Ch 78 local and 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

anatomy and physiology

Answer 4

• skin has a segmental arterial supply through muscles, to arborize in three distinct plexuses that run parallel to the skin surface
• connections between these vascular elements, providing excellent collateral flow to adjacent areas of skin
• strength and compliance due to Collagen and elastin fibers (collagen accounts for 90% fiber content)
• Growth Factors Important in Neovascularization (VEGF)
• • delay phenomenon

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 by gradually restricting blood supply
- Ischaemic preconditioning, resistance to ischemia increases after short episodes of vascular occlusion
- Decreased production of PGF2alpha (vasoconstruction) with elevated PGE2 (vasodilation)
- Norepiphedrine depletion as a result of the delay causes 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

Major factors contributing to the delay phenomenon (5):

Answer 7

• alteration in sympathetic tone,
• dilation of choke vessels,
• reorientation of vessels,
• early and late changes in tissue metabolism,
• neovascularization

Question 8

pavletic delay technique

Answer 8

a total 3-week delay; at 18 days, half of the pedicle is divided, and the remainder of the pedicle is severed 3 days later.

Question 9

What growth factor may be important for neovascularisation?

Answer 9

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

Question 10

What is a composite flap?

Answer 10

Includes underlying muscle, oral mucosa or both

Question 11

Guidelines

Answer 11

• The aim of a flap is to transfer tension from edges of the original wound to fresh wound edges created by relocation of donor skin.
• Removal of skin from the donor site should not expose vital structures
• manipulated to determine lines of tension, templates
• most effective when developed adjacent to the skin defect
• advancement flap should be as long as, or preferably longer than, the length of the wound
• flap must not be too narrow.
• not to damage the subdermal plexus

Question 12

Types of Subdermal Plexus Flaps (7)

Answer 12

advancement flap,
rotation flap,
transposition flap
interpolation flap
plasty
distant flaps
composite

Question 13

Advancement flap: Shifts skin without rotation

3 types

Answer 13

• Single pedicle advancement
• Bipedical advancement
• H-plasty

Question 14

Rotation flap:

Answer 14

Semicircular flap that cover a triangular defect along one border of the flap

Question 15

Transposition flaps

Answer 15

Transposition flaps also share a common border with the defect, however, the flap has to be rotated across intact skin to reach an adjacent defect

Question 16

Interpolation flap

Answer 16

Lack a common border with the recipient bed. Must be tubed or incorporated into a bridging incision

Question 17

How is a rotation flap made?

Answer 17

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 18

How do you develop a transposition flap?

Answer 18

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 19

What is an example of a direct distant flap?

Answer 19

A pouch/hinge flap

Question 20

List some examples of subdermal plexus flaps (9)

Answer 20

• Skin fold flaps
• Scrotal flap (close inguinal and perineal defects)
• Perivulvar flap (perineal defects dorsal or cranioventral to the vulva)
• Preputial reconstructions (bipedical flap with free buccal mucosal graft)
• Phalangeal fillet
• Labial flaps
• Lip-to-Lid
• Distant direct
• Tubed flaps

Question 21

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

Answer 21

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

close defects in the inguinum, pectoral region, lateral thorax, lateral flank, lateral and medial thigh, lateral and medial stifle, and lateral and medial upper limb and elbow regions

Question 22

Phalangeal Fillet

Answer 22

digit is sacrificed

Question 23

Labial Flaps

Answer 23

full-thickness composite flaps from the upper or lower lip can be completely mobilized to close rostral labial defects
- oral mucosa is incised 5 mm from its gingival attachments
- With extensive upper lip defects, buccal rotation may result in a significant mucosal defect along the caudal portion
- Because of its elasticity, however, the lower lip can occasionally be advanced rostrally or caudally solely by incision of the mucosa (a long skin incision is not required to maximize rostral advancement of the lip)

Question 24

lip to lid flap

Answer 24

• high success rate is probably a result of vascular contributions from the angularis oris artery.
• recommened width-to-length ratio for a lip-to-lid flap? No more than 1:2
• with a marking pen at a 45‐ to 50‐degree angle to a
  line passing through the medial and lateral canthi.
• During elevation of the flap, care must be taken to avoid accidental injury to underlying structures, including
  the facial vein, parotid duct, and buccal nerve
  An optional second‐stage revision procedure will improve cosmetic results

Question 25

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

Answer 25

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

Question 26

When can a distant direct pouch flap be let down?

Answer 26

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 27

When can a developed tube flap be rotated?

Answer 27

- 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 28

Why is adherence of flaps to the underlying SQ important?

Answer 28

Reduces dead space Encourages neovascularisation Decreases tension along the flap edge

Question 29

How does radiation therapy effect flap survival/complications?

Answer 29

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 30

How does hyperbaric oxygen therapy effect subdermal plexus flaps?

Answer 30

Small but consistent improvement in survival of random flaps

Question 31

complications (4)

Answer 31

infection, seroma, skin edge dehiscence, necrosis

Question 32

infection

Answer 32

- contaminated, devascularized, or chronic wounds should be managed open until clean/granulation - gentle handling

Question 33

seroma

Answer 33

- closed suction drains, - placement of a soft compressive bandage - restriction of vigorous exercise in the first 2 to 3 weeks

Question 34

dehiscence (7)

Answer 34

Potential causes: - infection, - tension, - surgical trauma, - flap necrosis - systemic illness - radiation - poor blood supply as a result of previous surgery *Adherence of flaps to underlying subcutaneous tissues reduces dead space, encourages neovascularization, and decreases tension*

Question 35

Flap necrosis (6)

Answer 35

- requirement of the skin exceeds the capacity of the subdermal plexus perfusion - become apparent in the first 2 to 3 days after surgery - Devitalized skin may either undergo liquefactive necrosis or become an escha - necrotic skin should be debrided causes - narrow pedicle, - damage to the plexus during sx, - thrombosis - decreased peripheral perfusion or oxygenation - Self-trauma - pressure from bandages

Question 36

Complications and influence of cutaneous closure technique on subdermal plexus flaps in 97 dogs (2006–2022) Logothetou 2024

Answer 36

Retrospective monocentric study. n=97 subdermal plexus flaps in dogs - complications: 53.6% overall, 35% dehiscence, 4.4% necrosis - 14.4% revision, 2.1% euthanasia due to dehiscence - closure technique: skin staples 13/18 (72.2%), suture 39/79 (49.3%) - not significant - lower incidence: location on the head, advancement flap - increasing bodyweight → increased incidence of complications

Question 37

The pinna composite flap for wound reconstruction in a dog Price 2021 | liptak

Question 38

Indications, complications, and outcomes associated with subdermal plexus skin flap procedures in dogs and cats: 92 cases (2000–2017) Jones 2019

Answer 38

53 dogs and 20 cats Types of SPSFs included advancement (31 [34%]), axillary fold (20 [22%]), inguinal fold (20 [22%]), rotation (16 [17%]), transposition (3 [3%]), and distant direct (2 [2%]). Complications were noted for 47 (51%). minor for 34 (37%) procedures and major (requiring second surgery or > 50% flap failure) for 13 (14%) occured ~ 1 week after surgery Outcome was considered excellent for 44 (48%) procedures, good for 33 (36%), dehiscence [30%]), seroma[12%]), partial necrosis[10%]), infection [9%]), discharge (4 [4%]), ulceration (2 [2%]), and self-trauma (1 [1%]).