Advancement flap as a novel treatment for a pododermatitis lesion in a red-tailed hawk (Buteo jamaicensis).
Key words: pododermatitis, bumblefoot, advancement flap, raptor, avian, red-tailed hawk, Buteo jamaicensis
A subadult male red-tailed hawk (Buteo jamaicensis), weighing 830 g and with a body condition score of 1.5 of 5, was presented to the University of Illinois Wildlife Medical Clinic, Urbana, IL, USA, after being found unable to fly. Physical examination and survey radiographs revealed a comminuted fracture of the left distal tibiotarsal bone with proximolateral displacement of the distal fracture segment, all of which was surrounded by a well-defined callus. The right second digit had experienced traumatic amputation at the level of the proximal interphalangeal joint, and an active periosteal response with bone lysis was present at this site. The cause of the injuries was undetermined. No other injuries were observed, which indicated that the hawk's inability to fly was likely caused by debilitation. Empirical treatment was initiated with butorphanol (2-4 mg/kg IM ql2h; Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA, USA), carprofen (1 mg/kg PO ql2h; Rimadyl, Pfizer Animal Health, Exton, PA, USA), amoxicillin trihydrate with clavulanate potassium (75 mg/kg PO ql2h; Clavamox, Pfizer Animal Health), hetastarch (1.25 mL/kg/h IO; Hextend, Abbott Laboratories, Abbott Park, IL, USA), and isotonic fluid support (lactated Ringer's solution, 4.2 mL/kg/h IO). Once the hawk was stabilized, treatment included surgical amputation of the right second digit at the tarsometatarsal-phalangeal joint, during which 8 gentamicin-impregnated polymethyl methacrylate beads (1 g in 20 g polymethyl methacrylate beads; APP Pharmaceuticals, LLC, Schaumberg, IL, USA) were placed at the site for local antibiotic therapy. A culture of the site was not collected at the time of surgery because of the prior initiation of antimicrobial therapy. The left tibiotarsal fracture was stabilized by using a type 1 external skeletal fixator; however, mild medial angulation of the distal tibiotarsus was present after surgery.
The first signs of pododermatitis, bilateral redness and smoothing of the epithelium on the plantar aspect of the feet, began 5 days before surgical stabilization of the left tibiotarsal fracture. Over the next several months, a multitude of treatments and preventative measures that combined environmental, medical, and surgical strategies were implemented to control the persistent pododermatitis. Perches were routinely rotated to provide variation in shape, size, and texture. Regular cleaning of the perches and plantar aspects of the feet with dilute chlorhexidine (1:40, 0.05% solution) was performed to minimize exposure of the inflamed, damaged skin to bacterial contaminants. Topical therapies included the application of camphor spirits (CamphoPhenique, Bayer HealthCare LLC, Morristown, NJ, USA) and Bag Balm (Dairy Association Co Inc, Lyndonville, VT, USA) or 1% silver sulfadiazine cream used in conjunction with bandaging. Bandaging techniques were alternated and included application of commercially available digital corn pads to the affected tissue, ball bandages, custom fitted rubber booties with and without an indented area overlying the metatarsal pad, mattress foam, and donut bandage wraps. The pododermatitis associated with the left foot resolved through medical management, with lesions peaking at grade II/VII. (1) The lesion associated with the metatarsal pad on the right foot (grade V/VII) (the side with the previously mentioned digit amputation) persisted despite treatment and was consistently more severe than the left. (1)
As the condition of the right foot deteriorated, additional treatments, including surgical debridement and closure, were used. Aerobic culture of the wound yielded Streptococcus species, Pseudomonas species, and coliform bacteria. Enrofloxacin (15 mg/kg PO q24h; Baytril, Bayer Animal Health, Shawnee Mission, KS, USA) and amoxicillin trihydrate with clavulanate potassium (75 mg/kg PO ql2h) were administered based on antimicrobial sensitivity testing. Hygroscopic therapy by using 50% dextrose soaked dressings applied to the plantar aspect of the foot was used for topical antimicrobial effects. Surgical wound debridement and primary closure was attempted 3 times by using simple interrupted, horizontal mattress, and far-far-near-near suture patterns, respectively. Each of these attempts resulted in wound dehiscence. The hawk was frequently observed weight bearing preferentially on the left limb throughout this period.
