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Successful, Full-Thickness Skin Graft in a Bald Eagle (Haliaeetus leucocephalus).

Abstract: A subadult, male bald eagle (Haliaeetus leucocephalus) was evaluated after being found unable to fly, with large eschars on the dorsal head and right stifle. Because of the appearance and location, the lesions were believed to be caused by an electrical injury. Treatment included oral antibiotics, nonsteroidal anti-inflammatory drugs, pain medication, surgical debridement of the eschars, and trephining of the affected inner table of the cranium. A full-thickness skin graft was performed to expedite wound healing and minimize holding time. After 6 weeks, the bird had new feather growth on its dorsal head and was released. This is the first report, to our knowledge, of a nonmesh, full-thickness skin graft in an avian species. Full-thickness skin grafts should be considered as a surgical option in juvenile or adult avian patients with large dorsal head wounds.

Key words: electrocution, trephining, skin graft, full-thickness, raptor, avian, bald eagle, Haliaeetus leucocephalus

CLINICAL REPORT

A free-ranging, subadult, male bald eagle (Haliaeetus leucocephalus) was found unable to fly. On initial examination, the bird was bright and alert, and all vital parameters were within reference intervals. A black, 7.0 x 8.0-cm eschar, consisting of the epidermis, dermis, periosteum, and compact cranial bone, was observed on the dorsal head and underlying tissue (Fig 1). A 1.0 x 0.5-cm, black, hemorrhagic eschar was also noted on the medial aspect of the right stifle. The eagle weighed 2.35 kg and was emaciated, with a body condition score of 1/5 based on general muscle mass. The appearance and location of the lesions were similar to those of other birds that have suffered electrical injuries.

The bird was administered enrofloxacin (15 mg/ kg PO ql2h), lactated Ringer's (50 mL/kg SC q24h), and a wound healing solution (Vetericyn Plus Innovacyn, Inc, Rialto, CA, USA), and 2% chlorhexidine ointment were applied to the dorsal head. A bandage was applied around the head, which consisted of a nonadhesive film dressing, an adhesive film dressing, and a cohesive bandage. Chlorhexidine ointment was applied to the eschar of the right stifle injury, but no bandage was placed because of the location of the injury. The eagle received slow-release meloxicam (0.5 mg/kg SC, Meloxicam SR, ZooPharm, Wildlife Pharmaceuticals, Windsor, CO, USA) and tramadol hydrochloride for analgesia (5 mg/kg PO q12h for 14 days). The bandage was changed every other day for 10 days with reapplication of the Vetericyn Plus as well as the addition of 1% silver sulfadiazine cream.

The wounds of the dorsal head and stifle were examined 2 weeks after initial treatment. Anesthesia was induced with sevoflurane in oxygen, delivered through a face mask (8% in 1 L/min), followed by intubation with an uncuffed Cole endotracheal tube (6.0 mm). The bird was maintained on 3%-6% sevoflurane in oxygen (1 L/min) and received lactated Ringer's (5 mL/kg IV). The right stifle wound was completely healed. The bird was placed in ventral recumbency, and feathers around the wound margins of the dorsal head were plucked. The dorsal head eschar was gently removed with tissue forceps, revealing healthy pink granulation tissue (Fig 2) and exposed cranium cancellous bone. The granulation tissue was gently flushed with sterile saline. Small burr holes were placed on the remaining, exposed cranium surface, revealing, but not breaching, the underlying endosteal layer of the dura mater. A sample of the granulation tissue was collected for aerobic bacterial culture. The wound and surrounding skin were flushed again with sterile saline, and a bandage was applied, as previously described. Before recovery, the eagle received slow-release buprenorphine (1.8 mg/kg SC; ZooPharm, Wildlife Pharmaceuticals) and another dose of slow-release meloxicam. After the procedure, the eagle was restarted on a 14-day treatment of tramadol hydrochloride at the previous dosage, and 3 days after the procedure, treatment with meloxicam (1.5 mg/kg PO q12h) for 7 days was initiated.

Daily bandage changes were performed under manual restraint for 1 week. After 7 days, skin epithelialization of the dorsal head wound was observed to extend 1 cm from the wound margin on the left and 0.5 cm on the right. Given the degree of improvement, bandage changes were extended to every other day for the next 2 weeks. At 3 weeks after initial debridement, the wound had contracted 1.5 cm circumferentially, with viable granulation tissue emanating from the burr holes. Healing was sufficient to support a full-thickness skin graft.

