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The relative importance of proprioception, ligament laxity and strength on functional performance in… Govett, James Robert 1996

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T H E R E L A T I V E I M P O R T A N C E O F PROPRIOCEPTION, L I G A M E N T L A X I T Y A N D STRENGTH O N FUNCTIONAL P E R F O R M A N C E IN THE A C L DEFICIENT A N D A C L RECONSTRUCTED KNEE by  JAMES ROBERT GOVETT B . S . P . E . , The University of Saskatchewan, 1989 B . S c . (P.T.), The University of Saskatchewan, 1990  A THESIS SUBMITTED IN P A R T I A L F U L F I L L M E N T OF THE REQUIREMENTS FORTHE DEGREE OF M A S T E R OF SCIENCE in T H E F A C U L T Y OF G R A D U A T E STUDIES School of Human Kinetics W e accept this thesis as conforming to the required standard  T H E UNIVERSITY OF BRITISH C O L U M B I A December 1995 © James Robert Govett, 1995  In presenting this thesis in partial fulfilment  of the  requirements for an advanced  degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department  or by his  or  her representatives.  It is  understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department The University of British Columbia Vancouver, Canada  DE-6 (2/88)  Abstract The purpose  of this study was  to determine  the  relative importance  of  proprioception, ligament laxity and strength, in the performance of a functional skill, i n the conservatively and surgically managed subject following anterior cruciate ligament ( A C L ) injury. A second purpose o f the study was  to demonstrate  differences  i n knee  proprioception, anterior tibial displacement, quadriceps and hamstring muscle strength, and two functional performance tests among the following three groups:  1) conservatively  managed following A C L rupture, 2) surgically managed following A C L rupture, and 3) uninjured controls. The experimental groups consisted of twenty subjects greater than 8 months post A C L injury (conservative group) and twenty subjects greater than 1 year post A C L surgery (surgical group). These groups were compared to twenty control subjects with no history of significant knee joint injury. protocol of Barrett et al. (1991).  Joint position sense values were obtained using the Ligament laxity was tested by two anterior tibial  displacement measurements using the K T 1 0 0 0 knee ligament arthometer.  Quadriceps and  hamstring concentric and eccentric peak torque was measured using a K i n C o m isokinetic dynamometer.  Functional performance was measured with the single leg hop for  maximum distance ( S L H D ) and timed six metre single leg hop tests ( S L H T ) . The conservative group scored significantly worse than either o f the other groups in proprioceptive inaccuracy, both anterior displacement tests (134N and maximum manual test) and both functional hop tests ( S L H D and S L H T ) .  The surgical group was not  significantly different from the normal control group i n either proprioceptive function or functional hop testing.  The surgical group had an excellent post surgical outcome in  anterior displacement tests (2.1mm), while the conservative group had a poor result (5.5mm) with the maximum manual test. groups i n any of the strength measurements.  There were no significant differences among  Ill  Regressional analyses revealed that concentric quadriceps peak torque had a significant effect on single leg hop for maximum distance performance for all three groups. Proprioceptive acuity and anterior tibial displacement had no significant effect on S L H D in any of the three groups.  iv  Table of Contents  Abstract  ii  Table o f Contents  iv  List of Tables  v  List of Figures  vi  Acknowledgements  viii  Chapter One  INTRODUCTION  Chapter T w o  REVIEW OF LITERATURE Anatomy Biomechanics Neuroanatomy Functional Implications and Investigations Popular Hypotheses Conclusion  4 4 9 14 28 38 42  Chapter Three  DEFINITION OF T E R M S  44  Chapter Four  METHODOLOGY Subjects Surgical Procedure Testing Procedures Experimental Design and Analysis of Data  46 46 48 49 53  Chapter Five  RESULTS A N D DISCUSSION Descriptive Data Subjective Results Objective Results Discussion Limitations  55 55 56 62 82 92  Chapter Six  S U M M A R Y A N D CONCLUSIONS Summary Conclusions Recommendations  94 94 96 97  References Appendix A  1  99 SUBJECTIVE RATING SCALES Noyes Sports Activity Rating Scale Tegner & Lysholm Activity Score Change in Sport Level Lysholm Knee Scoring Scale  108 109 110 110 111  V  List of Tables  Table 4.1  Study Design Model  53  Table 5.1  Descriptive Data of Subjects by Group  55  Table 5.2  Noyes Sports Activity Rating Scale  56  Table 5.3  Tegner & Lysholm Activity Score (Response Counts)  58  Table 5.4  Tegner & Lysholm Activity Score (Ranges)  58  Table 5.5  Change in Sport Level  60  Table 5.6  Lysholm Knee Scoring Scale  61  Table 5.7  Proprioceptive Inaccuracy (Joint Position Sense)  62  Table 5.8  KT1000 Anterior Displacement  63  Table 5.9  Strength (KinCom): Peak Average Torque (Nm) and Symmetry Indexes  65  Table 5.10  Functional Performance (Single L e g Hop)  71  Table 5.11  Pearson Correlation Coefficients for Anterior Displacement and S L H D  75  Table 5.12  Pearson Correlation Coefficients for Strength and S L H D  75  Table 5.13  K T 1 0 0 0 Results for a Single Re-injured Subject  87  Table A l  Noyes Sports Activity Rating Scale  109  Table A 2  Tegner & Lysholm Activity Score  110  Table A 3  Change in Sport Level  110  Table A 4  Lysholm Knee Scoring Scale  111  vi  List of Figures  Figure 2.1  Microstructure of the anterior cruciate ligament  6  Figure 2.2  Major vascular supply of the knee joint  8  Figure 2.3  The articular surfaces o f the medial (right) and lateral (left) surfaces of the femoral condyles  10  Corresponding femoral and tibial contact points during knee extension demonstrating the changing ratio of rolling and gliding  11  Figure 2.5  Joint Proprioceptors  16  Figure 2.6  The neuromuscular spindle  17  Figure 2.7  G o l g i Tendon Organ  19  Figure 5.1  Noyes Sports Activity Rating Scale Pre and Post Injury/Surgery  57  Figure 2.4  Figure 5.2  Tegner & Lysholm Activity Scores Pre and Post Injury/Surgery  59  Figure 5.3  Change i n Sport Level and Associated Symptoms  60  Figure 5.4  Average Lysholm Knee Scoring Scale vs. Groups  61  Figure 5.5  Proprioceptive Inaccuracy by Groups  62  Figure 5.6  Anterior Displacement (KT1000 @ 134N) by Groups  64  Figure 5.7  Anterior Displacement (KT1000 @ M M T ) by Groups  64  Figure 5.8  Concentric Quadriceps Torque (Symmetry Index) by Groups Eccentric Quadriceps Torque (Symmetry Index) by Groups  67  Concentric Hamstring Torque (Symmetry Index) by Groups  68  Eccentric Hamstring Torque (Symmetry Index) by Groups  69  Concentric Hamstring:Quadriceps Ratio (InjAJninj.) by Groups  70  Mean Single L e g Hop for Maximum Distance (Symmetry Index) by Groups  72  Mean Timed 6 Metre Single Leg Hop (Symmetry Index) by Groups  73  Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 Figure 5.13 Figure 5.14 Figure 5.15  66  Whole M o d e l Regressional Analysis for Conservative Group  76  Figure 5.16  Strength Effect for Conservative Group  77  Figure 5.17  Proprioceptive Inaccuracy Effect for Conservative Group  77  vu Figure 5.18 Figure 5.19  Anterior Displacement Effect for Conservative Group  77  Whole M o d e l Regressional Analysis for Surgical Group  78  Figure 5.20  Strength Effect for Surgical Group  79  Figure 5.21  Proprioceptive Inaccuracy Effect for Surgical Group  79  Figure 5.22  Anterior Displacement Effect for Surgical Group  79  Figure 5.23  Whole M o d e l Regressional Analysis for Control Group  80  Figure 5.24  Strength Effect for Control Group  81  Figure 5.25  Proprioceptive Inaccuracy Effect for Control Group  81  Figure 5.26  Anterior Displacement Effect for Control Group  81  VU1  Acknowled gements  I would like to thank my thesis committee members, D r . Jack Taunton, D r . Pat M c C o n k e y , D r . D o n M c K e n z i e , and M r . Ronald Mattison, for their unending support  and encouragement  throughout this post  graduate  programme.  Completion of this degree was a component of the Sports Physiotherapy Fellowship Programme at the Allan M c G a v i n Sports Medicine.  I would  like to thank Trish Hopkins, Clyde Smith and R o n Mattison for the oportunity to participate in this programme, and for their assistance and patience throughout i t  1  Chapter One INTRODUCTION  Injury to the anterior cruciate ligament ( A C L ) is very common i n sports.  In fact, it  is reported to be the most frequently completely torn ligament i n the knee (Johnson, 1983). Injury of the A C L is often associated with other tissue damage such as medial collateral ligament tears medial meniscal tears and articular cartilage damage. Loss of the A C L may or may not result in a functional loss following initial rehabilitation, but performance of high level sport activities such as alpine skiing or sharp cutting and turning maneuvers are often not possible due to "giving way" or functional instability of the knee. Loss of the A C L results i n an 86% loss i n the knee's ability to restrain anterior displacement of the tibia with respect to the femur (Graf, 1987). The loss of the A C L also alters the arthrokinematics of the knee joint with a change in the instant centre of rotation during knee flexion and extension. This in turn changes joint forces which may cause the accelerated degenerative changes seen following A C L loss (Graf, 1987). The expected course of an untreated A C L deficient knee is one of progressive deterioration of function with  development  of rotatory  instability, meniscal tears,  degeneration of joint cartilage, and subsequent post-traumatic arthritis (Jackson, 1988; Johnson, 1983; McDaniel & Dameron, 1980; Odensten et al., 1985). Although the short term results of the untreated A C L rupture may appear similar to those of the surgically repaired knee, the long term results seem to differ greatly. Jackson (1988) points out that "there appears to be a natural sequela of arthritis and disability 20 or 30 years later" in the untreated cases. H e found that the incidence of meniscal tears rose from 60% to 90% over a ten year period following A C L disruption. The incidence of articular cartilage injury rose from 30% to 69% over the same period (Jackson, 1988). In a 10 year follow-up study of 53 untreated A C L injuries McDaniel et al. (1980) found that 33 knees demonstrated some  2  degree of valgus or varus laxity, only 8 knees had both menisci intact, and 10 knees demonstrated some degree o f articular cartilage degeneration. Early investigators have concentrated on the physical structure and biomechanical function of the A C L .  More recent investigations have begun to examine its neurological  structures, thereby considering a possible neurological function of the ligament as well as its more obvious mechanical role i n joint stabilization. Until recently, researchers believed that proprioception was entirely controlled by muscle spindles and golgi tendon organs. is now widely believed that joint proprioceptors  It  do contribute to some extent to  proprioception. Several recent histological and morphological studies have demonstrated  the  presence of mechanoreceptors in the human anterior cruciate ligament (Gardner, 1944; Gardner, 1948; Kennedy, 1982; Rowinski, 1985; Zimny, 1988a; Zimny, 1988b; Schutte & Happel, 1990; Haus & Halata, 1990; Johansson, Sjolander, & Sojka, 1991b). investigators  have  been  able  to  show  sensory  evoked  potentials  electromyographic ( E M G ) changes with the stimulation of the A C L .  (SEPs)  Some and  Barrack (1989) was  able to demonstrate a proprioceptive deficit (ability to detect joint movement) in A C L deficient subjects. Previously, investigators have found it difficult to show a correlation between the ability to perform high level activities such as cutting and turning (functional stability), and ligamentous laxity (mechanical stability). Barrett et al. (1991) showed that proprioception more closely correlated with patient satisfaction and function than did standard knee scores or clinical ligament testing. This suggests that proprioception is important during high level functional activities, and that it should be included when assessing the ligament deficient or injured knee. Loss of proprioceptive feedback, resulting from ligamentous injury, could affect the muscular control around the joint by decreasing the sensitivity of the muscle spindles. This might increase the chance of re-injury to the knee and accelerate degenerative changes.  The  3  idea that proprioceptive deficits might actually be a cause of joint degeneration instead of the result of it is supported by the degenerative changes seen in Charcot's joints i n which there is a proprioceptive loss but pain sensation remains unchanged.  These degenerative  changes are not seen in other neuropathies i n which pain sensation is lost, and proprioception remains unchanged. Further information regarding the proprioceptive loss following A C L disruption w i l l aid in the development of the ideal treatment for these individuals providing for a return to high level functional activities and insurance against the inevitability of subsequent injuries and degeneration of the knee. It is now being realized that mechanical stability, muscular strength, and neuro-muscular control all play an important part in the outcome following anterior cruciate ligament injury. This study w i l l attempt to determine the relative importance of each of these three components in the performance of two functional skills. It w i l l also compare differences in these components among A C L intact controls, A C L deficient subjects and A C L reconstructed subjects.  4  Chapter T w o REVIEW OF LITERATURE  Anatomy  Embryology The knee joint and its structures begin to form within the fourth to eighth week of development from a concentration of mesenchyme (Arnoczky & Warren, 1988; Reiman & Jackson, 1987).  A s the mesenchyme of the knee area condenses, a vascular portion  becomes isolated within the knee, and eventually forms the cruciate ligaments and menisci (Arnoczky & Warren, 1988). The anterior and posterior cruciate ligaments are separate from one another at about 10 weeks, and resemble adult ligaments by 20 weeks.  Little  change in form occurs after this point (Arnoczky & Warren, 1988). The anterior cruciate ligament initially appears i n a ventral position, but migrates  posteriorly into  the  intercondylar notch area (Reiman & Jackson, 1987). The ligament remains extrasynovial as it moves intraarticularly. Gross Anatomy The mature A C L is fan-shaped in structure, arising from the posterolateral aspect of the femur and attaching to the anteromedial aspect of the tibia. It is composed of multiple non-parallel interlacing collagenous fascicles of dense connective tissue (Dye & Cannon, 1988). A s noted above, the A C L is situated intraarticularly, but remains extrasynovial as it is enveloped by a synovial fold.  The A C L is about 3.5 cm long, and has a mean mid  portion thickness of about 1.1 c m .  The posterior cruciate ligament in comparison, is a  stronger structure about 3.8 cm long and 1.3 cm thick (Arnoczky & Warren, 1988). The femoral attachment of the A C L is oval in shape.  It is between 16 and 24 mm  in diameter, and covers an area of 2 c m (Dye & Cannon, 1988; Reiman & Jackson, 1987). 2  5  The A C L attaches to a fossa located posteriorly on the medial aspect of the lateral femoral condyle. The posterior border of the attachment is more convex than the anterior border. From this position, the A C L travels obliquely in a distal, anterior and medial direction to its tibial attachment. The tibial attachment is located between and anterior to the tibial spines. It inserts into a fossa located anterior and medial to the anteromedial tibial spine. The tibial attachment is about 11 mm wide, and 17 mm i n the anteroposterior direction, and covers an area of 3 c m (Dye & Cannon, 1988; Reiman & Jackson, 1987). 2  The anterior cruciate ligament crosses the knee joint as a collection o f individual fascicles fanning over a broad area, not as a single cord. The ligament rises upwards in a twisting fashion from the tibial to the femoral attachment The fascicles of the A C L have been divided into two groups, the anteromedial band and the posterolateral bulk.  The  anteromedial band includes those fascicles originating from the most proximal aspect of the femoral attachment, and inserting at the anteromedial aspect of the tibial attachment.  The  anteromedial band is most taught with the knee in a flexed position (Arnoczky, 1983). The posterolateral bulk, which includes the remaining fascicles, inserts at the posterolateral aspect of the tibial attachment. It is most taught with the knee i n extension (Arnoczky, 1983). A l l fibers of the A C L are tight with the knee in full extension.  Reiman (1987)  states "the important concepts of the normal anterior cruciate ligament are (1) that each fiber has a unique point o f origin and insertion, (2) that the fibers are not parallel and do not have the same length, and (3) that the fibers are not under the same tension at any one point in space". The meniscofemoral ligaments (previously thought to be a third cruciate ligament) have been described as accessory ligaments originating from the posterior horn of the lateral meniscus and attaching to the medial femoral condyle near the attachment o f the posterior cruciate ligament. They include the anterior meniscofemoral ligament (ligament of Humphry) and the posterior meniscofemoral ligament (ligament of Wrisberg).  Heller  (1964) examined 140 knees and found one of the two meniscofemoral ligaments present in  6  71%.  Only eight knees in the series demonstrated both meniscofemoral ligaments.  The  function of the meniscofemoral ligaments is unclear, but they appear to help position the posterior horn of the lateral meniscus during knee flexion thereby assisting joint congruency (Arnoczky & Warren, 1988). Microanatomy The anterior cruciate ligament is made up of fascicles of non parallel collagen tissue. Fibrils 150 to 250 nm in diameter are grouped together to form fibers 1 to 20 Jim in diameter (Dye & Cannon, 1988). These are in turn grouped to form subfascicular units 100 - 250 | i m in diameter, and are surrounded by endotenon, a loose connective tissue (Arnoczky, 1983). Groups of three to 20 subfasciculi are surrounded by epitenon to form fasciculi, which are aligned with the long axis of the ligament. The entire ligamentous unit is surrounded by paratenon (Fig. 2.1).  Endotendiheum  L  Figure 2.1 Microstructure of the anterior cruciate ligament. From: D y e , S. F . , & Cannon, W . D . (1988). Anatomy and Biomechanics of the Anterior Cruciate Ligament C l i n . Sports M e d . . 7(4), 715-726.  7  The ligament-bone attachment is characterized by a fibrocartilage transition zone. In this zone, ligamentous collagen fibers interdigitate with mineralized fibrocartilage from the adjacent bone.  This transition zone allows for a graduated change in stiffness thus  reducing concentration of stress at the attachment site (Arnoczky, 1983). The ligamentous branches of the middle genicular artery are responsible for the major blood supply to the anterior and posterior cruciate ligaments ( F i g . 