Brief Anatomy of Skin and Skin Grafting. Anatomy of Skin History of skin grafting. Recent Advances in Skin Grafting. Dermal Substitutes. Cell cultures in skin grafting.

1. Anatomy of
Skin and
Skin-Grafting
Dr. Rishi Kumar Gupta
M.Ch Resident
Department of Plastic and Reconstructive Surgery
Gauhati Medical College

2. One of the greatest advances in 19th-century surgery was the
demonstration that a piece of skin, fully separated from its original site,
might survive when transplanted to another part of the body to cover a
granulating raw surface.

3. • This became possible through the
pioneering work of Giuseppe
Baronio (1758–1811) from Milan,
who performed the first autologous
skin graft in a ram in 1804.
• Sixty-five years later Jacques
Reverdin (1842–1929) carried out
the first successful epidermic graft
on a human being at Hôpital Necker
in Paris, opening a new era in
wound-healing management.

4. • The route for skin grafting was traced. A few years later, Louis Ollier
(1830–1900) transferred a large piece of split-thickness skin, which
included the superficial layers and underlying dermis.
• Carl Thiersch (1822–1895) and John R Wolfe (1824–1904) made
further advances in the procedure.
• In the late 1800s, skin grafting became the preferred solution for the
management of chronic and granulating wounds.

5. INTRODUCTION
• Skin grafting is a technique for the transfer of cutaneous tissue from
one site of the body to another, often to cover large defects.
• Depending on the thickness of the dermis of graft that is harvested,
skin grafts are defined as full-thickness or split-thickness.

6. ANATOMY AND PHYSIOLOGY
• The skin represents approximately 8% of our total body weight, with a
surface area of 1.2–2.2 m2.
• The skin is 0.5–4.0 mm thick and covers the entire external surface of the
body.
• The main function of skin is to:
• Protect body contents from the environment, including pathogens
• Maintain temperature
• Prevent excessive water loss
• Insulation
• Sensation,
• Immune function
• Synthesis of vitamin D

7. • Skin loses regenerative capacity when lesioned down to the lower
dermis  results in scar tissue when injured.

8. • Skin has a complex three-dimensional structure characterized by two
overlapping layers, the epidermis and the dermis.
• The epidermis, as the nervous system, derives after gastrulation from
the neuroectoderm.
• Epidermis is the outer or upper layer of skin, which is a thin,
semitransparent, water-impermeable tissue, consisting primarily of
keratinocytes. These cells form a multilayered keratinized epithelium,
similar to a wall of bricks.

9. SKIN ORIGINS

10. EMBRYONIC
DEVELOPMENT

11. ANATOMY OF SKIN

13. • The basement membrane separates the epidermis from the dermal
tissue and consists of a protein structure produced by basal
keratinocytes.
• Basal keratinocytes are partially differentiated stem cells of the
epidermis that provide the proliferative and regenerative capacity of
the skin epithelium.
• The epithelium is metabolically active and continuously self-renews to
maintain an efficient barrier function.

14. • Cellular homeostatic regulation is, as a consequence, very important:
too little proliferation would bring a loss of barrier and excessive
activity to hyperproliferative disorders, such as psoriasis.
• Homeostasis is granted by the basal epidermal cells, which periodically
cycle, executing their program of terminal differentiation, a process
that takes approximately 28 days.

15. • The differentiation of the keratinocytes
is characterized by the progressive
production of alpha-keratin, with
migration towards the surface until the
cells lose their intercellular connections
(desmosomes), die, and become corneal
lamina.
• During this process, called
“Cornification”, basal keratinocytes
produce tonofilaments (precursor of
keratin) and then transform into the
stratum spinosum as the desmosomes
stretch the cells into spikes visible with a
microscope.

16. • Cells next start to produce Keratohyalin, which aggregates in dense
and basophilic granules, giving the name to the stratum granulosum.
• In these granules a histidine-rich protein, profilaggrin, becomes
progressively filaggrin, which ultimately acts as a glue to keep keratin
filaments together once the cells die and the cell membrane degrades.
• As the cells divide and move up through the epidermis  eventually
transform into the stratum corneum  a layer of dead cells, which
ultimately is highly mechanically and chemically resistant due to
chemical bonds between lipids and proteins.

17. • Also contained within the epidermis are melanocytes, Langerhans
cells, Merkel cells, and sensitive nerves.
• Melanocytes:
• 10% of the epidermal
• Derived from the neural crest.
• Produce melanin granules (contained in the melanosomes)
• Providing color to the skin and protecting basal epithelial nuclei from ultraviolet damage.
• They are anchored to the basal lamina by hemidesmosomes, but do not have
desmosomic connections with other cells.

