Multisurgeon assessment of coronal pattern classification systems for adolescent idiopathic scoliosis - Reliability and error analysis

Study Design. Three scoliosis surgeons and one orthopedic fellow were presented the anteroposterior radiographs of 70 patients with adolescent idiopathic scoliosis. All the reviewers assigned a type to each curve according to the classification systems of H. A. King and R. W. Coonrad. Objectives. To compare multisurgeon reliability in applying the classification systems of H. A. King and R. W. Coonrad, and to analyze controversially classified curve patterns. Summary of Background Data. The system most commonly used to classify adolescent idiopathic scoliosis is King's classification. However, because of poor interobserver reliability, the validity of this system is questioned. In contrast, high interobserver reliability is reported for Coonrad's classification system, which is used less frequently in clinical practice. Methods. Interobserver agreement and intraobserver reproducibility were tested. Kappa coefficients were used to test reliability. Between the observers, the divergent assignments to curve patterns were analyzed in both quantitative and qualitative terms. An error analysis was performed. Results, Paired comparisons showed a mean interobserver kappa coefficient of 0.45 for King's and 0.38 for Coonrad's classification systems. According to Svanhoim et al, these values indicate poor reliability in terms of interobserver agreement. Error analyses for both classification systems showed that the reason for poor reproducibility is disagreement among the observers about structural upper thoracic and structural lumbar curves. Conclusions. Neither the King nor the Coonrad method appears to have sufficient interobserver reliability. To improve reliability, the authors recommend that the structural stigmas of the upper thoracic and lumbar curves be unequivocally described.