Evaluation of canting correction of the maxillary transverse occlusal plane and change of the lip canting in Class III two-jaw orthognathic surgery

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1 Originl Article Evlution of cnting correction of the mxillry trnsverse occlusl plne nd chnge of the lip cnting in Clss III two-jw orthognthic surgery Seung-Je Kim ; Jin-Young Choi b ; Seung-Hk Bek c ABSTRACT Objective: To compre the effect of cnting correction in nterior mxillry trnsverse occlusl plnes (AMTOP) nd posterior mxillry trnsverse occlusl plnes (PMTOP) on the chnge of lip cnting (LC) in two-jw surgery (TJS) cses. Mterils nd Methods: The smples consisted of eight young dult ptients (three mles nd five femles, men ge yers) who hd skeletl Clss III mlocclusion (CIII), fcil symmetry (FA), nd LC nd who underwent TJS. Two-dimensionl lterl nd posteronterior cephlogrms nd three-dimensionl fcil scnning tken 1 week before (T1) nd 6 months fter TJS (T2) were combined using the Morpheus 3D progrm. Six liner nd ngulr vribles were mesured nd sttisticlly nlyzed. Results: When compring the vlues of the liner nd ngulr vribles t the T1 nd T2 stges there ws significnt cnting correction of AMTOP (1.7 mm vs 20.3 mm; 3.0u vs 0.1u), PMTOP (3.5 mm vs 0.1 mm, 3.3u vs 20.1u), nd LC (3.0 mm vs 0.7 mm, 4.7u vs 2.1u) (ll P,.05). Although the ngulr chnge rtios (DLC/DAMTOP nd DLC/DPMTOP) did not exhibit significnt difference (0.99 vs 0.83), the liner chnge rtio of DLC/DAMTOP ws significntly higher thn tht of DLC/DPMTOP (1.67 vs 0.74, P,.05). The ngulr chnge of DLC showed significnt correltion with DAMTOP (r ; P,.05). However, the liner chnge of DLC ws significntly correlted with both the ngulr nd liner chnges of DAMTOP (r nd 0.66; both P,.05). Therefore, the mount of LC chnge ws more relted to the cnting correction of AMTOP thn to tht of PMTOP. Conclusion: In TJS cses with CIII, FA, nd LC, the mount of cnting correction of the AMTOP should be considered to predict the ctul LC chnge. (Angle Orthod. 2012;82: ) KEY WORDS: Clss III mlocclusion; Fcil symmetry; Two-jw surgery; Lip cnting; Mxillry trnsverse occlusl plne cnting INTRODUCTION Grdute Student (MSD), School of Dentistry, Seoul Ntionl University, Seoul, South Kore. b Professor nd Deprtment Chir, Deprtment of Orl nd Mxillofcil Surgery, School of Dentistry, Dentl Reserch Institute, Seoul Ntionl University, Seoul, South Kore. c Professor nd Deprtment Chir, Deprtment of Orthodontics, School of Dentistry, Dentl Reserch Institute, Seoul Ntionl University, Seoul, South Kore. Corresponding uthor: Dr Seung-Hk Bek, Professor nd Deprtment Chir, Deprtment of Orthodontics, School of Dentistry, Dentl Reserch Institute, Seoul Ntionl University, Yeonkun-dong #28, Jongro-ku, Seoul, South Kore (e-mil: drwhite@unitel.co.kr). Accepted: Mrch Submitted: Jnury Published Online: April 19, 2012 G 2012 by The EH Angle Eduction nd Reserch Foundtion, Inc. Recently the number of orthodontic ptients who desire to correct fcil symmetry nd lip cnting (LC) hs incresed. 1 When setting the surgicl tretment objectives for orthognthic surgery, the prediction of soft tissue chnge is difficult nd inccurte, especilly in the frontl plne. Mild to moderte LC cn remin even fter correction of skeletl symmetry by two-jw surgery. 2,3 Since soft tissue symmetry is dictted by the underlying skeletodentl structures nd muscles, LC cn be useful tool for the dignosis nd tretment plnning of subjects with fcil symmetry despite discrepncy between the cnting correction of the mxillry trnsverse occlusl plne (MTOP) nd chnge of LC. 4 Previous studies 3,5,6 hve nlyzed the pttern nd mount of cnting correction of MTOP nd chnges of LC before nd fter orthognthic 1092 DOI: /

