Portable Ultrasound Equals Arthroscopy for Assessment of Syndesmotic Instability

CATEGORY: Ankle; Arthroscopy INTRODUCTION/PURPOSE: Syndesmotic instability, when subtle, can be challenging to diagnose-and often requires visualization of the syndesmosis during applied stress. Portable ultrasonography is increasingly used to evaluate ankle instability at the point of care. This study aims to evaluate 1) whether portable ultrasonography (P-US) can diagnose syndesmotic instability in the sagittal plane, and 2) how P-US measurements compare to arthroscopic evaluation. METHODS: Eight fresh, above-knee cadaveric specimen were used. The syndesmosis was evaluated with P-US and arthroscopy in the intact state, and thereafter with progressive sectioning of, 1) anterior-inferior tibiofibular ligament (AITFL), 2) interosseous ligament (IOL), and 3) posterior-inferior tibiofibular ligament (PITFL). Sagittal plane translation was simulated with 100N of anterior to posterior (A to P) and posterior to anterior (P to A) directed force using a bone hook. Separately, a 50N manual force was applied to the fibular tip and measured with P-US to simulate a fibular 'shuck test' performed in the clinical setting. RESULTS: When all three syndesmotic ligaments were transected, there was a significant increase in fibular motion in the sagittal plane when evaluated using portable ultrasonography with application of 50N of manual pressure and when applying a 100N hook test when measuring total sagittal plane motion (p=<0.001 and p=0.009). Arthroscopy demonstrated significant increased motion with a 100N hook test when measuring total sagittal plane motion (p<0.001). CONCLUSION: P-US performed similarly to arthroscopy when diagnosing syndesmotic instability in the sagittal plane. P-US also offers several advantages over arthroscopy, including availability, non-invasiveness, low cost, and affording contralateral comparison. The promise of this technique suggests it should be further explored as a potential future standard for the diagnostic assessment of occult syndesmotic instability in the sagittal plane.