股骨近端防旋髓内钉-Ⅱ治疗31-A3型股骨转子间骨折扩髓与否的有限元分析

Finite element analysis of reamed versus undreamed proximal femoral nail antirotation-II in treatment of 31-A3 intertrochanteric femur fracture

背景:针对股骨转子间骨折是否需要扩髓的问题尚有争议,一些人认为不扩髓缩短手术时间、减少出血、降低高龄患者术中风险,但此举是否会降低髓内钉支撑效果,尚无依据。另一些人认为扩髓可选择直径更粗的髓内钉,获得更好的力学支撑,但基础研究显示此方法存在脂肪栓塞、破坏骨质(尤其高龄骨质疏松患者)等风险。目的:通过有限元分析股骨近端防旋髓内钉-Ⅱ治疗31-A3型股骨转子间骨折时扩髓与不扩髓的力学分布特点。方法:纳入一名健康志愿者,CT扫描其股骨获取DICOM格式文件,顺序导入Mimics、Geomagic Wrap、SolidWorks、Hypermesh、Ansys软件处理文件,得到A3.1型、A3.2型及A3.3型股骨转子间骨折模型,分别与9,11 mm直径、170 mm长度的股骨近端防旋髓内钉-Ⅱ进行装配,赋予材料属性,设定各接触面相互作用关系及定义载荷及边界条件,之后进行求解。观察不同模型中股骨应力分布、内固定应力分布、股骨位移及内固定位移情况。结果与结论:①各型骨折采用扩髓髓内钉固定时股骨应力均小于非扩髓髓内钉固定,A3.3型骨折股骨最大应力值大于A3.1型和A3.2型;②各型骨折采用扩髓髓内钉固定时内固定应力均大于非扩髓髓内钉固定,A3.3型骨折内固定最大应力值大于A3.1型;③扩髓与非扩髓对股骨及内固定位移影响较小,应力影响较大;④提示采用扩髓髓内钉固定可使股骨应力减小,内固定整体承担应力增大,远端锁钉承担应力减小;与非扩髓髓内钉固定相比,采用扩髓髓内钉固定可能会提供更好的治疗效果。

BACKGROUND:There is controversy regarding the need for marrow reaming in intertrochanteric fractures of the femur.Some believe that unreaming shortens operative time,reduces bleeding,and decreases intraoperative risk in elderly patients,but there is no basis for whether this move reduces the effectiveness of intramedullary nail support.Others believe that reaming allows for the selection of thicker diameter intramedullary nails for better mechanical support,but basic studies have shown that this approach carries risks such as fat embolism and destruction of bone(especially in elderly patients with osteoporosis).OBJECTIVE:To analyze the mechanical distribution characteristics of reamed and unreamed proximal femoral nail antirotation-II in the treatment of type 31-A3 intertrochanteric fractures by finite element analysis.METHODS:A healthy volunteer was included,and CT scans of his femur were obtained in DICOM format,and the files were sequentially imported into Mimics,Geomagic Wrap,SolidWorks,Hypermesh,and Ansys software for processing.The A3.1,A3.2,and A3.3 intertrochanteric fracture models were obtained and assembled with 9 mm,11 mm diameter,and 170 mm length intramedullary nails,respectively,followed by assigning material properties,setting the interaction relationship of each contact surface and defining the load and boundary conditions,and then solved.The femoral stress distribution,internal fixation stress distribution,femoral displacement,and internal fixation displacement were observed in different models.RESULTS AND CONCLUSION:(1)The femoral stress was less than that of unreamed intramedullary nail fixation for each type of fracture,and the maximum stress value of the femur for A3.3 fracture was greater than that of A3.1 and A3.2.(2)The internal fixation stress was greater than that of unreamed intramedullary nail fixation for each type of fracture,and the maximum stress value of internal fixation for A3.3 fracture was greater than that of A3.1.(3)Reamed versus unreamed intramedullary nailing has less effect on femoral and internal fixation displacement and more effect on stress.(4)It is indicated that the use of reamed intramedullary nail fixation results in a reduction in femoral stress,an increase in the stress borne by the internal fixation as a whole,and a reduction in the stress borne by the distal locking nail.The use of reamed intramedullary nail fixation may provide better treatment results compared to unreamed intramedullary nail fixation.