The major direct cutaneous vessels identified in the cat include the omocervical, thoracodorsal, deep circumflex iliac, and caudal superficial epigastric arteries. Axial pattern skin flaps based on the thoracodorsal and caudal superficial epigastric arteries have been developed in cats. Rotation of these flaps as islands allows skin coverage to the carpus and metatarsus, respectively. The thoracodorsal and caudal superficial epigastric flaps provide a practical, one-step option in the reconstruction of large skin defects involving the distal extremities of cats. MICROSURGERY

12:125-129

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AXIAL PATTERN SKIN FLAPS IN CATS AUDREY M. REMEDIOS, D.V.M., M.V.Sc., MICHAEL S. BAUER, D.V.M., C. VAUGHAN A. BOWEN, M.B., Ch.B., and J. DAVID FOWLER, D.V.M., M.V.Sc.

M a j o r skin defects in animals, arising from trauma or sur- a large area of skin, direct cutaneous arteries allow the gical excision, can present problems in reconstruction. development of axial pattern flaps of considerable length Management options include primary closure, second in- without vascular compromise or delay In comparison, the primary cutaneous circulation in tention healing, skin grafts, and skin flaps.'-6 Primary closure of large wounds is often possible if confined to areas of man is derived from musculocutaneous arteries. Running loose skin over thorax, flank, or abdomen. With the ex- perpendicular to the skin, musculocutaneous arteries supply tremities, primary closure may not be feasible, and skin a relatively small area (Fig. 1). Random or cutaneous flaps, on musculocutaneous arteries, are analogous to defects are frequently left to heal by second i n t e n t i ~ n . ~ dependent '~ Disadvantages of second intention healing include fragile subdermal plexus flaps in loose-skinned animals. Axial pattern flaps were initially described in the dog.5 epithelial surfaces, excessive wound contracture, prolonged healing time, and n ~ n h e a l i n g . ~Skin - ~ grafts may be used The major canine direct cutaneous vessels include the omobut require optimal conditions of the recipient bed for cervical, thoracodorsal, deep circumflex iliac, and caudal survival. l o Skin flaps that retain an intact circulation from superficial epigastric arteries. Recently, canine axial pattern the donor bed are associated with fewer complications than flaps have been developed based on the superficial brachial artery and the genicular branch of the saphenous artery.'4315 second intention healing or grafts.6 Skin flaps are classified according to blood supply as Mapping and identification of direct cutaneous vessels has subdermal plexus or axial pattern.6 Subdermal plexus flaps been reported in the cat.16 This paper reviews the developare dependent on terminal branches of the cutaneous circu- ment and application of feline axial pattern skin flaps. lation, whereas axial pattern flaps are based on direct cutaneous arteries. Axial pattern flaps have a 50% greater DEVELOPMENT OF SKIN FLAPS survival area than subdermal plexus flaps of comparable Nonselective angiography and gross dissection were size.4,s ,8 performed on cadavers to delineate the major direct cutaIn cats and other loose-skinned animals, the primary neous arteries in the cat.'6 Vessels identified with nonsecutaneous vascular supply is from direct cutaneous ar- lective angiography included the omocervical, thoracodorteries. ' I Arising from perforator arteries, the direct cutane- sal, deep circumflex iliac, and caudal superficial epigastric ous vessels travel subdermally parallel to the skin supplying arteries. On gross dissection, the omocervical artery was the deep, middle, and superficial plexus (Fig. 1). Sustaining found to originate between the caudal aspect of the

From the Department of Veterinary Anesthesiology, Radiology and Surgery, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Address reprint requests to Audrey M. Remedios, DVM, Department of Veterinary Anesthesiology, Radiology and Surgery, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N OWO. 0 1991 Wiley-Liss, Inc.

omotransversarius muscle and the cranial aspect of the trapezius muscle, approximately 2 cm dorsal to the acromion. The vessel supplied the craniodorsal cervical skin. The thoracodorsal artery emerged at the caudal shoulder depression bounded by the spinous head of the deltoideus muscle cranially, the long head of the triceps muscle ventrally, and the latissimus muscle caudally. The vessel traveled caudodorsally, supplying the skin of the lateral thorax. The deep

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A

B

Figure 1. Schematic representation of the cutaneous vascular supply of cat (A) and human (6)skin. (Reproduced from Daniel RK and Williams HB: The free transfer of skin flaps by microvascular anastomosis: an experimental study and a reappraisal, Plast Reconstr Surg 52:20,1973, with permission of the publisher.)

