Diagnosis of prosthetic infection by intraoperative freezing biopsy

Clinical examinations and complementary tests, although highly sensitive and specific, do not always allow septic and aseptic prosthetic loosening to be safely differentiated. Prior experience suggests that the polymorphonuclear cell count in frozen intraoperative biopsy can improve diagnostic reliability. We report our experience with this technique in a series of 40 replacements made between 1995 and 1998. Infection defined as the presence of 1 or more polymorphonuclear cells per 10 enlargement fields had a reliability of 85%, 100% sensitivity and 79% specificity. Although there is some doubt about the ideal number of polymorphonuclear cells required to confirm a diagnosis of infection, these results suggest that this technique may facilitate the differential diagnosis of septic and aseptic loosening in prosthetic revision surgery.