Pediatrics and Neonatology (2013) 54, 153e160

Available online at www.sciencedirect.com

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REVIEW ARTICLE

Mandibular Distraction Osteogenesis in theMicrognathic Neonate: A Review forNeonatologists and Pediatricians

Paul Hong a,b,c,*, Michael Bezuhly a,d

a IWK Health Centre, Dalhousie Pediatric Craniofacial Group, Halifax, Nova Scotia, CanadabDivision of OtolaryngologyeHead and Neck Surgery, Department of Surgery, Dalhousie University, Halifax, Nova Scotia,Canadac School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadadDivision of Plastic and Reconstructive Surgery, Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada

Received Sep 17, 2012; accepted Nov 21, 2012

Key Wordsdistractionosteogenesis;

mandible;micrognathia;Pierre Robinsequence;

upper airwayobstruction

* Corresponding author. IWK Health CAvenue, PO Box 9700, Halifax, Nova S

E-mail address: Paul.Hong@iwk.ns

1875-9572/$36 Copyright ª 2012, Taiwhttp://dx.doi.org/10.1016/j.pedneo.2

In the past, severe neonatal upper airway obstruction secondary to micrognathia was managedwith a tracheostomy. Although effective, tracheostomy can cause many short-term and long-term complications. More recently, mandibular distraction osteogenesis (MDO) has becomea well-accepted surgical option in treating micrognathic newborns. Overall, MDO has been re-ported to be an effective intervention in alleviating the micrognathia-associated airway com-promise. Furthermore, it seems to be well tolerated and has supplanted the need fortracheostomy in many patients. Neonatologists and pediatricians commonly care for thesechildren, and therefore an up-to-date clinical narrative review regarding MDO is presentedto increase the awareness of this relatively new surgical option.Copyright ª 2012, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rightsreserved.

entre, 5850/5980 Universitycotia B3K 6R8, Canada.health.ca (P. Hong).

an Pediatric Association. Publish012.11.018

1. Introduction

Micrognathia is a congenital condition involving an abnor-mally undersized mandible. It tends to occur with glos-soptosis, and in some cases, U-shaped cleft palate.1,2 Thisconstellation of clinical features is now commonly referredto as Pierre Robin sequence (PRS). Craniofacial geneticdisorders, such as Stickler syndrome, Treacher Collins

ed by Elsevier Taiwan LLC. All rights reserved.

Figure 1 A photograph demonstrating a hypoplastic andretrusive mandible (micrognathia).

154 P. Hong, M. Bezuhly

syndrome, and hemifacial microsomia, can occur in con-junction with PRS. However, PRS is more commonlyobserved in isolation.2

Micrognathia can lead to upper airway compromise dueto posterior tongue collapse and physical obstruction of theoropharyngeal and hypopharyngeal regions. Although mostnewborns with micrognathia or PRS are either asympto-matic or can be managed with conservative therapy, somepatients may have significant airway obstructive andfeeding problems.3 Conservative therapy mainly includesclose monitoring with prone or lateral decubitis positioning.Other nonsurgical measures involve the use of temporarynasopharyngeal or oropharyngeal airways and the applica-tion of nasal continuous positive airway pressure.4 Fur-thermore, as the neonate grows, many will demonstratecatch-up mandibular growth, which occurs at a morerapid rate than other parts of the craniofacial skeleton.2e4

However, not all patients will respond to these noninvasiveinterventions.

Significant neonatal upper airway obstruction secondaryto micrognathia demands urgent medical attention. Tradi-tionally, tracheostomy has been the gold standard treat-ment for these patients.5 This procedure, however, cancause many short-term and long-term complications.6e8

Therefore, other methods of definitive airway manage-ment in this patient population are needed.

Mandibular distraction osteogenesis (MDO) is a relativelynew surgical treatment that involves gradually lengtheningthe mandible to correct the posterior tongue base positionto relieve the pharyngeal airway obstruction.9 Initially,reports of MDO during the first few days of life were limi-ted, but recent studies have provided more evidence toconsider when managing neonates with micrognathia.10e17

Neonatologists and pediatricians play a crucial role inthe perioperative management of hospitalized micro-gnathic newborns and are often involved in treating theassociated airway and feeding problems. This review willdiscuss the various management issues of micrognathicnewborns with emphasis on the safety and efficacy of MDO.The current review will serve to provide up-to-date infor-mation regarding MDO for the neonatologist and thepediatrician.

2. Review

A search of the online database of the National Library ofMedicine (PubMed) was performed to identify all publica-tions regarding MDO. All studies involving MDO in neonateswere included for the narrative review.

