Ch 78 - Local or Subdermal Plexus Flaps

Question 1

What do subdermal plexus flaps rely on for survival?

Answer 1

Collateral circulation from the remaining cutaneous attachment and its vasculature

Question 2

What range of thickness is hairy skin?

Answer 2

0.5 - 5mm

Question 3

What are the three vascular plexus’ of the skin?

Answer 3

• Superficial subpapillary plexus
• Middle cutaneous plexus
• Deep subcutaneous plexus

Question 4

What substances within skin supply it with its strength and compliance?

Answer 4

Collagen and elastin fibers (collagen accounts for 90% fiber content)

Question 5

What is the delay phenomenon?

Answer 5

A group of mechanisms by which flap survival is enhanced through staged flap development.
- physiologically trained to rely on vasculature support from pedicle
- Ischaemic preconditioning
- Decreased production of PGF2alpha (vasoconstruction) with elevated PGE2 (vasodilation)
- Norepiphedrine depletion with delay causing vasodilation
- Number and size of vessels increase and their orientation change to favour vessels parallel to long axis of flap

Question 6

How has delayed development of single pedicle and bipedical flaps effected perfusion?

Answer 6

• Perfusion drops to 10% and 40% after initial elevation of single and double pedicle flaps respectively
• Circulation than rises to 120 - 150% of normal after approx 3wk
• Re-elevation of the flap after 3wk delay then causes a much smaller decrease in perfusion to 90% of normal, resulting in improved survival

Question 7

What growth factor may be important for neovascularisation?

Answer 7

VEGF - Local autologous PRP enhanced tissue perfusion and improved survival of subdermal plexus flaps due to vasodilation

Question 8

What is a composite flap?

Answer 8

Includes underlying muscle, oral mucosa or both

Question 9

Define advancement flap, rotation flap, transposition flap and interpolation flap

Answer 9

• Advancement flap: Shifts skin without rotation
• Rotation flap: Semicircular flap that cover a triangular defect along one border of the flap
• Transposition flaps also share a common border with the defect. It’s created within 90 degrees of the long axis of the defect.
• Interpolation flap: Lack a common border with the recipient bed. Must be tubed or incorporated via a bridging incision.

Question 10

List some types of advancement flap

Answer 10

• Single pedicle advancement
• Bipedical advancement
• H-plasty (double single pedicle advancement flaps)

Question 11

How is a rotation flap made?

Answer 11

For triangular wounds, a curved incision is begun at a point adjacent to the shortest side of the wound so that the leading edge of the flap shares a border with the long side of the wound

For rectangular wounds, bilateral rotation flaps can be made

Question 12

How do you develop a transposition flap?

Answer 12

A rectangular flap is created within 90 degrees of the long axis of the defect. Should be as wide as the defect and length equivalent to the distance between the pivot point and the most distant point of the defect

Question 13

What is an example of a direct distant flap?

Answer 13

A pouch/hinge flap

Question 14

What vessels are closely associated with the skin fold flaps allowing them to function as an axial pattern flap if included

Answer 14

• Elbow fold: Lateral thoracic artery
• Flank fold: Deep circumflex iliac artery

Question 15

List some examples of subdermal plexus flaps

Answer 15

• Skin fold flaps
• Scrotal flap
• Perivulvar flap
• Preputial reconstructions (bipedical flap with free buccal mucosal graft)
• Phalangeal fillet
• Labial flaps
• Lip-to-Lid
• Distant direct
• Tubed flaps

Question 16

What is the recommened width-to-length ratio for a lip-to-lid flap?

Answer 16

No more than 1:2

Question 17

What options are there if corneal abrasion is considered likely due to swelling after a lip-to-lid flap?

Answer 17

• Place a contact lens! Allows temporary protection until swelling and spastic entropion subsides

Question 18

When can a distant direct pouch flap be let down?

Answer 18

• Once the skin has healed (approx 2 weeks) one half of each pedicle is divided
• Remaining halves divided 2-3 days later and the flap is fully sutured to the remaining wound edges

Question 19

When can a developed tube flap be rotated?

Answer 19

• After 18d, one half of the pedicle base farthest from the wound is severed and then resutured
• Other half is severed on day 21 and is rotated to the wound
• Tubed section left in place for at least 3-4 more weeks after which time is can be gradually divided and excised

Question 20

Why is adherence of flaps to the underlying SQ important?

Answer 20

• Reduces dead space
• Encourages neovascularisation
• Decreases tension along the flap edge

Question 21

How does radiation therapy effect flap survival/complications?

Answer 21

High complications associated with radiation therapy
- 62% dehiscense
- 35% necrosis
- 27% infection

Risk for complications is highest when radiation is performed before flap procedures because of damage to local fibroblasts and blood vessels

Question 22

How does hyperbaric oxygen therapy effect subdermal plexus flaps?

Answer 22

• Small but consistent improvement in survival of random flaps: increases oxygenation of the flap.