A Multiscale Approach for Predicting Certain Effects of Hand-Transmitted Vibration on Finger Arteries

Abstract

Prolonged exposure to strong hand-arm vibrations can lead to vascular disorders such as Vibration White Finger (VWF). We modeled the onset of this peripheral vascular disease in two steps. The first consists in assessing the reduction in shearing forces exerted by the blood on the walls of the arteries (Wall Shear Stress—WSS) during exposure to vibrations. An acute but repeated reduction in WSS can lead to arterial stenosis characteristic of VWF. The second step is devoted to using a numerical mechano-biological model to predict this stenosis as a function of WSS. WSS is reduced by a factor of 3 during exposure to vibration of 40 m·s−2. This reduction is independent of the frequency of excitation between 31 Hz and 400 Hz. WSS decreases logarithmically when the amplitude of the vibration increases. The mechano-biological model simulated arterial stenosis of 30% for an employee exposed for 4 h a day for 10 years. This model also highlighted the chronic accumulation of matrix metalloproteinase 2. By considering daily exposure and the vibratory level, we can calculate the degree of stenosis, thus that of the disease for chronic exposure to vibrations.

Factoring Muscle Activation and Anisotropy in Modelling Hand-Transmitted Vibrations: A Preliminary Study

“…Our FE hand model was built by segmenting MRI images of the hand of a 28-year-old male volunteer [5]. Most of the hand anatomical elements were included and meshed with tetrahedrons of around 1 mm (Figure 1b).…”

“…The calculations were performed using the FE software LS-Dyna ® (Ansys, Canonsburg, PA, USA) by assuming linear elastic constitutive laws. The parameters were derived from [5], except those for the muscles, which were derived from elastography measurements. Three cases were computed: (i) isotropic elastic with no activation, where Young's modulus (E L ) was derived from the longitudinal elastic shear modulus (µ L ) measured at 0-5% gripping force (contact without tightening condition) and the longitudinal Poisson's ratio (υ L ) was derived from [7]; (ii) isotropic elastic with maximum activation, conducted in the same way as the previous case but at 30% gripping force; and (iii) transversally isotropic elastic with maximum activation, where the muscle behaviour was considered to be anisotropic, with rotational symmetry around the fibre axis.…”

Arterial Stenosis Stemming from Vibration-Altered Wall Shear Stress: A Way to Prevent Vibration-Induced Vascular Risk?

“…Many physiological, histological, and epidemiological studies [1] have highlighted that the vibration dose assessed according to the current ISO 5349 standard may underestimate the onset predictions of such vascular injuries. In order to better tackle vibration-induced pathophysiological vascular issues, we recently set up a strategy in a two-step process [2]. First, we hypothesized that vibrations may acutely decrease the shear stress exerted by the blood flow on the artery endothelium layer.…”