2 CANTING CORRECTION IN CLASS III TWO-JAW ORTHOGNATHIC SURGERY 1093 surgery using two-dimensionl posteronterior (2D PA) cephlogrms nd frontl photogrphs. However, it is difficult to obtin proper ccurcy becuse of the chllenges in mtching the PA cephlogrm nd frontl photogrph with 1:1 rtio nd in reproducing the sme hed posture while tking the PA cephlogrm nd frontl photogrph. Even though three-dimensionl computed tomogrphy (3D CT) cn be nother option for the evlution of cnting, the low resolution of CTs (1.0-mm slice cut) cn produce errors in mesuring the cnting correction of MTOP nd the chnges of LC. Therefore, 3D fcil scnning cn be regrded s useful nd ccurte method with which to mesure soft tissue chnge. Lim et l. 7 nd Kim et l. 8 evluted soft tissue chnge in 3D fcil scnning imges ccording to the skeletl movement of lterl cephlogrms fter one-jw orthognthic surgery (mndibulr setbck only) in cses involving skeletl Clss III mlocclusion. Recently, new technology to superimpose the 2D lterl nd PA cephlogrms with the 3D fcil scnning imge (Morpheus 3D progrm, version 2.0; Morpheus, Seoul, Kore) hs been developed to overcome disdvntges, including enlrgement of the imge nd hed posture in the 2D biplnr cephlogrms nd low resolution of the hrd nd soft tissues in the 3D CT. The MTOP cn be divided into two prts: nterior nd posterior. The posterior MTOP (PMTOP), which is estblished by connecting the mxillry first molrs, hs been used in most of the previous studies. 3,6,9 The nterior MTOP (AMTOP) is estblished by connecting the mxillry cnines t both sides. Since the sgittl distnce from the mxillry cnine to the mouth corner (commissure) is reltively shorter thn the sgittl distnce from the mxillry first molr to the mouth corner, it is required tht one evlute the reltionship between the cnting correction of AMTOP nd the chnge of LC. Therefore, the purposes of this study were to compre the effect of cnting correction in AMTOP nd PMTOP on the chnge of LC in two-jw orthognthic surgery cses with skeletl Clss III mlocclusion, fcil symmetry, nd LC. The null hypothesis ws tht cnting correction of AMTOP nd PMTOP did not exhibit ny significnt difference in terms of chnge of LC in cses involving two-jw orthognthic surgery. MATERIALS AND METHODS The smples consisted of eight young dult ptients (three mles nd five femles; men ge yers) who hd skeletl Clss III mlocclusion, fcil symmetry, nd LC nd who underwent two-jw Tble 1. Cephlometric Anlysis of the Ptients Men SD SNA, u SNB, u ANB, u FMA, u Chin devition, mm SD indictes stndrd devition. surgery (LeFort I osteotomy for the mxill nd bilterl sgittl split rmus osteotomy for the mndible) t the Deprtment of Orl nd Mxillofcil Surgery, Seoul Ntionl University Dentl Hospitl in Seoul, Kore. The cephlometric dt for the smples before two-jw surgery re presented in Tble 1. Pre- nd postopertive orthodontic tretments were performed by single orthodontist nd two-jw surgery by single surgeon. The study protocol ws pproved by the institutionl review bord t the Seoul Ntionl University Dentl Hospitl (SNUDH IRB CRI-11028). 2D lterl nd PA cephlogrms nd 3D fcil scnning were conducted 1 week before (T1) nd 6 months fter two-jw surgery (T2). The Morpheus 3D progrm (version 2.0) ws used to orthogonlly overlp the 2D lterl cephlogrm with the 2D PA cephlogrm. The progrm ws then used to combine the 3D fcil scnning imge with the 2D biplnr cephlogrms in the 3D coordintes (Figure 1). These procedures cn correct the mgnifiction of the 2D rdiogrphs by mtching the ctul liner distnce between two reference points (pronsle nd soft tissue pogonion) in the 3D fcil scnning imge nd cn llow us to obtin ctul liner mesurements of the corrected 2D cephlogrms nd 3D fcil scnning. Choi et l. 10 reported superimposition