joint). Research work in the past had used E M G to determine the onset of the reflex muscle firing which defines the reflex threshold  70  Chapter 4: Data A n a l y s i s , Results and Discussion  because resistive torque curves themselves cannot accurately provide a measure of the reflex threshold. However, using E M G requires very precise and accurate measurement.  Because of  the complications and inconsistencies associated with the use of surface E M G , this is not a practical measure of spasticity. Similarly using the severity of the E M G response as a measure of spasticity only provides a qualitative measure of the degree of spasticity, as the E M G response can vary significantly (an order of magnitude) depending on the placement of the electrodes. In order to get a (semi-) qualitative measure of E M G , a baseline is required. In the initial testing using this device, a baseline was achieved by asking the control test subjects to provide a maximum voluntary contraction and the subsequent E M G results were compared to this maximum amount.  This technique seemed to work quite well in subjects without  spasticity, however, subjects with spasticity had difficulty eliciting a maximum voluntary contraction or could not provide one at all.  Reflex gain is characterized by an abnormal increase in reflex force with increasing rotation of the joint. During a passive angular rotation of a joint, the intrinsic stiffness of the joint provides a degree of resistive torque. If reflex activity of the involved muscles occurs (as may be the case with spasticity) the corresponding reflex action of the muscles contributes to the total stiffness of the joint. This additional stiffness is referred to as the reflex gain. However, reflex gain is difficult to measure directly as it requires some fore knowledge of the reflex curve without reflex gain. Reflex gain has proven troublesome to measure in the past and, in addition, can be largely influenced by input velocity and angle of rotation. A more appropriate and more informative measure of spasticity might be the steady state gain, K, with respect to the input position profile.  Steady state gain refers to the ratio of the output of a system after it has  71  Chapter 4: Data A n a l y s i s , Results and Discussion  stabilized, with respect to its input. In the case of the current project, the input is the angular position and the output is the resistive torque.  Steady state is achieved after the system has  settled, and, in the case of the current project, is considered to occur four seconds after the motion stops. In this manner the resistive torque gain could be relative to the range of the test. This gain, K, as a measure of spasticity, might be more suitable for comparisons over a variety of testing ranges.  A thorough analysis of the data generated by the device is needed to reveal the most valuable indices of spasticity. The traditional measures mentioned above (i.e. maximum torque, slope of the torque vs. time curve, reflex gain, and reflex threshold) are either too difficult to measure or are not suitable as a measure of spasticity.  B y comparing several sets of data  from subjects with spasticity with data from the control group, it is hoped to be able to isolate the most useful indications of spasticity.  A n in-depth analysis of the control data compared  to the data from subjects with spasticity is required to define a pattern suitable to distinguish between the two groups.  4.3.1  Evaluation of Data from Subjects Without Spasticity  Test data was plotted in a number of ways to help graphically analyze the data. Curves were generated of torque vs. time, averaged torque vs. time, averaged torque vs. normalized time, plus torque and position vs. time.  E M G activity was also correlated with the torque data by  including the E M G results in some of the graphs.  72  Chapter 4: Data A n a l y s i s , Results and Discussion  Within a test session (i.e. in a single day) up to ten tests were performed at each velocity. Correlation between these tests was found to be good (covariances were as high as 40). However, in order to more accurately analyze the data, averaged torque curves were used because they provide a more accurate description of the general behavior. Figure 4.3.1-1 shows a family of torque curves from a single test session. The tests were all performed within an hour of each other and while the subject remained connected to the device.  o  1  2  3  4  5  6  Time (sec)  Figure 4.3.1-1 Resistive torque responses of a subject without spasticity to passive rotation about the ankle joint within a test session (20°Is)  B y comparison, the same group of data is shown as an averaged torque vs. time curve including position in Figure 4.3.1-2.  73  Chapter 4: Data A n a l y s i s , Results and Discussion  Figure 4.3.1-2 Averaged torque response of a subject without spasticity to a passive rotation about the ankle joint at 20°/s  This curve illustrates the typical behavior observed in the data from subjects without spasticity. The curve exhibits a generally linear ramp of increasing torque in the velocity  dependent  portion of the testing. A s the motion stops, the torque abruptly stops increasing and retains its level throughout the four second position 'hold' portion of the test.  Occasionally a slight  overshoot is observed at the transition between the velocity and holding portions of the curve, most likely due to the momentum of the foot. Using this data for subjects without spasticity, a number of traditional parameters, such as slope, maximum torque, and area under the curve could be determined.  However, without corresponding data from subjects with spasticity, no  sound conclusions can be drawn.  74  Chapter 4: Data Analysis, Results and Discussion  To determine if any velocity dependence exists between the various test results, a number of averaged torque versus normalized time curves were generated. The time component was normalized so that the curves could be directly compared. Figure 4.3.1-3 compares averaged torque vs. time curves of different velocities without normalized time.  14  i  0  1  2  3  4  5  6  7  8  9  10  Time (sec)  Figure 4.3.1-3 Comparison of averaged torque vs. time curves of different velocities  It is obviously difficult to objectively analyze these curves because of their differing slopes. The solution to this problem is to normalize the curves. By normalizing the time during the position ramp to a unit value (in this case one second) resistive torque curves at differing velocities can be directly compared to establish any velocity dependence. A comparison of averaged, resistive torque curves of different test velocities plotted against normalized time, from a subject without spasticity, is shown in Figure 4.3.1-4.  75  Chapter 4: Data A n a l y s i s , Results and Discussion  Time  (sec)  Figure 4.3.1-4 Averaged torque vs. normalized time curves of different velocities  In this case it is clear that the torque curves from different test velocities can be visually compared in an easy manner.  It is clear that for subjects without spasticity there does not  appear to be any significant velocity dependence of the torque response at velocities as high as 607s. Although there may be velocity dependence of the torque response of subjects without spasticity to a passive rotation of the ankle at higher velocities, none was observed i n the control test data from this project.  The control group of subjects without spasticity showed little or no E M G response during tests at any velocity. The control group E M G response during tests was compared to E M G values obtained during a maximum voluntary contraction.  In this manner the E M G response was  quantified as a percentage of the maximal contraction level. Figure 4.3.1-5 shows a typical E M G response during a test of a subject without spasticity.  76  Chapter 4: Data Analysis, Results and Discussion  1  n  0  r  1  2  3  4  5  40  6  Time (sec)  Figure 4.3.1-5 Control EMG response (20°/s), including position of the test (in green)  There was little or no E M G correlation with torque increases for the control group. It is clear that normal behavior of the joint during a test is largely due to the intrinsic stiffness of the joint, muscles, and connective tissue and that no significant reflex action of the involved muscles takes place.  In order to determine the most valuable indicator of spasticity, the control group data must be compared to data obtained from individuals with varying degrees of spasticity. In doing this the most salient differences between the two groups of data can be exploited to establish a means to quantify spasticity. This requires a similar analysis of test data from subjects with spasticity.  4.3.2  Evaluation of Data from Subjects With Spasticity  Comparison of data from subjects with spasticity and the control group data is an obvious method to determine differences between the data which ought to be indicators of spasticity.  77  Chapter 4: Data Analysis, Results and Discussion  However, in order to determine differences in the data related to the degree of spasticity, data within the groups of people with spasticity should also be compared.  In this manner,  differences which indicate the severity of spasticity can be established and corroborated against the control data. A number of issues traditionally related to spasticity were also investigated, such as E M G activity correlation with increased resistive torque, velocity dependence of spasticity, occurrence of clonus, and the clasp knife phenomenon.  Data from the subjects with spasticity were also subjected to a similar analysis as was the control data. Initially two subjects with mild degrees of spasticity were tested and evaluated. Due to the tiring effects of testing, only five tests were performed at each velocity.  Figure  4.3.2-1 shows resistive torque responses of a subject with mild spasticity to passive rotation about the ankle joint within a test session.  Figure 4.3.2-1 Resistive torque responses of a subject with spasticity to passive rotation about the ankle joint within a test session (40°Is)  78  Chapter 4: Data A n a l y s i s , Results and Discussion  There were a number of minor differences between the curves of subjects with and without spasticity but it was not clear whether they were significant or coincidental. Primarily the variances were the transition between increasing torque and steady torque, which was not as sharp, the increasing torque curve, which was slightly less linear, and a more significant overshoot of the steady state torque value at four seconds. However, the differences were very subtle and not the exaggerated differences, which might be expected from an individual with severe spasticity. In order to determine whether the small noted differences were significant, a third subject with severe spasticity was tested.  The averaged resistive torque responses to  passive rotation about the ankle joint of the three subjects is shown in Figure 4.3.2-2.  > Hold Point  Mild Spasticity #1 Mild Spasticity #2 Severe Spasticity  0  1  2  3  4  5  Time (sec)  Figure 4.3.2-2 Average torque vs.timecurves of three subjects with varying degrees of spasticity at 30°/s  With the addition of the third subject with severe spasticity, it was observed that some of the characteristics of the curves of the two subjects with mild degrees of spasticity became more pronounced in the case of the subject with severe spasticity.  One of the more obvious  79  Chapter 4: Data A n a l y s i s , Results and Discussion  differences was the amount of overshoot with respect to the steady state gain. For the subject with severe spasticity, after the angular velocity ceased (at t = 1.18 sec), the curve kept rising and then slowly diminished.  Also noted in the case of severe spasticity was a smoothed  transition from the velocity dependent section to the holding section. These same features were also noted in the data from the subjects with mild spasticity, but to a lesser extent.  