Central hemimaxillectomy and reconstruction using a superficial temporal artery axial pattern flap in a domestic short hair cat

Abstract

A 2-year old, neutered male domestic short hair cat presented with a large mass involving the right upper lip and underlying gingiva. A previous attempt at mass excision had failed, and the histopathological diagnosis was reported to be a fibrosarcoma. The cat was otherwise in good health.

A central hemimaxillectomy was performed with extensive soft-tissue dissection and maxillofacial reconstruction achieved using an axial pattern flap based on the superficial temporal artery. This is the first reported clinical case of the use of the superficial temporal artery axial pattern flap in the cat. Histopathology identified a periodontal fibromatous epulis.

A3-year-old neutered male domestic short hair cat presented for treatment of a maxillofacial mass. The mass involved the right upper lip and underlying gingiva and had been present for at least 2 years, growing slowly and progressively during this time. An incisional biopsy of this mass by the referring veterinary surgeon was reported to be a fibrosarcoma. The cat was in good general health, although the size and position of the mass resulted in difficulties in the prehension of food. At the time of presentation, the mass was extensively ulcerated, necrotic and measured approximately 9 cm×5 cm. It involved the entire right upper lip and underlying gingiva to the level of the carnassial tooth (Fig 1A and B). The right submandibular lymph node was enlarged and non-painful. Clinical examination was otherwise considered normal.

Fig 1.

Preoperative appearance of the maxillofacial mass.

Haematology and serum biochemistry were within normal laboratory reference ranges. General anaesthesia was induced with propofol (Rapinovet, Boehringer Ingelheim) 4 mg/kg i.v. and maintained with isoflurane, nitrous oxide and oxygen for radiography of the thorax and maxilla. Left and right lateral and ventrodorsal thoracic radiographs showed no visible evidence of pulmonary metastasis. Ventrodorsal and lateral skull and intraoral radiographssuggested no involvement of the bone underlying the lesion. Fine-needle-aspirates of the submandibular lymph nodes revealed lymphoid hyperplasia. Neoplastic cells were not identified.

Cefazolin (Kefzol, Lilly) 20 mg/kg i.v. was administered before surgery. The mass was sharply excised ‘en bloc’ with margins of 1 cm on all borders and removed from the surgical site. This involved a skin incision dorsally extending from the philtrum to the zygomatic arch and incision ventrally of the labial, gingival and buccal mucosa from caudal to the canine tooth to caudal to the carnassial tooth. These incisions were connected cranially and caudally. Haemostasis was achieved using a combination of simple ligation and electrocautery. A periosteal elevator was used to undermine and reflect mucosa from the underlying bone. A central hemimaxillectomy was performed to remove the section of maxilla between the canine tooth and carnassial tooth using an oscillating saw.

Closure of the defect was achieved using an axial pattern flap (APF) based on the superficialtemporal artery (STA). The landmarks for the base of this flap were the caudal aspect of the zygomatic arch caudally and the lateral orbital rim rostrally (Fig 2). Flap length extended to the dorsal orbital rim of the contralateral eye. The width of the flap was limited by the eye rostrally and the ear caudally and was, therefore, equivalent to the width of the zygomatic arch. Following establishment of the relevant landmarks, the skin was incised and the thin frontalis muscle identified superficial to the fascia of the temporal muscle. The flap was carefully elevated towards its base. Principles of atraumatic tissue handling were adhered to at all times and included the use of skin hooks, atraumatic tissue forceps (DeBakey), haemostasis and the avoidance oftissue drying.

Fig 2.

Dotted line identifies the boundaries of the APF based on the STA.

The flap was rotated 90° and contoured into the facial defect with simple interrupted sutures to the underlying muscle using 2 metric polydioxanone (PDS II, Ethicon). A closed active suction drain was placed beneath the flap and secured to the skin at a distant site with a Chinese finger trap suture of 2 metric polyamide (Ethilon, Ethicon). Intradermal sutures using 2 metric PDS in asimple continuous pattern were placed followed by simple interrupted cruciate mattress sutures in the skin using 2 metric polyamide. Closure of the mucosal defect was performed using a double-layer collagen derivative of porcine submucosa (Vet BioSISt, Cook) secured to the underlying gingiva with simple interrupted sutures of 1.5 metric polyglactin 910 (Vicryl, Ethicon).

The secondary defect was closed by creation of a simple advancement flap, moving tissue from caudal to cranial, adhering to the same principles as described in the preceding discussion. An oesophagostomy tube was placed using a standard technique (Seim & Willard 1997) and secured to the skin with 2 metric polyamide using a Chinese finger trap suture pattern.

