ASPIRATION OF THE KNEE-JOINT BEFORE REVISION ARTHROPLASTY

Sixty-four operative procedures were performed on 55 patients with kne e arthroplasties for pain, loosening, instability, or suspicion of inf ection. Forty-three knees had a preoperative aspiration. In 19 knees, the aspiration showed growth on solid media, and in 18 of these knees the diagnosis of infection was confirmed by the intraoperative culture s. In 1 knee with an infected total knee replacement, the patient was receiving an intravenous antibiotic at the time of arthroscopic irriga tion and debridement and the cultures showed no growth. In 23 of 24 kn ees with a negative preoperative aspiration, the intraoperative cultur es showed no growth on solid media. In 1 knee with a preoperative aspi ration that had negative results, a single intraoperative culture grew Staphylococcus epidermidis. However, the presenting symptoms, examina tion, preoperative radiographs, and intraoperative evaluation were con sistent with aseptic loosening of a cemented total knee arthroplasty. Thus, the preoperative aspiration of the prosthetic knee joint had a s ensitivity of 100%, specificity of 100%, and accuracy of 100%. The Wes tergren erythrocyte sedimentation rate, peripheral leukocyte count, an d presenting symptoms correlated poorly with infection, Radiographs we re also not helpful in the diagnosis of infection, with loosening of c omponents, periostitis, focal osteolysis, and radiolucent lines freque ntly seen in infected and noninfected knees. Preoperative aspiration o f the knee is the most helpful study for the diagnosis or exclusion of infection in a prosthetic knee joint.