Bart C. Farrell, Brian B. Farrell, and Myron R. Tucker
Private Practice, Carolinas Center for Oral and Facial Surgery, Charlotte, North Carolina, USA; and Department of Oral and Maxillofacial Surgery, Louisiana State University Health Science Center, New Orleans, Louisiana, USA
A means of augmentation or reduction of the anterior mandible.
- Correction of skeletal deformities, including mild retrognathia, macrogenia, microgenia, and genial asymmetry
- Enlargement of the posterior airway space for treatment of obstructive sleep apnea
- Retrognathia with normal genial development
- Difficult or distorted anatomy
- Short mandibular symphysis
- Neurosensory concerns
- Mental nerve and foramen: The genu of the mental nerve may course anteriorly 1-5 mm before exiting the mental foramen at the apices of the premolar teeth.
- Mentalis muscle: A midline muscular band that originates from the incisive fossa of the mandible and inserts along the skin of the lower lip. Functions to protrude the lower lip.
- Genioglossus muscle: A paired extrinsic tongue muscle that originates from the superior genial tubercle and inserts into the body of the tongue. Functions to protract and depress the tongue.
- The patient is prepped and draped to include the oral cavity and maxillofacial region. The patient is nasally intubated, and the tube is secured. A throat pack is positioned at the level of the hypopharynx.
- Local anesthetic containing a vasoconstrictor is injected within the anterior mandibular vestibule from mental foramen to mental foramen with direct injection within the mentalis muscles.
- An incision is created within the anterior mandibular vestibule, 1 cm anterior to the depth of the vestibule (Figure 23.1, Case Report 23.1). An anteriorly placed incision will conserve both attached and unattached tissue for closure. An incision placed too close to the attached tissue will cause recession due to scar contracture and could compromise the incisor teeth. Once through the mucosa, the small branches of the mental nerve coursing superficially into the lower lip are identified and reflected laterally from the surgical field. The dissection is carried sharply through the mentalis muscle with a heavy scissor (Metzenbaum). Caution should be taken to minimize dissection toward the skin to avoid iatrogenic perforation of the lower lip.
- The symphysis is exposed anteriorly in a subperiosteal manner to the inferior border (Figure 23.2, Case Report 23.1). Minimal dissection is required superiorly to avoid unnecessary striping of the attached tissue over the mandibular incisor teeth and preserve the superior portion of the mentalis muscle for closure.
- The dissection is carried posteriorly to locate the mental foramen (Figure 23.3, Case Report 23.1). Subperiosteal dissection is carried inferior and posterior to the mental foramen to expose the inferior border of the body of the mandible.
A sagittal saw is used to score a vertical line marking the skeletal midline to serve as a reference during manipulation of the anterior segment (Figure 23.4, Case Report 23.1, and Figure 23.10, Case Report 23.2). The planned osteotomy should be placed at least 5 mm inferiorly to the visualized mental foramen and apices of the anterior teeth. The horizontal osteotomy should extend as far posteriorly as possible within the body of the mandible without encroaching on the mandibular canal.
- A reciprocating saw is used to score the facial cortex for the planned osteotomy bilaterally (Figure 23.10, Case Report 23.2).
- Once satisfied with the osteotomy design, the saw is held upright while cutting through both the facial and lingual cortices from the inferior border to the midline. The osteotomy is then duplicated on the contralateral side. Once the osteotomy is complete, the inferior border is downfractured and mobilized.
- The free segment can be stabilized with a towel clamp or wire. A wire-passing bur may be used to create an opening through the facial cortex for a 26-gauge wire. The wire or towel clamp can be used to control the free segment in preparation for fixation (Figure 23.4, Case Report 23.1).
The segment is repositioned according to the treatment plan and inspected to ensure appropriate positioning and symmetry. Calipers can be used to determine the extent of skeletal change to aid in transferring the presurgical plan to the surgery. Jigs may be fabricated from virtual planning when the chin possesses a pronounced deformity (asymmetry) to aid in the establishment of skeletal symmetry and projection (