Functional genioplasty in growing patients

Original Article

Functional genioplasty in growing patients

Sylvain Chamberlanda; William R. Proffitb; Pier-Eric Chamberlandc

ABSTRACTObjective: To evaluate the role of age as a moderator of bone regeneration patterns andsymphysis remodeling after genioplasty.Method: Fifty-four patients who underwent genioplasty at the end of their orthodontic treatmentwere divided into three age groups: younger than 15 years at the time of surgery (group 1), 15 to19 years (group 2), and 20 years or older (group 3). Twenty-three patients who did not acceptgenioplasty and had a follow-up radiograph 2 years after the end of their orthodontic treatmentwere used as a control group. Patients were evaluated at three time points: immediate preoperative(T1), immediate postoperative (T2,) and 2 years postsurgery (T3).Results: The mean genial advancement at surgery was similar for the three age groups, but theextent of remodeling around the repositioned chin was greater in group 1, less in group 2, and stillless in group 3. Symphysis thickness increased significantly during the 2-year postsurgery intervalfor the three groups, and this increase was significantly greater in group 1 than in group 3.Remodeling above and behind the repositioned chin also was greater in the younger patients. Thiswas related to greater vertical growth of the dentoalveolar process in the younger patients. Therewas no evidence of a deleterious effect on mandibular growth.Conclusion: The outcomes of forward-upward genioplasty include increased symphysisthickness, bone apposition above B point, and remodeling at the inferior border. When indicationsfor this type of genioplasty are recognized, early surgical correction (before age 15) produces abetter outcome in terms of bone remodeling. (Angle Orthod. 0000;00:000–000.)

KEY WORDS: Genioplasty; Inferior border osteotomy; Lip function; Facial proportions

INTRODUCTION

Inferior border osteotomy of the mandible for chinaugmentation was first reported by Trauner andObwegeser1 in 1957 and has become widely used asan isolated procedure or in combination with othermaxillo-mandibular osteotomies. Although the chin canbe repositioned in any direction with this procedure,simultaneous advancement and upward movement tocorrect both a horizontal deficiency and vertical excessis the most common. Precious and Delaire2 defined

forward-upward repositioning of the chin as a ‘‘func-tional genioplasty’’ because it provides a beneficialchange in lip function and helps to obtain lip compe-tency at repose.2 It also tends to reduce lip pressureagainst the lower incisors.3 When orthodontic treatmenthas created mandibular incisor protrusion, improvingthe relationship between the chin and mandibularincisors (the Holdaway ratio in cephalometric analysis)is thought to improve the chance of incisor stability—and one way to do that is to advance the chin rather thanretracting the incisors. This can be particularly helpfulwhen the improvement in occlusion in Class II patientswas achieved largely by tooth movement because ofminimal or unfavorable mandibular growth.

These functional and stability benefits stand, ofcourse, in addition to the esthetic improvementenjoyed with genioplasty. Facial appearance can bea serious psychosocial handicap, even early in life,4

and functional genioplasty offers a means to improveesthetics, function, and stability in conjunction withorthodontic treatment.

Although a number of publications on inferior bodyosteotomy for genioplasty have appeared, only a few

a Private practice, Quebec, Canada.b Kenan Distinguished Professor, Department of Orthodontics,

School of Dentistry, University of North Carolina, Chapel Hill, NC.c PhD student, Department of Psychology, Universite du

Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, Canada.Corresponding author: Dr Sylvain Chamberland, 10345 Boul

de l’Ormiere Quebec, Qc G2B 3L2, Canada(e-mail: [email protected])

Accepted: June 2014. Submitted: March 2014.Published Online: July 31, 2014G 0000 by The EH Angle Education and Research Foundation,Inc.

DOI: 10.2319/030414-152.1 1 Angle Orthodontist, Vol 00, No 0, 0000

studies have data for this procedure in adolescents,and none include follow-up of a control group whowere evaluated as potentially benefiting from func-tional genioplasty but rejected it. The optimum agefor genioplasty has been somewhat controversial. Thepositive psychosocial reaction to improved facialappearance would suggest earlier treatment forseverely affected patients4,5; concerns about possiblenegative effects on growth and decreased stabilitywould be the major reason for waiting until little or nogrowth remained.6 Martinez et al.7 reported in 1999that there is better regeneration of symphysis thick-ness in patients younger than age 15 than in oldernongrowing individuals. More recently, Frapier et al.8,9

suggested that early genioplasty could improve thedirection of mandibular growth and might increasenasal breathing because of improved lip function, butthese assertions were based on samples that were toosmall and diverse for broad generalization.

