Ultrasound identification and sonoanatomy of the inferior fascicle of the anterior talofibular ligament: a cadaveric study

PURPOSE: To demonstrate that the identification and visualization of the inferior fascicle of the anterior talofibular ligament (ATFLif) by ultrasound is feasible, to describe its sonoanatomy, and to compare the ultrasound anatomy of the superior (ATFLsf) and inferior (ATFLif) fascicles. METHODS: Sixteen fresh-frozen below-the-knee cadaveric ankles were evaluated. Longitudinal ultrasound scans of the ATFLsf and ATFLif were performed using a high-definition transducer. Anatomical dissection followed to expose the fascicles. The length of each fascicle was measured post-dissection using an analog caliper and compared with the sonographic findings. RESULTS: Ultrasound examination, dissection, and measurements were successfully completed in 16 specimens, with the ATFLif visualized in 14 and analyzed in 11. Measurements showed that the inferior fascicle is shorter than the superior fascicle. The intraclass correlation coefficient (ICC 2,1) between sonographic and post-dissection measurements was 0.9752 (95% CI 0.9128-0.9932), indicating the high reliability of the ultrasound method. CONCLUSION: The fibers of the ATFLif are visible and identifiable by ultrasound. These findings demonstrate the anatomical feasibility of ultrasound identification of both ATFL fascicles and support their inclusion in the systematic examination of the anterolateral ligament complex of the ankle.