Department of Mechanical Engineering, The University of Western Ontario, London, ON, Canada; The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada.
The Roth|McFarlane Hand and Upper Limb Centre, St. Joseph's Hospital, London, ON, Canada; Department of Surgery, The University of Western Ontario, London, ON, Canada.
J Shoulder Elbow Surg. 2018 Dec;27(12):2232-2241. doi: 10.1016/j.jse.2018.06.002. Epub 2018 Aug 10.
Since the advent of stemless implants, several different fixation feature designs have been used to improve primary implant stability. These stemless designs are diverse, and the rationale for their selection and design has not been thoroughly studied. Accordingly, this investigation assessed the effect of stemless implant geometry on the simulated stress and strain response of the proximal humerus.
Five humeral finite element models were used to examine 10 generic stemless implants with variable fixation features (2 central, 4 peripheral, and 4 boundary crossing). Loads representing 45° and 75° of shoulder abduction were simulated. Implants were compared based on the percentage of implant-bone surface area that remained in contact, the change in bone stress relative to the intact state, and the simulated potential for bone to resorb, remodel, or remain unchanged after reconstruction.
The implant-bone contact area was greatest for peripheral, followed by central and boundary-crossing designs. All implants elicited similar bone stress variations, which were greatest 0 to 5 mm beneath the resection and laterally. The simulated potential cortical response was also similar for all implants, with the greatest simulated resorbing potential 0 to 15 mm beneath the resection, and very little expected remodeling. Differences between implants were most prominent within the simulated potential trabecular response, with the central implants having the least bone volume percentage expected to resorb.
Simulated humeral bone response after stemless anatomic shoulder replacement depends on fixation feature geometry. Trade-offs exist between implant types. Centrally pegged implants produced the lowest simulated resorbing potential, whereas peripheral implants had the greatest percentages of implant-bone contact area.
自从无柄植入物问世以来，已经使用了几种不同的固定特征设计来提高初始植入物的稳定性。这些无柄设计多种多样，其选择和设计的原理尚未得到彻底研究。因此，本研究评估了无柄植入物几何形状对肱骨近端模拟应力和应变响应的影响。
使用 5 个肱骨有限元模型来检查具有可变固定特征的 10 种通用无柄植入物（2 个中心，4 个外周和 4 个边界交叉）。模拟了代表肩部外展 45°和 75°的载荷。根据植入物-骨表面面积的百分比、与完整状态相比骨的变化、以及重建后骨吸收、重塑或保持不变的模拟潜力，对植入物进行了比较。
外周设计的植入物-骨接触面积最大，其次是中心和边界交叉设计。所有植入物都引起了相似的骨应力变化，最大的变化在切除部位下 0 到 5mm 处和侧向。所有植入物的模拟皮质反应也相似，最大的模拟吸收潜力在切除部位下 0 到 15mm 处，几乎没有预期的重塑。植入物之间的差异在模拟小梁反应中最为明显，中央植入物的预计吸收骨体积百分比最小。
无柄解剖性肩关节置换术后肱骨的模拟骨反应取决于固定特征的几何形状。植入物类型之间存在权衡。中央带钉植入物产生的模拟吸收潜力最低，而外周植入物的植入物-骨接触面积百分比最大。