An isolated lower border osteotomy requires generalanesthesia, but not overnight hospitalization, and iscommonly done as a day-op procedure either in ahospital or a free-standing surgical center. In the UnitedStates, genioplasty is usually part of a larger orthog-nathic surgery plan because medical insurance willalmost never cover the cost of an isolated procedure.This is not the case in Canada, where medical coverageis provided. The aims of the study were to clarify theoptimal time for functional genioplasty from evaluationof (1) the pattern of bone remodeling at the chin afterfunctional genioplasty and (2) the pattern of postsurgicalstability in growing and nongrowing patients.

MATERIALS AND METHODS

Patient Sample

All participants in this research project were treated inthe private orthodontic practice of the senior author. Thesurgery patients had lateral cephalometric radiographsat three time points: T1, immediately prior to genioplasty,which was done at the end of their orthodontic treatment;T2, immediately after the genioplasty; and T3, at 2-yearfollow-up. The initial sample was all of the 59 patientswho had this surgery between June 1992 and December2012; five were excluded because of missing radio-

graphs, for a final sample size of 54. This group wasdivided into three age groups: younger than 15 years attime of surgery (group 1, n 5 28), 15 to 19 years (group2, n 5 16), and 19 years or older (group 3, n 5 10;Table 1). Skeletal age (maturation of vertebrae) was notused because chronologic age is more likely to predictthe peak of adolescent growth,10 and age 15 was thecutoff point in the only previous report of age-relatedchanges in symphysis remodeling after genioplasty.7

It is difficult to assess exactly how many patientswere offered a genioplasty and declined it, but we wereable to find 23 patients who did not accept genioplastyand had a follow-up radiograph 2 years after the end oftheir orthodontic treatment. This control group (group4) had only two observation time points: at the end oforthodontic treatment and 2-year follow-up. They weresimilar to the younger surgical patients (group 1) inage, percentage female, a-p and vertical chin position,and symphysis thickness at baseline and therefore arecomparable to that group. Five of the control groupeventually joined the surgery group because theydecided to accept genioplasty after their 2-yearpostorthodontics records had been obtained.

Surgical Procedure

A mandibular lower border osteotomy was per-formed with the patient under general anesthesia atHopital l’Enfant-Jesus, Quebec, Canada, by the sameoral-maxillofacial surgeon, following the techniquedescribed by Precious and coworkers.11 Anterior andsuperior repositioning of the chin was achieved bysliding the chin to its new position. For 49 of the 54patients, wire osteosynthesis was achieved with atleast three transosseous double strands of 28-gaugestainless-steel wire. The other five patients had bonescrews. Neither the wire nor screw fixation wasremoved.

Cephalometric Data

Lateral cephalometric radiographs for patients partic-ipating in this study prior to mid-2008 were taken on anOrthophos Ceph machine (Siemens, Beinsheim, Ger-many); afterward, an OP100 (Instrumentarium, Tuusula,Finland) unit was used. All radiographs were traced by

Table 1. Patient Characteristics

Baseline Age at T1 (Years) /1-APg (u) ADH (mm) FMA (u)

Group N Mean SD Range % Female Mean SD Range Mean SD Range Mean SD

Group 1 (,15 years) 28 14.00 0.67 12.62 to14.95 32 3.01 1.49 0.4 to 5.3 44.88 2.67 37.1 to 50.7 34.06 4.14

Group 2 (15–19 years) 16 16.65 1.05 16.16 to18.61 44 3.67 1.74 21.2 to 6.5 45.92 3.27 40.1 to 51.1 32.46 3.39

Group 3 (.19 years) 10 28.65 4.96 22.35 to 36.16 40 2.73 1.90 20.3 to 5.6 48.00 4.76 36.9 to 53.1 34.74 6.35