technique using the 2D biplnr cephlogrms nd the 3D virtul dentl models (2.5D superimposition technique) nd its ccurcy test result. They 10 concluded tht the 2.5D-technqiue cn be regrded s n effective nd efficient lterntive to the 3D technique. The definitions for the reference plnes, lndmrks, nd liner nd ngulr vribles for mesuring the LC, AMTOP, nd PMTOP re enumerted in Figures 1 through 4, respectively. The AMTOP nd PMTOP of 2D PA cephlogrms nd the LC of 3D fcil scnning imges were mesured by single opertor using the Morpheus 3D progrm. All liner nd ngulr vribles t the T1 nd T2 stges were mesured in units of 0.01u nd 0.01 mm, respectively. All vribles from three rndomly selected subjects were ressessed t 2-week intervls by the sme opertor. The differences tht were clculted using Dhlburg s formul 11 rnged from 0.12 mm to 0.16 mm for the liner mesurements nd from 0.06u to 0.13u

3 1094 KIM, CHOI, BAEK Figure 1. A new technology to superimpose the two-dimensionl (2D) lterl nd posteronterior (PA) cephlogrms with three-dimensionl (3D) fcil scnning imge using the Morpheus 3D progrm (version 2.0). The 3D coordintes consisted of three reference plnes: the horizontl plne, the plne constructed with the right orbitle, the right porion, nd the left porion (Frnkfort horizontl [FH] plne); the coronl plne, the plne constructed with the right porion nd the left porion perpendiculr to the FH plne; nd the sgittl plne, the plne constructed with the nsion, perpendiculr to the FH nd coronl plnes. for the ngulr mesurements. Therefore, the first set of mesurements ws used for this study. The smple size determintion ws performed by power nlysis using the Smple Size Determintion Progrm (version 2.0.1; Seoul Ntionl University Dentl Hospitl, Registrtion No , Seoul, Kore). The Wilcoxon signed rnk test, Mnn-Whitney U-test, nd Person correltion nlysis were performed for sttisticl purposes. RESULTS In compring the vlues of the liner nd ngulr vribles t the T1 nd T2 stges, there were significnt cnting corrections for AMTOP (1.7 mm vs 20.3 mm; 3.0u vs 0.1u, ll P,.05), PMTOP (3.5 mm vs 0.1 mm, 3.3u vs 20.1u, ll P,.05), nd LC (3.0 mm vs 0.7 mm, 4.7u vs 2.1u, ll P,.05) (Tble 2). The mounts of ngulr nd liner cnting correction in AMTOP (DAMTOP) were 3.0u nd 1.9 mm; those in PMTOP (DPMTOP) were 3.4u nd 3.4 mm; nd those in LC chnge (DLC) were 2.6u nd 2.4 mm, respectively (Tble 2). Although the ngulr chnge rtios (DLC/DAMTOP nd DLC/DPMTOP) did not show significnt difference (0.99 vs 0.83, P..05), the liner chnge rtio of DLC/DAMTOP ws significntly higher thn the liner chnge rtio of DLC/DPMTOP (1.67 vs 0.74, P,.05; Tble 3). A significnt correltion ws found between the ngulr cnting chnge of LC nd AMTOP (correltion coefficient [r 2 ] , P,.05; Tble 4). The liner cnting chnge of LC ws significntly correlted with the ngulr cnting chnge of AMTOP (r , P,.05; Tble 4) nd the liner cnting chnge of AMTOP (r , P,.05; Tble 4). There ws high Person correltion coefficient for the liner chnge between DPMTOP nd DAMTOP (0.69, P,.05; Tble 5). Therefore, the mount of LC chnge ws more relted to the cnting correction of the AMTOP thn to tht of the PMTOP. DISCUSSION Figure 2. Soft tissue nd skeletodentl lndmrks used in this study: (1) the center of the pupil (P); (2) the outermost point of the mouth (Ch); (3) the outer edge point of the fronto-zygomtic suture (FZ); (4) the midportion of the brcket nd wire of the mxillry cnine (C); (5) the midportion of the brcket nd wire of the mxillry first molr (U6). Jung et l. 12 reported tht devition of the philtrum nd mouth corner ws significntly corrected fter onejw orthognthic surgery (mndibulr setbck only) in cses with skeletl Clss III mlocclusion nd fcil symmetry using 3D CT nlysis. Lim et l. 7 found tht 3D soft tissue chnges in Clss III ptients fter

