Tuberculous ankle versus pyogenic septic ankle arthritis: a retrospective comparison

Ankle tuberculosis (TB) manifests with varying symptoms and is easily confused with pyogenic septic ankle arthritis. In this study, all patients with either ankle TB or pyogenic septic ankle arthritis who were admitted to a medical center in southern Taiwan between May 1986 and October 2006 were reviewed retrospectively to identify risk factors for ankle TB. Compared with the 42 patients with culture-confirmed pyogenic septic ankle arthritis, the 26 patients with ankle TB (12 definitive, 5 probable, and 9 possible) were significantly more likely to have evidence of TB on chest radiographs (50 versus 10%; P<0.01), a history of trauma (58 versus 17%; P<0.01), presentation with sinus discharge (50 versus 12%; P<0.01), duration of symptoms of more than 3 months (69 versus 12%; P<0.01), a leukocyte count of <10,000/μL (58 versus 29%; P=0.03), and C-reactive protein of <5 mg/dL (42 versus 17%; P=0.03). Evidence of TB on chest radiographs was identified as an independent risk factor for ankle TB (odds ratio=35.1; 95% confidence interval=1.6‒779.8; P=0.02) by multiple logistic regression analysis. Awareness of these factors is essential for the accurate and timely diagnosis of ankle TB.