Chapter 79 Axial Pattern and Myocutaneous Flaps

Question 1

Name the axial pattern flaps and the artery that they’re based on:

Answer 1

1. Caudal auricular - Sternocleidomastoideus branches of caudal auricular a.
2. Omocervical - Cervical cutaneous branch of omocervical a.
3. Thoracodorsal - Cutaneous branch of thoracodorsal a.
4. Caudal superficial epigastric - Caudal superficial epigastric a. (branches from pudendal a.)
5. Lateral genicular - Genicular branches of saphenous a.
6. Deep circumflex iliac (dorsal and ventral) - Deep circumflex iliac a (dorsal or ventral branch).
7. Lateral caudal (inset) -R and L lateral caudal a. (branches of caudal gluteal a.)
8. Superficial brachial (inset) - Superficial brachial a. (branch of brachial a.)
9. Superficial temporal - superficial temporal a.
10. Angularis oris - Angularis oris a. (branch of facial a.). Blood supply also includes neighbouring smaller inferior and superior labial arteries.

(Cranial superficial epigastric flap not shown. Based on short cutaneous branches of cranial superficial epigastric a. (branch of internal thoracic a.))

Question 2

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Angularis oris

Answer 2

Considerations:

• Is a myocutaneous flap, or can be developed as a buccal only flap.
• Careful dissection facial n., parotid salivary duct and facial vein underlying

Complications:

• Necrosis, billowing if used for maxilectomy (resolves in 10d)

Question 3

What are the advantages and disadvantages of island vs peninsular flap?

Answer 3

Peninsular flap is attached at it’s base so affords vessels some protection, but results in dog ear

Question 4

List some advantages of axial pattern flaps over other methods of wound closure.

Some disadvantages

Answer 4

• Can close large defect
• Early closure
• Coverage of suboptimal areas e.g. bone/tendon
• Avoids two stage procedure to enhance survival rates
• Excellent survival rates
• Cosmeisis (different fur)
• Limited reach to distal limbs
• Variable regional vascularity

Question 5

What is the overall survival rate of axial pattern flaps?

Answer 5

87-100%

Question 6

What is a composite/compund flap?

Answer 6

Flaps that include muscle, bone or cartilage with overlying skin

Question 7

List 4 differences between dog skin and cat skin

Answer 7

Cats:

• Less cutaneous perfusion in uninjured skin. (In primarily sutured skin, cats had lower cutaneous perfusion for first week, followed by more rapid gain –> no difference by 2 weeks)
• Skin takes longer to heal
• Lower strength at closure and 1 week
• Slower rate of granulation/epithelialisation/contraction

Question 8

What is the cold/warm pack recommendation for post-op flaps?

Answer 8

Cool packs (15-20º) for first 3d then warm for 3-5d

Question 9

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Superficial temporal

Answer 9

Considerations:

• Dont extend further than middle or contralateral dorsal orbital rim.
• Elevate frontalis muscle with the flap (lise superfiical to temporalis muscle)
• Usually transect superficial branch of rostral auricular nerve

Complications:

• Experimentally 93% area survival in dogs, 99% in cats (less if extended to contralateral zygomatic arch therefore limit to contralateral dorsal orbit!)

Question 10

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Caudal auricular

Answer 10

Considerations:

• In dogs, flap width is central 1/3rd of dogs lateral profile, in cats dorsal incision is closer to midline.
• Elevate skin and platysma musle together

Complications:

• 85% survival in dogs, cats anecdotally better

Question 11

What type of vasular pattern does latissiumus dorsi muscle have?

Answer 11

Type V i.e. single dominant vascular pedicle

Vascular supply = thoracodorsal artery dorsally, Lateral thoracic arteries supply ventral part.

Question 12

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Omocervical

Answer 12

Considerations:

• Superficial cervical branches of omocervical artery and vein originate at level of prescapular (aka superficial cervical) LN, course craniodorsally to scapula
• Caudally pointing L-shape possible, in which case make distance extended towards contralateral side shorter

Complications:

• Less robust and smaller area cf thoracodorsal flap

Question 13

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Thoracodorsal

Answer 13

Considerations:

• Thoracodorsal a. + v. originate caudal to shoulder at level of acromion. .
• Caudally pointing L-shape possible (in which case shorten distance dissected towards contralateral side)
• Elevate beneath cutaneous trunci
• (reported in conjuntion with omental pedicle for non-healing axillary wounds)

Complications:

• In dogs, mean flap area necrosis 21%
• Partial tip necrosis in 70% of dogs when used for forelimb defects

Question 14

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Superficial brachial

Answer 14

Considerations:

• Very fragile - authors recommend against it’s use
• Base = 33% circumference of brachium, at level of elbow crease (flexor surface).
• Distance limit; should end before greater tubercle.
• Converge donor site incisions proximally to facilitate donor site closure.

Complications:

• Care re vessels!

