Hand exoprosthesis mechatronic structure and actuation approaches: a systematic review of recent developments and trends.

Hand exoprosthesis are commonly assumed as a promising approach to help people regain independence after upper limb losses. Injury-related data from recent years highlights the need to continue developing solutions to increase end-user acceptance. Within this scope, the present review aims to provide up-to-date information related on advancements and current trends in hand exoprosthesis development. Following a PRISMA methodology, 60 studies were included in this review covering a different range of actuation strategies and design approaches. The main features of the devices developed in the literature are also presented in detail. Concerning actuation strategies, linkage-driven and tendon-pulley mechanisms are the most common approaches presented in the literature, however different strategies such as twisted-string actuators differential mechanisms are also proposed. In turn, pneumatic and hydraulic actuation approaches are also presented as soft alternatives to electric motors. Passive elements such as springs or clutch mechanisms are frequently employed to achieve underactuation in these devices. 3D Printed technologies are also suggested as alternatives to the most conventional manufacturing methods. By covering all these topics, the present review is meant to provide useful insights into future developments in this field. End-user-oriented continuous improvement and the development of highly anthropomorphic solutions are still current challenges, that should be addressed in upcoming developments. This work was developed in the scope of the project 'NerveRepack-Intelligent neural system for bidirectional connection with exoprostheses and exoskeletons', which has received funding from the Horizon Europe RIA programme under grant agreement N∘101112347.