2004 Abstract : CS 8

Authors: Muttagi V1, Gomez J1, Componovo R2, Schutte D2, Cantey J1

Title: Epidemiology and Outcome of the Treatment of Infected Primary Hip and Knee Prostheses at the Medical University of SC

Addresses: 1Division of Infectious Diseases and Department of Orthopedics, P.O. Box 250752, Medical University of SC, Charleston, SC, 29425, 2

Purpose: The Orthopedic Service at the Medical University of SC placed 247 prosthetic hips or knees in 2003 and serves as a referral center for failed prosthetic joints placed at other sites. There were 31316 discharges coded as hip and knee replacements in SC in the past five years. At the same there were 1455 discharges coded as infected hip and knee replacements. MUSC serves as a referral center for many failed prosthesis. The purpose of our study was to review the MUSC experience with infected prosthesis

Methods: The Infectious Diseases Division at MUSC has kept a prospective database of all infected hip and knee prosthesis treated at our facility. We review our experience with infected primary prostheses from July 1999 through December 2003. Criteria for inclusion were an ICD-9 code 996.66, a diagnosis of infection by Infectious Diseases, and either positive synovial biopsy and/or positive preoperative joint fluid and/or intra-operative tissue cultures. Information recorded included patient history, demographics, BMI, microbiology, surgical procedures, and outcome. Good outcomes were those with retention of prosthesis or successful reimplantation. At follow-up these patients had functional prosthesis with minimal or no symptoms

Results: The database contains 142 records of which 80 were infected primary prostheses and met our criteria for inclusion. 52 (65%) were referred cases. 52 (65%) were Caucasians and 28 (35%) were African American (AA). 63% were female. Mean age was 64 years (range 28-90). 59% of patients had a TKA. 23% of whites and 39% of AAs were diabetic. 25% of patients had polymicrobial infections. Among patients with positive cultures (92%), 29% grew coagulase negative staphylococci, 23% grew S. aureus (6/24 strains were MRSA). Six patients grew group B streptococcus, and six grew enterococcus. 10 patients grew gram negative rods, two grew C. albicans. 17 grew miscellaneous other organisms. Only 46% (p=0.07) of knee prostheses versus 67% of hip prostheses had a good outcome. Four of five MRSA infected patients did poorly (p=0.15) compared to MSSA infected patients. Multiple univariate analysis did not show statistically significant differences between outcomes and multiple variables. Multiple logistic regression models singled out no factor as significant except for a trend for the joint (knee versus hip) to influence outcome

Discussion: Our patient population differs greatly from published data. The AA population is better represented, and there is a higher percentage diabetics. Infecting agents are similar to those reported elsewhere. In our data set infected knee prosthesis appeared to have considerably worse outcomes than hips. The poor outcome of two stage revisions is surprising and much larger than expected from the literature

Significance: The infected prosthetic joint patient population is SC is differs greatly from the literature. Outcomes are worse as well. Small sample size did not allow determination of the responsible factors