Use of skin stretching techniques before bilateral caudal superficial epigastric axial flaps in a dog with severe burns

Abstract

This report describes how 2 days of skin stretching facilitated a tension-free closure of single event bilateral caudal superficial epigastric flaps in a dog with severe hindquarter burns. Full healing at all surgical sites with only minor dehiscence and without further treatment or abnormalities of gait or coat regrowth was achieved.

Case description

A 2-year-old female standard poodle was referred to the Western College of Veterinary Medicine (WCVM) for reconstructive surgery following extensive full thickness burns. The dog was a passenger in a vehicle that was involved in an accident and subsequently caught fire. The dog sustained burn injuries to the caudal dorsum, inner thighs, buttocks, perineum, and vulva (Figure 1). The initial recovery was managed by the referring veterinarian, and included debridement of necrotic tissue, daily hydrotherapy treatments, and bandaging with grocery grade honey as the primary layer. Medications administered included a fentanyl patch (Duragesic; ALZA Corporation, Palo Alto, California, USA) 75 μg/h transdermally, amoxicillin/clavulanic acid (Clavaseptin; Vétoquinol, Lavaltrie, Quebec), 375 mg, PO, q12h, and enrofloxacin (Baytril; Bayer, Shawnee Mission, Kansas, USA), 450 mg, PO, q24h.

Figure 1.

Photograph of the burn wounds on the caudal and inner thighs of the patient at presentation to our facility.

On presentation to WCVM, approximately 2 wk after the trauma, the dog was quiet, alert, and appeared comfortable. Physical examination revealed a stiff and short-strided hind limb gait, due to the contraction of wound margins. The patient was in thin body condition (body condition score 3/9), and had an estimated 20% loss of body weight since the trauma. Due to the wounds, her abdomen was not palpated for abnormalities. Blood glucose testing revealed a slight hypoglycemia [4.0 mmol/L; reference interval (RI): 4.4 to 7.2 mmol/L]. No other abnormalities were detected on physical and laboratory examination.

The burn wounds were most severe on the caudal hind limbs and perineum, where a full thickness skin defect extended over the entire inguinal area, inner and caudal thighs, extending dorsally to the tail base (Figure 1). The defect was almost symmetrical. A healthy granulation bed was present over this large wound, and no debridement was necessary. The tail had an exposed caudal vertebra at the distal end. Smaller wounds were noted on the upper eyelids, left upper and lower lip, dorsal left caudal thorax, and cranial abdomen. These areas also had a healthy granulation tissue covering, and no debridement was needed. Multiple small areas of flaking skin and small healing wounds with scabs were noted over the dog’s legs, trunk, neck, and face.

Bilateral caudal superficial epigastric flaps were planned to cover the major defect on the caudal hind limbs and inner thighs. Skin stretching was performed 2 d before the surgery using the technique described by Pavletic and Trout (1) using Velcro (Velcro Canada, Brampton, Ontario) and cyanoacrylate (KrazyGlue; Westerville, Ohio, USA). To place the skin stretching materials, the patient was sedated using hydromorphone (Hydromorphone hydrochloride; Sandoz Canada, Boucherville, Quebec), 0.5 mg/kg body weight (BW), IV, dexmedetomidine (Dexdomitor; Zoetis, Kalamazoo, Michigan, USA), 0.0015 mg/kg BW, IV, and ketamine (Narketan; Vétoquinol, Lavaltrie, Quebec), 0.5 mg/kg BW, IV. The patient was clipped from the mid-sternum to the pubis, extending to the lateral abdomen and thorax. Velcro with hooks were adhered to the left lateral abdomen with KrazyGlue, while Velcro with loops were adhered to the right lateral abdomen. Once the KrazyGlue had dried, the hook side of the Velcro was stretched ventrally from the left lateral abdomen, and attached to the looped Velcro on the right lateral abdomen (Figure 2). The Velcro distance was shortened every 8 h to continue stretching the skin. The skin was monitored for elasticity. After 48 h there was enough skin recruitment estimated to cover the defect.