2.2).  These  branches penetrate the ligament via the synovial envelope, and run parallel to the collagen fibers.  Some of the terminal branches of the medial and lateral inferior genicular arteries  also assist in A C L and P C L vascularization through connection with the infrapatellar fat pad (Arnoczky, 1987). A non-significant contribution to ligamentous vascularization arises from branches from the femoral and tibial epiphyses (Dye & Cannon, 1988). The posterior articular branch of the posterior tibial nerve supplies afferent fibers to the anterior cruciate ligament as well as other knee joint structures (Arnoczky & Warren, 1988). Fibers course through the synovial lining of the cruciate ligaments some of which ramify and send nerve fibers into the collagenous tissue (Johansson, Sjolander, & Sojka, 1991). Most o f the nerve fibers follow the endoligamentous vasculature which initially lead to the belief that their function was primarily for vasocontrol.  Subsequent  morphological studies have demonstrated the presence of four types of mechanoreceptors, indicating  a  proprioceptive function  (Johansson  et  al.,  1991).  The  types  of  mechanoreceptors that have been identified in cruciate ligaments are free nerve endings, golgi tendon-like organ endings, pacinian corpuscles and ruffini endings (Sjolander, Johansson, Sojka, & Rehnholm, 1989).  8  Descending genicular artery  Popliteal artery  Saphenous branch Articular branch  Lateral superior genicular artery  Medial superior genicular artery Middle genicular artery Epiphyseal branch Ligamentous branch Ascending parapatellar artery (medial) Oblique prepatellar artery (medial)  Lateral inferior genicular artery Circumflex fibular artery  Medial Inferior genicular artery  Anterior tibial recurrent artery  Figure 2.2 Major vascular supply of the knee joint. From: Arnoczky, S. P. (1987). The vasuclarity of the anterior cruciate ligament and associated structures. In D . W . Jackson & D . Drez (Eds.), The Anterior Cruciate Deficient Knee: N e w Concepts in Ligament Repair (pp. 27-54). Toronto: The C . V . M o s b y C o .  9  Biomechanics  Bryant and Cooke (1988) describe four functions of the anterior cruciate ligament. The primary function is to limit abnormal anterior translation of the proximal tibia on the distal femur throughout the normal knee range of motion. A second function of the A C L is to limit hyperextension of the knee. Cadaver studies by Girgis et al. (1975) demonstrated an average anterior drawer increase of 5.7 mm and an average hyperextension of 25° with severance of the A C L . The A C L ' s oblique orientation from the anteromedial aspect of the tibia to the posteromedial aspect of the lateral femoral condyle allows it to function additionally as a restraint to internal rotation of the tibia (particularly with the knee in an extended position), and to medial translation of the tibia (Bryant & Cooke, 1988).  The  A C L acts as a secondary restraint to valgus forces by preventing excessive medial translation of the tibia on the femur. Osteokinematics The shape of the femoral condyles has a direct effect on the biomechanics of the knee, and i n turn, the function of the A C L . The lateral femoral condyle is wider than the medial condyle, and the articular surface of the medial condyle extends further anteriorly than that of the lateral condyle (Fig. 2.3).  This longer articular surface corresponds with  the 15° of external tibial rotation which occurs at terminal extension (referred to as the screw-home mechanism) (Graf, 1987). Both femoral condyles, however, demonstrate a changing radius of curvature from the anterior to the posterior articular surfaces.  This  corresponds with a changing position of the instantaneous centre of rotation during knee flexion. The medial and lateral tibial plateaus are divided by two tibial spines which act to prevent medial or lateral subluxation of the tibia on the femur. The medial tibial plateau is  10  more concave than the lateral plateau, and more closely matches the shape of its corresponding femoral condyle (Graf, 1987). The menisci must also be considered when discussing kinematics of the knee. A s well as their function as shock absorbers, the menisci help to improve the joint congruency, and act to further stabilize the knee joint (Graf, 1987).  Figure 2.3 The articular surfaces of the medial (right) and lateral (left) surfaces of the femoral condyles. From: Graf, B . (1987). Biomechanics of the anterior cruciate ligament In D . W . Jackson & D . Drez (Eds.), The Anterior Cruciate Deficient Knee: N e w Concepts in Ligament Repair (pp. 55-71). Toronto: The C . V . Mosby C o .  Arthrokinematics Knee movement can be simplified by considering only those movements occurring in the sagital plane (flexion and extension).  During knee flexion, the convex femoral  condyles are said to "roll" on the tibial plateaus.  In order to prevent the condyles from  rolling off of the tibial plateaus, there must be an associated gliding motion of the tibia on  11  the femur. The ratio of rolling to gliding changes depending on the knee position. In this way, the femoral and tibial contact points also change depending on the position of the knee (Fig. 2.4) (MOller, 1983).  Figure 2.4 Corresponding femoral and tibial contact points during knee extension demonstrating the changing ratio o f rolling and gliding. From: Graf, B . (1987). Biomechanics of the anterior cruciate ligament. In D . W . Jackson & D . Drez (Eds.), The Anterior Cruciate Deficient Knee: N e w Concepts in Ligament Repair (pp. 55-71). Toronto: The C . V . M o s b y C o .  One final aspect of the arthrokinematics of the human knee is the phenomenon referred to as the "screw-home mechanism." During the last 20° o f knee extension, the tibia automatically externally rotates 15°. It is interesting to note that the cruciate ligaments are also 15° oblique from the sagital plane. The larger medial femoral condyle, mentioned earlier, allows this terminal rotation of the tibia The axis of rotation has been shown to be in line with the most lateral fibers of the posterior cruciate ligament at their tibial insertion (Miiller, 1983).  The anterior cruciate ligament, which is tight at terminal extension,  12  becomes even tighter with tibial internal rotation, but is relaxed during tibial external rotation, and may thus serve a role in regulating this automatic terminal rotation (Graf, 1987).  Kinetics The A C L is able to withstand forces of up to 1730 N (= 400 lbs.) before completely rupturing, with partial tearing occurring at lower levels (Butler, G r o o d , Noyes, & Sodd, 1985). Normal activities have been shown to load the A C L to about 454 N (=100 lbs.), well below maximal stiffness (Dye & Cannon, 1988).  Maximum strain, or elongation,  before failure of the A C L has been reported between 10 to 15% (Butler et al., 1985) and 25% (Dye & Cannon, 1988).  Arms et al. (1984) showed that cadaver knees moving  through a full range of motion demonstrated a maximum strain of 5.5%.  The least amount  of strain occurred between 30 and 35° of flexion (Arms, Pope, Johnson, Fischer, Arvidsson, & Eriksson, 1984). The forces applied across the A C L changes dramatically depending on whether the knee joint is loaded or unloaded (i.e. whether working with a closed or open kinetic chain). Hsieh and Walker (1976) state that in the unloaded situation joint stability is provided by the ligaments, joint capsule and menisci.  However, when the knee is compressed,  conformity of the femoral condyles becomes an important factor i n joint stability. This view was supported by Henning et al. in 1985, when they determined the relative anterior cruciate elongation with various loaded and unloaded activities. In this study, values of A C L anteromedial fiber elongation were reported relative to that occurring during an 80 pound Lachman test (given a value of 100). Results showed that loaded activities such as level walking, and a one-half single leg squat resulted i n relative A C L elongation o f 36 and 21 units respectively. Unloaded activities such as a leg lift with the knee held at 22° flexion  13  and an isometric quadriceps contraction at 22° flexion with a 20 l b . boot resulted in relative A C L elongation of 79 and 121 units respectively (Henning, L y n c h , & G l i c k , 1985).  14  Neuro-Anatomy  Proprioceptors Discussion of the neuro-anatomy of the knee and the A C L requires a understanding of the anatomy and function of the basic neural elements found within these structures. Proprioceptors are interoceptive mechanoreceptors. They include both joint receptors, and extraarticular receptors (muscle spindles and golgi tendon organs).  Joint receptors have  been classified into four main types by W y k e (1967) on the basis of morphological and behavioural criteria. Type I joint receptors (Ruffini endings) are globular or ovoid corpuscles. Ruffini endings are numerous in joint capsules of all joints and to a lesser extend in large ligaments (Rowinski, 1985). They are more numerous in the proximal joints of the extremities than in more distal joints. In the spine, they are found in greater numbers at the cervical level (Wyke, 1972). Ruffini endings are mostly located i n the outer layers of the joint capsules. They are more numerous i n those areas of the capsule which undergo the greatest changes in stress during joint movement (Wyke, 1972).  Ruffini endings contain spray type  terminal nerve endings, and some collagen fibres, which are thinly encapsulated by epithelial cells.  They are about 300 | i m by 300 - 800 p m in size (Rowinski, 1985).  Afferent nerve supply to type I joint receptors is by medium and large myelinated nerves ranging i n diameter from 8 to 17 u.m. Each axon can give rise to as many as six Ruffini endings (Rowinski, 1985). Ruffini endings have a l o w threshold and are slowly adapting receptors. They are sensitive to stretch of the joint capsule. Ruffini endings are categorized as both static and dynamic receptors. They signal static joint positions, intraarticular or atmospheric pressure changes, and direction, amplitude and velocity of joint movements produced either passively or actively (Freeman & W y k e , 1967a; Rowinski, 1985; Schutte & Happel, 1990; W y k e , 1972; Zimny, 1988a).  15  Type II joint receptors (Pacinian corpuscles) are elongated conical corpuscles containing a single unmyelinated nerve terminal, which is covered by a thickly multilaminated connective tissue capsule.  Type II joint receptors are found i n the fibrous  capsules of joints as well as articular fat pads (Rowinski,  1985;  Wyke,  1972).  M o r e recent  studies have found Pacinian corpuscles in joint ligaments as well (Haus & Halata, Zimny, Schutte, & Dabizies,  1986).  1990;  Pacinian corpuscles are found more numerously i n  the joint capsules o f distal joints than proximal joints. This is in contrast to Type I joint receptors.  Type U joint receptors are innervated by medium sized myelinated  fibres  ranging from 9 to 12 u.m i n diameter. Their conduction velocities are marginally slower than those o f Ruffini endings.  Pacinian corpuscles are cylindrically shaped and range i n  size from 20 - 40 Lim by 150 - 250 Lim. Pacinian corpuscles have a low threshold and are very quickly adapting.  They are  stimulated only by very rapid movements of the joint tissue because they adapt within a few thousandths o f a second (Guyton,  1981).  Type II joint receptors are sensitive to vibrations  over 60 H z , acceleration, and high velocity changes in joint position. They may also be sensitive to rapid contractions o f muscles adjacent to joints due to their influence on the joint capsule (Rowinski,  1985).  Pacinian corpuscles are not sensitive to static positions, or  slow joint movements. Type H I joint receptors (Golgi tendon organ-like receptors) present as fusiform endorgans which lie longitudinally to the superficial surfaces o f joint ligaments ( W y k e ,  1972).  G o l g i tendon organ-like receptors consist o f a filmy connective tissue capsule  enclosing a mass o f densely branching nerve filaments within collagen fibres. tendon organ-like receptors average  100  Lim by  600  Lim i n size ( R o w i n s k i ,  Golgi  1985).  Afferent nerve supply to type in joint receptors is via large myelinated axons o f up to 17 Lim in diameter (Wyke,  1972).  Conduction velocities are therefore the highest o f the joint  receptors. G o l g i tendon organ-like receptors are found i n all intrinsic and extrinsic joint ligaments.  16  Type HI joint receptors have a high threshold and are slowly adapting.  They are  inactive in immobile joints, but become active when the ligament is stressed at the extremes o f joint movements.  G o l g i tendon organ-like receptors may also be activated by joint  distraction. Type I V joint receptors are the non-capsular endings.  Free nerve endings arise  from small unmyelinated afferent nerves less than 5 u.m in diameter. Free nerve endings are located in joint capsules, synovium, articular fat pads and joint ligaments. Free nerve endings have a low to high threshold and are slowly adapting.  There  appear to be two types of free nerve endings. The first type is sensitive to non-noxious mechanical stress. The second is sensitive to noxious mechanical or biochemical stimuli. These are the nociceptors (Rowinski, 1985; W y k e , 1972).  ^ ^ ^ ^ ^ ^ Type I: Ruffini ending.  Type II: Pacinian corpuscle.  Type I V : Free nerve ending. Type UJ: G o l g i tendon organ-like receptor. Figure 2.5: Joint Proprioceptors. Modified from: Guyton, A . C . (1981). Textbook of Medical Physiology (6th ed.). Toronto: W . B . Saunders C o .  17  The neuromuscular  spindle (muscle spindle) is the  most complex of  the  proprioceptors (see F i g . 2.6), and the third most complex sensory organ behind the eye and ear (Schutte & Happel, 1990). parallel to skeletal muscle fibres.  Muscle spindles are fusiform structures located in  Their concentration is highest near musculo-tendinous  junctions. Muscle spindles can be up to 6 mm in length, and between 80 and 200 Lim in width (Keele et al., 1982).  They are enclosed by a collagenous capsule which is  continuous with the endomysium of the surrounding extrafusal muscle fibres. Within the spindle capsule are 2 to 14 intrafusal muscle fibres, which are surrounded by fluid at their equatorial region. This fluid gives the muscle spindle its characteristic fusiform shape. Intrafusal muscle fibres are smaller than extrafusal fibres with diameters of between 6 and 20 Lim (Keele et al., 1982)  The equatorial region of intrafusal fibres are poorly  striated and contain many nuclei. The polar regions, on the other hand, are well striated and contain fewer nuclei.  Intrafusal muscle fibres have been divided into nuclear bag  Motor 'endings  ii la Ar  Secondary (flower spray) sensory endings Primary (annulospiral) sensory endings  Nuclear chain fibre  Figure 2.6: The neuromuscular spindle. From: Barr, M . L . , & Kiernan, J. A . (1983). The Human Nervous System: A n Anatomical Viewpoint (Fourth ed.). N e w Y o r k : Harper & R o w , Publishers.  18  fibres, which have an expanded middle region containing an aggregation of nuclei, and nuclear chain fibres in which the nuclei run in a single line.  A typical muscle spindle  contains about 3 nuclear bag fibres and between 3 and 7 nuclear chain fibres (Guyton, 1981). Muscle spindles receive both afferent and efferent innervation. Afferent innervation is via group LA (primary) and group U (secondary) nerve fibres. Primary afferent fibres end in annulospiral terminals in the equatorial region of both intrafusal fibre types. afferents end to either side of the primary afferents.  Secondary  They end with flower spray terminals  on nuclear bag fibres, and either flower spray or annulospiral terminals on nuclear chain fibres (Barr & Kiernan, 1983).  Efferent supply to the muscle spindle is via y  x  and y  2  motor fibres. y efferents end in discrete end plates in the mid polar region of nuclear bag l  fibres. y  2  efferents end in diffuse terminal endings along much of the polar region of  nuclear chain fibres (Keele et al., 1982). Muscle spindles detect muscle length and the rate of change o f muscle length. They are slowly adapting receptors and w i l l continue firing at a given length for up to several hours.  When extrafusal fibres of a muscle are stretched, the muscle spindle is also  lengthened, which stimulates the group I A and group II afferent fibres. These fibres start a two neuron reflex arc which activates the a motor neurons supplying the muscle.  This  results in contraction of the muscle and in turn reduces the stretch on the muscle spindle. This is referred to as the stretch reflex. Efferent innervation o f the muscle spindle allows the spindle to vary its sensitivity. Activation of the y motor neurons causes the polar regions of the intrafusal fibres to contract, thereby increasing the stretch on their equatorial regions. This makes the muscle spindle more sensitive to external stretch, and is referred to as the y reflex loop. It is a mechanism in which the muscle spindle (via the y efferent system) can control the degree of muscle tone. It should be noted that over 30% of motor nerves supplying a muscle are y efferents, and that both a and y efferents are activated by nearly all conscious and subconscious areas of the brain. The y reflex loop is  responsible  19  for what is thought to act as a servo-assist mechanism, in which discrepancies between extrafusal and intrafusal fibre contractions are picked up, resulting i n reflex activation to correct the differences (Guyton, 1981). G o l g i tendon organs are found in tendons (and fascia) most commonly at the muscular attachments (see F i g . 2.7). They are simple mechanoreceptors consisting of one, or possibly more, afferent nerve fibres terminating on a few collagenous fibres.  The  receptor is encapsulated by thin connective tissue. Typically about 10 to 15 muscle fibres attach in series with each golgi tendon organ (Guyton, 1981).  Afferent nerve supply to  golgi tendon organs is v i a group LB fibres about 16Lim in diameter. These fibres are only slightly smaller and slower than those supplying muscle spindles.  Muscle  Figure 2.7: G o l g i Tendon Organ. From: Guyton, A . C . (1981). Textbook of Medical Physiology (6th ed.). Toronto: W . B . Saunders C o .  G o l g i tendon organs respond to tension produced by muscle contraction. This is i n contrast to muscle spindles which respond to muscle length. Stimulation of golgi tendon organs results i n signals being sent to the spinal cord where a cord reflex is triggered. This local cord reflex results in inhibition of a motor neurons supplying the specific muscle fibres attaching to the golgi tendon organ which was stimulated.  