Kedgley Angela E, Takaki Sarah E, Lang Pencilla, Dunning Cynthia E
Biomechanical Testing Laboratory, Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario N6A 5B9, Canada.
J Biomech Eng. 2007 Jun;129(3):310-4. doi: 10.1115/1.2720907.
Stability of a cemented implant, once the stem-cement interface has debonded, is reliant upon stem geometry and surface finish. There are relatively few studies addressing the effect of cross-sectional stem shape on cemented implant fixation. The purpose of this investigation was to compare the torsional stability of five different stem cross-sectional shapes-circular, oval, triangular, rectangular with rounded edges, and rectangular with sharp edges-under monotonically increasing and cyclic loading conditions. Seven samples of each stem geometry were tested. Stems were potted in bone cement and loaded to 5 deg of rotation. For monotonic loading, torque was applied at a constant rate of 2.5 deg/min. For cyclic loading, a sine wave torque pattern was applied, with a maximum magnitude that began at 4.5 Nm for 1500 cycles and then increased by 2.25 Nm every 1500 cycles until 5 deg of rotation. The rectangular stem with the sharp edges always provided the greatest resistance to torque, followed by the rectangular with rounded edges, triangular, oval, and circular. These results, including the effects of sharp corners, may differ for modes of loading other than torsion. These experimental results support the findings of earlier finite element models, indicating stem shape has a significant effect on resistance to torsional loading.
对于骨水泥型植入物，一旦柄-骨水泥界面脱粘，其稳定性就取决于柄的几何形状和表面光洁度。关于柄的横截面形状对骨水泥型植入物固定效果的研究相对较少。本研究的目的是比较五种不同柄横截面形状（圆形、椭圆形、三角形、带圆角的矩形和带尖角的矩形）在单调递增和循环加载条件下的扭转稳定性。每种柄几何形状测试七个样本。将柄植入骨水泥中，并加载至5度旋转。对于单调加载，以2.5度/分钟的恒定速率施加扭矩。对于循环加载，施加正弦波扭矩模式，最大扭矩从4.5 Nm开始，持续1500个循环，然后每1500个循环增加2.25 Nm，直至旋转5度。带尖角的矩形柄始终提供最大的抗扭阻力，其次是带圆角的矩形、三角形、椭圆形和圆形。除扭转外，这些结果（包括尖角的影响）对于其他加载模式可能有所不同。这些实验结果支持了早期有限元模型的研究结果，表明柄的形状对抗扭加载有显著影响。
