Arola D, Stoffel K A, Yang D T
Department of Mechanical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA.
J Biomed Mater Res B Appl Biomater. 2006 Feb;76(2):287-97. doi: 10.1002/jbm.b.30364.
Loosening is recognized as one of the primary sources of total hip replacement (THR) failure. In this study the influence of the bone surface texture on loosening of the cement/bone interface was studied. Model cemented hip replacements were prepared and subjected to cyclic loads that induced pure shear fatigue of the cement/bone interface. The femoral canals were textured with the use of specific cutting tools to achieve a desired surface topography. Loosening of the implant with cyclic loading was characterized in terms of the initial migration (Region I), steady-state loosening (Region II), and unstable loosening (Region III). Results from the experiments showed that the initial migration and rate of steady-state loosening were dependent upon the bone surface topography. The apparent fatigue strength ranged from 0.8 to 5.1 MPa, and denotes the cyclic shear stress required for loosening of 1 mm within 10 million cycles. Regardless of the bone surface topography the ratio of apparent fatigue strength and ultimate shear strength of the interfaces was approximately 0.24. In general, the apparent fatigue strength increased proportional to the average surface roughness of the femoral canal and the corresponding volume available for cement interdigitation. In addition, there was a strong correlation between the normalized initial migration and the apparent fatigue strength (i.e., specimens with the highest initial migration exhibited the lowest fatigue strength).
松动被认为是全髋关节置换术（THR）失败的主要原因之一。在本研究中，研究了骨表面纹理对骨水泥/骨界面松动的影响。制备了模拟骨水泥型髋关节置换物，并对其施加循环载荷，该载荷会导致骨水泥/骨界面出现纯剪切疲劳。使用特定的切削工具对股骨髓腔进行纹理处理，以获得所需的表面形貌。根据初始位移（区域I）、稳态松动（区域II）和不稳定松动（区域III）来表征植入物在循环加载下的松动情况。实验结果表明，初始位移和稳态松动速率取决于骨表面形貌。表观疲劳强度范围为0.8至5.1MPa，表示在1000万次循环内松动1mm所需的循环剪应力。无论骨表面形貌如何，界面的表观疲劳强度与极限剪切强度之比约为0.24。一般来说，表观疲劳强度与股骨髓腔的平均表面粗糙度以及骨水泥相互交错可用的相应体积成正比增加。此外，归一化初始位移与表观疲劳强度之间存在很强的相关性（即，初始位移最高的标本表现出最低的疲劳强度）。
