Willegger Madeleine, Holinka Johannes, Nemecek Elena, Bock Peter, Wanivenhaus Axel Hugo, Windhager Reinhard, Schuh Reinhard
Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
Foot and Ankle Unit, Orthopaedic Hospital Vienna-Speising, Vienna, Austria.
PLoS One. 2016 Apr 28;11(4):e0154224. doi: 10.1371/journal.pone.0154224. eCollection 2016.
Accurate measurement of the tibiotalar alignment is important in radiographic outcome assessment of ankle arthrodesis (AA). In studies, various radiological methods have been used to measure the tibiotalar alignment leading to facultative misinterpretation of results. However, to our knowledge, no previous study has investigated the reliability of tibiotalar alignment measurement in AA. We aimed to investigate the reliability of four different methods of measurement of the frontal and sagittal tibiotalar alignment after AA, and to further clarify the most reliable method for determining the longitudinal axis of the tibia.
Thirty-eight weight bearing anterior to posterior and lateral ankle radiographs of thirty-seven patients who had undergone AA with a two screw fixation technique were selected. Three observers measured the frontal tibiotalar angle (FTTA) and the sagittal tibiotalar angle (STTA) using four different methods. The methods differed by the definition of the longitudinal tibial axis. Method A was defined by a line drawn along the lateral tibial border in anterior to posterior radiographs and along the posterior tibial border in lateral radiographs. Method B was defined by a line connecting two points in the middle of the proximal and the distal tibial shaft. Method C was drawn "freestyle"along the longitudinal axis of the tibia, and method D was defined by a line connecting the center of the tibial articular surface and a point in the middle of the proximal tibial shaft. Intra- and interobserver correlation coefficients (ICC) and repeated measurement ANOVA were calculated to assess measurement reliability and accuracy.
All four methods showed excellent inter- and intraobserver reliability for the FTTA and the STTA. When the longitudinal tibial axis is defined by connecting two points in the middle of the proximal and the distal tibial shaft, the highest interobserver reliability for the FTTA (ICC: 0.980; CI 95%: 0.966-0.989) and for the STTA (ICC: 0.997; CI 95%: 0.996-0.999) is provided. Intergroup analysis for FTTA measurements revealed a statistically significant difference between the method in which the lateral border of the tibia was used to determine the longitudinal axis of the tibia, and the other methods in which the longitudinal axis was defined by bisecting the tibia.
When the longitudinal axis of the tibia is defined by connecting two points in the middle of the proximal and the distal tibial shaft for measuring the FTTA and STTA, the most favorable interobserver reliability is provided. Therefore, this method can be recommended for evaluating the frontal and the sagittal alignment on anterior to posterior and lateral radiographs after ankle arthrodesis.
在踝关节融合术（AA）的影像学结果评估中，准确测量胫距关节对线情况非常重要。在研究中，已使用各种放射学方法来测量胫距关节对线情况，这导致了结果的随意解读。然而，据我们所知，此前尚无研究调查AA中胫距关节对线测量的可靠性。我们旨在研究AA后测量额状面和矢状面胫距关节对线的四种不同方法的可靠性，并进一步明确确定胫骨纵轴的最可靠方法。
选取37例行双螺钉固定技术AA的患者的38张负重位踝关节前后位和侧位X线片。三名观察者使用四种不同方法测量额状面胫距角（FTTA）和矢状面胫距角（STTA）。这些方法因胫骨纵轴的定义不同而有所差异。方法A通过在前后位X线片上沿胫骨外侧缘绘制的线以及在侧位X线片上沿胫骨后缘绘制的线来定义。方法B通过连接胫骨近端和远端中部两点的线来定义。方法C沿胫骨纵轴“自由绘制”，方法D通过连接胫骨关节面中心和胫骨近端中部一点的线来定义。计算观察者内和观察者间相关系数（ICC）以及重复测量方差分析，以评估测量的可靠性和准确性。
所有四种方法在测量FTTA和STTA时均显示出优异的观察者间和观察者内可靠性。当通过连接胫骨近端和远端中部两点来定义胫骨纵轴时，FTTA（ICC：0.980；95%CI：0.966 - 0.989）和STTA（ICC：0.997；95%CI：0.996 - 0.999）的观察者间可靠性最高。FTTA测量的组间分析显示，使用胫骨外侧缘确定胫骨纵轴的方法与通过平分胫骨定义纵轴的其他方法之间存在统计学显著差异。
当通过连接胫骨近端和远端中部两点来定义胫骨纵轴以测量FTTA和STTA时，可提供最有利的观察者间可靠性。因此，该方法可推荐用于评估踝关节融合术后前后位和侧位X线片上的额状面和矢状面对线情况。
