Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, India.
Department of Mechanical Engineering, Imperial College London, London, UK.
Proc Inst Mech Eng H. 2024 May;238(5):471-482. doi: 10.1177/09544119241244537. Epub 2024 Apr 21.
The use of uncemented stems in hip arthroplasty has been increasing, even in osteoporotic patients. The major concerns of uncemented hip-stems, however, are peri-prosthetic fracture, thigh pain, and proximal femoral stress-/strain-shielding. In this study, a novel design of uncemented hip-stem is proposed that will reduce such concerns, improve osseointegration, and benefit both osteoporotic and arthritic patients. The stem has a central titanium alloy core surrounded by a set of radial buttresses that are partly porous titanium, as is the stem tip. The aim of the study was to investigate the mechanical behaviour of the proposed partly-porous design, examining load transfer in the short-term, and comparing its strain-shielding behaviour with a solid metal implant. The long-term effect of implant-induced bone remodelling was also simulated. Computed tomography based three-dimensional finite element models of an intact proximal femur, and the same femur implanted with the proposed design, were developed. Peak hip contact and major muscle forces corresponding to level-walking and stair climbing were applied. The proposed partly-porous design had approximately 50% lower strain-shielding than the solid-metal counterpart. Results of bone remodelling simulation indicated that only 16% of the total bone volume is subjected to reduction of bone density. Strain concentrations were observed in the bone around the stem-tip for both solid and porous implants; however, it was less prominent for the porous design. Lower strain-shielding and reduced bone resorption are advantageous for long-term fixation, and the reduced strain concentration around the stem-tip indicates a lower risk of peri-prosthetic fracture.
在髋关节置换术中，即使是骨质疏松患者，也越来越多地使用非骨水泥型股骨柄。然而，非骨水泥型髋关节股骨柄的主要关注点是假体周围骨折、大腿疼痛和股骨近端的应力/应变屏蔽。在这项研究中，提出了一种新型的非骨水泥型髋关节股骨柄设计，旨在减少这些问题，改善骨整合，并使骨质疏松症和关节炎患者受益。该柄由中心钛合金芯和一组部分多孔钛的放射状支柱组成，柄尖端也是部分多孔钛。该研究的目的是研究所提出的部分多孔设计的力学行为，研究短期的载荷传递，并比较其应变屏蔽行为与实心金属植入物。还模拟了植入物诱导的骨重塑的长期影响。建立了完整的近端股骨和植入所提出设计的相同股骨的基于 CT 的三维有限元模型。施加了对应于水平行走和爬楼梯的髋关节接触峰值和主要肌肉力。与实心金属对应物相比，所提出的部分多孔设计的应变屏蔽大约降低了 50%。骨重塑模拟的结果表明，只有 16%的总骨体积会降低骨密度。对于实心和多孔植入物，在柄尖端周围的骨中都观察到了应变集中；然而，对于多孔设计，应变集中现象不太明显。较低的应变屏蔽和减少的骨吸收有利于长期固定，并且柄尖端周围的应变集中降低表明假体周围骨折的风险较低。
