治疗股骨转子间骨折时头颈拉力螺钉不同置入位置的有限元计算

背景：课题组总结发现，股骨转子间骨折股骨近端髓内钉置入内固定治疗后出现髋内翻的病例中，除小部分由于股骨转子部粉碎性骨折和个别存在复位问题之外，绝大多数出现并发症的患者术后复查X射线片可见，2枚头颈拉力螺钉位置均位于股骨颈中上部。 目的：通过有限元计算，验证股骨近端髓内钉头颈拉力螺钉不同置入位置的生物力学性能，从而指导股骨近端髓内钉置入以减少置入后并发症的发生。 方法：利用MIMICS中的布尔运算将股骨近端髓内钉置入骨折模型，建立三维模型。实验分为2组：中下组股骨近端髓内钉头颈拉力螺钉置于股骨颈中下1/3处；中上组股骨近端髓内钉头颈拉力螺钉置于股骨颈中上1/3处。利用有限元软件计算头颈拉力螺钉于不同方向置入时股骨及股骨近端髓内钉的应力分布情况。 结果与结论：骨折断端应力分布结果显示，中下组小转子处所受压应力小于中上组，并且中下组股骨近端髓内钉各钉所受最大应力平均值大于中上组。骨折断面张开角测量结果显示，加载后中下组骨折断面张开角小于中上组。载荷与位移关系分析结果显示，加载后中下组股骨上部合位移小于中上组。说明2枚头颈拉力螺钉置入股骨颈中下1/3处时，生物力学性能更好，结构相对更稳定，受力更合理，在临床中具有重要的参考价值。

Finite element calculation of head and neck lag screws in different placement positions for intertrochanteric fracture

BACKGROUND：Our team summarized and found that in addition to a smal part due to the intertrochanteric comminuted and individual existence of the reset problem in the postoperative cases of coxa vara, radiograph of the vast majority of patients with complications after review revealed：two head and neck lag screws were positioned in the upper and middle femoral neck. OBJECTIVE：To verify the biomechanical properties of lag screws in different points of the neck of proximal femur using finite element calculation so as to guide the implantation of proximal femoral intramedul ary nail and to reduce the occurrence of complications. METHODS：Three dimensional models of fracture undergoing intramedul ary nail implantation in the proximal femur were established by using Boolean operation in MIMICS. This experiment contained two groups：in the lower and middle group, the lag screw was placed in the 1/3 lower and middle neck of femur;in the upper and middle group, the lag screw was placed in the 1/3 upper and middle neck of femur. The stress distribution of femur and proximal femoral intramedul ary nail was calculated using finite element software when lag screw was implanted at different directions. RESULTS AND CONCLUSION：Results of the stress distribution of the fracture broken ends showed that the stress of the smal trochanter was less in the lower and middle group than that in the upper and middle group. Moreover, mean value of maximal stress of intramedul ary nail in the proximal femur was larger in the lower and middle group than that in the upper and middle group. Results of the opening angle of the fracture surface demonstrated that the opening angle of the fracture surface after loading was smal er in the lower and middle group than that in the upper and middle group. Analysis results of the relationship between load and displacement displayed that the total displacement of the top of the femur after loading was smal er in the lower and middle group than that in the upper and middle group. These results confirmed that two head and neck lag screws in the 1/3 lower and middle femoral neck showed perfect biomechanical property, stable structure, and reasonable stress, which has important reference values in the clinic.