Prevalence rates and an evaluation of reported risk factors: DISCUSSION

30 Dec
2011

DISCUSSION

This investigation evaluated the detection rate of osteonecrosis in a large series of consecutively evaluated patients with inflammatory bowel disease, specifically Crohn’s dis­ease. Of the 877 patients seen by a single clinician over 20 years in a referral-based tertiary care university teaching hospital setting, osteonecrosis was detected in four patients for an overall rate of approximately 0.5%. Because all four patients were male, the actual rate for men in this study was about 1%. No case was detected in women. These results are similar to those of previous studies. In one study, seven of 204 consecutively evaluated patients from a similar tertiary care setting developed osteonecrosis; of these, how­ever, only two had Crohn’s disease and, as in the present re­port, both were male. There were also some differences. For example, it was not clear in that study whether patients with inflammatory bowel disease also had already defined osteonecrosis at the time of their initial referral, as in the pres­ent study for one patient (case 1). In addition, diagnosis was entirely dependent on the use of radiographs and, rarely, nu­clear scanning, which is quite different from the experience in the present study; in our hospital, MRI has been available from 1981 for the detection of early changes of osteonecrosis. In a later retrospective study of 55 patients treated with alternate-day prednisone (average dose prednisone 25 mg every other morning) for a mean duration of 6.6 years, no ob­served instance of osteonecrosis was recorded. In that study, men predominated (37 patients [67.3%]), and 24 patients (43.6%) also had a prior intestinal resection. Thus, the present study, based on a series of consecutively evaluated patients in a tertiary care referral setting, confirms that this debilitating extraintestinal osseous complication of osteone- crosis is extremely rare in patients with Crohn’s disease.

The cause of osteonecrosis in Crohn’s disease is not known. Corticosteroids have been implicated in the past be­cause of a relationship apparently established for some other clinical disorders, including renal transplant recipients and systemic lupus erythematosis patients. A firm causal relationship has not been established for most disorders, including Crohn’s disease. Case reports detailing this specific complication in Crohn’s disease have failed to demonstrate a consistent association. Indeed, if anything, the relationship detailed in these anecdotal experiences has been quite contradictory. No definitive dose-response relationship has been described in Crohn’s disease, similar to recent prospective observations in patients with either in­flammatory arthritis or asthma treated with corticosteroids. Moreover, no consistent temporal relationship for the development of osteonecrosis has been described in patients with Crohn’s disease. Finally, no definite biological ex­planation has been provided to explain the role, if any, of corticosteroids in those very rare patients with osteonecrosis and Crohn’s disease. Similar considerations related to parenteral nutrition, or the combined use of corticosteroids and parenteral nutrition, have failed to define any evidence for a cause-effect relationship. In the present experience, two pa­tients who were treated with corticosteroids and parenteral nutrition developed osteonecrosis. However, in this same experience, two patients with Crohn’s disease who were not treated with corticosteroids or parenteral nutrition also de­veloped osteonecrosis. Finally, in this study, analyses of the frequency of use of corticosteroids, parenteral nutrition or both modalities, as well as the requirement for small intesti­nal resection, provided no evidence for their potential role in predisposing patients to osteonecrosis.
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CONCLUSIONS

In this series of 877 consecutively evaluated patients with Crohn’s disease, osteonecrosis was rarely encountered. De­spite the frequent requirement in this patient population for corticosteroid therapy, parenteral nutrition or both, identi­cal numbers of patients developed osteonecrosis.

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