Mandibular Osteotomy with Genioglossus Advancement

Genioglossus advancement is indicated for patients with documented hypopha-ryngeal obstruction (Table 6) (Fujita Type II—Ill). The rationale of this surgery is to enlarge the posterior airway space by preventing prolapse of the tongue during sleep. Considered part of phase I of the Powell-Riley protocol, it may be used alone or in combination with other procedures depending upon the regions of obstruction.

This surgery is a conservative maxillofacial technique, since an osteotomy is created in the mandible without changing the dental occlusion. Thus, a limitation of this surgery is that no additional room is created for the tongue, in contrast to maxil-lomandibular advancement. Essentially, the genial tubercle and the attached genio-glossus muscle are advanced anteriorly. The degree of advancement is dependent upon the thickness of the anterior portion of the mandible and the compliance of the genioglossus muscle. Less muscle compliance will provide a greater degree of tension. Unfortunately, there is no study to determine the compliance of the genio-glossus muscle preoperatively.

Surgery can be performed under intravenous sedation or general anesthesia. Blood loss is usually negligible. A lateral cephalometric radiograph and a panoramic dental radiograph are critical in the preoperative planning. The panoramic radiograph allows the surgeon to identify the genial tubercle and to assess the root length of the mandibular canine and central incisor teeth. Sclerotic bone in the symphyseal region of the mandible aids in locating the genial tubercle. Furthermore, the film should be reviewed for evidence of periodontal disease.

Knowledge of the anatomy is vital to capture the majority of the genioglossus muscle fibers within the rectangular osteotomy and to avoid complications. As the muscle's insertion includes the genial tubercle and the lingual surface of the mandible adjacent to the tubercle, the osteotomy must be designed to encompass this region. Thus, the width of the bone fragment should be at least 14 mm and the height about 10 mm (60,61). To avoid injury to the roots of the canine teeth, the vertical osteotomies should be medial to the canine dentition. Careful planning is also required in performing the horizontal osteotomies. The surgeon must be cognizant of the roots of the incisor dentition and the inferior border of the mandible. It is recommended that the superior osteotomy be placed at least 5 mm inferior to the root apices to avoid injury (62). In addition, the inferior osteotomy should be approximately 10 mm above the inferior border of the mandible to prevent a potential fracture.

In 1986, Riley et al. (63) developed the rectangular osteotomy technique (Fig. 5) to advance the genial tubercle for patients with hypopharyngeal obstruction. This procedure is within the rubric of phase I surgery. Subsequently, they evaluated 239 patients who completed phase I surgery and underwent postoperative PSG. Most of these patients had genioglossus advancement with hyoid suspension and UPPP. The overall success rate was 61%. The data were further extrapolated to determine the correlation between disease severity and response rates. Patients with mild disease had a cure rate of 77%, while those with severe disease had a cure rate of 42% (38). Similar results were reported in other studies (43-45,64). In Sher's (46) meta-analysis of patients who only underwent UPPP, the overall responder rate

FIGURE 5 (See color insert.) Mandibular osteotomy with genioglossus advancement. A rectangular osteotomy is created in the anterior mandible. The genial tubercle and the attached genioglossus muscle are advanced anteriorly. The bony fragment is rotated 90° to overlap the inferior border of the mandible and secured to the mandible with a titanium screw. Source: From Ref. 121.

was 39%. Thus, it became evident that the addition of genioglossus advancement can substantially increase success rates for treating SDB.

Postoperative edema or hematoma is usually self-limiting. Obstruction of the airway due to edema or hematoma is the most distressing complication following surgery but it has not been observed in our series. The use of CPAP in the early postoperative period reduces edema and maintains the patency of the airway (65,66). Meticulous hemostasis and aggressive antihypertensive management are critical to prevent hematoma formation. As previously mentioned, inferior border mandible fractures can occur if the osteotomy is incorrectly designed. This complication has been essentially eliminated by performing a rectangular osteotomy, which leaves the inferior border of the mandible intact. Any technique which violates the inferior border increases the risk of a pathologic fracture. Minor complications, such as wound infection, transient anesthesia of the teeth or lower lip, and root injury requiring endodontic therapy have an incidence rate of 2%, 6%, and 1%, respectively, at our center.

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