3. Introduction:
A skin graft is a tissue of epidermis and varying amounts of dermis that
is detached from its own blood supply and placed in a new area of the
body.
Indications:
Replace lost skin, improve the appearance
of damaged skin and restore function
treating deep burns
closing large, open wounds
treating pressure injuries or bed sores or
other ulcers that haven’t healed well.
4. Anatomy of skin Grafts:
Layers of the Skin
Epidermis: Provides protective barrier against
Mechanical damage
Microbe Invasion
Water loss
Dermis: Provides
Mechanical strength (Collagen & elastin)
Sensation (Temp, Pressure, Proprioception)
Thermoregulation (Vessels and Sweat glands).
5. Epidermis:
Outermost layer, Ectodermal origin
Cells undergo continuous differentiation, migration
and eventual shedding.
Average thickness 0.1 mm
(0.05 mm on eyelids, 1mm hands/feet)
Keratinocytes 90-95% of the epidermal cells
remaining including Langerhans cells,
melanocytes and Merkel cells.
Five Layers:
Stratum Corneum
Stratum Lucidum
Stratum Granulosum
Stratum Spinosum
Stratum Basale
6. Dermis:
Mesodermal origin
Comprised of Collagen and Elastin fibres, Ground substance
and deeper portions of epithelial appendages (sweat glands
and pilosebaceous follicles).
Fibroblasts dominant cell type, dermal dendrocytes, mast cells.
Papillary Dermis: thin upper layer, composed of loosely
arranged collagen fibres, contains capillary network that
provides nutrients to epidermis.
Reticular Dermis: Dense irregular Collagen fibres
Contains most of the dermal elastin as well as pilosebaceous units
and sweat glands.
7. Classification:
Split Thickness Skin Graft:
Involving epidermis and part of the dermis.
Range from 0.2 – 0.8 mm
Thin: 0.2 – 0.3 mm
Med: 0.3 – 0.45 mm
Thick: 0.45 – 0.8 mm
Full Thickness Skin Graft:
Composed of epidermis and entire dermis
8. Characteristics:
Type of Graft Advantages Disadvantages Indications
STSG
Large area can be covered
Cosmetic and functionally
poor.
Debrided Burn wounds with
less vascularized wound beds.
Donor sites can be used again once
healed Less durable Exposed Flap areas
Lesser time to heal
Secondary contraction after
healing
Acute well vascularized
wounds
FTSG
Cosmetically and functionally
superior
Limited availability
cannot be used for large
wounds
Reconstruction of functional
areas like face and hand
wounds
More durable Longer healing time
Non-infected well
vascularized wound
Better color match
Difficult post surgical care and
donor site complications
No secondary contraction
Primary Contraction
reduces donor skin size
9. Mechanisms of skin Graft Healing:
Skin Grafts become incorporated into the wound bed by a process
known as Graft Take.
Graft take has been broken down into three phases
1. Imbibition (0 - 48 hours)
2. Inosculation (48 – 72 hours)
3. Revascularization ( > 96 hours)
10. Imbibition:
1st stage of skin graft healing
Plasmatic or serum imbibition
Plasma leaks from recipient capillaries into the
wound bed-graft interface.
Fibrin in the plasma adheres the graft
to the wound bed.
Graft absorbs serum and gains 40% of the
initial weight in 1st 24 hours.
Metabolism in Graft is Anaerobic and pH level
falls reaching 6.8.
Metabolic demands also fall, ATP levels falling
by 70% and glucose by 80%.
11. Inosculation:
2nd stage of Graft healing
Capillary buds from the blood vessels in the recipient bed make contact with
the graft vessels and open channels are formed.
Blood flow is established and the skin graft becomes pink
12. Revascularization:
Three theories have been put forth to explain how a skin graft is revascularized.
1st theory: Circulation is restored in a graft via the original skin graft vessels
by anastomoses formed between the recipient bed and the skin graft
through inosculation.
Definitive vasculature of a graft consists of the blood vessels originally
present within the graft.
2nd Theory: Graft is perfused through new vessels going from
the recipient bed into the transplanted graft.
3rd Theory: Recipient derived endothelial cells migrating into
the graft use the graft’s intrinsic vessels as a conduit for ingrowth
and eventually replace the graft’s endothelial structure.
13. Graft contraction:
Graft Contraction occurs in both STSG and FTSG
Primary Contraction Secondary Contraction
Immediately after Graft Harvest During healing of the graft
Result of recoil of elastin fibres
in the dermis
Myofibroblast mediated
FTSG 40% FTSG -0 %
STSG 20% STSG 40 %
14. Graft Fixation and dressing:
Adherence of skin graft to its bed is essential for skin graft take.
Phase-1
Begins immediately after grafting and lasts for 72 hours.
A thin Fibrin layer holds to the bed.
Phase-2
Onset of fibrovascular ingrowth and vascular anastomosis.