An  exaggerated curvature of the resistive torque curves which was more pronounced in the data from subjects with mild spasticity was less obvious in the subject with severe spasticity. This curvature was still evident in data from the subject with severe spasticity but the curvature took place at the very beginning of the test over a very short period of time, so it was less obvious. A s these features (over shoot and subsequent decreasing resistive torque, exaggerated curvature, and smooth transition from the velocity dependent section to the holding section)  were  consistent in subjects with spasticity, and appear proportional to the degree of spasticity, they appear to be potential parameters to quantify spasticity.  Electromyographic activity of the involved muscles, indicating firing or activity of the muscles, was correlated with increases in resistive torque and with position.  It was found that the  subjects with spasticity had significantly more muscle activity taking place during the tests, particularly at the end of the range of motion.  This observation lends some support to the  theory of reflex threshold. A s the subjects were asked to relax and the rotation of the joint was passive, the increase in muscle activity is probably attributed to reflex reaction of the involved muscles. E M G activity of a subject with mild spasticity correlated with position of the test is shown in Figure 4.3.2-3. The rotation of the joint occurs in the increasing section of the blue curve in the figure.  80  Chapter 4: Data A n a l y s i s , Results and Discussion  18  n  r  25  Torque EMG activity Position  0  1  2  3  Time (sec)  Figure 4.3.2-3 Mild spasticity EMG activity correlated with position of test (50°/s)  It is clear that the reflex response of the involved muscles initiated as the rotation began, increased throughout the rotation, and slowly dissipated after the position remained constant at the end of the range taking roughly half a second. Figure 4.3.2-4 shows the same relationship, but of the subject with severe spasticity.  Torque EMG Activity Position  0  1  2  3  4  Time (sec)  Figure 4.3.2-4 Severe spasticity EMG activity correlated with position of test (50°/s)  81  Chapter 4: Data A n a l y s i s , Results and Discussion  In this case, a similar pattern of E M G is seen except that the E M G activity at the end of the velocity portion of the curve takes much longer to disperse. This accounts for the much higher peak torque values with respect to the steady state torque and the much slower decrease of the torque curve. In practical terms, this increase in reflex activity starting after the rotation begins and increasing as the rotation progresses is manifested as a more rapid increase in the velocity dependent torque curve and a very subtle exponential curvature at the very beginning of the resistive torque curve. One can speculate that the subject's intrinsic joint stiffness provides a relatively linear resistive torque to a passive movement similar to that of subjects without spasticity. Then if an increasing torque with position (such as the reflex response indicated by the E M G activity) is added to this linear curve, the result is increased torque and possibly some exponential curvature like that observed in the data from subjects with spasticity, more obvious in the data from the subjects with mild spasticity.  This may result from a slower, more  moderate reflex response in the cases of mild spasticity.  The velocity dependence of spasticity was investigated by comparing averaged torque data of different velocities against normalized time in a similar manner to that of the control data. A typical set of curves for one individual with spasticity, at velocities of 57s, 107s, 207s, 307s, 407s, 507s, and 607s is shown in Figure 4.3.2-5.  It is clear from these results that for up to 607s there is little or no velocity dependence of the spastic torque response to a passive rotation of the ankle. However, the black curve at 607s trends away from the rest of the group.  The velocity dependent portion of this curve is  significantly more non-linear than that of the rest of the group of curves.  This type of non-  82  Chapter 4: Data A n a l y s i s , Results and Discussion  linear response was rarely seen in subjects without spasticity but was noted as a characteristic of torque response due to spasticity.  This leads to the conclusion that the spasticity is more  pronounced at the 607s velocity. Given that this is the case, it suggests that there may be a velocity dependence to spasticity starting at or near 607s for subjects with spasticity.  Time (sec) Figure 4.3.2-5 Velocity dependence of spasticity  Although clonus was found in the subjects during clinical evaluation, the device never induced sustained clonus during testing. In part, this may be due to the method by which the subject's foot is rotated. In a clinical setting, the ball of the foot is grasped and is forced up as far as is 'reasonable' whereas the device simply rotates a flat foot plate about the subject's ankle joint while the subject's foot remains flat and evenly rotated. O n the other hand, in a clinical setting the foot would be bent and the point of contact is on the ball of the foot. In addition, in the clinical setting the range of motion can be more fully realized as the clinician has a better 'feel' for the range than the device does (the device w i l l always err on the side of caution for obvious  83  Chapter 4: Data A n a l y s i s , Results and Discussion  safety reasons). These differences between clinical testing and testing with the device may be responsible for the lack of clonus during testing. One of the subjects did, however, self induce clonus for the benefit of science. A graph of the self induced clonus is shown in Figure 4.3.2-6. In this case the subject's ankle and knee were at 9 0 ° and no movement of the device took place. The variation of the torque up to the point at which clonus began (approximately 1.4 seconds) was due to the subject's leg movement while trying to induce the clonus response.  6  n  Time (sec)  Figure 4.3.2-6 Self induced clonus  Two interesting observations were made regarding the clonus data.  First, the initial torque  before the clonus begins is approximately zero, but after the clonus is induced, the mean torque rises to approximately 5 N m and then fluctuates about the mean at approximately 10 Hz. Second, during the course of the clonus, the mean torque value slowly decreases although the  84  Chapter 4: Data A n a l y s i s , Results and Discussion  fluctuations remain relatively constant.  This pattern was repeated a number of times with  surprising repeatability.  The subject with severe spasticity suffered from a brain injury which had severely affected the subject's left side while the right side had only been mildly affected, but which suffered from spasms. The right leg was tested and some of the resulting data is shown in Figure 4.3.2-7.  0  1  2  3  Time (sec)  Figure 4.3.2-7 Spasms occurring during testing  Because of the spasms of the ankle joint it is difficult to compare the data from this leg to the side suffering from spasticity.  The spasms might be considered as a form of clonus because  they meet the most basic definition of clonus (i.e. muscle contractions elicited by a rapidly applied, but maintained stretch).  However, of more interest is the possible clasp knife  phenomenon in the curve where one of the curves abruptly drops off after a certain point.  85  Chapter 4: Data A n a l y s i s , Results and Discussion  After examining the data from both the control population and the group with spasticity, it is clear that there are a number of distinct differences which appear to be related to the degree of spasticity. A careful comparison between parameters related to these differences is required to clearly distinguish between the two groups. In order to do this, some means to mathematically represent the parameters related to spasticity, must be chosen to describe the curve.  This is  accomplished in Section 4.3.3.  4.3.3  Comparison of Data from Subjects With and Without Spasticity  T o establish this device as a clinical diagnostic tool, data needed to be compared between the groups of subjects with and without spasticity with respect to the variances between groups, and between degrees of spasticity. had to be determined.  T o accomplish this, parameters describing the variances  This was done by fitting a curve, based on the chosen model for  spasticity, through the resistive torque data at the various velocities. response  to a position input as a second order system,  describing the fitted curve.  B y modeling the torque  four parameters are obtained  In order to determine the four parameters which described the  curves, each curve was fitted to a second order differential equation of the form: (Transfer function of a second order system)  dT  dB  dt  dt  2  where  2  2  T is the output torque 0 is the input angle or position  86  Chapter 4: Data A n a l y s i s , Results and Discussion  t is time £ is the damping parameter which corresponds to the damping ratio co„ is the response parameter which corresponds to undamped natural frequency K is the gain parameter which corresponds to the steady state gain with respect to the input position V is the velocity dependent gain A is the acceleration dependent gain  A s the tests occurred at a constant velocity, the acceleration dependent gain, A , is assumed to be zero.  This equation left four parameters which (with the input and output curves known)  describes a curve which most closely fits the output curve (Torque vs. time). The input curve used was the position (ramp and hold curve) which allowed some significance to the gain parameter, K. Thus K relates the amount of torque output with respect to the angular rotation (range) of the test.  What is also of interest is the smooth transition between the increasing  torque and the steady state torque (described in part by the damping factor Q . A s well, the response parameter, co , describes the speed of response of the torque increase to the position n  input. Finally, the velocity dependent gain, V , is representative of the reflex response subject to a slight delay (ignored in this model), dependent on the velocity of the rotation. This parameter is of some significance with respect to the amount of overshoot  B y using this second order differential equation to model the resistive torque data, the four parameters can distinguish differences in the data that are not obvious to the human eye.  87  Chapter 4: Data A n a l y s i s , Results and Discussion  However, in order to determine values of the equation parameters, a curve needs to be fitted to the experimental data. This was done in the frequency domain where the equation takes the form:  T(s)  Vs+K(On  2  6 0)  s +2^co„5 + co 2  2 n  Using the dynamic model parameter identification in Matlab®, a least squares regression fit of the data was used to determine the equation parameters. The Matlab® code used to do this is shown in Appendix D . The parameters provide the relationship between the input position data and the output torque data. A sample of the averaged torque and position vs. time input data for analysis in M a t l a b ® is shown in Figure 4.3.3-1. The green curve represents the position input while the red curve is the torque output. The torque data within test sessions was averaged to provide more generally applicable results. 