A comparison of methods for measuring spinal motion in female patients with adolescent idiopathic scoliosis

Noninvasive surface measures of spine motion are validated in adult patients but are infrequently used in adolescent scoliosis patients. The agreement between surface and radiographic measurements of spinal motion is not known. We performed a comparative prospective analysis of 3 methods to measure spinal motion in female patients with adolescent idiopathic scoliosis (AIS) to establish normative data of spinal motion in AIS patients and evaluate the relationship between surface and radiographic measurements of spine motion. Measurements were obtained using a cloth tape measure, dual inclinometers, and a 3-dimensional electrogoniometer in 37 female patients with AIS. Radiographic parameters of the deformity were correlated with the spine motion. Differences between methods were evaluated by paired t tests. The Bland-Altman method was applied to evaluate agreement in measuring flexion. The average spinal flexion was 5.7 +/- 2.2 cm by the modified Schober method, 49 +/- 11 degrees by the dual inclinometers method, and 64 +/- 10 degrees by the 3-dimensional electrogoniometer. Spinal motion did not vary with magnitude of the scoliosis. In addition, surface measurements of spinal motion did not correlate with radiographic measurements of scoliosis flexibility. In this study, the amount of spinal motion varied, depending on the method of measurement. Surface measurements of motion cannot predict the magnitude or flexibility of the scoliosis.