Should positive cultures at the time of primary total shoulder arthroplasty be treated?
Wyatt D Vander Voort, MD1, Edward Wu, MD1, George Chavez, BS1 and Robert M Szabo, MD, MPH2, (1)UC Davis Medical Center, Sacramento, CA, (2)UC Davis Health, Sacramento, CA
Cutibacterium acnes is a pathogen commonly affecting shoulder reconstruction; however, there is little understanding of the clinical impact of positive cultures at the time of index surgery and whether they should be interpreted as a dermal colonization or a prosthetic joint infection (PJI). We hypothesize that there is no difference in clinical outcomes or reoperation rates between patients with positive cultures at the time of primary TSA treated with antibiotic therapy compared to those with negative cultures.
We performed a retrospective chart review of 90 consecutive anatomic or reverse shoulder arthroplasties performed between January 2015 to December 2019 by the senior author. In each case, a minimum of 3 aerobic and anaerobic tissue culture samples were collected. Patients with positive cultures were referred to infectious disease. Those with positive cultures in only one sample or those with exceedingly low colony counts, as determined by infectious disease, were presumed to be due to contamination and thus not treated with antibiotics. Primary outcome was the development of a clinically significant PJI necessitating revision surgery. Chi-square analysis was used to compare groups.
28 (31%) patients had positive cultures at the time of index surgery, with 23 (82%) of the positive cultures growing C. acnes. 8 (29%) of patients underwent long term antibiotic therapy as directed by an infectious disease physician. There was no significant difference in history of diabetes, autoimmune disorders, shoulder injections, or steroid use between patients with positive versus negative cultures. 46% of patients with positive cultures had a history of prior shoulder surgery compared to 27% of patients in the culture negative group, which approached statistical significance (p = .08). Within the culture positive group, no patients had clinical or radiographic evidence of infection or required revision surgery for PJI at last follow-up. No patients in the culture negative group developed an infection, although 3 required revision for instability.
Positive cultures at the time of primary shoulder arthroplasty are common, although only a fraction are deemed to be clinically significant by the infectious disease service to warrant treatment. A history of shoulder surgery may predispose patients to higher culture positivity rates at the time of primary shoulder arthroplasty. In our cohort, there were no patients in the culture positive group developed evidence of prosthetic joint infection, suggesting that routine cultures or antibiotic therapy may be unnecessary at the time of index surgery.
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