30 25 h  Position Input Torque  20 15 10 5 20  40  60  80  100  120  140  Figure 4.3.3-1 Data input to Matlab®  88  Chapter 4: Data A n a l y s i s , Results and Discussion  The Matlab® program provides a curve from the model which most closely fits the data. In general, fit of the equation curves to the experimental data was excellent. Figures 4.3.3-2 and 4.3.3-3 show typical fitted curves to data from subjects without and with spasticity respectively. In each case the green curve is the position input, the red curve is the torque output and the blue curve is the fitted curve based on the equation of the model. Fit of the two curves is so close that it is often difficult to distinguish them. 35 30  h  25 Position Input Torque Fitted Curve  20 15 10 5 h 0 -5  20  40  60  80  100  120  140  Figure 4.3.3-2 Typical equation curvefittedto resistive torque datafroma subject without spasticity (40°/s)  50 45 40 35 30 25 20 1 5 1 0 5 0  Position Input T o r q u e F itte d C u r v e  20  40  60  80  1 00  12 0  Figure 4.3.3-3 Typical equation curvefittedto resistive torque datafroma subject with spasticity (60°Is)  89  Chapter 4: Data A n a l y s i s , Results and Discussion  With curves fit to the data, the four parameters for each curve were evaluated. Parameters were determined for each velocity, for each individual, and for each test session.  The calculated  values of the model parameters are listed in Table 4.3.3-1. In the table co is linearized at 307s n  in order to compare the data at different velocities. This was done by varying the time constant of the equation fitting inversely proportionally to the velocity of the test.  A s a result, co is n  proportionally changed while the other parameters remain constant.  107s  207s  307s  CO  7.5  c  2.49  K  0.24  6.26 6.86 0.93 0.93 0.26 0.26 1.39 1.16  5.11 6.83 0.95 0.88 0.2 0.26 0.64 -0.42  5.81 6.11 0.95 0.87 0.57 0.54 1.32 1.24  6.19 6.05 0.88 0.99 0.54 0.57 -0.67 0.11  6.5  6.44 6.37 1.12 0.99 0.39 0.49 1.70 -0.63  407s  507s  607s  6.44  6.01  5.4  0.83  0.97  0.99  0.25  0.26  0.25  -0.70  -1.07  -1.37  5.57  5.83  5.35  0.82  0.86  1.02  0.53  0.57  0.53  0.67  -0.78  -1.28  5.61  4.84  . 5.23  0.97  0.96  0.83  0.49  0.49  0.48  -1.49  -1.34  -2.52  6.89 .  6.71  6.34  Control #]  V  1.72  Control #2 to  6.42  r  0.85  K  0.58  V  1.34  Control #3 CO  K V  9.24 1.21  1.15  0.39  0.41  1.58  1.86  Control #4[ CO  20.1 14.94  11.45 10.67  0.97 0.85  1.06 1.14  8.52 7.17 7.7 0.8 0.94  90  Chapter 4: Data A n a l y s i s , Results and Discussion  0.87  K  0.18  0.18  0.2  0.19  0.2  0.21 0.2  V  1.08  1.08  1.53  1.87  1.02  0.85  0.2  0.19  0.21  0.34  -0.03  -0.42  4.16  5.08  4.49  0.91  0.56  0.76  0.35  0.34  0.34  2.97  1.11  -1.78  0.59 1.11 0.86  M i l dCOspasticity #1  0.98  5.4  4.5  5.54  4.13  4.58  4.19 4.12  (right leg)  4.89  3.41  3.3  0.54  0.63  0.7  0.9  0.6  0.59 0.65  (right l e g )  0.75  K  0.99  0.78  0.33  0.33  0.34  0.34  0.57  0.57 0.57  (right l e g )  0.3.7  V (right leg)  0.61  M i l dCOSpasticity #2  0.37  0.37  1.51  2.09  0.99  -0.10  1.43  1.20  5.48  5.24  4.97  4.36  3.83  0.65  0.59  0.68  0.7  0.69  3.54 0.83  K  0.75  0.74  0.73  0.7  0.71  V  1.75  -0.28  -0.17  -3.27  -2.25  0.68 5.57  Severe Spasticity CO  3.47  2.27  1.86  1.54  N/A  2.21  N/A  0.64  N/A  12.38  N/A  1.67 1.85 1.48  2.67  2.4 2.18 2.4  K  0.67  0.48  0.44 0.47 0.41  V  7.96  14.97  13.38 11.30 12.46  Table 4.3.3-1 Equation parameters for each test subject at various velocities  91  Chapter 4: Data A n a l y s i s , Results and Discussion  B y examining the values of the parameters in Table 4.3.3-1, a number of trends in the data can be noted.  In particular, as the severity of spasticity increases, the response parameter, co , n  decreases while the damping parameter,  increases.  In practical terms, this means that the  curves tend to take longer to respond to the initial movement, have a smoother transition from the velocity curve to the holding curve, and take longer to return to the steady state gain. It also indicates that the curves tend to take longer to respond to the position input which would be manifested by more of an initial delay or a slower increase in the torque response.  This  behavior well describes the characteristics which were associated with the curves from subjects with spasticity.  The gain, K, along with the velocity gain, V, seem loosely related to the  degree of spasticity but are not reliable indicators. While the velocity gain is considerably higher in the test data from the subject with severe spasticity, it does not follow an obvious trend when employing the other data. A larger steady state gain, K, means a larger torque increase with respect to a smaller movement (i.e. it relates range with torque).  Gain has a  tendency to be slightly higher for subjects with spasticity but it is not conclusive. This trend is to be expected as, in general, we expect higher torques from a subject with spasticity for the same rotations.  The gain, K, is also largely dependent on the maximum range for the  subjects with spasticity which can vary day-to-day and with mood (either in an emotional context or in a physical sense as well). The range of gain for subjects without spasticity seems more constant. This variation in maximum range of the subjects with spasticity does not affect the other parameters (co„ and Q as much so they are more stable indicators of spasticity. The  92  Chapter 4: Data Analysis, Results and Discussion  observed trends in co„ and £ are also generally applicable to the control data and thus some combination of these two parameters may provide a useful indicator of spasticity.  B y plotting the two most reliable indicators (co and Q of spasticity against each other the n  following plot in Figure 4.3.3-4 is obtained for all velocities tested. Data from subjects with and without spasticity are plotted.  8 -j 76 5 * A  CO 4  AA  • Without Spasticity A Mild Spasticity • Severe Spasticity  A  A  3 2 1 0  —I  0.5  1.5  2.5  3  Figure 4.3.3-4 Response parameter versus damping parameter for all velocities tested  Although there is some overlap of the two parameters individually, when they are plotted together there is a clear difference between the data from subjects with and without spasticity. Given that the data from subjects with and without spasticity can clearly be distinguished from each other in this plane, some quantitative measure of the degree of spasticity can be estimated.  93  Chapter 4: Data A n a l y s i s , Results and Discussion  4.3.4  Quantification of Results  B y plotting the response parameter and the damping parameter together, the data from subjects with and without spasticity can clearly be distinguished. B y making use of this relationship, the degree of spasticity can be quantified. From Figure 4.3.3-4 it can be seen that the more severe cases of spasticity are also differentiated from the mild cases. This can be taken advantage of by delineating a curve between the two sets of data.  T o separate the data from subjects with and without spasticity, an equation was determined which describes a curve between the two sets of data. The distance of the data outside this curve, measured perpendicular to the curve, was used to determine a quantitative number related to the degree of spasticity.  Inside the curve, or on the curve, the data indicates no  evidence of spasticity. The equation determined below was arbitrarily chosen to have the best fit between the two sets of data:  co =  + 2.7  This equation was chosen, rather than a straight x" type equation, in an attempt to linearize the data from subjects with spasticity with respect to the degree of spasticity. Figure 4.3.4-1 shows the response parameter, co , versus damping parameter, £ , for all velocities tested separated n  by the delineating curve.  94  Chapter 4: Data Analysis, Results and Discussion  9 8 7 6 CO  • A  5 4  Subjects w/o Spasticity Subjects with Spasticity Separator curve  3H 2 1 0 0.5  Figure 4.3.4-1  2.5  1.5  Response parameter versus damping parameter for all velocities tested  separated by delineating curve  The points on the graph are then compared to the delineating equation to determine their perpendicular distance outside the curve. If they are inside, or on the curve they are assumed to be free of spasticity. T o determine i f the points are inside the curve or outside the curve each data point is simply inserted into the following equation of the curve:  VC " 0 . 7 3  + 2.7 - co = Solution  If the solution to the equation is zero or negative the test indicates non-spastic behavior. If the solution to the equation is positive or an error occurs  < 0.73) the test indicates evidence of  spasticity and the corresponding distance outside the curve must be determined to quantify the  95  Chapter 4: Data A n a l y s i s , Results and Discussion  degree of spasticity. The distance of any given point outside the curve can be determined by minimizing the square of the distance between the two points:  D-(x-C) +(y-co) 2  2  Where the equation is constrained by:  *  V* -  2  0.73 + 2.7  Then:  D(x) =  (x-0 +(  X  2  V* -  \  0.73  +2.7-C0)  2  To minimize this equation set:  dDjx)  dx  0  Using M a p l e ® (code shown in Appendix D) this function is minimized for any given value of co or C, to determine the value of x corresponding to the shortest distance from the curve to the data point. This value of x is then used to determine y which can be used to determine the distance equation, -JT5, to get the shortest distance to the curve. This value of the distance of the data point from the separator curve is then used as a quantified measure of spasticity. After analyzing all the data points, the degree of spasticity for each subject was tabulated in Table 4.3.4-1.  96  Chapter 4: Data A n a l y s i s , Results and Discussion  Calculated Spasticity Measurement Parameter {4D ) Subject  207s  307s  407s  507s  607s  Control Group  0  0  0  0  0  Mild spasticity #1  0.24  0.32  0.07  0.50  0.46  0.24  0.22  0.30  0.56  0.13  0.36  0.83  0.58 Mild spasticity #2  0.13  0.14  1.09 Severe spasticity  1.25  2.88  3.10  3.31  N/A  3.18 3.11 Table 4.3.4-1 Quantified measurements of spasticity for all subjects.  With the exception of the case of 'Mild Spasticity #1' it was noted that there did appear to be a clear velocity dependence of the quantified spasticity measure. A s the velocity of the rotation increases, so too does the quantified spasticity measure. In the case of ' M i l d Spasticity #1' the quantified spasticity measure increased from 207s to 307s and then remained relatively constant through 407s.  A t 507s and 607s the measure decreases with increasing velocity.  However, this observation results from only one testing session and may be attributed to experimental error. In the case of 'Mild Spasticity #2' the spasticity measure remains relatively constant up to test velocities of 407s, and above this test velocity it increases rapidly. It was observed that 'Severe Spasticity' showed a distinct trend of increasing quantified spasticity measure with increasing test velocity. Initially, from 207s to 307s the measure increases quite rapidly and then increases more slowly from 307s to 507s.  In each case the quantified  97  Chapter 4: Data A n a l y s i s , Results and Discussion  spasticity measure began increasing at different velocities and behaved slightly differently (increasing along different slopes, leveling off etc.).  It could be theorized that the differing  velocity dependence of each subject may be related to the associated disease.  The subject of  'Mild Spasticity #1' suffered from a stroke, the subject of ' M i l d Spasticity #2' had a spinal cord injury, and the subject of 'Severe spasticity' had a brain injury. It is possible that individuals with similar associated diseases might exhibit similar velocity dependence of the quantified spasticity measure.  In this case it is difficult to compare the results of each individual test  subject or to speculate on the relevance of the velocity dependence. Suffice to say, there does appear to be a velocity dependence and the quantified spasticity measure does correlate with increasing clinical degree of spasticity.  