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Modeling of time-dependent force response of fingertip to dynamic loading.

Wu-JZ; Dong-RG; Smutz-WP; Schopper-AW
J Biomech 2003 Mar; 36(3):383-392
An extended exposure to repeated loading on fingertip has been associated to many vascular, sensorineural, and musculoskeletal disorders in the fingers, such as carpal tunnel syndrome, hand-arm vibration syndrome, and flexor tenosynovitis. A better understanding of the pathomechanics of these sensorineural and vascular diseases in fingers requires a formulation of a biomechanical model of the fingertips and analyses to predict the mechanical responses of the soft tissues to dynamic loading. In the present study, a model based on finite element techniques has been developed to simulate the mechanical responses of the fingertips to dynamic loading. The proposed model is two-dimensional and incorporates the essential anatomical structures of a finger: skin, subcutaneous tissue, bone, and nail. The skin tissue is assumed to be hyperelastic and viscoelastic. The subcutaneous tissue was considered to be a nonlinear, biphasic material composed of a hyperelastic solid and an invicid fluid, while its hydraulic permeability was considered to be deformation dependent. Two series of numerical tests were performed using the proposed finger tip model to: (a) simulate the responses of the fingertip to repeated loading, where the contact plate was assumed to be fixed, and the bone within the fingertip was subjected to a prescribed sinusoidal displacement in vertical direction; (b) simulate the force response of the fingertip in a single keystroke, where the keyboard was composed of a hard plastic keycap, a rigid support block, and a nonlinear spring. The time-dependent behavior of the fingertip under dynamic loading was derived. The model predictions of the time-histories of force response of the fingertip and the phenomenon of fingertip separation from the contacting plate during cyclic loading agree well with the reported experimental observations.
Models; Musculoskeletal-system; Musculoskeletal-system-disorders; Carpal-tunnel-syndrome; Hand-injuries; Arm-injuries; Mechanical-tests; Cardiovascular-system-disorders; Cumulative-trauma-disorders; Cumulative-trauma; Vibration-disease
E&CTB/HELD, National Institute for Occupational Safety and Health, Center for Disease Control and Prevention, 1095 Willowdale Road, Morgantown, WV 26505, USA
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Journal Article
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NIOSH Division
Priority Area
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
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Journal of Biomechanics