Veterinary Surgery, 21, 6,435-440, 1992
Free Microvascular Transplantation of the Trapezius Musculocutaneous Flap in Dogs DENIS PHILIBERT, DVM, MVetSc, J. DAVID FOWLER,DVM, MVetSc, Diplomate ACVS, and J. BRIAN CLAPSON, NM, FRCS(C)
A musculocutaneousflap based on the prescapular branch of the superficial cervical artery and including the cervical part of the trapezius muscle and overlying skin was transplanted over a defect created on the medial side of the contralateral tibia in four dogs by using microvasculartechnique. The donor and recipient sites in three dogs were examined clinically for 21 days, after which they were examined angiographically and histologically. All dogs were free of lameness by hour 48. Seromas formed at the donor site between days 7 and 15. One vascular pedicle was traumatized at hour 40, and the dog was euthanatized. Three flaps survived with minimal necrosis. Edema of the flaps was severe from days 5 to 11. Angiograms showed complete perfusion of the flaps, and survival was confirmed histologically. Esthetic appearance and function were good in one dog at month 7.
thetic appearance of donor and recipient sites, such as excessive bulk or eventual atr~phy.'.'~ A muscular or musculocutaneous flap should have size and bulk to allow coverage of the defect and should have an expendable f ~ n c t i o n . ~ . It ~ .should " be easily accessible and have a constant dominant vascular upp ply.^.^,'^ If a musculocutaneous flap is used, a sufficient overlying area of skin supplied by a direct cutaneous artery should be a ~ a i l a b l e . * ~The ~ ~ ' ~donor , ' ~ site should be easily closed with minimal m ~ r b i d i t y .Knowledge ~?~ of the location of the motor and sensory nerve entrance and the presence of an osseous temtory are also a d v a n t a g e ~ u s . ~ . ~ Anatomic studies of the vascular supply of the tissue to be transferred provide essential information for the design of simple or composite flaps for clinical use.3,15,19-22 A composite flap based on its dominant vascular pedicle can be raised and transplanted ~ a f e l y . ~ , ' The ~ . ~ vascular ~,~' temtory of the prescapular branch of the superficial cervical artery, which includes the cervical part of the trapezius muscle, has been de~cribed.'~ The purpose of this study is to test the viability of a musculocutaneous flap consisting of the cervical part of the trapezius muscle and overlying skin transplanted to a defect created on the me-
after trzuma, F surgical procedures, radiation therapy, or congenital defects can be difficult. When simpler methods are not UNCTIONALTISSUERECONSTRUCTION
appropriate, free microvascular transplantation of tissue should be considered because it provides soft-tissue coverage in a one-stage procedure.'-5 Muscle or compound muscle flaps provide bulk and protection for deep defects and are malleable, reliable, and easily available.2 Because of their rich blood supply, muscle and compound muscle flaps are an ideal bed for skin grafts and are resistant to infecti~n.~?' Muscle flaps increase oxygen tension in a wound and are believed to carry body defense mechanisms via their rich perfusion.8 When combined with aggessive debridement and tissue stabilization, their efficacy in prevention or treatment of osteomyelitis is well documented experimentally and c l i n i ~ a l l y . ~ ~The ~ ~ ~superiority -' of muscle flaps over skin alone is well documented."g8 Coverage of bone with muscle helps establish a periosteal blood supply in the early phase of bone It increases periosteal new bone formation, decreases the risk of wound sepsis,6 and provides a source for revascularization of devascularized bone fragment^.^ The major disadvantages of muscle flaps are associated with the es-
'
~
~
~~
From the Departmentof Vetennary Anesthesiology, Radiologyand Surgery, Western College of Veterinary Medicine, Universityof Saskatchewan, Saskatoon, Saskatchewan, Canada Supported by the Companion Animal Health Fund, Western College of Veterinary Medicine Reprint requests Denis Philibert, DVM, MVetSc, Western College of Vetennary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N-OW0
435
TRANSPLANTATION OF TRAPEZIUS FLAP
Fig. 1. Trapezius musculocutaneous flap. The broken line indicates the skin incision in relation to the direct cutaneous artery (D), the scapula, and the wing of the atlas (A).
dial side of the tibia with microvascular technique, and to evaluate donor site morbidity. Materials and Methods Distant transfer of the cervical part of the trapezius musculocutaneous flap by microvascular anastomosis was performed in four healthy adult male mongrel dogs weighing 17 to 22.5 kg. All procedures were approved by the Animal Care Committee of the University of Saskatchewan and conformed to the Guide to the Care and Use of Experimental Animals by the Canadian Council on Animal Care. All dogs were premedicated with acepromazine (0.05 mg/kg intramuscularly [IM]), and anesthesia was induced with sodium thiamylal (10 to 15 mg/ kg intravenously [IV]) and maintained with halothane and oxygen. Oxymorphone (0. 1 mg/kg IM) was administered as required for analgesia after the surgery. The side of flap elevation was assigned randomly. A curved skin incision was directed dorsally and cranially from the distal third of the spine of the scapula to approximately 5 cm caudal to the wing of the atlas. The arc extended as far dorsally as 2 cm from the dorsal midline. A ventrally curved incision was made between the same two points, taking care to preserve the region where the direct cutaneous artery supplying the skin emerged (Fig. 1). The dorsal part of the cervical part of the trapezius muscle was elevated and sutured to the overlying skin with a few simple interrupted sutures of 3-0 polydioxanone.* The caudodorsal tip of the cervical part of the trapezius muscle was left in situ. The accessory nerve was severed at the caudodorsal border of the cervical part of the trapezius muscle, as it exited the muscle. The muscle
* PDS 11. Ethicon, Somerville. New Jersey.
