Clinical Paper

Rconstructive Surgery

Int. J. Oral Maxillofac. Surg. 2010; 39: 573–579doi:10.1016/j.ijom.2010.03.021, available online at http://www.sciencedirect.com

Two-step transport-diskdistraction osteogenesis inreconstruction of mandibulardefect involving body and ramusJ. Chen, Y. Liu, F. Ping, S. Zhao, X. Xu, F. Yan: Two-step transport-disk distractionosteogenesis in reconstruction of mandibular defect involving body and ramus. Int. J.Oral Maxillofac. Surg. 2010; 39: 573–579. # 2010 International Association of Oraland Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Abstract. One-step transport-disk distraction osteogenesis (TDDO) is effective forrepairing segmental mandibular defects. The authors studied whether it waseffective for reconstructing angled large mandibular defects using a two-stepTDDO procedure in seven patients suffering from neoplasm. In the two-step TDDOprocedure, the first distraction (horizontal distraction) was initiated immediatelyafter mandibulectomy, aimed at restoring the mandibular body. It was followed bythe second distraction, which was obliquely vertical and aimed at restoring theheight of the ramus. The distraction rate was set at twice 0.4 mm/day. The treatmentlasted for 14–18 months. The horizontal distraction length ranged from 48 to55 mm, and the vertical one from 33 to 43 mm, with full ossification in thedistraction area. No obvious shift of mandible, malocclusion or mouth openinglimitation was observed. Patients had a regular diet and spoke clearly. In conclusion,the two-step TDDO is still an option for the reconstruction of large angledmandibular defects when patients are prudently selected, despite the long treatmentperiod required.

0901-5027/060573 + 07 $36.00/0 # 2010 International Association of Oral and Maxillofacial Surge

J. Chen1, Y. Liu1, F. Ping1,S. Zhao2, X. Xu1, F. Yan1

1Department of Oral and MaxillofacialSurgery, Second Affiliated Hospital, School ofMedicine, Zhejiang University, Hangzhou,P.R.China; 2Department of Oral andMaxillofacial Surgery, Affiliated Hospital ofStomatology, School of Medicine, ZhejiangUniversity, Hangzhou, P.R.China

Keywords: reconstruction; mandible; distrac-tion osteogenesis; transport disk.

Accepted for publication 23 March 2010Available online 28 April 2010

Large mandibular defects resulting fromtumor resection lead to severe aestheticand functional sequelae. The patient’spostoperative quality of life largelydepends on the quality of the mandibularreconstruction. Vascularized or non-vas-cularized bone grafting has been the main-stay of mandibular reconstructiontreatment because of its predictableeffect,7,12,15,16 but its use of autogenousbone and the donor site morbidities caused

by its harvesting encouraged the authors toseek an alternative1,10.

Distraction osteogenesis is often used tocorrect craniomaxillofacial bone malfor-mations20,21. Transport-disk distractionosteogenesis (TDDO) has been appliedclinically to reconstruct craniomaxillofa-cial bone defects resulting from tumorresection9. In this method, a bone segmentis osteotomized adjacent to the defect andthen distracted slowly across the defect so

that new bone forms in the continuouslywidening gap, eventually leading to recon-struction of the bone defect. The distractedbone segment is referred to as the transportdisk18. Constantino et al. carried out aseries of studies in dogs on the biomecha-nical properties of reconstruction of man-dibular defect with TDDO and concludedthat the bone regenerated by TDDO isstrong enough to resist the forces of mas-tication3,4. Since then, clinical cases of

ons. Published by Elsevier Ltd. All rights reserved.

574 Chen et al.

Fig. 1. Design of the mandibulectomy and the transport disk on a solid model of thepreoperative mandible.

mandublar reconstruction with TDDOhave been reported5,13,14,22.

Despite its success in reparing segmen-tal bone defects, it is impossible for asingle TDDO procedure to reconstruct amandibular defect that involves the body,angle and the whole ramus. There are twodifficulties: the defect size is beyond themaximal limitation of most internal dis-traction systems; and the angled shape cannot be formed with a single TDDO.

In the present study, this type of man-dibular defect was reconstructed success-fully with a double-step TDDO procedure,in which the first TDDO was horizontaldistraction and aimed at restoring the man-dibular body, and the second was verticaldistraction and aimed at reconstructing theheight of the ramus. The indications, lim-itations and noteworthy aspects of thismethod are described.

