Surgical-Orthodontic Considerations in Subcranial and ... · Le Fort III osteotomy Le Fort II osteotomy Monobloc osteotomy Subcranial distraction ... Monobloc frontofacial distraction

Surgical-OrthodonticConsiderations in
Subcranial and FrontofacialDistraction Richard A. Hopper, MD, MSa, Hitesh Kapadia, DDS, PhDb,Srinivas M. Susarla, DMD, MD, MPHc,*
KEYWORDS

� Le Fort III osteotomy � Le Fort II osteotomy � Monobloc osteotomy � Subcranial distraction� Counterclockwise craniofacial distraction � Frontofacial advancement� Syndromic craniosynostosis

KEY POINTS

� Distraction osteogenesis can be safely used for subcranial (Le Fort II, Le Fort III) or frontofacial(monobloc) advancements; proper orthodontic-surgical coordination is critical for a successfulresult.

� Midface distraction at the Le Fort III level is a valuable tool for managing the midface deficiencywhen the degree of hypoplasia is uniform across the midface (eg, Crouzon syndrome).

� Midface distraction osteogenesis at the Le Fort II level is useful for management of nasomaxillaryhypoplasia (eg, Binder syndrome) or, when done in conjunction with zygomatic repositioning, formanagement of differential hypoplasia of the central midface relative to the orbitozygomatic com-plex (eg, Apert syndrome, achondroplasia).

� Frontofacial distraction can be used for management of midface hypoplasia in the context of ante-rior cranial vault constriction (eg, syndromic midface hypoplasia in the setting of intracranial hyper-tension). Monobloc frontofacial distraction advances the frontal bone and midface as a single unit.

� Synchronous counterclockwise rotation of the maxillomandibular complex is an emerging tech-nique for management of complex hypoplasia involving the midface and mandible (eg, TreacherCollins syndrome).

BACKGROUND

Distraction osteogenesis, initially pioneered formanagement of limb-length discrepancies, hasbeen a major innovation in craniomaxillofacial sur-gery.1–5 Although craniofacial distraction wasinitially described for management of mandibular

Ethics Statement: All guidelines in the Declaration of Hesent was obtained for the use of clinical photographs.a Craniofacial Center, Division of Plastic and CraniofacialWay NE, Seattle, WA 98105, USA; b Craniofacial Centerdren’s Hospital, 4800 Sand Point Way NE, Seattle, WA 98facial and Plastic Surgery and Oral-Maxillofacial SurgerNE, Seattle, WA 98105, USA* Corresponding author.E-mail address: [email protected]

Oral Maxillofacial Surg Clin N Am 32 (2020) 309–320https://doi.org/10.1016/j.coms.2020.01.0051042-3699/20/� 2020 Elsevier Inc. All rights reserved.

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hypoplasia, the technique has been effectivelyapplied to myriad craniofacial differences,including midface deficiency, craniosynostosis,dentoalveolar hypoplasia, and management ofhypertelorism. The shortcomings and morbidityof conventional osteotomies for management ofcomplex subcranial and frontofacial deformities

lsinki were followed in the course of this work. Con-

Surgery, Seattle Children’s Hospital, 4800 Sand Point, Division of Craniofacial Orthodontics, Seattle Chil-105, USA; c Craniofacial Center, Divisions of Cranio-y, Seattle Children’s Hospital, 4800 Sand Point Way

RG

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HOSPITAL from ClinicalKey.com by Elsevier on August 19, 2020.ion. Copyright ©2020. Elsevier Inc. All rights reserved.

