Avascular necrosis predictive factors after closed reduction in patients with developmental dysplasia of the hip

Background: Developmental dysplasia of the hip (DDH) is a common pediatric orthopedic condition. Closed reduction (CR) is the conservative treatment approach with high success rates for DDH. However, avascular necrosis (AVN) is a severe potential complication after this procedure. This study retrospectively assessed the potential risk factors for AVN occurrence after CR and Spica cast immobilization. Materials and Methods: In a retrospective observational study, 71 patients (89 hips) with DDH aged 6-24 months old undergoing CR were enrolled. All patients were followed up for 3 years, and their demographic data, initial Tonnis grade, pre-reduction procedures, abduction angle in the Spica cast, and the AVN presence (based on Bucholz and Ogden classification [3rd-4th class]) were documented. Results: Of 71 patients (89 hips) with a mean age of 12.5 +/- 3.9 months, 13 patients (18 hips) developed AVN. The mean age of patients in the AVN and non-AVN groups was 14.3 +/- 4.9 and 12.2 +/- 3 months (P = 0.07); also, the mean abduction angle in patients with and without AVN was 51.86 +/- 3.66 and 58.46 +/- 3.91 (P < 0.001) in univariate analysis. The distribution of initial Tonnis grade, and previous conservative procedures, adductor tenotomies during the CR were comparable between the two groups (P > 0.05). We found age 12 months and 54 degrees in abduction angle as the best cutoff values for differentiating AVN patients from non-AVN and the risk of experiencing AVN for patients older than 12 months was odds ratio (OR) =4.22 (P = 0.06) and patients with abduction angle greater than 54 was OR = 34.88 (P < 0.001). Conclusion: In this study, older age at the time of intervention and larger abduction angle in the hip Spica cast were two predictors of experiencing AVN in DDH patients after undergoing CR treatment approach. Performing CR at a younger age and keeping the abduction angle lower than 54 degrees in the hip Spica cast could help to have the best possible prognosis. Level of Evidence: IV, retrospective, observational, cross-sectional study.