High Rate of Positive Cultures in Patients Referred With Antibiotic Spacers as Part of 2-Stage Exchange

Abstract

Background: Two-stage exchange for periprosthetic joint infection (PJI) in total knee arthroplasty (TKA) remains the gold standard treatment in North America. Occasionally, patients with knee PJI are referred for definitive management after resection and antibiotic spacer placement. Currently, little literature exists to suggest how these patients should be managed. The purpose of this study is to report the clinical outcomes of these patients.

Methods: We retrospectively identified 54 patients (54 knees) from 2000 to 2012 treated for PJI with initial TKA resection and spacer placement performed somewhere other than the definitive treatment center. The mean age at reimplantation was 64 years, with 59% being male. Redebridement and antibiotic spacer exchange was performed for all patients. Mean follow-up was 6.5 years.

Results: Of the 54 knees, 22 (41%) grew an organism from a culture taken at the time of redebridement and spacer exchange. The most common organism identified at redebridement was Staphylococcus aureus (41%). Obtaining positive cultures at redebridement was not associated with presenting erythrocyte sedimentation rate (P = .46), C-reactive protein (P = .57), or the presence of retained cement (P = .13). Forty-nine of 54 (91%) knees were ultimately reimplanted. Two-year survivorship free of infection in reimplanted knees was 98%.

Conclusion: Patients referred with an antibiotic knee spacer for PJI have a high rate of positive cultures at the time of redebridement. Neither the presenting serology nor the identification of retained cement was associated with obtaining positive cultures at the time of redebridement. Nevertheless, this unique cohort of patients has favorable outcomes when redebrided with spacer exchange prior to reimplantation.

Keywords: 2-stage exchange arthroplasty; TKA revision; antibiotic spacer; periprosthetic joint infection (PJI); total knee arthroplasty (TKA).