Accuracy and repeatability of a new method for measuring scoliosis curvature

A prospective diagnostic clinical trial.

To evaluate the accuracy, repeatability of a new method for measuring spinal curvature in patients with scoliosis, the axis-line-distance technique (ALDT), in comparison with the Cobb method.

Timely and accurate determination of the degree of lateral curvature of the spine is essential for deciding the appropriate treatment method for scoliosis. Although the Cobb method has been accepted as the clinical standard for 60 years, many investigators have reported a high degree of variance in the measurements of spinal curvature obtained using this method. Therefore, the development of an alternative method that incorporates the advances in imaging technology and assessment is needed.

Sixty-five scoliosis patients were evaluated by 6 physician observers. The spinal curves were measured on 2 separate occasions using the Cobb method and the ALDT on a picture archiving and communication system workstation. The time interval between the 2 measurements was 3 weeks, and the data were analyzed by a paired-sample Student t test and Pearson correlation method using SPSS 12.0 software package.

Intraobserver variance of the 2 measurements, the minimum variance, the maximum variance, and the mean and standard deviation values were 0 degrees, 26 degrees, and 5.14 degrees +/- 0.69 degrees for the Cobb method, and 0 mm, 20 mm, and 2.55 +/- 0.38 mm for the ALDT, respectively. There was a significant intraobserver difference in the Cobb angle measurements among 3 of the 6 observers (P < 0.05). No significant intraobserver variance in ALDT measurements was detected. The mean interobserver measurement variance for the Cobb method was 6.54 degrees +/- 1.35 degrees, significantly greater than that for the ALDT (3.58 +/- 0.93 mm; P < 0.05). There were significant positive correlation between the ALDT and the Cobb measurements (r = 0.73, P < 0.05).

The ALDT is more reliable, reproducible, and straightforward, and less error-prone than the Cobb method for measurements of spinal curvature.