Three-dimensional finite element simulations of the dynamic response of a fingertip to vibration.

Although excessive dynamic deformation of the soft tissues in the fingertip under vibration loading is thought to induce hand-arm vibration syndrome, the in vivo distributions of the dynamic stress/strain of the tissues in the fingertip under vibration conditions have not been studied because they cannot be measured experimentally. In the present study, we analyzed the dynamic responses of a fingertip to vibrations by extending our previously proposed three-dimensional finite element (FE) model. The FE model of the fingertip contains the essential anatomical structures of a finger, such as skin layers (dermis and epidermis), subcutaneous tissue, bone, and nail. Our analysis indicated that the fingertip has a major local resonance around 100 Hz and that the vibration displacement in the soft tissues under the nail bed is less than 10% of those in the finger pad for all precompression levels and vibration range. The resonant frequency of the fingertip was found to increase from 88 Hz to 125 Hz with the static precompression increasing from 0.5 mm to 2.0 mm. These results suggest that structural and functional changes in vascular function will likely initiate from the fingerpad, the location that undergoes the greatest deformation during vibration exposure. The current predictions are qualitatively consistent with the physiological data collected from workers with vibration white finger.