Group 4 (control) 23 14.31 1.41 11.46 to 16.44 39 3.18 1.56 1.0 to 5.8 43.90 2.39 39.5 to 49.6 31.97 4.25

2 CHAMBERLAND, PROFFIT, CHAMBERLAND

Angle Orthodontist, Vol 00, No 0, 0000

Figure 1. Cephalometric landmarks and dimensional measurements. Symphysis thickness was evaluated by measurement of the distance

between the anterior and posterior borders 4 mm below the apex of the lower incisors (ACP-PCP). Vertical chin height was evaluated by the

perpendicular distance from the mandibular plane to the lower incisor tip (ADH). Remodeling of the area above the repositioned chin was

evaluated by change at B point and symphysis thickness increase; remodeling of the area on the inferior border was evaluated by the change of

the depth of the notch at the posterior limit of the osteotomy cut, by measuring the perpendicular distance from PGP to the mandibular plane (MP).

FUNCTIONAL GENIOPLASTY IN GROWING PATIENTS 3


the senior author with Quick Ceph Studio (Quick CephSystems, San Diego, Calif). Magnification was calibratedfor both the older scanned films and newer digitalradiographs. An x–y cranial base coordinate systemwas constructed through sella with the x-axis drawn 7u tothe sella-nasion line and the y-axis passing through sella,perpendicular to the x-axis (Figure 1).

For all subjects, the recommendation for genioplastywas based on clinical evaluation of the prominence andvertical position of the soft tissue chin relative to the lipsand midface. Cephalometric data for pretreatment a-pchin deficiency relative to the lower incisors, the verticaldistance from the incisors to the bottom of the chin, andthe mandibular plane angle are shown in Table 1. To

Figure 2. Facial changes before and after functional genioplasty for a typical patient. Note the improvement in facial proportions, improved lip

closure at repose, and improved display of the incisors on smile. Moving the chin up also moves the lower lip upward and decreases the display

of lower incisors.

Table 2. Change at Surgery (mm)

Genial Advancement at

Surgery T1–T2 Genial Vertical Reduction T1–T2 /1-APg Change T1–T2

Group n Mean SD Range Mean SD Range Mean SD Range

Group 1 (,15 years) 28 6.45 2.2 2.6 to 10.6 2.93 2.5 22.1 to 7.4 21.61 1.08 22.9 to 2.6

Group 2 (15–19 years) 16 5.88 1.77 1.5 to 9.2 3.53 2.77 20.5 to 8.2 22.04 0.70 23.1 to 20.4

Group 3 (.19 years) 10 5.25 2.79 1.4 to 10.7 3.83 1.88 0 to 7.3 21.64 0.85 22.8 to 20.5



evaluate postsurgical changes in the chin, the focus wason four measurements (Figure 1): symphysis thickness,vertical height of the chin relative to the lower incisors,and remodeling above and behind the chin.

Statistical Analysis

The distribution of the sample was evaluated andjudged to be close enough to normal to use mean,standard deviation, and range as descriptive statistics.The study design involved comparison among the threeage groups who underwent genioplasty (groups 1, 2,and 3) and comparison of the youngest group (group 1)to an age-matched control group (group 4) with thesame characteristics. For both comparisons, changesscores between time points were analyzed with multi-variate analysis of covariance, in which gender effectwas evaluated as a covariate. Although gender did notcontribute to the differences, we kept this effect in themodel to adjust the conclusions for gender. One-samplet-tests were used to evaluate the chance that data foreach time point were different from zero; pairwisecomparisons with Bonferroni adjustments for multiplecomparisons were used to evaluate the change between

groups. Unlike the Tukey adjustment, the Bonferronimethod does not need correction because of theunbalanced sample size between groups. The level ofsignificance was set at P , .05. All of these analyseswere conducted with IBM SPSS Statistics (version 21).

To assess the method error, 15 cephalograms wereredigitized. An analysis of variance showed that therewas no significant difference between the first tracingand the redigitized tracing. The coefficient of fidelity forall variables was .9997. The coefficient of fidelity forthe symphysis thickness change and remodeling of theinferior border (PGP) was .9231. The analysis of themethod error was conducted with SAS 9.4 (SASInstitute Inc, Chicago, Ill).