was transected about 5 mm from its insertion on the scapular spine. Branches of the prescapular branch of the superficial cervical vascular pedicle penetrating the deep musculature were ligated. Dissection was continued between the cervical part of the trapezius and the cleidocervicalis and omotransversarius muscles, keeping the dissection close to the omotransversarius and cleidocervicalis muscles to avoid damaging vascular branches to the cervical part of the trapezius muscle and to preserve the vascular pedicle at the junction of those three muscles. The accessory nerve was severed at its entrance to the cervical part of the trapezius muscle. The cervical part of the trapezius muscle was sutured to the skin flap ventrally. Branches of the prescapular branch of the superficial cervical vascular pedicle, proximal to the branches going to the skin and cervical part of the trapezius muscle, were ligated and divided up to the level of the acromial branch ofthe superficial cervical artery (Fig. 2). The pedicle length was measured between the first branches to the cervical part of the trapezius muscle and the acromial branch of the superficial cervical artery. The pedicle was ligated and transected just distal to the acromial branch. Electrocautery and vascular clipst were used for hemostasis. A %inch latex drain$ exiting at the level of the greater tubercule of the humerus was inserted. Subcutaneous and cutaneous tissues at the donor site were closed in a Y pattern (Fig. 3 ) . Simple interrupted and continuous patterns of 3-0 polydioxanone were used for subcutaneous closure, and 3-0 polybutesters in far-near-near-far and simple interrupted patterns was used on the skin. t Hemoclip, Edward Weck Incorporated. Princeton, New Jersey. $ Penrose tubing, Argyle, Division of Shenvood Medical, St. Louis, Missouri. 5 Novafil. Davis and Geck. Cyanamid Canada Incorporated, Montreal, Quebec.
Fig. 2. The cervical part of the trapezius musculocutaneousflap (T) is elevated, exposing the prescapular branch of the superficial cervical vascular pedicle (P). Branches of the prescapular branch of the superficial cervical vascular pedicle going to the cleidocervicalis and other muscles are ligated (X).
437
PHILIBERT, FOWLER, AND CLAPSON
Fig. 3. The cervical part of the trapezius musculocutaneous flap has been harvested and the defect closed in a Y pattern. The latex drain exits at the level of the greater tubercule of the humerus.
The recipient site was prepared simultaneously by a second surgical team. A skin defect corresponding to the size of the flap was created on the medial side of the contralateral tibia. An incision was extended proximally, and a skin flap was elevated to expose the saphenous artery and medial saphenous vein up to their emerging point between the gracilis and caudal sartorius muscles. The musculocutaneous flap was secured to the recipient site with a few simple interrupted 3-0 polybutester sutures. The saphenous pedicle was transected at a level where anastomosis with the prescapular branch of the superficial cervical vascular pedicle was possible without tension. End-to-end microvascular anastomoses were performed with 9-0 or 10-0 nylon[(on a 100 pm needle with a simple interrupted pattern. Patency of the anastomoses was determined immediately and 30 minutes after removal of the vascular clamps by application of two jeweler's forceps to empty a small segment of the medial saphenous vein. The forceps nearest to the anastomosis were released first, and the segment was observed for rapid refill. The external diameters of the prescapular branch of the superficial cervical artery and vein were measured and compared with the saphenous pedicle. A %inch latex drain exiting at the distal tip of the recipient site was placed under the flap before cuticular closure with 3-0 polybutester in simple interrupted and cruciate patterns (Fig. 4). A light, soft, padded bandage was applied on the distal tip of the flap to cover the latex drain. Cephazolin sodium7 (30 mg/kg 1V) was administered every 2 hours during surgery. The dogs were kept separately in cages and walked three times daily for 21 days. An Elizabethan collar was put on each dog to prevent
11 Dermalon, Davis and Geck, American Cyanamid Company, Danbury, Connecticut. ll Kefzol, Eli Lilly, Toronto, Ontario.
self-mutilation. Necrosis, bleeding, discharge, dehiscence, edema, general appearance of the flap, body temperature, and lameness were evaluated daily. If signs of infection (fever, pain, purulent discharge) were present, cephalexin# (30 mg/kg orally BID for 3 to 4 days) was administered. Twenty-one days after surgery, dogs 3 and 4 were euthanatized with an overdose of barbiturate IV. Dog 2 was anesthetized for flap biopsies and retained to evaluate long-term function and cosmetic appearance of the flap. Nonselective and selective angiogaphy with a barium solution** were performed in dogs 3 and 4, respectively. The flaps were examined macroscopically, and a representative sample of slun, subcutaneous tissue, and cervical part of the trapezius muscle was secured to a wood tongue depressor and fixed in 10% formalin for histologic examination. The contralateral nondissected flap was used as a control. The biopsy specimens were sectioned and stained with hematoxylin-eosin. The flap in dog 1 was not available for histologic evaluation because of severe self-mutilation.
Results Two musculocutaneous flaps from the right side and two from the left side were transplanted in four dogs. Moderate tension was present on closure of donor sites, but closure was achieved in all dogs. Flap ischemia time was 75 to 130 minutes. Pedicle length was consistently more than 4 cm. The external diameter of the pedicles was 1.0 to 1.75 mm for the arteries and 2.0 to 3.0 mm for the veins. The dononecipient external vascular diameter ratios were 1:1 for arteries and 1:1 to 2: 1 for veins. The walls of the medial saphenous vein were consistently thicker than the prescapular branch of the superficial cervical vein. All vascular anastomoses were patent immediately and 30 minutes after completion (Table 1). Dehiscence at the donor site was not seen. Penrose drains were removed on days 2 or 3 and the cuticular sutures on day 14. All dogs were free of forelimb lameness on day 2. Seroma formation occurred to varying degrees in all dogs between days 7 and 15. Seromas were resorbed within 1 week without specific treatment. Forty hours after surgery, dog 1 mutilated the flap by opening the incision line over the anastomosis, resulting in severe subcutaneous hemorrhage secondary to damages of the anastomosis. The dog was subsequently euthanatized with an overdose of barbiturate IV. The other flaps became edematous within the first 3 days. The edema was most severe at day 5 and began to subside at day 11. Edema was minimal after day 14. ~~
# Novo-Lexin, Novopharm Limited, Toronto, Ontario.
**
Polybar, E-Z-EM, Montreal, Quebec.
