人工全膝关节置换术后单纯金属底座髌骨假体的翻修

目的分析带金属底座髌骨假体失败的原因，并观察单纯髌骨假体翻修的临床疗效。方法对 22例 (30膝 )人工全膝关节置换术后因金属底座髌骨假体失败而行单纯髌骨假体翻修者进行回顾性分析。假体均为同一类型的后十字韧带保留型假体，以金属底座髌骨假体置换髌骨。应用膝关节 KSS评分标准评价翻修术后的临床转归。结果髌骨假体失败时间在人工全膝关节置换术后的 26～ 96个月，平均 62.3个月，主要症状有金属摩擦感 (80％ )和膝关节疼痛 (70％ )。术中发现 23膝 (76.7％ )聚乙烯完全磨损、金属底座外露； 9膝髌骨倾斜或半脱位； 2膝完全脱位。 30膝均成功施行骨水泥全聚乙烯髌骨翻修术，随访时间 24～ 81个月，平均 42.5个月。所有患者主诉症状消失，可独立行走活动，膝关节评分从术前的平均 73分（ 27～ 88分）增加至 87分（ 60～ 100分）；膝关节屈曲度由术前的平均 91°增加至 99.5°。结论 (1)金属底座髌骨假体早期失败率较高； (2)髌骨位线不良和异常滑动轨迹是导致带金属底座髌骨假体失败的诱发因素； (3)单纯髌骨假体翻修可获满意的临床结果，其发生并发症的潜在危险和人工全膝关节翻修术相似，应予以重视。

Isolated metal backed patellar component revision following total knee arthroplasty

Objective To analyse the reasons of failure of metal backed patellar component and observe the clinical outcome of the revision procedure. Methods Thirty isolated patellar revision for failed metal backed patellar components following total knee arthroplasty in 22 patients were reviewed. All had similar total condylar knee prosthesis inserted with retention of the posterior cruciate ligament and resurfacing of the patella. There were 4 males and 18 females. Knee Society Score rating system was used for the final evaluation. Results In average the failure occurred in 62.3 months (ranged from 26 to 96 months). The majority of patients presented with metallic crepitus(80％ ) and pain of the knee(70％ ). At surgery, full thickness polyethylene wear exposing the metal backing was present in 76.7％ with surface damage of the femoral components in 36.7％ . There was tilting of patella in 9 knees and dislocation of patella in 2 knees. All 30 knees underwent successful isolated patellar component revision with cemented polyethylene patellar buttons. Final follow up averaged 42.5 months, all manifestations were reported significant improvement in 22 patients. The average knee score improved from 73 points(ranged from 27 to 88) pre revision to 87 points(ranged from 60 to 100) at the final follow up. Conclusion Resurfacing of the patella in total knee arthroplasty with metal backed patellar components carries a significant risk of early failure. Malalignment and maltracking of patella may be a predisposing factor to early failure in metal backed patellar components.