Functional Outcomes in Children with Osteonecrosis Secondary to Treatment of Developmental Dysplasia of the Hip

BACKGROUND:Osteonecrosis of the femoral head is a major potential complication following the treatment of developmental dysplasia of the hip. It remains unclear if the radiographic changes associated with osteonecrosis are clinically relevant. METHODS:In the present cross-sectional study, we determined the relationship between morphological changes on radiographs (classified with use of the Bucholz-Ogden system) and health-related quality of life (assessed with the Health Utilities Index Mark 3 [HUI3]; maximum score, 1), physical function (assessed with the Activities Scale for Kids [ASK]; maximum score, 100), and hip function (assessed with the Childrenʼs Hospital Oakland Hip Evaluation Scale [CHOHES]; maximum score, 100). The study group included seventy-two children (mean age, 14 ± 2.5 years) with a diagnosis of osteonecrosis of the hip secondary to the treatment of developmental dysplasia of the hip. Patient assessments were standardized (intraclass correlation coefficient, ≥0.93). Radiographs were graded by three experts according to consensus. Analyses were adjusted for the number of previous surgical procedures on the hip and for the severity of residual hip dysplasia. RESULTS:The median ASK score was 97 (interquartile range, 93 to 100), the median CHOHES score was 86 (interquartile range, 77 to 96), and the median HUI3 score was 1 (interquartile range, 0.9 to 1). The ASK summary scores were nearly equal (median, >90) across all radiographic grades. Adjusted mean scores showed a downward shift with worse radiographic grades. The ASK scores (p = 0.004) and CHOHES scores (p = 0.006) differed across radiographic grades, with Bucholz-Ogden grade-I and II hips demonstrating significantly better scores than grade-III and IV hips. DISCUSSION:Osteonecrosis secondary to the treatment of developmental dysplasia of the hip is a relatively benign condition in children and teenagers. While it was associated with limited hip function, it was not associated with physical disability. However, we speculate that this function will decline with increasing age. With regard to clinical outcome, Bucholz-Ogden grade-I hips are similar to grade-II hips and grade-III hips are similar to grade-IV hips. LEVEL OF EVIDENCE:Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.