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Technical Brief

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

[+] Author and Article Information
C.-H. Yeow

School of Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138
Department of Bioengineering,
National University of Singapore,
117575 Singapore

A. T. Baisch

School of Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138

S. G. Talbot

Department of Plastic Surgery,
Hand Surgery and Microsurgery,
Brigham and Women's Hospital,
Boston, MA 02115

C. J. Walsh

School of Engineering and Applied Sciences,
Harvard University, 60 Oxford Street,
Cambridge, MA 02138
Wyss Institute for Biologically Inspired Engineering,
Harvard University,
Cambridge, MA 02138
e-mail: walsh@seas.harvard.edu

1Corresponding author.

Manuscript received November 30, 2012; final manuscript received September 13, 2013; published online December 6, 2013. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 8(1), 014502 (Dec 06, 2013) (7 pages) Paper No: MED-12-1149; doi: 10.1115/1.4025449 History: Received November 30, 2012; Revised September 13, 2013

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.

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Figures

Grahic Jump Location
Fig. 1

Types of therapy exercises performed on the finger or hand during postoperative rehabilitation. The exercises include table top, PIP blocking, straight fist, DIP blocking, hook fist, and fist.

Grahic Jump Location
Fig. 2

Layout of the finger therapy exercise device donned on the index finger of a model hand. The device comprises of phalanx attachment interfaces, connected by cables on the palmar side to spooling actuators. On the dorsal side, the interfaces are linked by extension springs to provide passive return to the finger joints.

Grahic Jump Location
Fig. 3

State diagrams of (a) design 1 (same spring stiffnesses) and (b) design 2 (differential spring stiffnesses)

Grahic Jump Location
Fig. 4

Applied cable force profiles and corresponding joint angle profiles for the DIP, PIP, and MCP joints during execution of (a) table top, (b) straight fist, and (c) fist therapy exercises on the finger therapy exercise device with design 1 (same spring stiffnesses)

Grahic Jump Location
Fig. 5

Applied cable force profiles and corresponding joint angle profiles for the DIP, PIP, and MCP joints during execution of (a) table top, (b) PIP blocking, (c) straight fist, (d) DIP blocking, (e) hook fist, and (f) fist therapy exercises on the finger therapy exercise device with design 2 (differential spring stiffnesses)

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