Before the skin graft procedure, blood samples were collected, for hematologic testing and plasma biochemical analysis, by venipuncture of the right jugular vein. Hematologic results were within reference intervals for the species; however, heterophils appeared slightly toxic, compatible with ongoing inflammation or stress.

The bird was anesthetized, as previously described, for a full-thickness skin graft from the medial aspect of the left leg to the dorsal head. Slow-release meloxicam and slow-release buprenorphine were administered at previous doses before the procedure. Feathers were plucked from the medial aspect of the left pelvic limb inguinal skin fold and the wound edges on the dorsal head. The surgical areas were aseptically prepped with iodine scrub and saline. To prepare the dorsal head for the skin graft, a dermabrader (MicroAire Surgical Instruments, Charlottesville, VA, USA) was used to remove devitalized tissue and abrade the granulation tissue until blood was observed. A square, 3 x 3-cm of skin at the donor site was delineated through placement of stay sutures using absorbable 3-0 polydioxanone suture (PDS II, Ethicon, Somerville, NJ, USA) to match the lesion on the dorsal head. Sterile saline (30 mL) was injected into the subcutaneous space to elevate the epidermis from the subcutaneous fat. A fullthickness graft was collected from the skin of the medial left leg. The leg-incision skin was closed with 3-0 absorbable, polydioxanone suture in a simple, continuous pattern. The collected skin from the leg was immediately immersed in saline to maintain moisture. The subdermal tissue was removed from the raw surface of the skin, leaving only the dermis with its elements of feathers and oil glands. An effort was made to preserve the direction of feather growth before placing the graft on the dorsal head. The skin graft was trimmed to match the head-lesion shape and sutured to the dorsal head with 3-0 polydioxanone, absorbable suture in a simple, continuous pattern. Every other bite of suture was tacked to the skull periosteum at the margins of the wound to decrease dead space. Staples were placed just beyond the wound edges as anchors for a tie-over bandage, and 10 gauze squares, moistened with sterile saline, were placed on the skin graft. A nonabsorbable, 2-0 nylon suture (Ethilon, Ethicon) was tied over the gauze as a tie-over bandage. A nonadherent, cationic biocide dressing (Bioguard, Derma Sciences Inc, Toronto, ON, Canada) was stapled to the skin over the tie-over bandage to prevent slippage and to decrease the likelihood of accidental removal.

Staphylococcus aureus was isolated from the granulation tissue aerobic culture, which was susceptible to all antimicrobials tested. The bird was treated with amoxicillin trihydrate/clavulanate potassium (100 mg/kg PO q 12h) and was continued on tramadol at the previous dosage for an additional 10 days.

Ten days after the skin graft procedure, the bird was immobilized for graft evaluation and removal of the tie-over bandage. The same immobilization protocol was used as previously described. The staples and sutures from around the wound were removed along with the bandage. Examination of the bird's head revealed near-complete vascularization and adherence of the graft with a 1.0 x 0.5cm area of green discoloration in the middle. This indicated an approximately 90% acceptance of the skin graft (Fig 3). The incision on the medial aspect of the leg healed without complication, and sutures were removed.

After 2 weeks, the eagle was visually rechecked, and the graft continued to retain good color, with new feathers beginning to grow (Fig 4). The discolored area of the graft, which had not completely inosculated, continued to heal by secondary intention.

The bald eagle was maintained in the wildlife rehabilitation facility for an additional 3 weeks to ensure continued growth of feathers. The bird was released to the location at which it had been originally found 6 weeks after the full thickness skin graft.

DISCUSSION

This clinical report describes the medical and surgical management of a dorsal head wound in a subadult bald eagle, suspected to be secondary to an electrical injury. A full-thickness skin graft, with the growth of new feathers on the dorsal head, was achieved. This is the first report, to our knowledge, of a successful, nonmesh, full-thickness skin graft in an avian species.

Large wounds in birds can be difficult to heal without complications. (1,2) Wounds in areas with minimal extra skin are difficult to close without tension, have increased risk of dehiscence, and can lead to contracture after healing by second intention. (1) Because of those limitations, skin flaps, extracellular matrices, and autografts have been used in avian species.

