CHAPTER 13: MICROSURGERY AND FLAPS Flashcards
What are the functions of skin?
IS IT PUS?
I nfection S ensation I mmunological surveillance T emp regulation P revent fluid loss U V protection S tructural barrier
What are the layers of the epidermis?
Colin Likes Grilled Spicy Beef
Stratum
1. Corneum - dead keratinized cells
2. Lucidum - clear layer of dead cells (glaborous)
3. Granulosum - mature keratinocytes, protein synthesis
4. Spinosum - prickle cell layer - keratinocytes produce keratin - SCC orig
5. Basale - proliferating layer, contains melanocytes - BCC originates here
What cells are found in the epidermis?
Keratinocytes → predominant cell type
Langerhans cells → immune system → antigen presenting cells
Merkel cells → mechanoreceptors of neural crest origin
Melanocytes → from neural crest, in stratum germinativum, produce melanin.
What are the layers of the dermis and what are they comprised of?
95% thickness of skin
Papillary - superficial → finer collagen fibres, more cells
Reticular - deep → coarser collagen, less cells
- Collagen fibres - T1:3 = 4:1
- Elastin fibres - elastic recoil
- Ground substance - hyaluronic acid, dermatan sulphate, chondroitin sulphate
- Vascular plexus - separates P&R layers
1-3 produced by fibroblasts
What are the skin appendages?
Hair follicles - inner & outer root sheath, anagen (growth 75%) telogen (resting) phases Eccrine glands (sweat, odourless, secrete by exocytosis) Apocrine glands (axilla, groin, thicker secretions, body odour, hidradenitis suppurativa → infection Sebaceous glands - holocrine glands, drain into pilosebaceous units
What do these histological terms mean? Acanthosis Papillomatosis Hyperkeratosis Parakeratosis
- Acanthosis → hyperplasia of the epithelium
- Papillomatosis → ↑ depth of the corrugations at the junction between epidermis and dermis
- Hyperkeratosis → ↑ thickness of the keratin layer
- Parakeratosis → nucleated cells at the skin surface.
What is the blood supply to the skin?
Deep vessels (aorta → trunk, limbs, H&N)
Interconnecting vessels
- fasciocutaneous (septocutaneous) - limbs
- musculocutaneous - torso
Plexuses - anastomoses b/t cutaneous arteries
- subepidermal
- dermal
- subdermal → main supply of skin
- subcutaneous → from MC, esp torso
- prefascial → larger plexus esp limbs (FC)
- subfascial
What is a perforator?
What is the difference b/t a true anastomosis and choke vessel?
Perforator = direct branch from system of A&Vs whose primary function is to perfuse the deeper structures, muscles and bones
True anastomosis = no change in calibre
Choke vessel = reduced calibre vessels which dilate to restore blood flow to an area of ischaemia
What is an angiosome?
An angiosome is a composite block of tissue supplied by a named artery & its venae comitantes
adjacent angiosomes are connected by true anastomoses or choke vessels
junctional zones tend to occur within a muscle
Who described angiosomes and who extended the work?
What are the characteristics of arteries?
Manchot 1889
Salmon 1930s
Taylor and Palmer BJPS 1987
Arterial Characteristics (Taylor)
Vessels
- travel with nerves
- obey law of equilibrium (if sources vessel is small, adjacent source vessel is large)
- travel from fixed to mobile tissue
- have a fixed destination but varied origin
- size and orientation is a product of growth.
What is the anatomical, dynamic and potential territories of flaps?
Anatomical Territory = area in which the vessel branches ramify before anastomosing with adjacent vessels. (choke vessels join these anatomical areas together)
Dynamic Territory = area which staining extends into after IV fluorescein – via choke vessels.
Potential Territory = area that can be included in a flap if it is delayed
e.g. TRAM: zone 1 = anatomical, 2&3 = dynamic, 4 = potential
What is the delay phenomenon?
Delay = expansion of the vascular territory of a flap to achieve its potential vascular territory
Conditions flap to survive with reduced blood flow
e.g. pedicled TRAMs - DIEP divided 2/52 before, forehead flap
What is the possible mechanism of delay phenomenon? THAIS!
- increased axiality of blood flow
- tolerance to ischaemia
- sympathectomy → vasodilatation theory
- interflap shunting hypothesis (sympathectomy dilates the AVAs more than pre-capillary sphincters →↑non-nutritive blood flow bypassing cap bed). A greater length of flap will survive at 2nd stage as there are fewer sympathetics to cut and so will be less reduction in non-nutritive flow.
- hyperadrenergic state (surgery causes ↑ tissue conc of vasoconstrictors adrenaline and noradrenaline which gradually normalises. 2nd op vasoconstrictors ↑ again but less vasoconstriction occurs)
Unifying theory - all of above! (Pearl 1981)
Describe the microcirculation in the skin
- Terminal arterioles (reticular dermis)
- Precapillary sphincters regulate blood flow into capillary network (thermoregulation)
- Arteriovenous anastomoses (AVA) connect arterioles to efferent veins and bypass capillary network to radiate heat
How is blood flow controlled?
