Introduction
The pathogenesis of obstructive sleep apnea (OSA) is complex and involves many anatomic and physiologic factors. The Fujita system for classifying the level of airway obstruction is often employed as a diagnostic tool. Level 1 indicates obstruction at the retropalatal/oropharyngeal level area. Level 2 indicates obstruction at the retropalatal/oropharyngeal and retroglossal/hypopharyngeal levels. Level 3 indicates obstruction at the retroglossal/hypopharyngeal area only. One of the major contributors to airway collapse in OSA is loss of muscular activity or tone to the pharyngeal dilators during sleep. The genioglossus muscle is one of the major pharyngeal dilators and the primary muscle allowing tongue protrusion. The muscle is attached to the genial tubercles located on the lingual aspect of the anterior mandible. Thus, its influence on obstruction at the retroglossal/hypopharyngeal level in OSA cannot be understated. For this reason, the genioglossus advancement (GA) procedure, with all of its variations and modifications, was developed.
The original GA procedure was described in a case report detailing a “high” sliding advancement genioplasty osteotomy, which was secured in place via wire osteosynthesis. A limitation of this procedure is failure to capture the entire genial tubercle complex, resulting in suboptimal airway improvement. Riley et al. then modified this procedure to incorporate the entire genioglossus muscle insertion at the genial tubercles using a mortised sliding advancement genioplasty, but the procedure led to higher risks of pathologic fracture of the mandible. Subsequent modifications to reduce fracture risk included a rectangular bicortical osteotomy of the anterior mandible around the region of the genial tubercles, with subsequent advancement and 90-degree rotation of the attachments, followed by rigid fixation. Lewis and colleagues later described a trephine osteotomy and rigid fixation system for advancing the genial tubercle/genioglossus muscles using the Stryker Leibinger genioglossus bone advancement technique (GBAT) system (Stryker Leibinger, Kalamazoo, Michigan). There have been subsequent modifications and variations to this same theme during the past two decades. With many of these procedures, a simultaneous infrahyoid myotomy and hyoid suspension were often performed (see Chapter 37 ).
Key Operative Learning Points
- 1.
Patient selection is important to optimize GA surgical results. Patients with mild-moderate OSA and collapse in the retroglossal/hypopharyngeal region may be most likely to respond.
- 2.
GA can be combined with other surgical treatments such as uvulopalatopharyngoplasty (UPPP), bilateral sagittal split advancement osteotomies of the mandible, and bimaxillary advancement osteotomies.
- 3.
Advanced imaging using cone beam computed tomography (CBCT) technology combined with computer-assisted virtual surgical planning and custom three-dimensional (3D) printed marking and positioning guides can minimize operating time and improve the precision of with which the genial tubercles are captured and advanced.
Preoperative Period
History
- 1.
OSA history
- a.
OSA diagnosis and severity
- b.
Sleep-related symptoms
- c.
Medical comorbidities (e.g., hypertension, heart disease)
- d.
Prior OSA medical therapy (e.g., continuous positive airway pressure [CPAP], bilevel positive airway pressure [BIPAP], oral appliance)
- e.
Prior OSA surgical therapy (e.g., UPPP)
- f.
Comorbid sleep medicine disorders (e.g., insomnia)
- a.
- 2.
Past medical history
- 3.
Past surgical history
- 4.
Family history
- 5.
Social history, particularly alcohol and tobacco use
- 6.
Medications, especially anticoagulants or herbal products
Physical Examination
- 1.
General —A general examination of the patient is important to assess his or her overall health and development. It is also important to consider his or her body habitus or body mass index (BMI), as patients with high weights or BMI are less likely to benefit from a GA alone.
- 2.
Head and Neck —It is important to carefully examine the patient’s head and neck to look for any signs of skeletal hypoplasia that could be contributing to the patient’s obstructive symptoms. Those individuals that could benefit most from GA often present with mandibular hypoplasia and/or microgenia. Mentalis strain and the competence of the lips are also important; often, skeletal Class II patients have lip incompetence and exhibit mentalis strain when trying to close their lips. Neck circumference and hyoid position are two other factors to consider, as larger, thicker necks are associated with higher risk of OSA, and a low-set hyoid may indicate the same.
- 3.
Nasal airway —It is important to thoroughly examine the nasal cavity for any evidence of obstruction that could be resolved via nasal surgery alone or with a combination of nasal surgery and surgery, affecting another level of obstruction.
- 4.
Oral cavity and oropharynx —This is a very important examination because it gives valuable information regarding the size of the tongue and its contributions to the patient’s obstructive symptoms, the volume of soft tissue comprising the soft palate that may be amenable to UPPP, and the size of the tonsils, which may contribute to the symptoms. It is important to note that the presence or absence of periodontal disease could increase the risk of fracture if a GA is performed. The amount and health of the keratinized tissue located buccal to the mandibular incisors are important during the postoperative course, as the incision, closure, and any subsequent scarring are located adjacent to this area, and contractures may result in unaesthetic gingival recession around the mandibular incisors.
