source: American Society of Hematology

year: 2016

authors: Oyebimpe O Adesina, Ann M Brunson, Jason Gotlib, Theresa Keegan, Ted Wun

Introduction: Osteonecrosis of the femoral head (ONFH) is characterized by insidious onset of hip joint pain, limited range of motion and disability in sickle cell disease (SCD) patients. Prevalence of ONFH, rates of hip replacement surgery and post-operative course have not been previously described in population-based cohort studies. We retrospectively reviewed a large SCD patient cohort from California’s Office of Statewide Planning and Development (OSHPD) Patient Discharge Database (PDD), and report the risk factors and clinical outcomes for SCD patients with ONFH.

Methods: Patients were ascertained from the PDD from 1991 to 2013, through an iterative search algorithm using ICD-9 codes. In addition to descriptive statistics and univariate comparisons with the chi-square test, we used multivariable Cox proportional hazards models (with age as the time scale), to analyze factors associated with ONFH diagnosis, including sex, SCD severity and antecedent acute chest syndrome (ACS; data available from 2003-2013). Patients with more severe SCD were defined as those who averaged 3 of more hospitalizations per year. Antecedent ACS was considered as a time-dependent covariate to first ONFH diagnosis after 2003. We estimated the cumulative incidence of ONFH, accounting for the competing risk of death, by SCD severity and antecedent ACS diagnoses, with differences assessed by the Gray’s test for equality. We also determined rates of all re-admissions to the PDD and emergency department within 30-90 days after hip replacement surgery, including re-admissions for venous thromboembolism (VTE) and painful vasoocclusive crises (VOC). All data were analyzed using SAS 9.4 software, and results presented as hazard ratios (HR) and 95% confidence intervals (CI).

Conclusions: The overall prevalence of ONFH in this SCD cohort was 22%, and approximately 23% of the ONFH patients underwent hip arthroplasty (5% of the entire SCD cohort). Thus, ONFH is a common complication of SCD, which often requires surgical intervention. ONFH was independently associated with SCD severity and ACS, as has been previously suggested (Kato, Gladwin et al. 2007). Readmission within 30-60 days after hip surgery was common in this SCD cohort, and often due to painful VOC. Of the 144 readmissions within 90 days of discharge from hip replacement surgery, only 2 (~1%) were due to VTE, which is lower than reported in non-sickle cell patients undergoing hip replacement surgery. Our large, populations-based cohort study provides insight into the frequency and risk factors of ONFH in SCD patients, and also reveals that post-operative readmissions are common.

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