19. • Langerhans cells:
• Situated in the Stratum spinosum
• Immune cells  Antigen presenting cells.
• Playing an important role in allograft rejection and contact dermatitis.
• Merkel cells:
• Reside in the Basal layer
• Are commonly found in the epidermis of palms, soles, nail beds, oral and
genital areas.
• They act as mechanoreceptors and thus are responsible for neurosensory
transmission.

21. • Skin adnexal structures:
• Epidermal derivatives that invaginate into the dermis with a lining of epithelial
cells.
• Eg: Hair follicles, sweat and sebaceous glands.
• These structures provide the basis for re-epithelialization following the harvest
of an STSG.
• Sensitive nerve supply to the skin is rich and extends through the
basement membrane into the epidermis.
• Nerve fibers also go to skin adnexal organs that allow hair to become
erect and sweat glands to secrete.

22. DERMIS
• The dermis is a tough fibrous layer that provides the mechanical
features of the skin.
• It is composed primarily of collagens, glycosaminoglycans, and elastins.
• Skin grafts without the dermis result often unstable skin.
• Grafting a part of the dermis is therefore very important to consider in
terms of functionality of the future skin.

23. • Papillary dermis:
• Upper part of the dermis
• Contains blood vessels and nerve fibres.
• Consists of fine collagenous fibres that form an undulating interface with the
overlying basement membrane and epidermis.
• This increases the contact area between dermis and epidermis 
• For maximal mechanical stability of the two layers
• Exchange surface for diffusion.

24. • Reticular Dermis:
• Deeper
• Increasingly thicker collagenous fibers (mainly of type I) as we move toward
the subcutaneous tissue.
• It has larger collagenous fibers with substantial strength.
• The mechanical properties of the dermis are
• Critical to allow movement while providing stability and protection from mechanical
trauma.
• The dermis is remarkably self-healing, mainly due to the presence and
activation of myofibroblasts following injury.

25. BLOOD SUPPLY TO THE SKIN
• Dermal vascularisation is particularly important, as
blood vessels are not directly present in the
relatively more metabolically active epidermal layer,
glands, and hair follicles.
• Blood vessels set up a rich superficial plexus just
underneath the basement membrane in the
papillary dermis, facilitating nutrient transport to
the epidermis.
• The blood vessels in the papillary dermis are
arranged in the papillary plexus, with a rich network
of capillaries in the papillae, which come in close
contact with the epidermis.

26. • Deeper in the dermis is the
reticular plexus from which small
vessels distribute to the
subcutaneous and deep dermal
tissues to vascularize adnexal
organs, including the hair follicle
bulb.
• Blind-ended lymphatic structures
are present in the dermis from
where they connect to the
reticular plexus and to larger
vessels in the subcutaneous
tissue.

27. • In this Subcutaneous region, lymphatic vessels are larger, with valves,
and drain in deeper lymphatic vessels called regional collectors.
• In the skin the lymphatic drainage is very active with multiple
interconnections enabling lymphatic exchange.
• Circular skin and subcutaneous damage can therefore lead to
problematic lymphatic stasis in extremities or in the genital area.

28. STEM CELLS AND REGENERATION OF SKIN
• Basal epithelial keratinocytes are the committed stem cells of the
epidermis. Constant self-renewal provides a new protective layer at
the skin surface.
• Hair follicles contain multipotent stem cells that are activated upon the
start of a new hair cycle and upon wounding to provide cells for hair
follicle and epidermal regeneration.
• In the hair follicle stem cells reside in the bulge area. Bulge cells are
relatively quiescent compared with other cells within the follicle.

29. • However, during the hair cycle, bulge
cells are stimulated to exit the stem
cell niche, proliferate, and
differentiate to form the various cell
types of the hair follicle.
• Clinical Significance:
• Bulge cells can be recruited
during wound healing to support
re-epithelialization.

30. GLANDULAR STRUCTURES
• Sebaceous glands are small saccular structures residing throughout
the dermis but are more common in thicker areas.
• These glands produce lipid-rich sebum on the surface of the skin and
around the hair shaft.
• Sebaceous glands are particularly large on the face, trunk, shoulders,
and genital and perianal regions.

31. • Sweat glands are divided into eccrine and apocrine glands.
• There are numerous eccrine glands in every region of the body except
the tympanic membranes, lips, nail bed, nipples and clitoris.