Imaging
- 1.
Panoramic Radiograph —To visualize the periodontal tissues, dentition, height of the anterior mandible, mental foramina, inferior alveolar nerve canal, and temporomandibular joints
- 2.
Lateral Cephalometric Radiograph —Evaluate the presence and severity of maxillary, mandibular, and genial hypoplasia, all of which can contribute to various levels of obstruction in the airway during sleep.
- 3.
CBCT Scan or Maxillofacial CT Scan —Maxillofacial CT scans, and more recently CBCT scans, have been incorporated into the planning stages of various sleep surgeries, including GA. This is a proven technology that has been used for years and has been shown to have a high degree of accuracy. CBCT scans are advantageous in that they provide useful data regarding the volumetric aspects of the airway. The technology also facilitates the ability to make precise measurements to aid in planning osteotomies, avoiding critical structures such as the mental foramina, and to locate crucial aspects of the patient’s anatomy, such as the genial tubercles in this case. In addition, surgical models of the patient’s anatomy can be printed and studied along with the fabrication of surgical stents and guides to assist with various osteotomies to be certain that critical structures are included or avoided and that the specific surgical goal that was planned is accomplished. Postoperatively, the patient can be scanned again, and volumetric data can be generated about the increase in airway size and capacity.
Indications
Mild-moderate OSA with failure or inadequate adherence with medical therapy:
- 1.
Retrolingual or hypopharyngeal location of collapse
- 2.
Fujita type 2 or 3
- 3.
Microgenia or mandibular hypoplasia. GA for these patients may have both airway and aesthetic benefits.
Contraindications
- 1.
Significant medical comorbidities prohibiting operative intervention
- 2.
Severe obesity likely to decrease GA effectiveness and increase perioperative risk
- 3.
Airway obstruction localized to Fujita Level 1
- 4.
Severe OSA
- 5.
Severe periodontal disease
- 6.
Patients concerned about transient or permanent V3 paresthesia
Preoperative Preparation
- 1.
Discontinue any antiplatelet and anticoagulant medications if possible.
- 2.
Oxymetazoline nasal spray prior to the induction of nasal endotracheal anesthesia.
- 3.
Consider perioperative course of high-dose steroids to minimize postsurgical edema of the floor of the mouth, tongue, and airway.
Operative Period
Anesthesia
- 1.
General anesthesia with local anesthesia
- a.
The patient should be intubated for airway protection; ideally, the patient should have nasal intubation. In the event of a mandible fracture as a complication, the teeth would need to be wired together to set the occlusion before applying any rigid fixation plates.
- b.
Local anesthesia with epinephrine is helpful for postoperative pain management (mental blocks) but is mainly for infiltration into the anterior mandibular buccal vestibule and floor of the mouth to minimize bleeding and facilitate visualization intraoperatively.
- a.
Positioning
- 1.
Supine position with shoulder roll for partial neck extension
Perioperative Antibiotic Prophylaxis
- 1.
Ampicillin/Sulbactam (Unasyn)
- 2.
Clindamycin (Cleocin) for patients who are allergic to penicillin
Monitoring
- 1.
Routine anesthesia monitoring
Instruments and Equipment to Have Available
- 1.
#9 periosteal elevator
- 2.
Frazier tip suction
- 3.
Dingman bone clamp
- 4.
Obwegeser retractors
- 5.
Fine-tipped hemostats
- 6.
Twenty-four-gauge wire; or maxillomandibular fixation screws and 26-gauge wire
- 7.
Wire drivers
- 8.
Wire cutters
- 9.
Scalpel with #15 blade
- 10.
Electrocautery with Colorado microdissection tip
- 11.
Symphyseal retractor
- 12.
Sagittal safe oscillating saw blade
- 13.
Long reciprocating saw blade
- 14.
Maxillofacial plating set with bicortical screws, fixation plates, and/or pre-bent genioplasty advancement plates
- 15.
Compressive facial support dressing
- 16.
Computer-assisted marking and positioning guides (if surgery virtually planned and designed)
Key Anatomic Landmarks
- 1.
Mandibular buccal vestibule—For most solitary GA procedures, a standard intraoral approach is used via the anterior buccal vestibule, which has the advantage of a hidden, intraoral scar. The mandibular buccal vestibule is located between the mandibular incisors and the lower lip. It contains nonkeratinized stratified squamous mucosa.
- 2.
