A comparison of radiographic and electrogoniometric angles in adolescent idiopathic scoliosis.

Abstract

This was a cross-sectional study of a consecutive group of adolescent patients presenting to a scoliosis clinic for routine assessment or monitoring of their scoliosis, excluding postsurgical patients. In vitro studies suggested electrogoniometry could be useful in the evaluation of scoliosis. No prior in vitro study had been performed. To determine the reliability and validity of an electrogoniometric instrument, the Metrecom Skeletal Analysis System, in assessing adolescent idiopathic scoliosis. Thirty-one patients were examined, radiographed, and scanned with the Metrecom Skeletal Analysis System twice by two different examiners. The magnitudes of the curves derived from the Metrecom Skeletal Analysis System scans were compared with each other and with the Cobb angles measured from standing radiographs. The intraclass correlation coefficient (a measure of agreement, ranging from 0 to 1, where 1 represents complete agreement) for the intraexaminer reliability of the Metrecom Skeletal Analysis System ranged from 0.71 to 0.83. The interexaminer reliability intraclass correlation coefficient of the Metrecom Skeletal Analysis System was 0.58, with a mean difference between examiners of 5.5 degrees (SD = 5 degrees), and limits of agreement (mean difference +/-2 SD) ranging from -4.5 degrees to 15.6 degrees. The Metrecom Skeletal Analysis System and the radiographically derived Cobb angle correlation was 0.64, but the mean difference between the methods was 3.7 degrees (SD = 11.1), with limits of agreement from 18.4 degrees to 25.9 degrees. The Metrecom Skeletal Analysis System does not provide sufficient clinical precision to substitute for the Cobb angle measured from spinal radiographic measurements in the management of adolescents with scoliosis.