Axial Pattern Flaps for Maxillofacial Reconstruction
Mark Smith United States
Head and neck squamous cell carcinoma (SCC) is the fourth most common neoplasm in felines. The oral cavity, aural pinna, and nares are commonly affected locations. Feline SCC is biologically similar to human head and neck SCC: both are locally invasive, and metastases to regional lymph nodes and lungs occur late in the course of disease. As in human medicine, treatment of disease limited to small primary SCC (Stage I or II) is surgery or radiotherapy. Unfortunately, felines with SCC are often presented by their owner for advanced, large primary tumors (Stage III or IV), which are not amenable to local resective surgery or radiotherapy as single modalities for treatment. In veterinary medicine, the type of surgical treatment is based on neoplasm location, surgeon's skill, and owner preference. Owners of affected felines may not desire or comply with adjunctive therapy recommendations, often making surgical cure the operative goal for Stage III and IV SCC. Fulfillment of this goal requires aggressive en bloc resection to optimize tumor-free margins.
The concept of complete local excision of all visible tumor followed by, or concurrent with, chemotherapy or radiation therapy for treatment of presumed micrometastasis has achieved marked acceptance in human oncologic therapy and is being applied in veterinary medicine. This multimodality treatment plan includes surgery as an integral component especially for large, aggressive neoplasms. The goal of the operative plan for neoplasms of the head and neck in cats and dogs is most commonly curative resection or palliation. A surgical procedure that offers the greatest possibility of cure, restores or maintains function, and has an acceptable cosmetic result is often required in veterinary medicine. Regional axial pattern flaps may serve as a compromise between local and free flaps by providing durable tumor-free tissue for wound reconstruction. The availability of cervical and frontal cutaneous flaps with direct cutaneous blood supply for head and neck reconstruction may allow radical resective surgery avoiding functional disturbances while providing a cosmetic result.
CAUDAL AURICULAR (LATERAL NECK) FLAP
The lateral neck flap has been shown to be a useful reconstructive surgical technique following resection of head and neck neoplasms in humans. The skin-muscle composite has versatility for multiple head and neck lesions allowing generous margins, less tissue bulk compared with other regional flaps, adaptable length, and vascular reliability. The feline and canine platysma muscle is intimately associated with subcutaneous tissues. Cutaneous vascular supply from multiple vessels, including cutaneous branches of the caudal auricular artery and vein are observed coursing in the lateral cervical region of the platysma muscle. As in humans, the observed vascular supply to the feline and canine lateral neck flap is consistent in location and emphasizes a cranial basis and horizontal orientation. The flap is versatile based on surgical studies in which intraoperative manipulation was performed prior to orthotopic replacement and clinical application in two feline patients. There seems to be no deleterious results related to flap thinness or gravitational effects based on application in clinical patients.
Results of cadaver and vascular studies in the feline and canine show one cutaneous branch of the caudal auricular artery and vein contributing blood supply to the cranial aspect of the cervical skin and platysma muscle while angiography reveals dorsal and caudal vessel orientation which parallels the central cervical region. The cutaneous branch of the caudal auricular artery observed during surgery is intimately associated with the platysma muscle and divides near its origin located in the area between the lateral aspect of the wing of the atlas and the vertical ear canal. Guidelines for flap location have been based on results of cadaver and vascular studies. The flap is centered over the lateral aspect of the wing of the atlas. The flap is positioned in the center of the neck within ventral and dorsal lines paralleling the measured flap base and the same width measurement centered on the spine of the scapula. Flap length may vary and does not necessarily extend to the spine of the scapula. The platysma muscle is intimately associated with the subcutis of the flap.
In surgical studies, the mean survival length in cats (7.7 + 2.2 cm) and dogs (15.4 + 2.1 cm) of flaps incorporating vascular supply from the caudal auricular artery and vein, indicates that the lateral neck flap may be most useful for caudal head and neck defects compared with more rostral defects, which occur following resection of neoplasms affecting the nares, premaxilla, or mandibular symphysis.
The reconstructive surgical technique described here may allow elective neck dissection with preservation of the caudal auricular artery depending on the size of the operative field. This approach provides access for excisional biopsy of mandibular and/or cervical lymph nodes to aid staging and augment surgical extirpation of metastatic disease. Metastatic routes that may be considered during dissection include perineural, vascular and microvascular, lymphatic, and transcapsular. Extended dissection from the primary site may improve the incidence of free margins related to surgical resection of direct metastatic pathways. This may be of particular importance for neoplasms of the floor of the mouth and caudal head and neck region. The cranial cervical area was easily observed in conjunction with lateral neck flap elevation in surgical studies and clinical patients. Direct observation of regional lymph nodes allows assessment of gross transcapsular spread of the tumor that may warrant wider margins for adhered lymph nodes.
SUPERFICIAL TEMPORAL (FOREHEAD) FLAP
Skin of the canine and feline maxillofacial region is relatively immobile, making cutaneous wounds often not amenable to primary repair or second-intention wound management without resultant functional and cosmetic deficiencies. Human patients with maxillofacial defects have been surgically managed successfully using “forehead flaps” since as early as 700 B.C. The scalping “forehead flap” with the flap base at the level of the zygomatic arch is similar to the flap described here.
Guidelines for flap location were based on results of cadaver and vascular studies performed in dogs and cats. The landmarks for the base of the forehead flap were the caudal aspect of the zygomatic arch caudally and the lateral orbital rim rostrally. Flap dimensions were based on the feasibility of primary wound closure of the donor site and required length to transfer the flap to the maxillofacial area, including the nasal planum as the rostral extent. The width of the flap was equivalent to the width of the zygomatic arch. Based on the necrosis of the distal tip of the extended 4:1 length:width ratio flaps, we recommend use of a 3:1 length:width ratio forehead flap which provides adequate tissue for rostral rotation to the nasal planum. Based on the results of our research, the forehead flap based on the superficial temporal artery had a greater surviving length compared with flaps dependent solely on the subdermal plexus. The forehead flap may have application for maxillofacial reconstruction of traumatic wounds, or wounds resulting after excisional surgery or radiation therapy.
Surgery was done on a one-year-old Border Terrier for reconstruction of a traumatic maxillofacial defect. A premaxillectomy was performed, removing the incisors but maintaining the palatal incisive papilla, to provide a mucosal surface for reconstruction of the nares. A 4.0 x 12.0 cm (3:1 length:width ratio) forehead flap based on the left superficial temporal artery and vein was created. A bridge incision was made beginning in the frontal region and bisecting the nasal region. The flap was rotated rostrally, and the distal tip was sutured to the palatal mucosa in the region of the nares. Primary closure of the donor site and the periphery of the flap were performed using a simple continuous suture pattern.
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