Osteonecrosis of the femoral head in sickle cell disease: prevalence, comorbidities, and surgical outcomes in California

Osteonecrosis of the femoral head (ONFH) is a prevalent complication of sickle cell disease (SCD) that has not been well described in population-based cohort studies. Using California's Office of Statewide Planning and Development discharge databases (1991-2013), we estimated the cumulative incidence of ONFH after accounting for the competing risk of death and used a multivariable Cox proportional hazards regression to identify factors associated with ONFH diagnosis. We also calculated rates of readmissions to the hospital or emergency department within 30 to 90 days of hip replacement surgery. Of the 6237 patients in our SCD cohort, 22% (n - 1356) developed ONFH at a median age of 27 years, and 23% (n 5 308) of the patients with ONFH underwent hip replacement surgery at a median age of 36 years. The cumulative incidence of ONFH to age 30 years was higher among SCD patients with more severe disease (24%; vs 8% in less severe) and those with antecedent acute chest syndrome (ACS) (18%; vs 8% without prior history of ACS). From 2003 to 2013, SCD patients with more severe disease (hazard ratio [HR], 2.77; 95% confidence interval [CI], 2.38-3.23) or with antecedent ACS (HR, 1.61; CI, 1.35-1.91) were more likely to develop ONFH. Twenty-seven percent of post-hip surgery patients were readmitted within 30 days, mostly for painful vaso-occlusive crises. ONFH is a common SCD complication that increases with age; ongoing studies into prevention and effective nonsurgical interventions for SCD-induced osteonecrosis must remain a high research priority.