Laboratory Diagnosis of Periprosthetic Joint Infections

Total knee arthroplasty (TKA) is one of the most common elective surgical procedures in the world. Periprosthetic joint infection (PJI) is a rare but devastating complication after TKA, with an estimated risk of 0.5–2% following primary procedures. Despite the low incidence of this complication, PJI is the most common indication for revision in the Medicare population and the main cause of failure in modern total joint arthroplasty (TJA). With over a million joint replacement procedures performed each year in the USA, the overall burden of PJI will also invariably increase. This rare but devastating complication is not only associated with a significantly increased risk of mortality and decreased quality of life, but also poses a substantial economic burden to the healthcare system as costs can be up to four times higher than that of uninfected cases. The lack of a “gold standard” diagnostic test makes the diagnosis of PJI extremely challenging. Recently, several evidence-based guidelines have been introduced to standardize the approach to a patient with a suspected PJI. The general approach to diagnosing a PJI is twofold. First, the presence or absence of a joint infection must be confirmed; second, the infecting microorganism(s) must be isolated and its antimicrobial susceptibility elucidated. In addition to clinical findings from history and physical examination, the diagnosis of PJI often relies on laboratory results and in some cases, radiographic evaluation. In particular, isolating the causative microorganism from cultures of fluid or tissue within the joint remains the cornerstone for diagnosis and targeted antibiotic therapy, which has been shown to increase the chances of treatment success and influence the prognosis of patients with this condition.