2.1. Pierre Robin sequence

The initial insult in PRS is the failed anterior growth of themandible. The exact cause of this anomaly is unknown buthas been hypothesized to be secondary to hyperflexion ofthe neck in utero.9 Some authors also suggest a primarygrowth disturbance, especially in syndromic PRS cases.9

The abnormally small mandible positions the tongue pos-teriorly and superiorly, which is termed glossoptosis, andcan lead to the development of U-shaped cleft palate bypreventing the midline fusion of the palatine shelves.9

Simultaneously, the retrodisplacement of the tongue canresult in oropharyngeal and hypopharyngeal obstruction,leading to varying degrees of respiratory distress.18 Inaddition, newborns may struggle with oral feeding, becauseof problems in coordinating respiration and swallowing inthe context of upper airway obstruction and sometimesa cleft palate.2

The diagnosis of micrognathia and PRS is usually made atbirth but can be made as early as the second trimester ofpregnancy with prenatal high-resolution ultrasonograms. Incertain cases, the neonatologist can be called upon duringthe delivery of prenatally diagnosed children with PRS.However, assessment of the oropharyngeal soft tissue isnot easily performed with prenatal ultrasonography andtherefore, predictions of which newborn will have airwayobstruction is not possible at this time.15

The most notable feature at birth will be the hypoplasticand retrusive mandible (Figure 1). The lower mandibularalveolus will be significantly posterior to the upper maxil-lary alveolus. Examination of the oral cavity and orophar-ynx will usually demonstrate a tongue position that isposterior and superior; some newborns may also havea cleft palate. In patients with syndromic PRS, other cra-niofacial features may be noted at birth.

2.2. General management of micrognathicnewborns

Most neonates with PRS will not require any surgical airwayintervention.2,19 Many patients will have a mild degree ofmicrognathia and will subsequently not present with asignificant upper airway compromise and/or feedingproblems. For those neonates with mild-to-moderate res-piratory distress, conservative measures are initially insti-tuted. Specifically, positioning maneuvers with pulseoximetry in an intensive care unit or other monitored unitsmay be sufficient in some children. This is due to thepresence of catch-up mandibular growth, which occursduring the first few months of life (mandible grows ata faster rate than other parts of the craniofacial skeleton).However, catch-up growth is not always predictable andcan only lead to partial improvement in craniofacial

Neonatal mandibular distraction osteogenesis 155

proportions.20,21 Furthermore, children with PRS and asso-ciated genetic syndromes may not demonstrate any signif-icant catch-up growth.

More invasive interventions include continuous positiveairway pressure, nasopharyngeal or oropharyngeal airways,and endotracheal intubation, but they offer only temporaryrelief of the upper airway obstruction because they are nottolerated for long duration.2,19 Mostly, newborns whorequire prolonged treatment with these measures mayrequire a more definitive surgical intervention.

Currently, three surgical options exist for the micro-gnathic newborn: tongueelip adhesion (TLA), tracheos-tomy, and MDO.

Various techniques of TLAs have been described,22 butthey all involve the tongue being surgically fused to theanterior lower lip to hold the tongue in an anterior position.The adhesion is usually reversed with another surgicalprocedure when the patient is 9e12 months of age.Although TLA has been reported to be successful by someauthors, the tethering of the tongue can lead to swallowingdifficulties, which may necessitate the placement ofnasogastric or gastrostomy feeding tubes.2,23e25 Fur-thermore, the underlying anomaly is not fully addressed,and therefore, many craniofacial centers have abandonedTLA as a viable option.19 This is also the case at the authors’institution.

Tracheostomy immediately relieves the upper airwayobstruction and is still considered the gold standard treat-ment option by many clinicians. However, the associatedmortality rate of 1e4%26,27 and the significant morbidity,which includes accidental decannulation, tracheostomytube obstruction, bleeding, pneumonia, granulation tissueformation, cricoid cartilage injury, swallowing dysfunction,speech and language developmental problems, and latedecannulations, make tracheostomy an option fraught withserious limitations.5,28e30 Furthermore, children with long-term tracheostomy require nursing care at home and intheir educational institutions, along with monitoring andsuction equipment.28,30 In addition, negative psychosocialconsequences for the caregivers and family members ofchildren with tracheostomies have been documented.5,30

Figure 2 Photographs of a child with micrognathia and air-way obstruction (A) before and (B) after mandibular distractionosteogenesis. Note the change in the profile of the lower face.

