Pruijs J E, Hageman M A, Keessen W, van der Meer R, van Wieringen J C
Department of Orthopaedics, State University, Utrecht, The Netherlands.
Skeletal Radiol. 1994 Oct;23(7):517-20. doi: 10.1007/BF00223081.
In order to determine the reliability of the Cobb angle measurement as it is used in the clinical management of scoliosis, a methodological survey was carried out. In the measurement of a Cobb angle two phases can be distinguished: (a) the production of a spinal radiograph and (b) the measurement of the angle itself. In respect of the first phase, the variation in production of the radiographs was calculated on Cobb angle measurements made by one investigator on serial radiographs of patients who underwent spinal fusion for scoliosis and therefore had a fixed spinal curvature. For the second phase, the accuracy of Cobb angle measurement was investigated by comparing measurements on the same radiographs of 46 scoliosis patients obtained by three investigators, namely two orthopaedic surgeons and an orthopaedic fellow who was assigned to a school screening project. Results were expressed as a Spearman correlation coefficient and a standard deviation of the differences. The Spearman correlation coefficient was 0.98 for the repeated radiographs (production variation) and also 0.98 for the repeated measurements on one radiograph (interobserver measurement variation). The standard deviation of the differences in Cobb angle for the repeated radiographs amounted to 3.2 degrees and for the repeated measurements on one radiograph it was 2.0 degrees. Although there is a good reproducibility of the Cobb angle measurement between different investigators, the variation in production of a spinal radiograph is an important source of error. This should be taken into account when making decisions in scoliosis management.
为了确定用于脊柱侧弯临床管理的Cobb角测量的可靠性，开展了一项方法学调查。在测量Cobb角时可区分两个阶段：(a) 脊柱X光片的生成，以及 (b) 角度本身的测量。关于第一阶段，通过一名研究人员对接受脊柱侧弯脊柱融合术因而脊柱曲率固定的患者的系列X光片进行Cobb角测量，计算X光片生成过程中的变化。对于第二阶段，通过比较三名研究人员（两名骨科医生和一名参与学校筛查项目的骨科住院医师）对46名脊柱侧弯患者的同一X光片的测量结果，研究Cobb角测量的准确性。结果以Spearman相关系数和差异标准差表示。重复X光片（生成变化）的Spearman相关系数为0.98，对一张X光片的重复测量（观察者间测量变化）的Spearman相关系数也为0.98。重复X光片的Cobb角差异标准差为3.2度，对一张X光片的重复测量的差异标准差为2.0度。尽管不同研究人员之间Cobb角测量具有良好的可重复性，但脊柱X光片生成过程中的变化是一个重要的误差来源。在脊柱侧弯管理决策时应考虑到这一点。
