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Author(s): Camelia E. Marculescu, MD, MSCR, Joseph R. Cantey, MD; Division of Infectious Diseases, Medical University of South, Carolina, Charleston, SC

Title: Polymicrobial Prosthetic Joint Infections (Poly PJIs)- Risk Factors and Outcome

Purpose: To determine the outcome and factors associated with poly PJIs.

Methods: All episodes of THA and TKA PJIs treated at our institution between 1/98-11/2006 were reviewed. The survival free of treatment failure (TF) was assessed by the Kaplan-Meier method. Multivariable logistic regression was used to identify factors associated with poly PJIs. Thirty four of 174 PJI episodes (19%) were polymicrobial. 62% of these (21/34) involved a THA. P. aeruginosa, other GNB, enterococci were present in 26%, 35% and 32% of poly PJI episodes. MRSA (26.4% vs 7.1%, p = 0.001) and anaerobes (11.7% vs 2.8%, p=0.04) were more common in poly than in monomicrobial (mono) PJIs.

Results: Compared to the mono PJIs, poly PJIs occurred in patients h65 years (67% vs 49%, p = 0.05),presented with a soft tissue defect/dehiscence (23.5% vs 2.8%, p = 0.0002), drainage (79.4% vs 39.2%, p < 0.0001), had prior local irradiation (8.8% vs 0.71%, p = 0.02), and less bacteremia (0 vs 14.2%, p = 0.01). Poly and mono PJIs did not significantly differ in gender, type of co-morbidities, immunosuppressive therapy, median duration of intravenous antimicrobial therapy, prior joint revisions, type of surgery (two-stage-TSE, one-stage revision, debridement/retention-DR). The 2-year cumulative probability of success of poly PJIs was 63.8% (95% CI: 43.8%-80.5%) and of mono PJIs was 72.8% (95% CI: 63-80.9%) (p = 0.24). 26%, 38%, and 29% of poly PJI episodes were treated with TSE, DR, resection arthroplasty, and the 2 year survival free of TF in each group was 77.7%% (95% CI: 42.8%-94.2%), 52.7% (95% CI: 28.4%-75.9%) and 64.2% (95% CI: 28.7%-88.9%). In multivariable analysis, presence of a soft tissue defect /dehiscence (OR: 5.9, 95%CI: 1.5- 23.3), drainage (OR: 5.0, 95% CI: 1.9-12.9), and ageh65 years (OR: 2.8, 95%CI: 1.1-6.8) were factors significantly associated with poly PJIs.

Discussion: Polymicrobial PJI is relatively frequent at our institution. Factors associated with poly PJIs include presence of drainage, soft tissue defect/dehiscence and age h65 years. MRSA and anaerobes were present more in polymicrobial cultures. The outcome of poly PJIs is in general favorable, especially when treated with TSE.

Musculoskeletal Infecton Society
Musculoskeletal Infecton Society
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