Shriram Duraisamy, Parween Rizuwana, Lee Yee Han Dave, Subburaj Karupppasamy
Annu Int Conf IEEE Eng Med Biol Soc. 2017 Jul;2017:1625-1628. doi: 10.1109/EMBC.2017.8037150.
Knee osteoarthritis that prevalently occurs at the medial compartment is a progressive chronic disorder affecting the articular cartilage of the knee joint, and lead to loss of joint functionality. Valgus braces have been used as a treatment procedure to unload the medial compartment for patients with medial osteoarthritis. Valgus braces through the application of counteracting external valgus moment shift the load from medial compartment towards the lateral compartment. Previous biomechanical studies focused only on the changes in varus moments before and after wearing the brace. The objective of this study was to investigate the influence of opposing external valgus moment applied by knee braces on the lateral tibial cartilage contact conditions using a 3D finite element model of the knee joint. Finite element simulations were performed on the knee joint model without and with the application of opposing valgus moment to mimic the unbraced and braced conditions. Lateral tibial cartilage contact pressures and contact area, and tibial rotation (varus-valgus and internal-external) were estimated for the complete walking gait cycle. The opposing valgus moment increased the maximum contact pressure and contact area on the lateral tibial cartilage compared to the normal gait moment. A peak contact pressure of 8.2 MPa and maximum cartilage loaded area of 28% (loaded cartilage nodes) on the lateral cartilage with the application of external valgus moment were induced at 50% of the gait cycle. The results show that the use of opposing valgus moment may significantly increase the maximum contact pressures and contact area on the lateral tibial cartilage and increases the risk of articular cartilage damage on the lateral compartment.
膝关节骨关节炎多发生在内侧间室，是一种影响膝关节软骨的进行性慢性疾病，会导致关节功能丧失。外翻支具已被用作内侧骨关节炎患者减轻内侧间室负荷的一种治疗手段。外翻支具通过施加反向的外部外翻力矩，将负荷从内侧间室转移至外侧间室。以往的生物力学研究仅关注佩戴支具前后内翻力矩的变化。本研究的目的是使用膝关节三维有限元模型，研究膝关节支具施加的反向外部外翻力矩对胫骨外侧软骨接触状况的影响。在膝关节模型上进行有限元模拟，分别模拟不施加和施加反向外翻力矩的情况，即模拟未佩戴支具和佩戴支具的状态。在整个步行步态周期中，估计胫骨外侧软骨的接触压力、接触面积以及胫骨旋转（内翻-外翻和内外旋）情况。与正常步态力矩相比，反向外翻力矩增加了胫骨外侧软骨上的最大接触压力和接触面积。在步态周期的50%时，施加外部外翻力矩会使外侧软骨产生8.2MPa的峰值接触压力和28%（加载软骨节点）的最大软骨加载面积。结果表明，使用反向外翻力矩可能会显著增加胫骨外侧软骨上的最大接触压力和接触面积，并增加外侧间室关节软骨损伤的风险。
