ASPIRATION OF THE HIP-JOINT BEFORE REVISION TOTAL HIP-ARTHROPLASTY - CLINICAL AND LABORATORY FACTORS INFLUENCING ATTAINMENT OF A POSITIVE CULTURE

The value of routine aspiration of the hip joint before revision of a hip arthroplasty remains controversial. We reviewed the results of suc h aspirations in an attempt to determine clinical or laboratory factor s that could help the surgeon to identify hips that are infected and t hat should be aspirated preoperatively. One hundred and fifty consecut ive revision total hip arthroplasties were performed by one of us. Pre operative aspiration was not performed or data were excluded for eight hips; no fluid was obtained from one of these hips (0.7 per cent of t he 150). Of the remaining 142 hips, 128 had preoperative aspiration on ce and fourteen, twice. Twenty-one (15 per cent) of the 142 hips were infected, as demonstrated by the intraoperative culture. The intraoper ative culture for two of these hips, however, was considered to be fal se-positive. The initial aspiration was considered to be positive only if an organism grew on the solid medium or if grossly purulent fluid was obtained. The initial aspiration was positive for nineteen hips; o n culture of specimens from one hip, Bacteroides thetaiotaomicron grew in the liquid medium only; and purulent fluid was obtained from one h ip but no organisms grew on culture. Fourteen aspirations were repeate d for various reasons, most commonly to confirm the presence of an unu sual organism. The repeat aspiration did not change the diagnosis for these hips. When the two hips with a false-positive intraoperative cul ture were excluded, preoperative aspiration had a sensitivity of 92 pe r cent, a specificity of 97 per cent, and an accuracy of 96 per cent. Seventeen of the nineteen truly infected hips were associated with an abnormally elevated erythrocyte-sedimentation rate (mean, 80.8 millime ters per hour). However, fifty-eight (50 per cent) of the 116 hips tha t were not infected, and for which the results were available, also ha d an abnormally elevated erythrocyte-sedimentation rate (mean, 32.0 mi llimeters per hour). This difference was significant (p = 0.001, Fishe r exact test). The peripheral leukocyte count was not helpful in predi cting infection. Hips in which the implants had been in situ for more than five years were less likely to be infected (p = 0.008, Fisher exa ct test) than those in which the implants had been in situ for five ye ars or less. None of the infected hips in which the implants had been in situ for more than five years were associated with a normal erythro cyte-sedimentation rate. In this study, preoperative aspiration of the hip joint had an excellent sensitivity and specificity with regard to the prediction of infection. On the basis of our findings, we now fav or a selective approach to aspiration, as determined by the erythrocyt e sedimentation rate and the amount of time that the implant has been in situ.