Comparison of magnetic resonance imaging to physical examination for syndesmotic injury after lateral ankle sprain.

BACKGROUND: Clinical assessment of syndesmotic injury usually consists of two tests: the ankle external rotation test and squeeze test. This study sought to determine the sensitivity and specificity of both for syndesmotic injury secondary to lateral ankle sprain.

METHODS: Fifty-six patients with sprained ankles underwent clinical examination for syndesmotic injury with the aforementioned tests. Clinical findings were compared against magnetic resonance imaging (MRI) of the ankle. Sprains were graded on anatomical and functional classification scales, and correlation and agreement between both scales were assessed.

RESULTS: The MRI prevalence of syndesmotic injury in patients with lateral ankle sprains was 17.8%. Sensitivity and specificity were 30% and 93.5% for the squeeze test, and 20% and 84.8% for the external rotation test, respectively. Using the anatomical scale for sprain grading, 40% of syndesmotic injuries occurred in Grade I, 40% in Grade II, and 20% in Grade III sprains. Ten percent of patients with syndesmotic injury had no lateral ligament injury on MRI, 70% had injury of the anterior talofibular (ATFL) ligament, and 20% had injury to the ATFL and calcaneofibular (CFL).

CONCLUSION: The sensitivity of the squeeze test and external rotation test was low, suggesting that physical examination often fails to diagnose syndesmotic injury. Conversely, specificity was very high; nearly all patients with a positive test actually had syndesmotic injury. Severity of ankle sprain was not associated with prevalence of syndesmotic injury.