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Hopper et al310

have been long recognized: length of operations,blood loss, hospital stay, necessity for bone graft-ing, inadequate soft tissue results, infection, andrelapse.1–5 There is an increasing volume of datademonstrating the immediate efficacy and stabilityof subcranial and frontofacial distraction for man-agement of complex morphologic deficienciesaffecting the upper two-thirds of the face.6–14

Although perioperative morbidity rates for subcra-nial and frontofacial distraction remain significantdue to the complexity of the regional anatomyand procedural details, in many centers, distrac-tion procedures have replaced conventionalosteotomies for management of upper and mid-face deficiency.7–17

GOALS OF SUBCRANIAL AND FRONTOFACIALDISTRACTION

The primary goal of subcranial or frontofacialdistraction osteogenesis is to reposition the hypo-plastic upper or midfacial skeleton to correct (orovercorrect) the developmental deficiency.Recognition of the specific deficiencies byanatomic region (anterior cranial vault, orbitozygo-matic complex, nasal pyramid, and maxilla) is crit-ical for treatment success. Osteotomy patterns aretailored to the morphologic characteristics thatneed to be addressed (Fig. 1).In a patient with Crouzon syndrome, there is a

proportionate midface discrepancy—the degreeof hypoplasia in the orbitozygomatic regionmatches that of the nasomaxillary complex; theCrouzon phenotype is a morphologically normalmidface in an abnormal position (Fig. 2). Correc-tion at this level, via a Le Fort III distraction, is pri-marily related to improving the relationshipbetween the infraorbital rim and anterior cornea(correcting exorbitism).In contrast, the patient with Apert syndrome will

have a midface deficiency that is dispropor-tionate—the central midface hypoplasia is more

and may be combined with bilateral inverted-L mandibcraniofacial rotation. Segmentation of the Le Fort III ostallow for differential movement of the orbitozygomatic cright). Severe midface deficiency in the setting of cranialfronto-orbital and Le Fort III advancement (monobloc adv

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profound than the zygomatic hypoplasia. TheApert phenotype is a morphologically abnormalmidface in an abnormal position (Fig. 3). Correc-tion in this context is differential between thelateral and central midface. Correction of exorbi-tism is accomplished with zygomatic reposition-ing; the central vertical and sagittal midfacedeficiency is addressed with Le Fort II distraction.Patients with syndromic midface hypoplasia

with concomitant intracranial hypertension relatedto cranial vault constriction present a more chal-lenging clinical picture. Morphologic characteris-tics include frontal retrusion, exorbitism, andconcomitant midface hypoplasia (Fig. 4). In thiscontext, frontofacial advancement via monoblocdistraction is an effective approach for addressingthe anterior cranial vault and midface deficienciessimultaneously.Complex clockwise rotational deformities

involving the mid- and lower-facial skeleton arecharacterized by bimaxillary retrognathism witha class II skeletal pattern, long anterior faceheight, steep mandibular and palatal planes,and airway obstruction. For this phenotype, syn-chronous counterclockwise rotation of the maxil-lomandibular complex is an effective techniquefor correcting the maxillomandibular position,palatal and mandibular planes, anterior and pos-terior face heights, and improving airway dy-namics (Fig. 5).

TREATMENT PLANNING

As with any surgical procedure, appropriate pre-operative evaluation, diagnosis, and treatmentplanning based on sound principles are the keysto a successful result.18 A comprehensive dentofa-cial assessment, including both the hard and softtissues, is paramount. Objective assessment ofcranial morphology, globe position, malar projec-tion, nasal morphology, maxillary and mandibularsagittal and vertical positioning, as well as a

Fig. 1. Different patterns of osteotomydesigns for correction of midface hypo-plasia. The Le Fort III osteotomy (left)will result in separation of the entiremidface from the cranial base, allow-ing advancement of the orbitozygo-matic and nasomaxillary complexes asa single unit. The Le Fort II osteotomy(middle left) will allow for advance-ment of the nasomaxillary complex

ular osteotomies for synchronous counterclockwiseeotomy (Le Fort II with zygomatic repositioning) canomplex relative to the nasomaxillary segment (middlevault constriction can be addressed with simultaneousancement, right).

