全膝关节置换中股骨外旋截骨对下肢动态力线的影响

摘要

目的 通过计算机导航技术分析下肢动态力线的变化形式及其影响因素.方法 回顾性分析2013年7月至2013年8月接受计算机导航辅助下初次单侧人工全膝关节置换手术的76例膝关节骨关节炎患者病历资料,男46例,女30例;年龄64～78岁,平均71岁.手术均由同一名熟练掌握计算机导航技术的关节外科医生主刀完成.术中应用后稳定型旋转平台膝关节假体(RP,Depuy,强生公司,美国);计算机导航系统应用美国Stryker(R) Navigation SystemⅡ-Cart.术前运用CT扫描测量股骨远端髁间轴线(intraoperative transepicondylar axis,TEA)与后髁线(posterior condyle axis,PCA)间的夹角,即外旋角(external rotation angle,ERA);术中参考CT测量的ERA、计算机导航系统测量的TEA及Whiteside线进行股骨远端外旋截骨,假体骨水泥固定后记录膝关节在被动、无张力情况下屈曲活动过程中的髋-膝-踝(hip-knee-ankle,HKA)变化,即下肢动态力线的变化数据,并利用回归分析评价其影响因素.结果 与术前CT测量的ERA比较,术中分别以胫骨的前后轴线(股骨滑车最低点与髁间窝最高点之间的连线,AP线)、TEA及AP线与TEA均值(分别以TEA及AP线为参考进行股骨远端外旋截骨所得到ERA的平均值)为参考,由导航系统测量的ERA分别为5.54°±2.86°,5.21°±2.60°,5.34°±2.38 °;几种测量方法得到的结果并无统计学差异.TKA术中膝关节由伸直0°至屈曲90°的过程中下肢动态力线的变化与股骨远端外旋截骨密切相关.根据股骨远端外旋截骨角度的不同,下肢动态力线呈现出内翻、外翻及中立位波动三种变化趋势.结论 膝关节在屈伸过程中下肢力线发生变化;TKA术中股骨远端外旋截骨影响下肢动态力线的变化,其数学模型为反正弦三角函数.%Objective To evaluate the influences of femoral rotation on dynamic alignment of the lower extremity in TKA by computer assisted surgical technology.Methods From July 2013 to August 2013,76 consecutive patients with knee osteoarthritis undergone primary-single TKA in our hospital were enrolled,including 46 males and 30 females,aged from 64 to 78 years (average,71 years).All surgeries were completed by the same professional doctor.The PFC (fixed-bearing posterior stabilized) Sigma rotating-platform was selected for all patients,and computer navigation system (Stryker(R) Navigation System Ⅱ-Cart (Stryker corporation,Kalamazoo,Michigan,USA) was used.External rotation osteotomy of the distal femur during TKA was completed according to the pre-operative external rotation angle (ERA),intraoperative transepicondylar axis (TEA) and anteroposterior (AP) line.Passive dynamic alignment of the lower extremity during knee flexion was recorded.The variation trend of hip-knee-ankle (HKA) alignment and the influences of femoral external rotation osteotomy were analysed.Results ERA calculated by the computer navigation system according to Whiteside line,TEA and the mean of Whiteside line and TEA was 5.54°±2.86°,5.21°±2.60° and 5.34°±2.38°.Compared with the ERA measured by CT,no method was better than the other two.Postoperative deviation of HKA alignment from 0° to 90° flexion was associated with the rotational alignment of the femoral component.Trend of HKA alignment during knee flexion tended to be varus,valgus or neutral according to different angles of external rotation osteotomy of the distal femur.Conclusion The HKA alignment changes during the knee flexions.External rotation osteotomy of the distal femur played a crucial role in determining dynamic HKA alignment in TKA.