Verdonschot N, Huiskes R
Orthopaedic Research Laboratory, University of Nijmegen, Netherlands.
Biomaterials. 1998 Oct;19(19):1773-9. doi: 10.1016/s0142-9612(98)00088-x.
Although stress analyses have shown that the mechanical endurance of cemented femoral THA reconstructions is served by stems that firmly bond to their cement mantles, retrieval studies suggest that this may be difficult to achieve. Clinical studies with roentgen stereophotogrammetric analyses have shown that stems may gradually debond from their cement mantle. Accepting the fact that stem debonding is unavoidable, stem subsidence and cement stresses can be reduced by increasing stem-cement friction, as indicated by finite element stress analyses. Hence, it can be hypothesized that debonded stems with high surface roughness values would damage the cement mantle to a lesser extent as compared to polished ones. To confirm this hypothesis, tapered stems with polished and rough surface finishes were implanted in cement mantles and cyclically loaded for 1.7 million times. It was investigated how surface roughness affected the damage in the cement mantle, and how it was related to prosthetic subsidence. The polished taper subsided considerably more than the rough one (630 vs. 270 microm at the end of the experiments). In addition, it was found that the polished taper displayed step-wise subsidence, which is probably due to the interaction of stick-slip processes at the interface, associated with creep of the acrylic cement. The rough taper subsided monotonously. Scanning Electron Microscopic (SEM) analysis of the taper-cement structures showed that the rough taper was completely debonded from the cement mantle, creating a gap at the interface, and that many large cement cracks and particles were created. Around the polished taper, only a few cracks were found and the taper-cement interface seemed undamaged. It was concluded that an increased surface roughness does not necessarily lead to a reduction in cement damage. On the contrary, compared to polished ones, debonded rough stems may produce more cement cracks and acrylic cement debris, and provide routes to transport these wear products. Hence, after failure of the stem-cement interface, straight-tapered stems with an increased surface roughness accelerate the failure process due to inferior fail-safe features. Consequently, in vivo subsidence patterns at the stem-cement interface should be considered in combination with the surface finish of the implant. An amount of post-operative subsidence of a rough stem may be much more damaging for the reconstruction than the same amount for a polished stem.
尽管应力分析表明，骨水泥型股骨全髋关节置换术（THA）重建的力学耐久性取决于与骨水泥壳紧密结合的股骨柄，但取出研究表明，这可能难以实现。采用X线立体摄影测量分析的临床研究表明，股骨柄可能会逐渐与骨水泥壳脱粘。考虑到股骨柄脱粘不可避免这一事实，有限元应力分析表明，增加股骨柄与骨水泥之间的摩擦力可以减少股骨柄下沉和骨水泥应力。因此，可以推测，与表面光滑的股骨柄相比，表面粗糙度值高的脱粘股骨柄对骨水泥壳的损伤程度较小。为了验证这一假设，将表面光滑和粗糙的锥形股骨柄植入骨水泥壳中，并进行170万次循环加载。研究了表面粗糙度如何影响骨水泥壳的损伤，以及它与假体下沉的关系。表面光滑的锥形股骨柄下沉量比表面粗糙的股骨柄大得多（实验结束时分别为630微米和270微米）。此外，还发现表面光滑的锥形股骨柄呈现阶梯式下沉，这可能是由于界面处粘滑过程的相互作用以及丙烯酸骨水泥的蠕变所致。表面粗糙的锥形股骨柄则单调下沉。对股骨柄-骨水泥结构的扫描电子显微镜（SEM）分析表明，表面粗糙的锥形股骨柄与骨水泥壳完全脱粘，在界面处形成间隙，并且产生了许多大的骨水泥裂缝和颗粒。在表面光滑的锥形股骨柄周围，仅发现少数裂缝，股骨柄-骨水泥界面似乎未受损。研究得出结论，表面粗糙度增加不一定会减少骨水泥损伤。相反，与表面光滑的股骨柄相比，脱粘的表面粗糙股骨柄可能会产生更多的骨水泥裂缝和丙烯酸骨水泥碎片，并为这些磨损产物的运输提供途径。因此，在股骨柄-骨水泥界面失效后，表面粗糙度增加的直锥形股骨柄由于其较差的故障安全特性会加速失效过程。因此，在考虑股骨柄-骨水泥界面的体内下沉模式时，应结合植入物的表面光洁度。粗糙股骨柄术后一定量的下沉对重建的损害可能比相同下沉量的表面光滑股骨柄大得多。
