Many orthopaedists order cultures of tissue and synovial fluid samples during the reimplantation phase of two-stage exchange arthroplasties. Now, thanks to a retrospective study by Tan et al. in the August 3, 2016 JBJS, surgeons have some guidance on how to interpret the results from such cultures.
After controlling for other variables, the authors determined that a positive intraoperative culture at the time of reimplantation was independently associated with >2.5 times the risk of subsequent treatment failure. These findings prompted Tan et al. to conclude that “even single positive cultures…should be treated aggressively.” They report that at their institution (the Rothman Institute in Philadelphia), “any positive culture at the time of reimplantation is now considered important…and is treated with systemic antibiotics.”
Among the limitations of this study is its inability to accurately assess the impact of antibiotic treatment in patients with positive cultures. The authors also stress the need for further evaluation of rapid intraoperative diagnostic tools that have shown promise in determining infection eradication more quickly than cultures can.