In order to have clinically validated results, the subjects should be tested for spasticity by an experienced physician using one of the commonly accepted techniques, such as the Ashworth scale. The subject designated 'Mild Spasticity #1' was clinically evaluated and was found to have mild spasticity which was slightly worse in the subject's left leg than the right.  The  subject with severe spasticity was also clinically evaluated, and was found to have an extremely severe spastic response in the subject's left leg, while the right leg was not as severe.  The  subject designated ' M i l d Spasticity #2' was not clinically evaluated in the course of this project, but was able to self induce persistent clonus consistent with the clinical confirmation of spasticity. In addition, this subject had been evaluated for spasticity prior to this project and reported having mild evidence of spasticity.  The quantified results of this research project  98  Chapter 4: Data A n a l y s i s , Results and Discussion  concur with the clinical evaluation of spasticity, although, at present, it is not clear exactly how the quantified measurement of spasticity will relate to clinical evaluations.  Although the delineation curve effectively separates all the data points at all velocities, it may be more practical to quantify the degree of spasticity using one standardized velocity, or to relate numbers from the same velocities.  In addition, the exact curve to separate data from  subjects with and without spasticity should be determined by statistical analysis of further test data from both groups.  A s more data for the control group (and subjects with spasticity of  varying degrees) is obtained this equation can be refined to provide a more  accurate  differentiation between subjects with and without spasticity.  4.4  Statistical Significance of the Test Results  B y comparing data sets within a test session, the covariance between the sets of data can be determined, indicating a measure of the relationship between the two ranges of data. If there is a weak relationship between the two sets of data, the covariance tends toward zero. Covariance of experimental data within test sessions for data from subjects with and without spasticity was calculated. The covariance between the sets of experimental data was found to be very good for both test groups. The values of covariance for subjects without spasticity ranged from a low of 6 to as high as 36, indicating good to excellent correlation. The covariance for the data from subjects with spasticity was slightly better.  99  Chapter 4: Data A n a l y s i s , Results and Discussion  It is impossible to obtain an accurate measure of the reliability of the test data on a day-to-day basis because of the limited day-to-day sampling during this project. In order to check the dayto-day reliability of the test data or the results, requires a larger sample of day-to-day tests. This was difficult to obtain because of the time constraints of the test subjects. It appears that dayto-day reliability was not as good as within testing sessions (test-to-test). This may be due, in part, to inconsistencies of the device.  A s well, testing took place over a period of several  months while the testing protocol was being continuously changed to optimize the testing procedure.  The analysis of variance test ( A N O V A ) , which expands on the test for two means, was used to evaluate the hypothesis that the two data sets, repeated over a number of months on a variety of subjects with, and without spasticity, are drawn from populations with the same mean. The specific test used was the two-factor A N O V A test with replication, meaning that more that one sample for each group of data (i.e. co and Q was included in the analysis. The results of the test demonstrated a significant difference between the two data sets. A N O V A between the data samples from subjects with and without spasticity for co and C, yields:  SS = 33.26 P = 0.078  This indicates that the probability that the two groups are from the same population samples is only 7.8%. This indicates that a reasonably reliable indicator for spasticity has been developed.  100  Chapter 4: Data A n a l y s i s , Results and Discussion  Although the quantified results of the testing did agree with the clinical measure of spasticity, further testing is needed to correlate it as a measure of the degree of spasticity.  In order to  determine the reliability of day-to-day tests, a larger population sample is required.  4.5  C o m p a r i s o n s w i t h Previous W o r k  Previous research has often attempted to quantify spasticity with varying degrees of success. The results have often been a single number related only to one parameter of spasticity such as peak torque of the test. In addition, the parameters chosen for measuring spasticity have only been questionably shown to relate to spasticity.  In this research, one of the most  common methods utilized to measure spasticity, the peak torque has been shown not to relate to spasticity at all. Another common measure of spasticity, reflex gain, is both difficult to determine and related more to other factors, such as the input position, rather than to spasticity. B y relating the torque response gain to the input position, as in this research, some loose correlation has been established between gain and spasticity. The measure developed by this project takes into account a variety of factors which were seen to be indicators of both the existence of spasticity, and the severity of spasticity. These factors were carefully chosen because of their relative robustness and clear correlation. Other loosely related factors, often chosen by other researchers, were ignored because of poor correlation or inconsistent results. B y carefully choosing the factors related to spasticity and its severity, and intelligently presenting this data, a single, relevant measure of spasticity has been developed.  101  Chapter 4: Data A n a l y s i s , Results and Discussion  4.6  Summary  Initially subjects without spasticity were tested to determine the behavior of the ankle joint. Resistive torque data from the tests were plotted against time. The curves exhibited a generally linear ramp of increasing torque in the velocity dependent portion of the test followed by a steady torque level after the motion had stopped. There was little or no E M G activity evident during the testing, indicating no reflex muscle activity.  Nor was there any obvious velocity  dependence up to 607s rotations of the ankle. This data was compared with data from people with spasticity. Subjects with spasticity were tested to assess variations in spastic response. The data was analyzed to determine variations between data of subjects with and without spasticity.  Noted variations included a smoother transition between increasing torque and  steady torque, an increasing torque curve which was slightly less linear, and an overshoot and subsequently decreasing resistive torque. These variations were confirmed, in an exaggerated form, in data from a subject with severe spasticity.  In addition, E M G activity was found to  have increased during the tests of the subjects with spasticity indicating active reflex response. It was also noted that there might be velocity dependence of spasticity starting at or about 607s.  A number of traditional measures for spasticity were investigated using the collected data. Maximum resistive torque, slope of the velocity dependent curve, reflex threshold, gain, and severity of E M G response were all considered. None of the traditional measures of spasticity was deemed suitable as a reliable measure of spasticity.  Instead an equation, based on the  chosen model for spasticity, was used to fit a curve to the resistive torque vs. time data. Parameters of this equation were correlated with the degree of spasticity. It was noted that, as  102  Chapter 4: Data A n a l y s i s , Results and Discussion  the severity of spasticity increased, the response parameter, co , decreased while the damping n  parameter, £, increased. These two parameters were plotted against each other and a delineating equation was drawn between the data from subjects with and without spasticity.  The  perpendicular distance of the data points from this delineating curve was used as a quantitative measure of spasticity.  This quantified measure of spasticity correlated with the clinical  evaluation of the subjects.  The A N O V A test was used to analyze the two sets of data and  showed that the probability that the two groups were from the same population was only 7.8%. This demonstrates that a reasonably reliable indicator for spasticity has been developed.  103  Chapter 5: Conclusion  and Recommendations  for Future Work  CHAPTER 5: CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK  5.1  Conclusions  The general purpose of this investigation, as mentioned in Chapter 1, was to develop an objective, quantitative means of measuring the degree of spasticity. T o this end, a number of objectives  were set for the development  and testing  stages of the project.  For the  development stage of the device the following objectives were met.  •  The short term objective to develop and validate a computer-controlled device to quantitatively measure the degree of spasticity at the ankle in a clinical application has been achieved.  •  This device performs the testing in a safe manner and has built in redundant safety features to protect the test subjects from any possible failure of the device. These safety features include torque limited computer control, a variable slippage clutch, physical stops for the foot pedal, and mechanical shear pins designed to shear at unsafe levels of torque.  •  This device was designed to be flexible enough to accommodate testing of various measurement protocols.  The displacement/velocity controlled rotation method was  104  Chapter 5: Conclusion and Recommendations for Future Work  chosen as the best method to measure spasticity and the device was able to accommodate this method of measurement. •  Although no test data was generated, during laboratory testing, the device was able to test subjects in different sitting positions with the subject's knee joint and ankle joint in a variety of positions.  In the course of this project subjects were seated with their knees  and ankle joints at 9 0 ° .  Throughout the testing phase of the research the following objectives were met:  •  The device was able to reliably measure the resistive torque at the ankle of individuals with and without spasticity.  •  Using data acquired using the device, a diagnostic model has been developed which indicates the ability to distinguish between joints with and without spasticity. This was done by parameterizing the chosen model and applying that model to the experimental data. The parameter data was examined for trends in spasticity and plotted accordingly. A separator equation between the two sets of data was used to quantify the results and clearly distinguished between the data sets.  •  The developed model, which utilizes resistive torque data, was able to distinguish between degrees of severity of spasticity for the tested subjects and provides a parameter to quantify degrees of spasticity severity.  B y determining the minimum distance of the  plotted spasticity parameters outside the separator curve, experimental data from the device was used to quantify different spasticity severity.  B y modifying the separator  105  Chapter 5: Conclusion and Recommendations for Future Work  equation one could attempt to linearize the quantified results with respect to clinical " scales. •  The device was able to record self induced clonus in one subject. Other phenomenon associated with spasticity such as spasms, and perhaps a clasp knife reaction, were also recorded.  •  O n a trial-by-trial basis, the repeatability of the device was excellent. Covariance values between 6 to as high as 50 were achieved between data from the same testing sessions.  •  Using the analysis of variance test in order to test the hypothesis that the control data and the data from subjects with spasticity were different, a value of the probability factor, P, was determined to be 0.078 indicating that the parameters separating the data sets were able to reasonably differentiated people with spasticity from people without spasticity.  5.2  Recommendations for F u t u r e W o r k  Throughout  the course  of this  research  project  improvements and future work became apparent.  a number of recommendations  for  These were related to both the use and  design of the device, and the confirmation of the testing protocol and analysis of the data.  •  Increased testing of both subjects without spasticity and, more specifically , subjects with spasticity should be undertaken in order to more accurately determine the limits of normal spasticity.  This additional data should be analyzed and plotted against the control data.  This would more accurately show the ranges of the model parameters for people with and without spasticity and would allow a more accurate delineation equation to be developed.  106  Chapter 5: Conclusion and Recommendations for Future Work  •  More testing  of subjects with spasticity,  correlated with clinical trials should be  performed to further refine the delineation equation. This data should be used to linearize the quantified data with clinical measures. •  Results should be correlated within disease groups (such as head and spinal cord injuries, stroke, multiple sclerosis, and cerebral palsy ) to determine if the model parameters are affected more by one disease group than another.  •  Results should be correlated against a variety of testing conditions to help understand how results are affected by uncontrolled factors (such as comfort, fatigue, mood, ambient temperature, and so forth).  •  A more accurate method for determining the maximum range of motion should be developed. This was found to be troublesome using the current protocol.  •  The testing  protocol should be made more rigorous to better control the  testing  environment and improve day-to-day variations of test data. •  The device should be made more concise to more exacting tolerances so that the quality of the device does not cause day-to-day variations of the data.  •  The stepper motor of the device is not strong enough to reliably test subjects above 507s. The motor should be replaced with a stronger motor. This is of some importance if the apparent velocity dependence of spasticity above 607s is to be investigated.  •  The data acquisition system is only capable of collecting data at 25 H z . This is mostly due to running the control software through M i c r o s o f t ® Windows. However, if the A D board were replaced with one with a buffer, the present system could be retained.  107  Chapter 5: Conclusion  and Recommendations  for Future Work  Movement of a joint is very important in the maintenance of that joint and, as mentioned in Chapter 1, the device has potential as an exercise device to help rehabilitate people with spasticity. This was not investigated during the course of this project, but would be of interest for further study. Theoretically, once a suitable evaluation of spasticity has been established, the device could be used to determine conditions under which a particular patient will be least affected by spasticity. There are instances where, under certain circumstances, spasticity is not apparent in the muscles of people with spasticity. In certain positions, at particular velocities, and through various paths, an individual might have their joints manipulated without a spastic response.  B y moving the ankle joint through various positions at varying velocities, while  recording the muscle activity, the conditions where movement occurs without a spastic response could be determined by the device. This information could then be programmed into the device so that those conditions could be reproduced as an exercise routine or stretching program to help rehabilitate an individual. There is also a possibility that by moving the joint without eliciting spasticity, the subject may learn to move in a like manner, without evoking a spastic response.  The device could be modified to accommodate a number of therapeutic and exercise applications. Some of the potential uses of the device as an exercise tool which would be of interest for further study are:  i)  Stretching of the ankle joint - The device could be modified to rotate a subject's ankle from one joint limit to the other for a given number of cycles (beginning and ending at  108  Chapter 5: Conclusion and Recommendations for Future Work  the ankle's neutral position) thereby stretching the spastic muscles.  Alternatively, the  ankle could be rotated from torque limit to torque limit.  ii)  Movement control exercise - B y setting the clutch resistance to a chosen level, a subject could attempt to move their ankle at a given velocity, over a given range, with a fixed resistance. The computer could use the data acquisition system to monitor the subject's response, so the subject could monitor their own progress in real time by matching it against the desired values displayed on the screen.  iii)  Torque control exercise - The motor could manipulate the subject's ankle through a chosen velocity profile for a number of cycles while the user attempts to match a given level of resistance.  The subject could monitor their progress in real time in a similar  manner as in (ii) above.  109  References  REFERENCES 1.  Lance, J . W . , "Pathophysiology of spasticity and clinical experience with Baclofen" In  Spasticity: Disordered motor control, Year Book Medical Publishers, Chicago, pp 185-203, 1980. 2.  Chapman, C . E . and Weisendanger, M . , "The physiological and anatomical basis of  spasticity: A review", Physiotherapy Canada 34:125-36, 1982. 3. Howe, T . , and Oldham, J., "Measuring muscle tone and movement", Nursing standard, 9:2529, 1995. 4.  Allison, S . C . , and Abraham, L . D . , "Correlation of quantitative measures  with the  Modified Ashworth Scale in the assesment of plantarflexor muscle spasticity in patients with traumatic brain injury", Journal of Neurology, 242:699-706, 1995. 5. Tiberio, D . , "Evaluation of functional ankle dorsiflexion using subtalar neutral position: A clinical report", Physiotherapy 67:955-957, 1987. 6.  Murray, M . P . "Gait as a total pattern of movement", American Journal of Physical  Medicine and Rehabilitation, 46:290-333, 1967. 7. Lucy, S.D. and Hayes, K . C . , "Postural sway profiles in normal subjects and subjects with cerebellar ataxia", Physiotherapy Canada 37:140-148, 1985. 8.  Law, M and Cadman, D . , "Measurement of Spasticity:  A Clinician's Guide", Physical  and Occupational Therapy in Pediatrics, 8(2/3):77-95, 1988 9.  Panizza, M . et al, "H-reflex recovery curve and reciprocal inhibition of H-reflex of the  upper limbs in patients with spasticity secondary to stroke", American Journal of Physical Medicine and Rehabilitation, 74:357-363, 1995. 10. Levin, M . F . and Hui-Chan, C . "Are H and stretch reflexes in hemiparesis reproducible and correlated with spasticity?", Journal of Neurology, 240:63-71, 1993. 11. Carr, J . H . , Shepard, R . B . , and A d a , L , "Spasticity: Research findings and implications for intervention", Physiotherapy, 81:421-429, 1995. 12. Meinders et al, "The stretch reflex response in the normal and spastic ankle: Effect of ankle position", Archives of Physical Medicine and Rehabilitation, 11:A%1-A92, 1996.  110  References  13. Neilson, P . D . , and McCaughey, J . , "Effect of contraction level and magnitude of stretch on tonic stretch reflex transmission characteristics", Journal of Neurology, Neurosurgery, and Psychiatry, 45:320-330, 1981. 14. Burke, D . , Gillies, J . , and Lance, J . , "The quadriceps stretch reflex in human spasticity", Journal of Neurology, Neurosurgery, and Psychiatry, 33:216-233, 1970. 15.  Burke, D . , Gillies, J . , and Lance, J . , "Hamstrings stretch reflex in human spasticity",  Journal of Neurology, Neurosurgery, and Psychiatry, 34:464-468, 1971. 16.  Katz, R . T . , and Rymer, W . Z . , "Spastic Hypertonia:  Mechanisms and Measurement",  Archives of Physical Medicine and Rehabilitation, 70:144-155, February 1989. 17.  Latash, M . L . , and Zatsiorsky, V . M . ,  "Joint stiffness:  M y t h or reality?", Human  Movement Science, 12:653-692, 1993. 18. Given, J.D., Dewald, J.P., and Rymer, W . Z . , "Joint dependent passive stiffness in paretic and contralateral limbs of spastic patients with hemiparetic stroke", Journal of Neurology, Neurosurgery, and Psychiatry, 59:271-279, 1995. 19. Sinkjasr, T . , and Toft, E . , and Andreassen, S., and Hornemann, B . 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Seib, T . P . , Price, R., Reyes, M . R . and Lehmann, J.F. "The Quantitative Measurement of Spasticity:  Effect of Cutaneous Electrical Stimulation.", Archives of Physical Medicine and  Rehabilitation, 75:746-750, 1994. 30. Price, R., Bjornson, K . F . , Lehmann, J.F., McLaughlin, J.F., and Hays, R . M . , "Quantitative Measurement of Spasticity in Children with Cerebral Palsy", Developmental Medicine and Child Neurology, 33:585-595, 1991. 31.  Casale, R., Glynn, J . , and Buonocore, M . , "Reduction of spastic hypertonia in patients  with spinal cord injury: A double-blind comparison in itraveneous orphenadrine citrate and placebo", Archives of Physical Medicine and Rehabilitation, 76:660-665, 1995. 32.  Ensberg, J.R., Olree, K . S . , Ross,  S . A . , and Park,  T . S . , "Quantitative  clinical  measurement of spasticity in children with cerebral palsy", Archives of Physical Medicine and Rehabilitation, 77:594-599, 1996. 33. Allison, S . C . , Abraham, L . D . and Peterson, C . L . , "Reliability of the Modified Ashworth Scale in the assesment of plantar flexor spasticity in patients with traumatic brain injury", International Journal of Rehabilitation Research, 19:67-78, 1996. 34. Hesse, S., et al, "Ankle muscle activity before and after botulinum toxin therapy for lower limb extensor spasticity in chronic hemiparetic patients", Stroke, 27:455-460, 1996. 35.  Ashworth, B . , "Preliminary trial of carisoprodal in multiple sclerosis.", Practitioner,  192:540-542, 1964. 36.  Bohannon, R . W . , and Smith, M . B . , "Interrater reliablity of a Modified Ashworth Scale  of muscle spasticity", Physical Therapy, 206-208, 1987. 37. Sloan, R . L . , Sinclair, E . , Thompson, J, Taylor, S., and Pentland, B . , "Inter-rater reliabilty of th eModified Ashworth Scale for spasticity in hemiplegic patients", International Journal of Rehabilitation Research, 15:158-161, 1992.  112  References  38. Hass, B . M . , Crow, J . L . , "Towards a clinical measurement of spasticity?", Physiotherapy, 81:474-479, 1995. 39.  Tepevac, D . , et al, "Microcomputer-based portable long-term spasticity recording  system", IEEE transactions on Biomedical Engineering, 39:426-431, 1992. 40.  Katz, R . T . , Rovai, G.P., Brait, C , and Rymer, W . Z . , "Objective Quantification of Spastic  Hypertonia:  Correlation With  Clinical  Findings", Archives of Physical Medicine and  Rehabilitation, 73:339-347, April 1992. 41.  Keenan, M . A . , Haider, T . T . , and Stone, L . R . , "Dynamic electromyography to assess  elbow spasticity", The Journal of Hand Surgery, 15A:607-614, 1990. 42.  L i n , J . , Brown, J . K . , and Brotherstone, R., "Assessment of Spasticity in Hemiplegic  Cerebral Palsy.  II:  Distal Lower-limb Reflex Excitability and Function.", Developmental  Medicine and Child Neurology, 36:290-303, 1994. 43.  Erfanian, A . , Chizeck, H.J., and Hashemi, R . M . , "The relationship between joint angle  and evoked  E M G in electrically  stimulated  muscle",  Proceedings of the  16th  IEEE  Conference of Engineering in Medicine and Biology , 345-346, 1994. 44.  