Poor delineation of labrum and acetabular surface on arthrogram is a predictor of early failure of closed reduction in children aged six to 24 months with developmental dysplasia of the hip

Purpose The objective of this study was to explore the predictors for failed reduction in children with developmental dysplasia of the hip (DDH) managed by arthrogram, closed reduction (CR) and spica cast immobilization. Methods We retrospectively reviewed the clinical data of patients with DDH treated by CR and cast immobilization (2015-2020), including age, sex, affected side, presence/absence of an ossific nucleus, International Hip Dysplasia Institute classification, the delineation of labrum and acetabular surface on arthrogram, inverted labrum, acetabular index (AI), hip abduction angle and medial dye pool (MDP) distance. Predictors that potentially predicted failure of CR were evaluated by logistic regression analysis, simple t-test, Fisher's Exact Test and chi-square test. Results In total, 16 out of 187 hips failed to achieve initial CR (8.6%). Gender, age, preoperative AI and poor delineation of arthrogram were candidate predictors for failed CR in children aged six to 24 months with DDH; on the other hand, logistic regression analysis confirmed age and poor delineation of arthrogram significantly predicted failure of CR. Receive operating characteristic curve (ROC) showed MDP less than 6 mm and age higher than 14.5 months significantly increased the failure rate of CR in children aged six to 24 months with DDH. Conclusion Age and poor delineation of labrum and acetabular surface during arthrogram predicted failure of CR in children with DDH. In particular, age > 14.5 months and MDP distance >= 6 mm significantly increased the risk of CR failure. Level of evidence: III