Coxa Ltd, Hospital for Joint Replacement, Tampere, Finland.
Int Orthop. 2012 Mar;36(3):519-25. doi: 10.1007/s00264-011-1328-1. Epub 2011 Aug 12.
Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra- and inter-observer reliability of this method.
Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intra-observer reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements.
Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from -3.2 to -8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from -2.7 to -6.0 degrees.
Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use.
确定金属对金属髋关节表面置换术后的杯倾斜角度可以提供术后随访的重要信息。我们提出了一种基于先前描述的方法的数学方法，用于评估金属对金属轴承中杯的版本和倾斜度，而无需从普通射线照片进行单独的软件计算。本研究的目的是评估该方法的观察者内和观察者间可靠性。
由四位观察者对 20 例髋关节表面置换术进行了两次版本和倾斜度的计算。通过两个版本的平均误差和相关性来评估观察者内的可靠性。通过 Bland-Altman 图、组内系数和平均误差来评估测量的观察者间可靠性。
观察者内版本测量的相关性范围为 0.74 至 0.94。倾斜度的相关性在 0.94 至 0.97 之间。观察者之间版本测量的 Bland-Altman 图的上下限差异分别为 4.1 至 7.2 度和-3.2 至-8.3 度。对于倾斜度测量，上限和下限分别为 3.1 至 5.3 度和-2.7 至-6.0 度。
平均误差、相关系数和 95%的一致性都处于可接受的水平。我们认为该方法适用于临床应用。
