Low-grade infections in nonarthroplasty shoulder surgery

BACKGROUND: Recent studies have identified the diagnostic challenge of low-grade infections after shoulder arthroplasty surgery. Infections after nonarthroplasty procedures have not been reported. This study assessed patient-related risk factors, outcomes, and clinical presentation of low-grade infection after open and arthroscopic nonarthroplasty shoulder surgery.

METHODS: The cases of 35 patients presenting with suspected low-grade infection were reviewed. Biopsy specimens taken at revision surgery were cultured in the sterile environment of a class II laminar flow cabinet and incubated for a minimum of 14 days at a specialist orthopedic microbiology laboratory. Patient-related factors (age, occupation, injection), index surgery, and infection characteristics (onset of symptoms, duration to diagnosis, treatment) were analyzed.

RESULTS: Positive cultures were identified in 21 cases (60.0%), of which 15 were male patients (71%). Of all patients with low-grade infection, 47.6% were male patients between 16 and 35 years of age. Propionibacterium acnes and coagulase-negative staphylococcus were the most common organisms isolated (81.1% [n=17] and 23.8% [n=5], respectively). Of 14 negative culture cases, 9 were treated with early empirical antibiotics (64.3%); 7 patients reported symptomatic improvement (77.8%). Of 5 patients treated with late empirical antibiotics, 4 stated improvement. Patients presented with symptoms akin to resistant postoperative frozen shoulder (persistent pain and stiffness, unresponsive to usual treatments).

CONCLUSION: Young male patients are at greatest risk for low-grade infections after arthroscopic and open nonarthroplasty shoulder surgery. P. acnes was the most prevalent organism. Patients presented with classic postoperative frozen shoulder symptoms, resistant to usual treatments. Interestingly, 78.6% of patients with negative cultures responded positively to empirical treatment.