Evaluation of the use of sonication of retrieved implants for the diagnosis of prosthetic joint infection in a routine setting.

In order to evaluate the usefulness of sonication of retrieved implants for the diagnosis of prosthetic joint infection (PJI) in a large group of patients in a routine setting, we designed a 3-year retrospective study. Patients were classified into two groups: those meeting the clinical criteria of PJI and those that did not (control group). Two hundred patients and 276 samples were included. The types of infection were early (n = 44), delayed (n = 53), positive intraoperative cultures (n = 13) and late-acute (n = 8). The culture sensitivities of sonicate fluid, periprosthetic tissue, synovial fluid and combination of periprosthetic tissue and/or synovial fluid were 69.5, 52.8, 54.8 and 60.2%, respectively. The specificities were 97.6, 90.3, 93.0 and 89.9%, respectively. Sonicate fluid culture of implants was more sensitive than peri-implant tissue, synovial fluid and combination of periprosthetic tissue and/or synovial fluid for all infection types, though it was especially useful in delayed infection: 91.3% vs. 60.0% (p = 0.0015), 63.2% (p = 0.0005) and 66.7% (p = 0.0001), respectively. When sonicate fluid culture of implants was performed in addition to conventional cultures, the sensitivity increased significantly in total (from 60.2 to 77.1%) and delayed PJI (from 45.1 to 71.7%). On the other hand, for early PJI, sonicate fluid culture of prosthesis was not superior to conventional diagnostic methods.