Date of Award

Spring 5-15-2015

Degree Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

Public Health

First Advisor

Richard Rothenberg, MD MPH

Second Advisor

Betty S. Lai, PhD

Abstract

Background: Although device-associated total joint arthroplasty (TJA) has the potential to greatly improve recipient quality of life, the occurrence of surgical site infection (SSI) thereafter can render drastically debilitating and costly consequences.

Methods: A retrospective cohort design was used to analyze hospital discharge data from the State Inpatient Database (State of California, years 2009-2011). Descriptive statistics were conducted to establish microbial prevalence and multivariate logistic regression was conducted to examine associations between various patient-centric risk factors and the development of SSI. Interaction terms were evaluated for model inclusion. Finally, elapsed time from TJA operation to infection diagnosis was assessed according to site of TJA, pathogen virulence, and pre-existing comorbidities.

Results: During retrospective review, 1769 infections were detected. The incident rate of infection was 2.70 infections per 100,000 person-days. Staphylococci species were the most prevalent microorganisms (79%), including methicillin-resistant S. aureus (MRSA 24%) and methicillin-susceptible S. aureus (MSSA 40%). Polymicrobial aetiology was identified in 5% of infections. The multivariate logistic model revealed increased odds of infection for knee vs. hip operations (OR = 1.50; 95% CI = 1.41 – 1.60), for male sex (OR = 1.70; 95% CI = 1.60 – 1.80), for increasing length of hospitalization (OR = 1.10; 95% CI = 1.09 – 1.11), and for comorbidities including obesity (OR = 3.99; 95% CI = 3.16 – 5.04), diabetes (OR = 1.45; 95% CI = 1.29 – 1.63), and rheumatoid arthritis (OR = 1.49; 95% CI = 1.19 – 1.87). Diagnostic delay differed significantly according to pathogen virulence, but not with comorbid status and site of TJA.

Conclusions: Staphylococci species were the most prevalent microbes identified in infected patients. Anatomical site of TJA, male sex, length of hospitalization, and existing comorbidities were significantly associated with increased odds of surgical site infection following operative TJA. Surveillance networks continue to be fundamental for understanding and reducing the burden of SSI as a subset of healthcare-associated infections.

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