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Published on: December 3, 2017
Results after late polymicrobial, gram-negative, and methicillin-resistant infections in knee arthroplasty
José Cordero-Ampuero1, Jaime Esteban, Eduardo García-Rey
1Cirugía Ortopédica y Traumatología, Hospital Universitario La Princesa, Universidad Autónoma de Madrid, Océano Antártico 41, Tres Cantos, 28760 Madrid, Spain. jcordera@telefonica.net
Background:
Previous studies of knee arthroplasty infections caused by high-virulence organisms suggest poor outcomes. Polymicrobial and Gram-negative infections are less studied.
Questions/Purposes:
This study compared the results of treatment of knee arthroplasty infections by single versus polymicrobial isolates, Gram-positive versus Gram-negative, and methicillin-resistant versus -sensitive Staphylococci.
Methods:
We prospectively followed 47 patients with late knee arthroplasty infections. The mean age was 72 years (range, 20-87 years). The treatment protocol included two-stage exchange and a combination of two oral antibiotics given for 6 months. Minimum followup was 1 year (average, 4.8 +/- 3 years; range, 1-12 years). Control of the infection was judged by absence of clinical, serologic, and radiologic signs of infection. The functional outcome was evaluated by Knee Society score at the last followup.
Results:
Infection was controlled in all 15 patients with polymicrobial and in 28 of 32 (88%) with monomicrobial infections, in eight of nine patients with Gram-negative and in 35 of 38 (92%) with Gram-positive isolates. Control was also achieved in 22 of 25 patients (88%) infected by methicillin-resistant Staphylococci and in 14 of 14 by methicillin-sensitive Staphylococci. The Knee Society scores averaged 81-63 in patients with polymicrobial infections and were higher than in monomicrobial infections (75-52). The mean KSS was 85-59 in Gram-negative infections compared to 75-55 in Gram-positive infections. The mean KSS was similar in methicillin-resistant (78-54) and methicillin-sensitive Staphylococci (73-56) infections.
Conclusions:
Polymicrobial and Gram-negative infections can be controlled in late knee arthroplasty infections. On the other hand, infections by methicillin-resistant Staphylococci are less likely to be controlled by the regimens we used.
Level Of Evidence:
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Insights
Polymicrobial and Gram-negative knee arthroplasty infections show good treatment outcomes. However, infections by methicillin-resistant Staphylococci were less successfully controlled with the studied regimens.
Area of Science:
- Orthopedic surgery
- Infectious disease
- Microbiology
Background:
- High-virulence organisms in knee arthroplasty infections are associated with poor outcomes.
- Polymicrobial and Gram-negative infections in knee arthroplasty are less understood.
- Limited data exists on treatment efficacy for diverse microbial profiles in knee arthroplasty infections.
Purpose of the Study:
- To compare treatment outcomes for knee arthroplasty infections based on microbial characteristics.
- To evaluate the efficacy of a two-stage exchange protocol with oral antibiotics for late knee infections.
- To assess the impact of single vs. polymicrobial, Gram-positive vs. Gram-negative, and MRSA vs. MSSA on infection control and functional outcomes.
Main Methods:
- Prospective follow-up of 47 patients with late knee arthroplasty infections.
- Treatment involved two-stage exchange and a 6-month course of two oral antibiotics.
- Infection control assessed by clinical, serologic, and radiologic signs; functional outcome by Knee Society score (KSS).
Main Results:
- Infection control rates were 100% for polymicrobial and 88% for monomicrobial infections.
- Gram-negative infections (8/9) and Gram-positive infections (35/38) showed high control rates.
- Methicillin-resistant Staphylococci (22/25) and methicillin-sensitive Staphylococci (14/14) had similar control rates.
- Polymicrobial infections had higher KSS (81-63) than monomicrobial (75-52).
- Gram-negative infections had higher KSS (85-59) than Gram-positive (75-55).
Conclusions:
- Polymicrobial and Gram-negative late knee arthroplasty infections can be effectively controlled.
- The treatment regimens used were less effective for methicillin-resistant Staphylococci infections.
- Further research is needed to optimize treatment for MRSA knee arthroplasty infections.
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