Int. J. Oral Maxillofac. Surg. 2003; 32: 553–559doi:10.1054/ijom.2003.0423, available online at http://www.sciencedirect.com

Technical NoteDistraction Osteogenesis

Maxillary distraction using atrans-sinusal distractor:technical noteN. Nadjmi, R. Van Erum, J. Schoenaers, E. Schepers: Maxillary distraction using atrans-sinusal distractor: technical note. Int. J. Oral Maxillofac. Surg. 2003; 32:553–559. � 2003 International Association of Oral and Maxillofacial Surgeons.Published by Elsevier Ltd. All rights reserved.

Abstract. In this pilot study, the principle of distraction osteogenesis was used toadvance the midface of a boxer dog. A modified high Le Fort I-type osteotomywas performed. Following a latency period of 5 days the maxilla was distracted14 mm in 14 consecutive days at a rate of 1 mm per day. Ten weeks after thecompletion of the distraction, multiple biopsies were taken across the distractiongap. Histological observation showed bone deposition in the osteotomy sites. Softand hard tissue formation resulted in complete healing across the distraction gap.The maxillary sinus was used to accommodate the distraction device.Superimposition of the standardized lateral cephalograms taken at the end ofdistraction and 14 months after the removal of the distractors showed no sign ofrelapse in the achieved sagittal advancement of the maxilla. This small,intraoral–trans-sinusal placed distractor has a completely new conceptual design,and may be helpful in distraction of maxilla in children and adults with midfacialhypoplasia.

N. Nadjmi1, R. Van Erum2,J. Schoenaers3, E. Schepers4

1Department of Cranio-Maxillofacial Surgery,Eeuwfeestkliniek, Antwerp, Belgium;2Department of Orthodontics, CatholicUniversity of Leuven, Belgium; 3Department ofOral and Maxillofacial Surgery, CatholicUniversity of Leuven, Belgium; 4Department ofProsthodontic Dentistry, Catholic University ofLeuven, Belgium

Key words: distraction osteogenesis; midface;maxillary sinus; cleft lip and palate; bonetissue.

Accepted for publication 19 March 2003

Introduction

Maxillary distraction osteogenesis canfind its indication in severe Angle classIII malocclusions, and severe maxillaryhypoplasia among some cleft patientsand other craniofacial deformities.Attempts were made to treat thesemalocclusions through the use of maxil-lary protracting appliances and chincaps, with conflicting opinions about thetreatment results4,5. Several external dis-traction devices, such as the tractionmask of M & O-Mand the rigid external distraction systemof P & F, permit easydevice application and removal, andmultidirectional movement. But, thereverse headgear and rigid external dis-

0901-5027/03/000553+07 $30.00/0 � 2003 In

traction apparatus are cumbersome andhighly visible9,15. A low profile, intraoraldistraction device, used in an exper-imental study by W et al.17 wassuccessfully used for midface distractionat the Le Fort I level. However, thedistraction cylinder protruded throughthe buccal mucosa and had to bedelivered through a skin incision in thenasolabial fold area. In a clinical studyby K et al.7 four patients weretreated by high Le Fort I osteotomiesand insertion of a subcutaneous distrac-tion device, placed in the malar region.The range of the distraction was limited(7–14 mm) due to the distractor design,and the distraction rods led to injuries atthe angle of the mouth and swelling ofthe lips. Delaire masks had to be used to

ternational Association of Oral and Maxillofacial Surg

stabilize the results. An ideal distractorshould be easy to apply, easy to activate,and guarantee predictable results. Itshould not result in any physical orpsychosocial complaints, and shouldallow normal function during thedistraction and the retention period.

The aim of this experimental pilot-study is to evaluate the effectiveness ofa new maxillary distractor, an intraoral–trans-sinusal placed device.

Material and methods

Animal selection

Clearance of the study protocol wasobtained by the Ethical Committee ofthe Catholic University of Leuven,

eons. Published by Elsevier Ltd. All rights reserved

554 Nadjmi et al.

Belgium for performing the experimentaldistraction in a 2-year-old boxer dog.This dog fulfilled the requirements for agood experimental model: a maxillarysinus, deep enough to provide space forplacement of the distraction screw, ashort splanchnocranium (short snout)and an inherent hypoplastic midface,comparable to the class III malocclusionin humans.

