Comparing Standard Versus Extended Culture Duration in Acute Hip and Knee Periprosthetic Joint Infection.

Introduction: Periprosthetic joint infection (PJI) is a devastating complication of hip and knee arthroplasties. Surgical cultures are essential for the diagnosis and treatment of PJI. Yet, the ideal culture duration remains unclear. This study compares culture yield, organism profile, and treatment success between standard (5 days) and extended (14 days) cultures in acute hip and knee PJI. Methods: A retrospective review of medical records was completed between 2006 and 2015. All patients with an acute PJI meeting the modified International Consensus Meeting on PJI criteria of a primary hip or knee arthroplasty were included. All patients underwent irrigation and debridement with exchange of modular bearing surfaces for an acute postoperative or acute hematogenous infection. A standard growth cohort (before February 2012) was compared with an extended growth cohort (after February 2012) to determine if differences existed in culture yield and treatment success using the Delphi consensus criteria. Results: One hundred eighty-nine patients were analyzed, including 102 (54.0%) standard duration and 87 (46.0%) extended duration cohorts. Patient cohorts were closely matched, except more hip PJIs than knee PJIs were included in the standard cohort (69.6% versus 49.4%; P = 0.005). No differences between standard and extended cohorts were observed with regard to overall culture yield, monomicrobial growth, or polymicrobial growth. Propionibacterium acnes was identified more often in the extended cohort (5 versus 0 patients; P = 0.019). However, four of these patients had only one positive P acnes culture and grew additional organisms. Finally, no difference in treatment success between the standard and extended cohorts at the final follow-up was found (53% versus 52%; P = 0.282). Conclusion: Extended culture duration in acute hip and knee PJIs did not change the rate of culture-negative PJI, identify more patients with polymicrobial PJI, or improve the success of surgical treatment. The only difference was a higher incidence of P acnes growth, but contaminants or indolent chronic PJI cannot be excluded. Although extended culture growth may be indicated in acute shoulder arthroplasty PJI, its utility in hip or knee arthroplasty may be limited. Higher-level studies will be needed to address this in the future.