Lateral Mandible Reconstruction With Soft Tissue Flaps

Afshin Mosahebi

Evan Matros

Babak J. Mehrara

DEFINITION

The mandible provides contour to the posterior lower third of the face and plays a key role in mastication and maintenance of oral competence.
- As a result, mandibular function is necessary for swallowing, speech, and aesthetic contour of the face.
The most common indication for mandibular reconstruction is segmental bone loss resulting from cancer ablation, trauma, osteoradionecrosis, and infection.
Defects of the lateral mandible are defined as those that extend posteriorly from the mental foramen and can include the ramus or condyle.
Lateral mandibular defects that are most suitable for soft tissue-only reconstruction defects include not only osseous defects but also extensive soft tissue injury including the floor of the mouth, tongue, palate, pharynx, and external skin. Mandibular defects that result in the complete loss of the temporomandibular joint and the surrounding soft tissues may also benefit from soft tissue-only reconstruction because insetting of bone flaps in these defects may be difficult and associated with poor function.

ANATOMY

The mandible is anatomically divided into one horizontal component and two vertical components.
- The horizontal component comprises the symphysis and the body on each side, forming a U-shaped arch that connects the two vertical segments.
- Each vertical segment is composed of the angle, ramus, coronoid process and condylar process. The vertical segment serves as the insertion site for the muscles of mastication and forms the articulation of the mandible with the skull.
The arterial supply of the mandible is derived from branches of the lingual, facial, and inferior alveolar arteries.
The inferior alveolar nerve is the largest branch of the mandibular nerve. It enters the mandible through the mandibular foramen on the medial surface of the mandibular ramus and gives two terminal branches: the mental nerve and the incisive nerve.
- The mental nerve innervates the skin of the chin as well as the skin and the mucosa of the lower lip.
- The incisive nerve continues to travel in the mandible and provides sensory innervation to the premolar, canine, incisor teeth, and their associated gingiva.

PATIENT HISTORY AND PHYSICAL FINDINGS

Patient history should include careful assessment of the pathology of the anticipated mandibular defect and the previous treatments that have been administered.
- History of prior surgery, particularly those that may involve the vascular supply of the mandible, should be obtained. This information is important in surgical planning because damage to the ipsilateral neck vessels may require the use of contralateral neck vessels or alternative plans.
- Surgical plans should be reviewed with the head and neck surgeons (if they are involved in the procedure).
History of radiation to the area should also be obtained because this treatment may impede healing of soft and bony tissues, decrease availability of recipient vessels, and increase the potential need for external skin coverage.
Past medical history, medical comorbidities, and risk factors for cardiovascular disease (eg, hypertension, coronary artery disease, hyperlipidemia, history of smoking, obesity, diabetes, etc.) should be reviewed.
- This is common in patients with head and neck cancers because many of these individuals have a history of smoking and ethanol use.
- Patients with long-standing history of cardiovascular disease require medical consultation for preoperative clearance and optimization.
Preoperative speech and swallowing should be documented and assessed because these functions may be significantly affected by tumor invasion and surgical ablation. In addition, preoperative mouth opening should be recorded as interincisal distance.
Oral hygiene and dentition should be assessed because patients with poor oral hygiene and dentition are at much higher risk of postoperative infections and complications. Severe compromise of dentition or oral hygiene may also require preoperative dental consultation.
The presence or absence of pain with mouth opening, chewing, swallowing, or eating should be obtained.
The patient’s general nutritional status should be assessed by physical examination and laboratory tests.
Personal and family history of bleeding abnormalities should be elicited.
The physical examination should also include assessment of the head and neck area, anticipate the planned resection in the case of oncologic patients, assess availability of recipient
vessels, quality of intraoral and extraoral soft tissues, and available donor sites for reconstruction.
- A pulse examination of the extremities is necessary to document the potential for peripheral vascular disease.
- The quality (ie, thickness, pliability, etc.) of soft tissue donor sites should be addressed, and alternative plans should be developed.

IMAGING

Preoperative computed tomography (CT) or magnetic resonance imaging (MRI) may be helpful in assessing osseous defects and potential involvement of the soft tissues.
Preoperative angiography may also be helpful in assessing availability of recipient vessels in the head and neck area, although this is rarely necessary.
Preoperative imaging of donor sites may also be useful for assessment of blood flow. However, this is rarely necessary for assessment of soft tissue flaps such as the anterolateral thigh or rectus abdominis flaps commonly used in soft tissue only reconstruction of complex lateral mandible defects.

SURGICAL MANAGEMENT

Lateral mandible defects that involve primarily the bone with limited resection of the soft tissues are best reconstructed with bone flaps (eg, fibula, scapula, iliac crest).
Soft tissue reconstruction of lateral mandible defects is indicated in patients with an intact anterior mandibular arch (ie, bone resection is lateral to the incisors) in combination with complex soft tissue defects involving the floor of the mouth, tongue, palate, pharynx, or, in some cases, external skin.
- It is useful in cases in which the temporomandibular joint is widely excised, leaving a large defect at the base of the skull where bone flaps cannot be adequately seated.
- It may be needed in patients who do not have osseous donor-site options (eg, severe peripheral vascular disease). However, this is less common because multiple options for bone donor sites exist (eg, scapula may be a good choice in these cases).
Of the variety of soft tissue flaps useful for reconstruction of complex lateral mandibular defects, the vertical rectus abdominis myocutaneous flap and the anterolateral (ALT) flap are most commonly used for the following reasons:
- They provide large amounts of soft tissues and muscle that can be tailored to complex defects.
- They enable harvesting of multiple skin paddles that can facilitate combined intraoral and extraoral defect reconstruction.
- They have long pedicles that can easily reach neck recipient vessels even if it is necessary to use vessels contralateral to the site of the defect.