The effects of prophylactic brace construction materials on the reactive responses of the MCL during repetitive impacts

Objective: The purpose of the present study was to investigate the effect of different construction materials on the ability of a prophylactic brace to reduce the stresses sustained by a surrogate medial collateral ligament (MCL) under low-energy repetitive impact conditions. Design and Setting: A surrogate leg was fixed at both the hip and foot with the knee in full extension. A prophylactic brace was attached to the surrogate leg and the system struck by an impactor weighing either 6.68 kg or 16.9 kg. Subjects: A single brace design (Am Pro Knee Guard) was used. Three different materials (nylon, aluminum, graphite) were used in constructing the brace uprights. Measurements: Tension in the MCL was measured under all conditions of brace material and impactor weight. In addition, the impact impulse response of the system was evaluated. Results: The graphite and aluminum uprights showed significant reductions in both MCL peak tension magnitude (from 12 to 21% improvement) and in the impulse response of the MCL (from 36 to 47% improvement) when compared to the no-brace condition. Conclusions: The present study indicates that the choice of brace upright material does have a significant effect on the transmission and absorption of low-level repetitive impact forces at the MCL and should be an important consideration in the design of better knee braces.