A skin flap is a segment of skin and subcutaneous tissue that remains attached to a blood supply as it is moved into a new, adjacent position, usually in the form of pedicle advancement. (1) A pedicle-advancement flap was successfully used to cover a large, open wound on the distal antebrachium of a great-horned owl (Bubo virginianus). (3) A pedicle-advancement flap was used to cover degloving head injuries in a northern goshawk (Accipiter gentilis). (4) A pedicle-advancement flap was also used to cover head wounds in a ring-necked pheasant (Phasianus colchicus), a rock dove (Columba livia), and a red-tailed hawk (Buteo jamaicensis). (5) Skin flaps were used on 3 eastern imperial eagles (Aquila heliaca) with skin damage on distal limbs. (6) Lastly, an advancement flap was used to treat chronic pododermatitis in a red-tailed hawk. (7) Extracellular matrices, such as swine small-intestinal submucosa in the form of a xenogeneic graft, can provide the framework for wound healing and reconstruction.' Swine small-intestinal submucosa xenogeneic grafting was successful in repairing severe skin defects in a red-railed hawk, 2 barn owls (Tyto alba), an umbrella cockatoo (Cacatua alba), and an American crow (Corvus brachyrhynchos). (1,8)

In the bald eagle we describe, a full-thickness skin graft was chosen because of the size of the lesion, the minimal available surrounding tissue, and the potential for tension dehiscence in the highly mobile neck area. Skin grafts are a portion of dermis and epidermis that are collected from 1 area and transferred to another site. (1,9) Their survival depends on the absorption of fluid and the development of a new blood supply at the recipient site. (1,9,10) Skin grafts are indicated when there are defects that cannot be closed by the surrounding skin. (9,10) Grafts are not successful in areas with poor blood supply, infection, excessive movement, or fat. (9,10) Creating a mesh in the graft allows for improved contact with the wound and drainage of exudate. (9,10) A fullthickness mesh graft was successful in treating large, open wounds on distal extremities in 2 great horned owls. (2) A full-thickness mesh graft was described in an adult female ostrich (Struthio camelus) with a wound on the right tarsus. (11)

To cover the wound on the dorsal head of this bald eagle required skin with feathers large enough to cover the area. The medial thigh was chosen as the donor site because it had those characteristics. A full-thickness graft was elected because of the availability of sufficient tissue. This also alleviated the need to mesh the graft to cover the large surface area. Mesh skin grafts are grafts with slits cut in parallel, staggered rows and are often elected to allow drainage in the case of seroma formation, which was considered unlikely in this case. (1,12) The regrowth of feathers on the dorsal head was critical for the release of the bird. If feathers did not regrow within the grafted skin, the bird would be susceptible to scalp sunburn or frostbite. (13,14) By electing a nonmesh, full-thickness graft, potentially fewer feather follicles were disrupted, maximizing postgraft feather regrowth.

When placing flaps and grafts, proper alignment of the feather follicles is important to prevent excessive preening that could lead to feather damage or interfere with flight. (2,9) In this case, attention to feather-follicle alignment was attempted, but once the graft was removed from the inguinal flap, and the feathers plucked, it was challenging to visualize the direction of feather growth. To attain proper functionality, specific attention should be paid to feather follicle alignment when placing the graft.

The success of this full-thickness skin graft required 4 components. First, trephination of the skull to allow advancement of the vascular supply from the meninges to the granulation bed of the dorsal skull. This robust blood supply provided a more homogenous granulation bed for inosculation of the graft. Second, initial wound management, consisting of bandages and ointment application, was vital to ensure the recipient graft site remained healthy before graft placement. Topical silver sulfadiazine cream was chosen because of its antimicrobial spectrum of action, antifungal properties, and promotion of epithelialization while being able to penetrate eschars and necrotic tissue. (13) Third, the full-thickness skin graft needed to be prepared before it could be applied to the granulation bed. Maintaining moisture of the skin graft and removing all unnecessary tissue allowed for better contact to the recipient graft site. Fourth, use of the tie-over bandage was instrumental in securing the graft in place to prevent shearing while inosculation occurred. (15)

In this case report of a full-thickness skin graft in a bald eagle, postoperative care was minimal, and healing was complete in 6 weeks after the initial operation. We recommend that this technique be considered in cases of large, open, dorsal head wounds to hasten healing time.

