新型组合式锁定钢板治疗SandersⅡ型及Ⅲ型跟骨骨折的有限元分析

Finite Element Analysis on Sanders Ⅱ and Ⅲ Calcaneal Fractures Treated with the Novel Composite Locking Plate

目的研究已投入临床中使用的长型组合式锁定钢板与新型短型组合式锁定钢板治疗Sanders IIa、IIb、IIIab型跟骨骨折的骨折端应力分布规律及生物力学的稳定性。方法建立Sanders IIa、IIb、IIIab型跟骨骨折三维模型,同时模拟跟骨在中立位及背伸20°时的受力情况。参照人体标本实物形态,施加500 N垂直轴向载荷,研究骨折块在受力作用下的位移及相对位移,并分析骨组织和内固定的受力情况。结果长、短型组合式锁定钢板固定Sanders IIa、IIb型跟骨骨折中,钢板及跟骨应力集中位置基本相同,两种钢板固定同一种类型跟骨骨折的最大应力差均小于5 MPa,骨折模型最大位移无明显差异。长、短型组合式锁定钢板固定Sanders IIIab型跟骨骨折中,前臂钢板螺钉最高应力集中,有金属疲劳风险,最大应力差达12 MPa,跟骨最大位移达9μm。结论长、短型组合式锁定钢板治疗Sanders IIa、IIb型跟骨骨折无明显差异,而Sanders IIIab型跟骨骨折治疗中,长型组合式锁定钢板的固定效果优于短型组合式锁定钢板。

Objective To study the stress distribution and biomechanical stability of the long-type composite locking plate already used in clinic practice and the novel short-type composite locking plate for treating Sanders type IIa,IIb and IIIab calcaneal fractures.Methods The three-dimensional( 3 D) models of Sanders type IIa,IIb and IIIab calcaneal fractures were established,and the force conditions of calcaneus in neutral standing position and under 20° dorsal extension were simulated.By referring to the physical form of human specimens,500 N vertical axial load was applied,so as to study the displacement and relative displacement of the fracture block under the force,and the force conditions of bone tissues and internal fixation were analyzed.Results For Sanders type IIa,IIb calcaneal fractures treated with long-type and short-type composite locking plates,the stress concentration positions of the plates and calcaneal fractures were basically the same.The maximum stress difference of the two plates for fixing calcaneal fractures with the same type was smaller than 5 MPa,and there was no significant difference in the maximum displacement of the fracture models.For Sanders type IIIab calcaneal fractures treated with long-type and short-type composite locking plates, the maximum stress concentration occurred in the forearm of plate screws,indicating the risk of metal fatigue.The maximum stress difference was up to 12 MPa,and the maximum calcaneal displacement was up to 9 μm.Conclusions The longtype and short-type composite locking plates showed no significant differences in treating Sanders type IIa,IIb calcaneal fractures.For fixing Sanders type IIIab calcaneal fractures,the long-type composite locking plate was superior to the short-type composite locking plate.