Low Risk of Acute Iatrogenic Periprosthetic Joint Infection After Prosthetic Joint Aspiration

Synovial fluid analysis is an essential tool in diagnosing periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). However, concern exists that aspiration may introduce infection into a noninfected joint. Therefore, the purpose of this study was to evaluate the incidence of iatrogenic PJI following diagnostic knee aspiration done within 6 months of the primary TKA.Between 2017 and 2021, the senior surgeon performed over 4,000 primary TKAs and aspirated 155 knees in 137 patients for whom there was a suspicion for PJI within 6 months of their primary TKA. There were 22 knees diagnosed as infected from the initial aspiration and therefore were excluded from the study. The remaining 133 aspirates in 115 patients who were negative for infection were followed for 6 months for signs and symptoms of PJI to elucidate whether aspiration introduced infection into an initially noninfected joint.There were 70 of 133 knees (52.6%) aspirated between 0 and 6 weeks after index TKA, 40 of 133 (30.1%) between 6 weeks and 3 months, and 23 of 133 (17.3%) between 3 and 6 months. At final follow-up, none of the 133 initially noninfected knees exhibited evidence of subsequent iatrogenic PJI or had subsequent surgery for infection.While joint aspiration is a procedure with inherent risks, this study shows that the rate of iatrogenic PJI is extremely low (0%). Therefore, if infection is suspected, the surgeon should consider joint aspiration, even in the initial postoperative period, as the risk for introducing infection is far outweighed by the risk of missing an infection.