4 CANTING CORRECTION IN CLASS III TWO-JAW ORTHOGNATHIC SURGERY 1095 Figure 3. Liner vribles: (1) fronto-zygomtic suture (FZ) mxillry cnine (C) distnce (mm, the perpendiculr distnce between the midportion of the brcket nd wire of the C nd the inter-fz line); (2) FZ mxillry first molr (U6) distnce (mm, the perpendiculr distnce between the midportion of the brcket nd wire of the U6 nd the inter-fz line); (3) P-Ch distnce (mm, the perpendiculr distnce between the most outer point of the mouth corner [Ch] nd the interpupillry line). mndibulr setbck surgery exhibited incresed grdients from the upper lip nd lower lip to the chin s well s from the stomodium to the mouth corner. Kim et l. 8 suggested tht there were significnt increses in the upper lip length nd decreses in the lower lip length in the lrge setbck, hypodivergent, nd genioplsty groups in Clss III cses with mndibulr setbck surgery. However, they did not include twojw orthognthic surgery cses in the smples. Therefore, it is necessry to investigte the effects of cnting correction of MTOP on the chnge of LC by two-jw orthognthic surgery. LC is produced by the verticl height difference in the mouth commissures of the right nd left sides. The verticl position of the mouth commissure is determined by two fctors: the verticl proportion of the underlying skeletodentl tissue nd the blnce between the upwrd pull from the zygomticus mjor nd levtor nguli oris muscles nd the downwrd pull of the depressor nguli oris muscle. 13,14 Therefore, the position of the mxillry cnine, which is locted more djcent to the joining position of these muscles with the orbiculris oris muscle thn with the mxillry first molr, cn be regrded s hving greter correltion with LC thn does the position of the mxillry first molr. The findings tht the ngulr chnge rtio of DLC/ DAMTOP showed higher vlue thn tht of DLC/ DPMTOP (0.99 vs 0.83; Tble 3) nd tht the liner chnge rtio of DLC/DAMTOP ws significntly higher thn tht of DLC/DPMTOP (1.67 vs 0.74, P,.05; Tble 3) indicte tht there my be possibility tht Figure 4. Angulr vribles: (1) fronto-zygomtic suture (FZ) mxillry cnine (C) (u, nterior mxillry trnsverse occlusl plne cnting [AMTOPC] ngle, the ngle between the inter-fz line nd the inter-c line); (2) FZ mxillry first molr (U6) (u, posterior mxillry trnsverse occlusl plne cnting [PMTOPC] ngle, the ngle between the inter-fz line nd the inter-u6 line; (3) P mouth corner (Ch) (u, Lip cnting [LC] ngle, the ngle between the interpupillry line nd the inter-ch line).

5 1096 KIM, CHOI, BAEK Tble 2. Chnges of the Liner nd Angulr Vribles Between the T1 nd T2 Stges T1 Stge T2 Stge Amount of Chnge Vribles Men SD Men SD P Vlue Men SD Liner Liner cnting of AMTOP, FZ-C, mm Devited side Opposite side Difference * Liner cning of PMTOP, FZ-U6, mm Devited side Opposite side * Difference * Liner LC, P-Ch, mm Devited side Opposite side Difference * Angulr Angulr cnting of AMTOP, FZ-C, u * Angulr cnting of PMTOP, FZ-U6, u * Angulr LC, P-Ch, u * Wilcoxon signed rnk test ws performed. T1 indictes 1 week before two-jw orthognthic surgery; T2, 6 months fter two-jw orthognthic surgery; SD, stndrd devition; * P,.05; AMTOP, nterior mxillry trnsverse occlusl plne; PMTOP, posterior mxillry trnsverse occlusl plne; LC, lip cnting; FZ-C (mm), the perpendiculr distnce between the midportion of the brcket nd wire of the mxillry cnine (C) nd the inter-fz line; FZ-U6 (mm), the perpendiculr distnce between the midportion of the brcket nd wire of the mxillry first molr (U6) nd the inter-fz line; P-Ch (mm), the perpendiculr distnce between the most outer point of the mouth corner (Ch) nd the interpupillry line; FZ-C (u), the ngle