The validity and reliability of the Achilles tendon moment arm assessed with dual-energy X-ray absorptiometry, relative to MRI and ultrasound assessments

Dual-energy X-ray absorptiometry (DXA) in single energy mode has been shown to permit the visualisation of bone and soft tissue, such as patellar tendon through two-dimensional sagittal imaging. However, there is no validated DXA-based measurement Achilles moment arm (dAT). The aims this study were: 1) compare vivo DXA derived measurements dAT at rest against two previously methods: excursion (TE) magnetic resonance imaging (MRI) three ankle angles (-5°, 0° +10°). 2) analyse intra-day reliability method all between methods. Twelve healthy adults (mean ± SD: 31.4 9.5 years; 174.0 cm; 76.2 16.6 kg) participated study, involving test–retest scans, ultrasound scans one MRI scan. was defined distance from centre calcaneal-tibial joint axis (AT) muscle–tendon line action. measures were significantly greater than (19.7–24.9%) 45.2% larger TE method. technique high [CV = 1.38%; ICC 0.96] despite consistently lengths obtained using DXA, DEXA data strongly correlated (r 0.878, p < 0.001). In conclusion, allowed for highly reproducible rest, which implications calculation AT forces ability predict tool other, thereby providing a novel basis contrast existing future studies.