Skin Flaps and Skin Grafts

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Skin Flap vs. Skin Graft

Flap - Blood supply is maintained or immediate re-established
Graft - Blood supply is severed

Classifications of Skin Flaps

Either by:
1. Type of blood supply
Subdermal Plexus
Axial Pattern Flaps
Revascularized - re-attchement of blood vessels
2. Distance from wound
Local - usually subdermal plexus flaps
Distant - usually axial pattern flaps

Sub dermal plexus flaps

Also called Random base flaps
- Cutting into tissue w/ out knowing how strong the blood supply you are bringing is
Length : Width ration - do not exceed 3:1
- anything larger you risk losing blood supply

Axial Pattern Flaps

A type of transposition flap
Incorporate direct cutaneous artery and vein
Most commonly used vessels:
Thorcodorsal
Caudal Superficial Epigastric

Considerations when using the caudal superficial epigastric

Vessels in the female are more developed
Ipsilateral flap (same side) - can increase the distance the flap can extend, but risk kinking the blood supply
Contralateral flap - shorter distance, but less risk of compromising blood supply
Recommend spaying female, when doing these flaps
- the glands and nipple/thelium are still functional

Techniques commonly done with axial pattern flaps

1. Bridging incision
2. Tubing the flap - distant flap

Bridging Incision

Have to make an incision between the flap and the lesion

Tubing the flap

Cut the flap free in 2-3 weeks
This eliminates having to make a bridging incison

Blood supply used in local flaps

Subdermal plexus

Local flaps that rotate about a pivot point

1. Rotational flaps
2. Transposition flaps

Rotation flaps

Loose skin is rotated into the defect by cutting an arching incision on one side of defect
Arching incision needs to be 2.5x the width of the defect
A back cut incision increases the motility of the flap but also increases the risk of vascular compromise

Multiflap rotational flaps

2 or more rotational flaps
A 3 point suture line is NEVER ideal

Transposition flaps

3 sided flap
Donor skin is in a different plane from the wound
60-90 degrees is most common

Complication of transposition flaps

"Dog ears"
A small pucker of the skin that occurs when the edge of the skin doesn't quiet align
Small dog ears usually resolve during healing
Large ones should be removed at time of closure - easiest way is the lift up the tissue of the dog ear, cut through it parallel to the primary incision

Local flaps that do not rotate about a pivot point

1. Single pedicle advancement flap
2. Bipedicle advancement flap - not commonly used

Single pedicle advancement flap

Skin adjacent to the wound allows you to mobilize it to the wound
Common locations:
Dorsum, Ventral neck, Small flaps for eye lid reconstruction
Good trick is to angle your incision outward as you cut back, enhances likelihood you will bring good blood supply

Bipedicle advancement flap

Also called and H-plasty
Rarely used in small animals
Used more commonly in large animal medicine
Can be done w/ or with out Burrow's triangles (see picture)

Distant flaps

1. Tubed pedicle flaps
2. Pouched flap/Single pedicle direct flap

Tubed pedicle flap

Pouch Flap/Single direct pedicle flap

Distal limb wound is covered by skin on the trunk by bringing the limb to the flap
The limb should be sutured to the trunk PRIOR to creating the flap
- helps make location for the flap
- by finding the most comfortable position for the limb
Limb is in place for 10 days, ideally 14days
Need to close the skin beneath the flap as much as possible to avoid weepage
The limb is freed from the trunk with the flap attached.

Complications of Flaps

Flap edema - kink vessel
Seroma - put a light pressure wrap on it to stabilize it
Infection
PArtial deshisence - dehisences at corners d.t. severe edema
Vessel thrombosis w/ flap loss - if the flap gets back we need to take it out

Managing a compromised flap

Assess the vascular integrity
Vasoactive drugs??? - helps
Hyperbaric oxygen - works well
Leaches - used for venous compromise if you have blood accumulating under the flap
- not as good as they say they are

Indications for skin grafts

1. Skin defects on extremities
2. Excessive burn wounds
3. Adjunct to other reconstructive procedures

Classification

1. Donor-Host relationship
- Autograft
- Allograft
- Xenograft
2. Thickness
- Full thickness
- Split thickess

Definitions

Autograft - from the same patient - MOST USEFUL
Allograft - same species
Xenograft - different species

Full thickness vs. Split thickness skin grafts

Full thickness
- Epidermis and dermis, thus includes hair follicles and adnexa
- Most commonly used
- Best cosmetic appearance
Split thickness
- Epidermis and up to 2/3 dermis
- More commonly used in equine

Recipient bed should be

1. Healthy granulation tissue
2. Fresh wound w. sufficient blood supply to produce granulation tissue
- Healthy muscle is best

Areas where skin grafts will not take hold

Over tendons
Over missve amounts of fibrous tissue

When is granulation tissue ready for grafting?

1. When it is pink and glistening
2. Surface is smooth
3. Wound is contracting and epithelial migration is visible at wound margin

Preparation of recipient bed

1. Lightly scrap w/ scalpel blade to remove surface debris and expose capillaries
2. Cover bed w/ moist sponges soaked in CHX solution while graft is being prepped

Harvesting full thickness skin grafts

Dissect graft from donor site deep to the cutaneous trunci muscle

Remove cutaneous trunci muscle and superficial subcutaneous tissue prior to apply graft
- Important step, it enhanced revascularization of the graft

Can take off C. trunic and SQ tissue by placing sutures and using hypodermic needles to stretch the graft back to original size
Bulbs of the hair follicles should be visible if graft is properly prepared
- has a cobble stone appearance

A pattern is made for skin grafts when

1. Recipient site has irregular boarders
2. When exact fit is desired

Skin Graffting Techniques

1. Sheet
-Full thickness
-Spilt thickness
-Mesh, sieve, pie crust
2. Punch
-Seed or pinch
-Stamp
3. Strip
-Tunnel

Mesh, sieve, or pie crust grafts

Sheet grafts with parallel rows of staggered slits
Slight difference between these types based on the number of holes

Advantages of Mesh, Sieve or Pie crust grafts

1. Allows expansion of graft to cover larger area
2. Allows drainage of blood and serum from under the graft
3. Allows the graft to conform better to uneven surface

Mesh dermatome

A machine that allows us to make the mesh incisions very quickly and easily

Number of holes and length of slits determines

the degree the mesh graft can be expanded

Punch/Stamp/Seed/Pinch Graft

More commonly used in large animals
Not commonly used in small animals
Full thickness plugs of skin placed in the granulation bed to enhance epithelialization
- seeds epithelialization by minimizing wound surface area and increasing viable epithelium
Results in poor cosmetic appearance

Punch graft harvest and placement

Harvested using a punch tool 1 size larger than tool used to make holes i granulation tissue - accounts for contraction of the harvested graft
Remove m. and SQ tissue and prep recipient holes similar to other types of grafts

Graft application

As soon as the graft is placed it forms a fibrin seal - will feel stuck by the end of the procedure
Graft is thoroughly adhered after 48 hrs

Edges sutured and a few throws are but in the filed of the graft
Pass through the already present slits to avoid doing more damage

Closure of the donor site

Take a graft from a site which can be easily closed w/ walking sutures

Post op care

1. Apply AB ointment and no-adherent dressing to avoid an overgrowth of normal flora
2. Place a secondary absorbent layer followed by a cast or splint to keep immobilized
3. Change dressing in 24-48 hrs

Post op changes in healing grafts

Initially it may appear swollen
Later at 7 days PO it may look a bit nasty - take a wait and see attitude
Occasionally it looks great right away

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