DOES TRANS-RADIAL LONGITUDINAL COMPRESSION INFLUENCE MYOELECTRIC CONTROL?

Abstract

BACKGROUND: Existing trans-radial prosthetic socket designs are not optimised to facilitate reliable myoelectric control. Many socket designs pre-date the introduction of myoelectric devices. However, socket designs featuring improved biomechanical stability, notably longitudinal compression sockets, have emerged in more recent years. Neither the subsequent effects, if any, of stabilising the limb on myoelectric control nor in which arrangement to apply the compression have been reported. METHODOLOGY: Twelve able-bodied participants completed two tasks whilst wearing a longitudinal compression socket simulator in three different configurations: 1) compressed, where the compression strut was placed on top of the muscle of interest, 2) relief, where the compression struts were placed either side of the muscle being recorded and 3) uncompressed, with no external compression. The tasks were 1) a single-channel myoelectric target tracking exercise, followed by 2), a high-intensity grasping task. The wearers’ accuracy during the tracking task, the pressure at opposing sides of the simulator during contractions and the rate at which the limb fatigued were observed. FINDINGS: No significant difference between the tracking-task accuracy scores or rate of fatigue was observed for the different compression configurations. Pressure recordings from the compressed configuration showed that pressure was maintained at opposing sides of the simulator during muscle contractions. CONCLUSION: Longitudinal compression does not inhibit single-channel EMG control, nor improve fatigue performance. Longitudinal compression sockets have the potential to improve the reliability of multi-channel EMG control due to the maintenance of pressure during muscle contractions. Layman's Abstract Most prosthetic limbs are attached to the body using a rigid, cup-like socket shaped to each individual limb. Prosthetic arms attached to a residual forearm are called trans-radial prostheses, and bionic hands and grippers, formally referred to as myoelectric devices, are types of attachments which can be affixed to trans-radial prostheses. The sockets used in conjunction with myoelectric devices today pre-date the clinical introduction of myoelectric devices, and therefore are not optimised to facilitate signal transmission. Newer socket styles have emerged, with the aim of improving comfort and stability, notably those featuring areas of longitudinal compression running parallel to the underlying bone structures. However, longitudinal compression sockets have not been researched for their effects on critical aspects influencing the reliability of myoelectric control. Hence, this study investigates the effect of longitudinal compression on key factors influencing a wearers’ ability to control their myoelectric device. In twelve able-bodied participants, the following three factors were observed: 1) a wearers’ ability to complete a simple on-screen target tracking task whilst wearing a longitudinal compression socket simulator, 2) whether pressure at opposing sides of the socket simulator is maintained during muscle contractions, and 3) whether the longitudinal compression affects the rate at which the forearm fatigues during a short duration, high intensity gripping task. The results from the study showed longitudinal compression of the forearm does not significantly impact a wearers’ ability to complete a simple target-tracking task, or the rate at which the forearm fatigues. However, some benefit to myoelectric control may be achieved due to the maintenance of pressure using this type of socket. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/37963/29734 How To Cite: Olsen J, Day S, Dupan S, Nazarpour K, Dyson M. Does trans-radial longitudinal compression influence myoelectric control? Canadian Prosthetics & Orthotics Journal. 2022; Volume 5, Issue 2, No.2.https://doi.org/10.33137/cpoj.v5i2.37963 Corresponding Author: Jennifer Olsen,Intelligent Sensing Laboratory, School of Engineering, Newcastle University, UK.E-Mail: j.olsen@newcastle.ac.ukORCID ID: https://orcid.org/0000-0001-9076-3092