Figure 2.

The external skin stretching used before surgery. Typically the patient would wear a bandage over the skin stretching materials to prevent self-mutilation.

The patient was premedicated with hydromorphone (Hydromorphone hydrochloride; Sandoz), 0.05 mg/kg BW, IV, and dexmedetomidine (Dexdomitor; Zoetis), 0.0015 mg/kg BW, IV. To induce anesthesia, ketamine (Narketan; Vétoquinol), 2.5 mg/kg BW, IV and diazepam (Diazepam; Sandoz), 0.25 mg/kg BW, IV were given. Anesthesia was maintained with 0.5% to 1.75% isoflurane (Pharmaceutical partners of Canada; Richmond Hill, Ontario) in 100% oxygen. Ten minutes into the anesthesia, a continuous rate infusion (CRI) of ketamine (Narketan; Vétoquinol), 10 μg/kg BW per hour and remi-fentanyl (Teva Canada; Toronto, Ontario), 10 μg/kg BW per hour were added. An hour into anesthesia, a CRI of lidocaine (Lidocaine Hydrochloride; Pfizer Animal Health, Pfizer Canada, Kirkland, Quebec), 30 mg/kg BW/min lidocaine was started. At the same time, lidocaine (Lidocaine Hydrochloride; Pfizer Canada), 2 mg/kg BW, IV was given. Cefazolin (Cefazolin injection; Hospira, Lake Forrest, Illinois), 22 mg/kg BW, IV was given every 90 min during surgery. Two hours into anesthesia, nitrous oxide was added at a rate of 1.4 L/min. Due to mild hypotension (systolic blood pressure of 80 mmHg and mean arterial pressure of 60 mmHg), dobutamine (dobutamine injection; Hospira), 5 μg/kg BW per minute CRI was started, and a tetrastarch (Voluven; Fresenius Kabi Canada, Mississauga, Ontario) bolus of 5 mg/kg IV was administered over 6 min.

The patient was anesthetized, placed in dorsal recumbency, and prepared and draped for surgery using standard procedure. Bilateral island caudal superficial epigastric axial pattern flaps were developed (Figure 3). A ventral midline abdominal incision was made through the skin, extending from between the second and third nipples to caudal to the last nipple. The flap was undermined deep to the supramammarius muscle and superficial to the external abdominal oblique muscle in a caudal direction. Each flap was elevated and rotated 180° around the caudal aspect of the ipsilateral leg. The lateral margins of each of the 2 donor site sides were apposed at midline without tension to the level of the inguinal area using 2-0 polydioxa-none (PDSII; Ethicon, Guaynabo, Puerto Rico) in a simple continuous pattern. The subcutaneous tissue was closed using 3-0 poliglecaprone 25 (Monocryl; Ethicon) in a simple continuous pattern and the same suture was used to close the skin in an intradermal pattern. The large granulation beds at the caudal aspects of the thighs and buttocks were freshened at the edges where epithelialization was evident. A bridging incision was made between the wound bed and the flap on each side. The flaps were positioned over the wound bed following the lateral edges, and then turned back cranially to cover the remainder of the medial aspects of the wound beds. The subcutaneous skin tissue was closed using 3-0 polydioxanone suture (PDSII; Ethicon) in a simple continuous pattern, and the skin was closed using 3-0 nylon suture (Ethilon; Ethicon) in a simple interrupted pattern. Active drains with vacuum bulbs (Jackson-Pratt Bulb; Cardinal Health, Waukegan, Illinois, USA) were placed on each side.

Figure 3.

Seven days postoperative bilateral caudal superficial epigastric skin flaps.

