踝关节骨折中外踝移位对胫距关节接触影响的三维有限元分析

Influence of various displacement modes of lateral malleolus associated with ankle fracture on tibiotalar joint contact： a finite element analysis

目的探讨踝关节骨折中不同类型的外踝移位对胫距关节接触的影响。方法采用1例正常志愿者踝关节CT断层扫描数据对踝关节进行三维重建，分别建立出包含关节软骨和周围韧带的踝关节数值模型，设定踝关节中立位状态下受到的轴向压缩生理载荷和边界条件，分别模拟踝关节骨折后腓骨外移、短缩、内旋和外旋状态，对比不同外踝移位模型组的胫距关节接触应力峰值和分布情况。结果4种不同的腓骨移位状态下产生的胫距关节面的接触应力峰值和分布特点有所差异，其中腓骨短缩、外移、内旋和外旋产生的胫距关节接触应力峰值变化差异分别为10．23％、45．22％、17．68％和17．68％；在胫距关节面接触应力分布特点上，腓骨的短缩可显著增加关节面前部的接触面积；腓骨外移则直接使踝穴增宽和距骨外移，从而使胫距关节负重面内移，关节接触面积显著减少；而腓骨内旋和外旋在不同的旋转角度范围均呈现出接触区域自内踝向前踝转移的现象。结论踝关节骨折后不同的腓骨移位类型均会影响胫距关节面的接触状态，其中外移、外旋和内旋移位的影响最为显著。该研究为踝关节骨折复位不良、畸形愈合继发关节疼痛和关节炎的诊断和修复重建提供一定的理论依据。

Objective To investigate the impacts of various displacement modes of lateral malleolus on the tibiotalar joint contact in ankle fractures. Methods The computed tomography scans of a normal adult volunteer were used for three-dimensional reconstruction of the whole ankle joint, including its cartilage and adjacent ligaments. Axial compressive loads during mid-stance and boundary conditions were set to sim- ulate the lateral displacement, shortening, internal rotation and external rotation of the fibula following ankle fracture. Magnitude and distribution of the peak contact stress on the tibiotalar joint were compared among various displacement modes of the lateral malleolus. Results The magnitude and distribution of the peak contact stress on the tibiotalar joint varied among the 4 fibular displacement modes. Compared to the reference model, the deviations of peak contact stress for the modes of shortening, lateral displacement, internal rotation and external rotation were 10. 23%, 45.22%, 17.68%, and 17.68%, respectively. Regarding the distri- bution of contact stress on the tibiotalar joint, the fibular shortening significantly increased the contact area on the anterior facet and the lateral displacement of the fibula widened the ankle joint and pulled the talus out- wards. This made the articular contact migrate medially, resulting in a decreased contact area. When either internal or external rotation occurred to a certain extent, the contact area was transferred from the medial malleolus to the anterior tibiotalar facet. Conclusions In ankle fractures, various displacement modes of the lateral malleolus may affect the tibiotalar contact condition, especially the lateral displacement, internal rotation and external rotation of the lateral malleolus. This study may provide a theoretical basis for diagnosis and reconstruction of malreduction, maluion, secondary joint pain and arthritis following an ankle fracture.