Comparison of portable ultrasound and arthroscopy for assessing sagittal fibular translation for assessment of syndesmotic instability.

Objectives: To evaluate 1) whether portable ultrasonography can evaluate syndesmotic instability in the sagittal plane, and 2) how portable ultrasonound measurements compare to arthroscopic evaluation.

Methods: Eight fresh, above-knee cadaveric specimens were used. The syndesmosis was evaluated with portable ultrasonound 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 50N and 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 portable ultrasound to simulate a fibular "shuck test" performed in the clinical setting. Agreement between portable ultrasound and arthroscopic measurements of fibular translation was assessed using Bland-Altman analysis.

Results: When all three syndesmotic ligaments were transected, there was a statistically 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 a statistically significant increased motion with a 100N hook test when measuring total sagittal plane motion (p<0.001). Bland-Altman analysis between 50N manual portable ultrasound and 100N hook arthroscopy showed a mean difference of -0.24 with 95% limits of agreement ranging from -1.58 to 1.10.

Conclusions: Portable ultrasonound could detect increased fibular motion in the sagittal plane after progressive syndesmotic ligamentous injury and demonstrated acceptable agreement with arthroscopy. Portable ultrasonound 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.

Level of evidence: Not Applicable, diagnostic cadaver study.