Surgical Proceduresphase Ii Maxillomandibular Advancement Osteotomy

MMO, also referred to as bimaxillary surgery, is considered phase II of the Powell-Riley two-phase surgical protocol. The rationale for MMO is to ameliorate refractory hypopharyngeal obstruction by advancing the mandible and maxilla forward.

Treatment of SDB by skeletal surgery was first described by Kuo et al. (72) and Bear and Priest (73). Subjective improvements in SDB were reported, but there was no postoperative PSG to support these claims. Subsequently, our group objectively documented an improvement in sleep apnea following mandibular advancement (74). Numerous studies have since reiterated these findings (49,75,76).

MMO enlarges both the hypopharyngeal and pharyngeal airway by expanding the skeletal facial framework. It is the only surgery in our protocol, which physically creates more space for the tongue in the oral cavity. In addition, it exerts further tension on the velopharyngeal and suprahyoid musculature to prevent their posterior collapse. Advancements of 10 to 15 mm are usually required to adequately clear the posterior airway space of obstruction.

Although some authors have advocated maxillomandibular advancement as primary therapy for hypopharyngeal obstruction, we usually reserve this surgery for those who are incompletely treated with phase I surgery (36,77). Our experience has demonstrated reasonable response rates with phase I treatment; thus, we attempt less invasive surgery prior to MMO surgery. For those patients inadequately treated with phase I surgery, the source of obstruction is typically the hypopharynx.

Initially, MMO was advocated for patients with maxillomandibular deficiency. However, only approximately 40% of patients with SDB have contributing craniofacial deficiency (78). Potentially creating temporomandibular joint dysfunction or compromising facial esthetics was of concern in performing MMO in patients without mandibular or maxillary deficiency, but studies have since proven that MMO is effective in these patients without resulting in these complications. In fact, skeletal facial advancement may impart a more youthful esthetic appearance (79,80).

Maxillomandibular advancement had been used for many years to treat malocclusion. The surgery has undergone several modifications for the treatment of SDB. The primary modification is a bony advancement of 10 to 15 mm, which tends to be greater than those needed to treat malocclusion. Care must be taken to preserve the descending palatine arteries of the maxilla, and, the dental occlusion should be preserved. This is accomplished by placing arch bars or orthodontic bands prior to the osteotomies. A Le Fort I maxillary osteotomy is performed above the roots of the teeth. The maxilla is down fractured and then advanced anteriorly. Stabilization of the maxilla is accomplished with rigid plate fixation. Mandibular advancement is achieved by a sagittal split osteotomy (Fig. 7). Care is taken to preserve the inferior alveolar nerves. Fixation is maintained by bi-cortical screws and monocortical plating. Proper alignment of the dental occlusion is needed prior to fixation.

FIGURE 7 (See color insert.) Maxillo-mandibular advancement osteotomy (MMO). The maxilla and mandible are advanced 10 to 15 mm. A Le Fort I osteotomy and bilateral sagittal split mandibular osteotomy are performed. The advanced segments of bone are stabilized with bi-cortical screws and rigid plate fixation. Note the genioglossus advancement performed prior to MMO. Source: From Ref. 121.

FIGURE 7 (See color insert.) Maxillo-mandibular advancement osteotomy (MMO). The maxilla and mandible are advanced 10 to 15 mm. A Le Fort I osteotomy and bilateral sagittal split mandibular osteotomy are performed. The advanced segments of bone are stabilized with bi-cortical screws and rigid plate fixation. Note the genioglossus advancement performed prior to MMO. Source: From Ref. 121.

Published data regarding the results of MMO has been well established (47,49,77,81,82). In 1992, we reported 91 patients who underwent bimaxillary surgery. The success rate of phase II therapy was 97% (38). Despite the potential for some skeletal relapse, the long-term success of MMO remains greater than 90% (83). An enlarged posterior airway space can be visualized on postoperative cephalo-grams (Fig. 8). Ultimately, in order for surgery to be considered efficacious, it must

Powell And Riley Protocol
FIGURE 8 (See color insert.) Lateral cephalogram films. This patient underwent both phase I and phase II of the Powell-Riley protocol for sleep-disordered breathing. (A) Preoperative film. (B) Postoperative film—note the markedly widened posterior airway space (PAS).

achieve rates of cure similar to CPAP therapy. In 1990, Riley et al. (84) demonstrated no statistical difference between nasal CPAP and surgery in improving sleep architecture and SDB. Consequently, if a logical, stepwise surgical approach is used in treating SDB patients, cure rates similar to that of medical management can be offered.

As mentioned previously, loss of the airway is the most feared complication following surgery. Risk can be reduced by appropriately utilizing preoperative CPAP and controlling blood pressure (65,66). Necrosis of the palate has been observed as a result of compromised blood supply, although it is quite rare (85). Identifying and protecting the descending palatine vessels can prevent this complication. Skeletal relapse with resulting malocclusion may occur in 15% of patients. This usually does not result in recurrence of SDB, and can easily be managed with occlusal equilibration. Pain is well controlled with oral analgesics and is not as intense as palatal surgery. Perhaps the most common complaint following MMO surgery is anesthesia or paresthesias of the dentition and perioral region. This symptom is expected in the early recovery period and will resolve within 6 to 12 months for most patients.

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Responses

  • Giovanna
    Can sleep apnea be caused by sagital split astotomy?
    8 months ago

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