general points, random & local flaps

Question 1

list ways to address a discrepancy when undertaking an arterial anastomosis

Answer 1

1. Dilate small vessel
2. Oblique transection
3. end-to-side
4. telescoping, sleeve and cuff
5. spatulation
6. venous coupler (for vein)
7. interpositional vein graft (reversed)

Question 2

how do you define a flap?

Answer 2

• a composite of tissue that is transferred to a new location with its vascular pedicle (or by reconstituting its vascular pedicle)
• a unit of tissue (any combination of skin, fat, muscle, bone, tendon, nerve, or fascia) that is transferred from a donor site to a recipient site while maintaining (or reconstituting) a blood supply through a vascular pedicle

Question 3

how do you classify flaps?

Answer 3

Cormac and Lamberty suggested the 6 C’s:

• Circulation: a) random; b direct / axial; c) indirect / perforator (fascio-, septo-, musculo- cutaneous)
• Conformation / Vascular Directionality – normograde / anterograde, retrograde / reversed, flow -through
• Constituents: cutaneous, fasciocutaneous, musculocutaneous, osseomyocutaneous, etc
• Construction / Transfer Method – advancement, rotation, transposition, interpolation, distant transfer

o Advancement flap – move in a direction directly forward without any lateral movement

o Rotation flaps – semicircular flaps that rotate about a pivot point into an adjacent defect

o Transposition flaps – usually rectangular and move laterally about a pivot point into an adjacent defect

o Interpolation flaps – transfer skin above or deep to an intervening skin bridge to a non-adjacent defect

o Distant Transfer – tubed pedicle or free tissue transfer

• Contiguity – Relationship to defect (local/regional/distant/free)
• Conditioning – delay, tissue expansion

Question 4

Describe the 5 plexuses of skin and subcutaneous tissue

Answer 4

• Subepidermal
• Dermal
• Subdermal
• Subcutaneous
• Fascial
  
  • larger prefascial
  • smaller subfacial
  • intrafascial – very minor

Question 5

Describe an angiosome

Answer 5

• Angiosomes (40 in total) – 3D units of skin & underlying deep tissue supplied by a single source artery (ateriosome) & associated venosome
• Single source vessel may supply multiple angiosomes (ie perforasomes)
• Defines flap boundaries
• Can be linked by true anastamotic arteries or choke anastamotic vessels
• Territories are dynamic and depend on intravascular pressure & caliber of choke vessels

Question 6

Describe the 3 ways that reverse flow flaps work:

Answer 6

• Two systems of venous arcades with NO VALVES
  
  • Macrovenous connections (no valves) criss-cross between venae commitantes and provide a mechanism whereby the valves of the venae commitantes are bypassed
  • Microvenous connections (no valves), surround the artery as the vena arteriosa and also provide a connection to the venae commitantes
• Increased venous hydrostatic pressure within the flap causes a dilatation of the venae commitantes which may cause the valves to become incompetent
• Surgical sympathectomy may also provide the necessary venous dilatation

Question 7

what is a suspected mechanism of perfusion of venous flaps?

Answer 7

• Plasmic imbibition
• Perfusion pressure
• Sites of AV anastomosis
• V-v connections
• Circumvent valves

Question 8

what are the advantages and disadvantages of venous flaps?

Answer 8

• Advantages – smaller, thinner, no artery needed, fast and easy to raise, no donor site mobdiity, anatomically constant pedicle (e.g. saphenous)
• Disadvantages – Poorly understood physiology, limited size, inconsistent survival, potential hemodynamic complications from creating the AV shunt

Question 9

describe the physiology of skin microcirculation

Answer 9

• Systemic
• Neurologic regulation
  
  • Adrenergic –> SNS control of smooth muscle (vasoconstriction = alpha, vasodilation = beta)
  • Cholinergic –> parasympathetic = vasodilation
• Humoral regulation (important in surgical sympathectomy)
  
  • Vasoconstriction = adrenalin/serotonin/thromboxane, prostaglandin F2 (PGF2)
  • Vasodilation = histamine, bradykinin, PGE2
• Local
• Metabolic factors (↑PCO2, [K+], ↓PO2, pH) –> vasodilation
• Physical factors – temperature, viscosity (↓ flow with hct >.45)

Question 10

what are the 3 physiologic processes that occur during acute flap elevation?