between the inter-fz line nd the inter-c line; FZ-U6 (u), the ngle between the inter-fz line nd the inter-u6 line; P-Ch (u), the ngle between the interpupillry line nd the inter-ch line; Amount of chnge, the vlue of the T1 stge minus the vlue of the T2 stge; nd Difference, the vlue of the nonffected side minus the vlue of the ffected side. the cnting correction of AMTOP hs n overcorrection tendency for the chnge of LC, while the cnting correction of PMTOP hs n undercorrection tendency for the chnge of LC. Kim et l. 3 investigted the effects of cnting correction of MTOP on the chnge of LC by two-jw surgery using 2D PA cephlogrms nd frontl photogrphs. According to the results of Kim et l., 3 the rtios of DLC/DPMTOP were 51.5% in the ngulr mesurement nd 48.8% in the liner mesurement. However, the present study exhibited higher vlues of DLC/DPMTOP (83% in the ngulr mesurement nd Tble 3. Rtio of the Lip Cnting Chnge to the Mxillry Trnsverse Occlusl Plne Cnting Correction Rtio Vribles Men SD P Vlue Angulr DLC/DAMTOP DLC/DPMTOP Liner DLC/DAMTOP * DLC/DPMTOP Mnn-Whitney U-test ws performed. SD indictes stndrd devition; * P,.05; D, the mount of chnge between the T1 (1 week before the two-jw orthognthic surgery) nd T2 (6 months fter the two-jw orthognthic surgery) stges; AMTOPC, nterior mxillry trnsverse occlusl plne cnting; PMTOPC, posterior mxillry trnsverse occlusl plne cnting; LC, lip cnting; DLC/ DAMTOP, rtio of LC chnge to the AMTOP cnting correction; nd DLC/DPMTOP, rtio of LC chnge to the PMTOP cnting correction. 74% in the liner mesurement; Tble 3). This difference my be dependent on the surgicl technique, surgeon, or smples. In ddition, it seemed to be cused by DAMTOP rther thn DPMTOP itself. This study showed high Person correltion coefficient for the liner chnge between DPMTOP nd DAMTOP (0.69, P,.05; Tble 5). As result of this high correltion, reltively higher rtios of DLC/ DPMTOP were exhibited (Tble 3). In this study, the Person correltion coefficient between DLC nd DPMTOP for liner chnge ws 0.62 nd mrginlly insignificnt (P ; Tble 4), nd tht for the ngulr chnge ws 0.33 nd not significnt (P..05; Tble 4). However, Kim et l. 3 reported tht the Person correltion coefficients Tble 4. Person Correltion Coefficient Vlues Among the Amount of Lip Cnting Chnge (DLC) nd the Degree of the Cnting Correction of the Anterior nd Posterior Mxillry Trnsverse Occlusl Plnes (DAMTOP nd DPMTOP, Respectively) Vribles DLC, u P Vlue DLC, mm P Vlue DAMTOP, u * * DAMTOP, mm * DPMTOP, u DPMTOP, mm Person correltion nlysis ws performed. D indictes the mount of chnge between the T1 (1 week before two-jw orthognthic surgery) nd T2 (6 months fter two-jw orthognthic surgery) stges. * P,.05.

6 CANTING CORRECTION IN CLASS III TWO-JAW ORTHOGNATHIC SURGERY 1097 Tble 5. Person Correltion Coefficient Vlues Between the Degree of the Cnting Correction of the Anterior nd Posterior Mxillry Trnsverse Occlusl Plnes (AMTOP nd PMTOP, Respectively) Vribles DAMTOP, u P Vlue DAMTOP, mm P Vlue DPMTOP, u DPMTOP, mm * Person correltion nlysis ws performed. D indictes the mount of chnge between the T1 (1 week before two-jw orthognthic surgery) nd T2 (6 months fter two-jw orthognthic surgery) stges. * P,.05. between DLC nd DPMTOP were 0.87 for the ngulr mesurement nd 0.89 for the liner mesurement (P,.01, both). These vlues were higher thn expected. Since the distnce between the mxillry first molr nd the mouth corner is reltively longer thn the distnce between the mxillry cnine nd the mouth corner, it seems logicl to hve reltively lower Person correltion coefficient vlues thn hve been reported by Kim et l. (DLC nd DPMTOP for the liner chnge in the present study vs 0.87 in Kim et l.; ngulr chnge in the present study vs 0.89 in Kim et l.). 