- Myogenic theory
↑ intraluminal pressure → constriction of vessels, ↓ pressure → dilatation (explains hyperaemia after tourniquet) - Neural innervation
arterioles, AVA & precapillary sphincters are sympathetically innervated - Humoral factors
adr & NA - constrict, histamine & bradykinin, acidosis, ↓O2, ↑CO2 - vasodilate - Temp
What is the blood supply of the head and neck skin?
Below zygomatic arch (mainly dermal subdermal)
- facial artery
- transverse facial artery (from parotid)
- infraorbital
- mental
Above zygomatic arch - supraorbital - supratrochear - sup temporal vessels b/t skin & galea
Neck
- facial artery (submental br)
- traverse cervical artery
What is the blood supply of the trunk skin?
Perforators - emerge from muscle / aponeurosis and run in sup fascia
Segmental intercostals - ant, lat, post
Chest - ant & lat ic (deltopectoral flap)
Back - post ic perforators, circumflex scapula branches (scapular flaps), muscle perforators (LD, pec major, trapezius)
sup circ iliac - groin flap
sup epigastric - hypogastric flap
What is the blood supply of the upper limb skin?
Forearm - prefascial & subfascial plexuses, supplied by septocutaneous perforators
Upper arm
- posterior descending br of profunda brachii - runs in lateral intermuscular septum (attached to humerus, separates BR (dist) and Biceps (prox) from triceps)
Forearm
- short perforators (vessels close to skin)
- radial artery perforators → IM septum b/t BR & PT (prox) & FCR (dist)
- ulnar artery perforators → IMS b/t FCU & FDS
What is the blood supply of the lower limb skin?
Ant tibial perforators → row along ant border / subcut surface of tibia b/t anterior tibial muscles & peroneal compartment.
Peroneal perforators → b/t peroneal and post compartments.
Posterior tibial branches → in IM septum b/t FDL and Soleus emerging in a line behind post border of subcut surface of tibia, and also others pass backwards through muscles of soleus and gastroc to emerge midway b/t 2 bellies of gastroc and also midway b/t midline & lat & med margins of gastroc.
How are flaps classified?
Can be classified in 5 ways (5 C’s)
- Circulation → random or axial (Direct, Fasciocutaneous, Musculocutaneous, Venous)
- Composition → Cutaneous, Fasciocutaneous, Fascial, Musculocutaneous, Muscle, Osseocutaneous, Osseous
- Contiguity → Local, Regional, Distant (Pedicled, Free)
- Contour → Advancement, Transposition, Rotation, Interpolation, Crane
- Conditioning→ Delay
How are flaps classified by circulation?
Random
- no directional blood supply
- relies on dermal & subdermal plexi
Axial
- flap supplied by vessels running longitudinally within it
1. direct cutaneous
2. fasciocutaneous
3. septocutaneous (im septum)
4. musculocutaneous
5. venous
What are direct cutaneous skin flaps? Give some examples
- named axial arteries
e. g. deltopectoral (IMA perforators), groin (superficial external iliac)
Who classified fasciocutaneous flaps?
What are you are familiar with?
Type A - supplied by multiple FC perforators that enter at the base of the flap and extend throughout its longitudinal length. Can be based proximally/ distally/ as island. e.g. Ponten flap
Type B - single FC perforator & is fairly consistent. This flap may be isolated as an island flap or used as a free flap.
e.g. parascapular, scapular, some lower limb perforator flaps (?propeller)
Type C - based on multiple small perforators that run along a fascial septum. Supplying artery is included with flap. May be based proximally/ distally/ as free flap. e.g. RFF, lat arm flap
Type D is an osteomyocutaneous flap = Type C + adjacent muscle & bone. May be based proximally / distally on a pedicle / free flap e.g. RFF w radius, lat arm w humerus
Cormak and Lamberty also introduced a new classification based on clinical applications. Type A has a fascial plexus, Type B has a single perforator, and Type C has multiple perforators and a segmental source artery.
What is Mathes and Nahai’s classification of fasciocutaneous flaps?
Type A - direct cutaneous pedicle to fascia
Type B - septocutaneous perforator
Type C - w perforators from musculocutaneous source
Name a classification for musculocutaneous (muscle) flaps
Mathes and Nahai 1981 PRS
Type I - One dominant pedicle
o TFL, Gastroc, Rectus Femoris, Abd Dig Min
Type II - One dominant + minors
o Gracilis, Soleus, Trapezius, Peronei, Biceps Fem, Semitend, Brachioradialis, Abductor Digit Quinti, Abductor Hallucis.
- Delaying by ligating the dominant vessel improves survival.
- A portion of muscle can be based on a minor pedicle but whole muscle will not survive.
Type III - Two dominant pedicles
o Pec Minor, Serratus, Rectus Abdominus, Temporalis, Gluteus maximus.
- good for dividing up eg pec minor for facial reannimation (slips to orbit, slips to angle of mouth). TRAMS for breast.
Type IV - Segmental
o sartorius, Tib Ant, EDL, EHL, FDL, FHL.
- Muscle survives if only proximal vessel divided (sartorius switch).
Type V - One dominant + segmental
o L Dorsi, Pec Major.
- Will survive if dominant pedicle divided but segmental supply preserved (Pec Major turnover flap for sternum)
