A Parametric Design Evaluation of Lateral Prophylactic Knee Braces

Abstract

Six major mechanical design variables characterizing single-upright lateral prophylactic knee braces were studied experimentally, using a generic modular brace (GMB). Impulsive valgus loading tests were conducted with the GMB applied to a surrogate leg model. The surrogate involved anatomically realistic aluminum-reinforced acrylic components to model bone, and expendable polymeric blanks to mimic the major knee ligaments. Behavior of the surrogate system reasonably reproduced that of human cadaveric knees under similar loading conditions. Load at failure of the medial collateral ligament (MCL) analog, gross knee stiffness, and MCL relative strain relief were measured for each of twelve parametric brace design permutations. Compared to the unbraced condition, bracing provided statistically significant increases in valgus load uptake at failure and in MCL strain relief. Increasing the dimensions of individual brace components (hinge length and offset; upright length, breadth, and thickness; cuff area), relative to those of a GMB baseline configuration deemed representative of current commerical products, failed to achieve statistically significant improvements in brace performance. However, most below-baseline dimensioning of individual components did significantly compromise GMB performance. These surrogate test data indicate that geometric modifications of current single-upright lateral brace designs are unlikely to substantially improve upon the fairly modest valgus load protection afforded by this class of devices.