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Fig. 2. Midface hypoplasia Crouzon syndrome. The midface deficiency is evenly distributed between the centraland lateral midface. Clinically, this will be evident with poor malar support, exorbitism, and a class III profile.Correction of this specific midface morphology can be reliably accomplished with Le Fort III level distraction.

Fig. 3. Midface hypoplasia Apert syndrome. The midface deficiency is differentially distributed. The lateral orbi-tozyomgatic regions are hypoplastic, which is clinically evident as poor malar support and exorbitism. The centralmidface exhibits vertical and sagittal hypoplasia that is more severe than the lateral midface hypoplasia. Differ-ential correction is indicated with zygomatic repositioning and Le Fort II level distraction with a downward andforward vector.

Subcranial and Frontofacial Distraction 311

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Fig. 4. Frontofacial dysmorphology in a patient with Crouzon syndrome who presented with multiple cranial de-fects, obstructive sleep apnea (AHI 62.6), intracranial hypertension, frontal and supraorbital retrusion, malignantproptosis, and midface hypoplasia. Management of the midface deformity in the context of anterior cranial vaultconstriction can be accomplished with monobloc frontofacial distraction.

Fig. 5. Complex craniomaxillofacial discrepancy in Treacher Collins syndrome. There is bilateral zygomatic hypo-plasia, bimaxillary retrognathism, a long anterior face height, and steep palatal and mandibular plane angles.This constellation of skeletal differences is associated with clockwise rotation of the mid- and lower-face andis amenable to correction with counterclockwise craniofacial distraction (C3DO) using a Le Fort II osteotomywith concomitant bilateral mandibular osteotomies and subsequent synchronous maxillomandibular distraction.

Hopper et al312



detailed intraoral assessment, focusing on hy-giene, presence/absence of teeth, state of thedentition, crowding, transverse relationships, andocclusal plane orientation is necessary. Ophthal-mologic assessment is an important adjunct in pa-tients with exorbitism and those at risk forintracranial hypertension. Neurosurgical assess-ment is critical for patients undergoing frontofacialprocedures.

Three-dimensional computed tomographicscans are critical for both diagnosis and treatment.Three-dimensional visualization of the specificanatomy is necessary to identify the specificmorphologic deficiencies, plan appropriatedistraction vectors, safely execute osteotomiesand device placement, and overcome anatomicchallenges such as persistent bony defects,shunts, sensory nerves, and developing dentition.Dental models (cast or digital) complement imag-ing modalities in this regard and remain essentialfor evaluating potential occlusal interferences

Fig. 6. Midface distraction appliances can be internal (topface distraction can be tooth-borne (top right)25 or bonecally placed in the lateral orbitozygomatic region (bottorotation of the distracted segment.25 Tooth-borne devices


and for splint fabrication. Virtual surgical planningis used in many cases and affords an opportunityto visualize, in all three dimensions, the proposedskeletal movements and their impact on cephalo-metric parameters (Fig. 6).

The goals of treatment should be clearly estab-lished early in planning, with a focus on treatmentplans tailored to the specific characteristics of themidface deficiency. Patients undergoing distrac-tion procedures at the Le Fort II or Le Fort III levelsare frequently in the mixed dentition. In this popu-lation, maxillary expansion and leveling of theocclusal plane may be required before surgicalintervention. Pediatric dental assessment isnecessary to manage active decay and reinforcethe importance of excellent oral hygiene.

Patients undergoing frontofacial distraction pro-cedures are frequently medically complex andrequire a collaborative, team-centered approach,including a craniofacial surgeon, neurosurgeon,ophthalmologist, orthodontist, and pediatric

left)24 or external. External distraction devices for mid--borne (bottom left).26 Additional fixation posts, typi-m right) help control the upper midface and preventrequire a prefabricated splint.