circumflex iliac artery originated from the aorta and emerged through an aponeurosis of the external abdominal oblique muscle at the ventral aspect of the tuber coxa. The vessel supplied the skin dorsolateral to the sacrum. Arising from the external pudendal artery, the caudal superficial epigastric artery emerged at the inguinal ring and traveled cranially to supply the fourth, third, and second mammary glands and the ventral abdominal skin. Following identification of the direct cutaneous vessels, selective angiography and gross dissection were performed to define vascular territories and anatomic landmarks for development of associated axial pattern skin flaps. l 6 Small vessel diameters (0.4 mm) precluded cannulation of the omocervical and deep circumflex iliac arteries. Although these vessels could potentially be used to develop axial pattern flaps, their vascular territories could not be determined without selective angiography. Direct injection of the thoracodorsal and caudal superficial epigastric arteries allowed accurate assessment of vascular boundaries (Figs. 2,3). The cranial border of the skin supplied by the thoracodorsal artery was the scapular spine. The caudal border originated at a point twice the distance from the acromion to the caudal shoulder depression and was defined by a line parallel to the scapular spine. The ventral limit was defined by a line extending from the acromion caudally to the axilla. The dorsal border was formed by the midline (Fig. 4).The cranial extent of the caudal superficial epigastric artery was marked by the second nipple. The caudal border was marked by the inguinal ring. The lateral limit extended from a point twice the distance from the nipple to the ven-

tral midline. The ventral midline formed tht: medial limit (Fig. 5 ) . Based on the established anatomic landmarks of the thoracodorsal and caudal superficial epigastric arteries, their associated flaps were elevated as islands and sutured back onto the donor bed in an orthotopic fashion Skin defects were then created in the forelimb extending from the lateral aspect of the midhumerus to the carpus and on the medial aspect of the hindlimb extending from inguinal area to the metatarsus. The thoracodorsal and caudal superficial epigastric flaps were elevated as islands, rotated 180°, and sutured onto the created defects in a heterotopic fashion (Figs. 6,7). Survival of all flaps, 14 days after surgery, was excellent. All caudal superficial epigastric flaps survived 100%. Survivals of orthotopic and heterotopic thoracodorsal flaps were 98% (necrosis occurred at the distal tips). APPLICATION OF SKIN FLAPS

The primary application of the feline thoracodorsal and caudal superficial epigastric flaps is in reconstruction of distal limb skin wounds. Unlike the case with areas with redundant surrounding skin, management of cutaneous defects on the distal limbs is dictated by the paucity of loose skin. In that primary closure is not possible with large areas of skin loss, second intention healing is often relied upon.5 Defects greater than half the circumference of the limb are subjected to prolonged healing times or nonhealing. l4 Rotation of the thoracodorsal and caudal superficial epigastric flaps provides coverage to the distal aspects of the limbs. l 6 The thoracodorsal flap extends to the carpus, ,and the caudal

Axial Pattern Skin Flaps in Cats

Figure 2. Selective angiography of the thoracodorsal artery (arrows).

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Figure 4. Landmarks of the thoracodorsal axial pattern flap include 8, cranial limit identified as the scapular spine; C, caudal border parallel with the scapular spine originating at a point twice the distance from the acromion to the caudal shoulder depression; D,ventral limit extended from the acromion to the axilla; €, dorsal border delineated by the midline. A. caudal shoulder depression.

0

0

D 0

Figure 3. Selective angiography of the caudal superficial epigastric artery (arrows).

superficial epigastric flap provides coverage to the metatarsus. In comparable flaps developed in the dog, the thoracodorsal flap reaches the elbow, and the caudal superficial epigastric flap covers to the The more distal limb coverage in the cat vs. the dog can be attributed to the extremely pliable skin and similarity in body size and limb length from cat to cat. The direction of fur growth on the rotated thoracodorsal and caudal superficial epigastric flaps differs from that on the adjacent normal skin. Fur length and color pattern may

Figure 5. Landmarks of the caudal superficial epigastric flap include B, cranial limit marked by the second nipple; C, caudal border formed by a line between the inguinal rings; 0,medial limit defined by the ventral midline; €, lateral limit extended from a point twice the distance from the nipple to the ventral midline. A, inguinal ring.

also differ depending on the characteristics of the donor and recipient sites. These cosmetic alterations are of minimal importance in veterinary surgery. l7 CLINICAL CASES

Use of the caudal superficial epigastric axial pattern flap is demonstrated in two clinical cases. A 4-year-old female, spayed, domestic short-haired cat was presented to the Western College of Veterinary Medicine with extensive

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Figure 6. The thoracodorsal island flap was rotated 180" and sutured onto the created defect. FL, forelimb. Figure 7. The caudal superficial epigastric island flap was rotated 780"and sutured onto the created defect. HL, hindlimb. Figure 8. Case 7. The skin defect extended from the left lateral thigh to midtibia. C, crus; T, tarsus.

