全膝关节置换术的假体旋转不良的CT分析

Analysis of CT imaging for rotational malalignment in total knee arthroplasty

目的应用CT技术测量全膝关节置换术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。方法以股骨髁上轴和胫骨结节为参考点,对股骨假体和胫骨假体的旋转角度进行测量,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(1°～4°)导致髌骨倾斜和轨迹外移;中度假体内旋(3°～8°)导致髌骨半脱位;重度假体内旋(7°～17°)导致早期的髌骨脱位和晚期的髌骨置换失败。功能良好组的假体外旋10°～0°。结论在机械轴线正常时,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。

Objective To study the rotation value of femoral component and tibial component by a computed tomography technique, evaluate the relationship between rotational alignment of components and patellofemoral complications. Methods Thirty patients with isolated patellofemoral complications after total knee arthroplasty were compared with 20 patients with well functioning total knee replacements without patellofemoral complications. The epicondylar axis and tibial tubercle were used as references on CT scans to measure quantitatively rotational alignment of the femoral and tibial components. Results The group with patellofemoral complications had excessive combined （tibial plus femoral） internal component rotation. This excessive combined internal rotation was directly proportional to the severity of the patellofemoral complication. Small amouts of combined internal rotation （1°- 4°） correlated with lateral tracking and patellar tilting. Moderate combined internal rotation （3°- 8°） correlated with patellar subluxation. Large amounts of combined internal rotational （ 7°-17°） correlated with early patellar dislocation or late patellar prosthesis failure. The control group was in combined external rotation （10°-0°）. Conclusion 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. Computed tomography scans can be used intraoperatively and postoperatively. This study can determine whether rotational malalignment is present and thus, whether revision of one or both components may be indicated.