G o l g i tendon organs  therefore act to limit the tension applied across the musculotendinous unit. Afferent signals  20  from golgi tendon organs also reach the cerebellum via the spinocerebellar tracts, and the cerebral cortex via other tracts. G o l g i tendon organs are slowly adapting mechanoreceptors. They are characterized by having an initial dynamic response, in which there is a sudden strong response to a rapid increase in tension. This quickly reduces, within a fraction of a second, to a lower steady state response in which the firing from the receptor is proportional to the tension across it. G o l g i tendon organs have a higher threshold than muscle spindles, and therefore inhibit muscle activity only at high tensions. Sensory Innervation of the Knee Several studies have been conducted examining the anatomy and specifically the neuroanatomy of the knee. The most extensive anatomical studies of the nerve supply to the human knee to date, were by Gardner in the 1940's.  Since that time, there has been a  relative lack of interest expressed in the neurology of the knee joint, i n favour of structural and biomechanical considerations.  However, within the past ten years, there has been  renewed interest in the sensory function of the knee joint.  Perhaps a key factor in this  resurgence has been the lack of a clearly superior surgical treatment for anterior cruciate ligament ruptures. This failure has lead some investigators to consider function of the A C L other than its mechanical role in joint stabilization. The majority of studies have utilized either feline or human knee joints. The use o f the cat as an animal model appears to be sound, since the similarities between neuroanatomy of the feline knee and the human knee have proven to be much greater than their differences (Johansson, Sjolander, & Sojka, 1991a; Zimny et al., 1986).  Other  animal models which have been used include the dog (Miyatsu, Atsuta, & Watakabe, 1993) and rabbit (Amiel, Frank, Harwood et al., 1984). Gardner (1948) described two distinct groups of afferent nerves supplying the human knee: the posterior group, and the anterior group. The posterior group consists of  21  the posterior articular nerve ( P A N ) and the obturator nerve. The anterior group includes articular branches o f the femoral nerve, the common peroneal nerve, and the saphenous nerve. Johansson (1991) in his review of the literature, discussed three primary afferent nerves supplying the knee (Johansson, Sjolander, & Sojka, 1991b).  These are the  posterior articular nerve, the medial articular nerve ( M A N ) , and the lateral articular nerve (LAN).  However, this terminology is more frequently use in describing the feline knee  joint. When describing the human knee joint, the M A N is referred to as the saphenous and/or obturator nerves, and the L A N is called the common peroneal nerve. This appears to be more a difference in semantics than in anatomical uniqueness It should be noted that afferent nerves innervating the knee joint supply the area through which they travel. They do not supply specific tissues within the knee joint (Rowinski, 1985).  Although all structures within the knee are innervated by sensory  neurons, axons and receptors are rarely found within the deep fibrous substance of ligaments or menisci (Kennedy et al., 1982).  Gardner (1948) concludes that "no nerve  supplies a portion of the capsule which is not reached by another nerve." Finally, Kennedy (1982) makes it very clear that there exist individual differences in the size, extent of innervation, and location of afferent nerves in the knee. Primary Articular Nerves of the Knee Joint The following paragraphs w i l l discuss each individual sensory nerve supplying the knee joint. Specifically, the nerve's origin, location, pathway, and targets w i l l be outlined. The posterior articular nerve ( P A N ) is the largest and most consistent nerve supplying the knee (Kennedy et al., 1982). It arises from the posterior tibial nerve usually below the level of the popliteal fossa (Freeman & W y k e , 1967b; Gardner, 1944), but may arise above the knee or within the popliteal fossa (Kennedy et al., 1982). The nerve travels through the fatty substance of the popliteal plexus, where it penetrates the oblique popliteal ligament From here, fibres supply the fibrous capsule and the external part of the menisci.  22  Other fibres penetrate the posterior capsule, and travel through the synovial lining of the cruciate ligaments. Axons from the P A N reach as far anteriorly as the infrapatellar fat pad (Kennedy et al., 1982). The P A N innervates the posterior capsule, the posterior fat pads, the posterior oblique ligaments, the medial ( M C L ) and lateral ( L C L ) collateral ligaments, the anterior and posterior cruciate ligaments, the annular ligaments and outer regions of the medial and lateral menisci, and the infrapatellar fat pad (Johansson, Sjolander, & Sojka, 1991b; Kennedy et al., 1982). The medial articular nerve ( M A N ) may include branches from the obturator nerve and/or the saphenous nerve. The terminal portion of the obturator nerve arises from either the anterior or posterior divisions of the obturator nerve. It often accompanies the femoral artery into the popliteal fossa, before traveling anteriorly and medially. The infrapatellar branch of the saphenous nerve splits from the saphenous nerve between the tendons of the sartorius and gracilis and travels anteriorly and medially along the tibia just below the joint line (Kennedy et al., 1982). The M A N supplies the medial and antero-medial aspect o f the fibrous capsule, the M C L , the medial meniscus, the patellar tendon, the infrapatellar fat pad, and the medial part of the patellar periosteum (Freeman & W y k e , 1967b; Gardner, 1944). The lateral articular nerve ( L A N ) is the most inconsistent of the primary articular nerves to the knee. When present, it arises from the common peroneal nerve at the level of the joint line posterior and superior to the fibular head (Kennedy et al., 1982). It innervates the capsule of the superior tibio-fibular joint, the inferior portion of the lateral capsule of the knee, the L C L , and the peroneal muscles (Freeman & W y k e , 1967b; Gardner, 1944; Kennedy et al., 1982). Secondary Articular Nerves of the Knee Joint In addition to the above primary articular nerves, the knee joint is innervated to a small extent by secondary or accessory articular nerves.  These are small intramuscular  23  articular nerves arising from the main muscle nerves. Accessory articular nerves have been found i n the quadriceps, sartorius and gastrocnemius muscles (Freeman & W y k e , 1967b; Gardner, 1944; Kennedy et al., 1982). Freeman and W y k e (1967) suggest that secondary articular nerves may innervate the medial and posterior capsule, the patellar tendon, the infrapatellar fat pad, and the superior aspect of the M C L . Innervation o f Specific Joint Structures The joint capsule is innervated posteriorly by the P A N , medially by the M A N , and laterally by the L A N .  Fibres from these afferents reach all areas of the capsule and  terminate with free nerve endings, Ruffini endings, and Pacinian corpuscles (Schutte & Happel, 1990; Z i m n y , 1988b). Specifically, free nerve endings are found in the fibrous portion of the capsule and the subsynovial capsule, Ruffini endings are found only i n the fibrous portion of the capsule, and Pacinian corpuscles are found in the fibrous portion of the capsule and the capsule-synovium border (Rowinski, 1985).  In the capsule, slowly  adapting Ruffini endings out-number rapidly adapting Pacinian corpuscles (Johansson et al., 1991b). The synovium according to Kennedy (1982) is richly innervated primarily with single axons. Most of the receptors within the synovium are free nerve endings, with some Pacinian corpuscles found on the capsulo-synovium border (Rowinski, 1985).  Haus &  Halata (1990) found free nerve endings, Ruffini corpuscles and Pacinian corpuscles within the synovium surrounding the cruciate ligaments. Several investigators have studied the afferent innervation of the menisci. Kennedy et al. (1982) were unable to identify neither nerve fibres nor receptors within the menisci, but instead found many axons, free nerve endings, and golgi-type endings within the perimeniscal capsular tissue. Zimny (1988) found nerves penetrating the outer and middle thirds of the body and horns from the perimeniscal capsular tissue. They found a greater concentration of neural elements at the meniscal horns.  Encapsulated receptors  were  24  mainly found in the outer third of the menisci, while free nerve endings were mainly found in the middle third. Schutte (1990) found Ruffini endings, Pacinian corpuscles and golgi tendon organ-like endings i n the middle and outer thirds of the menisci (Schutte & Happel, 1990). The infrapatellar and posterior fat pads are innervated by axons from the P A N and M A N , and P A N respectively (Kennedy et al., 1982). Most endings i n the fat pads are free nerve endings for vascular control and pain (Rowinski, 1985). The collateral ligaments have been reported to contain Ruffini endings, golgi tendon organ-like endings, and free nerve endings, but not Pacinian corpuscles  (Johansson,  Sjolander, & Sojka, 1991b). The M C L is innervated by the P A N and the M A N . The L C L is innervated by the P A N and the L A N . Innervation of the Anterior Cruciate Ligament Nerve supply to the anterior cruciate ligament ( A C L ) arises from the posterior articular nerve (itself a branch of the tibial nerve) (Arnoczky, 1983; Arnoczky & Warren, 1988; Freeman & W y k e , 1967a; Gardner, 1944). A s with most intraarticular structures, the majority  of  nerves  supplying the  A C L are  associated  with  the  peri-  and  endoligamentous vasculature (Arnoczky, 1983). Branches of the P A N reaching the A C L have been shown to run together with the medial genicular artery, which is the primary blood supply to the ligament (Haus & Halata, 1990). The pathway taken by the A C L ' s nerve supply begins with the P A N penetrating the posterior capsule of the knee. From here, nerve fibres course around the periligamentous vessels within the synovium surrounding the A C L (Arnoczky, 1983; Arnoczky & Warren, 1988).  Fibres then reach deeper to the subsynovial connective tissue (Halata & Haus,  1989; Zimny et al., 1986). Axons then leave the neurovascular bundles i n the subsynovial connective tissue to enter the ligament (Schutte, Dabezies, & Zimny, 1987; Zimny et a l . , 1986).  25  Kennedy (1982) found most neural elements associated with the A C L to be located in the multiple clefts in the tibial origin of the ligament, and within its richly vascularized synovial coverings.  Arnoczky (1983 & 1988) found small nerve fibres throughout the  substance of the A C L , with some fibres lying alone among the fascicles of the ligament. Haus (1990) found nerve fibres in the synovium and in the interfascicular connective tissue. However, they did not find nerve fibres running through the fascicles themselves. Nerve fibres found within the A C L and its periligamentous connective tissue were both myelinated and unmyelinated. Haus (1990) found nerve fibres reaching sizes o f up to 250 p m .  Four kinds of nerves were noted within the A C L :  1) small nerves with  unmyelinated nerve fibres, 2) mixed nerves with myelinated and unmyelinated nerve fibres, 3) mixed nerves with one to three vessels at their margins, and 4) mixed nerves with vessels at their margins and an additional perineural sheath (Haus & Halata, 1990). Schultz (1984) was the first investigator to histologically demonstrate the presence of mechanoreceptors in the human anterior cruciate ligament H e was able to identify free nerve ending, Ruffini endings, Pacinian corpuscles, and golgi tendon organ-like endings. Since 1984, several investigators have looked for the presence of mechanoreceptors within the A C L .  Their results have generally fallen into three categories. The first (Kennedy et  al., 1982) found no specialized receptors in the human A C L , but did find golgi-like receptors near the origin of the ligament. The second and third all found mechanoreceptors within the A C L , but differ in which receptors were identified. Some identified only free nerve endings, Ruffini endings, and Pacinian corpuscles QHalata & Haus, 1989; Haus & Halata, 1990; Schutte et al., 1987; Zimny et al., 1986), while others demonstrated the presence of free nerve endings, Ruffini endings, Pacinian corpuscles, and golgi tendon organ-like endings (Arnoczky & Warren, 1988; Schultz, Miller, Kerr, & Micheli, 1984; Schutte & Happel, 1990; Sjolander, Johansson, 1988b).  Sojka, & Rehnholm, 1989; Z i m n y ,  26  Although Schutte (1987) identified only three receptor types, he differentiated between two types o f slow-adapting Ruffini endings. One o f these Ruffini endings was described as closely resembling a golgi tendon organ. Johansson (1991) notes that both Ruffini endings and golgi tendon organ-like endings are slowly adapting spray endings, which "seem to constitute a continuous spectrum of varieties." H e continues to state that the classification  of these two receptors  as different categories appears arbitrary  (Johansson, Sjolander, & Sojka, 1991b). Zimny (1986) found that neural elements within the A C L constituted approximately 2.5%  of the ligament  A subsequent study by Schutte (1987) found nerve fibres and  receptors to comprise 1.0% o f the area of the A C L . They later estimated the volume o f the neuronal tissue to be between 1.0% and 2.5% of the total volume of the A C L . The majority of receptors have been located near the ends of the cruciate ligaments, while only few have been identified in the middle one-third. Some investigators (Kennedy et al., 1982; Schutte et al., 1987; Zimny, 1988a) have noted that most receptors are found near the tibial origin, while others (Arnoczky & Warren, 1988; Sjolander et a l . , 1989; Zimny et al., 1986) have found receptors to be concentrated near both the tibial and femoral origins of the ligament. Information regarding the relative frequency of different receptors within the A C L has been variable. Sjolander (1989) found that Ruffini endings and Pacinian corpuscles were slightly more common than golgi tendon organ-like endings in the feline A C L . Zimny (1988) examined human A C L s and found Pacinian corpuscles and golgi tendon organ-like endings to be more numerous than Ruffini endings. Haus (1990) also studied human A C L s and found 21 Ruffini endings, 5 Pacinian corpuscles, and no golgi tendon organ-like endings. Only Haus (1990) has reported the location of specific mechanoreceptors.  They  found that 4 3 % o f the Ruffini endings identified were located i n the interfascicular regions of the ligaments. 47% were located in the subsynovial layer, and 10% were located i n the  27  border zone between the ligament and synovium.  When they viewed the ligaments  longitudinally, 47% of the Ruffini endings were situated in the femoral one-third of the ligament, 29% in the tibial one-third, and 24% in the middle one-third. A l l of the Pacinian corpuscles identified were found in the subsynovial layer of the ligament  40% of these  were located in the femoral one-third, 40% in the tibial one third, and 20% i n the middle one-third of the ligament. N o golgi tendon organ-like endings were identified (Haus & Halata, 1990).  28  Functional Implications and Investigations A s discussed in the previous section, it has been demonstrated that there exists neural tissue in nearly all knee joint structures.  Specifically, nerves and specialized  mechanoreceptors have been found in the anterior cruciate ligament. Although histologic and morphologic studies have revealed much information pertaining to the structure and location of these structures,  little information has  been  acquired  regarding  their  physiological function and functional significance. Several approaches have been tried attempting to answer these questions.  These  include direct investigations such as electromyographic studies attempting to isolate specific reflexes or changes i n muscle recruitment patterns, and peripheral nerve and somatosensory evoked potentials. Indirect investigations measuring joint position sense, joint movement sense, gait abnormalities and functional skill performance have also been performed. In this section, each of the major areas of investigation i n the search for the functional importance of the proprioceptive function of the anterior cruciate ligament w i l l be reviewed.  The discussion w i l l conclude with an overview of two popular hypotheses  regarding the proprioceptive function of the A C L . Electromyographic Studies Electromyographic studies have been used extensively for investigating the reflex muscle activity associated with stimulating joint mechanoreceptors.  In 1965, deAndrade  was able to show a reduction in quadriceps activity following distention of the knee joint with normal saline. When knees were distended with an anaesthetic solution, activity was reduced to a lower level. This indicated that capsular mechanoreceptors have an influence on quadriceps function (deAndrade et al., 1965). Freeman & W y k e , in 1967, measured E M G activity of the gastrocnemius and tibialis anterior muscles with passive movement of the feline ankle. Their results showed that passive  dorsiflexion resulted  in gastrocnemius  activation and tibialis  anterior  29  depression, while passive plantar flexion resulted in gastrocnemius depression and tibialis anterior activation.  The results were diminished, but still evident with skinning and  tenotomy of the ankles.  However, the introduction of a local anaesthetic to the joint  capsule completely abolished the responses.  A neurectomy of the articular nerves also  abolished the responses, although myotatic reflexes were still present (Freeman & W y k e , 1967b). Solomonow et al. (1987) recorded E M G responses of the quadriceps and hamstring muscles while stressing the feline knee.  They were able to show increased hamstring  muscle activity with direct loading of the A C L .  The quadriceps muscle demonstrated a  transient increase i n activation, followed by no activity while the A C L was loaded. These responses were evident only when high loads were applied to the A C L (130N). N o reflex activity was seen when low or medium loads were applied to the A C L .  These results, in  addition to histologic studies showing that most receptors were found near the ligament attachments (an area that becomes strained only at high loads), seemed to indicate an "on demand" function of the ACL-hamstring reflex (Solomonow, Baratta, Shoji, Bose, Beck, & D'Ambrosia, 1987). A similar study measuring E M G responses i n anaesthetized cats with controlled anterior tibial displacements and direct A C L loads was performed by Pope et al (1990). Their results showed no reflex activity with tibial displacements up to 4 mm (regardless of speed) and no reflex activity with direct loading of the A C L . demonstrate myotatic reflexes.  They were, however, able to  The authors concluded that "while traction on the intact  A C L causes signals in the afferent nerves, those signals are not translated into direct monosynaptic reflexes." (Pope, 1990) W o o d et al., in 1987, measured E M G activation of the quadriceps muscles while directly stimulating the posterior articular nerve ( P A N ) .  