Answer 10

Early flap hemodynamics rely on the balance of these 3 processes:

Increased Vascular Resistance

• Severing of cutaneous vessels - incr flap ischemia
• Ischemia and surgical trauma - incr inflammation, ­ capillary permeability and endothelial cell edema
• Interstitial and endothelial cell edema - decr intraluminal diameter and incr­ vascular resistance
• cap permeability - incr blood viscosity­ and contributes to­ vascular resistance

Vasoconstriction

• Surgical sympathectomy – initial release terminal neurotransmitters (adrenaline and noradrenaline) –> vasoconstriction
• Sympathetic re-innervation takes about 4 weeks (by then, your flap has vascular ingrowth)
• Surgical trauma also results in release of platelet-derived vasoconstrictors (Serotonin & TxA2)

Vasodilatation

• Sympathectomy eventually results in vasodilatation (and insensitivity to plt-derived v-const)
• Surgical trauma & anaerobic metabolism = release of local vasodilators (eg. bradykinin, histamine, and prostaglandins)

Question 11

Describe the temporal changes in vascularity of a flap after elevation

Answer 11

• 0-12 hours: vasoconstriction, marked congestion and edema in the 1st 24 hours
• 12-24 hours: vasodilatation
• 1-3 days: ↑ choke vessels (size and number), axial reorientation of flow
• 4-7 days: ↑ circulatory efficiency
• Week 1: inosculation
• Week 2: return to normal perfusion efficiency (can divide pedicle 10-21 days)
• Week 3: inosculation complete, flow 90-100% normal

Question 12

Define vascular delay

Answer 12

• surgical PARTIAL disruption to the blood supply of a flap at a preliminary stage prior to transfer

Question 13

How does vascular delay work?

Answer 13

• Early
  
  • Sympathectomy (with vasodilation, increased flow, and decreased AV shunting)
  • Vascular reorganization via increase size and longitudinal re-orientation of choke vessels (into true anastomoses)
  • Ischemic pre-conditioning via early metabolic response: Metabolic tolerance to hypoxia and ischemia
  • Others: reactive hyperemia
• Late
  
  • Tissue metabolism: blunted secretion of vasoconstrictive cytokines (TXF2) and increased secretion of vasodilatory cytokines (TXE2)
  • Neovascularization

Question 14

describe the crane principle

Answer 14

• Technique of transforming an ungraftable bed to a graftable one
• Stage 1 – pedicled flap placed in defect
• Stage 2 – superficial portion replaced to original place; subcutaneous tissue in defect now can accept a graft

Question 15

describe the pathophysiology of acute flap failure

Answer 15

• Intrinsic factors – arterial insufficiency (tip nec = vasodil @ tip/vasocon at bas), venous insufficiency
• Extrinsic factors – systemic (transient: hypotension, caffeine; preexisting: PAD, DM) , local (tension/pressure/dressing)
• Ischemia-reperfusion injury
• ATP stores broken down –> xanthine –> PMNs then release O2 free rad –> inc cell adhesion + more PMN –> ++ proimflammatory cytokines/cell injury/death vascular permeability/inc cell adhesion/microthrombosis
• No Reflow – never flows d/t irrev vascular damage with prolonged ischemia time

Question 16

List the advantages and disadvantages of using a local flap

Answer 16

• Advantages
• Replace like with like: colour, texture, thickness, quality
• Local anaesthesia permits outpatient procedure
• Complete 1’ closure of defect
• Possibly sensate
• A flap provides an additional blood supply
• Disadvantages
• Require planning and experience
• Partial or total flap failure
• Functional aberrations (ectropion, nasal obstruction, microstomia)
• Cosmetic aberrations (pin-cushion, scar, transfer of hair-bearing skin)

Question 17

outline the reconstructive ladder

Answer 17

1. Primary closure
2. Healing by secondary intention
3. Delayed primary closure
4. Negative pressure wound therapy
5. Skin graft
6. Dermal matrices (ADM)
7. Local flaps
   
   1. Local skin flaps- random pattern, axial pattern, after tissue expander
   2. Local muscle flap
   3. Local myocutaneous flap
8. Tissue expansion
9. Regional/ distant flaps: Pedicled Flap
10. Free flap

Question 18

describe and draw a rotation flap

Answer 18

• Semicircular flap that rotates about a pivot point into a defect
• Triangularize the defect
• Flap arc should be 5-7 X the height of the triangulated defect
• Axis of rotation/pivot point should be 2.5-3 X the length of the triangulated defect
• Maximum tension is from the pivot point to the leading edge (think of as original “height” of triangulated defect)
• May require a back cut or Burow’s triangle

Question 19

describe and draw a transposition flap

Answer 19

• Classically, rectangular & move laterally about a pivot point into an adjacent defect
• Distance between pivot point and flap margin should be greater than distance to the defect; height of flap should be longer than height of defect
• Maximum tension runs diagonally across the flap
• May also require a back cut or Burow’s triangle

Question 20

describe the lengthening you will get with various angles of Z-Plasty

Answer 20

• 30⁰ = 25%
• 45⁰ = 50%
• 60⁰ = 75%
• 75⁰ = 100%
• 90⁰ = 120%
• 4-flap Z-plasty (60’) = 150%

Question 21

What are the indications / purpose of Z-Plasty?