438
TRANSPLANTATION OF TRAPEZIUS FLAP
Fig. 4. The cervical part of the trapezius musculocutaneous flap has been transferred and sutured to the recipient site. The prescapular branch of the superficialcervical vascular pedicle is anastomosed to the saphenous pedicle (arrow).
Infection was suspected when pain in dog 2 developed at the recipient site on day 3. The distal suture line was released for 5 cm to establish drainage. Dog 4 was febrile on day 4. Cephalexin was administered to both dogs for 4 days, with subsequent resolution of the clinical signs. The skin at the distal 25% and along the caudal suture line of the flap in dog 4 became necrotic between days 8 and 9. These areas corresponded to the craniodorsal and ventral skin areas on the donor site. They were debrided and treated as open wounds. Dehiscence occurred in dog 3 for 2 cm at the proximal part of the flap on day 5.
On day 21, the three surviving flaps were adhered to the recipient bed and healed to the surrounding skin. Hair growth was longer than on the rest of the limb. Subcutaneous fat made the flaps appear bulky. Complete perfusion of the vascular system of the flaps was visible in angiograms of dogs 3 and 4 (Fig. 5). On macroscopic postmortem examination, no edema or necrosis was visible, but small areas of hemorrhage were occasionally seen in the subcutaneous tissue and under the cervical part of the trapezius muscle. Dog 2 was examined at month 7. The flap was no longer bulky and, despite the fact that the hair was longer than in the surrounding area, the cosmetic appearance was acceptable. The donor site appeared normal. Histologically, the skin and muscle survived with minimal degeneration and at least moderate regeneration of damaged muscle fibers. Small collections of adipocytes in some areas were thought to be the result of fat replacement of lost muscle fibers (Fig. 6). The region below the muscle had abundant fibrous tissue.
Discussion Morbidity at the donor site was minimal. Closure of the defect was relatively easy, tension was not severe enough to cause dehiscence, and the appearance after closure was acceptable. The cervical part of the trapezius muscle had a dispensable function as indicated by the absence of lameness 2 days after its removal. Seroma formation was expected because of extensive dead space after closure of the defect. The Penrose drain could have been left for a longer period, but chances of ascending infection
TABLE 1. Surgical Data and Clinical Assessment Dog 2
Dog 1 Donor side Pedicle diameter Artery (mm) Vein (mm) Pedicle length (cm) Prescapular branch of the superficial cervica1:saphenous diameter ratios Arteries Veins Ischemic time (minutes) Clinical outcome Donor site
Recipient site
Left
Right 1.75
3.0
Dog 3 Right
1.5 3.0
Left 1.75
3.0
>4.0
>4.0
>4.0
1:l 1.5:l 130
1:l 2: 1 100
1:l 1:l
No lameness on day 2
No lameness on day 2
-
Self mutilation after 40 hours
Dog 4
75
Serorna days 15 to 21
No lameness on day 2 Seroma days 7 to 10 and 19 to 21
Pain on day 3 Healed at day 21
2 cm dehiscence Healed at day 21
1 .o
2.0 >4.0
1:l 151 100 No lameness on day 1 Seroma days 7 to 8 Fever on day 4 Necrosis distal 25% and caudal suture line on day 8 and 9 Healed at day 21
PHILIBERT,
439
FOWLER,AND CLAPSON
would have increased.24A compressivebandage could also have helped to prevent seroma formation, but such a bandage was difficult to maintain on the neck." A suction drain might have reduced the incidence of seroma, but it should be retained longer to allow formation of adherence between the subcutaneous tissue and the deep muscle layer.2." Penrose drains were chosen because they are easier to manage than suction drains. Edema of the musculocutaneous flap was the major problem at the recipient site. Tension resulting from edema may have caused the discomfort in dogs 1 and 2 and the limited skin dehiscence in dog 3. Partial flap necrosis in dog 4 may have been from inconsistent cutaneous vascular anatomy, but this is unlikely because the necrotic area corresponded to an area of well-perfused skin in the anatomic In this dog, no dehiscence was encountered before necrosis. The flap was under considerable tension because ofthe edema from days 4 to 8. The tension could have compromised the vascular supply to the skin at the periphery of the flap, causing ischemia and necrosis. The dependent position of the flap may have accounted for some degree of edema.* The external diameter of the saphenous vein was smaller than the prescapular branch of the-superficial cervical vein in three flaps, and it had a thicker wall in all flaps. The resistence to venous outflow may have been increased because of the decrease in the internal vascular diameter as blood entered the saphenous vein.25 The ischemic time was too short (130 minutes
Fig. 6 . Histologic section of a cervical part of the trapezius muscle 21 days after transplantation. There is a small collection of adipocytes (arrow) and a regenerating muscle fiber (arrowhead). (Hematoxylin eosin, 125x)
maximum) to incriminate reperfusion injury as a cause of edema. Four to 6 hours of normothermic ischemic time are required before reperfusion injury occurs in skeletal muscle.26A pressure bandage applied over the flap might have reduced edema formation and its associated complications.2*1 ' The longer hair and bulky subcutaneous tissue of the flaps were noticeable at day 2 1. The cervical part of the trapezius muscle transplantation without its overlying skin but covered instead with a free full- or split-thickness skin graft could improve the cosmetic result." The bulky appearance, however, disappeared after 7 months in one dog. Suturing the muscle in the subcutaneous tissue of the recipient site, in addition to cutaneous suturing, could also have helped to orient the healing tissue and the cosmetic end result.'' The cervical part of the trapezius muscle meets the criterion of a suitable muscle for reconstruction of severe soft tissue defect^.^,^ Minimal donor site morbidity, accessibility, dominant vascular supply, and large size are primary advantages. The final outcome may be improved with the use of compressive bandages and suture of the muscle under tension to the recipient subcutaneous tissue. References
Fig. 5. Lateralview of a selective angiogram performed by catheterizationof the saphenous artery (arrow). Perfusion of the entire flap is visible.
