Objective: Ankle sprain severity is difficult to assess initially in the emergency department, yet it governs treatment decisions. Ultrasonography readily shows fluid present in the talocrural joint, which is difficult to assess by physical examination. The purpose of this study was to evaluate the prevalence of ultrasonographic talocrural joint effusion in moderate and severe ankle sprains and to determine the cause of effusions by magnetic resonance imaging (MRI).
Methods: Consecutive patients 18 to 55 years of age with moderate and severe ankle sprains within the previous 48 hours were included if they had no history of abnormalities in the same ankle within the last 12 months. When ultrasonography with the ankle in the neutral position showed talocrural effusion, MRI was performed within 8 days.
Results: Of the 110 patients (83 men and 27 women; mean age, 24.2 years), 40 (36.4%; 95% confidence interval, 27.6%-46.1%) had joint effusion on ultrasonography and MRI. In 39 of these 40 patients, MRI visualized damage to the anterior talofibular ligament (positive predictive value, 97.5%; 95% confidence interval, 85.3%-99.9%), accompanied in 5 (12.8%) cases by damage to the calcaneofibular ligament. In 14 (35%) cases, MRI showed cartilage damage or bony contusion.
Conclusions: Talocrural effusion on ultrasonography may identify patients with severe ankle sprains. Magnetic resonance imaging should be performed in patients with talocrural effusion. Further work is needed to evaluate the usefulness of MRI in acute ankle sprains without talocrural effusion.