Verdonschot N, Tanck E, Huiskes R
Orthopaedic Research Laboratory, University of Nijmegen, The Netherlands.
J Biomed Mater Res. 1998 Dec 15;42(4):554-9. doi: 10.1002/(sici)1097-4636(19981215)42:4<554::aid-jbm11>3.0.co;2-k.
Retrieval studies suggest that the loosening process of the cemented femoral components of total hip arthroplasties is initiated by failure of the bond between the prosthesis and the cement mantle. Finite element (FE) analyses have demonstrated that stem-cement debonding has stress-producing effects in the cement mantle. High interface friction, which corresponds to a degree of surface roughness, reduces these stresses. In experiments, however, debonded rough stems produced more cement damage than polished ones; in the Swedish Hip Register polished stems were clinically superior with respect to stems with a mat surface finish. The purpose of the present study was to investigate this contradiction. For this purpose, global and local FE models with debonded stem-cement interfaces were used to study the effects of prosthesis surface roughness on the cement stresses on a global scale and microscale, respectively. Similar to earlier numerical studies, the global FE model predicted that an increased surface roughness of the stem reduced the stresses in the cement mantle. The local model provided insight in the load-transfer mechanism on a microscale and could explain the experimental and clinical findings. The local cement peak stresses around the asperities of the surface roughness profile increased with increasing surface roughness and decreased again beyond a particular roughness value. Cement abrasion is caused by localized stresses in combination with micromotion. From this study it can be concluded that to minimize cement abrasion, debonded stems should either have a polished microstructure to minimize the local cement stresses or have a profiled macrostructure to minimize micromotions at the stem-cement interface.
检索研究表明，全髋关节置换术中骨水泥固定型股骨假体的松动过程始于假体与骨水泥套之间的粘结失效。有限元（FE）分析表明，柄-骨水泥脱粘会在骨水泥套中产生应力。与一定程度的表面粗糙度相对应的高界面摩擦力会降低这些应力。然而，在实验中，脱粘的粗糙柄比抛光柄产生的骨水泥损伤更多；在瑞典髋关节注册中心，抛光柄在临床效果上优于表面为磨砂处理的柄。本研究的目的是调查这一矛盾。为此，分别使用具有柄-骨水泥脱粘界面的全局和局部有限元模型来研究假体表面粗糙度对骨水泥应力在全局尺度和微观尺度上的影响。与早期的数值研究类似，全局有限元模型预测柄表面粗糙度的增加会降低骨水泥套中的应力。局部模型揭示了微观尺度上的载荷传递机制，并可以解释实验和临床结果。表面粗糙度轮廓的凸起周围的局部骨水泥峰值应力随着表面粗糙度的增加而增加，并在超过特定粗糙度值后再次降低。骨水泥磨损是由局部应力与微动共同引起的。从这项研究可以得出结论，为了使骨水泥磨损最小化，脱粘的柄要么具有抛光的微观结构以最小化局部骨水泥应力，要么具有成型的宏观结构以最小化柄-骨水泥界面处的微动。