I . Gregory CR, Gourley IM, Koblik PD, Patz JD. Experimental definition of latissimus dorsi, gracilis, and rectus abdominus musculocutaneous flaps in the dog. Am J Vet Res 1988;49:878-884. 2. Mathes SJ, Eshima I. The principles of muscle and musculocutaneous flaps. In: McCarthy JG, ed. Plastic Surgery. Philadelphia: WB Saunders, 1990:379-4 I I . 3. Mathes SJ, Nahai F. Clinical Applications.fi?r Muscle und Musczr/ocutaneous/7aps. St. Louis: CV Mosby, 1982: 1-36, 638-640. 4. Asaadi M, Murray KA, Russell RC, Zook EG. Experimental evaluation of free-tissue transfer to promote healing of infected wounds in dogs. Ann Plast Surg 1986: 17:6-12. 5 . Khouri RK, Shaw WW. Reconstruction of the lower extremity with microvascular free flaps: A 10-year experience with 304 consecutive cases. J Trauma 1989:29:1086-1094. 6 . Basher AWP, Presnell KR. Muscle transposition as an aid in covering traumatic tissue defects over the canine tibia. J Am Anim Hosp Assoc 1987;23:617-628. 7. Amold PG, Pairolero PC. Intrathoracic muscle flaps: A 10-year experience in the management of life-threatening infections. Plast Reconstr Surg 1989;84:92-98.
TRANSPLANTATION OF TRAPEZIUS FLAP 8. Mathes SJ. Alpert BS, Chang N. Use of the muscle flap in chronic osteomyelitis: Experimental and clinical correlation. Plast Reconstr Surg 1982;69:8 15-829. 9. Melissinos EG, Parks DH. Post-trauma reconstruction with free tissue transfer: Analysis of 442 consecutive cases. J Trauma 1989;29: 1095-1 103. 10. Byrd HS, Cierny G, Tebbetts JB. The management of open tibia1 fractures with associated soft-tissue loss: External pin fixation with early flap coverage. Plast Reconstr Surg 198 I ; 68:73-79. 1 1 . May JW, Gallico GG, Jupiter J, Savage RC. Free latissimus dorsi muscle flap with skin graft for treatment of traumatic chronic bony wounds. Plast Reconstr Surg 1984;73:641-648. 12. Rhinelander FW. Baragry RA. Microangiography in bone healing 1. Undisplaced closed fractures. J Bone Joint Surg Am 1962;44: 1273-1289. 13. Rhinelander F W ,Phillips RS, Steel WM, Beer JC. Microangiography in bone healing: 11: Displaced closed fractures. J Bone Joint Surg Am 1968;50:643-662. 14. Harii K, Ohmori K, Sekiguchi J. The free rnusculocutaneous flap. Plast Reconstr Surg 1976;57:294-303. 15. Mathes SJ. McCraw JB, Vasconez LO. Muscle transposition flaps for coverage of lower extremity defects, anatomic considerations. Surg Clin North Am 1974;54:1337-1354. 16. Mathes SJ, Nahai F, Vasconez LO. Myocutaneous free-flap transfer: Anatomical and experimental considerations. Plat Reconstr Surg l978:62: 162-166.
17. Pavletic MM. Vascular supply to the skin of the dog: A review. Vet Surg 1980;9:77-80. 18. Pavletic MM. Anatomy and circulation of the canine skin. Microsurgery 1991;12:103-112. 19. Chambers JN, Purinton PT. Allen SW, Moore JL. Identification and anatomic categorization of the vascular patterns to the pelvic limb muscles of dogs. Am J Vet Res 1990;5 1:305-3 13. 20. Taylor GI, Palmer JH. McManamny D. The vascular temtories of the body (angiosomes) and their clinical applications. In: McCarthy JG, ed. Plustic Surgery Philadelphia: WB Saunders, I990 329-378. 2 1. Mathes SJ, Nahai F. Clinicul Allus ufMiiscle and Musczclocutaneous Jups. St. Louis: CV Mosby, 1979:l-7. 22. Mathes SJ, Nahai F. Classification of the vascular anatomy of muscles: Experimental and clinical correlation. Plast Reconstr Surg I98 1 ;67: 177-187. 23. Philibert D, Fowler JD, Clapson JB. The anatomic basis for a trapezius muscle flap in dogs. Vet Surg 1992;21:429-434. 24. Hampel NL, Johnson RG. Principles of surgical drains and drainage. J Am Anirn Hosp Assoc 1985;21:21-28. 25. OBrien BM, Momson WA. Gumley GJ. Principles and techniques of microvascular surgery. In: McCarthy JG. ed. Plastic Szirgery. Philadelphia: WB Saunders, 1990:412-474. 26. Pang CY. Ischemia-induced reperfusion injury in muscle flaps: Pathogenesis and major source of free radicals. J Reconstr Microsurg 1990;6:77-83.