Patients and methods

Patients with a unilateral mandibulardefect involving the posterior part of thebody, the angle and the whole ramus werecandidates for this study. They wereinformed about the options for mandibularreconstruction, including traditional vas-cularized or non-vascularized bone graft-ing and the double-step TDDO. Thosepreferring the double-step TDDO methodwere involved in the present study. Thedouble-step TDDO method was applied in7 consecutive patients suffering frombenign neoplasm of the mandible. Thepatients’ clinical data are given in Table 1.

Ablative surgery and horizontal

distraction procedure

All patients underwent CT scanning pre-operatively. The scanning data were usedto manufacture a solid model using rapidprototyping techniques. Mandibulectomywas simulated and the horizontal distrac-

Table 1. Reconstruction of mandibular defect o

CaseSex/

Age (ys) DiagnosisDistractio

horizonta

1 F/18 Ossifying fibroma 552 M/22 Ameloblastoma 513 F/20 Ossifying fibroma 484 M/25 Odontogenic

keratocyst53

5 F/19 Ameloblastoma 506 F/33 Ameloblastoma 47

7 F/36 Ameloblastoma 43* since removal of distraction device for the

tion procedure (including size of the trans-port disk, the distraction orientation andlength; Figs. 1 and 2) was planned with thesolid model.

A sub- and retro-mandibular incisionwas made combined with an intra-oralincision under general anesthesia. The softtissues around the lesional mandible wereelevated. The elevation was performed inthe subperiosteal plane in an area wherethe periosteum was beyond a safe surgicalmargin. Otherwise, the periosteum had tobe sacrificed. Extensive elevation of thehealthy mandible should be avoided.Especially for the bone that was to bemade into the transport disk, elevationof the tissues on the medial side of thehealthy mandible had to be strictly pre-vented. Mandibulectomy was performedbeyond the safe surgical margin (0.5 cmfrom the lesion) and the lesional mandib-ular block was removed, including thewhole ramus, the angle and the posteriorpart of the body (Fig. 3).

f body and ramus with two-step TDDO in 7 pat

n length (mm) Bonequality

Max. insicalopening

(mm)Mid

shl vertical

37 Excellent 40 No41 Excellent 42 No40 Excellent 35 No42 Excellent 35 No

39 Excellent 35 No36 Excellent 37 No

35 Good 31 No

vertical distraction.

The intra-oral incision was sutured intwo layers; the oral mucosa and the sub-mucosal layer. A transport disk of about14x18 mm was osteotomized on themandibular stump. Special attentionwas paid to avoid lacerating the softtissues attaching to the medial side ofthe transport disk. The internal distrac-tion device (Cibei Med, Cixi, China) wasfixed to the transport disk and theremaining mandible (remaining basalbone), with the transport segment inclose contact with the basal bone(Fig. 4). The activation arm was sub-mandibularly placed and the extra-oralincision was sutured in layers. The dis-traction was started at the rate of twice0.4 mm per day after a latency period of7 days and ended when the expecteddistraction length was reached. The con-solidation period was continued for atleast 16 weeks, decided by the degree ofcalcification in the distraction gap on thepanoramic radiograph.

ients.

lineift Occlusion

Treatmentduration(month)

Follow-up(month)*

Good 18 27Good 17 21Good 16 13Mild anterioropen bite

16 11

Good 15 7Mild anterioropen bite

14 5

Good 14 2

Mandibular reconstruction with two-step TDDO 575

Fig. 2. Design of the distraction orientation and length of the horizontal distraction bysimulative distraction on the solid model.

Fig. 3. Intra-operative view: mandibulectomy with a Gigli saw.

Fig. 4. Placement of the distraction device for the horizontal distraction procedure.

Vertical distraction procedure

The vertical distraction procedure aimedto restore the height of the ramus. It wasapplied at the end of consolidation periodof the horizontal distraction procedure.The vertical distraction was also plannedon a solid model preoperatively (Fig. 5).Under general anesthesia, the extra-oralincision was reopened to expose the dis-tracted mandibular body and the horizon-tal distraction device (Fig. 6). Elevation ofthe soft tissues on the medial side wasavoided. After removal of the horizontaldistraction device, a transport disk ofapproximately 15�12 mm was cut. Thevertical distraction device was then placedand fixed (Fig. 7), with the distractionorientation set pointing to the glenoidfossa. The activation arm was transcuta-neously placed. The vertical distractionwas initiated after a 7 day latency periodand continued at a rate of twice 0.4 mmper day until the planned ramus height wasreached. A consolidation period then fol-lowed. The distraction device wasremoved after ossification of the distrac-tion gap.

