Reliability and Anatomical Agreement of High-Resolution Ultrasound for Measuring the Length and Thickness of the A1 Pulley: A Cadaveric Study.

Accurate assessment of the A1 pulley is essential for the diagnosis and treatment of trigger finger, particularly in ultrasound-guided percutaneous release. Although high-resolution ultrasound is widely used to evaluate pulley morphology, the validity of sonographic measurements of A1 pulley length has not been clearly established against anatomical reference standard. This study evaluated the reliability and validity of ultrasound for measuring A1 pulley length and thickness in human cadavers and assessed the reproducibility of A2 pulley length. Twenty fingers from five fresh-frozen cadaveric hands were examined. Two blinded expert musculoskeletal sonographers independently performed ultrasound acquisition and measurements of A1 and A2 pulley length and A1 pulley thickness, while a third blinded observer obtained anatomical measurements after meticulous dissection using a digital caliper. Ultrasound systematically overestimated A1 pulley length compared with anatomical measurements and showed very poor reliability (ICC = 0.05) with wide limits of agreement. In contrast, A2 pulley length showed high interobserver reliability (ICC = 0.83) and relatively better agreement with anatomical values, whereas A1 pulley thickness showed moderate reproducibility (ICC = 0.61). Overall, A1 length measurements showed substantial variability and limited agreement, while A2 length and A1 thickness appeared more consistent within this experimental setting. These findings should be interpreted within the limitations of a cadaveric model.