It is widely recognized that craniofacial skeletal abnormalities play a key role in causing upper airway obstruction. The cranial base, midface, and mandible are the anatomical structures involved.

Mandibular hypoplasia is the main cause of upper airway obstruction in newborns; it consists of a congenital anomaly of the jaw that can be identified from the twentieth week of pregnancy, using prenatal diagnostic techniques such as ultrasonography and fetal MRI (Pilu et al., 1986; Nemec et al., 2015). This condition develops within sequences that are determined by alterations in craniofacial morphogenesis, triggered by a single initial event that subsequently leads to other secondary defects, as in Pierre Robin sequence (PRS).

PRS is characterized by micrognathia, glossoptosis, and related breathing problems (Mackay, 2011). Cleft palate is frequently associated with this condition. A wide cleft palate is a typical finding, associated with a superior-posterior position of the tongue. The posterior displacement of the base of the tongue causes the respiratory obstructive symptoms.

Mandibular hypoplasia can also develop within syndromic disorders, characterized by a genetic or environmental cause that affects multiple stages of development during embryogenesis, as in Franceschetti, Nager, Miller, Marshall, and Stickler syndromes. While PRS always affects the lower jaw bilaterally, syndromes may have either unilateral (e.g. hemifacial microsomia and Goldenhar syndrome) or bilateral (Nager syndrome and Franceschetti syndrome) expression (Gangopadhyay et al., 2012).

Upper airway obstruction may not be continuous in newborns affected by micrognathia; patients can have an adequate air flow during the day and suffer from obstructive episodes only when they eat or sleep, due to a reduction in pharyngeal muscle tone. Obstructive sleep apnea syndrome (OSAS) is a breathing disorder that occurs during sleep and is characterized by prolonged partial upper airway obstruction and/or intermittent complete obstruction that disrupts normal ventilation (Shen et al., 2009). Patients may exhibit behavioral and daytime sleepiness. Additionally, if OSAS is not properly treated, it can lead to growth failure, cognitive disorders, and cardiovascular diseases (Gangopadhyay et al., 2012; Scott et al., 2011a, Scott et al., 2011b; Tibesar et al., 2010a, Tibesar et al., 2010b). The prevalence of sleep-disordered breathing (SDB) in children with craniofacial anomalies ranges from 40 to 50% (Luna-Paredes et al., 2012). In particular, Pierre Robin sequence has an incidence of SDB of 72.9% (Robison and Otteson, 2011) and Franceschetti syndrome presents a prevalence of 46% (Plomp et al., 2012).

Current treatments for mandibular hypoplasia include both conservative management and surgical procedures. Conservative management includes prone positioning, hyperextension of the head, manual advancement of the mandible, and palatal plate therapy (Maas and Poets, 2014). Oropharyngeal or nasopharyngeal cannulas (Mayo), non-invasive mechanical ventilation, and oral or nasotracheal intubation are also suitable options. Surgical procedures include tongue–lip adhesion (TLA), mandibular distraction osteogenesis (MDO), and tracheotomy. Tracheotomy is associated with significant morbidity and mortality (Carron et al., 2000). Better outcomes are achieved with MDO compared with TLA. TLA is not always successful in improving the patient's breathing or feeding, and also can contribute to an increased risk of aspiration (Li et al., 2002).

Mandibular distraction osteogenesis was introduced in 1992 by McCarthy (Karp et al., 1990) and subsequently performed on newborns affected by OSAS from the late 1990s. It was initially reserved for tracheostomized patients, in order to allow for decannulation. Currently, mandibular distraction osteogenesis is a widely adopted treatment for weaning off mechanical ventilation, avoiding the short- and long-term complications of a tracheotomy altogether. It is also considered by some authors as the gold-standard treatment for early intervention of upper airway obstruction in newborns affected by micrognathia when conservative management fails (Scott et al., 2011a, Scott et al., 2011b; Ow and Cheung, 2008).

Our longitudinal study analyzed the radiographic images of a large group of patients (n = 21) with mandibular retrognathia and OSAS, who underwent mandibular distraction at San Gerardo Hospital in Monza, Italy.

The aim of our study was to evaluate the long-term outcomes of mandibular distraction, in terms of mandibular growth as well as possible short-term and long-term surgical complications.