Olivecrona Henrik, Weidenhielm Lars, Olivecrona Lotta, Beckman Mats O, Stark André, Noz Marilyn E, Maguire Gerald Q, Zeleznik Michael P, Svensson Lars, Jonson Torbjörn
Department of Hand Surgery, Södersjukhuset, SE-118 83 Stockholm, Sweden.
Acta Orthop Scand. 2004 Jun;75(3):252-60. doi: 10.1080/00016470410001169.
It is difficult to assess the orientation of the acetabular component on routine radiographs. We present a method for determining the spatial orientation of the acetabular component after total hip arthroplasty (THA) using computed tomography.
Two CT-scans, 10 min apart, were obtained from each of 10 patients after THA. Using locally developed software, two independent examiners measured the orientation of the acetabular component in relation to the pelvis. The measurements were repeated after one week. To be independent of the patient position during scanning, the method involved two steps. Firstly, a 3D volumetric image of the pelvis was brought into a standard pelvic orientation, then the orientation of the acetabular component was measured. The orientation of the acetabular component was expressed as operative anteversion and inclination relative to an internal pelvic reference coordinate system. To evaluate precision, we compared measurements across pairs of CT volumes between observers and trials.
Mean absolute interobserver angle error was 2.3 degrees for anteversion (range 0-6.6 degrees), and 1.1 degrees for inclination (range 0-4.6 degrees). For interobserver measurements, the precision, defined as one standard deviation, was 2.9 degrees for anteversion, and 1.5 degrees for inclination. A Student's t-test showed that the overall differences between the examiners, trials, and cases were not significant. Data were normally distributed and were not dependent on examiner or trial.
We conclude that the implant angles of the acetabular component in relation to the pelvis could be detected repeatedly using CT, independently of patient positioning.
在常规X线片上很难评估髋臼假体的方向。我们提出一种使用计算机断层扫描（CT）来确定全髋关节置换术（THA）后髋臼假体空间方向的方法。
对10例接受THA的患者，在术后分别获取间隔10分钟的两次CT扫描图像。使用自行开发的软件，两名独立的检查者测量髋臼假体相对于骨盆的方向。一周后重复测量。为了不受扫描时患者体位的影响，该方法包括两个步骤。首先，将骨盆的三维容积图像调整到标准骨盆方向，然后测量髋臼假体的方向。髋臼假体的方向以相对于骨盆内部参考坐标系的手术前倾角和倾斜角表示。为评估精度，我们比较了观察者之间和不同测量之间CT容积对的测量结果。
观察者间前倾角的平均绝对角度误差为2.3度（范围0 - 6.6度），倾斜角为1.1度（范围0 - 4.6度）。对于观察者间测量，定义为一个标准差的精度，前倾角为2.9度，倾斜角为1.5度。Student t检验显示检查者、测量次数和病例之间的总体差异不显著。数据呈正态分布，且不依赖于检查者或测量次数。
我们得出结论，使用CT可以反复检测髋臼假体相对于骨盆的植入角度，且不受患者体位的影响。
