Treatment of Periprosthetic Knee Infection With a Two-stage Protocol Using Static Spacers

Two-stage exchange arthroplasty is a standard approach for treating total knee arthroplasty periprosthetic joint infection in the United States, but whether this should be performed with a static antibiotic spacer or an articulating one that allows range of motion before reimplantation remains controversial. It is unclear if the advantages of articulating spacers (easier surgical exposure during reimplantation and improved postoperative flexion) outweigh the disadvantages of increased cost and complexity in the setting of similar rates of infection eradication.

The purposes of this study were (1) to determine the ultimate range of motion; and (2) to determine the proportion of patients who remained free of infection at a minimum 2 years after treatment with static antibiotic spacers as part of a two-stage revision TKA for the treatment of periprosthetic joint infection.

Between 1999 and 2011, we treated 121 patients with chronically infected TKAs, of whom three had medical comorbidities precluding a two-stage exchange, four had died before 2-year followup for reasons other than the surgical intervention, and seven were lost to followup. The remaining 107 patients (109 knees; 53 men and 54 women) were treated using a two-stage approach with static spacers and are evaluated here at a mean of 3.7 years (range, 2.0-9.8 years); no patients were treated with articulating spacers during this study period. Twenty-five percent (27 of 109) of the organisms isolated the first-stage procedure were resistant to methicillin and/or vancomycin. Median age at the time of reimplantation was 67 years (range, 42-89 years). Range of motion was measured by an independent physical therapist with a standard goniometer. Knee Society knee and function scores were calculated before the first stage and at the 2-year mark. Because many of these patients were treated before consensus definitions of infection were established, we made the diagnosis of infection (and established that a patient was believed to be free of infection) using the approaches prevalent at that time, which generally included presence of a sinus tract communicating directly with the implant, two positive tissue cultures, or a combination of cultures, fluid analysis, and serology.

Postoperatively, 67 knees had full extension and no patients had a flexion contracture > 10°. Median flexion was 100° (range, 60°-139°). Thirty-nine knees had postoperative flexion > 120°. Ninety-four percent of patients were clinically free of infection at last followup.

Our two-stage exchange protocol with static spacers yielded comparable flexion and infection eradication when compared with other recent studies that have used articulating spacers. The large proportion of resistant organisms is alarming. Future multicenter studies should compare static with articulating spacers and should evaluate both cost and efficacy, because our study suggests that adequate range of motion can be achieved without the added cost of the articulating spacer.

Level IV, therapeutic study.