They found a synchronization  between motor unit firing and P A N stimulation. Anaesthetizing the P A N resulted i n the  30  loss of synchronization of motor unit firing, although the total intensity of the firing remained constant (Wood, Baxendale, Ferrell, et al., 1988). Kalund et al. (1990) compared E M G activity of thigh muscles of A C L deficient and normal volunteers walking on a treadmill. N o differences were found with walking on a level treadmill.  However, the A C L deficient subjects demonstrated earlier hamstring  activation with uphill walking. They proposed that this altered muscle coordination was required in A C L deficient patients in order to stabilize the knee (Kalund, Sinkjaer, ArendtNielsen, & Simonsen, 1990). Finally, a recent article by Miyatsu et al. (1993) demonstrated an increase in activity in the quadriceps and hamstring muscles in response to physiological loading of the A C L in unanaesthetized spinalized cats and dogs.  They concluded that "the ACL-muscle reflex  may therefore play a physiological role in maintaining knee kinematics." (Miyatsu et a l . , 1993) Evoked Potential Studies Although electromyographic studies have been useful i n detecting muscle activation and recruitment pattern changes with functional activity in the A C L deficient subject, and with direct stimulation of the knee joint capsule and A C L , they have been inconclusive in demonstrating the mechanism in which the A C L functions proprioceptively.  For this  reason, several investigators have chosen to measure evoked potentials in an attempt to more clearly follow the responses of the joint mechanoreceptors. Boyd  (1954) measured single-fibre discharges of the P A N in response  to  movement o f the feline knee. H e found a large number o f slowly adapting receptors and a smaller number of rapidly adapting receptors by stimulating areas of the joint capsule. H e concluded after localizing areas of the capsule which corresponded to slowly adapting receptor potentials in the P A N , that large fibres in the P A N appeared to be innervated by  31  mffini endings in the joint capsule. H e added that golgi tendon organ-like receptors i n the ligaments of the joints may also innervate large fibres in the P A N (Boyd, 1954). In 1992, Krauspe et al. measured evoked potentials from afferent fibres of the P A N in anaesthetized cats while the A C L was stimulated by applying local pressure.  They  showed no firing o f the afferent fibres while the knees were at rest i n 30° o f flexion, but activity was found when the knees were flexed and extended, and internally or externally rotated. Moreover, although afferent firing occurred when the knees were moved through a working range of motion, their activity was markedly increased when the joint was hyperextended and internally or externally rotated.  Krauspe et al. suspected that other  nerves also contribute afferent fibres to the A C L for the following reasons:  they were  unable to identify any afferent unit from the A C L in two experiments, and they were not able to identify receptive fields near the tibial attachments although mechanoreceptors have been described i n this region of the A C L (Krauspe, Schmidt & Schomburg, 1992). Miyatsu et al. (1993) studied the physiological role of A C L mechanoreceptors in unanaesthetized spinalized cats and dogs with both E M G and evoked potential experiments. Their results showed that evoked potentials in the P A N were elicited by electrical stimulation of the surface of the ligament, and by physiological loading of the A C L . They concluded that " A C L loading has an excitatory effect on the thigh muscles through a multimotor neurone output, and that the P A N is one of the afferent routes from the mechanoreceptors of the A C L . " It was also noted that "the average load which induced the maximal E M G discharge was less than the animals' body weight and this suggests that the levels of thigh muscle tone could be altered within the physiological range." (Miyatsu et al., 1993) Somatosensory evoked potentials have been used to locate central nervous system activity resulting from knee movement. Halata et al. (1977) demonstrated altered discharge rates in cells located in the nucleus gracilis, cuneate nucleus and somatosensory thalamus in response to changing knee joint angles (Halata, 1977).  32  Pitman et al. (1992) measured cortical evoked potentials i n nine patients undergoing arthroscopic surgery when intact A C L ' s were electrically stimulated. were recorded at the cerebral cortex upon stimulation of the A C L .  In all cases, S E P s Surprisingly, the  greatest potentials were reported upon stimulation of the midsubstance of the ligament, and not the attachments.  It is known that S E P s monitor proprioceptive information from  peripheral nerves and the posterior columns of the spinal cord.  In humans, S E P ' s are  correlated with spinal cord lesions that impair joint position sense and awareness of passive joint movements. Pitman et al. make note that their method measures direct evidence of the proprioceptive function of the A C L (Pitman, Nainzadeh, Menche, et al., 1992). In 1986, Johansson et al. measured the evoked potentials of single lumbar ymotoneurones caused by electrical stimulation of fibres of the feline P A N .  Their results  showed that in 80% of the animals tested, low threshold stimulation of the P A N resulted in y-motoneurone evoked potentials. They concluded that "activity in fibres running i n the P A N of the knee joint causes excitatory and/or inhibitory post-synaptic effects on static and dynamic y-motoneurones projecting to flexor and extensor muscles." It was also suggested that "low-threshold afferents act more potently on the y- than on the a-motoneurones." (Johansson, Sjolander, & Sojka, 1986) Joint Position Sense Studies The measurement of knee joint position sense has been used to try to demonstrate a proprioceptive deficit in the A C L deficient population. The results from many studies have been variable and contradictory. Differences in techniques used to measure joint position sense, including whether matching with the contralateral limb, passive movement of the ipsilateral limb, or a visual anologue is used for the measurement, may be i n part responsible for the differing results.  Another confounding factor is the large role the  muscle-tendon units play in determining joint position.  Minimizing this influence to  demonstrate a smaller joint receptor deficit has been the primary goal of several studies.  33  Barrack (1983) measured the ability of subjects to reproduce passive positioning of the knee and to detect a change in knee angle in ten healthy volunteers. H a l f of the knees were injected with 2% lidocaine the other with saline. H e found no difference between pre and post injection measurements in either group.  H e concluded that intraarticular  anaesthesia had no effect on joint proprioception as measured (Barrack, 1983). In 1988, D v i r et al. measured post-operative A C L reconstruction subjects' ability to reproduce passive positioning o f the knee (matching o f joint positions were done passively, concentrically, eccentrically, and as quickly as possible).  They found no significant  differences between the normal and operated knees. They concluded that "the role of the A C L in knee static position sense is secondary and that this function is likely to be controlled entirely by knee musculature." In 1991, Barrett et al. attempted to minimize the influence of the knee musculature in determining knee joint position by having subjects indicate the perceived joint position with a visual anologue, instead of using ipsilateral or contralateral limb matching. In one study they measured joint position sense i n knees with semi-constrained joint replacements (in which the joint capsule is retained), and knees with hinged joint replacements (in which the joint capsule is removed). They found that semi-constrained knee replacements resulted in a better improvement of proprioception than did the hinged replacements. In a second study, Barrett measured joint position sense, standard knee scores, clinical ligament testing and patient satisfaction in normal, A C L deficient and A C L reconstructed knees (Barrett, 1991).  H e found that standard knee scores and clinical  ligament testing correlated poorly with patient satisfaction (r = -0.18 in both cases), and with functional results (r = -0.24 and r = -0.19 respectively). Proprioception, however, correlated well with both function (r = -0.84) and with patient satisfaction (r = -0.9).  In  this study, he found that " A C L deficient knees showed significantly poorer joint position sense than did the knees of age-matched patients after A C L reconstruction and normal knees." Barrett concluded that there was a close correlation between proprioception and  34  both patient satisfaction and functional outcome, and that returning to sport participation may be more dependent on proprioception than on ligament tension. Corrigan (1992) also demonstrated a loss in joint position sense of 20 subjects with A C L insufficiency when compared to 17 age-matched control subjects. H e also found a significant correlation between hamstring/quadriceps strength ratio and joint position sense (r = -0.77, p < 0.01) (Corrigan, Cashman, & Brady, 1992). Joint Movement Sense Studies Another area in which researchers have attempted to demonstrate a proprioceptive loss i n the A C L deficient population is in the ability to detect knee joint movements. Barrack et al. (1989) measured the threshold to detection of passive change in knee joint position in a group of patients with documented complete A C L tears and in normal subjects.  They found normal subjects demonstrated virtually identical threshold values  between their two knees, with the mean variation being less than 2%. The A C L deficient group, however, showed a significandy higher mean threshold value for their A C L deficient knee versus their uninjured knee. The mean variation between knees in the test group was over 25%. Multivariate analysis indicated that the loss of proprioception i n the injured knees was attributable to the loss of the A C L and not to other variables such as thigh circumference, isokinetic muscle strength differences, time since injury and subject age (Barrack, Skinner, & Buckley, 1989). The 1992 study conducted by Corrigan et al. also measured threshold for movement detection in A C L deficient and control subjects.  Their results showed a  diminished threshold for movement detection i n the injured subjects.  They also  demonstrated a significant correlation between hamstring/quadriceps strength ratio and threshold for movement detection (r = -0.74, p < 0.0.1) (Corrigan, Cashman, & Brady, 1992).  35  Gait Analysis & Functional Studies The measurement of gait parameters and functional skill performance have also been inconclusive in demonstrating specific functional losses following A C L injury or blocking of knee joint proprioceptive influences. Barrack et al. (1983) examined 10 healthy knees during gait analysis. H a l f of the knees were injected with a 2% lidocaine solution, the other half with normal saline. They found no changes in gait velocity, cadence, stride length or gait cycle time i n either group after injection (Barrack, Skinner, Brunet, Haddad, 1983). Kalund et al. measured period of heel contact in nine A C L deficient subjects while walking on a horizontal level and during uphill walking (Kalund, Sinkjaer, Arendt-Nielsen, & Simonsen, 1990). Although E M G changes in the quadriceps and hamstring muscles were seen during uphill walking, no differences i n gait were found i n either test condition. Another study comparing gait patterns in A C L deficient and normal subjects was conducted by Gauffin et al. (1990). They found no significant difference i n gait velocity, stride length at maximal velocity, and single and double support phases between the two  groups  (Gauffin, Pettersson, Tegner, & Tropp, 1990). Measuring functional skill performance such as single-leg hopping, shuttle running and figure-of-eight running has been attempted to more closely measure the demands of athletic performance. Again, results have been variable since many other factors other than joint function come into play in the performance of such skills. In 1989, Barber et al. compared A C L deficient knees with normal knees i n the ability to perform five functional tests (single-leg hop for distance, single-leg vertical jump, 6 metre single-leg timed hop, shuttle run with no pivoting, and shuttle run with pivoting). They found that 90% of normal subjects demonstrated an 85% symmetry index in the hop for distance and the timed hop tests, but a large percentage (27%) of normal subjects fell outside an 80% symmetry index i n the vertical jump test. This lead the authors to question  36  the value of the vertical jump test in being able to show deficits in an A C L deficient population.  In the A C L deficient group, more than 90% of the subjects scored in the  normal limb symmetry range for the two shuttle run tests. In the single leg hopping tests 50% of the A C L deficient group performed normally. This lack of sensitivity was reduced i f both tests were used instead of either one. B y considering both tests, 60% of the A C L deficient group scored abnormally i n at least one test. This is compared to 4 2 % to 50% i f either test was used individually.  The single-leg hop tests correlated with subjective  complaints of difficulties pivoting, cutting and twisting, and with quadriceps weakness and patellofemoral compression pain (Barber, Noyes, Mangine, & M c C l o s k y , 1990). Daniel et al. (1982) tested 100 normal subjects performing a single leg hop.  They  found that the hop index (the limb with lesser hop distance divided by the limb with greater hop distance, multiplied by 100) ranged from 82% to 100% with a mean value of 96%. Hop index was not affected by gender or athletic participation. They concluded that a hop index of over 89 was considered satisfactory (Daniel, M a l c o m , Stone, et al., 1982). Noyes et al. (1990) compared four tests (single-leg hop for distance, timed singleleg hop, triple hop, and timed cross-over hop) i n order to determine how sensitive each was in detecting abnormal limb symmetry in A C L deficient patients. Their results showed that the triple hop and the timed cross-over hop had the same number of abnormal cases as the single-leg hop tests.  Their results also showed that 62% o f A C L deficient subjects  scored abnormally on at least one of the two single-leg hop tests. When only one hop test was considered, the abnormal scores decreased to 48 and 5 1 % (Noyes, Barber & Mangine, 1990). Tegner et al. (1985) found no difference between A C L deficient patients' and post reconstructive surgery patients' ability to perform four functional tests (Tegner & L y s h o l m , 1985). They measured performance of single leg hop for distance, running figure-of-eight course, spiral staircase run, and inclined slope run. Gauffin et al. (1990) was able to show an impairment in single-leg hop distance in the injured leg of A C L deficient patients.  They  37  noted that "the impaired performance was not correlated to reduced muscle strength." (Gauffin, Pettersson, Tegner, & Tropp, 1990).  38  Popular Hypotheses There are two popular hypotheses as to the mechanism of action of the A C L proprioceptive system. Most of the initial investigations attempted to demonstrate a direct ligament-muscular reflex in which cc-motoneurones supplying knee joint muscles were directly influenced by stimulation of the A C L .  In their 1986 study, Johansson et a l .  reviewed three early studies which indicated that skeletomotoneurones were stimulated by activity i n high threshold joint afferents, but not activity i n low-threshold joint afferents (Eccles & Lundberg, 1959; Holmquist, 1961; Holmquist & Lundberg, 1961).  This  conclusion was also reached by Solomonow et al. in 1987. They found that only high-load direct stimulation of the feline A C L resulted in reflex quadriceps and hamstring activity. L o w and moderate loads resulted in no activity.  Lundberg et al. (1978) was able to  demonstrate evoked potentials in oc-motoneurones in 1/3 of the spinalized cats to which he applied low-threshold stimulation to the P A N of the knee. The idea of an "on demand" ligamento-muscular reflex arc is "supported by the fact that most of the mechanoreceptors found in the A C L were concentrated near the insertions of the ligament to the bones." (Solomonow, Baratta, Shoji, Bose, Beck, & D'Ambrosia, 1987) This area becomes strained when high loads are applied to the ligament, while the more viscoelastic midportion of the ligament provides resistance to deformation at low and moderate loads. In 1990, Pope et al. attempted to elicit quadriceps and hamstring E M G responses in anaesthetized cats by loading the A C L , but were unable to find any responses.  As  previously discussed, they concluded that traction on the A C L did not result in direct monosynaptic reflexes even though sensory afferents were stimulated. Johansson, i n his 1991 review notes that "viewing the joint receptors as triggers o f protective  reflexes  that  are  elicited  only  when  the  joint  is  threatened  overextension/overflexion loads leads to considerable conceptual problems,  by  because  39  ligamento-muscular protective reflexes do not seem to be able to act i n time to protect the ligaments from injury unless the threatening event is very slow." (Johansson, Sjolander, & Sojka, 1991b) Difficulties in demonstrating ligamento-muscular reflexes have lead investigators to consider a second hypothesis regarding the mechanism of joint proprioception.  This  second hypothesis, commonly referred to at the y-loop hypothesis, was first suggested by Freeman & W y k e , i n 1967, who studied E M G response to the effects of passive movement of the feline ankle joint. They proposed that "articular mechanoreceptor reflexes operate polysynaptically by way of the y-motoneurone loop: that they are significantly involved in the normal reflex coordination of muscle tone in posture and movement; and that such reflexes are likely to become disordered in the presence of capsular lesion of joint." (Freeman & W y k e , 1967a) They noted that discharges from cutaneous mechanoreceptors have been shown to influence y-motoneurone activity and felt it was not unreasonable for joint mechanoreceptors to have a similar mechanism o f action. Pope et al. (1990) after failing to find E M G responses i n the cat quadriceps and hamstring muscles with loading the A C L made the following statement.  "Increasing  evidence supports a more subtle modulatory effect of joint afferents on motoneurone output and eliciting a robust reflex response to stimulation of ligamentous receptors in the anaesthetized animal may not reasonably reflect physiologic function." Appelberg et al. (1979) demonstrated  indirect evidence that joint  receptors  influenced the y-loop system by measuring increased muscle spindle afferent activity from the triceps surae while applying pressure to the contralateral knee joint capsule. They then were able to abolish the response  by infusing the capsule with local  anaesthetic.  (Appelberg, Hulliger, Johansson, et al., 1979) Johansson et al. (1986) measured the effects of 71 single lumbar y-motoneurones, evoked by graded electrical stimulation of fibres i n the P A N of the feline knee and by direct ligament loading. They found that y-motoneurones demonstrated evoked potentials to l o w  40  and moderate loads on the A C L (between 5 and 40N). This is i n contrast to loads of 1 3 0 N required to affect a-motoneurone activity. (Solomonow et al., 1987)  Johansson et a l .  concluded that "the findings seem to support the idea, as suggested by Freeman & W y k e (1967) that the joint receptors may contribute to the coordination of muscle tone in posture and movement via the y-loop." They continued by suggesting that the y-loop mechanism may serve to regulate joint stiffness and stability. (Johansson et al., 1986) Sjolander et al. (1989) agreed that the cruciate ligaments may play an important sensory role via the reflex actions of the y-spindle system. They went on to speculate that "the most likely candidates among the receptors to give the above mentioned effects are Ruffini and/or perhaps golgi tendon organ-like endings," both of which have been found in the A C L Miyatsu et al. (1993) found that A C L loading had an excitatory effect on thigh muscles of unanaesthetized decerebrate-spinalized cats and dogs.  They found that the  excitatory effect on thigh muscles is via a multi-motoneurone output, and that the P A N is one of the afferent routes from the mechanoreceptors of the A C L . They also found that the A C L load producing the maximum E M G discharge was less than the animals' body weight, which "suggests that the levels o f thigh muscle tone could be altered by loads within the physiological range." (Miyatsu et al., 1993) Another finding of interest was that there is a variability in the delay between A C L loading and muscle response both between animals and between experiments on the same animal. These results lead the investigators to conclude that "the receptor afferents from the A C L do not act on alpha-motoneurones." (Miyatsu et al., 1993) Appelberg (1983) had a similar view of the role of the y-muscle-spindle system in the regulation of joint stability which he called "the final common input" hypothesis. This hypothesis states that the muscle spindles are mediated not only by muscle length, but in addition, to a large extent, by signals from descending pathways and by both ipsilateral and contralateral peripheral nerves. The y-motoneurones integrate the descending messages and  41  peripheral receptor information and transmit them to the muscle spindles where final adjustments are made according to the ongoing length-tension changes of the parent muscle. (Appelberg, Hulliger, Johansson, & Sojka, 1983)  42  Conclusion  The complex nature of the proprioceptive system makes it difficult to determine the contribution that any one structure or group of structures may make.  Information from  peripheral receptors is sent to many centres of the C N S , reaching as far as the cerebral cortex and the cerebellum. Communications between these centres compare and modify the information.  Efferent signals are sent to the periphery via both alpha and gamma  motoneurones, and their responses are in turn affected by spinal reflexes.  Finding out  what deficits might result from the loss of specific joint structures such as the A C L therefore becomes very difficult. The fact that neurological receptors within the joints and joint ligaments do send impulses to the spinal cord and to higher centres in the C N S has been clearly shown. Investigations trying to reveal a direct myotatic reflex response to stimulation of the A C L have been inconclusive. A more promising model for understanding the proprioceptive role of the A C L arises from the y-loop hypothesis. This hypothesis has suggested possible mechanisms i n which neurological information from the A C L may play a significant role i n the modulation of knee joint control and proprioception.  The use of such a model is  important i n determining the possible consequences and relevance of the proprioceptive loss following A C L disruption. This loss of proprioception following knee joint ligament injury might help account for the poor correlation between mechanical stability of the knee and a patient's functional stability or ability to perform high level activities such as cutting and turning.  The  proprioceptive deficit might result in a lack of muscular protection to the joint (possibly due to reduced sensitivity of the muscle spindles) which in turn may predispose the patient to further ligamentous injury or accelerated degenerative changes. This idea that the proprioceptive loss is a cause of joint degeneration and not the result of it, is beginning to be considered by more and more investigators. The destructive  43  changes seen in Charcot's Joints in which there is a loss in proprioception, but not pain sensation, seem to support this view.  Other sensory neuropathies i n which patients  maintain good joint position sense, but lose the sensation of pain do not result in joint destruction. In conclusion, it can be seen that further research is needed to more clearly identify the mechanisms in which joint mechanoreceptors affect proprioception, and the changes that result following disruption of this information.  44  Chapter Three DEFINITION OF T E R M S  1. A C L deficient  A condition in which the anterior cruciate ligament has been completely ruptured, and has not been surgically repaired or reconstructed.  2 . A C L reconstruction  A surgical procedure which attempts to restore ligament integrity following anterior cruciate ligament disruption. In this study, the A C L reconstructions examined w i l l be intra-articular procedures utilizing semitendinosus/ gracilis tendons.  3 . Isolated A C L rupture  A complete tear of the anterior cruciate ligament that is not associated with other ligamentous, capsular, mensical or bony injury.  4 . Laxity  A general term describing slackness or lack of tension in a ligament or looseness of a joint. Laxity may be normal or abnormal (e.g. following ligamentous injury). (Staubli & Jakob, 1992)  5. Arthrometer  A n instrument that measures relative laxity of a joint  6. Instability  A clinical sign: a condition of increased joint motion or mobility due to ligament injury. A symptom: a giving-way event during activity. (Feagin, 1988)  7. Functional stability  The condition in which the joint is stable and does not give symptoms during physical activity (Johansson et al., 1991b)  8. Mechanoreceptor  A sensory receptor i n the body which responds to mechanical deformation. The discharge rate is directly related to the intensity of the mechanical force applied to the receptor.  9. Proprioceptor  A n y of the sensory nerve endings that give information concerning movements and position o f the body" (Dorland's Medical Dictionary 22ed., 1977) Proprioceptors include both joint receptors and extra-articular receptors.  10. Proprioception  The ability to discern movements and position of the body  11. Joint position sense  The ability to accurately determine a resting position of a joint when only proprioceptive feedback is allowed.  45  12. Joint movement sense  The ability to determine when a joint is being moved from a resting position. It is usually measured with passive movement at a constant speed of 0.5 degrees per second.  13. Concentric muscle contraction  A muscular contraction that results i n the origin and insertion of the muscle becoming approximated. (Gould, J. A . & Davies, G . J . , 1987)  14. Eccentric muscle contraction  A muscular contraction that occurs while the origin and insertion o f the muscle are moving away from each other. (Gould, J. A . & Davies, G . J., 1987)  15. Isokinetic  A concentric or eccentric contraction that occurs at a set speed and used a resistance that accommodates to the force produced at all points in the range of motion. (Gould, J. A . & Davies, G . J . , 1987)  46  Chapter Four METHODOLOGY  Subjects Three groups of twenty volunteers were chosen for this study. Normal Control  Group  2)  They were:  A C L Deficient (Conservative Group),  and  1)  3) A C L  Reconstructed (Surgical Group). Subjects were chosen based on the following criteria. 1) The control group consisted of twenty healthy volunteers, male and female, between the ages of 18 and 40 years, who have no history of injury or osteoarthritis in either knee. 2) The conservative group consisted of twenty subjects who had suffered an isolated unilateral A C L rupture greater than 8 months prior to their involvement in the study. The majority of these subjects were clinically diagnosed by a physician from the A l l a n M c G a v i n Sports Medicine Centre. The remaining subjects were clinically diagnosed by a physician from the N e w West Orthopaedic and Sports Medicine Centre. A l l subjects in this group had successfully completed a physiotherapy rehabilitation program and were at a functional level which allowed successful completion of all tests. Subjects were excluded i f they had previously injured either A C L , previously had knee surgery, or demonstrated evidence of osteoarthritis of either knee. 3) The surgical group consisted of twenty subjects who had been surgically treated more than 12 months previously for an isolated unilateral A C L rupture (confirmed at surgery). A l l surgical procedures were performed by one surgeon. Subjects i n the surgical group followed the standard physiotherapy rehabilitation protocol at the Allan M c G a v i n Sports Medicine Centre. Subjects were excluded from this group i f they had previously injured  either A C L , previously had knee  osteoarthritis i n either knee.  surgery,  or  demonstrated  evidence of  47  Subjects were excluded from any group i f they had a history of central nervous system or lower extremity peripheral nervous system pathology.  48  Surgical Procedure The surgical technique used was similar to that described by Gomez et al. (1990). In this technique, the ipsilateral semitendinosus tendon is dissected proximally, but left undisturbed distally. A drill hole is placed through the proximal tibia so that the remaining fibres of the A C L w i l l surround it. The semitendinosus graft is threaded through the drill hole and the remaining fibres of the A C L . The resulting ligament/tendon complex is then passed through the posterior capsule of the knee and attached to the lateral intramuscular septum in the over the top fashion.  The idea of this surgical technique is that the  semitendinosus graft acts as a splint and direction finder for the torn ligament ends.  It is  also believed that the A C L fibres covering the graft w i l l provide early blood supply to vasularize the graft. Finally, this technique may spare proprioceptive nerve endings in the A C L fibres, which would be otherwise lost with other surgical techniques (Gomez et a l . , 1990)  49  Testing Procedures Objective outcome measures can be discussed in four groups. proprioceptive acuity, 2) ligamentous laxity, 3) muscle torque,  These are: 1)  and 4) functional  performance. Each of these groups w i l l be discussed separately. Proprioceptive Acuity: Knee joint position sense was measured using the technique o f Barrett et a l . (1991a), i n which the subject is positioned supine with one leg supported in a Thomas Splint (with Pearson knee flexion piece attached). The knee was shielded from view of the subject and passively moved to ten predetermined positions. The subject was asked to reproduce each position using a visual analogue model which incorporated a goniometer for recording the subject's perceived angle of flexion.  A measurement of inaccuracy was  determined by finding the difference between the perceived angle and the actual angle of flexion. This measurement has been shown to be reliable and valid (Barrett et al., 1991a), and has been used to demonstrate a difference between A C L intact, A C L deficient and A C L reconstructed subjects (Barrett et al., 1991b). Anterior Tibial Displacement: Anterior tibial displacement on the femur was measured with the knee positioned at 20° flexion using the K T 1 0 0 0 Knee Ligament Arthrometer (MedMetric Corporation, San Diego, C A . ) .  Testing procedure followed a standardized protocol described by Daniel et  al, (1985). Subjects were positioned in supine lying during measurement  A n 11 cm  support was placed under the knee to obtain approximately 20° of knee flexion, and a foot support was used to hold both legs in neutral rotation and 15° abduction. The arthrometer was strapped to the lower leg so that the force handle was located 10 cm distal to the joint line. One sensor pad was positioned over the tibial tubercle, and the second pad over the  50  patella.  Measurements were taken at 134 N (30 lbs.) and at a maximal manual force  ( M M T ) . Three trials were performed for each test, and the average of these was recorded. The technique used closely approximates the Lachman procedure which has been shown to be reliable and valid i n determining A C L insufficiency (Katz, & Fingeroth, 1986). The KT1000 arthrometer has been tested for reliability by several authors.  Hanten  and Pace (1987) found reliability coefficients of r=0.92 and 0.84 for inter-examiner and intra-examiner reliability respectively. Malcom et al (1985) found that 9 3 % of their retest measurements of unilateral A C L disruption were within 2 m m or less. The mean variation between two examiners was found to be 1.2 mm. The K T 1 0 0 0 arthrometer is sensitive within a 1 mm range (± 0.5 mm). Muscle Torque Muscle torque  was  measured  Dynamometer (Medec, Canada).  using the  Kinetic  Communicator  (KinCom)  Both quadriceps and hamstring muscle groups were  tested. Peak torque was measured during the concentric and eccentric phases of muscle contraction at a velocity of 180 degrees per second. In addition, the hamstring:quadriceps ratio was computed for the concentric phase of muscle contraction.  The following test  protocols were performed: 1.  Left Quadriceps at 1807s  2.  Left Hamstring at 1807s  3.  Right Quadriceps at 1807s  4.  Right Hamstring at 1807s  The order of testing was randomized by side and muscle group for each subject. Subjects were given a standardized warm up (stair climbing) and verbal instructions regarding testing protocol and the use of the K i n C o m dynamometer.  Once the subject was  familiar with the procedure, they were seated on the K i n C o m with their pelvis and tested thigh strapped to the bench. The axis of motion of the K i n C o m was aligned with the lateral  51  femoral condyle of the tested knee, and the force arm positioned such that its most distal aspect was no further from the knee joint than 75% of the length of the fibula. A l l tests w i l l be performed between 15 and 90 degrees o f knee flexion. Gravity compensation was on during all tests. Once positioned, subjects were given a practice trial for both tests on that side. Practice trials consisted o f four repetitions, three o f which were performed submaximally followed by one which was performed with maximum effort.  After a 3 minute rest  interval, subjects were asked to repeat the two tests with maximal effort on all four repetitions. Test results were saved onto a floppy disc, and the procedure repeated for the opposite leg. Functional Performance: The two functional performance tests used for this study were a single leg hop for maximum distance ( S L H D ) , and a timed 6 metre single leg hop ( S L H T ) .  Barber et a l .  (1990) showed that with both of these tests, 90% of a normal population had a symmetry index o f 85% or above. These two single leg hop tests also had greater sensitivities for A C L deficient subjects than either a vertical jump test or shuttle running (with or without pivoting). Noyes et al. (1990) demonstrated that the single leg hop for distance and the timed single leg hop tests were also able to show greater differences between normal and A C L deficient subjects than a triple hop for distance or a cross-over hop test. T o perform the single leg hop for distance test, the subject first stood on one limb with their hands clasped behind their back. They then hopped as far as possible and landed on the same limb. The distance hopped was measured and recorded. Each limb was tested three times. A symmetry index was determined by dividing the mean score of the involved leg by the mean score of the uninvolved leg and multiplying by 100. For the timed single leg hop, a distance of 6 metres was measured.  The subject  was instructed to begin standing on one leg and hop on that leg as quickly as possible past  52  the 6 metre mark. The test was repeated three times for each leg and a symmetry index was calculated by dividing the mean of the uninvolved leg by the mean o f the involved leg and multiplying by 100. A l l tests were performed in a standardized physical environment. Subjective Information The following subjective information was gathered for all subjects: 1. Age 2. Gender 3. Knee Involved 4. Date of Injury 5. Date of Surgery In addition, subjects were asked to complete four subjective evaluations to assess their pre and post injury activity level, change in sport involvement, and functional outcome. The Noyes Sports Activity Rating Scale (Noyes et al., 1989) and the Tegner & Lysholm Activity Score (Tegner & Lysholm, 1985) were used to assess subjects' past and present activity levels. The Change i n Sport Level questionnaire (Noyes et a l . , 1989) was completed by the two injured groups. It was used to assess what effect the injury had on their level of sport involvement. Finally, the Lysholm Knee Scoring Scale (Lysholm & Gillquist, 1982) was used to compare subjects' own assessment of their knee function between groups. Examples of the above subjective scales are included i n appendix 1.  53  Experimental Design and Analysis of Data A three (group) by ten (outcome measurements) prospective quasi-experimental design was used (see Table 4.1). This design allowed testing of the following hypotheses: H I 1:  There is a significant difference among groups in proprioceptive acuity.  H21:  There is a significant difference among groups in ligamentous laxity.  H31:  There is a significant difference among groups i n muscular strength.  H41:  There is a significant difference among groups in functional performance.  H51:  Within the control group, there is a linear relationship among muscle strength, ligament laxity and proprioception to functional skill performance.  H61:  Within the A C L deficient group, there is a linear relationship among muscle strength, ligament laxity and proprioception to functional skill performance.  H71:  Within the A C L reconstruction group, there is a linear relationship among muscle strength, ligament laxity and proprioception to functional skill performance.  a  o  SLHT  c  Ham:Quad Ratio  Quad Ecc'  S  SLHD  Function  Strength  Quad Con  KTIOOO (MMT)  Ligament Laxity  KTIOOO (133N)  Joint Position Sense  Table 4.1: Study Design M o d e l Proprioception  Control Group Conservative Group Surgical Group  Statistical analysis began by determining which of the functional tests was able to show the greatest differences between groups.  