Abstract
Introduction: Infection is a serious complication of joint arthroplasty. Detection of low-grade prosthetic infection can be difficult, with major implications on the subsequent treatment, cost and patient morbidity. We evaluated the effectiveness of Polymerase Chain Reaction (PCR) in detecting infection in patients undergoing arthroplasty revision surgery.
Methods: Ninety-one consecutive patients (92 joints) undergoing revision THA or TKA were assessed prospectively. Preoperative assessment included clinical examination, blood tests and plain radiographs. At revision, tissue samples were sent for microbiology and histology. Cultures, using blood culture bottles, and PCR were performed on the synovial fluid. Diagnosis of infection relied on the surgeon’s opinion encompassing the clinical presentation, the results of various investigations and the intraoperative findings. Infected arthroplasties underwent a 2-stage revision. Post-operatively patients were followed up at regular intervals for a minimum of 2 years.
Results: Twelve (13%) joints were infected. Histology was positive for infection in 11 cases, tissue cultures were positive in 12 and PCR was positive in 32 cases. Intraoperative tissue cultures had sensitivity 0.75, specificity 0.96, positive predictive value 0.75 and negative predictive value 0.96; histology had sensitivity 0.92, specificity 1, positive predictive value 1 and negative predictive value 0.99 and PCR had a sensitivity 0.92, specificity 0.74, positive predictive value 0.34 and negative predictive value 0.98. At 2 years no patient showed evidence of infection.
Discussion: PCR is a sensitive method of diagnosing prosthetic infection but has poor specificity. False positive results may be due to contamination in theatre or in the laboratory. Positive results in apparently non-infected cases could be due to the detection of low virulence organisms, a small number of bacteria or a strong host immune response. Bacterial fragments and non-culturable forms of bacteria may also be responsible.
Conclusion: PCR was not helpful as a screening test for prosthetic infection. Cultures and histology combined with the surgeon’s clinical judgment remain the gold standard.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
