Laboratory of Biomechanics, Justus-Liebig-University, Klinikstrasse 29, Giessen 35392, Germany.
Department of Orthopaedics and Orthopaedic Surgery, University Hospital Giessen, Klinikstrasse 33, Giessen 35392, Germany.
J Biomech Eng. 2020 Dec 1;142(12). doi: 10.1115/1.4047659.
Cementless straight stems show very good survival rates. However, the more distal force application of straight stems may lead to release-related proximal stress-shielding. Nevertheless, this technical brief had the objective of conducting a biomechanical in vitro analysis comparing short stems with established straight stems with respect to their primary torsional stability. Two cementless short hip stems and three cementless straight hip stems were implanted in n = 5 synthetic femora each. Torsional torques were applied into the hip stems at a continuous interval of ±7 Nm. Micromotions were measured by six inductive extensometers on four different measurement levels. At the proximal measuring point, significantly smaller relative micromotions of the CLS® prosthesis could be detected compared to all other stem models (p < 0.05). In all stem models, smallest relative micromotions were found at the metaphyseal/diaphyseal measuring point. Only at the measuring point of the distal tips of the straight stems, statistically significantly lower relative micromotion of the CLS® stem compared to the Trendhip® stem could be found (p < 0.01). All the investigated stems generally display a rather comparable anchoring pattern and an almost physiological force application. Since the comparatively long straight stems present an anchoring pattern nearly identical to that of the examined short stems, a shortening of the established straight stems could be taken into consideration. This would offer the advantage of minimally invasive surgery and bone-saving resection as well as preservation of cancellous bone in case a revision would become necessary.
非骨水泥直柄具有非常高的存活率。然而，直柄更靠近末端的受力方式可能会导致与假体相关的近端应力遮挡。尽管如此，本技术简报的目的是进行一项生物力学体外分析，比较短柄和已确立的直柄在初始抗扭转稳定性方面的差异。将两个非骨水泥短柄髋关节假体和三个非骨水泥直柄髋关节假体分别植入 5 个合成股骨中。髋关节假体以连续间隔 ±7Nm 的扭矩施加扭转力。通过四个不同测量水平上的六个感应式引伸计测量微移动。在近端测量点，CLS®假体的相对微移动明显小于所有其他柄模型（p<0.05）。在所有柄模型中，在近-骨干测量点发现最小的相对微移动。只有在直柄末端尖端的测量点，CLS®柄与 Trendhip®柄相比，相对微移动显著降低（p<0.01）。所有研究的髋关节假体通常显示出相当可比的固定模式和几乎生理的力传递方式。由于相对较长的直柄具有与所研究的短柄几乎相同的固定模式，因此可以考虑缩短已确立的直柄。这将具有微创外科手术和保骨切除的优势，并且在需要翻修时可以保留松质骨。