Free Microvascular Transplantation of the Trapezius Musculocutaneous Flap in Dogs DENIS PHILIBERT, DVM, MVetSc, J. DAVID FOWLER,DVM, MVetSc, Diplomate ACVS, and J. BRIAN CLAPSON, NM, FRCS(C)
A musculocutaneousflap based on the prescapular branch of the superficial cervical artery and including the cervical part of the trapezius muscle and overlying skin was transplanted over a defect created on the medial side of the contralateral tibia in four dogs by using microvasculartechnique. The donor and recipient sites in three dogs were examined clinically for 21 days, after which they were examined angiographically and histologically. All dogs were free of lameness by hour 48. Seromas formed at the donor site between days 7 and 15. One vascular pedicle was traumatized at hour 40, and the dog was euthanatized. Three flaps survived with minimal necrosis. Edema of the flaps was severe from days 5 to 11. Angiograms showed complete perfusion of the flaps, and survival was confirmed histologically. Esthetic appearance and function were good in one dog at month 7.
thetic appearance of donor and recipient sites, such as excessive bulk or eventual atr~phy.'.'~ A muscular or musculocutaneous flap should have size and bulk to allow coverage of the defect and should have an expendable f ~ n c t i o n . ~ . It ~ .should " be easily accessible and have a constant dominant vascular upp ply.^.^,'^ If a musculocutaneous flap is used, a sufficient overlying area of skin supplied by a direct cutaneous artery should be a ~ a i l a b l e . * ~The ~ ~ ' ~donor , ' ~ site should be easily closed with minimal m ~ r b i d i t y .Knowledge ~?~ of the location of the motor and sensory nerve entrance and the presence of an osseous temtory are also a d v a n t a g e ~ u s . ~ . ~ Anatomic studies of the vascular supply of the tissue to be transferred provide essential information for the design of simple or composite flaps for clinical use.3,15,19-22 A composite flap based on its dominant vascular pedicle can be raised and transplanted ~ a f e l y . ~ , ' The ~ . ~ vascular ~,~' temtory of the prescapular branch of the superficial cervical artery, which includes the cervical part of the trapezius muscle, has been de~cribed.'~ The purpose of this study is to test the viability of a musculocutaneous flap consisting of the cervical part of the trapezius muscle and overlying skin transplanted to a defect created on the me-
after trzuma, F surgical procedures, radiation therapy, or congenital defects can be difficult. When simpler methods are not UNCTIONALTISSUERECONSTRUCTION
appropriate, free microvascular transplantation of tissue should be considered because it provides soft-tissue coverage in a one-stage procedure.'-5 Muscle or compound muscle flaps provide bulk and protection for deep defects and are malleable, reliable, and easily available.2 Because of their rich blood supply, muscle and compound muscle flaps are an ideal bed for skin grafts and are resistant to infecti~n.~?' Muscle flaps increase oxygen tension in a wound and are believed to carry body defense mechanisms via their rich perfusion.8 When combined with aggessive debridement and tissue stabilization, their efficacy in prevention or treatment of osteomyelitis is well documented experimentally and c l i n i ~ a l l y . ~ ~The ~ ~ ~superiority -' of muscle flaps over skin alone is well documented."g8 Coverage of bone with muscle helps establish a periosteal blood supply in the early phase of bone It increases periosteal new bone formation, decreases the risk of wound sepsis,6 and provides a source for revascularization of devascularized bone fragment^.^ The major disadvantages of muscle flaps are associated with the es-
'
~
~
~~
From the Departmentof Vetennary Anesthesiology, Radiologyand Surgery, Western College of Veterinary Medicine, Universityof Saskatchewan, Saskatoon, Saskatchewan, Canada Supported by the Companion Animal Health Fund, Western College of Veterinary Medicine Reprint requests Denis Philibert, DVM, MVetSc, Western College of Vetennary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N-OW0
435
TRANSPLANTATION OF TRAPEZIUS FLAP
Fig. 1. Trapezius musculocutaneous flap. The broken line indicates the skin incision in relation to the direct cutaneous artery (D), the scapula, and the wing of the atlas (A).
dial side of the tibia with microvascular technique, and to evaluate donor site morbidity. Materials and Methods Distant transfer of the cervical part of the trapezius musculocutaneous flap by microvascular anastomosis was performed in four healthy adult male mongrel dogs weighing 17 to 22.5 kg. All procedures were approved by the Animal Care Committee of the University of Saskatchewan and conformed to the Guide to the Care and Use of Experimental Animals by the Canadian Council on Animal Care. All dogs were premedicated with acepromazine (0.05 mg/kg intramuscularly [IM]), and anesthesia was induced with sodium thiamylal (10 to 15 mg/ kg intravenously [IV]) and maintained with halothane and oxygen. Oxymorphone (0. 1 mg/kg IM) was administered as required for analgesia after the surgery. The side of flap elevation was assigned randomly. A curved skin incision was directed dorsally and cranially from the distal third of the spine of the scapula to approximately 5 cm caudal to the wing of the atlas. The arc extended as far dorsally as 2 cm from the dorsal midline. A ventrally curved incision was made between the same two points, taking care to preserve the region where the direct cutaneous artery supplying the skin emerged (Fig. 1). The dorsal part of the cervical part of the trapezius muscle was elevated and sutured to the overlying skin with a few simple interrupted sutures of 3-0 polydioxanone.* The caudodorsal tip of the cervical part of the trapezius muscle was left in situ. The accessory nerve was severed at the caudodorsal border of the cervical part of the trapezius muscle, as it exited the muscle. The muscle
* PDS 11. Ethicon, Somerville. New Jersey.