References

(1.) Stroud PK, Amalsadvala T, Swaim SF. The use of skin flaps and grafts for wound management in raptors. J Avian Med Surg. 2003; 17(2):78-85.

(2.) Hannon DE, Swaim SF, Milton JL. et al. Full-thickness mesh skin grafts in two great horned owls (Bubo virginianus). J Zoo Wildl Med. 1993;24(4): 539-552.

(3.) Hannon DE, McGhee NW, Weber TD. Use of a single pedicle advancement flap for wound repair in a great horned owl (Bubo virginiaus). Proc Annu Conf Assoc Avian Vet. 1995:285-289.

(4.) Malley AD, Whitbread TJ. The integument. In: Benyon PE, ed. BSAVA Manual of Raptors, Pigeons, and Waterfowl. Ames, IA: Iowa State Press; 1996:129-139.

(5.) Gentz EJ, Linn KA. Use of a dorsal cervical single pedicle advancement flap in 3 birds with cranial skin defects. J Avian Med Surg. 2000; 14(1):31-36.

(6.) Kozar M, Molnar L, Trbolova A, Kozarova I. Application of a single vascularised skin flap in eastern imperial eagle with skin defects. Vet Rec. 2013; 172(16):425.

(7.) Sander S, Whittington JK, Bennett A, et al. Advancement flap as a novel treatment for a pododermatitis lesion in a red-tailed hawk (Buteo jamaicensis). J Avian Med Surg. 2013;27(4):294-300.

(8.) Hernandez-Divers SJ. Hernandez-Divers SM. Xenogeneic grafts using porcine small intestinal submucosa in the repair of skin defects in 4 birds. J Avian Med Surg. 2003; 17(4):224-234.

(9.) Ferrell ST. Avian integumentary surgery. Semin Avian Exotic Pet Med. 2002;1 1(3): 125-135.

(10.) Swaim SF. Skin grafts. Vet Clin North Am Small Anim Pract. 1990;20(1):147-175.

(11.) Johnson JH, Schumacher J, McClure SR, Jensen JM. Use of a full-thickness autograft on the tarsus of an ostrich. J Am Vet Med Assoc. 1994;205(7): 1019-1020.

(12.) Pope ER. Mesh skin grafting. Vet Clin North Am Small Anim Pract. 1990;20(1): 177-187.

(13.) Burke HF, Swaim SF, Amalsadvala T. Review of wound management in raptors. J Avian Med Surg. 2002;16(3): 180-191.

(14.) Heidenreich M. Birds of Prey: Medicine and Management. Maiden, MA: Blackwell Science; 1997.

(15.) Beldon P. What you need to know about skin grafts and donor site wounds. Wound Essentials. 2007;2: 149-155.

Lauren P. Kane, DVM, MS, Trenton C. Shrader, DVM, and R. Coleen Stice, MD

From the Henry Doorly Zoo and Aquarium. 3701 S 10th St. Omaha. NE 68107, USA (Kane. Shrader): Metropolitan Plastic & Reconstructive Surgery, 17030 Lakeside Hills Plaza. Omaha, NE 68130. USA (Stice). Present address (Shrader): Lincoln Children's Zoo. 1222 S 25th St, Lincoln, NE 68502, USA.

Caption: Figure 1. A subadult, male bald eagle that presented with a large eschar on its dorsal head, suspected to be caused by an electrical injury.

Caption: Figure 2. The subadult bald eagle described in Figure 1 after removal of the eschar and trephining the cranium. Note the healthy granulation tissue.

Caption: Figure 3. The subadult bald eagle described in Figure 1, at 10 days after a full-thickness skin graft. Note the near complete vascularization and adherence of the graft with an approximately 90% acceptance of the skin graft.

Caption: Figure 4. The subadult bald eagle described in Figure I at 2 weeks after a successful full-thickness skin graft. Note the beginning growth of new feathers (arrow).
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Title Annotation:Clinical Report
Author:Kane, Lauren P.; Shrader, Trenton C.; Stice, R. Coleen
Publication:Journal of Avian Medicine and Surgery
Date:Jun 1, 2019
Words:2842
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