32. SCIENCE

33. MECHANISMS OF SKIN GRAFT TAKE
• Skin grafting is the transfer of autologous skin cells left in anatomic order but
without an intact blood supply.
• Therefore, time and the recipient surrounding conditions limit the vitality. The
operative procedure allows for nearly immediate coverage of large wound areas.
• Meshed grafts allow further expansion of skin but leave multiple small wounds
that are re-epithelialized, mainly from the mesh within a few days.
• Skin can also be expanded through multiple small skin island grafts (as in
Reverdin’s technique) that stimulate granulation tissue, probably by excreting
growth factors.
• In STSGs, keratinocytes on the basal layer show high proliferation rates, which may
ultimately stimulate growth factor excretion.

34. • Three phases of skin graft
take are commonly
described:
1. Serum imbibition;
2. Revascularization;
3. Maturation

35. SERUM IMBIBITION
• In the first days, before the graft revascularizes, oxygen and nutrients
diffusing through the plasma between the graft and the wound bed
will nourish the skin graft.
• Huebscher in 1888 and Goldmann in 1894 theorized that skin grafts
might be nourished by host fluid before vascularization of the graft
occurs. They referred to this as “plasmatic circulation.”

36. • Later, Converse et al. altered the term to “serum imbibition,” as fibrinogen
changes into fibrin that fixes the skin graft on to the wound bed in the
absence of real plasmatic flow.
• Converse’s studies show that skin grafts gain up to 40% of their initial weight
within the first 24 hours after grafting and then this gain is reduced to 5% at
1-week post grafting.
• In the first hours, passive absorption of serum from the wound bed causes
oedema, which resolves when the revascularization is functional.

37. REVASCULARIZATION
• Revascularization is critical for long-term skin graft survival.
• Early studies in the 19th century suggested a connection between the
wound bed and graft vessels, referred to as inosculation, but the
mechanism of revascularization remained unclear for many years.
• Three hypotheses of revascularization are supported by the literature,
each of them probably contributing to the process:
1. Anastomosis,
2. Neovascularization
3. Endothelial cell ingrowth

38. • Anastomosis: The process of reconnection between the blood vessels
in the recipient site wound bed and the graft.
• Neovascularization: It is characterized by new vessel ingrowth from the
recipient site into the skin graft.
• Endothelial cell ingrowth: It describes endothelial cell proliferation 
sliding from the recipient site, utilizing pre-existing vascular basal
lamina as a structure, while in the graft endothelial cells gradually
degenerate.

39. • The process of revascularization begins as early as 24–48 hours after
grafting.
• There is vessel ingrowth mainly from the wound bed and less so from the
wound margins, since no significant increase in blood vessels was seen in
graft margins after skin grafting.
• Studies by intravenous injection with radioisotopes that blood flow in the
graft was established 4 days after grafting.
• Similarly, studies using India ink showed graft vessel stain as early as 2 days
postgrafting.

41. MATURATION
• Once the skin graft is completely integrated, the same graft and
surrounding tissues remodel and contract, similar to the last phase of
wound healing after re-epithelialization is complete.
• Skin grafts take at least 1 year to complete maturation, with the
extension of this process continuing for several years in burn victims
and children.
• Scars from skin grafts can continue to improve for a number of years,
often making prolonged conservative therapy worth considering.

42. • Skin graft vascularization contributes to prevent underlying tissue
contraction.
• Fibroblasts from surrounding tissues and from blood circulation
become activated and repopulate the wound at the interface between
the graft and the recipient site.
• As collagen is deposited, cross-linking allows the extracellular matrix to
resist mechanical insults.

43. • During wound maturation, the epithelium from the edges of the
wound  produces a basal lamina on the open surface while sliding
across  progressively covering the immature granulation tissue.
• During the re-modeling phase, all immature blood vessels necessary to
support the initial phases regress and eventually disappear.
• The re-modeling phase of wound healing is the longest, lasting from
several months up to years.

44. SKIN APPENDAGES AND FUNCTIONAL
STRUCTURES
• Hair follicles, sweat glands, and dermal nerves can often be transferred
within thick-STSGs and full thickness skin grafts.
• Thin STSGs will not allow the transfer of hair or other adnexal glands,
as the regenerating bulb is not harvested.
• Hair regrowth can occur in STSGs but, due to the shallow depth of
harvest, is rather unlikely. Full-thickness and composite grafts will
show hair regrowth 2–3 months after grafting.

45. • It is still unclear how nerves regrow into the skin graft. Studies
demonstrated that recipient nerves use the basal lamina infrastructure of
degenerated blood vessels and Schwann cells of donor nerves to grow.
• Although histological images reveal similar neural structures between
healthy skin and integrated skin grafts, patients report abnormal sensation,
including hypersensitivity and pain, up to 1 year.
• Usually, patients regain sensitivity of the grafted area after 1 year, but the
result is not completely normal.