Figure 9. Case 1. The right caudal superficial epigastricaxial pattern flap was raised and rotated to cover the entire left hindlimb defect. C, crus; T tarsus. Figure 70. Case 2. A degloving injury involving the circumferenceof the right hind limb extending from the proximal femur to the digits. F, femur; T, tarsus. Figure 7 7. Case 2.The right caudal superficial epig#astricaxial pattern flap is raised and encircles the entire hind limb from the midfemur to the metatarsus.

Axial Pattern Skin Flaps in Cats

skin loss involving the left lateral thoracic and flank area and the left lateral thigh and crus extending to midtibia. A severely comminuted fracture of the proximal right femur was also present. Initial surgery involved surgical debridement of the skin wounds, primary closure of the lateral thoracic and flank wounds, and amputation of the right hindlimb. The large skin defect on the lateral left hindlimb was managed as an open wound until granulation tissue was present and local infection was controlled (Fig. 8). Reconstructive surgery was then performed to close the hindlimb wound. As the adjacent left thoracic and flank wound was closed primarily, under marked skin tension, the right caudal superficial epigastric axial pattern flap was raised to avoid complications of donor bed closure. The flap was then rotated to cover the entire left hindlimb defect (Fig. 9). Survival of the skin flap was excellent. The second case involved a 1-year-old female, spayed, domestic short-haired cat with a circumferential degloving injury of the right hindlimb extending from the proximal femur to the digits (Fig. 10). Following open wound management to encourage granulation tissue, the right caudal superficial epigastric flap was elevated. The flap was rotated to encircle the limb from midfemur to the metatarsus (Fig. 1 1). The proximal femur and digits were covered with mesh expansion skin grafts. Skin flap survival was excellent.

these flaps as islands affords coverage to the carpus and metatarsus.

REFERENCES I . Ross G E Clinical canine skin grafting. J Am Vet Med Assoc 12: 1759-1765, 1968. 2. Swaim SF: Principles of mesh skin grafting. Comp Contin Ed Prucr Vet 4:194-200, 1982. 3. Keefe F: Skin grafting in acat. J A m VetMedAssoc 108:43-48, 1946. 4. Pavletic MM: Caudal superficial epigastric arterial pedicle grafts in the dog. Vet Surg 9:103-107, 1980. 5 . Pavletic MM: Canine axial pattern flaps, using the omocervical, thoracodorsal and deep circumflex iliac direct cutaneous arteries. Am J Vet Res 42:391-406, 1981. 6. Swaim S F Skin flaps, in Swaim SF (ed): Surgery of Traumarized

7. 8.

9. 10.

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In cats and other loose-skinned animals, the primary cutaneous vascular supply is from direct cutaneous arteries. Based on these vessels, axial pattern flaps can be developed over large areas of skin without vascular compromise. The thoracodorsal and caudal superficial epigastric axial pattern flaps described in the cat are practical procedures in the management of skin defects on the distal limbs. Rotation of

Skin: Management and Reconstruction in the Dog and Cat. Philadelphia, W.B. Saunders, 1980, pp 321-394. Johnston DE: Repair of skin loss in the foot by means of a double pedicled abdominal flap. J Am Anim Hosp Assoc 12:593-596, 1976. Pope ER, Swaim S F Chronic elbow ulceration repair utilizing an axial pattern flap based on the thoracodorsal artery. J Am Anim Hosp ASSOC22~88-93, 1986. Pavletic MM: Reverse saphenous conduit flap in the dog. J Am Anim Hosp Assoc 182:380-389, 1983. Yturraspe DJ, Creed JE, Schwach RP: Thoracic pedicle skin flap for repair of lower limb wounds in dogs and cats. J Am Anim Hosp Assoc

12:581-587, 1976. 11. Daniel RK, Williams HB: The free transfer of skin flaps by rnicrovas-

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cular anastomosis: An experimental study and a reappraisal. Plast Reconsrr Surg 52:16-30, 1973. Pavletic MM: Vascular supply to the skin of the dog: A review. Ver Surg 9:77-80, 1980. Guba AM: Study of the delay phenomena in axial pattern flaps in pigs. Plast Reconstr Surg 63:550-554, 1979. Henney LH, Pavletic MM: Axial pattern flap based on superficial brachial artery in the dog. Ver Surg 17:311-317, 1988. Kostolich M, Pavletic MM: Axial pattern flap based on the genicular branch of the saphenous artery in the dog. Vet Surg 16:217-222, 1987. Remedios AM, Bauer MS, Bowen CVA: Thoracodorsal and caudal superficial epigastric axial pattern skin flaps in cats. Vet Surg (in press). Paveltic MM: Surgery of the skin and management of wounds, in Sherding RG (ed): The Cat: Diseuses and Clinical Management. New York, Churchill Livingstone, 1989, pp 1601-1629.

Axial pattern skin flaps in cats.

The major direct cutaneous vessels identified in the cat include the omocervical, thoracodorsal, deep circumflex iliac, and caudal superficial epigast...
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