Prosthetic joint failure is mainly caused by infection, aseptic failure (AF), and mechanical problems. Infection detection has been improved with modified culture methods and molecular diagnostics. However, comparisons between modified and conventional microbiology methods are difficult due to variations in specimen sampling. In this prospective, multidisciplinary study of hip or knee prosthetic failures, we assessed the contributions of different specimen types, extended culture incubations, and 16S rRNA sequencing for diagnosing prosthetic joint infections (PJI). Project specimens included joint fluid (JF), bone biopsy specimens (BB), soft-tissue biopsy specimens (STB), and swabs (SW) from the prosthesis, collected in situ, and sonication fluid collected from prosthetic components (PC). Specimens were cultured for 6 (conventional) or 14 days, and 16S rRNA sequencing was performed at study completion. Of the 156 patients enrolled, 111 underwent 114 surgical revisions (cases) due to indications of either PJI (n = 43) or AF (n = 71). Conventional tissue biopsy cultures confirmed PJI in 28/43 (65%) cases and refuted AF in 3/71 (4%) cases; one case was not evaluable. Based on these results, minor diagnostic adjustments were made. Fourteen-day cultures of JF, STB, and PC specimens confirmed PJI in 39/42 (93%) cases, and 16S rRNA sequencing confirmed PJI in 33/42 (83%) cases. One PJI case was confirmed with 16S rRNA sequencing alone and five with cultures of project specimens alone. These findings indicated that JF, STB, and PC specimen cultures qualified as an optimal diagnostic set. The contribution of sequencing to diagnosis of PJI may depend on patient selection; this hypothesis requires further investigation.

BackgroundUnrecognized periprosthetic joint infections are a concern in revision surgery for aseptic failure (AF) after total hip (THA) or knee (TKA) arthroplasties. A gold diagnostic standard does not exist. The aim of the current study was to determine the prevalence of unrecognized periprosthetic joint infection (PJI) in a cohort of revision for AF, using an experimental diagnostic algorithm.MethodsThe surgeons’ suspicion of AF was based primarily on patient history and clinical evaluation. X-ray imaging was used to reveal mechanical problems. To rule out an infectious aetiology standard blood biochemical tests were ordered in most patients. Evaluation followed the existing practice in the institute. Cases were included if revision surgery was planned for suspected AF. Intraoperatively, five synovial tissue biopsies were obtained routinely. PJI was defined as ≥3 positive cultures with the same microorganism(s). Patients were followed for 1 year postoperatively. Protocol samples included joint fluid, additional synovial tissue biopsies, bone biopsy, swabs from the implant surface, and sonication of retrieved components. Routine and protocol samples were cultured with extended incubation (14 days) and preserved for batchwise 16S rRNA gene amplification. Patients were stratified based on culture results and a clinical status was obtained at study end.ResultsA total of 72 revisions were performed on 71 patients (35 THA and 37 TKA). We found five of 72 cases of unrecognized PJI. Extended culture and protocol samples accounted for two of these. One patient diagnosed with AF was treated for a PJI during follow-up. The remaining patients did not change status from AF during follow-up.ConclusionsWe found a low prevalence of unrecognized periprosthetic joint infections in patients with an AF diagnosis. The algorithm strengthens the surgeons’ preoperative diagnosis of a non-infective condition. Evaluation for a failing TKA or THA is complex. Distinguishing between AF and PJI pre-operatively was a clinical decision. Our data did not support additional testing in routine revision surgery for AF.

The predominant indications for revision surgery after total hip (THA) or knee arthroplasty (TKA) are an aseptic failure (AF) and prosthetic joint infection (PJI). Accurate diagnosis is crucial. Therefore, we evaluated prospectively a multidisciplinary diagnostic algorithm including multi-modal radionucleid imaging (RNI) and extended microbiological diagnostics. If the surgeon suspected PJI or AF, revision surgery was performed with multiple samples obtained in parallel for special culture procedures and later molecular analyses. Alternatively, if the underlying cause was not evident, RNI was scheduled comprising 99 Tc-HDP SPECT/CT, 111 In-labeled white blood cells combined with 99 Tc-nanocoll bone marrow SPECT/CT, and 18 F-FDG PET/CT. A multidisciplinary clinical team made a recommendation on the indication for a diagnostic procedure guided by RNI images or revision surgery. A total of 156 patients with 163 arthroplasties were included. Fifty-five patients underwent RNI. In all, 118 revision surgeries were performed in 112 patients: 71 on the indication of AF and 41 revision of PJI. Thirty-four patients were concluded with chronic pain, and revision surgery refrained. The effective median follow-up period was 13 months. A structured approach offered by the algorithm was useful for the clinician in the evaluation of patients with a failing TKA or THA. Surgical revision was possibly obviated in approximately 20% of patients where an explanation or cause of failure was not found. The algorithm served as an effective tool.

Background: The aim of this prospective study was to assess the diagnostic value of nuclear imaging with 18F-FDG PET/CT (FDG PET/CT), combined 111In-WBC/99mTc-Nanocoll, and 99mTc-HDP SPECT/CT (dual-isotope WBC/bone marrow scan) for patients with chronic problems related to knee or hip prostheses (TKA or THA) scheduled by a structured multidisciplinary algorithm. Materials and Methods: Fifty-five patients underwent imaging with 99mTc–HDP SPECT/CT (bone scan), dual-isotope WBC/bone marrow scan, and FDG PET/CT. The final diagnosis of prosthetic joint infection (PJI) and/or loosening was based on the intraoperative findings and microbiological culture results and the clinical follow-up. Results: The diagnostic performance of dual-isotope WBC/bone marrow SPECT/CT for PJI showed a sensitivity of 100% (CI 0.74–1.00), a specificity of 97% (CI 0.82–1.00), and an accuracy of 98% (CI 0.88–1.00); for PET/CT, the sensitivity, specificity, and accuracy were 100% (CI 0.74–1.00), 71% (CI 0.56–0.90), and 79% (CI 0.68–0.93), respectively. Conclusions: In a standardized prospectively scheduled patient group, the results showed highly specific performance of combined dual-isotope WBC/bone marrow SPECT/CT in confirming chronic PJI. FDG PET/CT has an appropriate accuracy, but the utility of its use in the clinical diagnostic algorithm of suspected PJI needs further evidence.