Background: Differential diagnosis of prosthetic joint infection and aseptic loosening can be not easy. The American Academy of orthopaedic Surgeons has recently published guidelines to perform a correct diagnosis using clinical findings, inflammatory markers, and microbiological cultures. In uncertain cases radionuclide imaging, frozen section and histopathology can be useful.
Methods: Retrospective analysis of a cohort of patients with prosthetic joint infection examined with technetium-99-labeled-leukocyte, frozen section and histopathology.
Results: A cohort of 30 patients was evaluated in the period 2010-2012. Before surgery, technetium-99-labeledleukocyte
imaging was performed in 25 cases (in the remaining 5, infection was documented by the presence of a sinus tract). The nuclear scan was negative in 3 patients and positive in the other 22. Patients with negative scan were treated with one stage exchange. Patients with documented infection were treated with resection arthroplasty (2 cases) or two-stage exchange (25 cases). Frozen section examination, performed during removal arthroprosthesis, was negative in 4 cases (3 patients undergoing one stage exchange and one false negative) and positive in 26 cases. Histological findings were in agreement with frozen section. A failure for persistence of infection (culture
positive) was documented in 3/25 two stage exchange. Radionuclide scan was repeated before spacer removal in 20/25 two stage. It was negative in 16 (one false negative), positive in 4 cases (2 true positive in patients with persistence of infection, 2 false positive in patients with cultures negative). During prosthesis replacement frozen section and permanent histopathology was repeated with some discordant results for persistence of inflammation in patients with documented resolution of infection.
Conclusions: In our experience technetium-99-labeled-leukocyte imaging associated with intraoperative frozen section examination, have guided a correct management of patients with suspect prosthetic joint infections. In 2 stage exchange the sensibility seems better during first step (prosthesis removal) than during prosthesis replacement.