Abstract
Introduction
Periprosthetic joint infection (PJI) is considered one of the most feared causes of implant failure, due to the difficulty in formulating a proper and timely diagnosis. In the diagnostic workup are often used test with a low specificity, such as the dosage of ESR and CRP, or sensitivity, such as cultures or the leukocyte count of the synovial fluid. Radiological investigations are expensive and unreliable to play a direct role in the diagnosis of PJI. The alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens and it is an ideal biomarker for the diagnosis of PJI. It is now possible to verify the presence of alpha-defensin in periprosthetic synovial fluid with an ELISA (Synovasure® PJI, Zimmer) that provides results in 10 minutes, with a sensitivity of 97% and a specificity of 96%, without being affected by systemic inflammatory diseases or by the assumption of antibiotics. The purpose of this study is to assess the applicability and reliability of Synovasure® PJI, correlating its results with microbiological analyzes, laboratory tests and imaging studies of the patient.
Materials and Methods
Patients recruited are those who have undergone a previous total hip or knee arthroplasty where there is suspicion of PJI. The test can be performed either during surgery or during the diagnostic iter, through the execution of an arthrocentesis. The synovial fluid is partly used for Synovasure® PJI and partly put in culture for microbiological analyzes. Once ready, culture results are compared with the results of the test to get a confirmation of its reliability or reference to identify the microorganism responsible for PJI. These data are then compared, with laboratory tests and radiological investigations performed by the patient.
Results
Up to now we have full results in 10 patients (11 implants). In four cases, the test showed the presence of alpha-defensin in the synovial fluid, while in seven cases the test result were negative. In case of negative test culture of synovial fluid showed no growth of microorganisms that could indicate the presence of false negatives. All patients with positive test have arthrocentesis positive for pathogenic microorganisms. We are waiting for culture results of two other patients (one with positive test and one with negative test). In the next few months will be tested other patients with suspicion of PJI.
Discussion
Timeliness and accuracy in the diagnosis are essential for the proper management of the patient with suspected PJI. Diagnostic tools currently available are often sensitive but not very specific or conversely, specific but insensitive. New synovial markers such as alpha-defensin and rapid ELISA tests for their dosage open new horizons in the diagnosis of periprosthetic infections.
Conclusions
Synovasure® PJI is a practical and reliable tool in the diagnosis of periprosthetic joint infections. Thanks to the quick response and the ease of execution the test can be used both during the diagnostic iter and during the revision surgery helping the orthopedic to apply the most appropriate measures to each case.
