Preoperative and intraoperative infection workup in apparently aseptic revision shoulder arthroplasty.

The possibility of infection should be considered in every revision shoulder arthroplasty even in the absence of clinical symptoms and signs of infection because indolent infection is prevalent. Detection of infection in apparently aseptic failed arthroplasties poses a diagnostic challenge as the conventional principles and criteria used for hip and knee arthroplasty are not generally applicable. Propionibacterium acnes and Staphylococcus epidermidis are among the infectious organisms most commonly identified in such situations. Serum inflammatory markers are essential but are often unreliable as they have poor sensitivity in the shoulder. Preoperative shoulder joint aspiration culture is an important step but is subject to high false-negative rates. Lower cutoff values of synovial fluid analysis are used for detection of periprosthetic infection than for native joint infection as demonstrated in the knee literature. Intraoperatively, frozen section should be considered when a diagnosis of infection has not been established even in the presence of clinical suspicion. Gram stain is currently not recommended because of its low sensitivity and negative predictive value. Intraoperative culture is critical and should be performed whenever there is clinical suspicion of infection. Unexpected positive intraoperative cultures are not uncommon, and 6% to 25% of them appear to represent true infection as demonstrated with positive follow-up cultures or subsequent development of infection. In revision shoulder arthroplasty, determining the presence of infection can be difficult. A standardized approach is needed to determine the best course of treatment in this particular clinical setting.