Prevalence and Risk of Avascular Osteonecrosis in Inflammatory Bowel Disease

Abstract

Purpose: Avascular necrosis (AVN) of bone is a dreaded complication of prolonged steroid use. Case series in patients with inflammatory bowel disease (IBD) have reported an association between steroids and AVN of the hip/neck of femur and other sites. However, the prevalence of AVN has not been studied in depth in a large IBD population. Given that IBD patients often develop steroid-dependent disease, we sought to investigate the prevalence of AVN in IBD and to determine whether risk is related to length of steroid exposure. Methods: Using a large administrative health claims database, we conducted a retrospective cohort analysis to determine the prevalence AVN in IBD and identify factors associated with AVN occurrence. ICD-9 codes were used to identify subjects with IBD and diagnosis of AVN. We excluded subjects who also had diagnoses of lupus and other disorders for which steroids are used frequently. Treatment with steroids was documented and categorized into four exposure groups based on duration of use. All subjects were followed forward in time until the occurrence of AVN, end of capture period (Dec 2006) or end of enrollment. The prevalence of AVN in IBD was compared to that in a non-IBD population (1:5 ratio). Logistic regression was used to calculate independent risk (expressed as odds ratio [OR]) for AVN stratified by steroid exposure. Results: 53,434 IBD subjects were included and mean follow-up time was 2.4 years. The overall prevalence of AVN was 0.3% in IBD and 0.2% in non-IBD subjects. The rates were similar for Crohn's disease (CD) and ulcerative colitis (UC) but the steroid exposure overall was greater in CD. The risk of AVN with any steroid exposure compared to none was greater in CD (OR=2.1, P=0.0019) than in UC (OR=1.1, P=0.74). In a multivariate analysis, risk of AVN increased with longer steroid exposure, after adjustment for age and gender (Table). Conclusion: Among IBD patients, risk of AVN increases significantly with greater duration of steroid use. The prevalence is higher in CD than in UC but this difference may be due to lower steroid exposure in UC. There does not appear to be an increased risk for AVN due to IBD alone.Table