Hopper et al314

dentist. Although there remains controversyregarding early monobloc procedures (<2 yearsof age), older patients undergoing frontofacial ad-vancements have dental needs similar to patientsin the mixed dentition undergoing subcranial mid-face advancements. Preoperative planning forfrontofacial distraction should take into accountthe specific cranial dysmorphology, including thepresence of cranial defects and shunts. Coordi-nated treatment planning frequently allows forcustom alloplastic cranioplasty to address cranialdefects at the time of frontofacial osteotomies.

DISTRACTION DEVICES

The distraction apparatus (Fig. 7) can be internal(directly affixed to bone) or external (halo device).Internal devices can be used to span the osteot-omy gap without a splint, with fixation placedabove and below the osteotomy or with a splint,with the inferior plate limb affixed to the splint.Similarly, external devices can be subdividedinto those that use tooth-borne splints versusbone-borne fixation to connect to the externalframework. Practitioner preferences vary in thechoice of device, and each type has specific ad-vantages and disadvantages. Purported advan-tages of external devices are related to therelative ease of placement, with less extensivesubperiosteal dissection necessary, as well asdifferential forces (can “push” and “pull”), and,perhaps most importantly, 3-dimensional controlof movement vectors. These advantages must

Fig. 7. Virtual surgical planning is an important adjunct fmities. Precise 3-dimensional visualization of the pertinentwhen needed, fabricate cutting guides (left: cutting temcraniofacial distraction osteogenesis (C3DO), with guidemovements along the planned vector can be demonstrachanges (middle and right: virtual surgical plan depictingHopper RA, Kapadia H, Susarla S, et al. Counterctracheostomy-dependent children with Treacher Collinswith permission.)


be weighed against the patient’s tolerance for acumbersome device that may become loose ordislodged and the risks of pin site infections. In-ternal devices are generally well hidden andplaced closer to the primary osteotomy sites,theoretically reducing torque. However, place-ment is more challenging and requires extensiveperiosteal stripping, more significant staged pro-cedures for device placement and removal, anddistraction may be limited both in terms of magni-tude and direction.

SPLINT FABRICATION AND APPLICATION

With tooth-borne external midface distraction, aprefabricated occlusal splint is necessary(Fig. 8).13,19,20 The splint is fabricated by usingan orthodontic headgear bow as a frameworkwithin an acrylic occlusal registration. The internalwire is used to conform to the dentoalveolarmorphology of the maxilla; the external wire isbent at 90-degree angle to accommodateoutrigger hooks. The height of the outrigger hooksdepends on both the patient’s age and theplanned distraction vector. The transverse dimen-sion between the external wire limbs is slightlywider than the alar base width. The sagittal posi-tion of the external framework relative to theacrylic plate is based on the patient’s lip thickness.The internal wire is embedded within a self-curingdental acrylic resin. The completed splint is thenpolished, both for patient comfort and to removesurface irregularities that are prone to plaque

or management of complex maxillomandibular defor-anatomy allows the surgeon to plan osteotomies and,plate for inverted-L osteotomies for counterclockwiseholes for transpharyngeal pin placement). Projectedted, with associated measurement of cephalometricpre- and post-distraction positions for C3DO). (Fromlockwise craniofacial distraction osteogenesis forsyndrome. Plast Reconstr Surg. 2018;142(2):447–57;


Fig. 8. Splint fabrication for external midface distraction. An orthodontic headgear bow is used for the frame-work. The internal wire is adapted to the maxillary arch form; the external wire is bent at a 90-degree angleto accommodate the outrigger hooks (top left). Proper orientation of the external framework requires meticu-lous attention. The width between the vertical limbs should be slightly larger than the alar base width (top right).The sagittal position of the bend should account for the upper lip thickness (bottom left). The final acrylatedsplint (bottom right).