2.3. Mandibular distraction osteogenesis

Distraction osteogenesis is a method of producing new bonewith a surgical procedure that involves an osteotomy (bonycut) and gradual lengthening of the divided bony segments.Ilizarov31 was the first to describe this procedure in longbones on the basis of the “tensionestress” principle. Hesuggested that the biomechanical factors mediating theprocess of distraction osteogenesis (gradual lengthening)result in a constant and localized tension and stress, whichpromotes metabolic activation, angiogenesis, and newbone formation.

The addition of distraction osteogenesis to craniofacialsurgery has revolutionized the surgical management ofcongenital and acquired defects, and the procedure hasbecome widely accepted at several children’s hospitalsthroughout the world. McCarthy and colleagues32 firstintroduced the use of distraction osteogenesis to lengthenthe human mandible for the treatment of hemifacial

microsomia in 1992. Since then, the indications for MDOhave rapidly expanded to include airway obstruction in themicrognathic infant (Figures 2 and 3).

Distraction osteogenesis of the mandible relieves thetongue base obstruction by lengthening the mandible. Morespecifically, because of genioglossus and other muscularattachments of the tongue to the mandible, MDO positionsthe tongue more anteriorly, thereby reducing theglossoptosis.

The surgical procedure of MDO is composed of threephases: (1) osteotomy and latency, (2) distraction, and (3)consolidation. The first phase involves a surgical procedurewhere osteotomies are made on the mandible, and dis-tractor devices are placed spanning the proximal and distalsegments of the bone to be distracted (Figure 4). The dis-traction phase soon follows, where the distractor device isactivated to gradually lengthen the mandibular bone. Therate of distraction is typically 1e2 mm/day and is per-formed with a turning device that attaches to an externalpart of the distractor device. Because the lengtheningprocess is steady and gradual, the overlying soft tissues willstretch to accommodate the newly expanding bonyframework. This deliberate process is usually very welltolerated (no analgesia required), and the neonatal patientis able to resume a normal diet during the early post-operative period. Moreover, most patients will demonstratea notable improvement in their respiratory status after

Figure 3 Photographs of a child with micrognathia and air-way obstruction (A) before and (B) after mandibular distractionosteogenesis. Note that the end of the distractor device comesthrough the skin (B). This part is engaged and turned to grad-ually advance the mandible.

156 P. Hong, M. Bezuhly

a few days of distraction (usually 7e14 days), and they canbe transferred to a regular hospital ward or even allowed togo home. The final phase is the consolidation phase, whichinvolves healing and solidifying of the newly generatedbone. During this phase, which usually takes about 1e2

Figure 4 The internal distractor device is placed along themandible, spanning the osteotomy site. The activator end,which protrudes through the skin, is turned to advance themandible.

months, the distractor device is left in place to act asa fixation device.

3. Preoperative Investigations

At present, there are no specific indications or guidelinesthat can be applied when evaluating newborns for MDO.Many surgeons use both subjective and objective measuresto assess preoperative candidacy.

3.1. Clinical and laboratory assessments

Preoperative clinical assessments should include compre-hensive pulmonary and neurological examinations.10,16

Specifically, the degree of respiratory distress and upperairway compromise, oxygen saturation levels, and signs ofneurological abnormalities, such as hypotonia, should bedocumented. For instance, in the presence of generalizedhypotonia, MDO should not be performed because theclinical symptoms may not strictly be due to themicrognathia-associated tongue base obstruction, and thepatient may still require a tracheostomy or other airwayinterventions.

Laboratory investigations mainly include blood gases toassess the level of pCO2. In our institution, a severeobstruction is partially defined as a persistent pCO2 greaterthan 50 mmHg, in addition to the clinical findings.

3.2. Feeding and reflux evaluation

Clinical evaluation of the volume, frequency, and quality ofsuccessful feeding (bottle or breastfeeding), as well asappropriate weight gain, and the inability to concurrentlyfeed and breath adequately, must be analyzed indetail9,14,16 when considering MDO. A diligent assessment ofreflux and swallowing dysfunction with pH probe, swallowstudies, and feeding evaluations can help determine can-didacy, as some children with significant reflux can havepoor postoperative outcomes.10,11 However, some authorsreport that feeding and swallowing problems, along withreflux, all tend to improve post-MDO, and therefore refluxshould not be considered a contraindication for distractionosteogenesis.14,33

3.3. Imaging workup

Commonly used preoperative imaging studies include ra-diographs and three-dimensional computed tomographyscans (Figure 5), which can readily show the details of thedeficient mandible, which allows proper planning of theosteotomies.4,10,34 More importantly, the imaging studiescan show the location of the tooth buds and the inferioralveolar nerve, which are ideally avoided during surgery.

