A wireless buckle transducer for measurement of human forearm tendon tension: operational principles and finite element study

Introduction: Conventional methods for evaluating the management of spasticity, a complex neuromuscular disorder, typically fail to directly measure the muscle forces and loads applied through tendons, which is crucial for accurate diagnostics and treatment. To bridge this gap, we developed a novel modular buckle transducer (BT) designed to measure tendon forces in vivo. This device adjusts to accommodate tendon sizes ranging from 3 mm to 5 mm, maintaining accuracy within this range and avoiding the need for identical tendon calibration.

Methods: This study first presents the mechanical principles for determining tendon tension T using several strain gauges appropriately positioned to allow for varying angles of passage of the tendon through the device. Next, we present a finite element (FE) model that uses multiple linear regression to determine T while varying tendon diameter and lateral placement within the device for several candidate strain gauge locations on the device base plate. Finally, we posit several alternative ways of combining gauge strains.

Results: Initial simulation results demonstrated that this placement facilitates effective pre-implementation calibration, with the device accommodating tendon variations from 3 mm to 5 mm in diameter for a range of gauge placements.

Discussion: Future validation of this technology will involve direct testing on explanted human/equine tendons to verify the practical utility of the BT, aiming to establish a new standard for assessing and managing neuromuscular disorders such as spasticity.