FDG PET imaging for diagnosing prosthetic joint infection: discussing the facts, rectifying the unsupported claims and call for evidence-based and scientific approach

Abstract

Dear Sir,As the number of primary total hip and knee arthroplastiesincreases due to the rapid aging of the world population, sowill the number of failed prosthetic joint reinsertions [1].Causes of such failures include aseptic loosening, infection,dislocation, and fracture of the prosthesis or the surroundingbone. Infection, although uncommon, is the most seriouscomplication related to this procedure, occurring in 0.8–1.9%oforiginalkneearthroplastiesand0.3–1.7%oforiginalhip arthroplasties. However, this incidence increases substan-tially (to at least 10 %) when the joint arthroplasty is reviseddue to various complications of this procedure [2–4]. Thedifferentiation between infection and aseptic loosening ischallenging and yet of critical importance for planning opti-mal treatment of failed arthroplasty. While management ofprostheticjointinfection(PJI)generallyrequiresbothsystem-ic antibiotic treatment for an extended period and exchangearthroplastyinoneormorestages,asepticlooseningisusuallymanaged with a single revision arthroplasty [1].Although a variety of scintigraphic techniques have beenemployed for diagnosing PJI during the past decades [5–8],no consensus opinion has been proposed about the optimaldiagnostic paradigm for this purpose. Some investigators(ardentproponents) havestatedthat combined invitro radio-labeled leukocyte/bone marrow scintigraphy (LS/BMS) be-cause of its high accuracy (90 %) should be regarded as theimaging modality of choice for diagnosing PJI [5], despiteits well-known disadvantages and deficiencies (the proce-dure is labor-intensive, time-consuming, costly, and carriessubstantial risks to the patient including contamination ofthe final product with lethal pathogens, potential for inter-patient misadministration, and above all substantial andhazardous levels of radiation exposure). However, thesecolleagues have misrepresented the facts about seriousissues that are associated with this test in optimal manage-ment of patients with suspected PJI [5].In recent years, a relatively large number of studies havebeen carried out testing the efficacy of FDG PET imaging,which appears to have overcome many of the deficienciesdescribed above [8–15]. FDG PET imaging has many practi-cal advantages over combined LS/BMS, including its routineavailability in advanced societies, the requirement for only asingle radiotracer injection, completion of the test within abrief period of time, outstanding safety record (lack of patho-gensin the final product based onexisting FDA records), andsubstantially lower radiation exposure and costs. Moreover,PET provides significantly superior spatial resolution andhigh quality/quantitative imaging data unachievable by LS/BMS. Unfortunately, a small number of papers have beenpublished over the past few years claiming that FDG PETimagingcannotaccuratelydifferentiatebetweeninfectionandasepticloosening,andisinferiortoandnotasuitablealternateto combined LS/BMS [5, 16–18]. Are these claims trulyjustified and/or are they based on critical scientific evidencegenerated by competent and experienced investigators?