accumulation. Intraoperatively, the splint iscemented to the maxillary dentition using a light-cured glass ionomer cement. In patients with oli-godontia or where additional stability is otherwiseneeded, circum-zygomatic and circum-piriformwires (26-gauge) can be used to reinforce thesplint and prevent dislodgement during activation.Once the splint is affixed to the teeth, it is con-nected to the rigid external device frame via 26-gauge stainless steel wires to the transverse bar.The vertical rod attachment can then be adjustedto achieve the appropriate height for the planneddistraction vector.13

With Le Fort II and Le Fort III distraction proced-ures, the center of resistance for midfaceadvancement is located slightly above themidpoint between the maxillary occlusal planeand nasion.19,20 Application of the distractionforce at this level will reliably advance the uppermidface without affecting the occlusal plane. Pullof the pterygomasseteric sling tends to inferiorlyreposition the posterior aspect of the Le Fort II orLe Fort III segment—if this is not accounted for,


an anterior open bite will result from counterclock-wise rotation of the midface (ie, if the distractionforce is too low). Conversely, a distraction forceapplied too high will result in clockwise rotationof the midface complex, resulting in overadvance-ment of the orbitozygomatic regions and possibleenophthalmos.

For frontofacial advancements, the center ofrotation will be located higher in the midface,resulting in a longer lever arm between theocclusal plane and center of rotation. Rotationalmovements are less frequently problematic inthis group, due to the presence of additional stabi-lization posts within the lateral midface, but thevector of distraction needs to be continuallyassessed with serial lateral cephalograms, toensure a vector parallel to the Frankfort horizontal.

In patients undergoing synchronous counter-clockwise craniofacial distraction procedures, aLe Fort II osteotomy is performed in conjunctionwith bilateral mandibular inverted-L osteoto-mies.14 A custom acrylic occlusal splint, similarto that used for external midface distraction, but


Hopper et al316

adapted to include the mandibular dentition, isaffixed to the teeth, and the patient is placed intomaxillomandibular fixation with transpalatal andcircummandibular wires (26-gauge). The splintconstruct is then wired to the activation armswith a 45-degree upward vector relative to theFrankfort horizontal.

PERIOPERATIVE ORTHODONTIC TREATMENT

During distraction: once the planned osteotomiesare completed and the prefabricated occlusalsplint is affixed to the midface, the patient willhave a latency period of approximately 5 days.The device is then activated at a rate of 0.5 mmtwice a day. Distraction is complete when the pre-determined endpoints have been achieved. WithLe Fort III distraction, this is predicated on thelateral orbitozygomatic contour and correction ofexorbitism (Fig. 9). With Le Fort II distraction, thisis based on the nasal length and vertical heightof the central midface (Fig. 10).13 For frontofacialadvancement, the distraction endpoints are deter-mined by the position of the external orbit relativeto the anterior cornea, frontal bone projection, andmaxillary incisor position (Fig. 11). In growing pa-tients, a goal overjet of 5 to 6mm following subcra-nial or frontofacial advancement may also beconsidered as a treatment goal. With

Fig. 9. Congruent midface hypoplasia seen in Crouzon syn


counterclockwise craniofacial rotation, activedistraction is continued until the palatal plane isnormalized (sella-nasion to palatal plane angle of7�, Fig. 12).14

Following distraction progress with serial lateralcephalograms is critical during the active phase,as incorrect or inadequate vectors and problemswith splint adaptation can be addressed. As dis-cussed earlier, incorrect vertical positioning ofthe distraction force in the Le Fort II or III segmentcan result in undesirable counterclockwise orclockwise occlusal plane rotations. Placement oftemporary anchorage devices in the midlinemandible and elastic traction during activationcan be helpful to address these specific vector is-sues. Orthodontic bone anchors are similarly use-ful adjuncts for vector control in Le Fort IIdistraction procedures as well as counterclock-wise maxillomandibular rotations.

POSTDISTRACTION ORTHODONTICTREATMENT

Following completion of active distraction, pa-tients will enter a consolidation phase (average8 weeks). Once formation of bony generate isconfirmed radiographically (most evident at thepterygomaxillary junction), the devices areremoved. Postsurgical orthodontic treatment is

drome can be managed with Le Fort III distraction.