Distractor design

The distractor was made out of threemain parts: two plates and a distractionscrew. The distraction screw was the axisof a joint formed by the lower plate,

which was connected to it and couldmove around it. All parts of the devicewere made out of a titanium alloy(Ti-6Al-4V). The device was fabricatedby Titamed�, Belgium. The upper platewas fixed cranial to the osteotomyline with two screws (Fig. 1). Only twoscrews per plate were used to see whetherthe minimal fixation of the plates wouldbe sufficient to withstand the forcesapplied during the distraction process.The distractor was fixed on the lateralaspect of the nasal wall and the distrac-tion screw, which was almost perpen-dicular to the frontal plane, entered themaxillary sinus through the anterior wallof the sinus. The other end of the dis-

traction screw (activation head) foundits way through the soft tissue coveringthe anterior wall of the maxillary sinus,and was hidden behind the upper lip.The activation head (AH) was hexag-onal, with a matching screwdriver. A 360degrees counter clockwise rotation of theAH gave a displacement of 0.5 mm.

Animal experiment

The boxer dog was put under generalanaesthesia. A modified Le Fort I typeosteotomy was then performed, andthe distraction devices were placedbilaterally (day one).

After a latency period of 5 days thedistraction started at a ratio of 1 mmper day during 14 consecutive days(distraction phase). Activation was per-formed under light sedation, usingThalamonal� and Pentothal�.

The distractors were removed undergeneral anaesthesia after another 10weeks (retention phase). During thesame session multiple bone biopsies weretaken at the site of distraction.

A standardized lateral cephalogramwas taken on day 1, day 5 (start ofdistraction), day 12, day 19 (end of dis-traction), day 33, day 47, day 61, day 75(end of retention), and 14 months afterremoval of the distractors. A cephalostatwas used to ensure the standardizationof the lateral cephalometric radiographs.A fixed distance of 74 cm betweenthe source (90 kV and 60 ms) and themiddle of the skull was maintained. Allcephalograms were taken under lightsedation.

Surgical technique

A 2-year-old boxer dog was pre-medicated with IV injection of 0.5 mlThalamonal� (fentanyl, 0.05 mg/ml+droperidol 2.5 mg/ml; Janssen Pharma-ceutics, Beerse, Belgium) and 0.5 mlatropine (atropine sulphate 0.5 mg/ml).Five hundred mg Augmentin� (SKBeecham) IV was given preoperatively.A daily maintenance dose of Augmentinwas given during latency and distractionperiod. The dog was placed on theoperating table in a supine position withhis head in slight extension. The animalwas inducted with IV injection of30 mg/kg Narcovet� (sodium pento-barbital 60 mg/ml; Apharmo, Arnhem,Nederland). An orotracheal tube wasplaced and anaesthesia maintained withEthrane� (enflurane 15 mg/ml; Abott,

Fig. 1. Trans-Sinusal-Maxillary-Distractor (TS-MD), with two fixing plates and the distractionscrew that makes an axis of a joint formed by the lower plate.

Amstelveen, Nederland). A throat pack

Fig. 2. Illustration of the high Le Fort I type osteotomy and the entry hole to the maxillarysinus.

Maxillary distraction using a trans-sinusal distractor 555

was placed, and the oral mucosa anddentition were rinsed with chlorhexidinedigluconate 1% in water.

First, the crowns of the lower canineswere lowered to the gingival level, andwere treated endodontically in order

to minimize the chance of interferenceduring the maxillary protrusion.

Local anaesthesia Xylocaine� (1%in 1/100 000 epinephrine) was injectedsubmucosally.

A Le Fort I type incision was madewith electrocautery. Care was taken notto damage the infraorbital nerve. Theincision was then carried down to thebone.

Next, a subperiosteal dissection wascarried out to expose the midface struc-tures. In order to free the posteriormaxillary wall from the skull base theorbital floor had to be osteotomized,because this part forms the orbital floorin dogs. Therefore a subperiosteal tunnelwas made from the most medial point ofthe inferior rim (medial to the infra-orbital nerve) over the orbital floortowards the corner made by the horizon-tal and the perpendicular lamina of thepalatinal bone. The posterior maxillawas separated from the rest of the skullvia a transpalatinal approach in contrastto the human anatomy where theposterior maxilla can easily be separatedvia an upper buccal sulcus incision. Amodified high Le Fort I type osteotomywas then performed. The cut startedfrom the osseous corner made by thehorizontal and perpendicular lamina ofthe palatinal bone (as described above),continued over the orbital floor andended 4-mm posterior to the infraorbitalrim. Then an osteotomy cut was madestarting midway from the zygomatico-alveolar crest to a point midway betweenthe infraorbital rim and the superiorborder of the infraorbital foramen. Thisosteotomy line was continued parallel tothe hard palate through the lateral nasalwall, approximately 1 cm cranial to thenasal floor.

