Principles of Skin Grafting

Question 1

What are the two main types of skin graft?

Answer 1

Split-thickness skin graft (STSG) and full-thickness skin graft (FTSG).

Question 2

Which parts of skin are included in skin grafts?

Answer 2

The epidermis and part (STSG) or all (FTSG) of the dermis.

Question 3

What structures are included with the dermis in both split-thickness and full-thickness skin grafts?

Answer 3

Adnexal structures including sebaceous glands, hair follicles, sweat glands, and capillaries.

Question 4

How thick is a “thin” split-thickness skin graft?

Answer 4

0.005 to 0.012 inch.

Question 5

How thick is an “intermediate” split-thickness skin graft?

Answer 5

0.012 to 0.018 inch.

Question 6

How thick is a “thick” split-thickness skin graft?

Answer 6

0.018 to 0.028 inch.

Question 7

What are the advantages of meshing a partial-thickness skin graft?

Answer 7

Expansion of graft surface area up to six times, better contouring, decreased seroma or hematoma formation
beneath the graft.

Question 8

How does the mesher ratio affect the graft surface area?

Answer 8

A mesher expansion ratio of 1:1.5 (most commonly used) increases surface area by 50%, a ratio of 1:2 increases
surface area by 100%, etc.

Question 9

What are the disadvantages of meshing?

Answer 9

Waffled appearance, increased graft contraction (may be an advantage in some situations).

Question 10

Where should meshing be avoided?

Answer 10

On the face, hand, or forearm (cosmetically sensitive areas), and over joints, where contracture becomes a problem

Question 11

What is the postoperative bolster made of?

Answer 11

Xeroform, cotton balls or batting moistened in saline/mineral oil, secured with tie-over sutures or a stapled-on foam
dressing.

Question 12

How long should the bolster stay on postoperatively?

Answer 12

Five to seven days. Two to three days if the recipient site is contaminated.

Question 13

What are typical donor sites for split-thickness skin grafts?

Answer 13

Anterior or lateral thigh in adults, buttock in children (for concealment of scar). The abdomen, back, chest, and
scalp are often used if other donor sites are limited.

Question 14

What is an appropriate donor-site dressing?

Answer 14

Xeroform gauze dried with a hair-dryer or heat lamp is the traditional dressing. An occlusive semipermeable
dressing such as Opsite or Tegaderm may be used.

Question 15

What is the advantage of Tegaderm or Opsite for the donor-site dressing?

Answer 15

Faster healing and pain reduction.

Question 16

Do the dermis and epidermis regenerate in split-thickness donor sites?

Answer 16

The donor site epidermis regenerates from the periphery and from adnexal structures, but the dermis does not
regenerate. The donor site can be reharvested after it is well healed, if the underlying dermis is thick enough.

Question 17

How long does a split-thickness donor site take to heal?

Answer 17

A thin STSG donor site will heal within 1 week, whereas thicker STSG donor sites will take 2 to 3 weeks to heal.

Question 18

What are the advantages of full-thickness skin grafts?

Answer 18

Better color, thickness, and texture match with recipient site, decreased contraction.

Question 19

What are the disadvantages of full-thickness skin grafts?

Answer 19

Donor site must be closed primarily, limited donor sites, more difficult take compared to split-thickness skin grafts.

Question 20

What are typical full-thickness skin graft donor sites?

Answer 20

Supraclavicular, preauricular, postauricular, volar forearm, inguinal region.

Question 21

Why should an FTSG be defatted after harvesting?

Answer 21

Full-thickness skin grafts should be aggressively defatted to improve imbibition and take

Question 22

What is a composite graft?

Answer 22

A graft that includes fat, muscle, or cartilage in addition to skin.

Question 23

What is the maximum size of a composite graft?

Answer 23

Variable, but composite grafts that contain cartilage will not take if greater than 1 to 1.5 cm in diameter.

Question 24

What is the difference between an isograft/autograft, an allograft/homograft, and a xenograft/heterograft?

Answer 24

Autograft or isograft: from same person, or an identical twin.
Allograft or homograft: from same species. Xenograft or heterograft: from different species.

Question 25

What is the purpose of allograft or xenograft?

Answer 25

Used for temporary coverage of wounds until they are suitable for autografting. Cadaver allograft or more rarely porcine xenografts can be used. Cadaveric allografts do take initially, but are rejected after 10 days. Xenografts are more quickly rejected.

Question 26

What is the difference between primary and secondary skin graft contraction?

Answer 26

Primary contraction is the immediate shrinkage of a skin graft after harvesting, which is due to dermal elastin.
Secondary contraction is the contracture that occurs with healing, and is due to myofibroblast activity.

Question 27

Do split-thickness or full-thickness skin grafts contract more?

Answer 27

Primary contraction is greater with thicker skin grafts, whereas secondary contraction is greater with thinner skin
grafts.

Question 28

How does graft thickness affect the ability of the graft to sweat?

Answer 28

Thicker grafts contain more dermis, and therefore more sweat glands, and will have a greater potential to sweat.

Question 29

How does graft thickness affect the ability of the graft to grow hair?

Answer 29

More hair follicles are harvested with thicker grafts, and these will have greater hair growth.

Question 30

How does graft thickness affect the ability of the graft to develop sensation?

Answer 30

Thicker grafts contain more neurilemmal sheaths, allowing greater ingrowth of nerve fibers, and greater potential
for sensation over time. Thin grafts have less potential for sensation, but may develop sensation more quickly.

Question 31

What type of sensation develops first in a healing skin graft?

Answer 31

Pain returns first, then light touch, then hot/cold sensation.

Question 32

What are the phases of skin graft take?

Answer 32

Imbibition, inosculation, and revascularization.

Question 33

What is imbibition?

Answer 33

The first phase of take, involving the uptake of nutrients from serum in the wound bed by capillary action, lasting 48 to 72 hours.

Question 34

What is inosculation?

Answer 34

The second phase of take, involving donor and recipient capillary alignment.

Question 35

What is revascularization?

Answer 35

The third phase of take, revascularization occurs through the aligned capillaries, complete at 7 days.

Question 36

How does revascularization occur?

Answer 36

Controversial; new recipient site vessels may grow into the graft along the path of graft vessels, new ingrowth may
occur randomly, recipient and donor vessels may anastomose, or a combination of the above.

Question 37

To what type of tissue will a skin graft not take?

Answer 37

Exposed bone, cartilage, or tendon (unless there is overlying periosteum, perichondrium, or paratenon).

Question 38

What are the most common causes of failure of skin graft take?

Answer 38

Hematoma or seroma, poorly debrided or poorly vascularized wound, shearing of the graft, and infection. The
most common is hematoma or seroma beneath the graft.

Question 39

What level of bacterial load in the recipient site precludes skin graft take?

Answer 39

Skin grafts will not take in wounds with bacterial loads of 105 per gram or greater.

Question 40

What are the two phases of graft adherence?

Answer 40

The first phase is due to fibrin deposition between the graft and the wound bed, lasting 72 hours. The second phase
involves ingrowth of vessels into the graft and production of fibrous tissue.

Question 41

Once a skin graft is well healed, how should it be taken care of?

Answer 41

Hand-lotion or cream should be used to prevent desiccation. Skin grafts have decreased sweat and sebaceous glands. Sweat glands do not function until innervated. Sebaceous gland function is also delayed, although innervation is not required for function.