Sherwood, A . M . , Priebe, M . M . , Markowski, J . , Kharas, N . F . , and Ambatipudi, R.,  "Assessment  of  spasticity  in  spinal  cord  injury:  A  comparison  of  clinical  and  neurophysiological measures", Proceedings of the 16th IEEE Conference of Engineering in Medicine and Biology , 462-463, 1994. 45. Bajd, T. and Bowman, B . , "Testing and Modeling of Spasticity", Journal of Biomedical Engineering, 4:90-96, 1982. 46 Bajd, T . et A L , "Pendulum Testing of Spasticity", Journal of Biomedical Engineering, 6:916, 1984. 47.  Bohannon, R . W . , "Variability and reliability of the pendulum test for spasticity using a  Cybex I I ® isokinetic dynamometer", Physical Therapy, 67:659-661, 1987. 48.  Salles, M . , and Mayagoitia, R . E . , "Instrumentation design to attempt standardization of  pendulum test", Proceedings of the 16th IEEE Conference of Engineering in Medicine and Biology ,930-931, 1994. 49.  Malouin, F . , Boiteau, M . , Bonneau, C , Pichard, L . , and Bravo, G . , "Use of a Hand-Held  Dynamometer for the Evaluation of Spasticity in a Clinical Setting:  A Reliability Study",  Physiotherapy Canada, 41:126-134, 1989.  113  References  50. Boiteau, M . , Malouin, F . , and Richards, C . L . , "Use of a hand-held dynamometer and a K i n C o m ® dynamometer for evaluating spastic hypertonia in children:  A reliability study",  Physical Therapy, 75:796-802, 1995. 51. Bohannon, R . W . , and Saunders, N . , "Hand-held dynamometery: A single trial may be adequate for measuring muscle strength in healthy individuals", Physiotherapy Canada, 42:6-9, 1990. 52.  Otis, J . C . , Root, L . , Pamilla, J.R., and Kroll, M . A . , "Biomechanical Measurement of  Spastic Plantarflexors", Developmental Medicine and Child Neurology., 25:60-66, 1983. 53. Chabal, C , Schwid, H . A . and Jacobson, L . , "The Dynamic Flexometer: A n Instrument for the Objective Evaluation of Spasticity.", Anesthesiology, 74:609-612, 1991. 54.  Firoozbakhsh, K . K . , Kunkel, C . F . , Scremin, E . and Moneim,  Dynamometric Technique for Spasticity  Assessment.",  M . S . , "Isokinetic  American Journal of Physical  Medicine and Rehabilitation^!'3:379-385, 1993. 55. Bohannon, R. and Larkin, P., "Cybex U ® Isokinetic Dynamometer for the Documentation of Spasticity. Suggestion from the Field", Physical Therapy, 65,: 1052-1054, 1985. 56. Broberg, C , and Grimby, G . , "Measurement of Torque During Passive and Active Ankle Movements in Patients with Muscle Hypertonia A Methodological Study", Scandinavian Journal of Rehabilitation Medicine,. 9:108-117, 1983. 57. Chen, W . , Pierson, F . M . , and Burnett, C . N . , "Force-time measurements of knee muscle functions of subjects with multiple sclerosis", Physical Therapy, 67,:934-490, 1987. 58.  Nistor, L . et A l . , "A Technique for Measurements of Plantar Flexion Torque with the  Cybex II Dynamometer", Scandinavian Journal of Rehabilitation Medicine, 14:163-166, 1982. 59. Rack, M . H . , Ross, H . F . , and Thilmann, A . F . , "The Ankle Stretch Reflexes in Normal and Spastic Subjects", Brain, 107:637-654, 1984. 60. Rebersek, S., Stefanovska, A . , and Vodovnik, L . , "Some Properties of Spastic Ankle Joint Muscles in Hemiplegia", Medical & Biological Engineering & Computing, 24:19-26, 1986. 61. Walsh, E . G . , "The Measurement of Muscle Tone", Paraplegia, 30:507-508, 1992. 62. Kearney, R . E . , and Stein, R.B., "Influence of perturbation properties on the identification of stretch reflexes at the human ankle joint", Proceedings of the 15th IEEE Conference of Engineering in Medicine and Biology, 1169-1170, 1993.  114  References  63. Stein, R . B . , and Kearney, R . E . , " A method for the evaluation of reflex contribution to ankle dynamics", Proceedings of the 13th IEEE Conference of Engineering in Medicine and Biology, 2022-2023, 1991. 64.  Chesworth, B . M . , and Vandervoort, A . A . , "Reliability of a Torque Motor System for  Measurement of Passive Ankle Joint Stiffness in Control Subjects", Physiotherapy Canada, 40:300-303, 1988. 65.  Harburn, K . L . , Hill, K . M , Vandervoort, A . A . , Helewa, A . , Goldsmith, C . H . , Kertesz, A . ,  and Teasell, R . W . , "Spasticity Measurements in Stroke: A Pilot Study", Canadian Journal of Public Health - Supplement 2, 83,:S41-S45, 1992. 66.  Sinkjaer, T . , Toft, E . , Larsen, K . , Andreassen, S., and Hansen, H . J . , "Non-Reflex and  Reflex Mediated Ankle Joint Stiffness in Multiple Sclerosis Patients with Spasticity", Muscle and Nerve, 16:69-76, 1993. 67.  Powers, R . K . , Campbell, D . L . , and Rymer, W . Z . , "Stretch Reflex Dynamics in Spastic  Elbow Flexor Muscles", Annals of Neurology, 25:32-42, 1989. 68.  Powers, R . K . , Marder-Meyer, J . , and Rymer, W . Z . , "Quantitative Relations Between  Hypertonia and Stretch Reflex Threshold in Spastic Hemiparesis", Annals of Neurology, 23:115-124, 1988 69. Walsh, E . G . , "A Review of Some Measurements of Muscle Wasting, Tone and Clonus in Paraplegia", Paraplegia, 31,:75-81, 1993. 70. Stein R . B . , and Kearney, R . E . , "Nonlinear behavior of stretch reflexes at the human ankle joint", Proceedings of the 15th IEEE Conference of Engineering in Medicine and Biology, 1167-1168, 1993. 71. Kirsch, R.F., Kearney, R . E . , and MacNeil, J.B., "Identification of time-varying dynamics of the human triceps surae stretch reflex", Experimental Brain Research, 97:115-138, 1992. 72. Stein R . B . , and Kearney, R . E . , "Nonlinear behavior of muscle reflexes at the human ankle joint", Journal of Neurophysiology, 73:65-72, 1995. 73. Ibrahim, I.K., Berger, W . , Trippel, M . , and Dietz, V . , "Stretch-induced electromyographic activity and torque in spastic elbow muscles", Brain, 116:971-989, 1993. 74.  Hershler, C , Colotta, I., and Romilly, D . P . , "Computer controlled measurement of  Spasticity", IEEE Conference on Computers & Technology, Vancouver, B . C . , 4pages, 1993. 75.  Juvinall, R . C . , "Fundamentals of Machine Component Design", John Wiley & Sons,  Inc., New York, 69-114, 1983.  115  References  76.  Spotts, M . F . , "Design of Machine Elements", Prentice-Hall, Inc., New Jersey, 148-210,  1985.  116  Appendix A - Design  Calculations  APPENDIX A - DESIGN CALCULATIONS  The prototype stepper motor was sized according to the following calculations.  Recall that  initially the maximum angular velocity of the ankle joint was to be 0.35 rad/s. The selected motor therefore had to provide at least T  m a x  = 24 N m at co  max  = 0.35 rad/s at the foot pedal in  order to overcome the resistive forces in the system. Assuming this angular velocity should be achieved in 0.05 s, then the maximum angular acceleration would be: a The inertia of the system (J  = co . / 0.05 s = 7.0 rad/s  2  ) is estimated to be 0.172 kgm at the foot pedal. Thus the torque 2  system  required to overcome the inertial forces in the system is: T.incrtial = Jsystem T  ,„cruai  = 0.172 kgm' * 7.0 rad/s = 1.2 N m  Thus the total torque required at the motor is:  Where e = efficiency of reducer = 0.50 n = gear ratio of worm gear = 30  T  motor  = (25.2 Nm)/(0.50*30) = 1.68 Nm  This torque had to be available with the motor running at: co. = motor  0.35 rad/s * 30 = 10.5 rad/s  117  Appendix A - Design  Minimum  specifications  calculations.  the  new  motor were determined  according to  the  Calculations  following  The minimum required torque at the foot pedal is 25 N m at 1.05 rad/s (607s).  Losses in the driveline are approximately 2 N m . . The new motor therefore had to provide at least T  =27 N m at to max  = 0.35 rad/s at the foot pedal in order to overcome the resistive forces  max  A  in the system. a  = c o / 0.05 s = 21.0 rad/s max  Tin^ai =  T  n e w m o t o r  2  max  0.172 kgm * 21.0 rad/s = 3.6 N m 2  = (30.6 Nm)/(0.50*30) = 2.04 N m  The transducer shaft was designed as follows. Using St. Venant's principle governing stresses, a transducer shaft 2-3 diameters long at a uniform thickness was selected to ensure reliable results from the strain gauges. The transducer shaft was constructed of 17-4 P H stainless steel. Two rosette strain gauges were acquired to measure the torque in the shaft connecting the drive system to the foot pedal. Each rosette consisted of three strain gauges but only the outer two were required for measuring torque.  The strain gauges were mounted exactly opposite each  other in the center of the transducer shaft to evaluate accurate torque measurements.  The strain  gauges were connected in a wheatstone bridge arrangement which limits the effects of lateral bending of the shaft.  Temperature effects should cancel out because of this, as well.  The  gauges were composed of Constantan foil of 0.125 in. thickness, mounted on a polyamide backing and were temperature compensated.  The output from the resistive bridge is given by the equation:  118  Appendix A - Design Calculations  V = e*2.04*n*E/4 b  Where: e = strain 2.04 = gauge factor n = number of active arms = 4 E = potential across input = 5 V  To design the shaft, the following analysis was done: Where: T  » 25 N m max  d; = inner diameter of shaft = 12.7 mm d = outer diameter of shaft o  J = moment of inertia G = Modulus of Rigidity = 75.5 G P a E„„ = maximum strain » 1500 mm/m  t  =T  max  d/J = G E max o  max  J = p(d 4-d,4)/32 o  Then: T  m a x  d /GE o  m a x  = pCd, - d )/32 i4  Solving for d » 15.2 mm o  And from St. Venant's principle, the length of the uniform section of the shaft was selected to be 50.8 mm.  119  Appendix B - Computer Code  APPENDIX B - COMPUTER CODE  The following is the main computer code used for control of the device to measure spasticity at the  ankle developed  for this project.  Professional Edition 3.0 application.  The code was  printed from a Visual  Basic  Some of the global declarations were removed for  space reasons.  MODULEl.BAS -1 'Prog2.MAK======================================== ' File: Prog2.MAK ' Purpose: Scans a range of A / D Input Channels and stores the sample data in an array. ' Other L i b r a r y C a l l s : cbErrHandling%()  Global Global Global Global Global  Const B o a r d N u m = 0 Const N u m P o i n t s & = 3 Const F i r s t P o i n t & = 0 ADData%(NumPoints&) MemHandle%  D i m F N a m e , M s g , TestString G l o b a l Offset@(3) G l o b a l selection A s Variant G l o b a l motor% Global U L i m i t A s Variant Global toggle% G l o b a l T o r L i m A s Variant Global M a x E M G A s Variant  ' ' ' ' ' ' ' '  1  Board number Number of data points to collect set first element in buffer to transfer to array dimension an array to hold the input values define a variable to contain the handle for memory allocated by W i n d o w s through c b W i n B u f A l l o c % ( ) Declare variables. Calibration constant array to zero each channel  Safe Torque limit  Sub W a i t () N =0 Screen.MousePointer = 11 D o W h i l e N < 14000 N =N+1 Loop Screen.MousePointer = 0 N= 1 E n d Sub  120  Appendix B - Computer  Sub OpenData () ' Open data files: Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & Open "c \data\" & End Sub  FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt FileTxt  Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text  & & & & & & & & & & & & & & & & & &  Code  "Op.dat" F o r Output A s #1 ' A n g u l a r position data "Ot.dat" F o r Output A s #2 ' Resistive torque data "Oe.dat" F o r Output A s #3 ' E M G activity data "lp.dat" F o r Output A s #4 ' A n g u l a r position data "lt.dat" F o r Output A s #5 ' Resistive torque data "le.dat" F o r Output A s #6 ' E M G activity data "2p.dat" F o r Output A s #7 ' A n g u l a r position data "2t.dat" F o r Output A s #8 ' Resistive torque data "2e.dat" F o r Output A s #9 ' E M G activity data "3p.dat" F o r Output A s #10 ' A n g u l a r position data "3t.dat" F o r Output A s #11 ' Resistive torque data "3e.dat" F o r Output A s #12 ' E M G activity data "4p.dat" F o r Output A s #13 ' A n g u l a r position data "4t.dat" F o r Output A s #14 ' Resistive torque data "4e.dat" F o r Output A s #15 ' E M G activity data "5p.dat" F o r Output A s #16 ' A n g u l a r