全膝关节置换术的假体旋转力线不良与髌股关节并发症

目的应用CT技术测量股骨假体和胫骨假体旋转角度,探讨假体旋转性和髌股关节并发症之间的关系。方法以股骨上髁轴和胫骨结节为参考点,对股骨假体和胫骨假体的旋转性进行测量,并比较了20例功能良好膝关节和30例产生髌股关节并发症的膝关节的假体旋转性。结果髌股关节并发症组的假体(股骨 胫骨)存在过度内旋,其内旋度数和值与髌股关节并发症的严重程度成正相关。轻度假体内旋(和值1°～4°)导致髌骨倾斜和轨迹外移;中度假体内旋(和值3°～8°)导致髌骨半脱位;重度假体内旋(和值7°～17°)导致早期的髌骨脱位和晚期的髌骨置换失败。功能良好组的假体旋转度和值为10°～0°外旋。结论在轴向力线正常时,假体的内旋放置可能是导致髌股关节并发症的主要原因;利用 CT扫描图像,行假体旋转度测量可用于术中以指导手术,术后也可以作为是否需要翻修的评价指标。

Rotational malalignment causing patellofemoral complications after total knee replacement

OBJECTIVE: To study the rotation of femoral component and tibial component with CT and evaluate the relationship between patellofemoral complications and rotational alignment of the components. METHODS: Thirty patients with isolated patellofemoral complications after total knee arthroplasty were compared with 20 patients with well functioning total knee replacements free of patellofemoral complications. The epicondylar axis and tibial tubercle were used as references on CT scans to quantify the rotational alignment of the femoral and tibial components. RESULTS: Patients with patellofemoral complications had excessive combined (tibial plus femoral) internal component rotation, which was directly proportional to the severity of the patellofemoral complications. Mild combined internal rotation (1 degree-4 degrees) was correlated with patellar and lateral tracking tilting, moderate rotation (3 degrees-8 degrees) with patellar subluxation, and severe rotation (7 degrees-17 degrees) with early patellar dislocation or late patellar prosthesis failure. The control group had combined external rotation of 10 degrees-0 degree. CONCLUSIONS: The direct correlation of combined internal component rotation to the severity of the patellofemoral complication suggests that internal component rotation may be the predominant cause of patellofemoral complications in patients with normal axis alignment. CT scans can be used intraoperatively and postoperatively to determine whether the rotational malalignment is present to require revision of one or both components.