公式法与K-均值聚类分析法在判断站立位矢状面骨盆前后倾准确性的比较研究

A study to compare the accuracy of a formula and the K-means clustering analysis in determining pelvic inclination in standing position

[目的]通过与标准方法测量对比，比较公式法与K-均值聚类分析法在判断站立位矢状面上骨盆前后倾的准确性。[方法]选取78位健康志愿者（20—65岁）的站立位全脊柱侧位x线片（含髋关节），测量骶骨倾斜角、骨盆倾斜角、骨盆投射角，并采用标准法判读骨盆的前后倾。采用公式法及均值聚类分析进行分析判定骨盆的前后倾，并将结果与标准判定方法进行一致性比较分析，分析符合率。[结果]采用公式法判定的结果中1例不一致，符合率为98．70％，Kappa值=0．965〉0．7，一致性高；K-均值聚类分析法中15例不一致，符合率为80．77％，Kappa值=0．523〉0．4，一致性一般；可以得出公式法较K均值聚类法的符合率更高。[结论]公式法可作为一种准确地评判站立位时骨盆前后倾的方法。

[ Objective] To study the accuracy of a formula and the K -means clustering analysis in determining sagittal pelvic inclination in standing position. [ Methods] The upright standing lateral radiograph of spine and pelvis of 78 healthy vol- unteers （age ranged from 20 years to 65 years） were selected. The sacral slope, pelvic tilt and pelvic incidence were measured then the direction of pelvic inclination was computed by a formula, or K - means clustering analysis. In addition, the direction of pelvic inclination relating to the horizontal plane were determined by two independent observers. The agreements amount pelvic inclination determined by different methods were analyzed. [ Results ] All but one direction of pelvic inclination determined by formula method were same as the direction determined by the clinical observation, showed high agreement （98. 7% ） and consis- tency （kappa = 0. 965 〉 0. 7） between two methods. In contrast, the direction of pelvic inclination determined by K - means clustering analysis was different from those determined by the clinical observation in fifteen subjects, resulted in an agreement rate of 80. 77% and kappa = 0. 523 〉 0.4. The agreement rate between two methods were significant different. [ Conclusion ] The pelvic inclination on sagittal plane could be accurately calculated by the formula method. It can serve as an ahernative method in determining pelvic inclination when the clearly presentation of anterior part of pelvis is not available on X - ray films.