A small hole with a diameter ofapproximately 4-mm was made in theanterior wall of the maxillary sinus onthe right side, through which the distrac-tion screw would enter the sinus. Thisopening was located at the most medialpoint of the anterior wall of the maxil-lary sinus and was part of the anteriorosteotomy line (Fig. 2). The maxilla wasslightly mobilized making sure there wasno interference between the maxilla andthe rest of cranium. At this stage thedistractor was fixed to the lateral nasalwall (Figs 3 and 4). The lower platemoves in the same direction as thedistraction vector and therefore is fixedto the lateral nasal wall at the lowerborder of the osteotomy line. Each platewas fixed to the underlying bone with

Fig. 3. Schematic diagram showing the position of TS-MD on the right maxilla and thedistraction screw inside the sinus cavity. Osteotomised maxilla; — — the maillary sinus

distractor; – – – distraction screw inside the sinus cavity.

two screws. The same procedure was

Fig. 4. TS-MD fixed on the right side. The distraction screw is located inside the maxillarysinus, while the upper plate of the device is buried behind the inferior orbital nerve.

556 Nadjmi et al.

performed at the contra-lateral side. Thedistractors were activated for 4-mm tomake sure there were no interferences,and then reversed.

The distractor on the right side wasopened for a few mm (before fixation ofthe lower plate) in order to be distin-guished on radiographs. An osteosyn-thesis screw (diameter 1.5 mm, length5 mm) was placed in the midline on thefrontal bone, as a landmark for thecephalometric analysis. Two smallclass-5 amalgam fillings were placed on

the upper molars on the left side, asadditional landmarks for cephalometricanalysis.

The distraction head was too short tobe exposed into the oral cavity (rightbehind the upper lip). Therefore a hardsilicon tube approximately 2 cm inlength and with a diameter that matchedthe head of the distraction screw waspulled over it and fixed with Ethilon 2/0to the surrounding periosteum, thusallowing for activation of the distractors.The intraoral incision was sutured with

Ethilon 2/0 (Fig. 5). Postoperative dietconsisted of soft food.

Removal of the distractors

The animal was put under general anaes-thesia following the same protocol asdescribed above. A small incision wasmade at the level of the distractor.A subperiosteal dissection was per-formed at the level of the distractedarea. Subsequently, the distractors wereremoved very easily. Multiple bonebiopsies were taken at the distractionsite.

Histological evaluation

At the time of distractor removal biop-sies were taken and immediately fixatedin a solution of one part formaldehyde(Merck, Darmstadt, Germany), neutral-ized with 50 g CaCO3/1, and two parts80% ethanol. The samples were dehy-drated in graded alcohols and embeddedin methylmethacrylate. Nondecalcifiedserial sections were prepared in asawing microtome (Leitz 1600, Wetzlar,Germany) and ground and polished to athickness of approximately 30 to 50 �m(Minimet�, Buehler Inc., Lake Bluff, IL,USA). Finally, the sections were stainedwith a combination of Stevenel’s blueand Von Gieson’s picrofuchsine for lightmicroscopical evaluation.

Results

Insertion of the trans-sinusal maxillarydistractor was easy. The monocorticalscrew fixation gave sufficient stabilityand the distraction devices were welltolerated by the animal. No signs ofinfection were observed. The animaltolerated the soft diet very well.

Although the expected linear increaseof the cephalometric points was sup-posed to be 14 mm, an average increaseof 8.7 mm was found. The superimposi-tion showed a downward tipping of themaxilla for the first five days of thedistraction period. A standard lateralcephalogram was taken 14 months afterremoval of the distractors. The super-imposition of this cephalogram with theone taken at the end of the retentionperiod showed no sign of relapse (Figs7–10).

Histological examination showed analmost completely filled distraction gapwith newly formed bone with a typicalwoven structure that could clearly

Fig. 5. White arrows show hard silicon tubes approximately 2 cm in length and with a diameterthat matched the head of the distraction screw. The distractors were activated intraorallythrough the silicone tube.

be distinguished from the bone at the

Fig. 6. The difference between the new and old bone is clear. In the newly formed bone islandsof active remodelling with osteoclasts and osteoblasts are visible.

Maxillary distraction using a trans-sinusal distractor 557

border of the gaps that had a maturelamellar nature.

Two types of ossification wereobserved. Most of the new bone wasformed by appositional bone growth.Within some areas, where the gap wasnot yet completely filled, the newlyformed bone was covered with a layerof osteoid tissue and a row of activeosteoblasts.

In other areas endochondral boneformation was observed; here the boneformation was preceded by cartilageformation.

Islands of active remodelling could beobserved in the newly formed bone, withosteoclasts lying in resorption lacunae

and at the other side active osteoblasts(Fig. 6).

