1 INTRODUCTION

Hypopharyngeal obstruction is a major contributing factor in obstructive sleep apnea (OSA). Hypopharyngeal obstruction stems from the prominence or relaxation of the base of the tongue, lateral pharyngeal wall collapse, and occasionally involves the aryepiglottic folds or epiglottis.^1–3 Because the genioglossus muscle is a major pharyngeal dilator, it has long been suggested to play a major role in nocturnal airway obstruction.^4,5 Genioglossus advancement is a surgical procedure designed to place the genioglossus muscle under tension, thus restricting the collapse of the tongue into the airway during sleep-induced hypotonia. Multiple studies have demonstrated that genioglossus advancement combined with uvulopalatopharyngoplasty achieves improvement of OSA.^6–8 Several designs of the osteotomy during genioglossus advancement have been described, with each one aimed at minimizing the surgical morbidity while improving the incorporation and the advancement of the genioglossus muscle.^6,9–11

2 PRESURGICAL EVALUATION

The presence of hypopharyngeal obstruction is confirmed by physical examination as well as utilizing fiberoptic evaluation and lateral cephalometric radiograph. The operation is designed to reposition the genial tubercleforward, thus improving the tension of the tongue musculature and limiting its posterior displacement during sleep. Preoperative radiograph such as a panoramic dental x-ray is also necessary to assist the surgeon in the evaluation of the genial tubercle position and tooth root posi-tion. The panoramic radiograph will demonstrate the course of the inferior alveolar nerve canal, the mental foramen, the position of the mandibular tooth roots, as well as the detection of potential pathologic processes of the mandible.

3 SURGICAL TECHNIQUE

The procedure is performed under general anesthesia with oroendotracheal intubation. Local anesthetic injection (10 milliliters of 2% lidocaine with epinephrine) is administered at the anterior mandibular vestibule. The procedure begins with a mucosal incision approximately 10 mm below the mucogingival junction (Fig. 48.1). A subperiosteal dissection is performed to expose the mandibular symphysis. Exposure and identification of the mental nerves are unnecessary as the mental foramen is lateral to the surgical site. The genial tubercle and genioglossus muscle can be estimated by finger palpation in the floor of the mouth and with the aid of the lateral cephalometric and panoramic radiographs. A rectangular osteotomy encompassing the estimated location of the genial tubercle is performed under copious irrigation (Fig. 48.2). It is recommended that the superior horizontal bone cut be at least 5 mm below the mandibular root apices to decrease the likelihood of tooth paresthesia. The inferior horizontal bone cut should be designed to preserve approximately 10 mm of the inferior border of the mandible to reduce the risk of a pathologic mandibular fracture. If there is insufficient mandibular symphyseal height, this procedure should not be performed as the risk of pathologic mandibular fracture or tooth root injury is increased. Due to the elongated canine tooth roots that are often present, the vertical bone cuts are made just medial to the canine tooth to avoid root injury. It is crucial to follow parallelism of the osteotomies to facilitate the ease of releasing the rectangular bone flap. Prior to completing the osteotomy, a titanium screw is placed in the outer cortex to control and manipulate the bone flap. At the completion of the osteotomy, the bone flap is released from the surrounding bone and is advanced and rotated 60° to prevent retraction back into the floor of the mouth. The outer cortex and marrow are removed and the inner cortex is rigidly fixed with a lag screw (Fig. 48.3).

Fig. 48.1 Mucosal incision made approximately 10 mm below the mucogingival junction.

Fig. 48.2 A rectangular osteotomy encompassing the estimated location of the genial tubercle is performed.

Fig. 48.3 The bone flap is advanced and rotated 60° to prevent retraction back into the floor of the mouth. The outer cortex and marrow are removed and the inner cortex is rigidly fixed with a lag screw.

Bleeding is controlled with electrocautery and a hemostatic agent such as Gelfoam® (Pharmacia and Upjohn Company, Kalamazoo, Michigan 49001). Bone wax is not recommended for control of bleeding due to extrusion problems. It is important to irrigate the wound with copious irrigation to eliminate bone dusts. The procedure is completed with layer closure of the wound with re-establishment of the mentalis muscle and mucosa layers. This layered closure is crucial to minimize wound dehiscence.

3 PERIOPERATIVE MANAGEMENT

Patients with OSA have an increased risk for postoperative airway compromise. All patients should be extubated awake in the operating room immediately following surgery. ICU monitoring should be considered in patients undergoing multiple procedures (uvulopalatopharyngoplasty combining with genioglossus advancement and/or hyoid myotomy and suspension), or in patients with significant co-existing medical problems such as hypertension and coronary artery disease. Nasal CPAP or humidified oxygen via face tent should be considered in all patients, and oximetry monitoring is performed throughout the hospitalization. Blood pressure should be monitored closely and hypertension treated aggressively with intravenous antihypertensive medications to minimize postoperative bleeding and edema.

4 DISCUSSION

It is well recognized that the hypopharyngeal airway often needs to be addressed in order to maximize the surgical response in sleep apnea treatment. Genioglossus advancement has been utilized in the management of hypopharyngeal obstruction since the 1980s.¹² Regardless of the osteotomy design, the principle of the procedure is the same, i.e. advancing of the genioglossus muscle and limiting the tongue base collapse. It should be pointed out that there are advantages and disadvantages with different designs. The rectangular osteotomy described in this article is less invasive when compared to the mortise osteotomy which includes the lower border. It also minimizes the risk of mandibular fracture since the lower border of the mandible is preserved. The genioglossus muscle is routinely captured in the advancement. However, the rectangular design is more technically challenging. Although the mortise design captures more muscle in the advancement, the advancement is usually less. Regardless of the osteotomy design, potential complications of genioglossus advancement include bleeding, infection, paresthesia, anesthesia or dysthesia of the chin and teeth as well as mandibular fracture.

Although most studies have shown that combining uvulopalatopharyngoplasty and genioglossus advancement achieves improvement of OSA, the success rate can be quite variable, ranging from 22% to 67%.^6–13 This is likely due to the complexity associated with the etiology of OSA, patient selection and surgical execution.