Subacromial bursitis is caused by inflammation of the bursa that separates the superior surface of the supraspinatus tendon from the overlying coraco-acromial ligament and acromion. While multiple cytokines are implicated, interleukin-1 beta appears to play a prominent role. Rilonacept, an interleukin-1 trap, may be an alternative to corticosteroid injection for the management of this condition.

This single center, randomized, non-inferiority, unblinded study recruited 33 subjects over 9 months. Twenty subjects received 160mg intrabursal injection of rilonacept and 13 received a 6mL mixture of lidocaine, bupivacaine, and 80mg triamcinolone acetonide. QuickDASH, subject reported pain, and adverse events were recorded at time of injection, 2 days later, 2 weeks later, and 4 weeks later. Primary outcome was improvement in QuickDASH 4 weeks post-injection. Secondary outcomes were improvement in subject reported pain and occurrence of adverse events at 4 weeks.

Both study groups were equally matched for age, gender, ethnicity, and site of bursa injection. Both medications demonstrated a statistically significant improvement in QuickDASH 4 weeks post-injection, but triamcinolone acetonide injection offered greater improvement (P=0.004). Both medications demonstrated improvement in subject reported pain but between group comparison at 4 weeks showed that triamcinolone was superior (P=0.044). No statistically significant differences in adverse events were noted between groups, but subjects who received rilonacept experienced more episodes of diarrhea and headache.

While improvement in QuickDASH and pain was noted with a single intrabursal injection of rilonacept at 4 weeks, injection with triamcinolone acetonide was more efficacious.

This trial was registered with www.clinicaltrials.gov/ (NCT01830699).