46. • Neural reconnection to sweat glands will reactivate their function up
to 3 months after grafting.
• For this reason, moisturizing of the skin graft is advised for at least 3
months to avoid dryness.
• Full-thickness skin grafts include skin appendages that can survive and
be functional at the recipient side, while STSGs do not contain the
deep structure skin appendages and remain without glandular
function or hair growth.

47. CLINICAL APPLICATION
• Skin wounds that extend into the deep dermis heal through the
mechanisms of scarring and wound contraction.
• Also, wounds that are left open for months to years can degenerate
into skin cancer (Marjolin’s ulcer).
• For these reasons, methods that rapidly facilitate wound coverage or
resurfacing are desired.

48. • Skin grafting is still the gold standard
to cover large areas of skin loss.
• The concept is to take skin from an
area where the donor site will heal
with minimal scarring and transplant
it to an area of need.
• As skin grafting always leaves some
sort of scar, donor site considerations
are important when balancing the
needs of the recipient site for a given
skin graft.

49. • Skin grafts can be:
• Of different origin from different anatomical sites
• Can be harvested in different thicknesses
• Depending on the histological level of the graft the skin graft type is
classified by:
• Thin and thick STSGs,
• Full-thickness skin grafts
• Composite grafts

50. Thickness in mm Name
Thin 0.15–0.3 Thiersch–Ollier
Intermediate 0.3–0.45 Blair–Brown
Thick 0.45–0.6 Padgett
Full Thickness >0.6 Wolfe–Kraus
Skin grafts are further classified according to their thickness into:

53. SPLIT-THICKNESS SKIN GRAFT

55. • The thickness of the dermal layer classifies the STSG as either thin or
thick.
• An STSG consists of epidermis and a variable amount of superficial to
profound (papillary) dermis.
• As the dermis is responsible for the viscoelastic property of the skin, it
is crucial for stability of the future skin.
• The amount of dermis grafted is key to the outcome: body areas with
high mechanical friction are ideally grafted with thicker dermal layers.

56. • Thin STSGs include the epidermis and a thin layer of the dermis.
• STSGs are commonly taken from the lateral thighs and trunk.
• They do not include the full length of appendages and are therefore unlikely
to grow hair or to develop full sweat gland function.
• Advantage of thin STSGs:
• Reduced morbidity of the donor site
• Possibility of performing multiple harvests from the same donor area about 2 weeks
after the previous harvest.
• Although thinner grafts allow for more frequent re-harvest, they result in
additional wound contraction.

58. • Thick STSGs include more dermis with a greater number of full hair follicles
and glandular structures.
• These grafts will likely develop some hair growth and sweat gland function
about 2–3 months after grafting.
• Thick STSGs are commonly selected to cover areas of high mechanical
friction, such as joints, plantar soles, and the palm.
• Since hair regrowth is common in thick STSGs, the donor site should be
carefully chosen to avoid unpleasant hair growth.

59. • Because of decreased nutrient diffusion, thick grafts require a better
recipient wound than thin grafts during the revascularization process.
• Therefore, thick grafts should be avoided in unhealthy wound beds
such as in chronic ulcers.
• The donor site usually heals with more obvious scarring and
discoloration but less graft contraction.

61. • To increase the uniformity and expedite the
harvest of skin grafts, a number of electrical or
air-powered dermatomes have been designed
to take uniform small to large skin grafts.
• Powered dermatomes have adjustable guards to
set the graft thickness.
• Drum dermatomes are precision instruments
that can take large graft areas reliably.
• They require placement of adhesive on the skin
and an oscillatory movement by the operator.

62. • When possible, harvesting the skin graft first and covering the donor
site will avoid contamination from the wound.
• The size of the graft needed should be accurately measured prior to
harvest. The graft thickness can be adjusted by a lever near the end of
the dermatome between 0.1 and 1.0 mm.
• The surgeon presses the dermatome in 45°to the skin surface on to
the tissue and moves the device from distal to proximal with uniform
pressure and speed.

63. • Keeping the graft moist with saline-impregnated gauze is of vital
importance if not immediately grafted.
• Larger skin grafts should be incised with an 11 knife multiple times to
allow wound fluid drainage and prevent collections between the skin
graft and the wound bed.

64. MESHED SKIN GRAFT
• STSGs can be enlarged up to six times their original size.
• Enlargement of the graft can vary from just a few manually applied
perforations with an 11 blade to a systematic enlargement with a hand-
powered meshing device (Mesher) that applies multiple slits at regular
intervals
• Meshed grafts are often used following large burns when the wound
area exceeds available healthy donor sites.