Answer 21

1. Increase length (decrease width) - lengthen a scar or webbed neck
2. Break up a straight line or circumferential scar - may look less obtrusive; constriction band
3. Release (or prevent) a contracture or band - ie across joint
4. Reposition topographic structures - displaced commissure, medial canthus
5. Create a web or cleft; or effacement - deepen 1st web, Furlow CP closure (effacement)

Question 22

Describe the Limberg flap

Answer 22

• Transposition flap of exact geometry rhomboid defects
• Four different flaps available for each defect
• Angles should be 60 and 120; lengths are equal
• Maximum tension is from D to F, so the flap should be designed along the RSTL’s (want most laxity along ADF or BC)
• Changes the line of tension on closure by 60⁰

Question 23

• Modified Limberg up to 90⁰ angles (often 30&150⁰)
• Four different flaps available for each defect
• Donor limb is extended out an angle which bisects the parallel and perpendicular planes
• E to F is described as parallel to long axis OR at 60’
• Facilitates donor site closure

Question 24

Describe a bilobed flap

Answer 24

• Two transposition flaps along the radius of a circle
• Each transposed up to 90 degrees, width 1st flap slightly less than the width of the defect and the width of the 2nd flap less than the width of the 1st flap
• Zitelli modification
• Identify pivot point= length radius of defect, then triangulate defect
• Draw line 90 degrees with axis of defect = axis of 2^nd lobe
• Outline semicircles from center of defect +tangential to defect
• Draw 1^st lobe diameter= diameter of defect x, to semicircle tangential to defect
• Draw 2^nd lobe: half diameter of defect, beyond tangential semicircle

Question 25

what is the difference between autograft, isograft, allograft and xenograft?

Answer 25

* auto - self * iso - between individuals but identical, same species (identical twin) * allo - between indivuals (cadaver), same species * xeno - different species

Question 26

list indications for skin grafting

Answer 26

· Skin deficiency: Wounds that cannot be closed primarily (traumatic, oncologic, burn); after scar contracture release; congenital skin deficiency (syndactyly) · Hair restoration · Vitiligo · NAC reconstruction

Question 27

list contraindications to skin graft

Answer 27

* **Absolute** * Avascular, infected, neoplasm in wound bed * **Relative** * Wounds with compromised wound bed: pressure sore, irradiated, vasculitic, arterial insufficiency, malnutrition * Cosmetically sensitive areas (with superior alternative)

Question 28

compare stsg to ftsg

Answer 28

**STSG** **FTSG** **What** Epidermis & partial thickness dermis (often 0.010 – 0.014 of inch; ideally in papillary dermis) Full thickness epidermis and dermis **Indication** Large surface area, not cosmetically sensitive Small area, cosmetically sensitive +/- want to avoid 2’ contracture (ie face, hands) **Contraction** More 2’ contraction More 1’ contraction **Graft take** Very reliable (in optimal conditions) Less reliable, even in optimal conditions **Appearance & Pigmentation** Pigment alterations (hyper \> hypo) Less natural, shiney, no hair More natural appearing, pigmentation, texture Softer; can grow hair (+ or – depending) **Growth** No growth in children Growth in children **Sensory reinnervation** No/uncommon More common to at least sensory protection Can sweat once sensory reinnervation **Donor** Heal by 2’ intention in 10-21d Closed primarily; Epithelializes in ~ 48hrs; can deshisc **Complications** Scar: HTS, KS, “cobblestone” (when meshed) Bleeding, infection, graft loss (less risk vs FT) Contracture (incr vs FT), decr function Scar: (? Less) HTS/KS Bleeding, infection, graft loss (incr risk vs PT) Contracture (decr vs PT), decr function

Question 29

Describe considerations for donor site harvest for STSG and FTSG

Answer 29

* STSG * consider colour/texture match: "blush" zone when necessary (supraclavicular/neck, chest, scalp) * thin harvest in hair-bearing areas to maintain follicles * do not harvest from area w/ suspicious lesion * FTSG * for small areas/sensitive areas, to avoid contracture (primarily hands/face) * face: eyelid, supraclavicular, pre/post-auricular * hands/feet: instep, lateral great toe, hypothenar eminence * other: groin, dorsal foot, volar/dorsal wrist, AC fossa, medial arm * Prepuce, scrotum, labia minora provide darker pigmentation