Newer imaging techniques, such as virtual bronchos-copies, may have a role in evaluating neonates with PRSbecause distal levels of airway obstruction, such as tra-cheomalacia, can be ruled out. For such patients with otherareas of airway obstruction, relieving the tongue baseobstruction with distraction osteogenesis may not obviatethe need for a tracheostomy.

Figure 5 Three-dimensional reconstructed computed tomo-graphic image of a neonate with Pierre Robin sequence. Notethe hypoplastic mandible.

Neonatal mandibular distraction osteogenesis 157

3.4. Polysomnography

Another objective investigation that can be carried out ispolysomnography (PSG) or sleep study. PSG can documentthe frequency and duration of apneic episodes, as well asthe severity of oxygen desaturations.10 More importantly,PSG will assess for central apneas, which is crucial to ruleout for success after MDO.4 Several cases of failed dis-traction procedures have been reported secondary toneurological hypotonia and central hypoventilatory syn-dromes,4,11,16 which may have been noted with a preoper-ative sleep study.

However, PSG is not always available or easily obtain-able at many centers. Furthermore, the obstructive epi-sodes may occur mostly during awake hours. To this end,some have argued that a sleep study is not necessarybecause acute airway obstruction is not a function of sleep,and the presentation is often worse when patients are morealert and agitated.4,10

3.5. Airway endoscopy

Perhaps the most important preoperative investigation fornewborns with micrognathia is airway endoscopy. Awakeflexible laryngoscopy in the micrognathic neonate canclearly demonstrate a tongue base obstruction at the levelof the oropharynx35; in addition, a jaw thrust maneuver tomimic the airway changes induced by MDO can be per-formed.35 This maneuver can be a predictor of the poten-tial success of the MDO procedure.

Another important role for airway endoscopy is to assessfor other levels of airway obstruction. This involves bothawake flexible laryngoscopy to rule out dynamic upperairway obstructive pathologies, such as laryngomalacia,

and formal bronchoscopies to ensure the absence of distalairway lesions, such as tracheomalacia.9,11,16 For thosenewborns with multilevel obstructions, additional airwayprocedures may be necessary, in addition to MDO.4

4. Distraction Osteogenesis and AirwayObstruction

Several case series have demonstrated the effectivenessof MDO in alleviating upper airway obstruction in neo-nates, infants, and older children with PRS.11,14e16,35e39

Most patients were able to avoid tracheostomies andthose who already had tracheostomies were able to bedecannulated. In addition, a meta-analysis of MDO wasperformed by Ow and Cheung in 2008.17 This reviewstudied 178 publications, which yielded 1185 patients.Success in preventing tracheostomy was achieved in 91.3%of neonates and infants, but there were no detailsregarding the failures.17 Kolstad and colleagues39 retro-spectively examined the effectiveness and complicationsof MDO in newborns (�35 days old), early infants (36 daysto 5 months), and older children (>5 months). Overall, nosignificant differences in success rates between the groupswere observed, and MDO was successful in 90% (9 of 10) ofnewborns.

Although there is now little debate about the efficacy ofMDO in relieving micrognathia associated airway obstruc-tion, the appropriate age to perform the surgery has notfully been settled. Newborns as young as 5 days old havebeen successfully managed with MDO,16 and early surgicalintervention seems to be safe and well tolerated. There-fore, the initial concern regarding the small size of theneonatal mandible and the lack of mineralization for MDOoperation is not truly valid.

MDO has been reported to be effective in relieving upperairway obstruction in micrognathic neonates, but severalauthors have reported on the failure of distraction tofully alleviate symptoms of airway compromise toallow avoidance of tracheostomies in some children.10,16,40

Specifically, children with syndromic PRS tend to have lesssuccessful outcomes, and some have required repeat MDOprocedures to achieve full resolution of airway-relatedsymptoms. The low success rate of distraction osteo-genesis in children with syndromic micrognathia maybe attributed to many different factors such as neurologicaldysfunction, other levels of airway obstruction, andother medical problems.10 Subsequently, some authorssuggest a more conservative management strategy in thispopulation.10,41

5. Distraction Osteogenesis and FeedingProblems

Neonatal feeding is closely related to the health of theneonatal airway and recent studies on MDO have focused onfeeding improvements, as well as airway relief, in childrenwith micrognathia.14e16,33 Overall, micrognathic childrenmanaged with distraction have improved outcomes in oralfeeding and many patients can avoid enteral feeding vianasogastric or gastrostomy tubes.