Fixation Methods:
Silicone rubber dressings, silicone gel sheets,
thin hydrocolloid dressings,
tie-over dressings with a bolster,
Negative-pressure dressings (Good option in difficult to bolster
areas like hands and axilla)
15. Choosing a Donor Site:
Selection of Graft donor site is based on
- Whether a FTSG or STSG is required
STSG are commonly taken from lateral thigh to minimize difficulties
during harvest and dressing changes.
Common FTSG sites include inguinal creases, post-auricular region
and supraclavicular area.
- Whether the donor site & recipient site match in color
color match is particularly important in head and neck reconstruction
with skin grafts.
Any skin graft taken below the clavicles and applied above the clavicle
will result in a lifelong color mismatch that is extremely difficult, if not
impossible, to correct.
- Potential morbidity of the donor site
To minimize morbidity from graft harvest, donor sites should be carefully chosen to avoid
hair-bearing skin and to camouflage the resulting scar
16. Graft Sizing:
A simple and reproducible technique consists of placing cardboard in the wound to
develop a blotter pattern.
The cutout is then applied over the donor site, traced with a marking pen, and a graft of
the outlined area is resected.
17. Graft Expansion
With graft expansion, larger areas can be covered with smaller sections of skin
Various techniques have been described.
Pinch Graft: breaks up a whole graft of skin into tiny pieces
to increase the edge area.
Meshing: cutting slits into a sheet graft and stretching it
open prior to transplantation.
- cover a larger area with less morbidity than non-meshed grafts.
- the contour can be adapted to fit in irregular recipient bed
- blood and exudate can drain freely through the interstices of a
meshed graft
- Offers multiple areas of potential reepithelialization.
18. Graft Expansion..
Meek technique: involves a special dermatome and prefolded
gauzes for expanding small pieces of split skin.
The expansion ratio obtained with the Meek technique is almost 1:9
Meek grafts are useful alternatives to meshed grafts
when donor sites are limited, and are particularly
well suited for grafting granulating wounds and
unstable beds
19. Graft Failure:
Causes of Graft Failure
Poor Graft-bed
Contact
Hematoma
Seroma
Inadequate Immobilization of the graft
Poor recipient
bed vascularity
Inadequate vascular bed
Exposed cartilage, tendon or bone
Infection Coagulase +ve staphylococcus
Beta hemolytic streptococcus
Pseudomonas spp
Host factors Diabetes Mellitus
Immunosuppression
Nutritional deficiencies
Systemic conditions with vascular compromise
Technique Rough handling of the tissue
Excessive devitalized tissue in recipient bed due to cautery
Inadequate size causing increased tension
Inadequate hemostasis
Inadequate trimming of the adipose layer.
20. Graft Survival
A meticulous surgical technique contributes greatly to the survival of a skin graft.
Particular attention should be paid to ensuring
atraumatic graft handling
a well-vascularized, scar-free bed
careful hemostasis and removal of accumulated blood before dressing the wound
postoperative immobilization of the graft recipient site
21. Donor site management:
Open wound technique:
Associated with prolonged healing time, more pain and higher risk of complications.
Most authors recommend dressing the donor site of a skin graft to protect it from
trauma and infection.
Dressings:
Ideal donor site dressing encourages rapid reepithelialization, minimizes
pain and decreases risk of infection.
In general dressings that promote moist wound environment until reepithelialization
occurs (at least 7 days), improve rates of healing and pain control.
Multiple options: Alginate (Algisite), semipermeable film (Tegaderm), a gauze dressing,
Hydrocolloid dressing (DuoDerm), a Hydrofibre (Aquacel), a Silicone
dressing (Mepitel).
Choice of dressing continues to be a matter of surgeon’s preference, no strong
evidence directed to any one option.
22. Skin Substitutes:
Substitutes for Skin grafts may be needed -
In patients with extensive burns and limited donor skin areas.
Suboptimal aesthetic and functional outcomes associated with autologous skin grafts.
In 1984, Pruitt and Levine detailed the attributes of an ideal skin substitute:
- Little or no antigenicity
- Lack of toxicity local or systemic
- Permeability to water vapor just like normal skin
- Impenetrability to microorganisms
- Rapid and persistent adherence to wound surface
- Porous for ingrowth of fibrovascular tissue from wound bed
- Malleability to conform to an irregular wound surface
- Structural stability to resist linear and shear stress
- A smooth surface to discourage bacterial proliferation
- Low cost
- Indefinite shelf life
23. Skin substitutes..
Integra: first commercially available skin substitute that is similar to dermal structure.
Consists of two layers
Epidermal layer is composed of silicone membrane which
prevents excessive moisture loss and formation of granulation tissue.
Dermal layer is made of bovine derived collagen type-1 cross-linked matrix
with glycosaminoglycans, which maintains an open pore structure that
allows cell migration into the matrix.
Integra heals in phases similar to skin graft healing, progressing
through Imbibition, fibroblast migration, neovascularization.
New blood vessels reach the superficial surface by day 28, at which
point the silicone layer has usually sloughed and STSG may be applied.