position data "5t.dat" F o r Output A s #17 ' Resistive torque data "5e.dat" F o r Output As#18 ' E M G activity data  Sub GetData () Collect the values with cbAInScan%() Parameters: BoardNum :the number used by C B . C F G to describe this board LowChan% :the first channel o f the scan H i g h C h a n % :the last channel of the scan C B C o u n t & :the total number o f A / D samples to collect CBRate& :sample rate Gain% :the gain for the board Addata% :the array for the collected data values Options% :data collection options LowChan% = 0 ' first channel to acquire HighChan% = 2 ' last channel to acquire CBCount& = NumPoints& ' total number of data points to collect C B R a t e & = 2000 ' sampling rate (samples per second) Options% = N O C O N V E R T D A T A Gain% = BIP5VOLTS ' set the gain If M e m H a n d l e % = 0 Then Stop ' check that a handle to a memory buffer exists ULStat% = cbAInScan%(BoardNum%, LowChan%, HighChan%, CBCount&, M e m H a n d l e % , Options%) If U L S t a t % = 84 Then  CBRate&,  Gain%,  M s g B o x "The C O N V E R T option cannot be used with 16 bit convenors. Set Options% to NOCONVERTDATA." Stop 'Change Options% above to N O C O N V E R T D A T A (Options%= 0) E n d If If U L S t a t % <> 0 Then Stop ' Transfer the data from the memory buffer set up by W i n d o w s to an array for use by V i s u a l Basic U L S t a t % = c b W i n B u f T o A r r a y % ( M e m H a n d l e % , A D D a t a % ( 0 ) , FirstPoint&, C B C o u n t & ) If U L S t a t % <> 0 Then Stop For 1% = 0 T o N u m P o i n t s & - 1 If A D D a t a % ( I % ) >= 0 Then A D D a t a % ( I % ) = A D D a t a % ( I % ) - 32768  121  Else A D D a t a % ( I % ) = A D D a t a % ( I % ) + 32768 E n d If 'Store the data to a 2 dimensional array in memory: D a t a A r r a y @ ( I % , temp) = A D D a t a % ( I % ) Next 1% E n d Sub DAS8.BAS - 1 ' ' ' '  This file contains the V i s u a l B A S I C declarations for all Computer Boards library commands. This file should be imported v i a V i s u a l B A S I C ' S L o a d Text command (from the code menu). It should be imported into either a form or the G l o b a l section o f the program.  FRMEMG.FRM - 1 D i m temp Dim MaxVal@ Sub C m n d C a n c e l _ C l i c k () TmrEMG.Enabled = 0 Unload F r m E M G E n d Sub Sub C m n d O K _ C l i c k () M a x E M G = T e x t l .Text Form2.Show Unload F r m E M G E n d Sub Sub C m n d S t a r t _ C l i c k () CmndCancel.SetFocus RunTotal@ = 0 T m r E M G . E n a b l e d = True E n d Sub Sub F o r m _ L o a d () MaxVal@  =0  temp = 0 E n d Sub Sub F o r m _ U n l o a d (Cancel A s Integer) Forml.CmndClose.Enabled = 1 F o r m l . C m n d D A . Enabled = 1 Form l.CmndProg.Enabled = 1 Forml.CmndLim.Enabled = 1 E n d Sub Sub T e x t l _ C h a n g e () Textl.BackColor = & H F F F F F F M a x E M G = T e x t l . Text E n d Sub  Sub T e x t l _ G o t F o c u s () T e x t l . T e x t = "" E n d Sub Sub T e x t l _ K e y P r e s s ( K e y A s c i i A s Integer) If K e y A s c i i = 1 3 Then M a x E M G = Textl.Text Form2.Show Unload F r m E M G E n d If E n d Sub Sub T m r E M G _ T i m e r () O n Error Resume N e x t C a l l GetData Limdata@ = ADData%(0) - Offset®(2) L i m d a t a ® = Abs(Limdata@) Limdata@ = L i m d a t a ® + R u n T o t a l ® RunTotal® = Limdata® T e x t l . T e x t = Format$(Limdata@, "0.0") If temp >= 100 Then M a x E M G = L i m d a t a ® / temp T e x t l . T e x t = F o r m a t $ ( M a x E M G , "0.0") T m r E M G . E n a b l e d = False temp = 0 E n d If temp = temp + 1 E n d Sub FRMFILES.FRM - 1 Sub C m n d C a n c e l _ C l i c k () Unload FrmFileSave E n d Sub Sub C m n d O K _ C l i c k () O n Error Resume N e x t C a l l OpenData frmDataDisplay.Show Unload FrmFileSave E n d Sub Sub F i l e T x t _ K e y P r e s s ( K e y A s c i i A s Integer) If K e y A s c i i = 13 Then C a l l OpenData frmDataDisplay.Show Unload FrmFileSave E n d Sub Sub L a b e l 2 _ C l i c k () toggle% = 1 E n d Sub PROG.FRM - 1 D i m temp  Dim total©(3) D i m D a t a A r r a y @ ( 3 , 51) D i m run A s Variant Sub C m n d C l o s e _ C l i c k () C o m m l . Enable = 0 CmndClose.Enabled = 0 CmndLim.Enabled = 0 Cmndlnit.Enabled = 1  Array to hold data for calibration  Disable port ' Enable Initialize and ' E x i t buttons  CmndExit.Enabled = 1 CmndTest.Enabled = 0 CmndStart.Enabled = 0 CmndDA.Enabled = 0 CmndProg.Enabled = 0 C m n d E x i t . SetFocus E n d Sub Sub C m n d D A _ C l i c k () FrmFileSave.Show CmndLim.Enabled = 0 CmndDA.Enabled = 0 CmndProg.Enabled = 0 E n d Sub Sub C m n d E x i t _ C l i c k () End E n d Sub Sub C m n d I n i t _ C l i c k () Cmndlnit.Enabled = 0 F o r m 1.Comml.Parity = 0 F o r m 1. C o m m l . Comport = 1 F o r m l . C o m m l . Baud = 3 F o r m l . C o m m l . Stop = 0 F o r m 1.Comml.Enable = 1 If C o m m l . E n a b l e = 0 Then E x i t Sub Picture 1 .Cls  ' If not enabled, exit ' Clear the picture  'Zero the data channels: Screen.MousePointer = 11 tmrConvert.Enabled = True E n d Sub Sub C m n d L i m _ C l i c k () CmndLim.Enabled = 0 CmndDA.Enabled = 0 CmndProg.Enabled = 0 FrmEMG.Show E n d Sub Sub C m n d P r o g _ C l i c k () If C o m m l .Enable = 0 Then Cmndlnit.Enabled = 1 CmndExit.Enabled = 1 CmndProg.Enabled = 0 E x i t Sub  ' If not enabled... ' Enable Initialize and ' E x i t buttons and exit  E n d If CmndClose.Enabled = 1 ' Determine the extent of programming in the device ' already. W e must assume that the users knows what they are doing. ' In this case we might be able to inform them (warning box) ' and warn them at what point they could safely start ' programming again. Title - "Entering Programming M o d e " M s g = "Programming may render device inactive!" + Chr(13) + C h r ( l O ) M s g = M s g & " D o you want to continue?" Beep response = M s g B o x ( M s g , 3 + 48, Title) If response <> 6 Then E x i t Sub CmndLim.Enabled = 0 CmndProg.Enabled = 0 CmndDA.Enabled = 0 Form4.Show E n d Sub Sub C m n d S t a r t _ C l i c k () motor% = 1 FrmFileSave.Show E n d Sub Sub C m n d T e s t _ C l i c k () CmndLim.Enabled = 0 CmndProg.Enabled = 0 CmndDA.Enabled = 0 Form3.Show 1 E n d Sub Sub C o m m l _ I n Q u e u e (Queued A s Integer) s$ = C o m m l . D a t a S t r ' Put characters in a string Picturel.Print s$; ' Print the string to picture E n d Sub Sub F o r m _ L o a d () temp = 0 motor% = 0 toggle% = 0 ' Initiate error handling ' activating error handling w i l l trap errors like  ' ' ' ' ' '  ' bad channel numbers and non-configured conditions. ' Parameters: PRINTALL :all warnings and errors encountered w i l l be printed DONTSTOP : i f an error is encountered, the program w i l l not stop, errors must be handled locally ULStat% = cbErrHandling%(PRINTALL, D O N T S T O P ) If U L S t a t % <> 0 Then Stop If c b E r r H a n d l i n g % is set for S T O P A L L or S T O P F A T A L during the program design stage, V i s u a l B a s i c w i l l be unloaded when an error is encountered. Suggest trapping errors locally until the program is ready for c o m p i l i n g to avoid losing unsaved data during program design. This can be done by setting c b E r r H a n d l i n g options as above and checking the value of U L S t a t % after a call to the library. If it is not equal to 0, an error has occurred.  Appendix B - Computer  MemHandle% = cbWinBufAlloc%(NumPoints&) If M e m H a n d l e % = 0 Then Stop E n d Sub Sub F o r m _ U n l o a d (Cancel A s Integer) ULStat% = cbWinBufFree%(MemHandle%) If U L S t a t % <> 0 Then Stop Unload Form2 Unload Form3 Unload Form4 U n l o a d frmDataDisplay E n d Sub  Code  ' set aside memory to hold data  ' Free up memory for use by other programs  Sub L a b e l l _ C l i c k (Index A s Integer) I f L a b e l l ( l ) = "" Then ForI% = 0 T o 2 L a b e l l ( I % ) = Offset(I%) Next Else ForI% = 0 T o 2 Label 1(1%) = "" Next E n d If E n d Sub Sub tmrConvert_Timer () O n Error Resume N e x t CallGetData If temp >= 50 Then tmrConvert.Enabled = False For J % = 0 To NumPoints& - 1 total(J%) = 0 Next J % For 1% = 1 T o temp - 1 total @(0) = total @(0) + D a t a A r r a y @ ( 0 , 1 % ) t o t a l @ ( l ) = total @(1) + D a t a A r r a y @ ( l , 1%) total©(2) = total®(2) + DataArray@(2,1%> N e x t 1% Offset@(0) = total@(0) / (temp - 1) O f f s e t @ ( l ) = t o t a l @ ( l ) / (temp - 1) Offset@(2) = t o t a l ® ( 2 ) / (temp - 1) Screen.MousePointer = 0 CmndLim.Enabled = 1 ' Enable B e g i n button CmndClose.Enabled = 1 CmndExit.Enabled = 0 CmndTest.Enabled = 0 CmndProg.Enabled = 1 CmndDA.Enabled = 1 C o m m l . D a t a S t r = " " + Chr$(10) + Chr$(13) ' Send A T Z to modem CmndLim.SetFocus temp = 0 E n d If temp = temp + 1 E n d Sub  126  Sub TmrStart_Timer () CmndStart.SetFocus TmrStart.Enabled = 0 E n d Sub Dim Dim Dim Dim Dim Dim  Calim@(2) P l i m A s Variant N l i m A s Variant Torque® LimData® temp3  ' Calibation constant  Sub C m n d A b o r t _ C l i c k () F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) Plim = 0 TmrPos.Enabled = False TmrNeg.Enabled = False CmndStop.Enabled = 0 CmndQuit.Enabled = 1 CmndPos.Enabled = 1 'CmndNeg.Enabled =1* End Sub Sub C m n d N e g _ C l i c k () CmndQuit.Enabled = 0 CmndAbort.Enabled = 1 CmndPos.Enabled = 0 CmndNeg.Enabled = 0 Torque® = 0 temp3 = 0 Nlim = 0 TmrNeg.Enabled = True E n d Sub Sub C m n d P o s _ C l i c k () Text2.BackColor = & H F F F F F F CmndQuit.Enabled = 0 CmndAbort.Enabled = 1 CmndStop.Enabled = 1 CmndPos.Enabled = 0 CmndNeg.Enabled = 0 CmndStop.SetFocus Torque® = 0 temp3 = 0 Plim = 0 TmrPos.Enabled = True End Sub Sub C m n d Q u i t _ C l i c k () Unload Form2 E n d Sub Sub C m n d S t o p _ C l i c k () F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) ULimit = Plim  Appendix B - Computer Code  TmrPos.Enabled = False TmrNeg.Enabled = False CmndStop .Enabled = False CmndQuit.Enabled = 1 CmndPos.Enabled = 1 CmndQuit. SetFocus T m r H o l d . Enabled = True E n d Sub Sub F o r m _ L o a d () C m n d A b o r t . C a n c e l = True T o r L i m = 35 ULimit = 0 Calim(O) = .0063 ' Calibration multiplyer for angular position C a l i m ( l ) = .00080826 ' Calibration multiplier for resistive torque F o r m l . C o m m l . D a t a S t r = "\20" + Chr$(10) + Chr$(13) Call Wait F o r m l . C o m m l . D a t a S t r = " V 1 0 0 0 " + Chr$(10) + Chr$(13) Call Wait F o r m l . C o m m l . D a t a S t r = "m3" + Chr$(10) + Chr$(13) Call Wait F o r m l . C o m m l . D a t a S t r = "f300" + Chr$(10) + Chr$(13) E n d Sub Sub F o r m _ U n l o a d (Cancel A s Integer) O n Error Resume N e x t ' M a k e sure timers are off: TmrNeg.Enabled = False TmrPos.Enabled = False T m r H o l d . E n a b l e d = False Forml.CmndClose.Enabled = 1 Forml.CmndDA.Enabled = 1 Form l.CmndProg.Enabled = 1 F o r m l . C m n d L i m . Enabled = 1 If U L i m i t Then U L i m i t = F i x ( U L i m i t * 1) ' F i x the testing extents to X X % of the comfort limits Forml.CmndTest.Enabled = 1 F o r m l .CmndTest.SetFocus E n d If If F o r m l . C m n d T e s t . E n a b l e d Then Forml.CmndTest.SetFocus E n d Sub Sub T e x t l _ C h a n g e () T o r L i m = Text 1.Text E n d Sub Sub T e x t l _ K e y P r e s s ( K e y A s c i i A s Integer) If K e y A s c i i = 13 Then CmndPos.SetFocus E n d If E n d Sub Sub Text2_Change () Text2.BackColor = & H F F F F F F U L i m i t = Text2.Text  128  E n d Sub Sub Text2_GotFocus () T e x t 2 . T e x t = "" E n d Sub Sub Text2_KeyPress ( K e y A s c i i A s Integer) If K e y A s c i i = 13 Then Unload Form2 E n d If E n d Sub Sub T m r H o l d _ T i m e r () F o r m l . C o m m l . D a t a S t r = "-" + P l i m + Chr$(10) + Chr$(13) CmndQuit.Enabled = 1 CmndAbort.Enabled = 0 CmndPos.Enabled = 1 'CmndNeg.enabled = 1 TmrHold.Enabled = 0 E n d Sub Sub T m r N e g _ T i m e r () O n Error Resume N e x t ' M o v e motor approximately one third o f a degree (11 steps): F o r m 1 .Picture 1 .Cls F o r m l . C o m m l . D a t a S t r = "-11" + Chr$(10) + Chr$(13) ' Collect and compare data: C a l l GetData If - T o r q u e © >= T o r L i m Then TmrNeg.Enabled = False T m r H o l d . E n a b l e d = True