Katz Yekutiel, Lubovsky Omri, Yosibash Zohar
School of Mechanical Engineering, Faculty of Engineering, Tel-Aviv University, Ramat-Aviv, Israel.
Department of Orthopedic Surgery, Barzilai Medical Center, Ashqelon, Israel.
Clin Biomech (Bristol). 2018 Oct;58:74-89. doi: 10.1016/j.clinbiomech.2018.06.012. Epub 2018 Jun 30.
Over 1.6 million hip replacements are performed annually in Organisation for Economic Cooperation and Development countries, half of which involve cemented implants. Quantitative computer tomography based finite element methods may be used to assess the change in strain field in a femur following such a hip replacement, and thus determine a patient-specific optimal implant. A combined experimental-computational study on fresh frozen human femurs with different cemented implants is documented, aimed at verifying and validating the methods.
Ex-vivo experiments on four fresh-frozen human femurs were conducted. Femurs were scanned, fractured in a stance position loading, and thereafter implanted with four different prostheses. All femurs were reloaded in stance positions at three different inclination angles while recording strains on bones' and prosthesis' surfaces. High-order FE models of the intact and implanted femurs were generated based on the computer tomography scans and X-ray radiographs. The models were virtually loaded mimicking the experimental conditions and FE results were compared to experimental observations.
Strains predicted by finite element analyses in all four femurs were in excellent correlation with experimental observations FE = 1.01 × EXP - 0.07,R = 0.976, independent of implant's type, loading angle and fracture location.
Computer tomography based finite element models can reliably determine strains on femur surface and on inserted implants at the contact with the cement. This allows to investigate suitable norms to rank implants for a patient-specific femur so to minimize changes in strain patterns in the operated femur.
在经济合作与发展组织国家，每年进行超过160万例髋关节置换手术，其中一半涉及骨水泥固定植入物。基于定量计算机断层扫描的有限元方法可用于评估髋关节置换术后股骨应变场的变化，从而确定针对特定患者的最佳植入物。本文记录了一项针对不同骨水泥固定植入物的新鲜冷冻人体股骨的实验与计算相结合的研究，旨在验证和确认这些方法。
对四根新鲜冷冻人体股骨进行体外实验。对股骨进行扫描，在站立位加载下使其骨折，然后植入四种不同的假体。所有股骨在三个不同倾斜角度的站立位再次加载，同时记录骨骼和假体表面的应变。基于计算机断层扫描和X射线照片生成完整和植入后股骨的高阶有限元模型。对模型进行虚拟加载以模拟实验条件，并将有限元结果与实验观察结果进行比较。
在所有四根股骨中，有限元分析预测的应变与实验观察结果具有极好的相关性（有限元=1.01×指数-0.07，R=0.976），与植入物类型、加载角度和骨折位置无关。
基于计算机断层扫描的有限元模型能够可靠地确定股骨表面以及与骨水泥接触的植入物上的应变。这有助于研究合适的标准，以便对针对特定患者股骨的植入物进行排名，从而使手术股骨中的应变模式变化最小化。
