Background Despite considerable changes in the treatment of of late-detected congenital or developmental hip dislocation (DDH) during the last 50 years, it is unclear whether and to what degree these changes have led to better long-term outcome for the patients. Questions/purposes The aims of this study were to see whether decreasing use of skin traction and instead a more aggressive approach to open reduction resulted in (1) reduced use of secondary procedures; (2) improved radiographic appearance of the hips at long-term followup; and (3) changes in the proportion of patients developing avascular necrosis. Methods Two groups of patients were compared retrospectively. Inclusion criteria were patient age older than 3 months and younger than 5 years at the initiation of treatment, no associated anomaly, no previous treatment in other hospitals, and available radiographs from the time of diagnosis to skeletal maturity.