Reliability of ultrasonography measurement of the anterior talofibular ligament (ATFL) length in healthy subjects (in vivo), based on examiner experience and patient positioning

BACKGROUND: The most common cause of ankle injury is the supination trauma, inflicting a partial or complete rupture of the anterior talofibular ligament (ATFL). Among conventional diagnostic tools and procedures of sports injuries, the method of stress-ultrasonography is reportedly a promising diagnostic tool for examining injuries of the lateral ligaments of the ankle. Preceding studies predominantly examined the comparability of stress-ultrasonography and other established diagnostic tools in terms of efficacy, viability and quality. The purpose of this study was to assess the reliability of stress-ultrasonography of the ATFL based on varying examiner experience and patient positioning. METHOD: Sixteen healthy subjects were examined by four examiners with differing levels of skill and experience in ultrasonography, ranging from laymen to specialist. Measurements were recorded and interrater correlation coefficient (ICC) was applied in four positions, including a neutral position (A), medial rotation (B), plantar flexion (C) and inversion of the foot (D). RESULTS: The length of the ATFL was 14.958 ± 2.145 mm in position A, 15.886 ± 1.994 mm in position B, 16.270 ± 1.858 mm in position C and 15.170 ± 1.781 mm in position D. The average length change was 0.928 ± 0.804 mm (6.656 ± 6.299%) in position B, 1.313 ± 1.266 mm (9.746 ± 9.484%) in position C and 0.213 ± 1.807 mm (2.604 ± 12.308%) in position D. The correlation of the combined results of all four investigators was 0.333 for position A, 0.386 for position B, 0.320 for position C and 0.517 for position D. The highest ICC (0.811) was recorded between the orthopedic specialist and the radiology specialist. The lowest ICC (0.299) was recorded between the laymen and the radiology specialist. CONCLUSION: The reliability of the ATFL examination seems to be exceedingly dependent on the examiner’s experience and skill in ultrasonographic (US) diagnostic. Moreover, the inversion positioning of the foot, described by the European Society of Musculoskeletal Radiology (ESSR) yielded the highest measurement reliability.