Postoperatively, analgesia was provided for the first 24 h with morphine (Morphine sulphate, Medeva) 0.1 mg/kg i.v. every 6 h followed by buprenorphine (Vetergesic, Alstoe Ltd) 0.01 mg/kg i.v. every 8 h for 5 days. Meloxicam (Metacam, Schering Plough) 0.1 mg/kg every 12 h was administered via the oesophagostomy tube for 5 days. Feeding via the oesophagostomy tube was required for 7 days postoperatively by which time the cat was eating normally.

Six days postoperatively, the Vet BioSISt™ appeared necrotic, necessitating general anaesthesia for debridement. Polymethyl methacrylate gentamycin-impregnated beads were placed beneath the skin flap in case of infection developing subsequent to degeneration of the Vet BioSISt™.

The oesophagostomy tube was removed 7 days postoperatively and skin sutures removed 10 days postoperatively. At this stage, the flap demonstrated 98% survival and the mucosal defect was granulating well. The cat was discharged from the hospital 10 days postoperatively. Histopathology identified the mass to be a periodontal fibromatous epulis, and tumour-free margins had been achieved.

A telephone report 14 days later confirmed that the cat was progressing well. The owner reported a dramatic improvement in the cat's activity and general well being. A telephone conversation at 7 months postoperatively confirmed a good functional and cosmetic outcome (Fig 3).

Fig 3.

Good cosmetic outcome at 5 months postoperatively.

Discussion

Neoplasms arising in the oral cavity of cats account for approximately 3–12% of all feline neoplasia (Andrews 1987). A retrospective 10-year survey of 371 neoplasms of the feline oral cavity detected 20 different oral neoplasms, 89% of which were malignant. The most commonly diagnosed tumours in this report were the squamous cell carcinoma (61.2%), fibrosarcoma (12.9%) and fibromatous epulis (7.8%) (Stebbins et al 1989).

The epulides arise from the periodontal stroma and are classified into three different types based on histological appearance: fibromatous epulis; ossifying epulis; and acanthomatous epulis. All three types are benign, although the acanthomatous epulides can exhibit malignant characteristics. The difference between the initialhistopathology result of a fibrosarcoma and the final histopathological diagnosis of a fibromatous periodontal epulis is likely to have resulted from sampling of superficial fibrous tissue.

Optimal treatment of maxillofacial neoplasia involves surgical excision with tumour-free margins, either alone or in combination with radiation therapy. Options for soft-tissue reconstruction are limited, as the skin of the maxillofacial region is relatively immobile compared with the occipital region and trunk. Healing of wounds by second intention or the use of local advancement flaps can lead to cosmetic and functional disturbances of the eyelids, nares or mouth.

APFs have been developed in dogs and cats to augment the surgeon's treatment options for the management of wounds with large skin deficits (Pavletic 1999). APFs incorporate a direct cutaneous artery and vein at the flap base and, therefore, have enhanced perfusion compared with subdermal plexus flaps (Pavletic 1999). An APF based on the cutaneous branch of the STA has been described experimentally in the cat (Fahie and Smith 1997, Fahie et al 1998), and both experimentally and in a single clinical case in the dog (Fahie & Smith 1999). The STA is one of the terminal branches of the external carotid artery and arises rostral to the base of the auricular cartilage in the dog and cat. It supplies the skin of the temporal region and frontalis muscle, a thin muscle located superficial to the temporal muscle. A similar flap has been used in human cutaneous maxillofacial reconstruction and is known as the ‘scalping forehead’ flap (Shumrick and Smith 1992), with the base of the flap located at the level of the zygomatic arch.

VetbioSISt™ was used in this case to cover the mucosal defect and provide a scaffold for tissue remodelling and reconstruction. Porcine small intestinal submucosa (SIS) has been reported to be biocompatible and resistant to infection (Badylak et al 1989). Recent reports have evaluated the use of SIS for arterial or venous grafts, urinary bladder augmentation, perineal herniorrhaphy and repair of abdominal wall hernias (Badylaket al 1989, Kropp et al 1996, Stoll et al 2002). In contrast to other collagen implant materials that are solely resorbed and replaced by scar tissue, VetbioSISt™ becomes vascularised and replaced by functional, site-specific tissue (Badylak et al 1989). Despite the implant requiring removal 6 days postoperatively in this case, it appeared to have provided at least a temporary scaffold over which tissue generation could occur.

Primary repair of large cutaneous defects is not always feasible in the maxillofacial area owing to a lack of skin. Second intention healing may result in functional and cosmetic complications. The use of reconstructive techniques such as subdermal plexus flaps or skin grafts also have limitations in the maxillofacial region. The good cosmetic result in this clinical case indicates that the STA flap can provide a viable treatment option in managing extensive wounds of themaxillofacial region.