11 – Skin Grafts

Question 1

What are skin grafts?

Answer 1

• Pieces of skin that are completely detached from the donor site
• Vascularized grafts require microsurgery to connect their main vessel to supply vessels in the recipient site
• Avascular grafts depend on ingrowth of blood vessels from the wound for survival

Question 2

Skin flaps

Answer 2

• Robust and require little aftercare
• Not easily used on sites at or distal to carpus or tarsus
• Good cosmetic appearance

Question 3

Skin grafts: characteristics

Answer 3

• More delicate; need protection and lots of aftercare
• Cosmetic appearance depends on graft thickness and donor site
• Donor site usually smaller than for flaps
• Especially useful for covering wounds of distal extremities

Question 4

What are the 2 ‘types’ of classification for skin grafts?

Answer 4

1. Full thickness
2. Partial thickness

Question 5

Partial (split) thickness grafts

Answer 5

• Can get big chunks of skin as you don’t need to close the donor bed (skin will grow back there)
• Donor site can be quite painful
• *requires special instrumentation for harvest
• Results in poor hair re-growth at both recipient and donor sites

Question 6

Full thickness grafts

Answer 6

• Prettier
• Easier to harvest
• Similar to partial thickness for graft survival
• Small animals usually get full thickness

Question 7

Why even bother with split thickness grafts?

Answer 7

• Used more often in large animals (ex. horses) and people due to scarcity of donor site tissue

Question 8

What are different types of skin grafts?

Answer 8

• Sheet, pie crust, mesh (all the same)
• Pinch and punch grafts
• Footpad free grafts

Question 9

Sheet, pie crust, mesh grafts

Answer 9

• All generally FULL thickness grafts
• Most common free grafts for small animals

Question 10

Pinch and punch grafts

Answer 10

• Easy to do under local anesthetic
• Take derm biopsy punches (ex. side of neck on horse) and move them to the recipient bed (in granulation tissue)

Question 11

What are the advantages of pinch and punch grafts?

Answer 11

• Minimal donor site morbidity
• Can be done under local anesthesia
• Motion at recipient site is less likely to dislodge tiny little independent graft: each graft moves independently
• Commonly used in horses

Question 12

What are some disadvantages of pinch and punch grafts?

Answer 12

• Not very cosmetic
• Majority of coverage is only epithelial: more prone to trauma than full-thickness skin

Question 13

Footpad free grafts

Answer 13

• Are punch grafts
• Place around periphery of wound
• Epithelial component will slough and regenerate

Question 14

How do skin grafts become incorporated?

Answer 14

• Graft adherence initially dependent on suturing and bandaging
• Fibrin attachment comes first
• Later, blood vessel ingrowth and collagen attachment occur
• *graft must be in close contact with wound bed to allow for nutrient/oxygenation of cells and later ingrowth of blood vessels/collagen

Question 15

Nutrition of skin grafts

Answer 15

1. Plasmatic imbibition
   a. Osmotic and capillary movement of wound fluid and proteins
2. Inosculation
   a. Open ends of vessels in wound bed and graft kiss and allow fluid exchange
3. Vessel ingrowth
   a. Capillary buds from wound bed invade graft

Question 16

What are 2 basic good recipient wound beds?

Answer 16

1. Healthy granulation tissue
2. Fresh wounds (ex. you removed a tumor)

Question 17

What are undesirable wound beds?

Answer 17

• Infected or contaminated tissue
• Desiccation, dead bone (can drill into bone)
• Very irregular surface

Question 18

What are some questions you when selecting an appropriate donor site?

Answer 18

• Can I harvest adequate skin and close the doner defect? (ex. pinch test)
• Do hair characteristics match the recipient site?
• Are there any donor site functional or cosmetic concerns?

Question 19

What is the technique for full thickness mesh grafting?

Answer 19

1. Trace template of the wound
2. Use template to mark donor site
   a. Pay attention to hair direction at both sites and ability to close donor wound
3. Graft harvest
4. Graft preparation
5. Preparation of recipient site
6. Graft inset

Question 20

Graft harvest

Answer 20

• Excise graft from donor site, leaving as much subcutaneous tissue as possible with the donor bed
• Mark graft so you know which way the hair will go
• Suture the donor site

Question 21

Graft preparation

Answer 21

• Remove all subcutaneous tissue
  o Fold graft over finger, SQ up and cut the SQ tissue away with Metzenbaum scissors
  o Look for cobblestone appearance of the bottom of hair follicles (if see open follicles=too deep)
• Pin the graft to sterile foam or cardboard and make multiple holes with scalpel

Question 22

Preparation of recipient site

Answer 22

• Gentle surgical prep if wound is not fresh
• Excise excessive granulation tissue, if present
• Excise epithelialized edges
• Pressure wrap to control hemorrhage if necessary

Question 23

Graft inset

Answer 23

• Establish correct orientation
• Stabilize graft edge to wound edge
  o Simple interrupted or continuous sutures
  o Skin staples
• Tacking sutures withing body of graft to hold the middle down
• Suture down to wound bed between perforations
• NO tension
• Excellent apposition: suture edge of graft to edge of defect WITHOUT overlap

Question 24

What are some postoperative considerations?

Answer 24

• *Stabilize the graft

Question 25

Stabilize the graft

Answer 25

• Bandages
• Negative pressure wound therapy
• Splints/external skeletal fixation in high motion areas

Question 26

Graft bandaging

Answer 26

• First layer must be NONSTICK and POROUS so that fluid can escape
  o Petrolatum-impregnated gauze=GOOD
  o Telfa pad=BAD
• Next layer: absorbent material
  o Splint if needed
  o Vetwrap or Elastoplast
• *try to avoid changing the bandage for 5 days post-op so you don’t disrupt ingrowth of blood vessels