1 INTRODUCTION

Obstructive sleep apnea syndrome (OSA) results from partial or total obstruction of the upper airway during sleep due to narrowing or total obstruction of the upper airway. The airway narrowing or collapse necessitates the patient to increase his/her negative intrathoracic pressures during sleep which results in sleep fragmentation and excessive daytime somnolence as well as a decrease in life expectancy, increased risk for hypertension, myocardial infarction and cardiac arrhythmia.

Maxillofacial skeletal abnormality is a well-recognized predictor in OSA. Maxillomandibular deficiency results in diminished airway dimension which leads to nocturnal obstruction.^1,2 Currently, the most effective surgical procedure in the management of OSA is the expansion of facial skeleton by advancing the maxilla and mandible, i.e. maxillomandibular advancement (MMA). MMA achieves enlargement of the pharyngeal and hypopharyngeal airway by physically expanding the skeletal framework. In addition, the forward movement of the maxillomandibular complex improves the tension and collapsibility of the suprahyoid and velopharyngeal musculature. Lateral pharyngeal wall collapse, which has been shown to be a major factor in airway obstruction,³ is also shown to be lessened following MMA.⁴ The current MMA technique involves the use of maxillary Le Fort I osteotomy and mandibular sagittal split osteotomy to facilitate the forward movement of the maxillomandibular complex followed by the application of rigid fixation.⁵

Since the early recognition of the role of maxillofacial skeletal deformity in OSA, all of the emphasis of deformity recognition and treatment has been primarily limited to the sagittal plane. The transverse deficiency of the maxilla and/or mandible as a potential contributor and treatment of OSA has received little attention. Recently, the constriction of the maxilla has been suggested as a possible risk factor of OSA. In a comparative study between OSA and control subjects by Seto et al.,⁶ OSA subjects were found to have narrower, more tapered and shorter maxillary arches. Kushida et al.⁷ found that the intermolar distance of the maxilla is related to the presence of OSA. Cistulli et al.⁸ have reported that patients with Marfan’s syndrome, in which maxillary constriction is a common finding, have increased incidence of OSA and elevated nasal resistance. The relationship of nasal resistance and maxillary morphology has long been suggested in the orthodontic literature.

Despite the past success in conventional maxillofacial surgery for the treatment of airway obstruction, there is increasing interest in the use of distraction osteogenesis for skeletal expansion in treating OSA due to its feasibility in the pediatric population as well as the less invasive nature of the procedure. This chapter will discuss the method as well as relevant results.

2 DISTRACTION OSTEOGENESIS IN THEMAXILLOFACIAL REGION

Skeletal expansion by slow osseous distraction (distraction osteogenesis) is not new and has been previously studied extensively in orthopedic surgery. It has demonstrated acceptable feasibility, efficacy, safety, and reproducibility of its treatment results. In its simplest form, distraction osteogenesis (DO) describes the generation of new bone in the stretched fracture callus. A screw-driven appliance that is firmly attached to the bone fragments slowly pulls apart the cut/or fractured bony edges, and new bone can fill in the stretched callus tissue. DO was first described by Alessandro Codvilla in 1905, who first published the use of this technique in lengthening the long bone.⁹ However, it is Ilizarov who is credited with developing the current methods of DO.¹⁰ DO in the maxillofacial region was first investigated by Snyder et al.¹¹ in the canine mandible. Karp et al.¹² demonstrated that bone formation during DO in the maxillofacial region is similar to that of long bones, which is predominantly by intramembranous ossification. Surgical lengthening by DO in sagittal plane was first described by McCarthy, who reported on the application of DO of the human mandible in pediatric patients in 1992.¹³ The surgical expansion of the maxilla and mandible to increase the width by distraction osteogenesis was reported by Bell and Epker¹⁴ and Guerrero,¹⁵ respectively.

DO is a potentially new approach for the treatment of OSA by slowly expanding the mandible and/or the maxilla in the sagittal or frontal plane, thereby expanding the airway. This technique is less invasive than the traditional technique. It requires less tissue manipulation, less blood loss, and has less skeletal relapse potential.

3 BRIEF DESCRIPTION OFMAXILLOMANDIBULAR ADVANCEMENT

See Figure 54.1.

Fig. 54.1 Pre- and postoperative cephalometric radiographs and panoramic radiographs.

The procedure is performed in the operating room under general anesthesia technique. The maxillary advancement is a Le Fort I osteotomy. The procedure is modified for DO with the placement of bilateral maxillary distraction devices following a limited down-fracturing of the maxilla without extensive mobilization. In the mandible, the procedure consists of performing an osteotomy behind the last molar, followed by application of the intraoral distraction device. Following 5–7 days of latency period, the device will be activated two to four times per day to achieve 1 mm of bone lengthening per day. The total bone lengthening will be determined preoperatively based on the patient’s anatomy, dentition, facial appearance and the severity of OSAS. After the completion of distraction (approximately 1–3 weeks), the distraction devices are maintained in place for 2–3 months to allow bone ingrowth and healing. The distraction devices are then removed under either general anesthesia or intravenous sedation technique.