Seven and a half months after admission, the primary pododermatitis lesion on the right foot encompassed the entire metatarsal pad (Fig 1). The skin and soft tissue on the plantar aspect of the foot had ulcerated, which resulted in tendon sheath exposure. The lesion was well circumscribed, with no exudate. The hawk was placed under general anesthesia by using mask induction with 5% isoflurane in oxygen, followed by intubation with a 3.5-mm internal diameter noncuffed endotracheal tube, and anesthesia was maintained at 1.5%-3% isoflurane. During surgery, lactated Ringer's solution (10 mL/kg/h) was administered through a 24-gauge intravenous catheter in the left medial metatarsal vein. The hawk was placed in dorsal recumbency and the right foot was prepared for aseptic surgery. The granulation tissue at the wound edge was bluntly dissected and undermined circumferentially, while hemorrhage was controlled with bipolar electrosurgical forceps and direct pressure. Sharp dissection was used to separate the healthy tissue surrounding the wound from the ulcerated metatarsal pad. The wound was debrided deep to the level of the tendon sheaths, and the chronic granulation tissue and the epithelializing edge were resected. Surgical scissors were used to create a full-thickness skin incision that incorporated the subcutaneous tissue. The incision originated at the abaxial wound edge and was extended distally to the interdigital skin between digits 3 and 4, to a point immediately axial to the fourth digit (Fig 2). A second incision was made from the axial edge of the wound to the interdigital skin just abaxial to the third digit. The corresponding interdigital skin on the dorsal surface of the foot was also incised to create a single pedicle advancement flap. The pedicle was made as wide as possible (1 cm) to preserve blood flow to the flap. The double layer of interdigital skin was split by using microsurgical instruments and 3.5x surgical loupes. Great care was taken to preserve the small blood vessels between the dorsal and plantar skin. The resulting skin flap, thus, was twice as long as the skin web (2 cm) and twice as long as the pedicle. The leading edge of the flap was advanced over the defect created by debriding the wound so that the entire lesion was covered with healthy foot skin and the interdigital web was eliminated. The flap was examined to assess viability of tissue at the leading edge, and approximately 3 mm was trimmed to optimize the coverage of the defect by the flap tissue without creating excess tension on the flap. Simple interrupted subcutaneous sutures of 4-0 polydioxanone (PDS, Novartis Animal Health, Greensboro, NC, USA) were used to secure the flap to the recipient bed. Simple interrupted sutures of 4-0 nylon (Ethilon, Novartis Animal Health) were placed in the skin along the flap edges. A bandage was applied to the foot incorporating cast padding in the shape of a donut to avoid pressure on the flap during weight bearing.
Two weeks after surgery, a 2-mm scab at the leading edge of the flap resulted in partial dehiscence, which was managed conservatively through wound care. Four weeks after surgery, this area had not healed. Surgical debridement was performed, with the hawk under general anesthesia as previously described, and the wound was closed with 4-0 nylon horizontal mattress sutures. A donut bandage was applied until the incision was healed (Fig 3). At 58 days after surgery, the hawk was released to a federally licensed wildlife rehabilitator for flight conditioning and evaluation of release status. Over the next several months, the bird was housed in a large outdoor flight enclosure and demonstrated appropriate ability to fly and perch; however, the slight angulation that persisted in the healed left tibiotarsus in addition to the missing digit on the contralateral foot resulted in some difficulty in landing on perches and grasping items. The animal was eventually deemed nonreleasable and subsequently euthanatized because of an inability to apprehend live prey.
This case report describes the medical and surgical managemcnt of chronic pododermatitis that developed in a red-tailed hawk secondary to prolonged captive care and altered weight beating on the pelvic limbs because of orthopedic injury. A single pedicle advancement flap was applied successfully to cover and heal the pododermatitis lesion in this hawk. To our knowledge, this is the first report of a single pedicle advancement flap being used to cover a pododermatitis lesion in a bird.
