Hip Abduction Angle and the Risk of Avascular Necrosis (AVN) After Closed Reduction (CR) in Developmental Dysplasia of the Hip (DDH)

Objectives Developmental dysplasia of the hip (DDH) is a prevalent pediatric orthopedic condition with a prevalence of 5–13 per 1000 live births worldwide. Early detection and management are paramount to mitigate long-term complications such as osteoarthritis and avascular necrosis of the hip (AVN). While various interventions exist, closed reduction (CR) and spica casting play pivotal roles in restoring normal hip anatomy. Given that AVN is a significant concern after CR, we aimed to investigate the correlation between the hip abduction angle in the spica and the risk of AVN. Methods This retrospective cohort study was conducted at Jordan University Hospital from 2016–2022. A total of 74 patients, aged up to 20 months, underwent CR, which was followed by CT scans with a minimum 12-month follow-up. CT scans were used for calculating the hip abduction angle, and X-rays were used for determining the Salter classification of AVN. Results The mean age at the time of CR was 7.29 ± 2.71 months. Fifty-one percent of the patients had bilateral DDH, and 7.6% had a positive personal or family history of DDH. The mean right and left abduction angles were 60.37° ± 8.03° and 59.53° ± 7.12°, respectively. The mean right and left International Hip Dysplasia Institute (IHDI) scores were 3.13 ± 0.7 and 3.38 ± 0.67, respectively. The mean right and left Salter AVN indices were 0.48 ± 1.13 and 0.55 ± 1.29, respectively. There were statistically significant relationships between right and left Salter (r = 0.793, p < 0.001), between right and left abduction angles (r = 0.335, p = 0.043), between right and left IHDI grades (r = 0.336, p = 0.039), between left IHDI grades and left Salter (r = 0.261, p = 0.047), and between left Salter and age (r = 0.264, p = 0.047). Neither the right nor the left abduction angle was associated with increased right or left Salter AVN grade, as indicated by the p values. Conclusions If a patient develops AVN on one side, the other side is also likely to be affected; however, the degree of abduction in CR does not correlate with the AVN rate. There was a correlation between the degree of abduction and the degree of subluxation/dislocation. Additionally, age at reduction is correlated with the risk of AVN.