2005 Abstract : Cl 2

Authors: Esway JE, Rao, N, Vogt M, Crossett LS.

Title: Staged revision arthroplasty for chronic prosthetic joint infection (PJI) with comparison of outcome between resistant and sensitive bacteria.

Addresses:

Purpose: To determine and compare the recurrence rates for infections caused by resistant and sensitive bacteremia in staged revision arthroplasty for PJI.

Methods: The records of 149 patients with chronic total hip/knee infections were reviewed between 1988 and 2002. Infection was diagnosed based on clinical, WBC, ESR, CRP, aspiration, and operative findings. Patients presenting with <3 months after their index procedure were excluded from the study. Patients with chronic infection were treated with 1) removal of hardware, 2) 1 or more debridements with placement of an antibiotic spacer, 3) 6 weeks of intravenous antibiotics, and 4) re-implantation after declared free of infection. All antibiotic regimens were based on the expertise of one infectious disease consultant (NR). Follow-up was conducted every 3, 6, and 12 months, and 2 years. Success of therapy was defined as the absence of signs or symptoms of infection at the most recent follow-up, while failures were defined as clinical evidence of recurrence along with further debridements, removal of hardware, fusion, or amputation. Infections were then divided into 3 groups: a resistant group comprised of methicillin resistant Staphylococcus aureus and epidermidis, a senstive group of methicillin-sensitive Staphylococcus aureus and epidermidis, and a third group consisting of various other organisms alone or in mixtures. Comorbid variables were then compared to determine if they significantly affected the outcome by grouping patients as having either 2 or less or 3 or more medical conditions.

Results: In 149 patients, we found that our overall re-infection rate was 12.8%. Resistant Staphylococcus species (MRSA and MRSE) were re-infected in 23.1% of patients; whereas, sensitive Staphylococcus species (MSSA and MSSE) and other organisms were re-infected 12.5% and 7.0%, respectively (p = 0.163). MRSA was particularly resistant to treatment (re-infection rate of 26.7%), especially when found in combination with MRSE (40%). Although less common, pseudomonas also displayed a relatively high re-infection rate (40%) We additionally found that patients with 3 or more underlying medical conditions were more likely to fail treatment than healthier patients (20.5% versus 9.5%, p = 0.068). Interestingly, the use of post-revision suppressive antibiotics for an average of 5.8 months also seemed to influence outcome, decreasing the re-infection rate from 15.2% to 8.7% (p = 0.228). These comparisons did not achieve statistical significance but we feel they, nonetheless, reveal important trends that should be studied further.

Conclusions: Resistant organisms represent a significant percentage of infections, which tend to lead to a poor ourcome. Additionally patients with 3 or more medical conditions are likely to fail treatment. Post-op suppressive antibiotic therapy seems to influence the outcome by decreasing the infection rate.