Question 30

Compare donor site healing from areas of STSG harvest vs. FTSG harvest

Answer 30

STSG * 7-21 days (re-epithelialization from adnexa begins \<24 hrs) * Migration occurs from the wound edges & adnexa * Initial epithelial coverage by 7 -10 days (not very durable) * Serial STSG harvest if thick dermis (epithelium regenerates but dermis progressively thinned) – risk of HTS FTSG * epithelialization occurs at ~ 48 hrs (as per usual healing of primary closure) * risk of dehiscence

Question 31

List options for stsg donor site dressings

Answer 31

* Open (cheap, painful, ­ healing time) * Lubricant impregnated gauze (scarlet red, jelonet, xeroform) * Kaltostat: sodium & calcium salts with alginic acid (hemostatic) * Biobrane (transparent, ¯ pain) * Bio-occlusive (OpSite/Allevyn) (¯ pain, ¯ bulk, ++ fluid accum) * Autografting – optimal rx if excess skin available after grafting * Allografting – faster healing, ¯ pain, limited avail, risk diseases * Other: Cadaver, amniotic mem, CEA, xenografts

Question 32

what is graft expansion, why is it done?

Answer 32

* Graft expansion is the mechanism why which the surface area of donor tissue is increased * Indications include: * · ­ surface area of graft to cover larger defects · ­ cumulative diameter though which epithelial outgrowth can proceed · Improved adherence to convoluted/irregular wound · Some techniques permit effluence of blood/serum

Question 33

List mechanisms of skin graft expansion

Answer 33

* Meshing (Advantage – better contour, drainage, larger area, Disadvantage - ↑ contracture, poor cosmetic result) * Pinch grafts (combination FTSG centrally, STSG peripherally) * Relay transplantation * Meek island grafts – special dermatome and folding pattern * Microskin grafts (sheet grafts minced using Tanner-Vandeput dermatome (10:1) * Intermingling auto and allografts (sandwich, interstices perpendicular)

Question 34

describe the process of skin graft take

Answer 34

* **0 - 48 hrs – Plasmatic Imbibition** * Nourished by diffusion of plasma, oxygen and nutrients * Fibrin clot: Plasma fibrinogen forms a glue-like substance anchoring the graft to the bed * **48 hrs - 5 d – Inosculation & Capillary Ingrowth** * Capillary buds from recipient bed blood vessels contact with the graft vessels & open channels formed – initially afferent * **\> 6 d – Revascularization - primary** * Both afferent and efferent; capillary bud ingrowth, lymphatics established * Collagenous links begin to form between the graft and bed * **Secondary revascularization** – Occurs when inosculation fails

Question 35

describe maturation/remodelling of skin grafts (including process of contraction)

Answer 35

* **Cellular Hyperplasia** * 1^st 2 wks – pronounced epidermal hyperplasia occurs – scaling & crusting àReturns to normal at 4 wks * **Secondary graft contraction** * Occurs over time at recipient site, but related to graft factors * Mediated by myofibroblasts – contracture modified by thickness of dermal collagen (thin STSG \> thick STSG \>\> FTSG) * **Primary graft contraction** * Occurs immediately after harvest, completely independent of recipient site * FTSG (~40%) \> thicker STSG (~20%) \> thin STSG (~10%);

Question 36

Describe adnexal and sensory function after STSG and FTSG

Answer 36

* **Hair follicles** * FTSG with intact hair follicles will regrow hair - same pattern as donor * 4^th day post graft – original shafts slough and follicles begin to produce new hair (fine hair present by day 14) * STSG rarely grow hair * **Sweat Glands** * Resume function following nerve regeneration; More complete function in FTSG * Sweating pattern that of the recipient site (Application of moisturizing cream advised until sweat function returns) * **Sebaceous Glands** * FTSG - more sebaceous glands preserved, therefore graft tend to be softer and more pliable * STSG - growth of glands beneath the graft leads to formation of small milia, treated by unroofing * **Re-innervation** * Sensory recovery begins 4-5 wks post-grafting * Completion 12 – 24 months * Dependent on the accessibility of the neurilemmal sheaths to the invading nerve fibers (FTSG \>\> STSG) * Order of sensory return – pain, light touch, temperature (may be hyperalgesic for up to 1 yr)

Question 37

describe factors that may lead to skin graft failure

Answer 37

* **Loss of contact**: hematoma, seroma, movement/shearing (disrupts small capillaries) * **Poor healing**: poorly vascularized recipient bed, infection (local \>10⁵ organisms/g or systemic), malnutrition, systemic illness, immunosuppression (steroids, chemo), excess pressure * **Technical error**: rough handling, upside down placement, inappropriate thickness, inadequate bolster/stabilization