THE CLINICAL IMPACT OF LOW-GRADE INFECTION IN THE SETTING OF REVISION SHOULDER INSTABILITY SURGERY: A PROSPECTIVE MULTICENTRE CONSECUTIVE COHORT STUDY

Recurrent shoulder instability after primary surgical stabilization is the main reason for revision surgery. The aim of this study was to document the positive culture rate in shoulder instability revision cases and describe its clinical impact. All consecutive patients with primary shoulder instability surgery needing revision surgery were included in our prospective cohort. Minimum follow-up after the revision surgery was 1 year. Data collected included demographics, infection evaluation (clinical evaluation and proper culture sampling), functional assessment with WOSI (Western Ontario Shoulder Instability Index) and Quick DASH (Disabilities of Arm, Shoulder and Hand), osteoarthritis at last follow-up. Thirty-seven patients met the inclusion criteria with a mean follow-up after revision surgery of 1.4 years. One patient was lost to follow up. Among all revisions, 22 had cultures taken. Ten patients had confirmed microbiological infection, all with C. acnes. Alcohol consumption was found to be a statistical risk of infection in patients with revision surgery (70% versus 22%, p=0.017). Patients with infection at revision surgery had worse clinical outcomes at the last follow-up compared to revision surgery with no infection, even if it did not reach statistical significance (WOSI= 1125 (± 303) 95% CI: [844.83; 1405.31] versus 855 (± 562) 95% CI: [591.53; 1117.81] respectively, p=0.128); (Quick DASH=32.8 (± 8.9) 95% CI: [24.49; 41.1] versus 25.3 (± 18.7) 95% CI: [16.59; 34.07], p=0.323). Osteoarthritis was significantly different at the last follow-up; 100% of infected patients had osteoarthritis whereas 55% of non-infected patients had osteoarthritis (p=0.018). At the last follow-up, there was no case of persistent clinical infection or dislocation recurrence. C. acnes infection was identified in 45% of recurrent anterior shoulder instability (RASI) revision surgeries when cultures were taken. Alcohol consumption was the only risk factor for infection found in our study. Positive cultures after RASI reoperation seem to be related to osteoarthritis onset. Patients can expect significant improvement in stability and function after revision, even in the presence of infection and osteoarthritis. To understand stabilization surgery failure, C. acnes cannot be treated lightly and should always be considered in revision surgery. We therefore recommend systematic tissue sampling and culture to rule out or treat infection in patients undergoing revision shoulder instability surgery.