Hip Abduction in Spica Casting and Osteonecrosis After Closed Reduction for Developmental Dysplasia of the Hip

Abstract

Purpose  Hip position after closed reduction must balance stability against vascular compromise, but the abduction angle associated with osteonecrosis remains uncertain.
Methods  PubMed/MEDLINE and PubMed Central were searched from inception through 13 September 2026. Eligible studies included children treated for idiopathic developmental dysplasia or dislocation of the hip and reported a measured or categorized post-reduction abduction angle with osteonecrosis or reduction-stability outcomes. Two-stage screening, cohort-overlap assessment, and structured risk-of-bias appraisal were performed. Because exposure definitions, age strata, outcome classifications, and effect measures were incompatible, quantitative pooling was not undertaken.
Results  Eight clinically relevant cohorts were retained for the principal synthesis. A closed-reduction cohort of 82 hips found no overall linear association, but among children aged 6 months or younger osteonecrosis occurred in 9 of 15 hips cast at 50 degrees or more versus 0 of 8 below 50 degrees. A separate 89-hip cohort reported a strong association above 54 degrees, whereas a 59-hip late-detected cohort found no association across a substantially higher mean angle of 70.2 degrees. A protocol-era comparison of 86 children found similar osteonecrosis rates at approximately 60 and 45 degrees (19% versus 16%). Recent mixed-reduction cohorts provided conflicting adjusted findings. Redislocation was infrequently and inconsistently reported.
Conclusion  Available observational evidence does not establish a universal safe abduction threshold. The association may be modified by age, reduction difficulty, perfusion, and treatment era. Angles at or above 50 to 60 degrees warrant particular caution in younger infants, but cast position should be individualized to achieve stable concentric reduction without forceful abduction.