A comparison of stiffness of six knee braces with application for posterolateral corner reconstructions

Abstract

Posterolateral corner knee injuries are clinically significant, and often require surgical reconstruction. The optimal knee brace following posterolateral corner reconstructions has not yet been determined via clinical nor biomechanical study. We sought to evaluate the stiffness of six types of knee braces to determine the ideal brace type for reducing varus forces, which may have clinical utility for posterolateral corner knee reconstruction rehabilitation. Six different groups of knee braces underwent mechanical testing: cruciate braces, cruciate braces with a valgus bend, medial unloaders, articulating sleeves, hinged braces, and tri-panel immobilizers. Each brace was fitted to the same fiberglass leg model and was secured to the testing apparatus. Force was applied under four-point bending to generate a varus moment about the artificial knee. The stiffness in Newtons per millimeter (N/mm) of each brace was calculated from the slope of the force-displacement curve. The cruciate brace with a valgus bend had the highest average stiffness at 192.61 N/mm (SD 28.53). The articulating sleeve was the least stiff with an average stiffness of 49.86 N/mm (SD 8.99). Stiffness of the cruciate brace was not statistically different compared to cruciate valgus ( p = 0.083) or medial unloader ( p = 0.098). In this experimental design, a cruciate brace with a valgus bend was shown to have the highest overall stiffness, while an articulating sleeve had the lowest stiffness. Future work will investigate whether this translates into clinical performance.