After surgery, the patient was administered fentanyl (fentanyl citrate; Sandoz) at 3 μg/kg BW per hour, IV, CRI, meloxicam (Metacam, Boeringer Ingelheim; St. Joseph, Missouri, USA), 0.1 mg/kg BW, SC, and ketamine (Narketan; Vétoquinol), 1 mg/kg BW, SC. The dog appeared comfortable and began standing and walking with a normal gait the morning after surgery. Three days after surgery, the patient began squatting normally to urinate and started sleeping in a dorsal position with legs extended. Together the drains produced 48 to 60 mL/d of clear serosanguinous fluid for 6 d after surgery. On the seventh day, fluid decreased to < 10 mL/day, and the drains were removed. Mild dehiscence of approximately 3 cm was noted on the caudal distal portion of each flap 2 d after surgery.

A second surgery was performed 5 d after the initial surgery to debride the tail tip and cover the exposed tail vertebra. At the same time, the 2 small areas of caudal distal flap dehiscence were closed. The patient was pre-medicated with dexmedetomidine (Dexdomitor; Zoetis), 0.002 mg/kg BW, IV, and hydromor-phone (Hydromorphone hydrochloride; Sandoz), 0.05 mg/kg BW, IV. Heavy sedation was achieved with ketamine (Narketan; Vétoquinol), 0.5 mg/kg BW boluses, IV. A regional tail block was also given subcutaneously along the tail using 1 mL of bupivacaine (Bupivacaine HCl Injection 0.5%; Hospira). The tail tip wound was undermined cranially and advanced over the exposed bone. The subcutaneous tissue was closed using 3-0 poliglecaprone 25 (Monocryl; Ethicon) in a simple continuous pattern. The skin was closed using 3-0 nylon suture (Ethilon; Ethicon) in a simple interrupted pattern.

Eight days after surgery the incisions were 95% intact, with several areas of 5 mm length exposure of underlying granulation tissue. The patient was sent home 10 d after surgery with a normal gait, and her major burn wounds fully covered. No further intervention was needed after suture removal. The patient fully healed at all the injury and surgical sites without further dehiscence. There were no gait abnormalities and a full coat of fur grew back in due course.

Discussion

Full thickness burns tend to heal slowly, by contraction and epithelialization, and patients are vulnerable to local and systemic infection due to skin necrosis (1). In the patient we describe, healing by contraction would have led to a gait disturbance and impaired ability to ambulate. Impairment of normal gait was noted when the patient arrived at WCVM, seemingly due to the beginning of contraction at the wound margins. The wounds would also have taken a long time to heal and would have resulted in coverage with fragile epithelium, if indeed coverage of the entire defect could be achieved at all. Wound closure options included skin grafts, advancement flaps, and axial pattern flaps. Axial pattern flaps were chosen in this case because of their robust nature and the availability of donor tissue for the flaps which could be used to cover the major defects present in this dog.

Axial pattern flaps, such as the caudal superficial epigastric flap, incorporate a direct cutaneous artery and vein, and thus supply blood to the subdermal plexus (2). The direct blood supply in an axial flap is advantageous over other reconstructive methods, because it leads to comparably higher skin survival rates (3). Experimental studies and clinical trials have shown that axial pattern flaps can be safely elevated and transferred in a single stage to close major defects in their general radius (2). The axial pattern graft allows the closure of large defects while decreasing the time of open wound management (3).

In 1 retrospective study of 10 caudal superficial epigastric flaps, the mean area of flap survival was 99.96% (4). Small areas of necrosis occurred near the tip of the flap (0.4% of flap surface area), and around a stab incision that was used for an external skeletal fixator (4). Overall, the complications associated with the caudal superficial epigastric flaps were minor and successfully treated with conservative management (4). In another retrospective study of 73 cases of axial pattern flaps in dogs and cats, incisional dehiscence was the most common complication (5). Successful outcomes occurred in 93% of these cases, with approximately 1/3 of cases requiring a second procedure (5). The results in our patient were similar to these findings. Excellent flap survival was noted, with only minor dehiscence, estimated to be maximum 1% of the flap area. We attached the flaps to the recipient bed in a semicircular pattern, and the small area of dehiscence was where there was a confluence of the incision into 3 lines meeting at 1 point.

