The prognostic importance of congruity of the hip joint in the reduction of residual dysplasia after successful conservative treatment of developmental luxation.

Background. Conservative treatment of developmental hip dislocation aims for stable reposition. However, after treatment a significant number of joints are not completely remodeled. The aim of our study was to determine which factors influence the direction of remodeling of the hip joint during growth. Material and methods. The remodeling of 78 dysplastic hips in 66 patients was analyzed, from the end of treatment to the end of the growth period. The remodeling of the hip joint was evaluated based on 5 radiographic parameters. The final assessment at the end of the growth period was performed using Severin's classification, and also our own classification. Results. The best outcome was obtained in hips which after conservative treatment had a normal neck-shaft angle, and the centering of the femoral neck improved quickly, reaching normal values before the age of 5 years. Slower remodeling (good final outcome) was observed in hips with increased neck-shaft angle which reached correct centering of the femoral neck before age 7. Those hip joints in which the centering of the femoral neck was incorrect at age 5-7 years had unsatisfactory outcomes. The condition of the acetabular roof in the first years after the end of conservative treatment did not affect outcome. Conclusion. The remodeling of the dysplastic hip after conservative treatment of developmental dislocation depends exclusively on the congruity of the joint. Early unsatisfactory remodeling of the acetabular roof resolves later, if the congruency of the joint is normal by age 5-7, depending on the neck-shaft angle.