Ch 79 - Axial Pattern and Myocutaneous Flaps

Question 1

How much can you rotate an axial pattern flap?

Answer 1

180 degrees

Question 2

What are the two braod options when elevating an axial pattern flap?

Answer 2

• Penisular flap - Intact skin at its base
• Island flap - Skin incised along all edges and flap is rotated around vascular base

Question 3

What is a composite flap?

Answer 3

An axial pattern flap composed of skin as well as muscle, bone or cartilage

Question 4

What is the reported overall survival rate of axial pattern flaps?

Answer 4

87 - 100%

Question 5

List some differences between cats and dogs in regard to skin anatomy and wound healing

Answer 5

• Dogs have a much higher density of tertiary and higher order vessels than cats (less cutaneous perfusion to the uninjured skin of cats)
• Granulation tissues takes half as long to form in cats and begins at the periphery
• Removal of SQ reduces the rate of epithelialisation, especially in cats (recommended to preserve SQ with harvesting axial pattern flaps in cats)

Question 6

Name the following axial pattern flaps

Answer 6

• 1 = Caudal auricular
• 2 = Omocervical
• 3 = Thoracodorsal
• 4 = Caudal superficial epigastric
• 5 = Lateral genicular
• 6 = Deep circumflex iliac
• 7 = Lateral caudal
• 8 = Superficial brachial

Question 7

Describe the Omocervical axila pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 7

• Based on superficial cervical branch of the omocervical artery and vein (originates at level of prescap LN and courses cranially)
• Caudal incision from acromion dorsally along scapular spine
• Cranial incision parallel and equidistant from cranial edge of scapula
• Can extend to contralateral scapulohumeral joint

Potential uses: Face, ear, cervical, shoulder, axillary defects

Question 8

Describe the Thoracodorsal axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 8

• Based on cutaneous branch of thoracodorsal artery and vein
• Cranial incision from acromion dorsally along scapular spine
• Caudal incision parallel and equidistant from caudal shoulder depression
• Can extend to contralateral scapulohumeral joint
• Elevated under cutaneous trunci muscle

Potential uses: Thoracic, forelimb, shoulder, axillary defects

Question 9

Describe the dorsal deep circumflex iliac axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 9

• Based on deep circumflex iliac artery and vein which exit lateral abdominal wall cranioventral to wing of ilium and divides into dorsal and ventral branch
• Base of flap at ventral extent of cranial edge of ilium
• Caudal incision midway between wing of ilium and greater trochanter extending dorsally
• Cranial incision parallel and equidistant from wing of ilium
• Can be extended to contralateral paralumbar or flank fold
• Elevated below cutaneous trunci muscle

Potential uses: ipsilateral flank, lateral lumbar, pelvic lateromedial thigh, greater trochnater defects

Question 10

Describe the ventral deep circumflex axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 10

• Based on the ventral branch, exiting at same point as dorsal branch but extending down lateral flank and craniolateral thigh
• Landmarks for base and width identical to dorsal
• Caudal incison runs ventrally in a line parallel to cranial border of femoral shaft
• Cranial incision parallel
• Can extend to proximal edge of patella

Potential uses: Lateral abdominal wall, pelvic, sacral

Question 11

Describe the caudal superficial epigastric axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 11

• External pudendal artery and vein exit caudal inguinal canal, provide ventral brance to labia/scrotum and arches cranially to form caudal superficial epigastric
• Ventral midline incision
• Parallel incision laterally and equidistant to teats
• Can extend cranially to include 2nd mammary gland
• Elevated below supramammarius muscle

Potential uses: Caudal abdominal, flank, inguinal, preputial, perineal, thigh, stifle defects

90% of dogs have complete flap survival

Question 12

Describe the cranial superficial epigastric axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 12

• Based on short cutaneous braches of cranial superficial epigastric. Artery exits through rectus abdominis caudoventral to thoracic cage and 2-4cm lateral to midline
• Ventral midline incision from just caudal to thoracic cage extending caudally
• Lateral parallel incision equidistant from 3rd teat
• Can extend to include mammary 3, 4 and sometimes 5
• Elevated below panniculus muscle

Potential uses: Sternal defects

Question 13

Describe the angularis oris axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 13

• Based on angularis oris artery and vein with branches of inferior and superior labial arteries
• Based at labial commisure
• Dorsal incision parallel to ventral zygomatic arch to level of vertical ear canal
• Ventral incision parallel with ventral aspect of mandibular ramus
• Can extend to wing of atlas but more commonly to vertical ear canal
• Can also be created as a noncutaneous rectangular island flap based on the buccal mucosa

Potential uses: Palatal, facial, nasal defects

Question 14

What important underlying structures may be encountered when elevating the angularis oris axial parrern flap?

