Abstract

A ring-necked pheasant (Phasianus colchicus), and a rock dove (Columba livia), each with a large soft tissue wound on the head resulting in exposed skull, were treated with wound debridement, removal of necrotic bone, and skin grafting using a single pedicle advancement flap from the adjacent dorsal cervical skin. The wound in the pheasant healed without complication. The initial flap attempted with the rock dove necrosed, but a second single pedicle advancement flap elevated from the dorsal cervical skin healed successfully. The final result in both birds was complete coverage of the defect with full-thickness skin. Use of single pedicle advancement flaps mobilized from dorsal cervical skin may expedite healing of large soft tissue wounds of the head in birds, especially when the skull is exposed.

Introduction

Injuries to the crown of the head can occur in captive, free-ranging, and companion birds as a result of collisions or attacks by other animals.^9,12 Although simple soft tissue lacerations often heal without intervention, injuries that expose the cranium can result in chronic, nonhealing wounds.^9,12 The presence of devitalized bone impedes the formation of granulation tissue and migration of epithelial cells.^14,19 In addition, the skin over the head is firmly attached to the underlying skull, making primary or delayed closure of large wounds difficult once the skin edges have begun to fibrose.^5,6 Even when closure is possible, tension created by apposing the edges of large wounds can cause eyelid deformation and exposure keratitis.^1,12

Reconstructive techniques can be used to provide epithelial coverage of defects that are difficult or impossible to close primarily. Free skin grafting, in which a full or partial thickness section of dermis and epidermis is detached from a distant donor site and transferred to a wound bed, is routinely used in mammals^14,16,19 and has been reported in birds^8,10. Pedicle grafts, or flaps, are sections of skin and subcutaneous tissue that are rotated or advanced from a donor site to cover a defect. A portion of a pedicle graft remains continuous with the donor site to maintain blood supply to the subdermal plexus within the flap.^15,16,19 Because of their intrinsic blood supply, properly designed flaps have a greater chance of remaining viable than do free grafts, especially when the recipient site is poorly vascularized. In addition, because pedicle grafts contain full-thickness skin and subcutaneous tissue, they can provide normal feather coverage if they contain pterylae. However, the use of pedicle flaps requires the presence of relatively loose, mobile skin adjacent to the defect. A single pedicle advancement flap was used to close a wing wound in a great horned owl (Bubo virginianus),⁷ and advancement flaps have been recommended in raptors to reconstruct wounds involving loss of tissue on the head.¹²

Case 1

A 1.12-kg, adult female ring-necked pheasant (Phasianus colchicus) from a game farm was presented with cranial trauma. The bird was alert and responsive with normal vital signs. A full-thickness skin wound, measuring 2.5×2.5 cm, exposed the dorsal cranium. The wound edges were inflamed and edematous, and the exposed skull was desiccated. The wound was irrigated with 0.05% chlorhexidine acetate solution, treated topically with a polymyxin B sulfate/bacitracin zinc/neomycin ointment, and covered with a semi-occlusive bandage. The bird was treated with trimethoprim-sulfamethoxazole (100 mg/kg PO BID) for 10 days. Wound irrigation was repeated and the dressing replaced every other day for 3 weeks. After 3 weeks, the wound was unchanged in size, no granulation tissue was evident, and the exposed portion of the skull appeared necrotic on the surface. Surgery was elected to expedite healing of the wound.

The bird was premedicated with midazolam (2 mg/kg, IM). After 15 min, it was mask induced, intubated and maintained under anesthesia with 2.5% isoflurane. The pheasant was placed in sternal recumbency. Feathers surrounding the wound and covering the dorsal aspect of the neck were plucked, and the area was prepared for aseptic surgery with chlorhexidine acetate solution and sterile physiologic saline solution. The bird was covered with a fenestrated, transparent, adhesive surgical drape.

Skin edges surrounding the wound were debrided and undermined. Lempert rongeurs were used to lift a thin layer of devitalized bone from the calvarium. The skin edges involving the rostral quarter of the wound were apposed in a single interrupted pattern with 4-0 polyglyconate. The remainder of the wound was closed by using a single pedicle advancement flap developed from the adjacent dorsal cervical area. Two incisions measuring 3.5 cm long and 2.5 cm apart were initiated at the caudal margin of the wound and extended caudally along the bird’s neck. These incisions diverged caudal to the wound, leaving the base of the flap slightly wider than its leading edge. The skin and associated subcutaneous tissues between these incisions were elevated and the flap was advanced rostrally to cover the defect. The flap was sutured in place using 4-0 polyglyconate in a simple interrupted pattern.

The graft site was monitored daily, and healing progressed without complications. Sutures were removed 2 weeks after surgery, and the pheasant was discharged from the hospital.

Case 2

A 0.26-kg, adult rock dove (Columba livia) of unknown gender was presented for treatment after being found along the roadside. The bird was in thin body condition and was missing several primary feathers. The calvarium was exposed through a 2.0×1.5 cm soft tissue defect on the dorsum of the head. The dove was initially treated with dexamethasone sodium phosphate (4 mg/kg, IM) and lactated Ringer’s solution (50 ml/kg, SC). The wound was irrigated with 0.05% chlorhexidine acetate solution, after which polymyxin B sulfate/bacitracin zinc/neomycin ointment was applied. A semi-occlusive bandage was placed over the wound. Trimethoprim-sulfamethoxazole (100 mg/kg PO BID) was administered for ten days.

