SHEAR WAVE PROPAGATION ALONG THE ACHILLES TENDON MEASURED WITH TENSIOMETRY: MECHANICAL VERSUS MANUAL IMPULSE

A. Schneebeli^1,2, D. Falla¹, C. Cescon², M. Barbero²

¹University of Birmingham, School of Sport, Exercise Rehabilitation Sciences, College of Life Environmental Sciences, Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), Birmingham, United Kingdom, ²University of Applied Sciences and Arts of Southern Switzerland, Department of Business Economics, Health and Social Care, Rehabilitation Research Laboratory 2rLab, Manno, Switzerland

Background: Given the growing clinical and research interest in evaluating tendon mechanical properties, different assessment techniques have been developed over the last few years. Amongst them, shear wave tensiometry is an innovative technology for measuring the speed of propagation of mechanical waves along the tendon. Its capacity to characterize Achilles tendon loading has been confirmed both in vitro and in vivo.
This technology uses accelerometers to measure wave propagation along the tendon generated by a tapping device that provides a mechanical impulse on the tendon. The impulse can be generated also manually using a common reflex hammer, which has potentially positive implications in terms of costs and clinical applicability.

Purpose: The aim of this study was to test the convergent validity of two different methods to generate mechanical impulses (i.e., tapping device versus reflex hammer) given to calculate mechanical shear wave along the Achilles tendon.

Methods: Ten (5 male and 5 female) healthy participants were prospectively recruited. Shear wave propagation along the tendon was calculated using four accelerometers (Analog Devices, ADXL202JE) aligned along the direction of the tendon and equally spaced at 1.5 cm distance. Impulse on the Achilles tendon to generate shear wave was provided in two different ways, one mechanical impulse provided by an actuator based on electromagnetic transductor and one manual impulse performed by a trained operator with a reflex hammer. Participants were asked to lie on an examination bed with the foot in 0° of plantar flexion and perform two isometric contractions (1 kg-10 kg). A measure was also performed in the relaxed state. The mean of 10 impulses was used to calculate the shear wave speed for each condition. Convergent validity between the two types of impulse was calculated using the intraclass correlation coefficient (ICC). The Bland Altman analysis was performed to quantify the agreement between the two methods.

Results: Convergent validity between the two types of impulse is very high (almost perfect) with ICC values ranging from 0.961 to 0.981. The Bland Altman plot confirm the validity of this measure; the mean of the difference between the measures was 0.66 and the upper and lower limit of agreement ranged between 4.08 and -2.76 m/s.

Conclusions: Convergent validity between a manual and a mechanical impulse for the calculation of tendon shear wave speed was confirmed.

Implications: The manual impulse could increase the clinical applicability of this device for the measurement of tendon properties or to evaluate the effect of exercise on the Achilles tendon mechanical properties.

Funding acknowledgements: Bianchi-Pandolfi foundation for the financial support of the PhD

Keywords:
Tendon loading
Shear wave tensiometry
Achilles tendon

Topics:
Musculoskeletal: lower limb
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: University of applied science and arts of southern Switzerland (SUPSI)

Committee: Ethics Committee of Canton Ticino

Ethics number: ID:2021–00611/CE3844