We retrospectively reviewed the database of 66 patients (68 knees). These 66 patients underwent a second two-stage revision TKA between January 2001 and January 2010. Of the 66 patients, 3 (4.5%) were lost to follow-up before 1 year, leaving 63 patients (65 knees) for review. Two patients had bilateral periprosthetic joint infection of the knees and they underwent simultaneous two-stage revision TKAs. The records of 63 patients had been entered into an ongoing computerized database that was updated continuously (Fig. 1). We performed irrigation and debridement after removal of the polyethylene spacer and replaced new polyethylene spacer, with retention of prosthesis as the initial treatment in all patients. Irrigation and debridement failed in all patients undergoing irrigation and debridement, resulting in two-stage revision TKA. There were 25 men and 38 women, with a mean age of 67 ± 10.2 years (range, 40 to 78 years) at the time of a second revision TKA. The mean body mass index was 28.9 ± 2.9 kg/m2 (range, 22 to 38.5 kg/m2). The study was approved by the institutional review board, and all patients provided written informed consent. The American Society of Anesthesiology (ASA) Score was 2 in 55 patients and 3 in the other 8 patients. Patients were followed at 3 months, 1 year after a second revision TKA and then 2 or 3 years or until a recurrence of infection. The mean follow-up period was 15.1 years (range, 10 to 19 years) after a second two-stage revision TKA and the mean follow-up from time of a third two-stage revision for the 12 TKAs was 7 years (range, 5 to 10 years).
Periprosthetic joint reinfection was diagnosed against the criteria of Musculoskeletal Infection Society (MSIS) [17]. Reinfection was confirmed with positive cultures through aspiration and intraoperative cultures in 59 of the 65 knees (91%) while the other 6 knees met at least one of the 3 criteria: ESR > 20 mm/hr; CRP > 0.5 mg/dL; joint aspiration leukocyte count over 1,100 cells/μL and neutrophil percentage greater than 64%; evidence of purulence during the subsequent surgical intervention [16, 17].
Causative infective organisms included sStaphylococcus aureus in 21 knees (32%), methicillin-resistant Sstaphylococcus aureus in 10 (15%), Staphylococcus epidermis in 9 (14%), Streptococcus anginosus in 7 (11%),E nterococcus cloacae in 6 (9%), Candida albicans in 3 (5%), and Candida lusitaniae in 3 (5%). In 6 knees (9%), no organisms were cultured (Table 1). Sixty-two of 65 knees (95%) had the same bacteria and 3 knees (5%) had a different bacteria from the first two-stage revision of TKA; 60 knees (92%) had the same bacteria and 5 knees (8%) had a different bacteria from the second two-stage revision; 13 of 16 knees (82%) had the same bacteria and the remaining 3 knees (18%) had multi-organisms from the third two-stage revision.
All patients underwent removal of all the well-fixed LCCK implants and, mobile bone cement spacer and debridement and placement of a tobramycin-impregnated (1.2 g per 40 g batch of bone cement) mobile cement spacer. Antibiotics were administered intravenously for 6 weeks. After completion of antibiotic therapy, ESR, CRP levels, total WBC count and differential in the joint aspirates and culture from the joint fluid were obtained and the patient was observed for 2 more weeks. If these tests yielded negative results and there was no clinical evidence of recurrent infection (ESR < 20 mm/hr; CRP < 0.5 mg/dl; and joint WBC < 1100 with (64%), we performed a second or third two-stage revision TKA. Multiple cultures of specimens (more than 5 cultures) obtained during a second or third revision operation were performed to confirm negative culture results. The antibiotic-impregnated spacer was removed and Legacy Constrained Condylar Knee prosthesis (LCCK; Zimmer, Warsaw, Indiana) was inserted and fixed with antibiotic-impregnated bone cement (1.2 g tobramycin mixed with 40 g of cement). For fungus infection, amphotericin-impregnated bone cement was used. After reimplantation, antibiotics were stopped at about 2 weeks by recommendation of infectious disease consultant, when the intraoperative cultures were negative, except in one patient in whom chronic oral suppressive antibiotic therapy was used.
At each follow-up, we evaluated the patients clinically and obtained radiographs of knees. Pre-revision and post-revision review data were recorded according to the systems of the Knee Society [18]. All of the knees were evaluated by one orthopedic surgeon who was not connected with the surgery, and the data were entered into a computerized record.
One of the team members evaluated the final radiographs. We defined radiographic loosening as a complete radiolucent line of ≥ 2 mm in width at the bone-cement or prosthesis-cement interface or a shift in position of a component on serial radiographic examination [18].
Descriptive statistics were described as the number (percentage) or mean (range). The chi-square test and Fisher exact test were used to compare binary variables. All calculations assumed 2-tailed test. The level of significance was set at P < 0.05. All analyses were performed with SPSS, version 14.0 (SPSS Inc, Chicago, IL).