Diagnostic algorithm in septic total knee arthroplasty failure - What is evidence-based?

Prosthetic joint infection (PJI) is among the most common differential diagnoses of total knee arthroplasty failure. It is a challenging complication, not least because of the difficulty of establishing the correct diagnosis. The fact that no single diagnostic parameter or test has been identified that can accurately rule in or out PJI has led to an evolution of similar but competing definitions of PJI on the grounds of an array of criteria. This development has had very positive effects on the scientific evaluation of various methods of PJI diagnostics and treatment because of an increased comparability. However, it can be challenging to stay abreast of the evidence these definitions are based on. Also, the definitions alone do not necessarily entail an algorithm to aid in evaluating the right criteria in a sound order to be able to use the definitions as a sensible tool. The aim of this overview is to state the most recent evidence on the diagnostic parameters included in the most established PJI definitions and to exhibit and compare the few algorithmic approaches published. Clinical symptoms of PJI are very rarely reported on in the literature, hence the evidence on their diagnostic value is poor. The only symptom that is part of the established PJI definitions is the presence of a fistula. Concerning serological markers, CRP and ESR are still the common denominator in the literature, most recently accompanied by D-Dimer as a potentially suitable marker that has been included in the most recent update of the International Consensus Meeting (ICM) criteria. Imaging plays a minor role in the diagnostic cascade because of inconsistent evidence, and no role whatsoever in the established definitions. The most important preoperative diagnostic measure is arthrocentesis and cultural and cytological analysis of the synovial fluid. The much acclaimed α-Defensin test has so far not been included in the established criteria due to inconsistent reports on its diagnostic accuracy, it is, however, in wide use and considered an optional diagnostic tool for inconclusive cases. The most diagnostic accuracy lies in the cultural and histological analysis of periprosthetic tissue biopsies, whether they are gathered in a small procedure or during arthroplasty revision. Published algorithmic approaches to PJI diagnosis are much rarer than the well-established definitions by various associations. With their PJI definition, the American Academy of Orthopedic Surgeons (AAOS) published a consensus based flowchart for PJI diagnosis. Another algorithm was proposed as part of the endeavor of the MSIS and the first consensus meeting, also based on a consensus among experts. There have been two more recent publications of flowcharts based on the current evidence, one introduced at our institution in 2013, one established in 2020 by the German Society for Arthroplasty (AE).