65. • Meshed skin grafts are also very helpful to cover irregular geometric
surfaces such as around joints as they minimize folds in the graft.
• Development of contractures should be taken into consideration in
functional areas.
• Using different mesh templates, from 1 : 1 to 1 : 9, can regulate the extent
of the enlargement of meshed grafts.
• The most commonly used mesh ratio is 1 : 1.5 in smaller wounds, while a
mesh ratio of 1 : 3 and 1 : 6 is often needed to cover large burns.

67. • The mesh gaps will be subsequently filled
by keratinocytes from the skin stripes.
• This process takes longer with higher
mesh expansion ratios.
• Since grafted cells excrete growth
factors, underlying granulation tissue will
be stimulated until full re-
epithelialization occurs.
• Aesthetically unpleasant
hypergranulation in the open areas of
the mesh are therefore more often seen
in large mesh ratios.

68. • Meshed skin grafts leave
unsightly long-term results
that need to be considered
when selecting this
technique.
• Very thin meshed skin
grafts used in combination
with dermal substitutes or
keratinocyte cultures are
other strategies to mitigate
the result.

69. FULL-THICKNESS SKIN GRAFT
• Full-thickness skin and composite grafts are limited in availability but
show excellent function and sensitivity after engraftment.
• Full-thickness grafts should be considered in the reconstruction of
aesthetically dominant (face) or functionally important areas (hand).
•
• Full-thickness grafts from the retro-auricular region and above the
eyebrows are an excellent choice to maintain tissue quality and colour
of the surrounding skin in the face.

71. • If needed, foreskin can also be used and in adults' retro-auricular skin is
helpful in face reconstruction.
• Also, excess skin from the upper eyelid and submental area can be taken
into consideration for full-thickness reconstruction if the patient is
comfortable with an aesthetic-like intervention.
• In hand reconstruction, elbow crease and wrist fold grafts have been
described but should be avoided in cultures where these donor site scars
may result in stigmatization of the patient as they can be associated with
suicide.

72. • Hypothenar skin is useful for glabrous
reconstruction but can leave a painful
scar that can cause an unpleasant
sensation if the hand is positioned on
a table in a relaxed position.
• Therefore, full-thickness skin graft
from the hypothenar area should be
harvested elliptical with the main axis
and slightly more dorsal in relation to
the glabrous–skin border.

73. • Full-thickness skin grafts are taken in an area where loose surrounding
skin is available to achieve primary closure.
• Skin grafts can be designed elliptical and excised with a knife.
• Harvesting should be carried out trying not to elevate the underlying
tissue.
• Most of the fullthickness grafts need defatting and this can be easily
performed by spreading the graft over the index finger and trimming
the fat tissue tangentially to the skin.
• Defatting of the graft will encourage graft take.

75. COMPOSITE GRAFT
• Composite grafts include a layer of subcutaneous fat tissue under the
dermal and epidermal layer.
• The donor sites are principally the same as the full-thickness donor
sites.
• Since fat tissue is less vascularized and more vulnerable to ischemia,
optimal revascularization is needed in order to achieve graft survival.
• Composite grafts can be used in children as they show a remarkable
capacity to revascularize thicker grafts.
• Some surgeons use composite grafts to reconstruct the nasal tip, the
alar, and the columella in cleft lip patients.

76. SKIN FIXATION AND DRESSING
• Once the autologous skin is grafted on to the wound site the
revascularization depends on multiple factors.
• One of the most important factors to achieve stable taking is the
immobility of the graft during the revascularization process.
• An “Open-technique” requires labor-intensive monitoring on the graft
and any fluid that is formed beneath the graft is rolled out with a
cotton-tipped applicator.
• More often, skin grafts are fixed through a series of sutures and
overlying compressive dressing materials (Bolster).

78. • Vacuum-assisted pressure devices can be used with a protective
interface of petroleum gauze or a silicone sheet to permit continuous
compression on to the graft and fluid removal.
• The suction dressing is especially useful if fast mobilization is desired in
patients with wounds in joint regions or the lower extremities.
• Compression to stabilize the graft on to the wound bed should be
performed until 5–10 days when the graft is usually stable and wound
areas are completely closed.

79. • Splints can be used as adjuncts if the risk of wound contraction is high,
such as in chin scar release or in joint and web space release of the
hand.
• These splints or casts should be worn up to several months after
grafting, in the beginning 24 hours per day, later during the night, to
avoid the loss of mobility.
• Physiotherapy and scar massage are also important elements for
obtaining better results with skin grafts.

