Inter-observer and intra-observer reliability of the Risser sign in a metropolitan scoliosis screening program.

Background: Risser staging is one of several criteria used in scoliosis screening programs. This study aimed to evaluate the reliability of a radiologist's Risser interpretations from a large metropolitan scoliosis-screening program when compared to interpretations of 2 pediatric orthopaedic surgeons and 2 orthopaedic residents.

Methods: During the 2008 to 2009 school year, 275 students were reviewed as part of a metropolitan scoliosis-screening program. 100 of the radiographs were randomly chosen and de-identified for inclusion. Two attending orthopaedic surgeons and 2 orthopaedic residents independently interpreted the films on 3 occasions and assigned each a Risser stage. Inter- and intra-rater analyses using Kappa statistics were performed to determine the reliability of the Risser stage interpretations between the orthopaedic surgeons and the radiologist as well as the reliability of the interpretations among the individual surgeons.

Results: Inter-rater kappa values for the attending surgeons and the radiologist averaged 0.526. Inter-rater kappa values for the resident surgeons and the radiologist averaged 0.490 and 0.101. There was significant agreement between the attending surgeons on all 3 occasions (κ = 0.764, 0.809, 0.837). The intra-rater reliability among the attending surgeons (κ = 0.988, 0.957) and the resident surgeons (κ = 0.813, 0.495) showed statistical significance (P < 0.0001). Only half of the films had perfect agreement between the radiologist and the surgeons and 28% of the films were interpreted with a difference of 2 or more Risser stages. The radiologist did not interpret any of the films as a Risser 4 or 5 but 21% of the films were interpreted as a 4 or 5 by the orthopaedic surgeons.

Conclusions: The scoliosis-screening program utilizes a referral pathway based on the radiologist's Risser stage interpretation in conjunction with the Cobb angle. The radiologist and the orthopaedic surgeons demonstrated only moderate agreement in their interpretations of Risser stages, resulting in a possible 21% over-referral rate. This study questions the efficacy of using the Risser stage as part of a large metropolitan scoliosis screening program and warrants further investigation.