STUDY DESIGN: Cross-sectional, observational study.
INTRODUCTION: There is little reported on the in vivo mechanics and behavior of extensor pollicis brevis (EPB) in relation to wrist position. Wrist position is known to significantly influence tendon excursion and therefore function of the digits. Ultrasound imaging (USI) can be used to assess in vivo tendon behavior and excursion. An improved knowledge of the excursion of the EPB tendon is important in understanding normal tendon mechanics and potentially pathological tendon disorders such as de Quervains tenosynovitis.
PURPOSE OF THE STUDY: To assess the reliability of using USI to measure EPB tendon excursion and to quantify EPB tendon excursion in 3 wrist positions.
METHODS: USI with speckle-tracking analysis were utilized to assess 49 normal EPB tendons (25 subjects). Tendon excursion was measured in wrist flexion (45°), wrist neutral and wrist extension (45°) on 2 different occasions.
RESULTS: The within- and between-session reliability of using USI to quantify EPB tendon excursion was "excellent" and "high," respectively. Wrist position had a significant influence on EPB tendon excursion (P ≤ .05). EPB excursion in the neutral wrist position was statistically greater than the other 2 positions (P < .05).
DISCUSSION: EPB tendon excursion has been shown to be dependent on the wrist positions of flexion and extension. The measures are notably lower than those found in cadaver studies; however, they follow a similar pattern with greatest excursion occurring in the neutral wrist position and least in flexion. This information is useful for EPB tendon rehabilitation and in consideration of biomechanics and pathogenesis of disorders that affect EPB tendon.
CONCLUSION: In vivo EPB tendon excursion measures have been quantified, and wrist position has been found to have an influence on excursion. USI with speckle-tracking analysis are considered to be reliable methods for measuring EPB tendon excursion.