VARIABILITY IN COBB ANGLE MEASUREMENTS IN CHILDREN WITH CONGENITAL SCOLIOSIS

The variability in measurement of angles in congenital scoliosis is no t known, but it is postulated that it is larger than that in adolescen t idiopathic scoliosis due to skeletal immaturity, incomplete ossifica tion, and anomalous development of the end-vertebrae, To determine thi s variability, we selected 54 radiographs of adequate quality showing 67 scoliotic curves from children with congenital scoliosis. The end-v ertebrae were preselected, Each curve was measured by the Cobb method on two separate occasions by six different observers, using the same g oniometer and marker. The intraobserver variability was +/-9.6 degrees and the interobserver variability +/-11.8 degrees, If 'significant pr ogression' is to be used as a criterion for surgical fusion in congeni tal scoliosis, there should be at least a 23 degrees increase, the ent ire range of the interobserver variability, in the curvature to ensure that the perceived increase is not due to variability in measurement.