Biomedical Engineering Reference
Fig. 1.1 Systems for body support design and testing: a abstracted pelvis, b physical dummy
made from technical materials, c system for shear force evaluation of the human skin*, d dummy
employed in mattress testing, e pressure-sensor mat for shoes and for f seating systems (*adopted
from the draft supplement of the catalogue of therapeutic appliances ''product group
11-decubitus'' of the medical review board of the head organisations of health insurance
carriers (MDS)-sector ''therapeutic appliances'')
process and stress distribution (three direct and three shear stress components at
each material point) at skin level and inside human tissue.
Various questionable systems are employed for shear force evaluation of human
skin (cf. Fig. 1.1 ), which at closer look and due to the employed materials and test
scenarios, have little in common with the actual interaction between material and skin.
To date, it has not been possible to judge the effects of therapeutic appliances
on (deeper) tissue regions. It has also not been possible to objectively evaluate the
complex (internal) tissue stress distribution due to external skin loading in the form
of compressive, tensile and shear stress. Shear stress is a prominent factor in
pressure sore development.
These shortcomings were the impetus for my co-author, Christophe Then, then
working in the field of finite element analysis, to place a virtual human model
(multi body system with rudimentary elastic outer-surface material properties and
mainly used for safety analysis in automotive engineering) on a bedding system
from the T HOMASHILFEN company. Stress occurring in the mattress was then
observed, cf. Fig. 1.2 .
At that time, simulations of dummy-car interaction in highly dynamic crash
scenarios were common practice. Though our test situation was much more
passive, it was possible to take a first step towards the goal of objectively
evaluating tissue and support material stress and strain. It became clear that better
understanding of mechanical interaction simulations between human dummies
and body supports would entail an adequate human body model with realistic
anatomical structures and realistic tissue material properties.
Within the next 5 years, in cooperation with physicians, health care profes-
sionals and biologists, a new and objective approach based on engineering-