80. SEALANTS
• Fibrin glue can also be helpful to
assist skin graft fixation.
• In this case, some surgeons
spray fibrin glue on to the skin
graft dermis just before placing
it on to the wound site. The
fibrin network may even act as a
provisory extracellular matrix
under the graft.

81. FIRST DRESSING CHANGE
• The first dressing change should occur  once the skin graft is
revascularized and has a stable physical connection to the wound bed.
•
• Early dressing change around the third day after grafting may allow
predicting the “take rate” of the graft but risks secondary graft loss
through shear forces that disturb nascent vessel connections.
• More commonly the dressings are taken off for the first time 5–10
days after grafting.

82. RECIPIENT SITE CONSIDERATIONS
• Before planning a skin graft, several factors have to be taken into
consideration to achieve optimal tissue cover at the wound site.
• The wound bed quality has to be optimized for a successful “take” of
the graft and the skin color, thickness, and mechanical resistance of
the donor site area should ideally match the recipient site skin quality.
• Wound conditions often found in chronic or insufficiently debrided
burn wounds and characterized by low wound bed vascularization or
high bacterial loads will not allow skin grafts to be taken.

83. WOUND BED PREPARATION
• A good quantity of blood vessels near the surface is critical in order to
support graft viability.
• If highly vascularized peritendon and periosteum are still intact, skin
grafts can be performed.
• In chronic wounds:
• Re-epithelialization occurs at the wound margins that can grow into the tissue
and may inhibit the lateral reconnections of the graft.
• Therefore, wound margins should be sharply excised with a blade before
grafting.

84. • Experimental data suggest that the bacterial level must be brought
down below the critical level of 105 bacteria per gram of tissue to
allow a skin graft to take.
• Surgeons have learned over time that a “Granulating” wound has a
high likelihood of taking a skin graft.
• Active bleeding of the wound bed will likely lead to blood collection
between the graft and the wound bed, inhibiting graft take.
• Accurate homeostasis can be performed with bipolar cautery and
larger blood vessels can be ligated with fine resorbable sutures.

85. • Small areas of tendons and bones can either be prepared by vacuum-
assisted closure therapy to grow granulation tissue from the sides or
dermal substitutes can be used to cover functional structures.

86. FUNCTIONAL CONSIDERATION
• Consideration needs to be given to the size of graft needed, the
degree of wound contraction expected, the color and texture of the
skin required, and the need for adnexal glands.
• The amount of wound contraction expected is inversely related to the
amount of dermis in the skin graft.
• Full-thickness skin grafts are frequently used for nipple–areola
reconstruction, syndactyly release, or ectropion release.
• Full-thickness grafts are in short supply and can be augmented by
tissue expansion prior to harvesting full-thickness skin grafts.

87. • Very thin grafts such as epidermal grafts result in a donor site that
heals quickly with minimal contraction but provide little constraint to
wound contraction.
• The surgeon can use this as an advantage if wound contraction is
desired. For example, on large scalp wounds or abdominal wounds,
wound contraction may be desired to keep the skin graft as small as
possible while pulling the wound edges together over time.

88. AESTHETIC CONSIDERATIONS
• Skin color is determined by a complicated integration of skin texture,
melanin pigmentation, and blood flow.
• In general, replacement of tissue from a similar or adjacent site will
give the best color match.
• In the face, this is often the most critical aesthetic area and choosing
donor sites such as supraclavicular, posterior auricular, upper eyelid or
scalp skin grafts can often lead to an excellent color match.

89. • Skin texture is most commonly an issue when dealing with glabrous
skin (palms and soles of feet).
• In this case, placing a non-glabrous skin graft to cover these areas can
result in a very unnatural look
• Glabrous skin grafts are obviously in short supply but can be harvested
from the hypothenar eminence.

90. DONOR SITE CONSIDERATIONS
• The obligatory scarring or discoloration associated with donor sites must be
considered when taking a skin graft.
• Common donor sites include the thigh, trunk, and buttocks, regions
frequently covered by clothing.
• Full-thickness donor sites in the head and neck are pre- and postauricular
regions (the first is generally thicker), nasolabial crease, supraclavicular
region, eyelids, and neck.
• Other common regions include the inguinal crease that is often used to
cover large defects. In this case it is important to harvest laterally and away
from potentially hair-bearing regions of the pubis. This area generally heals
well and is hidden.

91. DONOR SITE DRESSING
• Topical gauze soaked with diluted epinephrine solution is useful to
stop bleeding at the donor site and can be left until the operation is
ended, adding an analgesic effect.
• The donor site of an STSG generally heals (re-epithelializes) in 7–21
days depending on the size and depth of the graft taken and the age of
the patient.
• A myriad of donor site dressings are available with multiple studies on
a variety of products.

