Gkiatas Ioannis, Malahias Michael-Alexander, Xiang William, Meyers Kathleen N, Torres Lisa A, Tarity T David, Rodriguez Jose A, Bostrom Mathias P, Wright Timothy M, Sculco Peter K
Stavros Niarchos Foundation Complex Joint Reconstruction Center, Hospital for Special Surgery, New York, NY.
Department of Biomechanics, Hospital for Special Surgery, New York, NY.
J Arthroplasty. 2021 Sep;36(9):3333-3339. doi: 10.1016/j.arth.2021.04.013. Epub 2021 Apr 22.
Titanium tapered stems (TTS) achieve fixation in the femoral diaphysis and are commonly used in revision total hip arthroplasty. The initial stability of a TTS is critical, but the minimum contact length needed and impact of implant-specific taper angles on axial stability are unknown. This biomechanical study was performed to better guide operative decision-making by addressing these clinical questions.
Two TTS with varying conical taper angles (2° spline taper vs 3.5° spline taper) were implanted in 9 right and left matched fresh human femora. The proximal femur was removed, and the remaining femoral diaphysis was prepared to allow for either a 2 cm (n = 6), 3 cm (n = 6), or 4 cm (n = 6) cortical contact length with each implanted stem. Stepwise axial load was then applied to a maximum of 2600N or until the femur fractured. Failure was defined as either subsidence >5 mm or femur fracture.
All 6 femora with 2 cm of stem-cortical contact length failed axial testing, a significantly higher failure rate (P < .02) than the 4 out of 6 femora and all 6 femora that passed testing at 3 cm and 4 cm, respectively, which were not statistically different from each other (P = .12). Taper angle did not influence success rates, as each matched pair either succeeded or failed at the tested contact length.
4 cm of cortical contact length with a TTS demonstrates reliable initial axial stability, while 2 cm is insufficient regardless of taper angle. For 3 cm of cortical contact, successful initial fixation can be achieved in most cases with both taper angle designs.
钛制锥形柄（TTS）可在股骨干中实现固定，常用于翻修全髋关节置换术。TTS的初始稳定性至关重要，但所需的最小接触长度以及特定植入物锥角对轴向稳定性的影响尚不清楚。进行这项生物力学研究以解决这些临床问题，从而更好地指导手术决策。
将两种具有不同圆锥锥角（2°花键锥度与3.5°花键锥度）的TTS植入9对左右匹配的新鲜人股骨中。切除近端股骨，准备剩余的股骨干，以便每个植入柄的皮质接触长度为2 cm（n = 6）、3 cm（n = 6）或4 cm（n = 6）。然后逐步施加轴向载荷，最大至2600N或直至股骨骨折。失败定义为下沉>5 mm或股骨骨折。
所有6个股骨柄皮质接触长度为2 cm的股骨均在轴向测试中失败，失败率显著高于分别在3 cm和4 cm时通过测试的6个股骨中的4个和所有6个股骨，后两者之间无统计学差异（P = 0.12）。锥角不影响成功率，因为每对匹配的股骨在测试的接触长度下要么成功要么失败。
TTS的皮质接触长度为4 cm时显示出可靠的初始轴向稳定性，而无论锥角如何，2 cm均不足。对于3 cm的皮质接触，两种锥角设计在大多数情况下均可实现成功的初始固定。
