LAUSR

Background: The aim of this paper was to determine the prognostic potential of the ossific nucleus center edge angle (ONCEA) in patients below 5 years of age treated for developmental dysplasia of the hip (DDH) to predict final outcome and the need for a secondary procedure. Methods: The interobserver and intraobserver reliability was calculated using the intraclass correlation coefficient for measurement of the ONCEA. The ONCEA was divided a priori into 3 groups: group A≥10 degrees, group B −9 to 9 degrees, and group C ⩽−10 degrees. Final outcome was measured using the McKay score and Severin classification. The presence of osteonecrosis was recorded at final follow-up. Results: One hundred one patients with 133 dislocated hips underwent closed or open reduction for DDH. Mean age at presentation was 19 months with a mean age at final follow-up of 12.4 years. A significant difference was shown in a comparison of the 3 ONCEA groups using the McKay score, Severin classification, and need for a secondary procedure. Eighty seven of the 101 patients underwent ONCEA reliability measurements. The ONCEA was shown to have a mean intrarater reliability of 0.89, and a mean interrater reliability of 0.77. Conclusions: The ONCEA is a reliable measurement in predicting medium-term outcome of the hip post reduction in children under the age of 5 years with DDH and might be useful as a predictor for a secondary procedure before the age of 5 years. Level of Evidence: Level III—prognostic case control study. Clinical Relevance: This case control study shows the importance of measuring the ONCEA within 6 months of removing the final cast after reduction of a dislocated hip and its implications for further management and outcome.