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UBC Theses and Dissertations

An analysis of the effect of the rotational, convex, poly-axial, mechanical knee brace (prototype I) : on the stability and dynamic range of motion of the knee joint Cooke, Christopher

Abstract

The functional loss of knee stabilitv that results from soft tissue and ligamentous injury is a serious problem for the conpetitive athlete. Non-surgical attempts to restore femoro-tibial stability and function have been centered on the external application of supportive tape and athletic knee braces. Several athletic braces are available on the market today. The more substantial ones, however, have proven ajrtibersane and uncomfortable in their attempts to provide support for the unstable knee. Prototype I of tlie rotational, convex, poly-axial, mechanical knee brace (Taylor Brace) was subjected to testing to deteririine its effect on knee stability and dynamic range of motion. Electrogoniometric recordings of knee function in three mutually perpendicular movement parameters were obtained from each subject at varying speeds of ambulation. Testing was conducted in the laboratory for unbraced and braced conditions using a 2 x 2 collapsible parallelogram chain electrogoniometer. Instant center of rotation pathways and joint surface velocity angles were determined from roentgenogram analysis of the unstable knee for unbraced and braced conditions. Seven medial roentgenograms were taken of the knee with the femur fixed and the tibia moved from ninety degrees of flexion to zero degrees of flexion in increments of fifteen to twenty degrees. Stress analysis was carried out on the unstable knee using a mechanical stress machine. Regulated forces were anplied to the knee joint and radiographic changes in the range of medial and anterior laxity recorded for the unbraced and braced knee. Subjective evaluation was also conducted in which subjects evaluated the Taylor Brace verbally, after each session of activity, and in an overall written assessement at the end of the study. Various aspects of brace construction and function were discussed under pre-determined criteria. Electrogoniometric results showed that the Taylor Brace had a general restraining effect on unwanted internal-external rotation and varus-valgus movement of the knee. Reductions in the flexion-extens range were also recorded but were considered unimportant as a hindrance to total knee function. There was also an indication that the contra-lateral, unbraced knee pattern changed following bracing. There were no consistent trends in the pattern or disoersion of the instant center of rotation pathways following bracing. A consistent shifting posteriorly and superiorly of the individual centers and a change in abnormal joint surface velocity angles, however, was noted following application of the Taylor Brace. Subjective evaluation suggested several minor aspects of brace construction for improvement in future prototypes. Triigh cuff rigidity, tibial abraison and brace slippage were cited as areas for improvement. Knee joint range and articulation was considered excellent as well as ease of application, overall brace comfort, lightness and cosmetics of design.

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