was transected about 5 mm from its insertion on the scapular spine. Branches of the prescapular branch of the superficial cervical vascular pedicle penetrating the deep musculature were ligated. Dissection was continued between the cervical part of the trapezius and the cleidocervicalis and omotransversarius muscles, keeping the dissection close to the omotransversarius and cleidocervicalis muscles to avoid damaging vascular branches to the cervical part of the trapezius muscle and to preserve the vascular pedicle at the junction of those three muscles. The accessory nerve was severed at its entrance to the cervical part of the trapezius muscle. The cervical part of the trapezius muscle was sutured to the skin flap ventrally. Branches of the prescapular branch of the superficial cervical vascular pedicle, proximal to the branches going to the skin and cervical part of the trapezius muscle, were ligated and divided up to the level of the acromial branch ofthe superficial cervical artery (Fig. 2). The pedicle length was measured between the first branches to the cervical part of the trapezius muscle and the acromial branch of the superficial cervical artery. The pedicle was ligated and transected just distal to the acromial branch. Electrocautery and vascular clipst were used for hemostasis. A %inch latex drain$ exiting at the level of the greater tubercule of the humerus was inserted. Subcutaneous and cutaneous tissues at the donor site were closed in a Y pattern (Fig. 3 ) . Simple interrupted and continuous patterns of 3-0 polydioxanone were used for subcutaneous closure, and 3-0 polybutesters in far-near-near-far and simple interrupted patterns was used on the skin. t Hemoclip, Edward Weck Incorporated. Princeton, New Jersey. $ Penrose tubing, Argyle, Division of Shenvood Medical, St. Louis, Missouri. 5 Novafil. Davis and Geck. Cyanamid Canada Incorporated, Montreal, Quebec.
Fig. 2. The cervical part of the trapezius musculocutaneousflap (T) is elevated, exposing the prescapular branch of the superficial cervical vascular pedicle (P). Branches of the prescapular branch of the superficial cervical vascular pedicle going to the cleidocervicalis and other muscles are ligated (X).
437
PHILIBERT, FOWLER, AND CLAPSON
Fig. 3. The cervical part of the trapezius musculocutaneous flap has been harvested and the defect closed in a Y pattern. The latex drain exits at the level of the greater tubercule of the humerus.
The recipient site was prepared simultaneously by a second surgical team. A skin defect corresponding to the size of the flap was created on the medial side of the contralateral tibia. An incision was extended proximally, and a skin flap was elevated to expose the saphenous artery and medial saphenous vein up to their emerging point between the gracilis and caudal sartorius muscles. The musculocutaneous flap was secured to the recipient site with a few simple interrupted 3-0 polybutester sutures. The saphenous pedicle was transected at a level where anastomosis with the prescapular branch of the superficial cervical vascular pedicle was possible without tension. End-to-end microvascular anastomoses were performed with 9-0 or 10-0 nylon[(on a 100 pm needle with a simple interrupted pattern. Patency of the anastomoses was determined immediately and 30 minutes after removal of the vascular clamps by application of two jeweler's forceps to empty a small segment of the medial saphenous vein. The forceps nearest to the anastomosis were released first, and the segment was observed for rapid refill. The external diameters of the prescapular branch of the superficial cervical artery and vein were measured and compared with the saphenous pedicle. A %inch latex drain exiting at the distal tip of the recipient site was placed under the flap before cuticular closure with 3-0 polybutester in simple interrupted and cruciate patterns (Fig. 4). A light, soft, padded bandage was applied on the distal tip of the flap to cover the latex drain. Cephazolin sodium7 (30 mg/kg 1V) was administered every 2 hours during surgery. The dogs were kept separately in cages and walked three times daily for 21 days. An Elizabethan collar was put on each dog to prevent
11 Dermalon, Davis and Geck, American Cyanamid Company, Danbury, Connecticut. ll Kefzol, Eli Lilly, Toronto, Ontario.
self-mutilation. Necrosis, bleeding, discharge, dehiscence, edema, general appearance of the flap, body temperature, and lameness were evaluated daily. If signs of infection (fever, pain, purulent discharge) were present, cephalexin# (30 mg/kg orally BID for 3 to 4 days) was administered. Twenty-one days after surgery, dogs 3 and 4 were euthanatized with an overdose of barbiturate IV. Dog 2 was anesthetized for flap biopsies and retained to evaluate long-term function and cosmetic appearance of the flap. Nonselective and selective angiogaphy with a barium solution** were performed in dogs 3 and 4, respectively. The flaps were examined macroscopically, and a representative sample of slun, subcutaneous tissue, and cervical part of the trapezius muscle was secured to a wood tongue depressor and fixed in 10% formalin for histologic examination. The contralateral nondissected flap was used as a control. The biopsy specimens were sectioned and stained with hematoxylin-eosin. The flap in dog 1 was not available for histologic evaluation because of severe self-mutilation.
Results Two musculocutaneous flaps from the right side and two from the left side were transplanted in four dogs. Moderate tension was present on closure of donor sites, but closure was achieved in all dogs. Flap ischemia time was 75 to 130 minutes. Pedicle length was consistently more than 4 cm. The external diameter of the pedicles was 1.0 to 1.75 mm for the arteries and 2.0 to 3.0 mm for the veins. The dononecipient external vascular diameter ratios were 1:1 for arteries and 1:1 to 2: 1 for veins. The walls of the medial saphenous vein were consistently thicker than the prescapular branch of the superficial cervical vein. All vascular anastomoses were patent immediately and 30 minutes after completion (Table 1). Dehiscence at the donor site was not seen. Penrose drains were removed on days 2 or 3 and the cuticular sutures on day 14. All dogs were free of forelimb lameness on day 2. Seroma formation occurred to varying degrees in all dogs between days 7 and 15. Seromas were resorbed within 1 week without specific treatment. Forty hours after surgery, dog 1 mutilated the flap by opening the incision line over the anastomosis, resulting in severe subcutaneous hemorrhage secondary to damages of the anastomosis. The dog was subsequently euthanatized with an overdose of barbiturate IV. The other flaps became edematous within the first 3 days. The edema was most severe at day 5 and began to subside at day 11. Edema was minimal after day 14. ~~
# Novo-Lexin, Novopharm Limited, Toronto, Ontario.
**
Polybar, E-Z-EM, Montreal, Quebec.