92. • Traditionally, fine-meshed gauze, often impregnated with a petroleum-
based product, is placed over the wound and fixed in place.
• Cotton gauze is placed over this and removed a day or two after the
operation.
• The wound heals under this dressing and the dressing spontaneously comes
off when healed.
• The advantages of this type of dressing system are its simplicity, low cost,
and minimal wound care requirement.

93. • A large number of other dressings, including silver based, absorptive,
and biological, have been studied.
• In most of the cases the donor site heals spontaneously, thus simple
impregnated gauze is still the gold standard.

94. SKIN GRAFT STORAGE
• Skin grafts can be stored on a moist gauze at 4°C for up to 2 weeks,
although the viability decreases over time.
• Experimentally, storage can be extended using cell culture media.
• For degloving injuries, the skin can be defatted acutely and reapplied
as a full-thickness graft.

95. COMPLICATIONS
1. Hematoma
2. Seroma
3. Infection
4. Non-take
5. Wound Contraction
6. Instability
7. Cosmetic issues
8. Doner Site

96. HEMATOMA
• Any liquid between the wound and skin graft can impair skin graft take.
• Since bleeding represents one of the most important complications
after excision and grafting with up to 100–200 mL of blood, every 1%
of body surface area that is excised, particularly from the scalp.

97. • The surgeon must be certain that bleeding has stopped prior to
dressing the wound. Suture ligation or cautery can be used to control
larger bleeding vessels; oozing can be controlled with pressure and/or
pharmacological methods such as topical thrombin, epinephrine, or
fibrin glue.
• To reduce bleeding during excision the area can be primarily injected
with epinephrine diluted in saline (tumescent technique).
• As discussed above, incisions of the graft should be done to allow fluid
evacuation through a compressive or suction dressing.

98. SEROMA
• Serum imbibition is essential for early skin graft survival.
• Excessive serum, such as a seroma, will prevent or delay skin graft
take.
• Seromas are better tolerated than hematomas, and adequate
fenestrations (pie crusting) can prevent this problem.

99. INFECTION
• When skin graft infections occur, pus often accumulates beneath the
skin graft and can rapidly spread.
• If an infection is found early, prompt incision and drainage of the fluid
beneath the graft can often salvage some or all of the skin graft.
• A large number of dressings have been developed that carry a variety
of topical antimicrobial agents.
• Silver nitrate, mafenide acetate, and silver ion dressings are commonly
used.
• Bacteria seem not to develop resistance easily to silver products,
making these products desirable.

100. NONTAKE
• Unfavorable conditions:
1. Malnutrition,
2. Vasculitis
3. Malignant diseases
4. Steroids
5. Chemotherapeutic medications

101. WOUND CONTRACTION
• Wounds covered with skin grafts can still undergo wound contraction
leading to a scar contracture.
• After the acute inflammation phase the contraction starts.
• Fibroblasts from surrounding tissues and from blood circulation 
start to be activated  repopulate the wound between the graft and
the wound bed.
• Collagen deposition allows wound maturation.
• Collagen is deposited  cross-linking occurs  extracellular matrix
becomes mechanically resistant.

102. • This increase in mechanical resistance allows mechanical interaction
with fibroblasts that develop fibers called alpha-SMA.
• The development of alpha-SMA coincides with
• Fibroblast  Myofibroblast

103. INSTABILITY
• Shear forces are a major cause of skin graft failure that can disrupt the
nascent fragile blood vessel connections.
• Later, thin skin grafts have less collagen content and are prone to
delamination due to shear forces.

104. COSMETIC ISSUES
• Unpleasant net-like patterns of meshed STSGs are much more
prominent than non-meshed or full-thickness grafts.
• Color differences are a common problem if donor sites could not be
optimally chosen.

105. DONOR SITE
• Infection at donor sites can occur from bacterial contamination during
the operation or in the postoperative period.
• These infections are treated with topical antimicrobial agents,
including silver dressings.
• The delay in healing of donor sites due to infection can lead to
hypertrophic scar formation.
• Hypertrophic scar or keloid formation can also result from deep donor
sites or in patients with a propensity for scarring.
• Itching is a common reaction to donor sites as well as hypersensitivity
to changes in temperature.

106. FUTURE

107. DERMAL SUBSTITUTES
• Burke et al. first described a collagen–glycosaminoglycan scaffold to
treat dermal defects in the early 1980s.
• Dermal substitutes are widely used in large burn injuries, when skin
lesions are so extensive and unaffected donor skin areas are often
limited.
• Cadaver skin (allograft) or dermal substitutes can be used initially to
cover large defects.

