Diagnostic accuracy of preoperative percutaneous synovial biopsy and aspirate compared with open biopsy for prosthetic shoulder infections.

Background: Shoulder arthroplasty revision is associated with a high prevalence of prosthetic infection, and diagnosis remains difficult. The primary aim of the study was to determine the diagnostic accuracy of percutaneous synovial biopsy (PSB) and joint aspiration compared with open culture results in detecting infection in revision shoulder arthroplasty. The second aim was to determine whether biopsy location within the shoulder was associated with culture status.

Methods: This was a multicenter prospective cohort study involving 4 sites and 69 patients undergoing revision shoulder arthroplasty. The cohort was 57% female with a mean age of 64 years. Preoperative fluoroscopic-guided PSBs and aspirations were carried out by a musculoskeletal radiologist before revision shoulder arthroplasty. The original prostheses consisted of hemiarthroplasties, total shoulder arthroplasties (TSAs), resurfacing TSA, reverse shoulder arthroplasties (RSAs), and antibiotic spacers. Six synovial tissue biopsies from separate regions in the shoulder were obtained both preoperatively and intraoperatively. The shoulder joint was aspirated, and synovial fluid collected, if available. Infection was considered positive in the setting of 2 or more matching positive cultures. The PSB cultures were considered "true positive" if the PSB cultures matched the open biopsy cultures.

Results: Nineteen percent had positive infection based on PSB, and 23% had confirmed culture-positive infections based on intraoperative biopsy. The diagnostic accuracy of PSB compared with open biopsy was as follows: sensitivity 0.37 (95% confidence interval [CI] 0.13-0.61), specificity 0.81 (95% CI 0.7-0.91), positive predictive value 0.37 (95% CI 0.13-0.61), negative predictive value 0.81 (95% CI 0.70-0.91), positive likelihood ratio 1.98, and negative likelihood ratio 0.77. Of the 71 patients from whom aspirates were collected, aspiration yielded synovial fluid in 33 patients. Preoperative aspiration detected no infections confirmed positive by open biopsy and correctly identified 81% of absent infections. The diagnostic accuracy of aspiration compared with open biopsy was as follows: sensitivity 0%, specificity 0.81 (95% CI 0.66-0.96), positive predictive value 0%, and negative predictive value 0.78 (95% CI 0.63-0.93). Biopsy location within the shoulder was not associated with infection status.

Discussion: Preoperative aspiration detected none of the infections proven positive via open biopsy. Although PSB was superior to synovial fluid aspirate, poor likelihood ratios suggest that PSB is not useful as an isolated test in the preoperative workup of the potentially infected patient. Biopsy location was not associated with culture status suggesting that the capsule is uniformly infected, and the location of tissue biopsies does not appear to matter.