3 Although Kim et l. 3 did not mesure the chnges in AMTOP, the Person correltion coefficients between DLC nd DAMTOP for the liner nd ngulr chnges were 0.66 nd 0.64, respectively, in the present study (both P,.05; Tble 4). In ddition, the ngulr chnge of AMTOP ws significntly correlted with the liner chnge of LC (correltion coefficient , P,.05; Tble 4). Therefore, these findings lso support the concept tht LC chnge ws more relted to AMTOP cnting correction thn to PMTOP cnting correction. However, this study hs some limittions in terms of smple size nd stndrdiztion of the mount or type of the surgicl movement of the osteotomized mxillry bony segments. Although the sme surgicl methods (LeFort I nd BSSRO) were used in cses with skeletl Clss III mlocclusion, fcil symmetry, nd LC, there my be diverse nteroposterior, trnsverse, nd verticl movements of the osteotomized mxillry bony segments. To overcome these limittions, further studies with stndrdized protocol from multi-centers will be required to investigte the reltionships ssocited with cnting correction mong AMTOP, PMTOP, nd LC. CONCLUSIONS N The null hypothesis ws rejected. N In two-jw orthognthic surgery cses involving skeletl Clss III mlocclusion, fcil symmetry, nd LC, the mount of cnting correction of the AMTOP, in ddition to tht of the PMTOP, should be considered to predict the ctul LC chnge. REFERENCES 1. Im DH, Kim TW, Nhm DS, Chng YI. Current trends in orthodontic ptients in Seoul Ntionl University Dentl Hospitl. Koren J Orthod. 2003;33: Choi JY, Choi JP, Lee YK, Bek SH. Simultneous correction of hrd- nd soft-tissue fcil symmetry: combintion of orthognthic surgery nd fce lift using resorbble fixtion device. J Crniofc Surg. 2010;21: Kim YH, Jeon J, Rhee JT, Hong J. Chnge of lip cnt fter bimxillry orthognthic surgery. J Orl Mxillofc Surg. 2010;68: Msuok N, Momoi Y, Ariji Y, Nw H, Murmtsu A, Goto S, Ariji E. Cn cephlometric indices nd subjective evlution be consistent for fcil symmetry? Angle Orthod. 2005;75: Hwng HS, Min YS, Lee SC, Sun MK, Lim HS. Chnge of lip-line cnt fter 1-jw orthognthic surgery in ptients with mndibulr symmetry. Am J Orthod Dentofcil Orthop. 2009;136: Ko EW, Hung CS, Chen YR. Chrcteristics nd corrective outcome of fce symmetry by orthognthic surgery. J Orl Mxillofc Surg. 2009;67: Lim YK, Chu EH, Lee DY, Yng IH, Bek SH. Threedimensionl evlution of soft tissue chnge grdients fter mndibulr setbck surgery in skeletl Clss III mlocclusion. Angle Orthod. 2010;80: Kim M, Lee DY, Lim YK, Bek SH. Three-dimensionl evlution of soft tissue chnges fter mndibulr setbck surgery in clss III mlocclusion ptients ccording to extent of mndibulr setbck, verticl skeletl pttern, nd genioplsty. Orl Surg Orl Med Orl Pthol Orl Rdiol Endod. 2010;109:e20 e Pdw BL, Kiser MO, Kbn LB. Occlusl cnt in the frontl plne s reflection of fcil symmetry. J Orl Mxillofc Surg. 1997;55: Choi JY, Hwng JM, Bek SH. Virtul model surgery nd wfer fbriction using 2-dimensionl cephlogrms, 3- dimensionl virtul dentl models, nd stereolithogrphic technology. Orl Surg Orl Med Orl Pthol Orl Rdiol. 2012;113: Dhlburg G. Sttisticl Methods for Medicl nd Biologicl Students. New York, NY: Interscience Publiction; Jung YJ, Kim MJ, Bek SH. Hrd nd soft tissue chnges fter correction of mndibulr prognthism nd fcil symmetry by mndibulr setbck surgery: three-dimensionl nlysis using computerized tomogrphy. Orl Surg Orl Med Orl Pthol Orl Rdiol Endod. 2009;107: e Mrinetti CJ. The lower musculr blnce of the fce used to lift lbil commissures. Plst Reconstr Surg. 1999;104: Pélissier P, Pistre V, Bustmnte K, Mrtin D, Budet J. The modiolus. Comprtive ntomy, embryologicl nd physiologicl review, surgicl importnce. Ann Chir Plst Esthet. 2000;45:41 47.