109. • Dermal regeneration is very limited in our skin and full-thickness skin
defects heal by secondary intention with scar tissue formation.
• The difference of scar tissue and healthy skin besides the aesthetic
appearance is the viscoelasticity and therefore stability
• Scar tissue shows histological parallel-oriented collagen fibers, while
healthy dermis consists of randomly oriented collagen fibers.

110. • In some patients and for restricted donor sites keratinocyte cultures or
very thin STSGs can be attempted to close full-thickness defects.
• Integra:
• The first commercially available skin substitute
• Bovine-derived collagen type 1 cross-linked matrix with glycosaminoglycans
• Similar to the dermal structure and covered by a silicone sheet to recreate
temporarily the function of the epidermis.
• Can be applied to a vascularized wound bed blood vessels and cell growth
into the collagen matrix  create a vascularized neodermis after 2–3 weeks.

111. • During the avascular period, the
dermal graft is very sensitive to
infection, one of the main
disadvantages of the two-step
strategy.
• Once revascularization is
accomplished, the silicone layer can
be removed, and the epidermal
replacement can be granted by either
keratinocyte cultures or a thin STSG.
• Newer clinical studies show that
small areas of exposed tendon or
bone without remaining
peritendineum or periosteum can be
successfully grafted with Integra.

112. • Matriderm:
• (Dr. Suwelack Skin and Health Care), a bovine-derived collagen matrix with
noncross-linked collagen fibers of types I, III, and V matrix coated with elastin
fibers.
• Allografts and xenografts will be rejected by the recipient and may
adhere in patients with large burn injuries for several weeks because
of the posttraumatic immunosuppressed stage.

113. • After 2–3 weeks dermal dressings will be removed and a well-
vascularized wound bed is found underneath that is ready for final skin
reconstruction by autologous grafts.
• Another drawback for human- and porcine-derived dermis is possible
viral infection transmission.

114. CELL CULTURES
• Epithelial cell culture autografts
were first introduced by Rheinwald
and Green in 1975 and pose a
milestone in skin regeneration.
• In patients with extensive burns,
donor sites are often limited.
• Cultured epithelial autografts (CEA)
are keratinocytes harvested from a
small biopsy of the same patient
that are then expanded manifold in
the laboratory.

115. • The time needed to expand keratinocyte cultures in vitro for clinical
use is dependent upon the delivery method.
• In order to obtain sheets of confluent keratinocytes as in normal
epidermis, it may take up to 5 weeks.
• This time can be shortened to less than 2 weeks by expanding the
cultures on bio-scaffolds that allow cell attachment and proliferation
prior transplantation.
• Hyaluronan or collagen scaffolds
• Cell suspensions : the in vitro time to only 5–7 days.

116. • The introduction of CEA in clinical practice dates back more than 20
years, but the best delivery method as well as efficacy and indications
has not been identified yet.
• Published studies have reported taking rates of CEA on biomaterials
varying from 0 to 80%, raising many questions about their
effectiveness.

117. BIOENGINEERED CULTURED ALLOGENIC
BILAYERED CONSTRUCTS
• Cell-seeded skin constructs were first described in the early 1980s,
when autologous keratinocytes and fibroblasts were seeded into
collagen glycosaminoglycan matrixes by centrifugation.
• Further research found neonatal skin cells to be very efficient in
accelerating wound healing.
• Neonatal foreskin keratinocytes and fibroblasts were than used in
combination with biological or synthetically engineered scaffolds to
stimulate wound healing in topically applied allogenic skin constructs.

118. • Apligraf:
• (Organogenesis, Canton, MA, US and Novartis Pharmaceuticals, East Hanover,
NJ, US) is a
• Bilayered living skin-equivalent composed of type I bovine collagen and
allogenic keratinocytes and fibroblasts obtained from neonatal foreskin.

119. • Fibroblasts are cultured in the collagen matrix where they proliferate
and augment the extracellular matrix with all kinds of proteins.
• Keratinocytes are then added and build up the epidermal layer. The
living skin construct supports skin graft take in difficult wounds, such
as burn wounds, or accelerates healing in chronic wounds.
• With a shelf-life of 5 days at room temperature Apligraf has to be
applied fresh either as a temporary dressing or over meshed STSGs.

120. • Dermagraft:
• (Advanced Tissue Sciences, La Jolla, CA, US) does not contain keratinocytes
and is described as a living dermal skin construct consistent with a
cryopreserved bioabsorbable polyglactin mesh seeded with allogenic neonatal
fibroblasts.

121. THANK YOU