Infections after shoulder arthroplasty are correlated with higher anesthetic risk score: a case-control study in Brazil

PURPOSES: Shoulder arthroplasty (SA) has been performed by many years for the treatment of several conditions, including osteoarthritis and proximal humeral fractures following trauma. Surgical site infection (SSI) following Shoulder arthroplasty remains a challenge, contributing to increased morbidity and costs. Identification of risk factors may help implementing adequate strategies to prevent infection. We aimed to identify pre- and intra-operative risk factors associated with deep infections after Shoulder arthroplasty. METHODS: An unmatched case-control study was conducted to describe the prevalence, clinical and microbiological findings, and to evaluate patient and surgical risk factors for prosthetic shoulder infection (PSI), among 158 patients who underwent SA due to any reason, at a tertiary public university institution. Risk factors for PSI was assessed by uni- and multivariate analyses using multiple logistic regression. RESULTS: 168 SA from 158 patients were analyzed, with an overall infection rate of 9.5% (16/168 cases). Subjects undergoing SA with American Society of Anesthesiologists (ASA) grade III or higher (odds ratio [OR] = 5.30, 95% confidence interval [CI] = 1.58–17.79, p < 0.013) and presenting local hematoma after surgery (odds ratio [OR] = 7.10, 95% confidence interval [CI] = 1.09–46.09, p = 0.04) had higher risk for PSI on univariate analysis. However, only ASA score grade III or higher remained significant on multivariate analysis (OR = 4.74, 95% CI = 1.33–16.92, p = 0.016). Gram-positive cocci and Gram-negative bacilli were equally isolated in 50% of cases; however, the most commonly detected bacterium was Pseudomonas aeruginosa (18.7%). CONCLUSION: This study provides evidence suggesting that patient-related known factors such as higher ASA score predisposes to shoulder arthroplasty-associated infection. Furthermore, unusual pathogens associated with PSI were identified.