Regular follow-up

Patients were followed-up periodically.The follow-up included panoramic radio-graphy, assessment of mastication andfacial symmetry, mouth opening, occlu-sion, speech, and recurrence of tumor. Thefunction of mastication was judged by thediet type (soft or regular diet). Facialsymmetry was categorized as symmetricalor unsymmetrical, judged by the doctors’observation. It was also reflected by themandibular midline (shift or no shift).Mouth opening was judged by maximalincisal opening. Anterior or lateral openbite was judged to evaluate occlusion.Speech was classified as clear or unclearby the patients’ pronunciation.

Results

Two-step distraction TDDO treatmentwas completed in all patients. The distrac-tion length ranged from 43 to 55 mmhorizontally and from 35 to 42 mm verti-cally (Table 1). The treatment periodlasted for 14–18 months, longer thanexpected. It was mainly caused by thepatients’ failure to return for visits in time.A consolidation period of 16 weeks wasenough, judged by the high-degree ossifi-cation on the radiograph (Fig. 8) and theintra-operative view of the new bone(Fig. 9). In the whole treatment period,no distraction device failure or intra-oral

576 Chen et al.

Fig. 6. Intra-operative view: new bone generated by the horizontal distraction was fully ossifiedwhen the distraction device from the first step was removed.

Fig. 5. Design of the vertical distraction on the solid model. The distraction orientation was setpointing to the glenoid fossa and the distraction length was filled with wax.

Fig. 7. Intra-operative view: placement of the distraction device for the vertical distractionprocedure.

exposure was found. The incision healeduneventfully, without mucosal dehis-cence. Pain and obvious discomfortoccurred at the end of distraction in twopatients, although it was tolerable.Obvious scars were left on the skin wherethe activation arm pierced through, whichwere trimmed later during removal of thedistraction device.

The patients have been followed up for2–27 months (Table 1). In all 7 patients,neither tumor recurrence nor mandibularfracture was observed. Limitation ofmouth opening was observed in twopatients at the end of the treatment, withmaximum incisal opening of 21 and23 mm. All patients demonstrated satis-factory mouth opening through exercise,with maximum incisal opening from 31 to42 mm (Table 1).

The postoperative appearance of allpatients was roughly symmetrical.Obvious lateral shift of the mandiblewas not found (Fig. 10). The remainingteeth maintained the preoperative occlu-sion, except in two patients who demon-strated slight anterior open bite andneeded maxillomandibular elastic reduc-tion to improve the occlusion (Table 1).The patients could pronounce clearly aftera period of exercise. Three patients hadreceived removable partial denture reha-bilitation. All patients had a regular dietwith the remaining teeth and the partialdenture.

Discussion

Owing to the studies by Constantinoet al.3,4, TDDO is now an option forreconstruction of segmental mandibulardefects. It is difficult for a single-stepTDDO to reconstruct a mandibular defectinvolving body, angle and the wholeramus, which is large and angled. For thistype of mandibular defect, the large size isa problem, while the angled shape is abigger challenge for restoration. Theauthors attempted to resolve these diffi-culties using the double-step TDDO in thepresent study. The posterior part of thebody and angle, which was roughly hor-izontal, was reconstructed through the firstdistraction. The second distraction wasapplied to restore the obliquely verticalramus. The results show that the shape andfunctions of the mandible reconstructedwith this technique were satisfactory(Fig. 11).

It is crucial for the transport disk toacquire enough nutrition and oxygen tomaintain vitality, which is a prerequisitefor the success of TDDO8,9. In this double-step TDDO, the transport disk could

Mandibular reconstruction with two-step TDDO 577

Fig. 8. Panoramic radiography: the distraction gaps of both the horizontal and the verticaldistraction were filled with highly ossified new bone at the end of treatment.

Fig. 9. Intra-operative view: the whole distraction gap was filled with high-quality new bonewhen the vertical distraction device was removed.

