Risk factors for prosthetic hip and knee infections according to arthroplasty site

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Summary

Prosthetic joint infection is a devastating complication of arthroplasty. Previous epidemiological studies have assessed factors associated with arthroplasty infections but have not assessed the impact of comorbidity on infection at different arthroplasty locations. We used a case–control design to investigate risk factors for prosthetic joint infection with reference to the anatomical site. During an eight-year period at a single hospital, 63 patients developed a prosthetic joint infection (36 hips, 27 knees). Cases of prosthetic hip or knee joint infection were matched 1:2 to controls. The results suggest that factors associated with arthroplasty infections differ with anatomical location. Following knee arthroplasty, wound discharge was associated with an increased risk of prosthetic joint infection whereas the presence of a drain tube reduced the risk. By contrast, increased body mass index, increased drain tube loss and superficial incisional surgical site infections (SSIs) were associated with prosthetic hip infection. When analysed as a combined cohort, systemic steroid use, increased SSI drain tube losses, wound discharge, and superficial incisional SSIs were predictors of infection.

Introduction

Infection of the prosthetic joint is a significant complication of arthroplasty, occurring at a rate of 2–3% per year in most series.1 These infections are associated with significant morbidity and mortality.2 In addition, the financial cost to the health system is considerable, with estimated hospital costs of US $96,166 per patient requiring revision arthroplasty for infection.3 Over time, the number of people requiring prosthetic joint replacement is expected to increase; US Medicare data predict that by 2030 the number of patients undergoing primary hip and knee replacement will increase by 174% and 673% respectively.4 Identifying patients at increased risk of prosthetic joint infection is important: it could inform preoperative assessment to optimise patient comorbidity and might increase the diagnostic acumen of clinicians.

Current epidemiological studies examining clinical risk factors do not usually take the site of the prosthetic joint into account. Risk factors may vary according to which joint is replaced.

Section snippets

Methods

This case–control study was designed to examine the impact of patient comorbidity, operative and postoperative factors on the risk of subsequent prosthetic joint infection with particular reference to the joint replaced. The study was conducted at a metropolitan university-affiliated tertiary hospital in Australia. This orthopaedic unit is currently staffed by 17 orthopaedic surgeons performing over 1200 prosthetic joint replacements per year. The study population consisted of all patients who

Results

Between 1 January 2000 and 31 January 2007, 63 patients (27 having knee replacements and 36 hip replacements) developed a prosthetic joint infection. The demographic characteristics of cases and controls are shown in Table II.

The mean interval between arthroplasty and diagnosis of prosthetic joint infection was 54 days (range: 5–277 days). Causative pathogens involved in the prosthetic joint infections in the cases identified by deep, intraoperative tissue specimens are shown in Table III. In

Discussion

The results of this study suggest that risk factors for prosthetic joint infection differ according to the joint replaced. Therefore grouping all joint replacements for analysis may miss some relevant risk factors. Superficial infection and wound discharge were associated with the development of prosthetic joint infection irrespective of arthroplasty site. The association between hip arthroplasty and obesity has been delineated previously, with studies showing that morbidly obese patients have

Acknowledgements

Assistance with study design and statistical analysis was provided by Dr N.M. Peel, Australasian Centre on Ageing, University of Queensland.

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