Journal of Rehabilitation Research & Development (JRRD)

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JRRD Volume 46, Number 8, 2009

Volume 46 Number 8, 2009
   Pages 1011 — 1020

Abstract — Crossed four-bar mechanism for improved prosthetic grasp

Issa A. Ramirez, MS;1 Craig P. Lusk, PhD;1* Rajiv Dubey, PhD;1 M. Jason Highsmith, DPT, CP;2 Murray E. Maitland, PhD, PT3

1Department of Mechanical Engineering and 2School of Physical Therapy and Rehabilitation Sciences, University of South Florida, Tampa, FL; 3Department of Rehabilitation Medicine, University of Washington, Seattle, WA

Abstract — Passive linkages were developed to improve grasp functionality and minimize a prosthetic terminal device's number of user-controlled inputs. The linkages act to stabilize grasped objects and substitute for the palp of normal anatomical fingers. The Southampton Hand Assessment Procedure was used to compare the normal anatomical hand, this prototype, and a commercially available (Hosmer) hook. In testing, prosthetic terminal devices took three times as long as the normal anatomical hand to perform tasks. Nevertheless, heavyweight power and spherical grasps were improved with the use of the new mechanism compared with the commercial hook. Conversely, precision grasps were worsened because of the lack of a high-friction surface on the distal end of the prototype.

Key words: amputation, four-bar mechanism, grasp, hook, polycentric, prehension, prosthetic hand, SHAP, terminal device, upper-limb prosthetics.

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