Reliability of acetabular index measurement in developmental dysplasia of the hip screening by orthopaedic trainees: a comparative study

Background: Radiographic measurements are used for screening of developmental dysplasia of the hip (DDH) in children. The ability to detect acetabular dysplasia requires validated radiographic outcome measures. The acetabular index (AI) measurement has been shown to be a reliable measure worldwide. This study aims to test the reliability of the AI measurement in a DDH screening population by orthopaedic junior and senior residents. Methods: The review examined 470 radiographs taken during 4 yr (2016-2019) in a university hospital. AI measurement was performed by two surgeons, four senior residents, and four junior residents at three different times. The intraobserver and interobserver reliability for each group was assessed. Results: The intraobserver reliability intraclass correlation coefficient (ICC) for the AI measurement performed by seniors was excellent at 0.98 (confidence interval [CI] 0.98 to 0.99) for the right side and 0.99 (CI 0.98 to 0.99) for left side. Indistinguishably, the ICC for AI measurement performed by orthopaedic juniors for right and left side was excellent at 0.96 (CI 0.95 to 0.97) and 0.95 (CI 0.95 to 0.96), respectively. The overall ICCs for interobserver reliability for the AI measurement between professors, seniors, and juniors for right and left side was between good and excellent at 0.89 (CI 0.87 to 0.90) and 0.89 (CI 0.87 to 0.91), respectively. Conclusions: Orthopaedic juniors are less reliable in terms of intraobserver and interobserver variability in detecting DDH in screening program in comparison with seniors using AI measurement in a pediatric orthopaedic clinic. Level of Evidence: Level III.