Design and evaluation of a new short stemmed hip implant using porous titanium material to diminish stress shielding

髋关节炎的标准治疗是全髋关节置换术（THA）。尽管THA是一种成功的手术干预，但年轻患者的失败导致寻找替代解决方案，这些解决方案可能更耐用，并可能保留股骨骨量以备将来翻修。微创手术的日益普及导致了保守性种植体的发展。短股骨柄具有保留股骨骨量以备将来翻修的优势。众所周知，在股骨内植入金属器械会改变向周围骨的载荷传递。较短的股骨柄可以以更生理的方式对股骨施加载荷，从而降低应力遮挡的风险。这种现象是由金属和骨之间的刚性差异引起的，导致骨吸收或骨密度降低。随着快速制造工艺的进步，现在可以设计复杂的结构材料，如多孔微结构。多孔金属材料促进骨细胞在结构内生长，导致更好的骨整合，从而更好地将植入物固定到周围骨上。本研究的目的是设计和评估一种新型仿生材料制成的短柄髋关节植入物，以提高关节置换术的长期生存率，采用生物力学建模和有限元分析。该项目包括两个部分。第1部分包括通过研究股骨柄长度对初始稳定性和股骨应力的影响来评价新的短股骨柄植入物。第2部分包括优化多孔钛材料的微观结构，以获得与股骨松质骨相似的力学性能，并研究采用该材料的短柄植入物的骨应力分布和应力遮挡。建议的程序将基于候选人小组以前的建模工作。

Standard treatment of hip arthritis is Total Hip Arthroplasty (THA). Although THA is a successful surgical intervention, failures in younger patients have led to search for alternative solutions which may be more durable and may conserve femoral bone stock for future revision. The increasing popularity of minimally invasive surgery had led to the development of conservative implants. Short stem has the advantage of preserving femoral bone stock for future revision. It is well known that the implantation of a metallic device inside the femur modifies the load transfer to the surrounding bone. Shorter femoral stem may load the femoral bone in a more physiological way and so reduce the risk of stress shielding. This phenomenon, caused by the difference in rigidity between the metal and the bone, leads to bone resorption or decrease of bone density. With the advancement of rapid manufacturing processes, complex structural materials can now be designed such as porous microstructures. Porous metallic materials promote bone cells to grow inside the structure, leading to better osseointegration, consequently better fixation of the implant to the surrounding bone. The aim of this research project is to design and evaluate a short stemmed hip implant made of a new biomimetic material to improve long-term survivorship of the arthroplasty, using biomechanical modeling and finite element analysis. The project foresees two parts. Part 1 consists in evaluating a new short stem implant by investigating the effect of stem length on primary stability and the femoral stresses. Part 2 consists in optimizing the microstructure of the porous titanium material to obtain mechanical properties similar to femoral cancellous bone properties, and investigate bone stress distribution and stress shielding of the short stemmed implant proposed with this material. The proposed program will be based on the previous modeling works of the candidate's group.