基于髋关节正位X线片可测量髋臼假体方位

目的系统回顾以往基于髋关节正位X线片测量髋臼假体方位的方法，提出更加可靠的测量工具。方法利用Matlab软件建立基于髋关节正位X线片拟合臼杯开口椭圆的新方法，并测量34例全髋关节置换术后臼杯的前倾角和倾斜角。由4名骨科医生完成信度实验，评价该测量方法的观察者间及观察者内信度。结果椭圆二次导数函数图可知，椭圆切线斜率的变化率在长短轴附近最小，距离长短轴端点越近，所选拟合点对拟合椭圆形态的影响也最小。观察者内信度表明：前倾角和倾斜角的组内相关系数ICC分别为0.916（95% CI：0.858~0.954）和0.948（95% CI：0.910~0.972）。观察者间信度结果为：前倾角和倾斜角的组间相关系数ICC分别为0.893（95% CI：0.821~0.941）和0.937（95% CI：0.892~0.966）。结论基于椭圆导数理论，本研究提出了一种基于髋关节正位X线片测量髋臼假体方位的新方法，可以用于临床评价全髋关节置换术后的假体位置。

Imaging study on the orientation of acetabular prosthesis based on orthographic radiographs of hip joint

ObjectiveTo analyze the current measurement methods for determining the indication and antevesion of acetabular cup, and then a new radiographic measurement tool was developed and verified.MethodsBased on the formula of ellipse, the second derivative of ellipse was set up and plotted using the Mathematica software. We analyzed the plot of the second derivative of ellipse and determine the relationship between the slope of ellipse and different points. The best method to select the points of the fitted ellipse was explored. Based on the previous analyses, a new radiographic measurement tool was developed using Matlab software and to calculate the antevesions and indications of 34 acetabular cups after total hip arthrosplasty. The reliability of the current established measurement approach was tested by the intra-class correlation coefficient (ICC).ResultsThe plot of the second derivative of ellipse revealed that the slope of ellipse varied relatively little near the end of the major and minor axises of ellipse. Thus, the selected fitted points near the end of the major and minor axises could influence little on the shape of fitted ellipse. The reliability studies showed that high intraobserver reliability (n=34) was observed in the same observer’s measurements with an ICC between 0.972 and 0.996. A high agreement (n=34) was observed between different observers with an ICC between 0.973 and 0.996. The mean squares within trials ranged from 0.022 to 0.482 with all P values more than 0.05.ConclusionBased on the principle of the derivative of ellipse, a new radiographic measurement tool for determining the indication and antevesion of acetabular cup is developed using Matlab software.