438
TRANSPLANTATION OF TRAPEZIUS FLAP
Fig. 4. The cervical part of the trapezius musculocutaneous flap has been transferred and sutured to the recipient site. The prescapular branch of the superficialcervical vascular pedicle is anastomosed to the saphenous pedicle (arrow).
Infection was suspected when pain in dog 2 developed at the recipient site on day 3. The distal suture line was released for 5 cm to establish drainage. Dog 4 was febrile on day 4. Cephalexin was administered to both dogs for 4 days, with subsequent resolution of the clinical signs. The skin at the distal 25% and along the caudal suture line of the flap in dog 4 became necrotic between days 8 and 9. These areas corresponded to the craniodorsal and ventral skin areas on the donor site. They were debrided and treated as open wounds. Dehiscence occurred in dog 3 for 2 cm at the proximal part of the flap on day 5.
On day 21, the three surviving flaps were adhered to the recipient bed and healed to the surrounding skin. Hair growth was longer than on the rest of the limb. Subcutaneous fat made the flaps appear bulky. Complete perfusion of the vascular system of the flaps was visible in angiograms of dogs 3 and 4 (Fig. 5). On macroscopic postmortem examination, no edema or necrosis was visible, but small areas of hemorrhage were occasionally seen in the subcutaneous tissue and under the cervical part of the trapezius muscle. Dog 2 was examined at month 7. The flap was no longer bulky and, despite the fact that the hair was longer than in the surrounding area, the cosmetic appearance was acceptable. The donor site appeared normal. Histologically, the skin and muscle survived with minimal degeneration and at least moderate regeneration of damaged muscle fibers. Small collections of adipocytes in some areas were thought to be the result of fat replacement of lost muscle fibers (Fig. 6). The region below the muscle had abundant fibrous tissue.
Discussion Morbidity at the donor site was minimal. Closure of the defect was relatively easy, tension was not severe enough to cause dehiscence, and the appearance after closure was acceptable. The cervical part of the trapezius muscle had a dispensable function as indicated by the absence of lameness 2 days after its removal. Seroma formation was expected because of extensive dead space after closure of the defect. The Penrose drain could have been left for a longer period, but chances of ascending infection
TABLE 1. Surgical Data and Clinical Assessment Dog 2
Dog 1 Donor side Pedicle diameter Artery (mm) Vein (mm) Pedicle length (cm) Prescapular branch of the superficial cervica1:saphenous diameter ratios Arteries Veins Ischemic time (minutes) Clinical outcome Donor site
Recipient site
Left
Right 1.75
3.0
Dog 3 Right
1.5 3.0
Left 1.75
3.0
>4.0
>4.0
>4.0
1:l 1.5:l 130
1:l 2: 1 100
1:l 1:l
No lameness on day 2
No lameness on day 2
-
Self mutilation after 40 hours
Dog 4
75
Serorna days 15 to 21
No lameness on day 2 Seroma days 7 to 10 and 19 to 21
Pain on day 3 Healed at day 21
2 cm dehiscence Healed at day 21
1 .o
2.0 >4.0
1:l 151 100 No lameness on day 1 Seroma days 7 to 8 Fever on day 4 Necrosis distal 25% and caudal suture line on day 8 and 9 Healed at day 21
PHILIBERT,
439
FOWLER,AND CLAPSON
would have increased.24A compressivebandage could also have helped to prevent seroma formation, but such a bandage was difficult to maintain on the neck." A suction drain might have reduced the incidence of seroma, but it should be retained longer to allow formation of adherence between the subcutaneous tissue and the deep muscle layer.2." Penrose drains were chosen because they are easier to manage than suction drains. Edema of the musculocutaneous flap was the major problem at the recipient site. Tension resulting from edema may have caused the discomfort in dogs 1 and 2 and the limited skin dehiscence in dog 3. Partial flap necrosis in dog 4 may have been from inconsistent cutaneous vascular anatomy, but this is unlikely because the necrotic area corresponded to an area of well-perfused skin in the anatomic In this dog, no dehiscence was encountered before necrosis. The flap was under considerable tension because ofthe edema from days 4 to 8. The tension could have compromised the vascular supply to the skin at the periphery of the flap, causing ischemia and necrosis. The dependent position of the flap may have accounted for some degree of edema.* The external diameter of the saphenous vein was smaller than the prescapular branch of the-superficial cervical vein in three flaps, and it had a thicker wall in all flaps. The resistence to venous outflow may have been increased because of the decrease in the internal vascular diameter as blood entered the saphenous vein.25 The ischemic time was too short (130 minutes
Fig. 6 . Histologic section of a cervical part of the trapezius muscle 21 days after transplantation. There is a small collection of adipocytes (arrow) and a regenerating muscle fiber (arrowhead). (Hematoxylin eosin, 125x)
maximum) to incriminate reperfusion injury as a cause of edema. Four to 6 hours of normothermic ischemic time are required before reperfusion injury occurs in skeletal muscle.26A pressure bandage applied over the flap might have reduced edema formation and its associated complications.2*1 ' The longer hair and bulky subcutaneous tissue of the flaps were noticeable at day 2 1. The cervical part of the trapezius muscle transplantation without its overlying skin but covered instead with a free full- or split-thickness skin graft could improve the cosmetic result." The bulky appearance, however, disappeared after 7 months in one dog. Suturing the muscle in the subcutaneous tissue of the recipient site, in addition to cutaneous suturing, could also have helped to orient the healing tissue and the cosmetic end result.'' The cervical part of the trapezius muscle meets the criterion of a suitable muscle for reconstruction of severe soft tissue defect^.^,^ Minimal donor site morbidity, accessibility, dominant vascular supply, and large size are primary advantages. The final outcome may be improved with the use of compressive bandages and suture of the muscle under tension to the recipient subcutaneous tissue. References
Fig. 5. Lateralview of a selective angiogram performed by catheterizationof the saphenous artery (arrow). Perfusion of the entire flap is visible.
