钛制弹性钉和锁定接骨板固定锁骨中段骨折的有限元分析

Finite Element Analysis of Manual Reduction Percutaneous Elastic Nail and Locking Plate in the Fixation of Middle Clavicle Fracture

目的比较钛制弹性钉(titanium elastic nail,TEN)及锁定接骨板(locking plate,LP)固定锁骨中段骨折的生物力学特点。方法通过Mimics和Geomagic Wrap软件构建锁骨三维模型,在Solidworks软件中模拟锁骨中段斜行骨折,分别构建8孔LP两端各3枚螺钉(P1)和直径2.5 mm TEN(N1)两种内固定模型。在ANSYS Workbench软件中比较不同内固定模型在100 N轴向载荷、100 N垂直载荷、100 N·mm顺时针扭转载荷及200 N轴向载荷、200 N垂直载荷、200 N·mm顺时针扭转载荷六种工况下远折端最大位移和内固定应力分布情况。结果垂直载荷下,N1远折端最大位移明显大于P1,但在轴向及顺时针扭转载荷下,二者位移基本相当。不同工况下,两种内固定模型远折端位移及内固定应力变化大致与所施载荷呈正相关。综合六种载荷工况,P1远折端最大位移接近正常锁骨(NC),但应力遮挡效应明显。N1在六种载荷条件下的应力分布接近NC,但其断端及针尾折弯处存在明显的应力集中现象。结论TEN固定锁骨中段骨折断端稳定性不及LP,但更符合生物力学原则。对于锁骨中段骨折,若术后早期进行患肢的悬吊制动,减少垂直方向上的应力负荷,钛制弹性钉髓内固定也可为骨折愈合提供相对稳定的力学环境。

Objective To compare the biomechanical characteristics of titanium elastic nail(TEN)and locking plate(LP)in the fixation of middle clavicle fracture.Methods The three-dimensional model of the clavicle was constructed by Mimics and Geomagic wrap software,and the oblique fracture of the middle clavicle was simulated in Solidworks software.Two kinds of internal fixation models,including three screws at both ends of 8-hole LP(P1),and TEN with diameters of 2.5 mm(N1)were constructed respectively.The maximum displacement and stress distribution of different internal fixation models under 100 N axial load,100 N vertical load,100 N·mm clockwise torsional load and 200 N axial load,200 N vertical load,200 N·mm clockwise torsional load were compared in ANSYS Workbench software.Results Under the vertical load,the maximum displacement of N1 distal end was significantly larger than that of P1,but under the axial and clockwise torsional loads,the displacement of both were basically equivalent.Under different working conditions,the maximum displacement and internal fixation stress of different internal fixation models were roughly positively correlated with the applied loads.Under the six load cases,the maximum displacement of P1 broken end was close to normal clavicle(NC),but the stress shielding effect was obvious.The stress distribution of N1 under six load conditions was close to NC,but there was obvious stress concentration at the broken end and the bending of the needle tail.Conclusion The stability of the broken end of the middle clavicle fracture fixed by TEN is less than that of LP,but it is more in line with the biomechanical principle.For the middle clavicle fracture,if the suspension braking of the affected limb is carried out in the early postoperative period to reduce the stress load in the vertical direction,the elastic titanium nail intramedullary fixation can also provide a relatively stable mechanical environment for fracture healing.