Diagnosing infection in patients undergoing conversion of prior internal fixation to total hip arthroplasty

• Published in: The Journal of arthroplasty Vol. 32; no. 1; pp. 241 - 245
• Main Authors: Gittings, Daniel, MD, Courtney, P. Maxwell, MD, Ashley, Blair, MD, Hesketh, Patrick, MD, Donegan, Derek, MD, Sheth, Neil, MD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2017
• Subjects: Adult; Aged; Aged, 80 and over; Area Under Curve; Arthroplasty, Replacement, Hip - statistics & numerical data; Biomarkers - blood; Blood Sedimentation; C-Reactive Protein - analysis; Cohort Studies; conversion total hip arthroplasty; Female; Fracture Fixation, Internal - adverse effects; hip fracture; Hip Fractures - surgery; Humans; Incidence; infection; Male; Middle Aged; Orthopedics; Philadelphia - epidemiology; Prostheses and Implants; Prosthesis-Related Infections - blood; Prosthesis-Related Infections - diagnosis; Prosthesis-Related Infections - epidemiology; Prosthesis-Related Infections - etiology; prosthetic joint infection; Retrospective Studies; Risk Factors; ROC Curve; Young Adult; conversion total hip arthroplasty; prosthetic joint infection; infection; hip fracture
• ISSN: 0883-5403; 1532-8406
• DOI: 10.1016/j.arth.2016.06.047

Abstract 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 2009-2014. Patients were diagnosed with infection preoperatively using Musculoskeletal Infection Society (MSIS) criteria or post-operatively if they were found to have positive cultures intra-operatively at time of conversion surgery. Medical comorbidities and preoperative inflammatory markers were compared between infected and non-infected groups. Univariate and multivariate logistic regression analysis were performed to identify independent risk factors for infection. Receiver operating characteristic (ROC) 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 33 patients were included in the study. 6 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/hr, CRP=2.0 mg/dL) versus non-infected (ESR=19.3mm/hr, CRP=1.3 mg/dL) groups (both p<0.01). ESR>30 mm/hr (OR 28.8, 95% CI 2.6–315.4, p=0.001) and CRP>1.0 mg/dL (OR 11.5, 95% CI 1.6–85.2, p=0.01) were strongly associated with infection. Receiver operating characteristic (ROC) curves for ESR (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.