TC股骨转子间骨折半髋假体系统的研制及力学测试

目的针对老年不稳定型股骨转子间骨折,研制一套新型半髋假体系统———TC(Trochanteric Prosthesis Sys-tem)半髋假体系统,以保存粗隆部骨量,达到早期功能锻炼的要求。方法选择1名正常成年男性志愿者,对其双侧股骨进行CT薄层扫描,所得图像信息以DICOM格式储存,导入有限元建模软件建立股骨中上段三维模型。利用计算机Pro/E软件进行半髋假体的辅助设计,计算机数控快速成型技术制造半髋假体的金属模型,在尸体骨上反复验证和修改完善后,开模铸造正式假体。将所研制假体模拟植入人体股骨后进行三维有限元分析。选择1名老年男性的新鲜尸体股骨标本,制作A2.2型(AO分型)股骨转子间骨折模型,模拟手术植入装配所研制的半髋假体系统。按照国家行业标准YY0117和YY0118的要求进行材料的性能测试、假体头颈部疲劳测试、假体柄部疲劳测试以及模拟植入新鲜尸体股骨后的抗压、抗扭转等生物力学性能测试。结果新型股骨转子间骨折半髋假体试样的头颈部、柄体部的疲劳性能测试结果 500万次(8 Hz),假体未断裂或失效;植入新鲜尸体股骨后抗压达到2 kN,试样未失效,抗扭转最大扭矩达到15.5 N.m。有限元分析应力云图显示假体柄与股骨接触应力主要由股骨转子部以下的骨干部所承担,最大平均Von Mises应力值为17.6～26.4 MPa,而大、小转子处的应力水平较低,最大平均Von Mises应力值分别为2.7、4.9 MPa。结论本研究所研制的老年不稳定型股骨转子间骨折半髋假体系统具有操作简便、固定牢靠、充分保存转子部骨量的特点,并且能够达到早期功能锻炼的生物力学要求。

Development and mechanical testing on TC hemi-arthroplasty prosthesis system for femoral intertrochanteric fractures

Objective To develop a new hemi-arthroplasty system-Trochanteric Prosthesis System (TC) for the treatment of unstable femoral intertrochanteric fractures in the elderly, so as to preserve bone mass and meet requirement of functional exercises at early stage. Methods A normal male adult volunteer was chosen to receive CT scanning at middle and upper regions of his both intact femur. The serial digitized image data of spiral CT in DICOM format were imported to finite element modeling software to establish a three-dimensional (3D) solid model of the proximal femur. The Pro/E software was used to conduct computer-aided design of the new hemi-arthroplasty prosthesis system and then its metal model was also made by rapid prototyping techniques. After repeated verification and improvement on cadaver femur, the femoral prosthesis was molded and assembled in the solid fracture mode for finite element analysis. The unstable femoral intertrochanteric fracture model obtained from the fresh cadaver of an elderly male was chosen to make A2.2 Type of such fracture model in AO classification system. The new hemi arthroplasty prosthesis system was implanted and assembled into the model and received mechanical testing, including material performance testing, prosthesis head/neck and stem fatigue testing, anti-compression and anti-torsion testing, according to the National Industrial Standard YY0117 and YY0118. Results The sample of new hemi-arthroplasty prosthesis sustained 5 million cycle (8 Hz) fatigue testing on the part of the head-neck and the stem body without any breakage and failure. With the sample implanted into the intertrochanteric fracture model, the maximum compressive strength and torsional strength of the sample reached over 2 kN and 15.5 N?m without failure, respectively. The contact stresses between the stem and the femur were mostly distributed at the region below the femoral trochanter, where the maximum average Von Mises stress values were 17.6~26.4 MPa. Stresses at the region of intertrochanteric fractures were at a low level. The maximum average Von Mises stress values at the greater and lesser trochanter region were 2.7 and 4.9 MPa, respectively. Conclusions The new developed hemi-arthroplasty prosthesis has the advantages of easy performance, reliable fixation, sufficient bone preservation and it is capable of fulfilling the demands of early weight bearing and functional exercises. It is suitable for the treatment of unstable femoral intertrochanteric fractures in the elderly.