Results after late polymicrobial, gram-negative, and methicillin-resistant infections in knee arthroplasty.
BACKGROUND
Previous studies of knee arthroplasty infections caused by high-virulence organisms suggest poor outcomes. Polymicrobial and Gram-negative infections are less studied.


OBJECTIVE
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.


METHODS
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Cordero-Ampuero
José
J
Cirugía Ortopédica y Traumatología, Hospital Universitario La Princesa, Universidad Autónoma de Madrid, Océano Antártico 41, Tres Cantos, 28760 Madrid, Spain. jcordera@telefonica.net
Esteban
Jaime
J
García-Rey
Eduardo
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D005500:Follow-Up Studies; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000097:blood / Q000188:drug therapy / Q000382:microbiology*; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011446:Prospective Studies; D016459:Prosthesis-Related Infections / Q000097:blood / Q000188:drug therapy / Q000382:microbiology*; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
D000900:Anti-Bacterial Agents; D002097:C-Reactive Protein