Fig. 10. Differential midface hypoplasia seen in Apert syndrome is appropriately addressed with Le Fort II distrac-tion and zygomatic repositioning.


then undertaken. In many instances, postsurgicalorthodontic care for the patient following midfacedistraction is similar to nonsurgical orthodonticcare.

For patients undergoing midface distractionprocedures in the mixed dentition, it is paramountto monitor growth of the midface relative to the

Fig. 11. This patient with Crouzon syndrome presented wmalignant proptosis, supraorbital retrusion, midface hyporior cranial vault constriction and midface hypoplasia werecial distraction. Postoperatively, the facial proportionsPostoperative polysomnography demonstrated substantial


mandible, as well as to follow dental eruption.There is evidence that subcranial midface osteot-omies in younger patients results in disruptions inmaxillary molar development and eruption.10 Fam-ilies should be counseled regarding this possibilitypreoperatively, and molar development should becarefully monitored in mixed dentition patients

ith large calvarial defects, intracranial hypertension,plasia, and obstructive sleep apnea (AHI 67). The ante-addressed simultaneously with a monobloc frontofa-were improved, with adequate globe protection.improvement in sleep-disordered breathing (AHI 3.7).


Fig. 12. The clockwise rotation deformity seen in Treacher Collins syndrome is managed with synchronous coun-terclockwise rotation distraction of the maxillomandibular complex, accomplished via Le Fort II and bilateralinverted-L mandibular osteotomies. In this patient, construction of the zygomas with autologous cranial bonegraft was completed at the time of device removal. (From Hopper RA, Kapadia H, Susarla S, et al. Counterclock-wise craniofacial distraction osteogenesis for tracheostomy-dependent children with Treacher Collins syndrome.Plast Reconstr Surg. 2018;142(2):447–57; with permission.)

Fig. 13. Preoperative occlusion in a pa-tient with achondroplasia (top). Post-distraction occlusion following Le FortII osteotomy with zygomatic reposi-tioning (middle); the midface positionis overcorrected relative to themandible, with positive overjet at theincisors. At skeletal maturity, the pa-tient underwent Le Fort I and bilateralmandibular sagittal split osteotomiesfor correction of the residual dentoske-letal discrepancy (bottom). (From Hop-per RA, Kapadia H, Susarla SM. Le FortII Distraction With ZygomaticRepositioning: A Technique forDifferential Correction of MidfaceHypoplasia. J Oral Maxillofac Surg.2018 Sep;76(9):2002.e1–14; withpermission.)

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undergoing subcranial distraction procedures. Theavailable evidence demonstrates that although thedistracted midface does not significantly relapse,growth is unpredictable and many patients under-going subcranial midface advancement in themixed dentition may require definitive orthog-nathic surgery at skeletal maturity. In this context,the goals of subcranial advancement establishedpreoperatively are paramount. Anticipation of theneed for occlusal and lower midface correctionat skeletal maturity is necessary for appropriatetreatment planning and patient/family counseling(Fig. 13).5,21–23

SUMMARY

When properly planned and executed, subcranialadvancement at the Le Fort II-III levels (includingsegmental movements and synchronous maxillo-mandibular counterclockwise rotations) and fron-tofacial distraction can be used to correct a widearray of craniomaxillofacial deformities. Focusedattention on the specific morphologic characteris-tics of the patient, as well as an assessment ofgrowth, and specific goals for distraction end-points are necessary to ensure an optimaloutcome.

DISCLOSURE

Dr R.A. Hopper shares patent royalties with KLSMartin. The other authors have nothing to disclose.

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Surgical-Orthodontic Considerations in Subcranial and ... · Le Fort III osteotomy Le Fort II osteotomy Monobloc osteotomy Subcranial distraction ... Monobloc frontofacial distraction