RESULTS

Change at Surgery (T1–T2)

Changes at surgery for a typical functional genio-plasty patient are shown in Figure 2, and the data aresummarized in Table 2. There were no significantdifferences in genial advancement or vertical reductionbetween the three age groups (Table 2). The changeswere highly statistically significant (,.0001 for both).

Change from Surgery to Follow-up (T2–T3)

Changes in symphysis thickness. Symphysis thick-ness increased significantly for all three surgicalgroups and showed a small but significant decreasefor the controls (Table 3; Figure 3). Pairwise compar-isons between groups 1 and 3, controlling for differentsample size, showed a significant difference (P 5

.004) between these two groups for the symphysisthickness change.

When there is considerable variability in treatmentoutcomes, as there often is, the percentage of patientswith clinically significant change can provide a betterunderstanding of the data.12,13 Figure 3 shows that39% of the youngest patients (group 1) had a 2- to 4-mm increase in symphysis thickness during the 2 yearspostsurgery, and 28% had a .4-mm increase.Therefore, two-thirds of the youngest patients had amore than 2-mm increase in symphysis thickness. Thepercentage with change .2 mm was smaller in group2, but two of those patients (7%) had a .4-mm

Figure 3. The percentages of patients with .2- and .4-mm changes

in symphysis thickness after genioplasty. Note the differences in the

genioplasty age groups and the contrast to the control patients.

Table 3. Symphysis Thickness at Each Time Point (mm)

T1 T2 T3 T2–T3 T1–T3

n Mean SD Mean SD Mean SD Mean SD Mean SD

Group 1 (,15 years) 28 8.39 1.62 8.50 1.57 11.73 2.86 3.24 2.68 3.44 2.51

Group 2 (15–19 years) 16 8.14 1.78 8.29 1.84 10.35 2.58 2.06 1.24 2.15 1.88

Group 3 (.19 years) 9 8.13 2.37 8.07 2.48 9.18 2.21 1.11 1.02 1.04 1.16

Group 4 (controls) 23 — — 8.84 2.20 8.46 2.25 20.44 0.67 — —



increase. No patients in the oldest group (group 3) hada .4-mm change, and only two (20%) had a .2-mmchange. In contrast to the genioplasty groups, nopatient in the control group had an increase insymphysis thickness from the end of treatment to 2-year recall, and seven (30%) had a 1-mm or greaterdecrease.

Changes in coordinate positions and dimensionalrelationships. Data for changes in coordinate positionsfor points B, Pg and Me are displayed in Tables 4 and5, and the changes for Pg and Me are showngraphically in Figures 4 and 5. It is important to keepin mind that these changes are due to a combination ofmandibular growth and surface remodeling at and nearthe chin.

Horizontal growth change at Pg after genioplasty(T2–T3) of group 1 was less than the control group, butthe difference was not statistically significant. Group 1showed a significant forward growth change, while forgroups 2 and 3, the horizontal change at Pg was not

significant (Figure 4). Vertical growth change at Meafter surgery was similar to the control group, and thevertical change was significant for group 1, group 2, andcontrols (Figure 5). Figure 6 shows the pattern ofvertical dentoalveolar change postgenioplasty. Allchanges were statistically significant from zero for eachgroup, but for group 1, the T2–T3 change wassignificantly different from groups 2, 3, and 4. Oneshould keep in mind that this vertical change at Me wasbalanced by posterior facial growth: the mandibularplane angle change for group 1 was not significant.Pairwise comparisons are shown in Table 6. Thisconfirms that remodeling in group 1 is different fromremodeling in groups 3 and 4.

