Jennings L M, Bell C I, Ingham E, Komistek R D, Stone M H, Fisher J
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK.
Proc Inst Mech Eng H. 2007 Apr;221(3):305-14. doi: 10.1243/09544119JEIM215.
In vivo fluoroscopic studies of patients with total knee replacements (TKRs) have shown lift-off of the femoral condyles from the tibial insert. This study investigated the influence of femoral condylar lift-off on the ultra-high molecular weight polyethylene (UHMWPE) wear of fixed bearing (FB) and rotating platform mobile bearing (RP MB) total knee replacements, using a physiological knee joint simulator. In the absence of lift-off, the RP MB knees exhibited a lower wear rate of 5.2 +/- 2.2 mm3 per million cycles (mm3/MC) compared with 8.8 +/- 4.8 mm3/MC for the FB knees. The presence of femoral condylar lift-off was found to accelerate the wear of the FB and RP MB knees tested in this study to 16.4 +/- 2.9 and 16.9 +/- 2.9 mm3/MC respectively. For the RP MB knees the increase in wear rate was more marked, resulting in a similar wear rate for both designs of knee under lift-off conditions. In both cases the medial condyle displayed more wear damage. This study has shown that a small amount of abduction/adduction lift-off and medial-lateral shift increases wear and that the increase in wear is design dependent. In this simulator test, lift-off was simulated on every cycle, whereas the amount of wear and effect of lift-off clinically would depend on the frequency of occurrence of lift-off in vivo.
对全膝关节置换术（TKR）患者进行的体内荧光透视研究显示，股骨髁与胫骨衬垫分离。本研究使用生理膝关节模拟器，调查了股骨髁分离对固定平台（FB）和旋转平台活动轴承（RP MB）全膝关节置换术中超高分子量聚乙烯（UHMWPE）磨损的影响。在没有分离的情况下，RP MB膝关节的磨损率较低，为每百万次循环5.2±2.2立方毫米（mm3/MC），而FB膝关节为8.8±4.8 mm3/MC。研究发现，股骨髁分离的存在会加速本研究中测试的FB和RP MB膝关节的磨损，分别达到16.4±2.9和16.9±2.9 mm3/MC。对于RP MB膝关节，磨损率的增加更为明显，导致在分离条件下两种设计的膝关节磨损率相似。在两种情况下，内侧髁的磨损损伤都更严重。本研究表明，少量的外展/内收分离和内外侧移位会增加磨损，且磨损的增加取决于设计。在这个模拟器测试中，每个循环都模拟了分离，而临床上磨损量和分离的影响将取决于体内分离发生的频率。
