2009 Abstract : 28

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Authors: Mabry TM, Berbari EF, Sems SA, Mayo Clinic, Rochester, MN

Title: The Microbiology of Prosthetic Joint Infection Following Arthroplasty Treatment of Hip Fracture

Purpose: The purpose of this study was to describe the microbiology of prosthetic joint infection (PJI) following arthroplasty treatment of hip fracture.

Methods: Patients for whom arthroplasty was the initial treatment for acute hip fracture were identified using an institutional joint registry. Those patients requiring a reoperation for infection, defined as a positive preoperative or intraoperative culture, were then selected for a detailed retrospective review of prospectively collected data. Hip arthroplasties performed for the sequelae of hip fracture, such as nonunion, osteonecrosis, and post-traumatic arthritis, were excluded. Culture-negative hip infections, as well as non-operatively managed hip infections, were also excluded.

Results: Between March 1969 and November 2008, 3178 arthroplasties were performed for the treatment of acute hip fracture at our institution. The study group consists of 43 patients (1.4 percent) who required a reoperation for culture-positive infection. The median age was 79 years at the time of arthroplasty. 39 patients were treated with hemiarthroplasty, and 4 patients were treated with total hip arthroplasty. Preoperative antibiotics were administered in 41 cases. Antibiotic-impregnated bone cement was used in 17 cases. The median interval between arthroplasty and reoperation for infection was 27 days (range, 10 days to 18.7 years). 24 hips were diagnosed with deep infection within 30 days of arthroplasty. 34 hips were infected with a single organism, and 9 hips were infected with multiple organisms, for a total of 57 isolates (see Fig. 1). Staph. aureus was the most common (24), followed by coagulase-negative Staphylococci (14). 17 hip arthroplasties performed before the year 2000 became infected, of which 3 (18%) were due to methicillin-resistant staphylococci (MRSE-2, MRSA-1). 26 hip arthroplasties performed since 2000 became infected, and 15 (58%) were due to methicillin-resistant staphylococci (MRSA-8, MRSE-7).

Discuassion and Conclusion: The number of hip fractures requiring arthroplasty treatment is expected to rise in parallel with the growing population of older adults. Prosthetic joint infection following hip arthroplasty is a relatively rare, but devastating complication. Previous studies have analyzed the microbiology of infection following elective total joint replacement or following hip fracture surgery with a variety of implants. This study described the microbiology of PJI in a large cohort of acute hip fracture patients treated exclusively with arthroplasty at a single institution.
The most striking finding was the high rate of drug resistance among the isolated organisms. In fact, methicillin-resistant staphylococci were identified in the majority of cases treated over the past ten years. Strategies aimed at reducing the burden of drug-resistant infection in the hip fracture population are urgently needed.