胫腓下联合分离的生物力学研究

A biomechanical study of syndesmosis diastasis

目的分析踝关节内、外侧结构和胫腓下联合损伤对踝关节稳定性的影响,探讨胫腓下联合固定的指征。方法12具新鲜膝关节以下下肢标本,随机分为a、b两组,分别模拟内踝骨折和三角韧带撕裂的旋前-外旋型踝关节骨折,按该型骨折加重顺序依次切断周围韧带,用压敏片和位移传感器分别测定每次处理后的关节接触面积和胫腓下联合分离距离。分析各操作步骤对关节接触面积、胫腓下联合分离距离的影响。结果a组切断三角韧带、b组切断骨间韧带后,关节接触面积及胫腓下联合分离距离较基线状态均有明显改变,差异有极显著性意义(P<0.01)。关节接触面积和下联合分离距离呈线性回归关系。结论踝关节的稳定性主要由踝关节内、外侧结构和中间的胫腓下联合共同维持,只有当三者中两处以上发生不可逆性损伤时,踝关节的稳定性才会发生根本性改变。因此,胫腓下联合分离时,下联合固定应选择性地使用。

Objective To evaluate factors which maintain the stability of the ankle, and discuss indications for trans-syndesmotic fixation. Methods 12 freshly-frozen cadaver legs amputated below the knee were collected and divided into 2 groups. An ankle fracture model of unconstrained pronation-external rotation was then designed. Group A simulated the injury combined with medial malleolus fracture, and Group B the injury combined with deltoid tear. Ligaments were cut off sequentially to simulate the increasing severity of the injury. Fuji super low-pressure sensitive films and displacement transducers were used to measure the contact area of the tibiotalar articular surface and the width of the syndesmosis. The data were analyzed with SPSS to analyze the relationship of ligament injury and ankle stability. Results In Group A, the articular contact area and the syndesmotic width after section of the deltoid were significantly different from those before the section （P〈0.01）. In Group B, after section of the interosseous ligament, the articular contact area and the syndesmotic width were notably altered （P〈0.01）. The regression equation of neutral position was y=414.808-73.158x, and that of plantar flexion was y=380.842-85.725x （y represents articular contact area, and x represents syndesmotic width）. Conclusions Since the stability of the ankle is maintained by 3 main factors： the medial, lateral structures of the ankle, and the syndesmosis, severe injury of only one structure will not affect the stability significantly. So, the trans-syndesmotic fixation is only necessary when more than 2 structures are destroyed irreversibly.