Biomedical Engineering Reference
In-Depth Information
Table 11.1
Ideal characteristics of a dermal replacement of xenogenic origin
•
Serves as a natural matrix for host granulation, fibroblast proliferation and
neovascularization
•
Lacks antigencity or immune system stimulatory agents
•
Promotes epithelial influx and growth
•
Adheres to the wound bed
•
Lacks any infectious agents that could cross species
•
Fully covers the wound
•
Ability to withstand hypoxia
•
Flexibility
on a clean wound for more than three to four days, they do provide excellent
coverage for second-degree burns, donor sites, and even venous ulcers.
3-5
Reports
from a large series of patients have provided favorable results when the dressings
of porcine acellular dermal matrix were left for seven to ten days.
11
Porcine
dressings provide outstanding analgesia as the wound heals, although because they
are of xenogenic origin, they do not vascularize. Bovine dermis is not employed in
this fashion, though a bovine tendon collagen derivative, Promogram
®
(Johnson
and Johnson, New Jersey, USA) can be used temporarily. This dressing consists of
processed bovine collagen combined with oxidized cellulose.
4
Initially, these derivatives were used fresh, but with the need for immediate use,
technology has allowed them to be lyophilized for preservation and availability.
Because of to antigenicity, certain preparation and treatment variations are em-
ployed, including radiation and conjugation with aldehydes. Aldehyde cross-linking
does not interfere with the structural integrity of the product and, with the addition
of silver ions, allows for increased antimicrobial resistance. These preparations are
employed for temporary wound coverage.
4-9
11.3
Permanent skin substitutes
Porcine dermis, bovine dermis and small intestine submucosa are also employed in
a more permanent fashion. Optimally, these skin substitutes should act like human
dermis (Table 11.1): be adherent to the underlying wound to prevent evaporative
loss and protect against infection, and serve as a matrix to stimulate granulation
and influx of blood vessels and epithelium. In addition, lack of antigenicity is also
desirable, as well as protection against transmission of non-human disease.
4-9
The more permanent products of porcine dermis and its derivatives come in
many forms, conjugated with synthetic and human scaffolds, such as
Transcyte™, Permacol™, and Enduragen™ and others, but the latter two will
be of focus in this chapter. A previous porcine collagen derivative, Zenoderm™,
a product from Ethicon developed and used in the 1980s, is no longer being
produced. Permacol™, from Tissue Science Laboratories in the UK, was devel-
oped in Britain, and has been available since 1998. Variations include