Pearson correlation coefficients were then  54  calculated for each of the two ligament laxity measurements and five strength measurements to determine which were most closely correlated to the chosen functional test. The single laxity test and strength test with the highest correlation to the chosen functional test were used for subsequent regressional analyses. Between group comparisons were performed for each of the areas measured (proprioceptive acuity, ligamentous laxity, muscle torque, and functional performance) using analysis of variance ( A N O V A ) to answer the following null hypotheses.  Post hoc  analyses to determine significant differences between individual groups were done using Tukey's H S D tests. H l g : There is no significant difference among groups i n side-to-side proprioceptive acuity. H 2 q : There is no significant difference among groups i n either of the anterior displacement tests. H3q: There is no significant difference among groups in any of the peak torque measurements. H 4 q : There is no significant difference among groups in either of the functional performance tests. Linear regressional analyses were performed to produce regressional equations for each of the three groups indicating the relative contribution of proprioceptive acuity, ligamentous laxity and muscular torque in the performance of the chosen functional test. In the case of anterior tibial displacement and muscle torque, where there was more than one measurement, only the single measurement  which correlated most closely (Pearson  correlation coefficient) with the chosen functional test was used. Significance for all statistical measures was accepted at the p < 0 . 0 5 level.  55  Chapter Five Subjective Results  Descriptive Data Table 5.1 summarizes the descriptive characteristics of subjects i n each of the three groups tested.  Table 5.1 Descriptive Data of Subjects by Group Group  Gender  Conservative  Female - 9 Male -11 Female - 1 3 Male-7  Surgical Control  Female - 1 0 Male - 1 0  Age (years) (x ± S D ) 26.5 ± 7 . 5 29.9 ± 1 0 . 0 25.1 ± 4 . 1  Knee Involved Left - 12 Right - 8 Left-11 Right - 9 N/A  Months Post Surgery/Injury ( x ± SD) 39.7 ± 44.4 23.3 ± 8.0 N/A  56  Subjective Results  Noyes Sports Activity Rating Scale The pre-injury Sports Activity Rating Scale results for the Conservative Group show 9 of 20 subjects fell within Level I, while the remaining 11 fell within Level II. In the Surgical Group 10 of 19 subjects scored within Level I and 9 scored within Level II. In the Control Group, 10 subjects fell within Level I and 10 within Level II. N o subjects scored below Level II i n any of the three groups before injury (Table 5.2).  Analysis of  Variance showed no significant differences in average rating among the Conservative and Surgical Groups pre-injury values and the Control Group values.  Table 5.2 Noyes Sports Activity Rating Scale Conservative Group (n=20)  Response Counts Level I (4-7 days/wk) 100 95 90 Level I Total Level II (1-3 days/wk) 85 80 75 Level II Total Level I V (no sports) 50 Level TV Total  A by Level  Present  -2  3 3 4 10  5 4 1 10  + 1  4 2 4 10  1 1  + 1  0 0  3.4** (11.9)  87.3 (8.7)  A by Level  Pre  -6  4 4 2 10  2 3 3 8  3 7 3 13  + 2  3 5 1 9  4 4  + 4  0 0  Pre  Post  7 2 0 9  1 1 1 3  5 6 0 11 0 0  89.8 74.3* Group Mean (8.8) (18.7) (SD) *, ** significant difference (p < 0.05)  Control Group (n=20)  Surgical Group (n=19)  15.5** (19.9)  88.9 (8.4)  Post  85.3* (10.9)  The post-injury Sport Activity Rating Scale results for the Conservative Group show 3 subjects within Level 1,13 subjects within Level II and 4 subjects within Level I V .  57  The Surgical Group's results show 8 subjects scoring in Level I, 10 subjects in Level II and only one subject scoring in Level I V . The average score for the Conservative Group post injury was significantly lower than that of the Surgical Group post surgery (p < 0.05).  Sports Activity  Rating  Scale  24 22 20  Surgical Group  Conservative Group  Control  1 8 1 6 1 4  a Level IV  1 2  B Level II  1 0  • Level I  8 6 4 2  _i  0  ^  1_  Pre  Post  Pre  Post  Present  Injury  Injury  Injury  Injury  Level  Figure 5.1 Noyes Sports Activity Rating Scale Pre and Post Injury/Surgery  Tegner & Lysholm Activity Score Pre-injury results of the Activity Score show that 17 (85%) of the Conservative Group scored 7 or higher, while 3 (15%) scored between 5 and 6. In the Surgical Group 13 (68%) scored 7 or higher, 5 (26%) scored between 5 and 6, and 1 (5%) scored at or below 4. In the Control Group 8 (40%) scored 7 or higher, 5 (25%) scored between 5 and 6, and 7 (35%) scored at or below 4 (Tables 5.3 & 5.4). The post injury Activity Score results for the Conservative Group showed 8 (40%) scoring 7 or higher, 4 (20%) scoring between 5 and 6, and 8 (40%) scoring at or below 4 .  58  Table 5.3 Tegner & Lysholm Activity Score (Response Counts) Surgical Group Conservative Group (n=20) (n=19) Pre Post Pre Post Injury Injury Injury Surg. Score  8 2 •7 3 0 0 0  9  8 7 6 5 4 3  3 0 5 2 2 4 4  7.8* Group Mean 5.6f (SD) (1.2) (2.1) *, **, t = significant difference (p < 0.05)  Control Group  (n=20)  Present Level  6 2 2 6 0 2 1  7 3 3 5 0 1 0 7.5** (1.5)  3 1 4 2 3 7 0 5 9* **  6.95f (1.9)  d'.9)  The Surgical Group's post surgery results showed 10 (53%) scoring 7 or higher, 6 (32%) scoring between 5 and 6, and 3 (16%) scoring at or below 4. Statistical analysis o f the average pre-injury Activity Score showed the Control Group scored significantly lower (5.9 ± 1.9) than either the Conservative Group (7.8 ± 1.2) or the Surgical Group (7.6 ± 1.5). There was no significant difference between the two injured groups.  The average Conservative Group score post injury was significantly  lower than the average post surgery score of the Surgical Group.  Table 5.4 Tegner & Lysholm Activity Score (Ranges) Subjects Scoring within Specified Range (n(%)) Control Group Surgical Group Conservative (n=20) (n=19) Group (n=20) Present Level Pre Post * Pre Post Scoring Range >7 5-6 <4  17 (85) 3(15) 0 (0)  8 (40) 4(20) 8(40)  13 (68) 5 (26) 1 (5)  10(53) 6 (32) 3(16)  ,  8(40) 5(25) 7(35)  59  Activity Score (Tegner & Lysholm) 24 22 20  Conservative  Grou|  Surgical  Group  Control  1 8 1 6 |D£4  1 4 1 2  I 5 or 6  1 0  l>7  8 6 4 2 •  0  1  I  1  1  1  Pre  Post  Pre  Post  Present  Injury  Injury  Injury  Surgery  Level  Figure 5.2 Tegner & Lysholm Activity Scores Pre and Post Injury/Surgery  Change in Sport Level Table 5.5 shows the results of the Change in Sport Level.  Three subjects in the  Conservative Group reported no change in their sport level since injuring their knee, and having no or slight symptoms.  Ten subjects in the Surgical Group reported the same  results. Three subjects in the Conservative Group and 5 subjects in the Surgical Group had decreased their sport level, but had no symptoms. Thirteen subjects i n the Conservative Group experienced moderate to significant symptoms while playing at the same or decreased level of sport.  Only one member of the Surgical Group was playing on a  symptomatic knee. One subject in the surgical group was unable to participate in their sport activity for reasons related to their knee. Three subjects in the surgical group decreased their sport level for reasons unrelated to their knee.  60  Table 5.5 Change i n Sport Level Surgical GrouD  Conservative Group Same Level; N o Symptoms  3  10  Decreased Level; N o Symptoms  3  5  13  1  Unable to Play; Related to Knee  0  1  Decreased/Unable to Play; Unrelated to Knee  0  3  Symptomatic; Same or Decreased Level  Change In Sport Level by Treatment Group 20 1 8  Conservative  Group  16 1 4  Surgical  Group  1 2  • Not Related to Knee  1 0  a Moderate/Sig. Problems • No/Slight Problems  8 6 4 2 0  •a a> w al  2a £a.  £ o D  Figure 5.3 Change in Sport Level and Associated Symptoms  Lysholm Knee Scoring Scale (Table 5.6) There was a significant difference in subjective functional assessment using the Lysholm Knee Scoring Scale. The Conservative Group scored significantly lower than the  61  Control Group and the Surgical Group (p < 0.05).  There was no difference between the  Surgical Group and the Control Group scores.  Table 5.6 Lysholm Knee Scoring Scale Conservative Group (n=20)  Surgical Group (n=14)  Control Group (n=20)  97.2* (6.15)  96.6** (2.65)  Lysholm Knee Scoring Scale 78.4* ** Mean (14.01) (SD) *, ** = significant difference (p < 0.05)  L  110-  y  s iooi h  :  0  •  90  ^  ^  ^  ^  o  1  m  K n e e S c o r e  m  B •  60•  50-  40  •  Conservative  Control  Surgical  Group Figure 5.4 Average Lysholm Knee Scoring Scale vs. Groups  62  Objective Results  Proprioceptive Inaccuracy Analysis of variance demonstrated a significant difference (p = 0.04) among groups in proprioceptive inaccuracy (injured leg - uninjured leg).  Tukey's H S D showed a  significant difference between the conservative and control groups, and between  the  conservative and surgical groups (p < 0.05). There was no significant difference between the surgical and control groups.  There was no difference in uninjured leg proprioceptive  inaccuracy among the groups (p = 0.94) (see Table 5.7).  Table 5.7 Conservative Group degrees ( x ± S D ) 15.96 ± 7.13 Injured/Right 12.37 ± 6.48 Uninjured/Left 3.59 ± 4.44* ** Difference (I-N) *, ** = significant difference (p < 0.05)  i.  Surgical Group degrees ( x ± S D ) 11.38 ± 8.21 11.56 ± 8 . 6 4 -0.19 ± 5 . 0 2 *  10  o  CO  t_ O  o  CO  c  CD > Q0) o o  l_  CL O  a.  Conservative  Control  Surgical  Group Figure 5.5 Proprioceptive Inaccuracy by Groups  Control Group degrees ( x ± S D ) 12.08 ± 7 . 1 0 12.06 ± 7 . 1 6 0.02 ± 3.65**  63  Anterior Displacement (KTTOOO) There was a significant difference (p < 0.001) among groups i n K T 1 0 0 0 anterior displacement (injured - normal knee) at both the 134N (30 lbs.) test and the manual maximum test ( M M T ) . Tukey's H S D showed a significant difference between all group pairs at both 134N and M M T (see Table 5.8). Results were graded as either excellent (< 3mm), acceptable (3 - 5mm) or poor (> 5.5mm). The conservative group included 2 (10%) excellent results, 9 (45%) acceptable results, and 9 (45%) poor results at both 134N and M M T .  A t 134N the surgical group  included 15 (75%) excellent, 3 (15%) acceptable, and 2 (10%) poor results.  With the  M M T the surgical group included 15 (75%) excellent, 4 (20%) acceptable and 1 (5%) poor result. The control group all scored excellent results.  Table 5.8 KT1000 Anterior Displacement (Injured minus contralateral normal knee) Control Group Surgical Group Conservative Group (mm) (mm) (mm) K T 1 0 0 0 @ 134N n < 3 (excellent) 3 - 5 (acceptable) > 5 (poor) Mean±SD  20 2 9 9 4.85 ± 2.73*  20 15 3 2 2.10 ± 2 . 5 0 *  20 20 0 00 -0.73 ± 0.88*  KT1000 @ M M T 20 n 2 < 3 (excellent) 9 3 - 5 (acceptable) 9 > 5 (poor) Mean±SD 5.48 ± 2.85* * = significant difference (p < 0.01)  20 15 4 1 2.10 ± 2.67*  20 20 0 0 -0.75 ± 0.88*  64  1 o-  co  ^  •  •  •  •  •  •  •  Conservative  Control  Surgical  01  o p\ o  Group Figure 5.6 Anterior Displacement (KTIOOO @ 134N) by Groups  1  o-  o o o  o o  r  o-  Conservative  Control  Surgical  Group Figure 5.7 Anterior Displacement (KTIOOO @ M M T ) by Groups  65  Strength ( K i n C o m Dynamometer) A l l strength values were peak average torque measurements made at 180°/s. Symmetry Indexes for the conservative group and surgical group were calculated by dividing the injured leg peak average torque by the uninjured leg peak average torque and multiplying the quotient by 100. The symmetry index for the control group was calculated by dividing the peak average torque o f the right leg by that o f the left leg and multiplying the quotient by 100.  Table 5.9 Strength (KinCom): Peak Average Torque (Nm) and Symmetry Indexes Conservative Group Surgical Group Control Group 1807s (x±SD) (x±SD) (x±SD) Concentric Quadriceps 116.42 ± 36.06 110.90 ± 34.17 127.26 ± 48.00 Injured/Right 112.27 ± 32.71 124.70 ± 41.98 138.21 ± 55.18 UninjuredVLeft 106.11 ± 25.38* 90.00 ± 13.75* 95.26 + 19.98 Sit Eccentric Quadriceps 174.00 ± 55.70 164.74 ± 62.04 160.35 ± 51.52 Injured/Right 173.11 ± 51.25 167.85 ± 54.40 183.47 ± 66.59 UninjuredVLeft 102.26 ± 20.46 97.60 21.73 90.32 21.22 ± ± sit Concentric Hamstring Injured/Right Uninjured/Left  Sit Eccentric Hamstring Injured/Right Uninjured/Left  Sit Hamstring/ Quadriceps Ratio Injured/Right Uninjured/Left  sit  82.47 + 29.05 86.42 ± 30.35 97.63 ± 21.36 97.79 ± 35.98 104.58 + 34.70 94.84 ± 22.49* 65.92 62.67 106.89  ± 19.44 ± 15.45 ± 24.29  70.45 + 21.18 74.25 ± 21.56 95.35 ± 16.05*  79.95 + 26.73 72.84 ± 22.57 109.90 ± 14.83*  90.25 91.45 99.00  ± ± ±  27.70 25.88 16.66  100.79 91.37 110.26  ± ± ±  34.69 28.48 13.42*  64.99 61.93 108.25  ± ± ±  14.94 15.54 24.32  67.25 67.52 108.53  ± ± ±  26.67 18.79 27.36  t = Symmetry Index (SI) [Injured/Uninjuredjx 100 * = significant difference (p < 0.05)  66  Concentric Quadriceps There was a significant difference (p < 0.05) between the surgical and control groups i n the concentric quadriceps symmetry index. However, there was a large right/left leg difference in the control group with the left leg being 94% as strong as the right leg. There was no difference between the conservative and surgical groups or between the conservative and control groups.  There was no significant difference among groups for  either the injured or uninjured legs.  180 1601 1401 co o O •o  a3  1201 1001 801 601 40  Conservative  Control  Surgical  Group Figure 5.8 Concentric Quadriceps Torque (Symmetry Index) by Groups  67  Eccentric Quadriceps There was no difference among groups in eccentric quadriceps symmetry index. There was no difference among injured legs, and no difference among uninjured legs.  160-150140" 130"  •  60-  50-  1  1  Conservative  1  Control  Surgical  Group Figure 5.9 Eccentric Quadriceps Torque (Symmetry Index) by Groups  68  Concentric Hamstring There was a significant difference (p < 0.05) between the surgical and control groups in the concentric hamstring symmetry index. However, there was a large right/left leg difference in the control group with the left leg being 9 1 % as strong as the right leg. This difference is greater than the differences for either of the two injured groups. was no difference between the conservative and surgical groups conservative and control groups.  or between  150140130-  :  •  »  70605  0  the  There was no significant difference among groups for  either the injured or uninjured legs.  80-|  There  J  , Conservative  , Control  Surgical  Group Figure 5.10 Concentric Hamstring Torque (Symmetry Index) by Groups  69  Eccentric Hamstring There was a significant difference (p < 0.05) between the conservative and control groups in the eccentric hamstring symmetry index. However, there was a large right/left leg difference in the control group with the left leg being 9 1 % as strong as the right leg. This difference is greater than the differences for either of the two injured groups.  There  was no difference between the conservative and surgical groups or between the surgical and control groups.  There was no significant difference among groups for either the  injured or uninjured legs.  140  co o o  LU  E CQ  Conservative  Control  Surgical  Group Figure 5.11 Eccentric Hamstring Torque (Symmetry Index) by Groups  70  Hamstring/Quadriceps Ratio There was no difference among groups in hamstring/quadriceps ratios. no difference among injured legs, and no difference among uninjured legs.  1.8 1.6i  1.4 c o O  1.2  TJ CO  q c o  0.8 E co  0 1  0.6 0.4  T Conservative  r Control  Surgical  Group Figure 5.12 Concentric Hamstring:Quadriceps Ratio (Inj./Uninj.) by Groups  There  71  Functional Performance The single leg hop for maximum distance ( S L H D ) symmetry index was calculated for the injured groups by dividing the injured leg average hop distance by the uninjured leg average hop distance and multiplying the quotient by 100. In the control group, the right leg average hop distance was divided by the left leg average hop distance and the quotient multiplied by 100.  The timed six metre single leg hop ( S L H T ) symmetry index was  calculated for the injured groups by dividing the uninjured leg average hop time by the injured leg average hop time and multiplying the quotient by 100. It was calculated for the control group by dividing the left leg average hop time by that of the right leg and multiplying the quotient by 100.  Table 5.10 Functional Performance (Single L e g Hop) Conservative Group (x±SD) Single L e g H o p for Distance ( S L H D ) Injured/Right 123.10cm ± 26.58 Uninjured/Left 134.02cm ± 25.31 Sit 91.70 ± 8.78*** Timed 6m Single Leg Hop (SLHT) Injured/Right 2.52s ± 0.39 Uninjured/Left 2.37s ± 0.34 SItt 94.25 ± 3.65* **  Surgical Group (x±SD)  Control Group (x±SD)  127.22cm ± 29.97 129.60cm ± 28.73 97.95 ± 7.08*  139.03cm ± 22.52 139.07cm ± 22.95 100.20 ± 4.74**  2.50s ± 0.45 2.47s ± 0.44 99.25 ± 6.00*  2.26s ± 0 . 3 1 2.29s ± 0.30 100.75 ± 2.95**  t = Symmetry Index (SI) [Injured/Uninjured]x 100 tt = Symmetry Index (SI) [Uninjured/Injured]x 100 *, ** = significant difference between pairs at p < 0.05  72  Single L e g Hop for M a x i m u m Distance ( S L H D ) Analysis of variance showed that there was a significant difference in the single leg hop for maximum distance symmetry index among the groups (p = 0.001). Tukey's H S D showed the conservative group scored significantly lower than the control group and the surgical group (p < 0.05). There was no significant difference between the surgical group and the control group (see Table 5.10).  115  11  ( H  1051  o  o  X _l CO  851 801 751 70  Conservative  Control  Surgical  Group Figure 5.13 Mean Single L e g Hop for Maximum Distance (Symmetry Index) by Groups  73  Timed Six Metre Single L e g Hop ( S L H T ) There was a significant difference in the timed six metre single leg hop symmetry index among the three groups (p < 0.001). Tukey's H S D showed the conservative group scored significantly lower than the control group and the surgical group (p < 0.05).  There  was no significant difference between scores of the surgical group and the control group (see Table 5.10).  115  11CH w 105-H c  CQ CD  2  10CH  1  85  Conservative  Control  Surgical  Group Figure 5.14 Mean Timed 6 Metre Single L e g Hop (Symmetry Index) by Groups  74  Determination of Individual Measurements for use in Regressional Analyses Regressional analyses have been used to determine the relative contribution o f proprioceptive inaccuracy, anterior displacement, and strength in the performance of the functional test. Three regressional analyses have been performed determining the effects of proprioceptive acuity, anterior displacement and strength on the performance of a functional skill. They are: 1) Conservative group (injured leg), 2) Surgical group (injured leg), and 3) Control group (combined left and right leg).  In the cases of function, anterior  displacement, and strength, where there was more than one test performed in each category, the single best test was determined as follows. Functional Test for Regressional Analyses The best functional test for regressional analysis was determined by choosing the test which was able to show the greatest difference between groups. The injured leg single leg hop for maximum distance produced a difference of 15.9cm between the control and conservative groups. This represented an 11.5% difference between the two groups.  