Diagnostic Validation of Dynamic Ultrasound Evaluation of Supination-External Rotation Ankle Injuries

Abstract Purpose: Definitive diagnosis of syndesmosis injuries can be made with plain film radiographs if the injury is severe enough, but often is missed when severity or image quality is low. Ultrasound diagnosis may circumvent many of these disadvantages by being inexpensive, efficient, and able to detect subtle injuries without radiation exposure. This study evaluates the ability of ultrasound to detect subtle SER ankle syndesmosis injuries with a dynamic external rotational stress test. Methods: Nine male fresh frozen specimens were secured to an ankle rig and stress tested to 10 Nm of external rotational torque with ultrasound monitoring 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. Ankle States Examined:

1. Intact State
2. 75% of AITFL Cut
3. 100% of AITFL Cut
4. Fibula Fx - Cut 8 cm proximal
5. 75% PITFL Cut
6. 100% PITFL Cut Results: Dynamic external rotation stress evaluation using ultrasound was able to detect a significant difference between the uninjured ankle tibiofibular clear space of 4.5 mm and the injured ankle with 100% of anterior inferior tibiofibular ligament cut 6.0 mm (P=.017). Additionally, this method was able to detect significant differences between the uninjured ankle and the injured states. Conclusion: Dynamic external rotational stress evaluation using ultrasound 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.