Thoracolumbar rotation in ankylosing spondylitis. A new noninvasive measurement method.

Thoracolumbar rotation was measured by a noninvasive method in 135 patients with ankylosing spondylitis. The mean of the total rotation from the level of the xiphisternum to S1 was 45.2 degrees, which is approximately half of that in healthy subjects measured by comparable methods. Rotation had a significant negative correlation with the duration of the disease and with the radiologic degree of lumbar spine involvement, but not with the degree of radiologic sacroiliitis. Reproducibility of the method was good. Measurement of thoracolumbar rotation is seldom used in the assessment of ankylosing spondylitis, and merits further evaluation.