Pododcrmatitis, or bumblcfoot, is a general term for inflammation or degenerative conditions of the avian foot. (l-5) It is characterized by varying degrees of swelling, excoriation, ulceration, cellulitis, and abscessation of the plantar aspect of the foot. (l,3-4) Captive waterfowl and raptors are at increased risk for developing this condition because of the heavy-bodied nature of these birds and a propensity to spend significant amounts of time standing, but it can develop in any bird with improper perches or substrate, poor nutrition, poor health, overgrown talons, or obesity, or in birds living in unsanitary conditions. (l-12) Pododermatitis also can occur secondary to infectious or parasitic diseases, penetrating foot wounds, or leg injuries that affect normal gait and weight distribution. (3-5,8)
Epithelial damage that occurs secondary to asymmetric weight bearing on the metatarsal pad, in this case, potentially caused by the contralateral tibiotarsal fracture and repair, causes reduced circulation, microepithelial damage, local impairment of the immune system, and, ultimately, invasion of opportunistic pathogens. (1,4,6,7,13,14) Staphylococcus aureus is commonly isolated from infected lesions, although Escherichia coli, Corynebacterium species, Pseudomonas species, and yeast are also routinely cultured. (4,7,10) Several scales are used to grade the severity of pododermatitis in a given patient. In this case we used a grade I-VII scale. (1) With this scale, grade I lesions are characterized by desquamation of small areas on the plantar foot surfaces with the presence of small, shiny pink areas and peeling or flaking of the skin on the legs and feet. (1) The severity of lesions progresses to grade VII, which is defined by the presence of osteomyelitis. (1) In this case, lesions were most commonly classified as grade II (smooth, thinly surfaced, circumscribed area on the plantar metatarsal pad; no distinct ulceration present) or grade V (cellulitis of the tissue surrounding a necrotic plug in an ulcer of the metatarsal pad; entire metatarsal pad may be affected; digits or foot may also be edematous; necrotic debris may start to accumulate in the metatarsal area, which suggests infection of the tendon sheaths; severe lameness, generally a chronic lesion). (1)
Pododermatitis is easier to prevent than to treat. The plantar location of the lesion is constantly under forces of pressure, movement, and contusion as well as exposure to contaminants. (11,15) Spontaneous resolution is rare and, if left untreated, pododermatitis is progressive and can lead to crippling deformities, sepsis, quality of life concerns, and death. (4,12,15) Therefore, once present, efforts must be made to identify and correct the inciting cause in addition to managing the wound itself by reducing local inflammation, initiating antibacterial therapy, and establishing drainage as needed. (1,2,4,6,9,15)
Conservative treatment options include a combination of environmental and medical methods. Environmental approaches incorporate padding perches with rope, cohesive tape, indoor-outdoor carpeting, mattress padding, or other soft material, and encouraging flight. (1,2,5,7-10,13-15) Vertically oriented enclosure bars are also beneficial because they help to prevent trauma to the foot pads when bars are gripped. (1) Medical therapies include the application of topical agents to the foot such as products intended to toughen the plantar skin of the foot (eg, camphor spirits, liquid bandage) or softening agents (eg, bag balm ointment), the use of which depends on the character of the foot (ie, thinning epithelium versus corns and thick keratin layers). (2,5,7-10,13-15) Antimicrobial and anti-inflammatory products (eg, dimethylsulfoxide, hemorrhoid cream, triple antibiotic ointment, silver sulfadiazine cream) as well as hypertonic footbaths (eg, hypertonic saline solution, magnesium sulfate) provide local control of infection and inflammation. (2,5,7-10,13-15)
Bandaging to alter the weight-bearing surface of the affected foot alleviates pressure directly applied to the pododermatitis lesions, which is often necessary for healing. (2,8,9,15) Bandaging techniques previously described for the treatment of pododermatitis are application of commercially available digital corn pads, ball bandages, custom-fitted rubber booties with and without modification of the orthotic surface overlying any lesions, mattress foam, digit wraps, and donut bandage wraps. (2,5,7-10,13-15) Systemic medical therapy includes systemic antibiotic and anti-inflammatory medications. (2,5,7-10,13-15) Advanced cases of pododermatitis may warrant surgical debridement of fibrotic and exudative material as well as attempts to close the defect with purse-string sutures, tension-relieving sutures, or primary closure. (1,4,7,9,13,15,16) In addition, intensified local antibiotic therapy is provided in some cases by implanting antibiotic-impregnated polymethyl methacrylate beads. (17) Despite these attempts, treatment failure is common and relapse can happen in captivity weeks to years after initial resolution of signs. (15)
