锁定钢板用于胫骨远端骨折外固定的有限元分析

Finite element analysis of external fixation using locking plate in distal tibial fractures

目的探讨锁定钢板用于胫骨远端骨折外固定的生物力学特性。方法利用三维有限元技术,创建胫骨远端骨折锁定钢板外固定模型。将股骨LISS钢板放置于胫骨前内侧,钢板与骨面距离设定为1、10、20、30 mm 4个组,在骨折远近端各锁定4枚双皮质螺钉。对骨折固定模型分别施加垂直负荷及旋转外力,观察在不同外力作用下,骨折固定模型的稳定性变化。结果骨折固定模型的稳定性随着钢板与骨面距离的增加而下降。在单一垂直载荷下,30 mm组的刚度接近正常胫骨,1、10、20 mm组的刚度高于正常胫骨。在垂直及内旋载荷下,1 mm和10 mm组的刚度接近正常胫骨,20 mm和30 mm组的刚度低于正常胫骨。在垂直及外旋载荷下,4组的刚度均低于正常胫骨。钢板峰值应力集中在最靠远端的2枚螺钉,在10 mm组最高,在1 mm组最低。结论采用锁定钢板外固定胫骨远端骨折时,为了获得良好的稳定性,钢板与骨面的距离宜保持在30 mm以内。在完全负重站立位时,要避免旋转动作,以降低固定失败的风险。

Objective To investigate the biomechanical features of external fixation for distal tibial fractures using locking plate. Methods Using the finite element technique, the computational processing model of external fixation of distal tibial fracture using femoral less invasive stabilization system （LISS） plate was analyzed. The plate was placed on the anteromedial aspect of tibia with different plate-bone distance： 1 mm, 10mm, 20mm, and 30mm. There were four bicortical screws in each side of fracture. The stability of construct was evaluated under vertical and rotational force. Results Stiffness of construct decreased with increased plate-bone distance. Under vertical load, the stiffness of construct with 30 mm plate-bone distance was similar to that in intact tibia. The stiffness of construct with 1 mm, 10 mm, and 20 mm plate-bone distance were higher than that in intact tibia. Under vertical load with internally rotational force, the stiffness of construct with 1 mm, 10 mm plate- bone distance was similar to that in intact tibia. The stiffness of construct with 20 mm, 30 mm distance was lower than that in intact tibia. Under vertical load with externally rotational force, the stiffness of construct in all groups was lower than that in intact tibia. The maximum plate stresses were concentrated at the two most distal screws and were highest in construct with 10 mm plate-bone distance, least in construct with 1 mm plate-bone distance. Conclusion With a plate-bone distance less than 30 mm, external fixation using femoral LISS plate can provide instant stability to stand full weight bearing in tibial distal metaphyseal fractures. When standing, rotation of tibia should be warned of increased risk of fixation failure.