The Implant Biomechanics Laboratory of the J. Vernon Luck, Sr., M.D. Orthopaedic Research Center, Los Angeles Orthopaedic Hospital-UCLA, 2400 South Flower Street, Los Angeles, CA 90007, USA.
J Biomech. 2011 Jan 11;44(2):235-43. doi: 10.1016/j.jbiomech.2010.10.006. Epub 2010 Oct 30.
Long-term clinical follow-up studies have shown that radiolucent lines at the cement interfaces of total hip replacement femoral components develop gradually, ultimately leading to loosening. In this experimental study, 32 synthetic femurs implanted with cemented femoral components were cyclically loaded with a dynamic joint reaction force, torque, and muscle force, to assess the relative effects of surface finish and collars on interface fixation. Four each of four otherwise identical straight femoral stems, varying only in surface finish and presence or lack of collars were used. Specimens were tested under two conditions: (1) with intact interfaces simulating immediate post-operative conditions and (2) with a thin-film at the stem-cement interface, simulating conditions several weeks to months post-operative when fibrous tissue has formed with the implant still stable. Micromotion was measured at both interfaces in three directions. Surface finish had a larger relative effect than collars, regardless of whether or not a thin-film was present. For example, a proximal grit-blasted finish enhanced fixation at the stem-cement interface by 7-12 μm per-cycle (p<0.05) and decreased early cement mantle loosening by 7-13 μm. For straight stems, rougher surfaces provided greater stability than polished, even with a thin film at the stem-cement interfaces, contradicting the theory that once debonded, rough stems are less stable than polished at the stem-cement interface. The findings of this experimental study exemplify the need to take advantage of all available tools for the preclinical evaluation of orthopaedic implants, including long-term clinical observations of related devices, analytical and numeric models, and experimental bench-top simulations.
长期临床随访研究表明，全髋关节置换股骨假体的水泥界面处的透光线逐渐发展，最终导致松动。在这项实验研究中，32 根植入带水泥股骨假体的合成股骨接受了动态关节反作用力、扭矩和肌肉力的周期性加载，以评估表面光洁度和领圈对界面固定的相对影响。使用了四种各四个完全相同的直股骨柄，仅在表面光洁度和是否存在领圈方面有所不同。在两种情况下测试了标本：（1）具有完整界面，模拟术后即刻条件；（2）具有在柄-水泥界面的薄膜，模拟术后数周到数月时的条件，此时纤维组织已形成，但植入物仍稳定。在三个方向上测量了两个界面的微动。无论是否存在薄膜，表面光洁度的相对影响都大于领圈。例如，近端喷砂处理的表面光洁度使柄-水泥界面的固定增加了 7-12 μm/周期（p<0.05），并使早期水泥覆盖层松动减少了 7-13 μm。对于直柄，粗糙表面比抛光表面提供了更大的稳定性，即使在柄-水泥界面存在薄膜，这与一旦脱粘，粗糙表面在柄-水泥界面的稳定性不如抛光表面的理论相矛盾。这项实验研究的发现例证了需要利用所有可用的工具来进行骨科植入物的临床前评估，包括对相关设备的长期临床观察、分析和数值模型以及实验台模拟。
