The presence of the ossific nucleus and its relation to avascular necrosis rates and the number of secondary procedures in late-presenting developmental dysplasia of the hip

Abstract

Late-presenting developmental dysplasia of the hip (DDH) has an incidence reported between 0.07 and 2:1000 live births. Avascular necrosis (AVN) of the femoral head secondary to treatment of DDH is a feared complication and may lead to adverse long-term sequelae. This study aims to investigate the relationship between the ossific nucleus (ON) presence and AVN in late-presenting DDH. This is a retrospective study of prospectively collected data over a 24-year period, at a single UK centre. Late-presenting DDH who were treated surgically with a closed or open reduction were included in the series. The presence of ON was monitored, and outcomes measured included AVN and whether delaying surgery affected the number of secondary procedures. Seventy-six patients with 79 hips (mean age at presentation 13.8 months) were included in the analysis. The mean age at presentation was 13.8 months. About 45.5% of hips with no ON present developed clinically significant AVN (Kalamchi and MacEwen grades 2-4, P = 0.12), compared to 20.6% of hips with the ON present. Delaying surgery did not affect AVN rates or the number of secondary procedures. Looking at long-term outcomes, 86.7% of hips had a Severin grade of I or II and 13.3% had a grade ≥III. Factors that affected long-term outcomes were absent ON (P = 0.04) and open reduction (P = 0.03). In the multiple logistic regression model, only open reduction could increase AVN rates (P value 0.027). The presence of ON at the time of surgery may have an impact on the rate and significance of AVN. Absence of the ON at the time of reduction negatively affects long-term outcomes in late-presenting DDH.