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

J Biomech. 2003 Mar;36(3):383-92. doi: 10.1016/s0021-9290(02)00427-x.

Abstract

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.

Publication types

  • Comparative Study
  • Evaluation Study
  • Validation Study

MeSH terms

  • Bone and Bones / physiology
  • Computer Simulation
  • Elasticity
  • Fingers / physiology*
  • Finite Element Analysis
  • Humans
  • Models, Biological*
  • Motion
  • Nonlinear Dynamics
  • Physical Stimulation
  • Pressure
  • Sensitivity and Specificity
  • Skin Physiological Phenomena
  • Stress, Mechanical
  • User-Computer Interface
  • Viscosity
  • Weight-Bearing / physiology*
  • Word Processing