The wound was irrigated, treated with antibiotic ointment, and bandaged daily, but the bird frequently dislodged the bandage. Surgical debridement and closure of the wound was elected because, after 10 days, no granulation tissue was evident and the exposed calvarium appeared devitalized.

The bird was premedicated with midazolam (2 mg/kg, IM) and glycopyrolate (0.01 mg/kg, IM), induced by mask, intubated, and maintained under anesthesia on 2.5% isoflurane in oxygen. The dove was placed in sternal recumbency, and the dorsal aspect of its head and neck were prepared for aseptic surgery and draped as in case 1. Rongeurs were used to remove desiccated bone from the surface of the calvarium until a small amount of hemorrhage was evident. Skin edges surrounding the defect were debrided and undermined. The rostral skin edges were apposed by using 4-0 polyglyconate in a simple interrupted pattern. A dorsal cervical single pedicle advancement flap was developed as described in the pheasant (case 1). In this bird less subcutaneous tissue was elevated with the skin, and the lateral aspects of the flap converged slightly, rather than diverged, toward the base. The graft was advanced rostrally to cover the defect and was sutured in place with 4-0 polyglyconate in a simple interrupted pattern. After surgery, the bird was given lactated Ringer’s solution (20 ml/kg divided between IV and SC routes). The midazolam was reversed with flumazenil (0.04 mg/kg), and the bird was given butorphanol (0.1 mg/kg, IM) for postoperative analgesia.

Within 8 days after surgery, the portion of the flap covering the defect appeared devitalized. The bird was anesthetized and prepared for aseptic surgery, and the necrotic skin covering the defect was debrided. The wound was irrigated with sterile physiologic saline solution, and a new single pedicle flap was developed from the cervical skin caudal to the original defect. To ensure that the base of the flap was broader than its leading edge, divergent lateral incisions were created. Despite the fact that this was the second pedicle graft developed from the dorsal cervical skin, the flap was easily mobilized to cover the defect, with very little tension on the graft. The skin flap was sutured in place using 4-0 polyglyconate in a simple interrupted pattern. This repair healed without incident, and sutures were removed 2 weeks after surgery. The bird was released 4 days later.

Discussion

Lacerations and abrasions of the skin on the head can usually heal without surgical intervention.⁹ In both these birds, healing by second intention was delayed because of the presence of devitalized bone. Removal of the necrotic bone may have allowed healing by second intention.

We chose to use a single pedicle advancement flap in these birds for several reasons. Closure by either contraction or direct apposition might have created sufficient traction on the upper eyelids to affect their function and result in exposure keratitis because of the size and location of the wounds.^1,12 The relatively loose, mobile skin in the dorsal cervical area⁶ adjacent to the wounds made it feasible to develop local flaps and to avoid the additional operative time and donor site morbidity that would have accompanied harvesting free grafts. To preserve normal feather orientation on the dorsum of the head, the flaps were advanced rather than rotated into place.¹² A similar technique, using twin Z-plasties to create an advancement flap has been used with success in raptors to cover skin defects involving the head.¹² A bipedicle flap, which makes use of a releasing incision to allow closure of an adjacent defect, might have been used in these birds; however, this type of flap can have limited mobility and primary closure of the donor defect can be difficult.¹⁹ Single pedicle advancement was simple to perform and resulted in rapid healing in these birds.

Two technical errors probably led to the necrosis of the first flap created in the dove. The shallow dissection of subcutaneous tissue in this flap may have compromised its subdermal plexus and this was likely exacerbated by the caudal convergence of the lateral incisions used to define the flap. Narrowing of the base of a flap decreases the blood supply available to perfuse the subdermal plexus.^15,19 In areas where the skin is quite mobile, an attempt to create parallel side incisions can result in inadvertent convergence of the sides if lateral tension is applied to the skin for stability during incision. A strategy suggested to compensate for this tendency is to make the lateral incisions diverge.¹³ Axial pattern flaps, which include a direct cutaneous artery for blood supply, can be narrowed at the base, providing the artery is not compromised.^14,15 To our knowledge, use of axial pattern flaps has not yet been reported in birds.

The presence of devitalized bone was a factor contributing to the delayed healing of the wounds in both birds. Although both birds presented with a portion of the skull already exposed and desiccated, we attempted to hydrate the wounds to encourage the tissue to granulate^16,19 and to prevent bone necrosis. The semi-occlusive dressing (Tegaderm, 3M Animal Care Products, St. Paul, MN) used in these birds has been recommended for coverage of wounds that heal by second intention, but an occlusive hydrocolloid dressing might have been more effective to moisten the wounds.¹ In the dove, the wound dried intermittently when the bird dislodged the dressing. Suturing or supergluing the dressing in place or applying a tie-over bandage might have been more successful in keeping the wound covered. Once necrotic tissue was debrided and the defects were covered with advancement flaps, wound healing was relatively rapid and results were functional. Because prolonged captivity of wild birds can lead to an increase in complications such as inappetence, foot infections, aspergillosis, and stress-related death^2,3,4,18 use of skin flaps to close large head wounds may improve the chances for a successful outcome.

Although dorsal head wounds that are difficult or impossible to repair by primary closure may heal by second intention, we recommend the use of dorsal cervical single pedicle advancement flaps to expedite healing.

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