全膝关节置换术中不同关节线高度对髌股关节接触压强的影响

Effects of different heights of simulated joint lines on patellofemoral joint contact pressure in total knee arthroplasty

目的:探讨全膝关节置换(TKA)术中不同关节线高度对髌股关节接触压强的影响。方法:取7个关节结构正常、关节软骨完整的正常中国成人的新鲜冷冻尸体膝关节,将标本固定到8501型Instron生物力学测试机上,垂直加载负荷30 kg,改变股四头肌肌腱上的拉力使标本获得平衡,用压敏片测量髌股关节之间的峰值压强。人工膝关节置换术后,测量髌股关节之间的峰值压强;增加股骨侧的截骨量(每次为2 mm,即关节线分别为0、+2、+4、+6 mm),并将胫骨平台作相应的垫高,再次测量髌股关节之间的峰值压强。结果:TKA术后,膝关节屈曲60°、90°和120°时,关节线高度为+4、+6 mm时的外侧髌股关节峰值压强显著高于关节线高度为0、+2 mm时的峰值压强(P<0.05);膝关节屈曲30°、60°、90°和120°时,关节线高度为+6 mm时的内侧髌股关节峰值压强显著高于关节线高度为0、+2、+4 mm时的峰值压强(P<0.05)。结论:全膝关节置换术中,关节线的高度抬高超过4 mm以上就会进一步导致髌股关节的峰值压强增高。TKA术中,应该尽量将关节线的变化控制在4 mm之内。

Objective：To discuss the effects of different joint line heights on patellofemoral joint （PFJ） contact pressure at different knee flexion angles in human cadaveric total knee arthroplasty. Methods, Seven normal fresh-frozen human cadaveric knees with intact joint cartilage were tested on an Instron 8501 testing machine with a load of 30 kg. The load of quadriceps tendon was adjusted to balance the specimen at the desired angles. Total knee arthroplasty were performed with femurs of increased lengths （i. e. the heights of joint line were ＋2 mm, ＋4 mm, and ＋6 mm） and tibial plateaus of different heights. The peak PFJ contact pressure was measured with Fuji pressure-sensitive film before and after total knee arthroplasty. Results： After total knee arthroplasty, at knee flexion angles of 60°,90°and 120°, the peak contact pressures of lateral PFJ facet were significant- ly higher when the heights of joint line were ＋4 mm and ＋6 mm than those when the heights of joint line were 0 and ＋2 mm （P〈0.05）; at knee flexion angles of 30°, 60°, 90°and 120°, the peak contact pressure of medial PFJ facet were significantly higher when the heights of joint line were ＋6 mm than those when the heights of joint line were 0, ＋2 mm, and ＋4 mm （P〈 0.05）. Conelusion： The peak PFJ contact pressure increases if the height of joint line is elevated by more than 4 mm in total knee arthroplasty, so the variation of joint line should be controled within 4 mm in total knee arthroplasty.