Maxillomandibular Advancement

Key points

  • Obstructive sleep apnea is underdiagnosed in Canada.

  • Canadian sleep specialists are reluctant to propose maxillomandibular advancement (MMA).

  • The Canadian public health insurance covers expenses related to sleep apnea investigation and MMA (with the exception of orthodontic treatment).

  • MMA treatment plan is based on a multiple of factors, such as obstructive sleep apnea severity, aesthetics, and the initial malocclusion.

Introduction

Obstructive sleep apnea (OSA) is a chronic medical condition characterized by a temporary reduction or a cessation of airflow. It is acknowledged that continuous positive airway pressure (CPAP) is the first line of treatment, but, like most patients affected by this disease, Canadians are looking for a definitive cure. Maxillomandibular advancement (MMA) is an effective surgical treatment that is nowadays more frequently proposed to the Canadian population, although there is still a general lack of knowledge among sleep specialists on its indications and efficacy. Similarly, general dentists tend to favor dental mandibular advancement devices (DMADs) because they are more familiar with them. The goal of this article is to expose the authors’ experience with MMA for the treatment of this condition.

An estimated 5.4 million Canadians have been diagnosed with OSA or at risk of developing it. In 2009, based on a questionnaire survey sent to 8647 adults, the Canadian Public Health Agency estimated that approximately 858,900 Canadians adults were diagnosed with OSA by their physician ; 75% of these patients were older than 45 years old. The study also reported that 26% of the Canadian population is at risk of developing OSA in the near future based on risk factors and symptoms of OSA.

The Canadian population is more aware of OSA, and referral to sleep clinics has increased in the recent years. The public health survey estimated that 76% of Canadians diagnosed with OSA and 4.8% of patients considered at high risk of OSA were referred for a sleep apnea investigation. OSA diagnosis in Canada seems to be made by doctors without a polysomnographic study. Access to a polysomnographic examination represents a challenge in many centers, and this may explain why 23% of patients who reported symptoms of OSA never had this test. Evans and colleagues published a study showing that the amount of sleep laboratories in the country is approximately 2 per 100,000 population.

Because patients living in rural areas have less access to these facilities, they are more likely to be undiagnosed and have more severe disease at time of diagnosis.

The Canadian health care system

In Canada, the health care system is public and OSA treatments are generally insured. This may vary slightly between provinces (10) and territories (3) because both are responsible for delivering health services. One possible drawback of this system is an increased waiting period to meet sleep specialists and to obtain appropriate diagnosis and treatment. This may be one of the reasons why the number of private sleep clinics has increased in the past decade. CPAP appliances and DMADs are usually at a patient’s expense. This is also the case for orthodontics even if it is judged necessary to proceed to MMA.

The dental community is biased toward the use of DMADs, and sleep physicians are reluctant to refer patients for MMA. The benefits and efficacy of MMA still need to be promoted as it is often considered as too invasive and risky by other sleep specialists. Results obtained with MMA in Canadian centers have been published, showing good clinical results.

The CHU de Québec-Université Laval-Hôpital de l’Enfant-Jésus experience and surgical technique

The authors’ academic institution performs more than 300 cases of standard orthognathic surgery per year. Referrals for MMA for OSA patients are increasing. Otorhinolaryngologists, pneumologists, family doctors, and dentists refer most OSA patients. At the authors’ institution, before considering MMA, all patients need a confirmed OSA diagnosis with polysomnography. A trial period of CPAP therapy is also strongly recommended unless obvious craniofacial anomalies are noted ( Fig. 1 ). If a patient has a dental malocclusion or a retrusive facial profile, a consultation with an orthodontist is recommended to decompensate the occlusion and allow more forward movement of the maxillomandibular complex. On the other hand, MMA may be accomplished without an orthodontic preparation.

Fig. 1
A ) Facial and ( B , C ) intraoral pictures of a 28-year-old male patient with severe retrognathia.

Preoperative planning

Once a patient is considered a good candidate for MMA, the following data are recorded: cephalometric and panoramic radiographs, CT, full facial photographs, dental impressions, and all other relevant clinical information. Maxillofacial orthognathic treatment plan is based on several factors. The aesthetics outcome related to MMA is explained to the patient. Negative aesthetics effects are possible but rare with low effect if the surgery is well planned.

For bimaxillary surgery, a counterclockwise rotation of the maxillomandibular complex is often planned to maximize the mandibular advancement to open the posterior airway and diminish collapsibility. The amount of advancement and rotation is based on the patient malocclusion, appearance, and OSA severity. The first goal is to correct the OSA by enhancing the airway and to correct the malocclusion by maintaining an aesthetic normal facial balance and a stable dental occlusion, although it is important to consider the patient facial appearance to minimize the negative effect of this approach. A patient with thick soft tissue tolerates an anticlockwise rotation and a large maxillary advancement better aesthetically than a patient with thin facial soft tissue. A patient with solely retrognathic mandible with an orthognathic maxilla and moderate OSA may benefit merely of a bilateral sagittal split osteotomy (BSSO) advancement with genioplasty only. Research has shown that a sole BSSO brings tridimensional volumetric changes in the airway by enlarging the airway space when a retrusive mandible is present.

Cephalometric radiograph is traced with the architectural and structural Delaire analysis. Delaire cephalometric analysis is based on skeletal points. Delaire analysis uses the nasopalatine canal and the menton region to determine mandible and maxillary positions. Those skeletal landmarks are less influenced by the dentoalveolar area of the patient, such as A and B points, and are proved to correlate the severity of apnea-hypopnea index (AHI) with the bimaxillary sagittal position with more efficacies. The authors use virtual surgical planning for all cases. This surgical planning allows analyzing the bony modification and future bimaxillary position more precisely. Both condyles are specifically placed in the posterior glenoid fossa.

For OSA patients treated by their orthodontist with multibracket appliances or clear aligners, surgical hooks or orthodontic brackets are installed prior to the surgery date.

Patient preparation

Patients are placed in supine position and put under general anesthesia with nasotracheal intubation. A nasogastric tube and arterial line are installed for all patients. Local anesthesia of the mucosa and inferior alveolar nerve blocs are performed using bupivacaine 0.5% with epinephrine 1:200,000 for postoperative anesthesia. Occlusal adjustments of the teeth are done when necessary at this point. For patients without active orthodontic treatment, temporary dental brackets or intermaxillary fixation (IMF) screws are installed for intraoperative IMF and postoperative guiding elastics when judged necessary. Otherwise the screws are removed at the end of surgery.

Surgical technique and approaches

The authors generally preconized a mandible-first sequence for OSA patients to obtain a more stable intermediate position; otherwise, the splint is too large and IMF is more difficult to place.

For the BSSO approach, bilateral vestibular incision is realized. Full subperiosteal dissection is performed and the lingula is identified. All ostectomies are performed using a combination of reciprocating saw and Lindemann bur. Splitting of the mandible according to the osteotomies is completed with osteotomes and bone spreaders. The inferior alveolar nerve is identified and bone interferences are removed.

The intermediate guiding splint is installed and patient is placed in IMF. The authors carefully adapt the proximal to the distal bone segment by grinding bone interferences with a surgical rasp. This is particularly important if fixation with bicortical screws is contemplated. Titanium mandibular rigid fixation is applied with either bicortical screws, titanium plates, or a combination of both ( Fig. 2 ). With mandibular advancement, the airway is then opened by advancement of the suprahyoid muscles, the anterior digastrics, and the mylohyoid muscles. IMF is released and the intermediate position is confirmed. Attention can then be on the maxilla.

Jan 19, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Maxillomandibular Advancement
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