Inter- and intraobserver variance of Cobb angle measurements with digital radiographs.

This study compares the intra- and interobserver variance of Cobb angle measurements of primary and secondary curves on digital radiographs versus traditional radiographs. Four orthopaedic surgeons of varying experience measured the Cobb angles from a standard posteroanterior thoracolumbar scoliosis radiograph (25 digital, 25 traditional) on two occasions 2 weeks apart. The intra- and interobserver variances were calculated and compared for major versus minor curves and the digital versus traditional radiographs.