Decking Ralf, Puhl Wolfhart, Simon Ulrich, Claes Lutz E
Department of Orthopaedic Surgery, University of Ulm, RKU, Oberer Eselsberg 45, 89075 Ulm, Germany.
Clin Biomech (Bristol). 2006 Jun;21(5):495-501. doi: 10.1016/j.clinbiomech.2005.12.011. Epub 2006 Feb 2.
A number of clinically used total hip femoral implants are claiming a more or less physiologic load transfer, mostly without providing experimental data. To compare three clinically cementless total hip stems of fundamentally different design, the strain distribution before and after insertion in human cadaver femora was measured in vitro.
A conventional straight stem based on a distal anchorage concept, a so-called "anatomic" stem designed to have a proximal force transmission and a "stemless" femoral neck prosthesis were evaluated under similar loading conditions. Strain distribution was measured with tri-axial strain-gauge rosettes before and after implantation of the stems. The same bending moment was used in all femora tested to compare magnitude and direction of the resulting strains.
The straight and the "anatomic" stem both led to a decrease of the longitudinal strains in the proximal femur, while the femoral neck implant mainly led to an increase of measured strains on the lateral side of the greater trochanter. The observed medial strains were closer to physiological values in the "stemless" prosthesis than those of the two full-stem prosthesis.
The decrease in strains seen in the proximal region of the femora with implanted conventional hip prosthesis corresponds well to the decrease of bone density in this region noted in clinical follow-up studies. The more physiological strain at the inferior base of the neck seen in "stemless implant" may induce a remodelling process that better retains bone stock in that area. However, the increase of strains noted after implantation of this prosthesis require further investigation to assess the risk they may pose to bone failure.
许多临床使用的全髋关节股骨植入物都声称能实现或多或少的生理性负荷传递，但大多未提供实验数据。为比较三种设计根本不同的临床非骨水泥型全髋关节柄，在体外测量了它们植入人体尸体股骨前后的应变分布。
在相似的加载条件下，评估了一种基于远端锚固概念的传统直柄、一种设计为近端力传递的所谓“解剖型”柄以及一种“无柄”股骨颈假体。在柄植入前后，用三轴应变片测量应变分布。在所有测试的股骨中使用相同的弯矩，以比较所产生应变的大小和方向。
直柄和“解剖型”柄均导致股骨近端纵向应变降低，而股骨颈植入物主要导致大转子外侧测量应变增加。在“无柄”假体中观察到的内侧应变比两种全柄假体的更接近生理值。
植入传统髋关节假体后股骨近端区域应变的降低与临床随访研究中该区域骨密度的降低非常吻合。“无柄植入物”在颈下部基部观察到的更生理性应变可能会引发一个重塑过程，从而更好地保留该区域的骨量。然而，这种假体植入后应变的增加需要进一步研究，以评估它们可能对骨衰竭造成的风险。