E n d If N l i m = N l i m + 11 E n d Sub Sub T m r P o s _ T i m e r () O n Error Resume N e x t ' M o v e motor approximately one third of a degree (11 steps): F o r m l .Picture 1 .Cls F o r m l . C o m m l . D a t a S t r = "+11" + Chr$(10) + Chr$(13) P l i m = P l i m + 11 ' C o l l e c t and compare data: C a l l GetData If T o r q u e © >= T o r L i m Then TmrPos.Enabled = False T m r H o l d . E n a b l e d = True ULimit = Plim E n d If E n d Sub Sub C m n d C a n c e l _ C l i c k () Unload Form3 E n d Sub Sub C m n d O K _ C l i c k ()  Appendix B - Computer Code  On Error Resume Next If Optionl(0).Value <> 0 Then selection = 0 If Optionl(l).Value <> 0 Then selection = 1 If Optionl(2).Value <> 0 Then selection = 2 If Optionl(3).Value <> 0 Then selection = 3 If Option 1(4).Value <> 0 Then selection = 4 If Option 1(5).Value <> 0 Then selection = 5 If Optionl(6).Value <> 0 Then selection = 6 Forml.CmndStart.Enabled = True Unload Form3 End Sub Sub Form_Load () CmndCancel.Cancel = True End Sub Sub Form_Unload (Cancel As Integer) Forml.CmndLim.Enabled = 1 Forml.CmndProg.Enabled = 1 Forml.CmndDA.Enabled = 1 Form 1 .TmrStart.Enabled = 1 End Sub Sub Command l_Click () Forml. Picturel. Cls Forml.Comml.DataStr = Textl.Text + Chr$(10) + Chr$(13) Text 1.Text = "" End Sub Sub Command2_Click () Unload Form4 End Sub Sub Command3_Click () Forml.Comml.DataStr = Chr$(27) + Chr$(10) + Chr$(13) Textl.SetFocus End Sub Sub Form_Unload (cancel As Integer) Command3. cancel = True Forml.CmndClose.Enabled - 1 Forml.CmndProg.Enabled = 1 Forml.CmndLim.Enabled = 1 Forml.CmndDA.Enabled = 1 Forml.Cmndlnit.Enabled = 0 Forml.CmndExit.Enabled = 0 End Sub DimDataCal@(3, 1000) Dim Dta@ Dim temp2 Dim Calib@(3) Dim N As Variant Dim TestVel%(5) Dim UnifVel%(5)  ' Calibrated data array ' Data calibrated with zeroing constant ' Calibration Constant  130  Appendix B - Computer Code  Dim Dim Dim Dim Dim Dim Dim  NorVel%(5) HiVel%(5) LoVel%(5) LoVel2%(5) LoVel3%(5) LoVel4%(5) ADLimit%(5)  Sub C m n d A b o r t _ C l i c k () F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) TmrData.Enabled = False CmndAbort.Enabled = False CmndStop.Caption = "Pause A / D " CmndStop.Enabled = False CmndStart.Enabled = True CmndQuit.Enabled = True E n d Sub Sub C m n d Q u i t _ C l i c k () U n l o a d frmDataDisplay E n d Sub Sub C m n d S t a r t _ C l i c k () On Error Resume N e x t temp2 = 0 CmndStop.Enabled = True CmndQuit.Enabled = False CmndAbort.Enabled = True CmndAbort.SetFocus CmndStart.Enabled = False L a b e l 1.Caption = " Test #" + N + " in progress" Label l.BackColor = &H80000005 TmrData.Interval = 100 If motor% Then* TmrData.Interval = 40 F o r m l . C o m m l . D a t a S t r = "e7" + Chr$(10) + Chr$(13) Call Wait F o r m l . C o m m l . D a t a S t r = "v" + C S t r ( T e s t V e l % ( N - 1)) + Chr$(10) + Chr$(13) Call Wait F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) Call Wait Call Wait F o r m l . C o m m l . D a t a S t r = "gO" + Chr$(10) + Chr$(13) E n d If TmrWait.Enabled = True E n d Sub Sub C m n d S t o p _ C l i c k () If TmrData.Enabled Then CmndStop.Caption = "Restart" TmrData.Enabled = False Else CmndStop.Caption = "Pause D / A " TmrData.Enabled = True E n d If  131  E n d Sub Sub F o r m _ L o a d () O n Error Resume N e x t C m n d A b o r t . C a n c e l = True C a l i b @ ( 0 ) = .0062 ' Calibration multiplyer for angular position C a l i b @ ( l ) = .0015857 ' Calibration multiplier for resistive torque Calib@(2)= 1 N= 1 For n = 0 to 5 U n i f V e l % ( n ) = 990 N o r V e l % ( n ) = 330 H i V e l % ( n ) = 660 L o V e l % ( n ) = 165 LoVel2%(n) =1320 L o V e l 3 % ( n ) = 1650 L o V e l 4 % ( n ) = 1980 Next n Select Case selection CaseO For 1% = 0 T o 5 TestVel%(I%) = L o V e l % ( I % ) N e x t 1% Case 1 F o r 1% = 0 T o 5 TestVel%(I%) = N o r V e l % ( I % ) Next 1% Case 2 F o r 1% = 0 T o 5 TestVel%(I%) = H i V e l % ( I % ) N e x t 1% Case 3 For 1% = 0 T o 5 TestVel%(I%) = U n i f V e l % ( I % ) N e x t 1% Case 4 F o r 1% = 0 T o 5 TestVel%(I%) = L o V e l 2 % ( I % ) N e x t 1% Case 5 For 1% = 0 T o 5 TestVel%(I%) = L o V e l 3 % ( I % ) N e x t 1% Case 6 F o r 1% = 0 T o 5 TestVel%(I%) = L o V e l 4 % ( I % ) N e x t 1% E n d Select If toggle% Then For 1% = 0 T o 5 A D L i m i t % ( I % ) = ( U L i m i t / TestVel%(I%) + 20.5) * 25 N e x t 1% Else For 1% = 0 T o 5 A D L i m i t % ( I % ) = ( U L i m i t / TestVel%(I%) + 4.5) * 25  Next 1% E n d If If (motor% = 0) Then For 1% = 0 T o 5 A D L i m i t % ( I % ) = 100 Next 1% E n d If Forml.Comml.DataStr Call Wait Forml.Comml.DataStr Call Wait Forml.Comml.DataStr Call Wait Forml.Comml.DataStr Call Wait Forml.Comml.DataStr Call Wait  = " e l 3 " + Chr$(10) + Chr$(13) = "+" + U L i m i t + Chr$(10) + Chr$(13) = Chr$(27) + Chr$(10) + Chr$(13) = "e22" + Chr$(10) + Chr$(13) = "-" + U L i m i t + Chr$(10) + Chr$(13)  F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) E n d Sub Sub F o r m _ U n l o a d (Cancel A s Integer) motor% = 0 Form l.CmndClose.Enabled = 1 Forml.CmndDA.Enabled = 1 Form l.CmndProg.Enabled = 1 Form l.CmndLim.Enabled = 1 Forml.CmndClose.SetFocus Close 'Close all files E n d Sub Sub TmrData_Timer () O n Error Resume N e x t If temp2 < A D L i m i t % ( N - 1) Then temp2 = temp2 + 1 C a l l GetData For 1% = 0 T o N u m P o i n t s & - 1 D t a @ = A D D a t a % ( I % ) - O f f s e t ® (1%) ' M u l t i l p l y Data by calibration constant: Dta@ = Dta@ * Calib@(I%) If motor% A n d 1% = 1 Then If D t a @ >= T o r L i m Then F o r m l . C o m m l . D a t a S t r = Chr$(27) + Chr$(10) + Chr$(13) TmrData.Enabled = False C m n d A b o r t . E n a b l e d = False CmndStop.Caption = "Pause A / D " CmndStop.Enabled = False CmndStart.Enabled = True CmndQuit.Enabled = True E n d If E n d If ' Store the data to a 2 dimensional array in memory: D a t a C a l @ ( I % , temp2) = D t a @ ' Print data to screeen: If N o t motor% Then  Appendix B - Computer  Code  l b l A D D a t a ( I % ) . C a p t i o n = Format$(Dta@, "0.00") E n d If Next 1% Else ' Process E M G data and store the test data: For 1% = 0 T o 2 Print #(I% + N + 2 * ( N - 1)), "Range is: " + U l i m i t + " steps" Print #(I% + N + 2 * ( N - 1)), " M a x E M G is: " + M a x E M G Next 1% average® = 0 For J% = 0 T o (temp2 - 1) a v e r a g e ® = a v e r a g e ® + D a t a C a l @ ( 2 , J%) N e x t J% a v e r a g e ® = a v e r a g e ® / temp2 For 1% = 0 T o N u m P o i n t s & - 1 For J% = 0 T o (temp2 - 1) IfI% = 2Then DataCal@(2, J%) = D a t a C a l @ ( 2 , J%) - a v e r a g e ® D a t a C a l @ ( 2 , J%) = A b s ( D a t a C a l @ ( 2 , J%)) D a t a C a l @ ( 2 , J%) = DataCal@(2, J%) / M a x E M G E n d If Print #(I% + N + 2 * ( N - 1)), D a t a C a l @ ( I % , J%) N e x t J% Next 1% temp2 = 0 TmrData.Enabled = False CmndStop.Enabled = False CmndQuit.Enabled = True CmndAbort.Enabled = True TmrReturn.Enabled = True Label 1.Caption = " Press 'Start' to begin data collection" Label 1 . B a c k C o l o r = & H F F F F & If motor% Then N = N+ 1 If N > 6 Then Label 1.Caption = "" N = 6 Else I f N = 6Then CmndQuit.SetFocus CmndStart.Enabled = 0 N= 1 E n d If L a b e l 1.Caption = " Test velocity #" + N + " Press 'Start' to continue" E n d If E n d If E n d If End Sub Sub TmrReturn_Timer () CmndStart.Enabled = True CmndStart.SetFocus TmrReturn.Enabled = False E n d Sub  134  Appendix B - Computer Code  Sub T m r W a i t _ T i m e r () TmrData.Enabled = True TmrWait.Enabled = False E n d Sub  135  Appendix C - Ethics Review  Information  Page 1 of 2  SPASTICITY M E A S U R E M E N T S T U D Y Principal Investigator: Dr. Cecil Hershler  I agree to participate in a study which is designed to test a machine to measure spasticity. At present spasticity is commonly measured manually which provides only qualitative information and which makes it difficult to record small changes. If we can measure spasticity more effectively we will have a better method for evaluating treatment and intervention for patients suffering from spasticity. This measurement of spasticity is completely harmless and painless. There are no known side effects. I understand that the resistance to passive stretch of my ankle will be measured using the device. In conjunction with this measurement, the underlying motor unit firing pattern of the active muscle at my ankle will also be recorded. This is a passive measurement which is totally harmless and painless with no known side effects. The entire procedure would require approximately 60 minutes. The procedure for the spasticity measurement study will consist of: 1. Your foot will be placed in a foot pedal specially designed to hold your foot and ankle firmly in place. 2. A n electrode will be placed on your skin above the active muscle of your ankle. 3. With you attempting to relax your ankle, the spasticity measuring device will manipulate your ankle through a range of motion within your ankle's range. 4. The resistive torque to the passive stretch of your ankle will be recorded. 5. The electrode will passively record the motor unit firing pattern of the muscle in your ankle. This is an indication of the underlying activity of the muscle during the procedure. 6. Steps 2-5 will be repeated using different manipulation velocities and with you sitting down and lying down. This study is being carried out at the research laboratory of Dr. Doug Romilly in room 031 of the CICSR building. All procedures will be carried out in collaboration with Dr. Cecil Hershler and Dr. Doug Romilly of the U B C Mechanical Engineering program.  137  Appendix D - Data Analysis  Code  APPENDIX D - DATA ANALYSIS CODE  The data analysis was performed using a custom made M a t l a b ® program which fitted a least squares regression curve to the data. This code is shown below:  % determines the best fit of a second order differential system to a set of data % sampling rate of data collection system Ts=.04 ; % load data file load c.dat -ascii % displacement u=c(:,iy; % torque y=c(:,2)'; % plot original response subplot(2,l,l); plot([u;y]'); % order order=2; % minimum delay delay _min=0; % maximum delay delay _max=0; % least square fit theta=ide(y,u,delay_min,delay_max,order); % z-domain coefficients of O D E  139  b=[0,theta(3:4)]; a=[l,theta(l:2)]; % measure of quality of fit (the smaller the better) J=theta(5) % s-domain coefficients of O D E [bc,ac]=tfd2tfc(b,a,Ts); k=ac(l); ac=l/k*ac; bc=l/k*bc; % steady state gain K=bc(3)/ac(3) % natural frequency wn=sqrt(ac(3)) % damping ratio zeta=ac(2)/2/wn % Velocity gain V = bc(2) % determine fitted response yl=filter(b,a,u); % plot fitted and measured responses subplot(2,l,2); %plot([u;y/K;yl/K]'); plot([u;y/K;yl/K]'); % transfer a continuous transfer function to a discrete one function [NUM,DEN]=tfc2tfd(num,den,Ts); [a,b,c,d]=tf2ss(num,den); [P,G]=c2d(a,b,Ts); [NUM,DEN]=ss2tf(P,G,c,d, 1); % transfer a discrete transfer function to a continuous one function [num,den]=tfd2tfc(NUM,DEN,Ts);  Appendix D - Data Analysis  Code  [a,b,c,d]=tf2ss(NUM,DEN); [P,G]=d2c(a,b,Ts); [num,den]=ss2tf(P,G,c,d,l);  The distance  of the data from subjects with spasticity  from the interface curve  was  determined by minimizing the distance from an unknown point on the curve to a known data point. The equation to be minimized was differentiated and set to zero.  The equation was  solved using the following M a p l e ® code:  > y:=x 2/sqrt(x-0.73)+2.7; A  > F:=(x-zeta) 2+(y-omega) 2; A  A  > fd:=diff(F,x); > fdd:=diff(fd,x); > zeta:=2.4; > omega:=1.85; > z:=solve(fd,x); # First Solution > evalf(subs(x=z[l],sqrt(F))); > evalf(subs(x=z[l],fd)); > evalf(subs(x=z[l],fdd)); # Second Solution > evalf(subs(x=z[2],sqrt(F))); >evalf(subs(x=z[2],fd)); > evalf(subs(x=z[2],fdd)); # Possible Third Solution > evalf(subs(x=z[3],sqrt(F))); >evalf(subs(x=z[3],fd)); > evalf(subs(x=z[3],fdd));  141  Appendix D - Data Analysis  Code  # Possible Fourth Solution > evalf(subs(x=z[4],sqrt(F))); > evalf(subs(x=z[4],fd)); > evalf(subs(x=z[4],fdd));  142  

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