Cable-Driven Finger Exercise Device With Extension Return Springs for Recreating Standard Therapy Exercises

Abstract

Finger therapy exercises, which include table top, proximal-interphalangeal blocking, straight fist, distal-interphalangeal blocking, hook-fist, and fist exercises, are important for maintaining hand mobility and preventing development of tendon adhesions in postoperative hand-injury patients. Continuous passive motion devices act as an adjunct to the therapist in performing therapy exercises on patients; however, current devices are unable to recreate these exercises well. The current study aimed to design and evaluate a finger exercise device that reproduces the therapy exercises by adopting a cable-actuated flexion and spring-return extension mechanism. The device comprises of phalanx interface attachments, connected by palmar-side cables to spooling actuators and linked by dorsal-side extension springs to provide passive return. Two designs were tested whereby the springs had similar (design 1) or different stiffnesses (design 2). The device was donned onto a model hand and actuated into the desired therapy postures. Our findings indicated that design 1 was able to recreate table top, straight fist, and fist exercises while design 2 was capable of further replicating distal-interphalangeal blocking, proximal-interphalangeal blocking, and hook-fist exercises. This work demonstrated the possibility of replicating finger therapy exercises using a cable-actuated flexion and spring-return extension design, which lays the groundwork for prospective finger exercise devices that can be donned on patients to assess the efficacy in postoperative joint rehabilitation.