Rilonacept (Arcalyst ®) in the Treatment of Subacromial Bursitis

Background: Subacromial bursitis is an inflammatory condition which is typically triggered by altered rotator cuff mechanics. One of the mainstays of therapy is corticosteroid injection. Given the inflammatory nature of subacromial bursitis coupled with prominence of interleukin-1 (IL-1) beta on histopathologic assessment of resected subacromial bursa, targeted anti-IL-1 therapy would be an attractive alternative to corticosteroid injection. Hypothesis: One intra-bursal injection of the IL-1 trap rilonacept (Arcalyst ®), currently FDA approved for the treatment of cryopyrin associated periodic syndrome (CAPS), is non-inferior to intra-bursal corticosteroid injection at 4 weeks post-procedure. Methods: This study is a prospective trial lasting a total of 4 weeks. Patients with typical symptoms and signs of subacromial bursitis are randomized to either corticosteroid injection prepared in the usual fashion in clinic vs. injection of rilonacept. Prior to injection of either medication patients will complete a QuickDASH Questionnaire and provide a verbal pain score from 0 to 10. The Quick DASH Questionnaire and verbal pain score are then completed within 2 duty days of injection, 2 weeks after injection, and 4 weeks after injection by phone. Primary Outcome: Primary outcome is improvement in QuickDASH. Secondary outcomes are improvement in the verbal pain score and monitoring for infection or other complications from rilonacept administration.