Biomedical Engineering Reference
In-Depth Information
advanced wound care treatments have been slow to develop. It is only now,
through our growing understanding of the intrinsic ability of human tissue to heal
itself via a regenerative pathway, that RTMs have been developed to address the
need for more clinically promising wound treatments. RTMs are currently garner-
ing increased clinical acceptance as advanced wound care materials through their
ability to support restoration of the structure, function and physiology of damaged
tissue previously unattainable through other wound treatments (Harper and
McQuillan, 2007).
10.1.2 Solutions
Permanent closure of large full-thickness wounds has historically been accom-
plished through application of an autologous split thickness skin graft (STSG)
from a non-wounded area. The amount of dermis included as part of the graft
inversely correlates with the level of scarring and contracture observed in the
healed wound (Dunkin
et al
., 2007; Klein and Rudolph, 1972). This response
probably results from the presence of myofibroblasts in the wound bed which
induce a significantly stronger contractile response than do typical dermal fibroblasts
(Germain
et al
., 1994). The effect of dermal thickness on healing characteristics
applies to the donor site as well. Thus, a balance must be achieved between
providing enough dermis with the graft and leaving enough in the donor site so that
both sites can heal and provide the functional and aesthetic outcomes desired by
the patient. For very large wounds, the STSG can be meshed to expand graft
coverage and minimize the size of the donor site. However, meshed grafts have a
tendency to impart a meshed pattern to the treated wound. Nevertheless, despite
efforts to minimize additional trauma during the autograft procedure, the limiting
factor to this approach has remained the availability of a viable dermis. One
potential source of additional dermis has been allograft skin. Such grafts integrate
well with the wound bed and minimize dehydration, but are eventually rejected
owing to the presence of foreign cellular antigens. Thus, the role of allogeneic skin
grafts has been limited to temporary coverings.
The explosion in biotechnology over the past three decades has provided
scientists with new tools and the ability to purify or synthesize many biological
building blocks. Medical science has thus turned to tissue engineering (TE) to
address the limitations of auto- and allograft skin. While TE is customarily defined
as the application of engineering and life science principles in the development of
biological substitutes to restore, maintain, or improve function, it is not, however,
necessarily equivalent to the regenerative medicine concept, which requires
restoration of native structure and physiology. By employing combinations of the
traditional TE triad of cells, matrix molecules and biochemical factors, a variety of
dermal constructs and engineered skin substitutes have been developed and now
are commercially available. These devices, their approved uses, benefits and
limitations are reviewed elsewhere (Bello
et al.
, 2001; Clark
et al.
, 2007; Simpson,