The  injured timed six metre single leg hop produced a difference of 0.26s between the control and conservative groups. This represented a 10.4% difference between the two groups. The single leg hop for maximum distance ( S L H D ) was therefore chosen to be used i n the regressional analyses. Anterior Displacement Test for Regressional Analyses Pearson correlation coefficients between the S L H D and the K T 1 0 0 0 (134N), and between the S L H D and the K T 1 0 0 0 ( M M T ) were calculated for both the conservative group and the surgical group (see Table 5.11). Injured leg values were used i n calculating these coefficients. The K T 1 0 0 0 ( M M T ) was chosen as the best anterior displacement test since it resulted i n the single best Pearson correlation coefficient (r = -0.21, between S L H D and K T 1 0 0 0 ( M M T ) in the conservative group.  75  Table 5.11 Pearson Correlation Coefficients for Anterior Displacement and S L H D KTIOOO (134N)  SLHD  KTIOOO ( M M T ) -0.210* -0.037  0.089 -0.087  Conservative Group Surgical Group * = chosen anterior displacement test  Strength Test for Regressional Analyses Pearson correlation coefficients between the S L H D and each o f the five strength measurements were calculated for both the conservative and surgical groups (see table 5.12).  Injured leg values were used in calculating these coefficients.  The concentric  quadriceps measurement was chosen as the best strength test since it had the highest correlation with the chosen functional test (r = 0.71, between S L H D and the conservative group).  Table 5.12 Pearson Correlation Coefficients for Strength and S L H D SLHD  Quad C o n  Quad Ecc  Ham C o n  Ham Ecc  HamrQuad  Conservative Group Surgical Group  0.708* 0.614*  0.541 0.447  0.420 0.475  0.486 0.507  -0.357 -0.132  * = chosen strength test  76  Regressional Analyses Conservative Group The effects of proprioception (proprioceptive inaccuracy), anterior displacement (KTIOOO ( M M T ) ) , and strength (concentric quadriceps  peak torque) on functional  performance (single leg hop for maximum distance) in the conservative group were tested by regressional analysis.  A l l measurements used were of the injured leg.  variance indicated a significant whole model test (p = 0.007)(see Figure 5.15).  Analysis of Individual  effect tests found that quadriceps strength had a significant effect on the model (p = 0.002). Neither proprioceptive inaccuracy nor anterior displacement had significant effects on the model (see Figures 5.16 to 5.18).  SLHD Avg. (Inj./R)  Predicted  Figure 5.15 Whole M o d e l Regressional Analysis for Conservative Group (Injured Leg) (p = 0.007)  77  200  n—i—i—i—i—i—i—r 0 50 100 150 200 250 Quad Con (Inj./R) Leverage  Figure 5.16 Strength Effect for Conservative Group (Injured Leg) (p = 0.002)  Figure 5.17 Proprioceptive Inaccuracy Effect for Conservative Group (Injured Leg) (p = 0.82) 200  "i 1 1 5 10 15 MMT (Inj./R) Leverage  1  r 20  Figure 5.18 Anterior Displacement Effect for Conservative Group (Injured Leg) (p = 0.27)  78  Surgical Group The effects of proprioception, anterior displacement and strength  on functional  performance in the surgical group were tested by regressional analysis. A l l measurements used were of the injured leg. Analysis of variance indicated a significant whole model test (p = 0.04) (see Figure 5.19).  Individual effect tests found that quadriceps strength had a  significant effect on the model (p = 0.008). Neither proprioceptive inaccuracy nor anterior displacement had significant effects on the model (see Figures 5.20 to 5.22).  s  200  /  L H  175"  ..  D  A v  a /  )  '  ¥  /  / .  -  •  '/"  ' a  m /  »/*/." °  100/  n / R  o.  /  /  J  /  • = v  JO.  125"  1  / y'  .  150-  9  (  /  /o  '  7 5 "  /  /  /  9 1 *  / i i  / r  i  / /  D  /  50  1 50 SLHD  '  1  i  100  Avg. (Inj./R)  i  150  i  i  200  Predicted  Figure 5.19 Whole M o d e l Regressional Analysis for Surgical Group (Injured Leg) (p = 0.04)  79  s  200  L H 175" D  /  /  °  _--'"  A 150" V  g  i  ' ' ' ' '  ''i  125" u  (  i  100"  n i  o  t  75"  -  /  R )  /•  50  1 1 1 1 1 1 100 150 200 50 Quad Con (Inj./R) Leverage  I 250  Figure 5.20 Strength Effect for Surgical Group (Injured Leg) (p = 0.008) 200 L H 175" D  s  A 150" 9  -.  """•*»  V  o  —r '  •  __ .  125"  • —  •  T^-  1..  ( I 100" n i 75"  a  •  /'  R )  50  _  i 1 1 1 I I 5 10 15 20 25 5 0 Inaccuracy Mean (l/R) Leverage  1 30  35  Figure 5.21 Proprioceptive Inaccuracy Effect for Surgical Group (Injured Leg) (p = 0.55) 200" L H 175" D  s  9  -  \ '  A 150"  ""•o-  V  ' " '  • 125"  ( 100" 1 n i 75"  / R )  50  I I 5 MMT (Inj./R)  1 1 10 Leverage  1 15  1  20  Figure 5.22 Anterior Displacement Effect for Surgical Group (Injured Leg) (p = 0.52)  80  Control Group For the control group left and right leg data were combined for the regressional analysis. The whole model analysis o f variance again showed a significant whole model effect (p = 0.007) (see Figure 5.23).  Strength was the only individual effect which was  significant (p = 0.007) (see Figures 5.24 to 5.26).  180  170160150"  v  •  y  140130"  X  y  s  •/ / / •  120•  110" S  /  *  t  **  m  •  /  */  *  """"  "  m  •  i  100"  1 1  •  1  90  90  I r i i i i i i 100 110 120 130 140 150 160 170 180  SLHDAvg.  Predicted  Figure 5.23 Whole M o d e l Regressional Analysis for Control Group (Left & Right Legs) (p = 0.007)  81  n  r  50 100 Quad Con Leverage  150  200  Figure 5.24 Strength Effect for Control Group (Left & Right Legs) (p = 0.007) s L H D  1 9  °-  180" 170160-  10090'  ~i—r 1—i—i—i—i—i—r 25 0 5 10 15 20 Inaccuracy Mean Leverage  Figure 5.25 Proprioceptive Inaccuracy Effect for Control Group 0-eft & Right Legs) (p = 0.41)  4 5 6 7 MMT Leverage  Figure 5.26 Anterior Displacement Effect for Control Group (Left & Right Legs) (p = 0.20)  82  Discussion The first purpose of this study was to determine the effect of proprioceptive acuity, ligament laxity and strength i n the performance of a functional skill (single leg hop for maximum distance).  The second purpose of the study was to demonstrate side-to-side  differences in proprioceptive acuity, ligament laxity, strength and functional hop tests, among conservatively and surgically managed subjects following A C L injury, and uninjured control subjects. Three groups of twenty subjects were compared. The conservative group included 9 females and 11 males with an average age of 26.5 years, who suffered a complete rupture of their anterior cruciate ligament of one leg (12 left, 8 right) an average of 39.7 months previously. None had been surgically treated for the injury. The surgical group included 13 females and 7 males with an average age of 29.9 years, who had undergone surgical treatment for an isolated unilateral anterior cruciate ligament rupture (11 left, 9 right). A l l members of the surgical group were operated within two weeks of injury by a single surgeon. The operative technique used was an augmented repair of the A C L using the semitendinosus tendon.  This technique attempts to maintain the viability of the neural  structures within the A C L , and provides an early blood supply to the tendon graft by means of the remaining A C L tissue. The control group consisted of 10 females and 10 males with an average age of 25.1 years, who had intact anterior cruciate ligaments bilaterally. There were no significant differences among the groups i n any of the descriptive parameters. Interval results were statistically tested by means of analysis of variance and multiple regressional analysis. Post hoc analysis between group pairs were performed using Tukey's H S D test. Ordinal data was statistically tested using the C h i square test. The level of significance for all statistical tests was set at p < 0.05.  83  Subjective Results T w o scales were used to assess subjects' sport activity level.  The Noyes Sports  Activity Rating Scale (Noyes et al., 1989) takes into account the sport of involvement and the frequency in which it is played.  It ranks subjects into twelve categories, which are  further divided into four levels according to frequency o f participation. There were no significant differences in the pre-injury ratings among the three groups.  There was  however a significant difference between the two injured groups in the post injury ratings with the conservative group scoring lower than the surgical group. The Tegner & Lysholm Activity Score (Tegner & L y s h o l m , 1985) takes into account a subject's sport of participation and their level of participation (elite, competitive or recreational). Scores are ranked from zero to ten. F o r the purpose of this study scores were divided into three groups as follows: scores of seven or higher (competitive sports and recreational sports involving high speed cutting and turning), scores between 5 and 6 (sports involving minimal cutting and turning), and scores of 4 and below (sports involving linear motion only). The Tegner & Lysholm Activity Score ranked the control group significantly below either of the two injured groups pre-injury.  There was no  significant pre-injury score difference between the two injured groups.  However, the  conservative group scored significantly lower than the surgical group i n the post injury score. The difference in results between these two scores lies primarily in the fact that there were fewer competitive athletes in the control group than i n the injured groups.  Both  scores showed no difference between injured groups before injury, and a significantly lower scores for the conservative group than the surgical group post injury. These findings are in agreement with the predicted outcomes for similar groups in the literature (Jackson, 1988; Johnson, 1983; M c D a n i e l & Dameron, 1980; Odensten et al., 1985).  84  Subjects i n the injured groups were asked to compare their pre-injury sport level to their post injury sport level. The results of this question showed that only three of the conservative group subjects reported no change in their sport level, compared to ten subjects i n the surgical group. Seventeen of the conservative subjects reported playing at a decreased sport level. Eight of the surgical subjects reported playing at a decreased sport level, three of which stated their reason for decreased sport level was not related to their knee.  O f those playing at a decreased level, 13 conservative group subjects reported  having moderate to significant problems with their knee. Only two surgical subjects reported having moderate to significant problems with their knee, one of whom had suffered a re-injury several months before testing, and was unable to play. Re-injury was confirmed on KTIOOO measurements where an 11mm side-to-side difference was recorded on maximum manual testing. These results indicate an improved functional outcome for the surgical group with respect to the conservative group. This is supported by the results o f the Lysholm Knee Scoring Scale OLysholm & Gillquist, 1982), which is a subjective measurement of functional outcome. There was no difference between the surgical group and the control group i n Knee Scoring Scale results.  However, the conservative group  scored  significantly lower than the other groups, suggesting a poorer functional outcome for this method of treatment. Objective Results  Proprioceptive Inaccuracy There was no significant difference i n proprioceptive inaccuracy between the surgical group and the control group (-0.2 and 0.02 degrees respectively), but a significant difference between the conservative group (3.6 degrees) and the other two groups.  In  1991, Barrett found 2.9 degree side-to-side difference in normals, a 6.8 degree difference in an A C L reconstructed group, and a 9.1 degree difference in an A C L deficient group.  85  The A C L deficient group in his study showed a significantly greater proprioceptive deficit than either the surgical or control group. Barrett suggested that the poorer performance of the A C L deficient subjects may have been due to abnormal mechanics of the A C L deficient knee, which produce non-physiological inputs through the neurological structures o f the remaining knee ligaments and capsule. While Barrett found a deficit in his surgical group,  in the present study, the  surgically treated group were not significantly different than the control group. difference i n results may be partially explained by the surgical procedure used.  This  Subjects in  this study underwent a different operative procedure which not only acted to normalize mechanical function of the knee, but attempted to maintain neurological structures within the original A C L , which was not the case in the Barrett study. Barrack et al. (1989) was able to show a difference in proprioceptive function between an A C L deficient group and a normal control group. reproduction of joint angles between 30 and 40°.  They measured the  Their results showed that the  proprioceptive deficit was attributable to the loss of the A C L , and not other factors such as subject age, time since injury or muscle strength. Corrigan et al. (1992) showed a significant difference in ability to detect joint movement between normals and A C L deficient subjects. The proprioceptive deficit of the A C L deficient knee demonstrated in this and other studies, and the fact that surgery can help to normalize proprioceptive function strengthens the argument for surgical treatment of these patients. Surgery has been shown to improve mechanical laxity of the knee, and it is now being suggested that it may improve proprioceptive function of the knee as well. The improvement in proprioception following surgery may be a result of improved mechanical function of the knee, which ensures that more physiological inputs being sent from remaining proprioceptors in the joint capsule and other ligaments. Normal proprioceptive function is thought to have an important effect in  86  preventing long term degenerative changes.  This is one of the rationales for surgical  intervention following A C L disruption. Anterior Tibial Displacement K T 1 0 0 0 measurements were taken at 134N (30 lbs.) and maximum manual test (MMT).  A side-to-side difference of 2.1mm was found in the surgical group for both  measurements.  If the data from the single subject who reported reinjuring his leg is  excluded from the group, the results for the two tests become 1.63 and 1.68mm. These are very good post operative results. Harter et al. (1988) examined 51 post operative A C L reconstructed subjects an average of 48 months post operation. They found a 1.83mm difference at 9 0 N (20 lbs.) force with a K T 1 0 0 0 . Gomez et al. (1990) measured a group of subjects 37.9 months post surgery and found a K T 1 0 0 0 maximum manual test difference of 2.30mm. Subjects i n the Gomez series were operated using a similar surgical technique to that used in this study. Aglietti et al. (1994) used a K T 2 0 0 0 to compare anterior tibial displacement differences between  subjects reconstructed with a patellar tendon graft and subjects  reconstructed with a semitendinosus/gracilis graft. The K T 2 0 0 0 is similar to the K T 1 0 0 0 , but includes a chart recorder which gives a force-length printout as well as absolute laxity measurements. Aglietti et al. defined a side-to-side difference of greater than 5 mm as the limit of graft failure. Their results showed that 13% o f the patellar tendon grafts failed at 134N, and 20% failed at M M T . In the semitendinosus/gracilis group 20% failed at 1 3 4 N , and 23% failed at M M T . There was no significant difference between the two groups. In the present study, i f the same criterion for failure is used, only 10% of the subjects failed at 134N, and 5% failed at M M T . It is expected that K T 1 0 0 0 scores at M M T would be greater than those at 134N. It was therefore unexpected that one subject would score over 5 mm at 134N, but under 5 mm at M M T .  When the data from this subject is considered, it is seen that the M M T  87  measurements were greater than the 134N measurements for both legs, but the side-to-side differences were not as expected (see Table 5.13). A small amount of muscle guarding on the injured side during M M T testing, or of the uninjured side during 134N testing may have accounted for the difference.  Table 5.13 K T 1 0 0 0 Results for a Single Re-injured Subject (mm) KT1000 ( M M T ) K T 1 0 0 0 (134N) Uninjured Injured Difference Uninjured Injured Difference Leg Leg Leg Leg 3.0  8.5  5.5  5.5  10.0  4.5  Strength There was a significant difference between the surgical and control groups in concentric quadriceps and concentric hamstring symmetry indexes. The conservative group's eccentric hamstring symmetry index was significantly lower than that of the control group. However, these differences do not indicate significant strength deficits i n the injured groups. The symmetry index for the control group was arbitrarily calculated by dividing the right leg strength by that of the left leg and multiplying the quotient by 100. In all of the three significant results above the side-to-side difference in the control group was greater than that of the injured groups.  H a d the symmetry index i n the control group been  calculated as left leg/right leg x 100, no significant differences would have been found. There were no significant differences among groups for uninjured leg torque values or for injured leg torque values i n any of the strength parameters tested. In this study, all strength symmetry indexes were at or above 90 (at or below 110 for the control group). This indicates that subjects from the two injured groups were able to strengthen within a 10% difference between legs, a difference within the normal range.  88  It appears that A C L deficiency or reconstruction does not affect a subject's ability to strengthen his or her quadriceps or hamstring muscles. Concentric and eccentric quadriceps strength deficits in both injured groups were larger than the corresponding hamstring deficits. These results were not significant, but agreed with those found by Tibone et al. (1986) who noted that A C L deficient subjects had a greater quadriceps deficit (SI = 86) than hamstring deficit (SI = 96)  C o et al. (1993)  examined a group of A C L reconstructed subjects and found a greater quadriceps deficit (SI = 85) than hamstring deficit (SI = 96). Aglietu' et al. (1994), who compared patellar tendon reconstructed grafts to semitendinosus/gracilis grafts, found concentric quadriceps and hamstrings symmetry indexes between 94 and 99 when subjects were tested at 1807s. They concluded that use o f a semitendinosus/gracilis graft did not result in weakening o f the hamstring muscles. Their results are in agreement with those of this study. Both the surgical group and the conservative group scored lower with the injured leg than with the uninjured leg i n all tests (not significant). The surgical group had higher symmetry indexes for eccentric quadriceps and hamstring tests than concentric tests, while the conservative group had higher symmetry indexes for concentric tests than eccentric tests. This trend was not significant. Functional Performance The conservative group performed significantly poorer in both functional tests than the other two groups.  