Evaluation of preoperative cultures before second-stage reimplantation of a total knee prosthesis complicated by infection - A comparison-group study

Background: Two-stage reimplantation has proven to be highly successful in the treatment of patients,vith infection at the site of a total knee arthro plasty. However, up to 20 percent of patients have a recurrence of infectio n following this treatment. The purpose of our study was to determine wheth er aspiration of the affected joint and culture of the specimen, performed before reimplantation and after discontinuation of antibiotic therapy, woul d help to identify patients who might have a recurrent infection. Methods: We prospectively followed sixty-nine patients who were treated for a culture-proven deep infection at the site of a total knee arthroplasty. Group I consisted of thirty-five patients who were treated with removal-of the prosthetic components and irrigation and debridement of the joint, foll owed by six weeks of antibiotic therapy and reimplantation of a prosthesis. Group II was composed of thirty-four patients who were treated,vith remova l of the components and irrigation and debridement of the joint, six weeks of antibiotic therapy, and then repeat culture four weeks after the antibio tic course had ended. If the culture was negative, the patient was managed with a second-stage reimplantation of a prosthesis. If the culture was posi tive, the protocol was repeated, beginning,vith irrigation and debridement. The two groups were similar with regard to male-to-female ratio, age, preo perative Knee Society scores, time since primary surgery, types of infectio us organisms, duration of symptoms, duration of follow-up, and number of pr evious revisions. All of the patients were evaluated clinically with use of the objective scoring system of the Knee Society and were followed with se rial radiographs. Success was defined as no infection and a functional pros thesis, with a Knee Society score of at least 75 points at the last (thirty -six-month-minimum) follow-up evaluation. Results: Of the thirty-five patients in Group I, five (14 percent) had recu rrence of infection. One of the patients was managed,vith a successful seco nd-stage revision, three were managed,vith arthrodesis of the knee, and one continued dwith chronic antibiotic suppressive treatment. Of the thirty-fo ur patients in Group II, three (9 percent) had a positive culture after the course of antibiotics. The protocol was repeated for all three, and they s ubsequently had a successful second revision. One other patient (3 percent) in Group Il, who had a negative culture, had a recurrent infection and was eventually managed,vith arthrodesis of the knee. Conclusions: Prerevision cultures, grown after discontinuation of antibioti c treatment and before reimplantation of the components, helped to identify the patients with infection at the site of a total knee arthroplasty in wh om the infection might recur. The performance of aspiration and cultures re sulted in a substantial improvement in the clinical outcome.