Clinical characteristics and mid-to-long-term hip joint function in children with non-traumatic osteonecrosis of the femoral head: a comparative study of steroid-related, sickle cell disease, and idiopathic etiologies

Background Non-traumatic osteonecrosis of the femoral head (ONFH) in children is a heterogeneous condition with variable etiologies and prognoses. Few studies have compared mid-to-long-term functional outcomes across etiologic categories in the pediatric population. This study compared clinical characteristics, treatment patterns, and 5-year hip joint function among pediatric patients with steroid-related, sickle cell disease (SCD)-associated, and idiopathic ONFH. Methods This retrospective cohort study included 372 pediatric patients (127 steroid-related, 89 SCD-associated, 156 idiopathic) diagnosed with ONFH between 2012 and 2020; the idiopathic group comprised children who fulfilled diagnostic criteria for Legg-Calve-Perthes disease (LCPD), and the terms idiopathic ONFH and LCPD are used synonymously throughout. The patient was the unit of analysis. Primary outcomes were the Harris Hip Score (HHS) at 5-year follow-up (assessed for native, non-replaced hips) and conversion to total hip arthroplasty (THA). Kaplan-Meier survival analysis with the log-rank test, competing-risk cumulative incidence analysis accounting for death, a linear mixed-effects model for HHS trajectories, and univariate and multivariable logistic regression were performed. Results The SCD group had the worst outcomes, with a THA conversion rate of 53.9% (48/89) and a mean 5-year HHS of 65.6 +/- 19.6, compared with 33.9% (43/127) and 78.4 +/- 14.8 for the steroid-related group, and 9.6% (15/156) and 89.8 +/- 9.2 for the idiopathic (LCPD) group (all p < 0.001). In the multivariable model, SCD etiology (adjusted OR = 5.86, 95% CI: 2.60-13.24), Ficat stage III-IV (adjusted OR = 3.74, 95% CI: 1.93-7.25), and bilateral involvement (adjusted OR = 1.97, 95% CI: 1.02-3.80) were independently associated with THA conversion. Conclusions Etiology significantly influences the clinical course and prognosis of pediatric ONFH. SCD-associated ONFH carries the worst prognosis, whereas idiopathic (LCPD) cases show the most favorable outcomes. These findings support etiology-specific management protocols.