Their symmetry indexes were 92 for the single leg hop for  maximum distance ( S L H D ) , and 94 for the timed 6 metre single leg hop ( S L H T ) .  The  surgical and control groups did not differ in either test. Their symmetry indexes were 98 and 100 for the S L H D and 99 and 101 for the S L H T respectively. Tegner et al. (1986) measured single leg hop for distance in normals and A C L deficient subjects.  H e found the injured group performed significandy poorer (SI = 90)  than the normal group (SI = 96). Kramer et al. (1993) looked at S L H D performance in  89  A C L reconstructed subjects. These subjects demonstrated a S L H D symmetry index of 96. These results are similar to those found in the present study. Although all groups scored within 10% side-to-side differences, statistically sigriificant differences between groups were found. In this study, the mean of three trials was used to calculate S L H D and S L H T .  The  literature appears evenly split between using the mean of three trials (Kramer et al., 1992; Noyes et al., 1991; Daniel et al., 1990) or the best of three trials (Fonseca et al., 1992; Gauffin et al., 1990; Tegner et al., 1986). Kramer et al. (1992) examined the difference between these two testing procedures and determined that results were not affected whether the single best score or the average of three attempts was used. Regressional Analyses Three regressional analyses were performed testing the effects of proprioceptive acuity, anterior displacement (KT1000 (MMT)) and strength (concentric quadriceps peak torque) on functional performance (single leg hop for maximum distance) for each of the three study groups. A l l three analyses showed a significant whole model effect (p < 0.05). The multiple correlation coefficients were 0.54 for the conservative group (injured leg), 0.40 for the surgical group (injured leg), and 0.30 for the control group (both legs combined). This indicates that between 30% and 54% of the functional test result could be explained by the model. The only individual effect which was significant was concentric quadriceps peak torque. It was significant for all three groups. Neither proprioceptive acuity nor anterior tibial displacement had significant effects on any of the three models. In contrast to these results, Gauffin et al. (1990) found that strength measurements of the quadriceps and hamstring muscles were not correlated to the single leg hop symmetry index in A C L deficient subjects.  Harter et al. in 1988 were unable to show significant effects o f  hamstring peak torque, anterior displacement (KT1000) or knee joint position sense on a  90  subjective measurement of knee function (Knee Function Rating Form (Harter et al. 1988)) in a group of A C L reconstructed subjects. Fonseca et al. (1992) were able to demonstrate that KTIOOO results correlated with S L H D symmetry index and to the Lysholm Knee Scoring Scale. The fact that quadriceps strength had so strong an effect in predicting functional performance for all groups shows how important this muscle group is during activity. It accounted for as much as 54% of the single leg hop performance. Although the importance of hamstring strength following injury to the A C L cannot be denied, all muscle groups must be addressed during rehabilitation. Athletes and non-athletes must have sufficient strength of all muscle groups to allow proper execution of their chosen activities. This study showed no significant effect o f proprioceptive acuity on functional performance. However, in 1991, Barrett was able to correlate proprioceptive acuity (as measured in this study) with a subjective evaluation of function and with patient satisfaction. Perhaps a more dynamic measurement of proprioception would be better able to predict functional outcomes. Originally it was intended that the regressional analyses would be performed using symmetry indexes for strength and functional testing, and injured leg - uninjured leg differences for anterior displacement and proprioceptive acuity. This was changed in favor of using only injured leg data for each of the factors. B y comparing actual test scores, the regressional analyses were able to demonstrate how performance of the independent variables affected performance of the dependent variable. If side-to-side differences and ratios were used, the results would be much more difficult to interpret, and would not represent the actual subject performances. For example, two subjects who have equal sideto-side differences in quadriceps strength may have very different peak torques.  If their  symmetry indexes are used in the regressional analysis, the effect of this difference i n strength is not included in the results. If the dependent variable is also a ratio of injured leg  91  and uninjured leg data then the results become ever more difficult to interpret. Harter et a l . (1988) also restricted regressional analysis to injured leg data only.  92  Limitations Several limitations should be considered with this study. They were controlled for as much as possible as indicated. Threats to Internal Validity: 1. Group selection - The A C L Deficient group may have represented subjects who were willing to lower their activity level following injury instead of opting for surgical treatment. They may therefore have a lower physical activity level than the other groups. This was monitored by asking subjects what their physical activities were. 2.  Proprioceptive acuity - as measured by Barrett et al., 1991 shows a trend toward decreased error values as the number of trials increases.  Therefore the order of  testing (right/left, injured/uninjured) was randomized. 3.  Functional testing - Although the functional tests used have been demonstrated to show the greatest differences between A C L intact, A C L deficient and A C L reconstructed subjects, it was still expected that approximately 50% of the A C L deficient and A C L reconstructed subjects w i l l score within the normal ranges. made finding significant differences difficult.  This  It should be noted however, that  these tests more closely approximate real-to-life situations and provide important information for that reason. Threats to External Validity: 1. A C L injuries are often associated with other bony and soft tissue injuries (such as medial meniscal tears and medial collateral ligament injuries). Subjects entering this study were limited to those suffering from isolated A C L injuries.  This limited  possible confounding factors, but w i l l also restrict to what extent the conclusions can be generalized.  93  2.  Measurement Context - Testing was performed in a laboratory setting instead of a sports setting.  This setting w i l l have more closely approximated some sport  settings than others. 3. Measurement Context - Subjects who normally wear a brace during activities were not allowed to wear the brace during testing.  This may have affected their  confidence in performing a maximal effort during the strength measurements and functional testing. It is expected that roughly the same number of subjects from each of the two treatment groups wear a brace during sport activities.  94  Chapter Six S U M M A R Y AND CONCLUSIONS  Summary Injury of the anterior cruciate ligament ( A C L ) is very common in sports. reported to be the most frequently completely torn ligament in the knee.  It is  A C L injury is  often associated with other tissue damage such as medial collateral ligament tears medial meniscal tears and articular cartilage damage.  Loss of the A C L frequendy results in an  inability to perform high level sport activities such as alpine skiing or sharp cutting and turning maneuvers due to "giving way" or functional instability of the knee. The expected course of an untreated A C L deficient knee is one of progressive deterioration of function, increased incidence of subsequent injury, and accelerated degenerative changes of the knee. Anatomical and biomechanical properties of the A C L have been extensively studied in the past. Recent investigations have considered the neurological structure and function this ligament. Four types of mechanoreceptors have been demonstrated i n the human A C L , and electromyographic changes and somatosensory evoked potentials have been shown with direct stimulation of the A C L . Proprioceptive deficits have been seen in A C L deficient knees when compared to normal knees, and a recent study by Barrett et al. (1991) found that proprioception was closely correlated with patient satisfaction and subjective analysis of function. Neither standard knee scores nor clinical ligament testing correlated as well with either satisfaction or function. The purpose  of this study  was  to determine  the  relative importance  of  proprioceptive acuity, anterior tibial displacement and strength, i n the performance of a functional skill. A second purpose of the study was to demonstrate differences among the three groups in knee proprioception, anterior tibial displacement, quadriceps and hamstring muscle strength, and two functional performance tests.  95  Three experimental groups of twenty subjects were compared. A group of twenty A C L deficient subjects who were conservatively treated and were more than 8 months post injury (conservative group), and a group of twenty subjects who had been surgically treated for an isolated A C L rupture and were more than 1 year post surgery (surgical group) were compared to a third group of twenty control subjects with normal knees. Scores from the subjective questionnaire indicated that there was no difference in level of sport involvement between the two injured groups before injury.  Post injury  results showed that the conservative group were participating at a significantly lower level of sport involvement than the surgical group.  The conservative group also rated their  functional outcome lower than the surgical group did. The conservative group scored significantly worse than either of the other groups in proprioceptive inaccuracy, both anterior tibial displacement tests (134N and M M T ) and both functional hop tests ( S L H D and S L H T ) .  The surgical group was not significantly  different from the normal control group in either proprioceptive function or functional hop testing.  The surgical group had an excellent post surgical outcome in anterior  tibial  displacement tests (2.1mm), while the conservative group had a poor result (5.5mm) with the maximum manual test. There were no significant differences among groups i n any of the strength measurements. Regressional analyses revealed that concentric quadriceps peak torque had a significant effect on single leg hop for maximum distance performance for all three groups. Proprioceptive acuity and anterior tibial displacement had no significant effect on S L H D in any of the three groups.  96  Conclusions The following conclusions can be made based on the hypotheses set forth prior to commencement of this study: 1.  Conservatively treated subjects had a greater injured side to uninjured side deficit in proprioceptive acuity than either surgically treated subjects or uninjured control subjects.  2.  Surgical subjects  had no side-to-side deficit in proprioceptive acuity when  compared to a group of uninjured control subjects. 3.  Conservative and surgical subjects had significandy greater side-to-side differences in anterior tibial translation than uninjured controls. However, while conservatively treated subjects showed a poor average outcome (5.5mm at M M T ) , surgical subjects demonstrated an excellent average outcome (2.1mm).  Surgery therefore  resulted in significantly lower differences in anterior tibial translation than conservative treatment. 4.  There were no significant differences in strength symmetry indexes among groups for concentric or eccentric quadriceps or hamstring muscle tests.  There was no  difference i n relative hamstring:quadriceps strength ratios among the groups tested. 5.  The conservative group had a significant injured leg deficit (compared to the uninjured leg) i n both distance hopping and timed hopping when compared to both the surgical group and the control group.  6.  There was no side-to-side deficit in hopping function in the surgical group  7.  Concentric quadriceps peak torque was the only dependent variable tested which had a significant effect on performance of a single leg hop for maximum distance. This result was the same for all groups tested.  8.  Proprioceptive acuity and anterior tibial displacement had no significant effect on performance of a single leg hop for maximal distance in any of the groups tested.  97  Recommendations Based  on  the  information  gathered  during  this  study,  the  following  recommendations are proposed: 1.  Proprioception is a very broad term which includes kinesthesia (joint movement sense), statesthesia (joint position sense) and vestibular function. This study only considered one aspect of proprioception, joint position sense, and may therefore have tested the inputs from Ruffini endings i n the knee joint, but not the inputs from Pacinian corpuscles or golgi tendon organ-like endings.  It is therefore  recommended that a dynamic measurement of proprioceptive acuity be developed so that all joint proprioceptors w i l l be stressed as they are during functional activity. 2.  This study  showed that post  surgical subjects  had no relative deficit i n  proprioceptive acuity compared to normal subjects.  It is recommended that the  surgical technique used in this study be compared to a surgical technique which does not attempt to salvage neurological structures, with respect to their effect on proprioceptive acuity. 3.  The conservative group showed a significant side-to-side difference in functional performance in both hop tests with respect to the other two groups.  Although  quadriceps peak torque was the only variable tested to show a significant effect on functional performance, the conservative group showed no deficit i n peak torque. This suggests that another variable, such as dynamic prorioception, may have a significant effect on functional performance in this group.  Future investigations  could therefore consider the effect of a dynamic proprioceptive training programme on functional performance in A C L deficient subjects. 4.  The control group demonstrated a right leg dominance i n all strength measurements. Differences between legs were as large as ten percent. investigate lower extremity strength dominance.  Further research could  Specific questions may include  98  whether upper extremity dominance can be used to determine lower extremity dominance, and how different sport activities affect lower extremity dominance. 5.  Although a significant difference in functional performance was found between the conservative group and the other groups, all groups demonstrated symmetry indexes greater than 90 for each test. Researchers have attempted to develop a test which is able to show a greater difference between groups, but have not succeeded to date. Finding a functional performance test which is able to both demonstrate the effects of A C L insufficiency, and correlate closely with the ability to perform high level sport activities should be a priority for future investigations.  6.  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R e c . 214. 204-209  108  Appendix A  SUBJECTIVE RATING SCALES  109  Table A l Noyes Sports Activity Rating Scale Points Level I 4 - 7 days  100 95 90  Level II 1 - 3 days/week  85 80 75  Level III 1-3 times/month  65 60 55  Level I V N o sports possible  Sports Jumping, hard pivoting, cutting (basketball, volleyball, football, soccer, gymnastics) Running, twisting, turning (racquet sports, baseball, hockey, skiing, wrestling) N o running, twisting, jumping (running, cycling, swimming) Jumping, hard pivoting, cutting (basketball, volleyball, football, soccer, gymnastics) Running, twisting, turning (racquet sports, baseball, hockey, skiing, wrestling) N o running, twisting, jumping (running, cycling, swimming) Jumping, hard pivoting, cutting (basketball, volleyball, football, soccer, gymnastics) Running, twisting, turning (racquet sports, baseball, hockey, skiing, wrestling) N o running, twisting, jumping (running, cycling, swimming)  40  A D L with no problems  20 0  A D L with moderate problems A D L with severe problems  110  Table A 2 Tegner & Lysholm Activity Score Activity Score 10 Competitive sports Soccer—national and international elite 9 Competitive sports Soccer, lower divisions Ice hockey Wrestiing Gymnastics 8 Competitive sports Bandy Squash or badminton Athletics (jumping etc.) Downhill skiing 7 Competitive sports Tennis Athletics (running) Motorcross, speedway Handball Basketball Recreational sports Soccer Bandy and ice hockey Squash Athletics (jumping) Cross-country track findings both recreational and competitive 6 Recreational sports Tennis and badminton Handball Basketball Downhill skiing Jogging, at least five times per week  5  Work Heavy labor (e.g., building, forestry) Competitive sports Cycling Cross-country skiing Recreational sports Jogging on uneven ground at least twice weekly 4 Work Moderately heavy labour (e.g., truck driving, heavy domestic work) Recreational sports Cycling Cross-country skiing Jogging on even ground at least twice weekly 3 Work Light labour (e.g., nursing) Competitive and recreational sports Swimming Walking i n forest possible 2 Work Light labour Walking on uneven ground possible but impossible to walk i n forest 1 Work Sedentary work Walking on even ground possible 0 Sick leave or disability pension because of knee problems  Table A 3 Change in Sport Level Unable to Play  Decreased  Not Changed •  no/slight problems  •  no/slight problems  •  •  moderate/significant problems  •  moderate/significant problems  moderate/significant problems  •  not related to knee  •  not related to knee  Ill Table A 4 Lysholm Knee Scoring Scale L i m p (5 points) None Slight or periodical Severe and constant Support (5 points) None Stick or crutch Weight-bearing impossible Locking (15 points) N o locking and no catching sensations Catching sensation but no locking Locking Occasionally Frequently Locked join on examination Instability (25 points) Never giving way Rarely during athletics or other severe exertion Frequently during athletics or other severe exertion (or incapable of participation) Occasionally in daily activities Often in daily activities Every step Pain (25 points) None Inconstant and slight during severe exertion Marked during severe exertion Marked on or after walking more than 2 k m Marked on or after walking less than 2 k m Constant Swelling (10 points) None On severe exertion O n ordinary exertion Constant Stair-climbing (10 points) N o problems Slightly impaired One step at a time Impossible Squatting (5 points) N o problems Slightly impaired Not beyond 90° Impossible  5 3 0 5 2 0 15 10 6 2 0 25 20 15 10 5 0 25 20 15 10 5 0 10 6 2 0 10 6 2 0 5 4 2 0  

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