Mentalis muscle—Located beneath the anterior buccal vestibular tissue of the mandible, it is the only elevator of the lower lip and chin. If this muscle is not repositioned properly during the closure, the chin will “droop,” leading to a “witch’s chin”–type deformity along with the sagging appearing of the lower lip, exposing more lower incisor. The mentalis originates from the mental prominence of the mandible and inserts into the soft tissues of the chin prominence. The most superior fibers are the shortest and pass almost horizontally into the chin, while the most inferior fibers are the longest and pass obliquely or vertically to the skin at the lower aspect of the chin. The origin of the mentalis muscle determines the depth of the labial vestibule. The mentalis muscle is innervated by the marginal mandibular branch of the seventh cranial nerve (facial nerve).
- 3.
Mental neurovascular bundle—The major neurovascular structure that must be avoided during a GA procedure. The artery and vein that accompany the nerve are insignificant from a surgical standpoint. However, the mental nerve is a terminal branch of the mandibular division (V3) of the fifth cranial nerve (trigeminal nerve), and its function is to innervate the skin and mucosa of the lower lip, the facial gingiva of the mandibular incisors, and the skin of the chin. The mental nerve exits the mental foramen located near the apex of the first or second mandibular premolar teeth and usually then splits into three smaller branches that fan out into the region of innervation. The branching pattern can be variable, and some branches can be superficial within the oral mucosa.
- 4.
Genioglossus muscles/genial tubercles—The genioglossus muscles are one set of extrinsic muscles of the tongue. As such, they originate from the genial tubercles located on the lingual aspect of the mandible and then fan out vertically and horizontally within the body of the tongue. They are the main protrusors of the tongue. The muscles are innervated by the 12th cranial nerve (hypoglossal nerve). They receive their major blood supply from the lingual arteries bilaterally. Silverstein et al., in their classic cadaveric study from 2000, detailed many relevant measurements regarding the nature of the genial tubercles and surrounding anatomy. They showed that the average thickness of the mandible at the genial tubercle was approximately 13 mm at the midline inferior border 14.5 mm. In addition, the average distance from the genial tubercles to the inferior border at midline was 14.5 mm, and the average distance from the apex of the mandibular incisor teeth to the genial tubercle was 11.8 mm. The width of the genioglossus muscle attachments themselves was approximately 14 mm.
- 5.
Digastric muscles—The anterior digastrics are attached to the inferior border of the anterior mandible and the hyoid posteriorly. When advancing the inferior border segment during a GA, these muscles are placed under tension along with the genioglossus, which helps to pull the hyoid anteriorly and superiorly and helps to further open the airway.
Prerequisite Skills
- 1.
Basic mandibular osteotomy skills
- 2.
Familiarity with anatomy of the mandible and the floor of the mouth
- 3.
Experience with internal rigid fixation
Operative Risks
- 1.
Hemorrhage from the floor of mouth from the genioglossus muscles, the mylohyoid muscles, or the lingual or sublingual arteries. This often occurs when patients have remained on antiplatelet or anticoagulant medications or when the reciprocating saw tip is placed too deep into the floor of mouth.
- 2.
Fracture of the mandible—If the inferior border osteotomy is placed too superior, leaving minimal to no mandibular basal bone and only mandibular alveolar bone to provide continuity
- 3.
Damage to the mental nerves—Damage to the nerves can occur during the dissection of the mandible or during the osteotomy.
- 4.
Avulsion of the genioglossus muscles from the genial tubercles—If the osteotomized segment containing the genial tubercles is placed under significant tension, the muscles can avulse from the tubercles.
- 5.
Perforation of the lower lip or labiomental groove—This complication can occur if the surgeon is not careful during the intraoral dissection that is done to access the mandible.
- 6.
Damage to the mandibular dentition—Damage to the teeth can occur during the osteotomy if the osteotomy is made too superior. The apices of the teeth can be cut off the roots, endangering the vitality of the teeth.
Surgical Technique
- 1.
The patient is positioned, padded, prepped, and draped.
- 2.
The anterior mandibular buccal vestibule is injected with 1% lidocaine with 1:100,000 epinephrine, with additional local anesthetic being injected into the anterior floor of the mouth to assist with hemostasis.
- 3.
A moist throat pack is placed in the posterior oropharynx.
- 4.
The jaws can then be wired shut with 26-gauge wire and temporary bone screws to provide stability to the mandible while performing the osteotomy.
- a.
You may elect to use surgical marking and positioning guides, which are wired temporarily between the teeth once the dissection is complete. These guides were also screwed into the mandibular bone ( Fig. 58.1 ). The guides, which had been printed with 3D printing technology, were based off of the data from the patient’s preoperative CBCT scan and virtual surgical planning session. Their purpose was to allow us to include the genial tubercles with the osteotomized segment with a high degree of accuracy and then to advance the segment the intended, maximal amount ( Figs. 58.2 and 58.3 ).
- a.
