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Diagnosing Infection in Patients Undergoing Conversion of Prior Internal Fixation to Total Hip Arthroplasty
Daniel J Gittings1, Paul M Courtney1, Blair S Ashley1
1Department of Orthopaedics, University of Pennsylvania, Philadelphia, Pennsylvania.
Insights
Infection risk factors for conversion total hip arthroplasty (THA) are unclear. Elevated preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) strongly indicate infection, aiding diagnosis.
Area of Science:
- Orthopedic Surgery
- Infectious Disease
- Diagnostic Markers
Background:
- Diagnosis of infected internal fixation implants before conversion total hip arthroplasty (THA) lacks clear criteria.
- Identifying infection risk factors in THA conversion is crucial for patient management.
Purpose of the Study:
- To identify risk factors for infection in patients undergoing conversion to THA.
- To evaluate the diagnostic utility of preoperative inflammatory markers for infection in this cohort.
Main Methods:
- Retrospective review of patients undergoing conversion to THA (2009-2014).
- Infection diagnosed using Musculoskeletal Infection Society criteria or intraoperative cultures.
- Comparison of comorbidities and inflammatory markers (ESR, CRP) between infected and non-infected groups.
- Logistic regression and ROC curve analysis to identify risk factors and assess marker performance.
Main Results:
- 18% of patients (6/33) were diagnosed with infection.
- No association found between comorbidities and infection.
- Significantly higher mean ESR and CRP in infected patients (P < .01).
- ESR >30 mm/h (OR 28.8) and CRP >1.0 mg/dL (OR 11.5) strongly associated with infection.
- ROC analysis showed good test performance for ESR and CRP (AUC = 0.89).
Conclusions:
- High incidence of infection observed in conversion THA patients.
- Preoperative ESR and CRP are effective screening tools for infection.
- Elevated inflammatory markers warrant strong suspicion for occult infection.
Background:
Criteria for diagnosis of infected internal fixation implants at the time of conversion to total hip arthroplasty (THA) are not clear. The purpose of this study is to identify risk factors for infection in patients undergoing conversion to THA.
Methods:
We retrospectively reviewed patients at a single institution who underwent conversion to THA from 2009 to 2014. Patients were diagnosed with infection preoperatively using Musculoskeletal Infection Society criteria or postoperatively if they were found to have positive cultures intraoperatively at the time of conversion surgery. Medical comorbidities and preoperative inflammatory markers were compared between infected and noninfected groups. Univariate and multivariate logistic regression analysis were performed to identify independent risk factors for infection. Receiver operating characteristic curves were generated to determine test performance of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). A post hoc power analysis was performed.
Results:
Thirty-three patients were included in the study. Six patients (18%) were diagnosed with infection. We found no association between comorbidities and infection in this cohort. The mean ESR and CRP were higher in infected (ESR = 41.6 mm/h, CRP = 2.0 mg/dL) vs noninfected (ESR = 19.3 mm/h, CRP = 1.3 mg/dL) groups (both P < .01). ESR >30 mm/h (odds ratio 28.8, 95% confidence interval 2.6-315.4, P = .001) and CRP >1.0 mg/dL (odds ratio 11.5, 95% confidence interval 1.6-85.2, P = .01) were strongly associated with infection. Receiver operating characteristic curves for ESR (area under the curve [AUC] = 0.89) and CRP (AUC = 0.89) demonstrated good fit.
Conclusion:
We report a high incidence of infection in patients who underwent conversion to THA. Preoperative ESR and CRP are effective screening tools though occult infections may still be missed. Patients with borderline or elevated inflammatory markers should raise strong suspicion for infection.
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