Answer 14

• Facial nerve (dorsal, ventral and auriculopalpebral branches)
• Auriculotemporal nerve
• Parotid salivary duct
• facial vein

Question 15

Describe the superficial temporal axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 15

• Based on superficial temporal artery
• Based on caudal aspect of zygomatic arch caudally and lateral aspect of orbital rim cranially
• Extends dorsally to maximal length at dorsal aspect of contralateral orbital rim
• Thin frontalis muscle elevated with flap

Potential uses: Maxillofacial, eyelid defects

Question 16

What nerve may need to be transected during elevation of superficial temporal axial pattern flap?

Answer 16

• Rostral auricular nerve - does not effect eyelid function

Question 17

Describe the caudal auricular axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 17

• Based on sternocleidomastoideus branches of caudal auricular artery and vein
• Based at palpable depression between vertical ear canal and wing of atlas
• Flap is centered over wing of atlas with dorsal and ventral incisions running caudally and parallel to each other
• Maxiumu length to spine of scapula
• Platysma muscle is elevated with the flap
• In cats, the dorsal incision is closer to dorsal midline

Potential uses: neck, facial, ear, dorsal head defects

Question 18

Describe the superficial brachial axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 18

• Based on superfical brachial branch of brachial artery
• Base centered over proximal 1/3 of flexor surface of elbow
• Lateral and medial incision lateral to each other and to the shaft of the humerus
• Maximum length distal to greater tubercle
• Fragile and easily fails, use as a last resort option

Potential uses: Antebrachial, elbow defects

Question 19

Describe the genicular axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 19

• Based on the genicular braches of the saphenous artery and saphenous vein
• Genicular artery extends cranially over the medial aspect of the stifle and terminated over its craniolateral surface
• Base of flap located 1cm proximal to patella and 1.5cm distal to tibial tuberosity
• Incisions extend proximally, parallel to femoral shaft, converging to make base 2cm wider than tip
• Maximum length distal to greater trochanter

Potential uses: medial stifle or tibial defects

Question 20

What is the reverse saphenous conduit flap dependant on?

Answer 20

Reverse flow through vascular anastomoses between branches of the cranial tibial and saphenous arteries and between tributaries of the medial and lateral saphenous veins

Question 21

Describe the lateral caudal axial pattern flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 21

• Based on the left and right lateral caudal arteries and veins (branches of caudal gluteal)
• Cranial border of flap is horizontal line where tail attaches to body
• Dorsal or ventral midline incision
• Elevated deep to dorsal fascia (tricky)
• Tail amputated between caudal vertebrae 2-3
• Can be splint along dorsal midline to form 2 flaps

Question 22

Describe the latissimus dorsi myocutaneous flap
what vessel is it base one, anatomical landmarks, maximum length, potential uses

Answer 22

• Based on thoracodorsal artery
• Direct cutanous artery through craniodorsal portion of latissiumus to the skin just dorsal to the scapula
• Craniodorsal aspect is level with acromion and caudal to triceps m. Incised in a caudodorsal direction to head of 13th rib
• Ventral border starts at thoracic limb skin fold at a point level with lower third of the humerus. Extends parallel to 13th rib
• Dissection deep to latissimus dorsi

Potential uses: Defects which require more bulky reconstruction such as thoracic wall

Question 23

What is the reported outcome of thoracodorsal axial pattern flaps?

Answer 23

• Experimental 98%
• Clinically 70% partial tip necrosis

Question 24

What is the reported outcome of caudal superficial epigastric flaps?

Answer 24

• 90% dogs have complete flap survival
• 30% complication rate (seroma, brusining, oedema, drainage, dehiscense)

Question 25

What is the reported outcome of the superficial temporal axial pattern flap?

Answer 25

• Mean flap area survival experimentally 93 - 99%
• (decreased to 69% if extended to contralateral zygomatic arch - not recommended)

Question 26

What is the reported mean flap survival of the caudal auricular axial pattern flap?

Answer 26

85%

Question 27

What type of vascular pattern does the latissimus dorsi have?
What does this mean?

Answer 27

• Type V vascular pattern
• Has a single dominant vascular pedicle and a segmental vascular pedicle
• Portions of a muscle with this vascular pattern will survive if the transfer is based on the dominant vascular pedicle (thoracodorsal artery for latissimus dorsi)