Diagnostic capability of dynamic ultrasound evaluation of supination-external rotation ankle injuries: a cadaveric study

BACKGROUND: Ankle syndesmosis injuries are common and range in severity from subclinical to grossly unstable. Definitive diagnosis of these injuries can be made with plain film radiographs, but are often missed when severity or image quality is low. Computed tomography (CT) and magnetic resonance imaging (MRI) can provide definitive diagnosis, but are costly and introduce the patient to radiation when CT is used. Ultrasonography may circumvent many of these disadvantages by being inexpensive, efficient, and able to detect injuries without radiation exposure. The purpose of this study was to evaluate the ability of ultrasonography to detect early stage supination-external rotation (SER) ankle syndesmosis injuries with a dynamic external rotational stress test. METHODS: Nine, all male, fresh frozen specimens were secured to an ankle rig and stress tested to 10 Nm of external rotational torque with ultrasonography at the tibiofibular clear space. The ankles were subjected to syndesmosis ligament sectioning and repeat stress measurements of the tibiofibular clear space at peak torque. Stress tests and measurements were repeated three times and averaged and analyzed using a repeated one-way analysis of variance (ANOVA). There were six ankle injury states examined including: Intact State, 75% of AITFL Cut, 100% of AITFL Cut, Fibula FX - Cut 8 cm proximal, 75% PITFL Cut, and 100% PITFL Cut. RESULTS: Dynamic external rotation stress evaluation using ultrasonography was able to detect a significant difference between the uninjured ankle with a tibiofibular clear space of 4.5 mm and the stage 1 complete injured ankle with a clear space of 6.0 mm (P < .02). Additionally, this method was able to detect significant differences between the uninjured ankle and the stage 2–4 injury states. CONCLUSION: Dynamic external rotational stress evaluation using ultrasonography was able to detect stage 1 Lauge-Hansen SER injuries with statistical significance and corroborates criteria for diagnosing a syndesmosis injury at ≥6.0 mm of tibiofibular clear space widening.