158 P. Hong, M. Bezuhly

6. Technical Aspects of DistractionOsteogenesis

6.1. Complications

Management of complications of MDO has improved overtime as better devices and equipment became available.Currently, there are two main types of distraction devices(see below) and several different surgical approaches, andeach has its own associated complications. Less commonly,they include the following: temporomandibular jointankylosis, Greenstick fracture, osteomyelitis, tooth budinjury, premature union, malunion, pin or device mobility,device failure, facial nerve paresis/paralysis, cheek ab-scess, open bite deformity, and dentigerous cyst forma-tion.10,15,42 More commonly encountered complicationsinclude wound infection, temporary paresthesia, andscarring at external pin sites.10,15 Of course, failure todecannulate and requirement of other airway in-terventions are major complications as already discussedabove.

Because MDO is still relatively new, the long-term com-plications have been poorly documented.2,23,24 However,communications at scientific meetings and more recentarticles have demonstrated that long-term complications,such as relapse or dental developmental problems, are notcommon.41

6.2. Distraction osteogenesis devices

At present, there are two main types of distraction de-vices: external and internal. External devices (Figure 6)have been in use longer, whereas the internal device(Figure 4) is relatively new. The major advantage ofexternal device is the multidirectional vectors that can beapplied during the distraction phase. Subsequently, thereis an ability to adjust the direction of advancement afterthe surgery. Disadvantages include greater risk to marginalmandibular nerve and scars at external pin sites.35 More-over, owing to the bulkiness of the external devices, theneonatal intensive care unit (NICU) team may not be very

Figure 6 An external mandibular distractor device (KLSMartin, LP, Jacksonville, FL, USA).

comfortable with managing these newborns in the earlypostoperative period. More specifically, if inadvertentextubation occurred during the early phase of mandibularadvancement, the NICU team may be uncomfortable withreintubation.

Internal devices are becoming more popular as there isno cumbersome external device to deal with during thedistraction and consolidation periods, and there is no risk ofpin-associated scar formation or infection. The major dis-advantage of the internal distraction device is the unidi-rectional or linear vector of movement, which requiresmeticulous planning of osteotomies and distractor place-ment in the operating room.

6.3. Extubation and decannulation of tracheostomy

Removal of the endotracheal tube after the operation canoccur at any time when the airway caliber has improved.This can occur during the distraction phase or at the start ofthe consolidation phase.

Decannulation for previously tracheostomized childrenshould involve comprehensive airway endoscopy, includingflexible laryngoscopy and bronchoscopy. The removal oftracheostomy typically occurs at the time of the distractorremoval at the end of the consolidation phase or approx-imately 1e2 months after distractor removal.4

6.4. Cost-effectiveness of distraction osteogenesis

As mentioned above, tracheostomy is associated withcomplications, long after the procedure has been per-formed.6e8 After tracheostomy, a prolonged hospital stay istypical, because the tracheostomy tube has to be changedon multiple occasions and the caregivers require adequatetime to be educated on tracheostomy-associated care. Inaddition, there is a great long-term cost related to tra-cheostomy care (see above).

Distraction osteogenesis also bears high costs owing tothe operative equipment but the duration of stay in theNICU and hospital tends to be less when compared tochildren who undergo tracheostomy.43 Moreover, there aretypically no long-term costs associated with patients un-dergoing MDO.

Two cost studies comparing tracheostomy versus MDOboth demonstrated that MDO seems to be more costeffective.43,44 This is in keeping with the fact that MDOpatients are usually discharged home earlier.

6.5. Future direction of distraction osteogenesis

The future distraction of MDO lies in new technologicaldevelopments and refinements of the procedure itself.Three-dimensional surgical planning with novel imagingsoftware and resorbable distraction devices that have suf-ficient strength are under development, which should makethe operation more efficient and precise.

Moreover, further understanding of the biochemical andmolecular mechanisms involved in MDO will lead to theenhancement and hastening of the bone healing con-solidation phase.45e47

Neonatal mandibular distraction osteogenesis 159

7. Conclusion

Although most children with PRS can be managed withconservative measures, MDO in the neonate with micro-gnathia can be an effective and well-tolerated treatmentoption to relieve the upper airway obstruction. It should beconsidered as an acceptable alternative to tracheostomy inselected patients.

For managing newborns with PRS, a multidisciplinaryapproach involving a neonatal intensivist or a pediatricianwith experience in neonatal respiratory medicine, a pedi-atric anesthesiologist, and a craniofacial surgeon, alongwith other allied health professionals, is preferred.

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