I . Gregory CR, Gourley IM, Koblik PD, Patz JD. Experimental definition of latissimus dorsi, gracilis, and rectus abdominus musculocutaneous flaps in the dog. Am J Vet Res 1988;49:878-884. 2. Mathes SJ, Eshima I. The principles of muscle and musculocutaneous flaps. In: McCarthy JG, ed. Plastic Surgery. Philadelphia: WB Saunders, 1990:379-4 I I . 3. Mathes SJ, Nahai F. Clinical Applications.fi?r Muscle und Musczr/ocutaneous/7aps. St. Louis: CV Mosby, 1982: 1-36, 638-640. 4. Asaadi M, Murray KA, Russell RC, Zook EG. Experimental evaluation of free-tissue transfer to promote healing of infected wounds in dogs. Ann Plast Surg 1986: 17:6-12. 5 . Khouri RK, Shaw WW. Reconstruction of the lower extremity with microvascular free flaps: A 10-year experience with 304 consecutive cases. J Trauma 1989:29:1086-1094. 6 . Basher AWP, Presnell KR. Muscle transposition as an aid in covering traumatic tissue defects over the canine tibia. J Am Anim Hosp Assoc 1987;23:617-628. 7. Amold PG, Pairolero PC. Intrathoracic muscle flaps: A 10-year experience in the management of life-threatening infections. Plast Reconstr Surg 1989;84:92-98.
TRANSPLANTATION OF TRAPEZIUS FLAP 8. Mathes SJ. Alpert BS, Chang N. Use of the muscle flap in chronic osteomyelitis: Experimental and clinical correlation. Plast Reconstr Surg 1982;69:8 15-829. 9. Melissinos EG, Parks DH. Post-trauma reconstruction with free tissue transfer: Analysis of 442 consecutive cases. J Trauma 1989;29: 1095-1 103. 10. Byrd HS, Cierny G, Tebbetts JB. The management of open tibia1 fractures with associated soft-tissue loss: External pin fixation with early flap coverage. Plast Reconstr Surg 198 I ; 68:73-79. 1 1 . May JW, Gallico GG, Jupiter J, Savage RC. Free latissimus dorsi muscle flap with skin graft for treatment of traumatic chronic bony wounds. Plast Reconstr Surg 1984;73:641-648. 12. Rhinelander FW. Baragry RA. Microangiography in bone healing 1. Undisplaced closed fractures. J Bone Joint Surg Am 1962;44: 1273-1289. 13. Rhinelander F W ,Phillips RS, Steel WM, Beer JC. Microangiography in bone healing: 11: Displaced closed fractures. J Bone Joint Surg Am 1968;50:643-662. 14. Harii K, Ohmori K, Sekiguchi J. The free rnusculocutaneous flap. Plast Reconstr Surg 1976;57:294-303. 15. Mathes SJ. McCraw JB, Vasconez LO. Muscle transposition flaps for coverage of lower extremity defects, anatomic considerations. Surg Clin North Am 1974;54:1337-1354. 16. Mathes SJ, Nahai F, Vasconez LO. Myocutaneous free-flap transfer: Anatomical and experimental considerations. Plat Reconstr Surg l978:62: 162-166.
17. Pavletic MM. Vascular supply to the skin of the dog: A review. Vet Surg 1980;9:77-80. 18. Pavletic MM. Anatomy and circulation of the canine skin. Microsurgery 1991;12:103-112. 19. Chambers JN, Purinton PT. Allen SW, Moore JL. Identification and anatomic categorization of the vascular patterns to the pelvic limb muscles of dogs. Am J Vet Res 1990;5 1:305-3 13. 20. Taylor GI, Palmer JH. McManamny D. The vascular temtories of the body (angiosomes) and their clinical applications. In: McCarthy JG, ed. Plustic Surgery Philadelphia: WB Saunders, I990 329-378. 2 1. Mathes SJ, Nahai F. Clinicul Allus ufMiiscle and Musczclocutaneous Jups. St. Louis: CV Mosby, 1979:l-7. 22. Mathes SJ, Nahai F. Classification of the vascular anatomy of muscles: Experimental and clinical correlation. Plast Reconstr Surg I98 1 ;67: 177-187. 23. Philibert D, Fowler JD, Clapson JB. The anatomic basis for a trapezius muscle flap in dogs. Vet Surg 1992;21:429-434. 24. Hampel NL, Johnson RG. Principles of surgical drains and drainage. J Am Anirn Hosp Assoc 1985;21:21-28. 25. OBrien BM, Momson WA. Gumley GJ. Principles and techniques of microvascular surgery. In: McCarthy JG. ed. Plastic Szirgery. Philadelphia: WB Saunders, 1990:412-474. 26. Pang CY. Ischemia-induced reperfusion injury in muscle flaps: Pathogenesis and major source of free radicals. J Reconstr Microsurg 1990;6:77-83.
