Measurement accuracy in congenital scoliosis.

Background: The accuracy of measurement of curves in idiopathic scoliosis has been extensively studied; however, we know of only one article in the literature concerning the accuracy of measurement of curves in congenital scoliosis. That article stated that intraobserver variability was +/- 9.6 degrees and interobserver variability was +/- 11.8 degrees.

Methods: Sixty-nine curves in fifty patients with congenital scoliosis were measured on two separate occasions by seven different observers with varying experience in curve measurement.

Results: Mean intraobserver variance ranged from 1.9 degrees to 5.0 degrees, with an average of 2.8 degrees (95% confidence limit, +/- 3 degrees) for the seven observers. The interobserver variance was 3.35 degrees (95% confidence limit, 7.86 degrees).

Conclusions: It is possible to measure curves in congenital scoliosis with much greater accuracy than previously reported. In the clinical situation in which a skilled observer can measure two radiographs at the same time, an accuracy of +/- 3 degrees can be expected 95% of the time.