# Measuring Dynamic Tendon Torsion Using Ultrasound Speckle Tracking: Validation with Silicone Phantom and In Vivo Application on Human Tibialis Posterior Tendon

## TL;DR

This study validates the use of ultrasound speckle tracking to measure dynamic torsion in tendons, both in silicone phantoms and in human tibialis posterior tendons.

## Contribution

The study introduces a validated and reliable method for in vivo dynamic torsion assessment of tendons using transverse plane ultrasound speckle tracking.

## Key findings

- Speckle tracking measurements on silicone phantoms strongly correlated with reference marker tracking (R2 = 0.81–0.95).
- In vivo measurements of the tibialis posterior tendon showed strong correlation between speckle tracking angles and foot pronation (R2 = 0.98–0.99).
- Test–retest reliability of the method was moderate to good (ICC = 0.73–0.87).

## Abstract

What are the main findings?
Transverse plane speckle tracking is validated for quantifying dynamic torsion angles on silicone phantoms.Speckle tracking can be applied to measure dynamic torsion of human tibialis posterior tendon with reliable results.

Transverse plane speckle tracking is validated for quantifying dynamic torsion angles on silicone phantoms.

Speckle tracking can be applied to measure dynamic torsion of human tibialis posterior tendon with reliable results.

What are the implications of the main findings?
Transverse plane speckle tracking is a valid and reliable method for assessing tendons’ dynamic torsion characteristics.Dynamic torsion assessments via speckle tracking may provide functionally and clinically relevant information regarding tendons’ dynamic torsion characteristics.

Transverse plane speckle tracking is a valid and reliable method for assessing tendons’ dynamic torsion characteristics.

Dynamic torsion assessments via speckle tracking may provide functionally and clinically relevant information regarding tendons’ dynamic torsion characteristics.

The torsional characteristics of human tendons are recognized to have functional and clinical relevance, but are underexplored due to the limited in vivo assessment methods available to measure the dynamic torsion characteristics of a tendon during movement. This study aimed to validate the use of transverse plane ultrasound speckle tracking (ST) for measuring dynamic torsion on silicone phantoms, and to evaluate the capability and reliability of ST in measuring dynamic torsion of the human tibialis posterior tendon (TPT) in vivo. Of the ten silicone phantoms tested in the validation study, ST measurement results strongly correlated with the referencing marker tracking method (R2 = 0.81–0.95) and had measurement error similar to or smaller than the hypothesized accuracy of 3° (p > 0.045). Subsequently, when ST was applied to nineteen healthy participants’ TPT in vivo, it was capable of characterizing the dynamic external torsion of the TPT during 0–20° passive foot pronation. Strong correlations were found between the ST-measured angle and the foot pronation angle (R2 = 0.98–0.99), and the test–retest reliability was moderate to good (ICC = 0.73–0.87). These findings suggested that ST is a valid and reliable method for measuring dynamic tendon torsion characteristics.