Department of Movement Sciences, Human Movement Biomechanics Research Group, KU Leuven, Leuven, Belgium.
Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
PLoS One. 2018 Oct 16;13(10):e0205842. doi: 10.1371/journal.pone.0205842. eCollection 2018.
The current study quantified the influence of cartilage defect location on the tibiofemoral load distribution during gait. Furthermore, changes in local mechanical stiffness representative for matrix damage or bone ingrowth were investigated. This may provide insights in the mechanical factors contributing to cartilage degeneration in the presence of an articular cartilage defect.
The load distribution following cartilage defects was calculated using a musculoskeletal model that included tibiofemoral and patellofemoral joints with 6 degrees-of-freedom. Circular cartilage defects of 100 mm2 were created at different locations in the tibiofemoral contact geometry. By assigning different mechanical properties to these defect locations, softening and hardening of the tissue were evaluated.
Results indicate that cartilage defects located at the load-bearing area only affect the load distribution of the involved compartment. Cartilage defects in the central part of the tibia plateau and anterior-central part of the medial femoral condyle present the largest influence on load distribution. Softening at the defect location results in overloading, i.e., increased contact pressure and compressive strains, of the surrounding tissue. In contrast, inside the defect, the contact pressure decreases and the compressive strain increases. Hardening at the defect location presents the opposite results in load distribution compared to softening. Sensitivity analysis reveals that the surrounding contact pressure, contact force and compressive strain alter significantly when the elastic modulus is below 7 MPa or above 18 MPa.
Alterations in local mechanical behavior within the high load bearing area resulted in aberrant loading conditions, thereby potentially affecting the homeostatic balance not only at the defect but also at the tissue surrounding and opposing the defect. Especially, cartilage softening predisposes the tissue to loads that may contribute to accelerated risk of cartilage degeneration and the initiation or progression towards osteoarthritis of the whole compartment.
本研究定量分析了关节软骨损伤位置对步态中胫股关节负荷分布的影响。此外，还研究了代表基质损伤或骨长入的局部力学刚度变化。这可能为关节软骨损伤时软骨退变的力学因素提供新的认识。
使用包含胫股关节和髌股关节的多刚体模型来计算软骨损伤后的负荷分布，该模型具有 6 个自由度。在胫股接触几何形状的不同位置创建 100mm2 的圆形软骨损伤。通过为这些损伤位置分配不同的力学性能，评估组织的软化和硬化。
结果表明，仅位于负重区的软骨损伤仅影响受累关节的负荷分布。胫骨平台中央和内侧股骨髁前中央的软骨损伤对负荷分布的影响最大。损伤部位的软化会导致周围组织的过载，即接触压力和压缩应变增加。相比之下，在损伤内部，接触压力降低，压缩应变增加。损伤部位的硬化会导致负荷分布与软化相反的结果。敏感性分析表明，当弹性模量低于 7MPa 或高于 18MPa 时，周围接触压力、接触力和压缩应变会发生显著变化。
高负重区局部力学行为的改变导致了异常的加载条件，从而可能不仅在损伤部位，而且在损伤周围和对侧的组织中影响到平衡状态。特别是软骨软化会使组织容易受到可能导致软骨退变加速的负荷的影响，从而引发或进展为整个关节的骨关节炎。
