MRI of the Sinus Tarsi in Acute Ankle Sprain Injuries

PURPOSE: Our goal was to evaluate the visibility and incidence of traumatic abnormalities of the sinus tarsi in patients with acute ankle sprain injuries and compare these findings with the extent of lateral ankle ligament injuries on MRI. METHOD: Sixty athletically active patients (aged 18-45 years) with recent inversion trauma (< or = 7 days) underwent MRI. Replacement of fat tissue in the sinus tarsi was recorded. Inter/intraobserver agreement was calculated (kappa-statistics). Injuries of the three lateral ligaments, evaluated by MRI, were graded according to partial (1 point) or complete (2 points) tears for each of three lateral ligaments (together 0-6 points) and were compared with sinus tarsi abnormalities. RESULTS: In 26 patients (43%), replacement of sinus tarsi fat tissue was depicted by MRI. Inter/intraobserver agreement for MR changes of the sinus tarsi was good to moderate (kappa = 0.675/0.584). Grade of lateral ankle ligament injury showed a statistically significant difference (p = 0.033) between the two sinus tarsi groups (normal/abnormal). CONCLUSION: Acute ankle sprain injuries, evaluated by MRI, are associated with acute abnormalities of the sinus tarsi in 43% of patients and correlate with the extent of lateral ankle ligament tears.