Fig. 10. Intra-oral view: occlusion was good and the midline of the mandible did not shift at theend of treatment.

obtain nutrition and oxygen only from thesurrounding tissues. Therefore, elevationof the soft tissues on the medial side of thetransport disk should be prevented. Peri-osteum beyond a safe surgical marginshould be preserved during mandibulect-

omy to maintain a rich blood supply andosteogenicity of the defect area, a condi-tion conducive to bone regeneration18.Radiotherapy is generally considered tobe an adverse factor for bone regeneration,causing damage to the vasculature and

cells, therefore it is not recommended toapply this two-step TDDO procedure topatients who have undergone radiotherapyuntil more data is obtained from animalexperiments.

An internal distraction system wasexclusively applied in this study, becauseinternal distraction systems produce fewerscars and are more acceptable to patientsthan external distraction systems11. Theactivation arm was placed submandibu-larly rather than intra-orally. Althoughprobably leading to skin scars, it madethe daily distraction much easier to manip-ulate and reduced infection or dehiscenceof oral mucosa9. The submandibular scarscould be trimmed when the distractiondevice was removed.

Three aspects have to be consideredwhen planning and performing verticaldistraction. First, is the size of the trans-port disk. The bone from which the trans-port disk is created is generally limited inheight, so a balance has to be struckbetween the size of the transport diskand the height of the remaining basal bone,so that both the two parts are vital andstrong enough to resist the force producedby distraction. Second, the distractionorientation has to be set pointing to theglenoid fossa, to restore the ramus-con-dyle unit, which is important for normalocclusion6,19. Third, the distraction lengthhas to be determined. In the authors’experience, a gap of approximately10 mm between the glenoid fossa andthe transport disk should be maintainedwhen treatment is accomplished, workingas gap arthroplasty to reduce ankylosis2,17.It seldom led to apparent ramus heightinsufficiency or shift of the mandible, aswas demonstrated in this study.

Gonzalez-Garcia et al. also applied two-step TDDO to mandibular reconstruction8.Their cases were different from the presentones. Their patients had the condylereserved, which made it easy to set thevertical distraction orientation. The dis-traction orientation of the second stepwas adjusted 20 degree above the firstone in their study, with no intention torestore the angled shape symmetrical tothe contralateral side. In contrast, the sym-metry of the bilateral mandibular anglewas intentionally restored in this study,with the assistance of preoperative simu-lation on the solid models. This shouldimprove facial symmetry.

Autogenous vascularized or non-vascu-larized bone grafting remains the mainstayfor mandibular reconstruction because itensures satisfactory mandibular functionand profile after reconstruction, especiallywhen combined with prefabricated recon-

578 Chen et al.

Fig. 11. 3D CT scanning: the reconstructed left mandible was roughly symmetrical to thecontralateral side at the end of treatment.

struction plates. Vascularized bone graft-ing can also be used to reconstruct themandible in patients who have undergoneradiotherapy. The morbidities caused byharvesting bone flaps, which can be severeat the initial stage, has been reduced to alow level following improvements ininstruments, the development of micro-vascular anatomy, and modification ofthe bone harvesting techniques. In con-trast, it is difficult for TDDO to ensuresatisfactory postoperative mandibularshape and occlusion. The TDDO techni-que generally requires a long period andseveral operations to accomplish recon-struction. This weakness is importantwhen multi-stage TDDO is applied toreconstruct a large mandibular defect.As was demonstrated in this study, thetreatment period ranged from 14 to 18months. The long treatment period hindersits wide application.

In spite of its weaknesses, the two-stepTDDO technique avoids sacrifice of auto-genous bone and the donor site morbiditiescaused by bone (flap) harvesting. This isimportant for adolescents in whom boneharvesting may influence the bone growthof donor sites, or for patients who have aphobia about bone harvesting, or whenautogenous bone harvesting is contraindi-cated. As was shown for the first time inthis study, the double-step TDDO techni-que can achieve a satisfactory shape and

function in the reconstruction of angledmandibular defect involving ramus, angleand body. This technique is an option forthe reconstruction of large angled man-dibular defects when patients are pru-dently selected.

Funding

This study was supported by Technologi-cal Project Fund of Zhejiang Province ofChina (No. 2007C33012).

Competing Interests

None declared

Ethical Approval

Not required

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Address:Yanming Liu, Department of Oral and

Maxillofacial SurgerySecond Affiliated HospitalZhejiang University School of Medicine88 Jiefang Rd.Hangzhou310009 P.R.ChinaTel.: +86 571 87783513fax: +86 571 87767078E-mail: liuyanming_cn@yahoo.com