Olivecrona H, Olivecrona L, Weidenhielm L, Noz M E, Maguire G Q, Zeleznik M P, Svensson L, Jonson T
Department of Hand Surgery, Södersjukhuset, Stockholm, Sweden.
Acta Radiol. 2003 Nov;44(6):653-61. doi: 10.1080/02841850312331287889.
To validate a CT method for detecting changes in acetabular cup orientation after THA.
26 CT examinations were obtained from a pelvic model with an uncemented acetabular cup. The model position was altered between acquisitions, but the cup axis angle vis-à-vis the pelvis was maintained. Data sets were combined into 37 pairs, each containing a unique positioning error. The pelvi in different examinations were fused, creating transformed volumes. Landmarks corresponding to the cup before and after fusion were placed interactively by two independent examiners. The orientation of the acetabular axis was calculated for each volume and compared across volumes.
Before fusion the mean angle error between the acetabular axes was 4.17 degrees (SD +/- 1.95 degrees ). After fusion the mean angle error was 0.36 degrees (SD +/- 0.17). The 95% repeatability limits were below 0.7 degrees. There was no significant interobserver difference. Analysis of the cup landmarking pattern by condition numbers and individual landmark errors showed stability.
Non-invasive fusion of CT volumes and a stable landmarking pattern for the acetabular cup outperforms routine plain radiography in detecting changes in the orientation of the acetabular axis over time. The method delivers both visual and numerical output and could be used in clinical practice.
验证一种用于检测全髋关节置换术后髋臼杯方向变化的CT方法。
从一个带有非骨水泥髋臼杯的骨盆模型获取了26次CT检查图像。在采集图像期间改变模型位置，但保持髋臼杯轴相对于骨盆的角度不变。将数据集组合成37对，每对包含一个独特的定位误差。将不同检查中的骨盆进行融合，生成变换后的容积。由两名独立的检查人员交互式地放置与融合前后髋臼杯相对应的地标。计算每个容积中髋臼轴的方向，并在各容积之间进行比较。
融合前髋臼轴之间的平均角度误差为4.17度（标准差±1.95度）。融合后平均角度误差为0.36度（标准差±0.17）。95%的重复性极限低于0.7度。观察者间差异无统计学意义。通过条件数和单个地标误差对髋臼地标模式进行分析显示具有稳定性。
CT容积的非侵入性融合以及髋臼杯稳定的地标模式在检测髋臼轴方向随时间的变化方面优于常规X线平片。该方法可提供视觉和数值输出，可用于临床实践。
