Biomedical Engineering Reference
In-Depth Information
shape). The VAC device properties were captured in our model by varying both
strut thickness (values of 0.15, 0.3, 0.5 mm), and strut lumen or pore diameter (0.8,
1.2, 1.6 mm) as well as the sub-atmospheric pressure applied by this device (70,
110 and 150 mmHg below atmospheric pressure).
Our results showed that the average surface strains under the application of the
VAC were on the order of 20%.
5
These strains rose as expected with increased
negative suction pressure (higher and higher negative values) and with pore size,
while they decreased with strut thickness.
3.6 Forces on cells
In our paper discussing the finite element model, we proposed that wound healing
was accelerated through the transmission of forces from the external environment
onto the cells residing within the wounded tissue. It has previously been shown that
cells that are allowed to stretch tend to proliferate whereas those cells that obtain a
spherical conformation and are not allowed to stretch become cell cycle arrested and
apoptotic.
6,7
Thus, an understanding of the mechanics of skin and its microstructure
can help us understand what types of forces may be being transmitted into the cells.
3.7 Conclusion
An understanding of skin mechanics is critical for the design of medical devices
that find application in wound healing in the skin. It is also critical in understanding
how cells and the extracellular makeup of tissues perceive and transmit those
forces. The skin is far from a mechanical scaffold that serves a passive role. It
responds actively to forces by transmitting force information on to its cellular
components, which then secrete various growth factors, cytokines and so on in
response to the mechanical stimuli the tissue perceives from the environment
through signal transduction pathways.
3.8 References
1 Orgill DP.
The Effects of an Artificial Skin on Scarring and Contraction in Open Wounds
.
PhD Thesis, Harvard University - MIT Division of Health Sciences and Technology.
Program in Medical Engineering and Medical Physics. 1983, 214 pp.
2 Mader S.
Understanding Human Anatomy and Physiology
. 5th edition, McGraw-Hill,
New York, 2004.
3 Scanlon VC and Sanders T.
Essentials of Anatomy and Physiology
. 5th edition, F.A.
Davis Co, Philadelphia, 2006.
4 Kumar V, Fausto N and Abbas A.
Robbins and Cotran Pathologic Basis of Disease
. 7th
edition, Elsevier Saunders, Philadelphia, 2005, Volume xv, 1525.
5 Saxena V, Hwang CW, Huang S, Eichbaum Q, Ingber D and Orgill D. 'Vacuum-assisted
closure: microdeformations of wounds and cell proliferation'
.
Plast Reconstr Surg
,
2004,
114
(5), 1086-96; discussion 1097-8.