In order to stretch the skin for simultaneous bilateral flaps, the process of mechanical creep and stress relaxation were used. Mechanical creep is the use of tension applied to the skin over a period of time (6). As the dermal collagen fibers are stretched, they progressively align and compact in the direction of the stretching force (6). As the collagen fibers align, stress relaxation reduces the amount of force that is necessary to maintain a given strength (6). By applying an appropriate amount of force, skin can be recruited and used to cover defects. Skin stretching technique options include external skin stretchers, surgically placed tissue expanders, and walking sutures. Complications of skin stretching can occur if there is continuous stretching beyond maximal mechanical creep. This can result in breakage of dermal collagen fibers and skin damage (7).

The technique we used in this patient was described by Pavletic (8). This technique was used to facilitate the closure of large wounds in several dogs and cats. Use of the technique has also been reported for successful closure of a large wound over the dorsum and flank in a rabbit (9). A recent paper evaluated the use of this technique on the extremities of dogs and found that it was not as amenable to successful closure of large wounds as it has been reported to be on the trunk of small animals (10).

External skin stretching was chosen in this case due to its ease of use, low cost, and to maintain comfort in this hyperesthetic dog. Tissue expanders would require an additional anesthetic event and surgical procedure, whereas skin stretching was achievable with 1 short sedation event (8). The skin stretching was accomplished without disturbance of the many smaller regional wounds in various stages of healing, which would make other methods of skin recruitment vulnerable to tissue compromise, and more painful. The hook side of 2-inch Velcro stripping was adhered to the skin on each side of the patient from the lateral thorax to the lateral flank. Strips of the loop side of the Velcro were then apposed to the hook stripping on one side, stretched under the abdomen and across to adhere to the hook stripping on the contralateral side. The tension was adjusted every 8 h to maintain tension as the skin progressively stretched and relaxed, loosening the overlying Velcro strips, in accordance with published guidelines described by Pavletic (6,8). After 48 h the patient was taken to surgery and the Velcro strips were removed.

Bilateral caudal superficial epigastric flaps without skin stretching has been described in the cat (11). Entire wound coverage was achieved within 1 surgery, with moderate edema and crusting after surgery (11). However, this difference in skin stretching is likely due to the vast difference between the availability of skin in the cat compared to that in most dogs.

Bilateral flaps were indicated in this dog because the wounds were large and almost symmetrical, covering most of the caudal buttock and upper thigh region on each side. Considering that standard poodles have little excess skin, and this dog was in lean body condition, skin stretching was used to decrease the tension that would occur at the donor sites with simultaneous bilateral development of caudal superficial epigastric flaps. In 1 case report, bilateral simultaneous caudal superficial epigastric flaps were raised in a dog and 90% coverage was achieved without the use of skin stretching (12). Considerable tension was noted at closure of the donor sites (12). Three months after surgery, the remainder of the defect was closed during a second surgery (12).

In our patient, the use of skin stretching was primarily intended to provide a tension-free donor site closure. However, an added advantage was expansion of the dimensions of the flaps themselves. It is possible that without this added dimension to the flaps a defect may have remained at the primary site. Skin stretching has been used for the primary purpose of expanding an axial pattern flap to cover a large defect (13) and it is likely that our patient benefitted from this effect as well.

Our patient healed fully at both the donor site and the primary defect site without further treatment. There was no further dehiscence, no gait deficits or abnormalities, and a full coat of fur regrew over all the injured areas and surgical sites. With the use of skin stretching, 100% wound coverage of extensive defects over the caudal thighs and buttocks was achieved in this patient in 1 surgical event. Postoperative complications were minor, and included small areas of dehiscence. With the use of skin stretching, bilateral caudal superficial epigastric flaps can be used in dogs to cover major wounds on the caudal thighs. CVJ