Ch 78 local and subdermal plexus flaps Flashcards
What do subdermal plexus flaps rely on for survival?
Collateral circulation from the remaining cutaneous attachment and its vasculature
What range of thickness is hairy skin?
0.5 - 5mm
What are the three vascular plexus’ of the skin?
Superficial subpapillary plexus
Middle cutaneous plexus
Deep subcutaneous plexus
anatomy and physiology
- 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
What is the delay phenomenon?
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
How has delayed development of single pedicle and bipedical flaps effected perfusion?
- 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
Major factors contributing to the delay phenomenon (5):
- alteration in sympathetic tone,
- dilation of choke vessels,
- reorientation of vessels,
- early and late changes in tissue metabolism,
- neovascularization
pavletic delay technique
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.
What growth factor may be important for neovascularisation?
VEGF - Local autologous PRP enhanced tissue perfusion and improved survival of subdermal plexus flaps due to vasodilation
What is a composite flap?
Includes underlying muscle, oral mucosa or both
Guidelines
- 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
Types of Subdermal Plexus Flaps (7)
advancement flap,
rotation flap,
transposition flap
interpolation flap
plasty
distant flaps
composite
Advancement flap: Shifts skin without rotation
3 types
- Single pedicle advancement
- Bipedical advancement
- H-plasty
Rotation flap:
Semicircular flap that cover a triangular defect along one border of the flap
Transposition flaps
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
Interpolation flap
Lack a common border with the recipient bed. Must be tubed or incorporated into a bridging incision
How is a rotation flap made?
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
How do you develop a transposition flap?
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
What is an example of a direct distant flap?
A pouch/hinge flap
List some examples of subdermal plexus flaps (9)
- 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
What vessels are closely associated with the skin fold flaps allowing them to function as an axial pattern flap if included
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
Phalangeal Fillet
digit is sacrificed
Labial Flaps
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)
lip to lid flap
- 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
What options are there is corneal abrasion is considered likely due to swelling after a lip-to-lid flap
Place a contact lens! Allows temporary protection until swelling and spastic entropion reside
When can a distant direct pouch flap be let down?
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
When can a developed tube flap be rotated?
- 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
Why is adherence of flaps to the underlying SQ important?
Reduces dead space
Encourages neovascularisation
Decreases tension along the flap edge
How does radiation therapy effect flap survival/complications?
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
How does hyperbaric oxygen therapy effect subdermal plexus flaps?
Small but consistent improvement in survival of random flaps
complications (4)
infection,
seroma,
skin edge dehiscence,
necrosis
infection
- contaminated, devascularized, or chronic wounds should be managed open until clean/granulation
- gentle handling
seroma
- closed suction drains,
- placement of a soft compressive bandage
- restriction of vigorous exercise in the first 2 to 3 weeks
dehiscence (7)
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
Flap necrosis (6)
- 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
Complications and influence of cutaneous closure
technique on subdermal plexus flaps in 97 dogs (2006–2022)
Logothetou 2024
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
The pinna composite flap for wound reconstruction
in a dog
Price 2021
liptak
Indications, complications, and outcomes associated
with subdermal plexus skin flap procedures
in dogs and cats: 92 cases (2000–2017)
Jones 2019
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%]).