Skin flaps are used on large dermal defects in which primary closure is not possible. (10) A skin flap is composed of both skin and subcutaneous tissue that remains attached to its blood supply via a pedicle that is the base of the flap. The flap is then rotated or stretched to cover a skin defect. (18-20) Flaps boost circulation to ischemic regions and provide coverage overlying cavities and soft-tissue structures, such as nerves, vessels, and tendons that are susceptible to trauma and exposure necrosis. (20) They can be used as immediate coverage in areas where padding and durability are necessary. (18) Advancement flaps bypass many of the potential problems associated with healing by second intention, including scarring, contracture, and poor or prolonged healing by minimizing the amount of contraction and epithelialization of a wound during healing. (20)
The most common types of skin flaps are single pedicle advancement, rotation, and transposition flaps. (20) Flaps are classified based on their blood supply, tissues involved, and location of origin in relationship to the recipient bed. Regardless of type, elasticity of the skin and tension on the flap must be considered. (19,21) To preserve vascularization throughout the entirety of the flap, the length of a single pedicle advancement flap must be no more than twice that of the base. (20) As such, a properly developed and handled flap can survive on an avascular tissue bed. The recipient bed should be free of debris, necrotic tissue, and infection for optimal results. Chronic granulation tissue should be excised, and the wound borders should be freshened. (20) Flap necrosis occurs when circulation throughout the flap is inadequate to meet the metabolic demands of the tissue, as occurs with infection, exposure to toxic agents, inadequate blood supply, or excessive tension on the flap. (19,20) Flap color, temperature, pain sensation, and bleeding can be used as indicators of flap health during healing but should be evaluated together because each factor can be deceptive when evaluated alone. (20) For example, flaps are partially denervated as they are moved, thus poor pain sensation of the site does not accurately predict the likelihood of flap survival. (20) Skin flaps in avian patients have been most commonly reported as a technique to cover dorsal cervical and dorsal antebrachial wounds. (21-24) These reports include the repair of a large open wound on the distal antebrachium of a great horned owl (Bubo virginianus) (22); degloving injuries on the heads of northern goshawks (Accipiter gentilis) (23); and wounds on the head of a red-tailed hawk, rock dove (Columba livia), and ring-necked pheasant (Phasianus colchicus). (24)
In this case, pododermatitis persisted despite established management methods. Repeated attempts to medically and surgically address the lesion resulted in exuberant granulation tissue and scar tissue formation at the site. These types of tissue classically have a poor blood supply and, therefore, decreased healing capacity. (10,20,21) Previous failure, the formation of minimally vascular tissue at the site, and the relatively large size of the defect contributed to the development of fragile epithelium surrounding the defect and poor likelihood for the wound to heal with further attempts at traditional techniques. This surgery was designed to cover the defect with fresh, keratinized, healthy foot skin, which would be better able to hold up to the impact and pressures withstood at the plantar surface of the foot. The interdigital skin was chosen for this purpose because it is thick, tough, and scaly, and is not required to maintain function of the foot. (18) As with any surgery, scar tissue forms during healing, thus failure is more likely with subsequent attempts at primary closure. (6,10,20)
In this case report, we described the successful application of a single pedicle advancement flap to cover and heal a pododermatitis lesion in a red-tailed hawk. Postoperative care was minimal, and healing was complete 6 weeks after the initial operation. Despite improvements after extended medical and surgical management, the pododermatitis in this case was likely complicated by an altered weight-bearing surface because of digit 2 amputation of the right limb and angulation of the left limb secondary to injuries sustained before presentation for captive care as well as an extended time in captivity without an opportunity for flight. We recommend that this technique be used in cases of pododermatitis as early as grade IV/VII after environmental and medical treatment options have proven unsuccessful.
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Samantha Sander, DVM, Julia K. Whittington, DVM, Avery Bennett, DVM, MS, Dipl ACVS, Anne Burgdorf-Moisuk, DVM, and Mark A. Mitchell, DVM, MS, PhD, Dipl ECZM (Herpetology)
From the Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, 1008 W Hazelwood Dr, Urbana, IL 61802, USA (Sander, Whittington, Bennett, Burgdorf-Moisuk, Mitchell). Present address: Smithsonian Institution National Zoological Park, PO Box 37012, MRC 5502, Washington, DC 20013-7012, USA (Sander); Lauderdale Veterinary Specialists, 3217 NW 10th Terr, Fort Lauderdale, FL 33309, USA (Bennett); and Saint Louis Zoo Animal Health Department, 1 Government Dr, St Louis, MO 63110. USA (Burgdorf-Moisuk).
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|Title Annotation:||Clinical Reports|
|Author:||Sander, Samantha; Whittington, Julia K.; Bennett, Avery; Burgdorf-Moisuk, Anne; Mitchell, Mark A.|
|Publication:||Journal of Avian Medicine and Surgery|
|Date:||Dec 1, 2013|
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