Question 15

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Deep circumflex iliac

Answer 15

Considerations:

• Deep circumflex iliac a. and v. exit abdo wall cranioventral to winf of ilium. Dorsal (shorter) or ventral branch.
• With dorsal flap, can create cranially facing L-shape (shorten contralateral distance as usual - if not l shaped can extent to contralateral paralumbar or flank fold)
• For ventral branch flap, incise along cranial thigh , extending to proximal patellar edge.

Complications:

• No reports

Question 16

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Cranial superficial epigastric

Answer 16

Considerations:

• Cranial superficial artery and vein exit abdo wall in hypogastric area, caudoventral to thoracic cage, 2-4cm lateral to midline.
• Used for sternal defects.
• Can extend to 4th gland (or in males limit to just cranial to prepuce)
• Distal supply relies on flow through anastomotic vessels (to what was caudal superficial epigastric)

Complications:

• 93% flap survival reported in a dog

Question 17

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Caudal superficial epigastric

Answer 17

Considerations:

• i.e. can’t include gland 1.
• Undermine beneath supramammarius muscle
• Skin stretchers + bilat flap reported in a dog
• Glands will remain functional if FE. Can do concurrent OVE

Complications:

• 90% of dogs have complete flap survival

Question 18

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Lateral caudal

Answer 18

Considerations:

• Vessels sit ventrolateral to coccygeal vertebrae.
• Dissect deep to caudal fascia.
• Limit length to proximal 1/3rd of tail.
• Amputate tail between 2nd and 3rd caudal vertebrae.
• If created dorsal flap can split to allow placement either side of anus.

Complications:

• n/a

Question 19

Name the base and borders of the following flap:

Any other particulars to consider?

Complications?

Genicular

Answer 19

Considerations:

• Diagonal base: 1cm proximal to patella –> 1.5cm distal to tibial tuberosity.
• Converging incisions so base is 2cm wider than tip.
• Terminate before greater trochanter.

Complications:

• 89% mean flap survival in dogs (10-33% necrosis, speculated due to variability in vessels)

Question 20

The reverse saphenous conduit flap is reliant on reverse flow through anastomotic arteries and veins.

Which arteries are involved?

Answer 20

Arterial flow: Reliant of flow through superficial branch of cranial tibial artery –> anastomosis –> reverse flow through cranial branch of saphenous artery.

Venous flow: Reliant on flow from cranial branch of lateral saphenous vein –> anastomosis –> cranial branch of medial saphenous vein.

Question 21

List some pre-op considerations for reverse saphenuos conduit flap.

Outline surgical technique

Answer 21

• Assess flow throguh vessels - angiography recommended
• Incise 33% of circumference at medial thigh, at level with of patella
• Ligate and divide saphenous artery, medial saphenous vein.
• Cranial incision 1cm cranial to cranial branches of saphenous a. and medial saphenous vein. Caudal incison 1 cm caudal to caudal branches of sphenous a. and medial saphenous vein.
• Slightly converging incisions
• Dissect with portion of medail gastrocnemius muscle fascia
• Carefully dissect free branches of tibial nerve.
• May need to ligate + divide peroneal artery and vein to mobilise.
• Stop dissection proximal to anastomoses!

Question 22

What is a common, temporary complication of reverse saphenous conduit flap?

What is flap failure rate?

Answer 22

Congestion due to reverse venous flow.

Complete failure in 17-33% of cases, partial failure in 33-50%.

Question 23

What is the most common reason for flap necrosis?

What is the typical appearance of a flap devoid of arterial supply?

And devoid of venous drainage?

Answer 23

Inadequate blood perfusion.

Lack of arterial supply –> pale flap

Lack of venous drainage –> engorgement and cyanosis.

Usually declared by 6d post-op.

Question 24

List 4 interventions to try to salvage a failing flap:

Answer 24

• Release sutures in areas of tension
• Treat infection if present
• Treat underlying disease e.g perfusion, nutrition etc
• NPWT reported in humans and with rotation flap in a dog (Bristow, JAVMA 2013)

Question 25

What are the anatomical borders of lat dorsi flap?

What is noted post-op if used for thoracic wall recon?

Answer 25

Dorsal incision: Craniodorsal staring point = just caudoventral to acromion to head of 13th rib

Ventral incision: Axillary skin folw level with lower 1/3rd of humerus, parallel to dorsal incision, to reach 13th rib.

DV incision along 13th rib.

–> paradoxical movement with respiration (Halfacree, VetSurg, 2007)

Question 26

The reverse saphenous conduit flap is reliant on reverse flow through anastomotic arteries and veins.

Which arteries are involved?

Answer 26

(Repeat card with different anatomy pic)

Arterial flow: Reliant of flow through superficial branch of cranial tibial artery –> anastomosis –> reverse flow through cranial branch of saphenous artery.

Venous flow: Reliant on flow from cranial branch of lateral saphenous vein –> anastomosis –> cranial branch of medial saphenous vein.