20.1 Introduction

Reconstruction of the buccal region following resection of an oral malignancy constitutes a challenging problem from both a functional and an aesthetic standpoint. Functionally, the buccal region plays a crucial role in oral phase swallowing, speech, mastication, and facial movement. Facial expression, along with the contour of the face and appearance of the oral commissure, can also introduce aesthetic complexities in reconstruction. Successful reconstruction of the buccal region is aimed at restoring a barrier that encloses the oral cavity while supporting the functional and aesthetic components listed above.

20.2 Anatomy

The buccal region is roughly defined anteriorly by the oral commissure, posteriorly by the ramus of the mandible, superiorly by the zygomatic process of the maxilla, inferiorly by the inferior border of the mandible, medially by the maxillary and mandibular alveolus, and laterally by the skin of the cheek. The key anatomic components are comprised of skin, oral mucosa, buccal fat pad (BFP), facial and buccal vessels, parotid duct, as well as the facial nerve and associated musculature. Each of these elements must be considered in characterizing a defect and planning for an appropriate reconstruction

The muscles of facial expression in the buccal region include the orbicularis oris, risorius, zygomaticus major and minor, buccinator, and depressor anguli oris. These muscles are all enveloped by the superficial muscular aponeurotic system (SMAS) and are innervated by the buccal branches of the facial nerve, with contributions from the zygomatic and marginal mandibular branches. The facial nerve branches travel just deep to the SMAS and innervate the muscles of facial expression, with the exception of the buccinator, from their deep surface.

The arterial supply of the buccal regions is derived from the buccal branch of the internal maxillary artery as well as the facial artery. Venous drainage is comprised of the pterygoid plexus and facial vein. Sensory innervation is supplied by branches of the maxillary and mandibular branches of the trigeminal nerve.

The parotid duct exits from the anterior aspect of the parotid gland and courses superficial to the masseter muscle. At the anterior border of the masseter, it turns medially and pierces the BFP, buccinator fascia, and buccinator muscle before exiting into the oral cavity via a papilla opposite the second maxillary molar.

20.3 Functional Considerations

The various components of the buccal region play a major role in the functions of mouth opening, chewing, swallowing, speech, as well as facial movement, all of which may be impacted by tumor resection. In simple terms, the buccal mucosa serves as a passive barrier that helps enclose the oral cavity and, in conjunction with the action of the lips, prevents leakage of saliva and other oral contents. The ability to seal the oral cavity is also necessary to generate a positive air pressure gradient for plosive speech and a negative pressure gradient for sucking. The muscles of facial expression, in addition to accomplishing their namesake, are involved in the transit of food during mastication and deglutition. Facial reanimation, as it pertains to the buccal region, is therefore an important consideration for reconstruction of buccal defects that involve the facial musculature and nerve branches. Specific techniques for facial reanimation, however, are beyond the scope of this chapter.

One of the most common functional consequences of surgical resection and reconstruction for buccal cancer is the development of trismus, defined as a mouth opening limited to 35 mm or less. ¹ The reported incidence of trismus following treatment of oral cancer varies, but may be seen in as many as 86% of patients following radiation therapy or surgery. ^{2 , 3} Reduced mouth opening may result from scarring of the muscles of mastication and buccal soft tissue, and/or tissue loss following radiation therapy or surgery. In addition, native buccal mucosa has a high degree of inherent elasticity that is difficult to replicate through any form of tissue transfer. By itself, trismus may contribute to difficulty with oral intake, chewing, swallowing, speaking, as well as dental issues from poor oral hygiene. ³ Therefore, reducing the risk of trismus should be one of the primary considerations when choosing a reconstructive technique.

20.4 Options for Reconstruction

The choice for an optimal reconstructive plan is largely dictated by size and location of the primary defect. Squaquara et al classify the size of intraoral defects into small (= 4 cm diameter), medium (= 7 cm diameter), and large (> 7 cm diameter). ⁴ When measuring the size of the defect, the superior to inferior dimension will generally be the most important in determining mouth opening. ⁵ Small defects may be closed primarily or, for superficial defects, either left to heal by secondary intention or repaired with a split-thickness skin graft. However, with increasing defect diameter and soft-tissue involvement, the risk of trismus increases. ⁴ Numerous options for reconstruction using local and regional flaps have been reported in the literature. For large and complex defects, free tissue transfer remains the most versatile option for reconstruction, although it is not without its drawbacks. ^{6 , 7}

20.4.1 Local Flaps

A simple mucosal advancement flap may be sufficient to repair smaller buccal defects. The use of a posteriorly based buccinator musculomucosal flap has also been reported. ⁸ These flaps have the advantage of utilizing native buccal tissue, as well as potentially preserving sensation to the buccal surface. Excessive harvesting of buccal mucosa, however, may result in trismus as well as damage to the parotid duct. ⁵

For slightly larger defects, the BFP can be harvested and used as a pedicled flap (▶ Fig. 19.4). The BFP is found in the masticator space in between the buccinator and masseter muscles, and has a relatively rich blood supply consisting of branches of the internal maxillary artery, transverse facial branch of the superficial temporal artery, and facial artery. Mucosalization of the BFP typically takes place over several weeks, and so an additional skin graft is usually not necessary. Buccal fat has the advantage of being easily harvested. However, it provides minimal bulk and can retract substantially, making it unsuitable for medium or large defects. ^{9 , 10}

The facial artery musculomucosal (FAMM) is robust pedicled flap with an axial blood supply based off of the facial artery (▶ Fig. 20.1). It is designed just anterior to the parotid duct and consists of mucosa, submucosa, part of the buccinator muscle, the facial artery, and a rich submucous venous plexus. The FAMM flap may be inferiorly (anterograde flow) or superiorly (retrograde flow) based, depending on the location of the defect. ¹¹

Various tongue flap designs, including the double-door and lateral tongue flap, have also been described for the closure of buccal defects (▶ Fig. 20.2). These flaps are generally versatile and reliable, but require a second-stage surgery, as the flap pedicle tethers the tongue and must be divided after the initial inset. During the postoperative period, trauma to the pedicle can occur from the teeth, as well as excessive movement of the tongue. Dysarthria is also a potential sequela, although this can usually be avoided if the mobility of the tongue tip is maintained. ^{12 – 14}

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