Discussion

Distraction osteogenesis is of particularinterest in patients with midfacial hypo-plasia as they lack both bone and softtissue. The subcutaneous, intraoraldevices present several advantages overexternal distraction devices currentlyused, which are cumbersome, highly vis-ible, and potentially not well toleratedby patients17. The intraoral devices havecertain disadvantages. At present, theyare all unidirectional. This implicates aperfect preoperative vector planning.The removal of the devices must be

performed under general anaesthesia,and can be difficult7. This is due to thefact that the current devices are still toobulky, and are placed under the peri-osteum. The activation rods are either incontinuous contact with lips, causingpain and irritation, or have to bedelivered through the skin in thenasolabial region3,7,17.

In this study the distraction screw wasplaced inside the maxillary sinus ratherthan in the subperiosteal area The vol-ume of the sinus cavity provides enoughroom for positioning of the distractionscrew, which determines the vector ofdistraction. In this way a bulky andmovable part of the device is accommo-dated in an empty cavity, and does notinterfere with the surrounding soft tissueand periosteum.

Although the linear increase of thecephalometric points was expected to be14 mm, an average of only 8.7 mm wasfound. This could be explained bio-mechanically by the influence of severalfactors i.e. distractor design, distractorplacement, and the possible movementof the screws in the fixation plates.Secondly, the superimposition of thelateral cephalograms shows a clockwisetipping of the maxilla during the first 5days of the distraction period, which cancontribute to the difference between theexpected and the effective gain in sagittaldisplacement of the maxilla. Apparentlythe fixation of the distractor plates, eachwith only two screws did not providesufficient stability of the device to with-stand the forces applied during the initialdistraction process.

Histologically two types of ossifi-cation were observed in the distractiongap. Endochondral bone formation,which was preceded by cartilage for-mation, was observed in some areas.This can be due to instability of the bonesegments and the distraction rate, but itdoes not influence the final result8,12,15.

Islands of active remodelling couldbe observed in the newly formed bonetissue, with osteoblasts lying in resorp-tion lacunae and at the other sideactive osteoblasts (Fig. 6). These obser-vations are in accordance with otherstudies8,15,16.

Because of a potential communicationbetween the oral cavity and the maxil-lary sinus a strict protocol with anti-biotics was maintained during thedistraction period. B et al.1

showed that the insertion of implantswhere sinus or even nasal cavity pen-etration could not be avoided, was justi-

Fig. 7. Lateral cephalogram at the beginning of the distraction.

fied, as titanium screws penetrating the

Fig. 8. Lateral cephalogram at the end of the distraction.

558 Nadjmi et al.

bone of sinus or nasal cavity did notcause undesirable side effects1.

In this study no clinical or radiologicalsign of infection or fistula formationwere found. This distraction deviceprovided skeletal anchorage and relapsewas not seen up to 14 months post-distraction (Figs 7–10).

The potential advantages of this dis-tractor are as follows. The distractoris easy to place and is positionedintraorally. The distraction screw goesbackward into the sinus rather than for-ward into the lip, which would implicatethe transcutaneous delivery of the dis-traction barrels in the nasolabial foldsbilaterally17. It can serve as a retentiondevice and be left in place as long asnecessary. This is in contrast with dis-traction performed using extra-oraldevices or a facial mask with elasticforces. Other studies report on dentalanchorage for the fixation of the distrac-tion device2,10,13,14,16, but this resultedoften in a significant dento-alveolardisplacement.

Distraction can be achieved in hori-zontal, vertical, and sagittal planes,simply by changing the inclination of thedistraction screw. Correction of the mid-line can be done by distracting one sidemore than the other.

The clinical prototype was designedby N. Nadjmi in cooperation withMartin MedizinTechnik, Tuttlingen,Germany, and has successfully beenapplied in a clinical study for the treat-ment of 10 patients with moderate tosevere midfacial hypoplasia11. A detailedreport is in progress.

Acknowledgments. The authors acknowl-edge with thanks the kind assistance ofProf. Dr P. Simoens, Department ofMorphology, Faculty of VeterinaryMedicine, University of Ghent. K.Stalmans, Dr A. Verdonck, Departmentof Orthodontics, and Professor P.Lambrechts, Department of Endo-dontics of the Catholic University ofLeuven. Special thanks to Dr J.Defrancq, Craniofacial AssociationAntwerp, for his advise on the choice ofmaterial used to make the distractors.

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Fig. 9. Lateral cephalogram 14 months after removal of the distractors.

Fig. 10. Superimposition of the lateral cephalograms taken at well-defined time-intervals. ——At the start of the distraction; – – – at the end of distraction; · · · after 14 months.

Maxillary distraction using a trans-sinusal distractor 559

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Address:Nasser NadjmiDepartment of Cranio-Maxillofacial SurgeryEeuwfeestkliniekHarmoniestraat 68B-2018 AntwerpBelgiumTel: 0032(0)3 240.26.11Fax: 0032(0)3 238.04.89E-mail: drnadjmi@monica.be