Three variables were significantly correlated to thepostsurgical change in symphysis thickness: theamount of genial advancement, the amount of verticaldentoalveolar growth, and the age at surgery. TheR value of these three variables taken together was.47 (r 2 5 .22), and their influence was significant at the

Table 4. Horizontal Changes in Coordinate Position

Group n

T2–T3 (Postsurgery to 2 Years) T1–T3 (Presurgery to 2 Years)

Mean SD

Intragroup

Significance Mean SD

Intragroup

Significance

Horizontal change

D B point Group 1 (,15 years) 28 3.72 2.89 ,.001 4.21 3.47 ,.001

Group 2 (15–19 years) 16 2.13 1.92 ,.001 2.33 1.65 ,.001

Group 3 (.19 years) 9 1.90 1.42 .004 1.68 1.74 .020

Group 4 (controls) 23 2.47 2.57 ,.001 2.47 2.57 ,.001

D BPg to MP Group 1 (,15 years) 28 1.06 1.33 ,.001 21.35 1.39 ,.001

Group 2 (15–19 years) 16 0.85 1.14 .009 21.59 2.40 .018

Group 3 (.19 years) 9 0.69 1.00 n.s. 20.78 1.70 n.s.

Group 4 (controls) 23 20.36 0.58 .007 20.36 0.58 .007

D Pg Group 1 (,15 years) 28 1.17 2.89 .042 7.57 3.90 ,.001

Group 2 (15–19 years) 16 20.21 1.42 n.s. 6.13 1.99 ,.001

Group 3 (.19 years) 9 0.48 2.06 n.s. 5.70 2.75 , .001

Group 4 (controls) 23 2.67 2.85 .005 2.67 2.85 .005

D Symphysis thickness Group 1 (,15 years) 28 3.24 2.68 ,.001 3.44 2.51 ,.001

Group 2 (15–19 years) 16 2.06 1.24 ,.001 2.15 1.88 ,.001

Group 3 (.19 years) 9 1.11 1.02 .011 1.04 1.16 .027

Group 4 (controls) 23 20.44 0.67 .004 20.44 0.67 .004

D Me Group 1 (,15 years) 28 0.78 2.78 n.s. 7.68 3.81 ,.001

Group 2 (15–19 years) 16 0.00 1.71 n.s. 6.79 2.27 ,.001

Group 3 (.19 years) 9 0.68 1.69 n.s. 6.42 3.38 ,.001

Group 4 (controls) 23 2.38 2.82 ,.001 2.38 2.82 ,.001

D Pg relative to N

perpendicular to FH

Group 1 (,15 years) 28 20.48 2.54 n.s. 5.60 3.31 ,.001

Group 2 (15–19 years) 16 20.86 1.25 .015 5.32 1.70 ,.001

Group 3 (.19 years) 9 20.24 2.25 n.s. 4.93 3.14 .002

Group 4 (controls) 23 0.77 2.07 n.s. 0.77 2.07 n.s.

Sagittal relationship

D ABOP occlusal

relationship

Group 1 (,15 years) 28 20.69 1.57 .028 21.31 1.75 ,.001

Group 2 (15–19 years) 19 21.44 2.09 .015 21.19 1.47 .005

Group 3 (.19 years) 9 21.17 1.46 .043 21.79 1.67 .012


D/1-APg Group 1 (,15 years) 28 0.80 0.85 ,.001 20.87 1.01 ,.001

Group 2 (15–19 years) 16 20.03 0.73 n.s. 22.18 0.53 ,.001

Group 3 (.19 years) 9 0.38 0.65 n.s. 21.39 0.69 ,.001

Group 4 (controls) 23 0.43 0.91 .033 0.43 0.91 .033



P , .05 level (P 5 .03). When the predictor variableswere ranked by the standardized coefficient beta, theresult clearly showed that the younger the age atsurgery and the greater the dentoalveolar growth asincisors erupted, the more the symphysis wouldincrease in thickness due to bone apposition. Theamount of genial advancement was not a determinant.

Remodeling changes. Remodeling of the symphysisafter genioplasty involves bone apposition above therepositioned chin, with changes leading up to and evenbeyond point B, and removal of bone adjacent to thenotch in the lower border of the mandible that ispresent after the chin has been moved (Figures 7 and8). Figure 8 illustrates the typical pattern of remodelingin the younger patients. Statistical analysis showedthat the decrease in the depth of the notch at theinferior border was significant for groups 1 and 2, butno significant change was noted for the adult group(Figure 7; Table 5). There was no significant change ofthe inferior border in the control group.

Ranking the predictor variables confirmed that thegreater the dentoalveolar growth postsurgery, themore complete the remodeling in both areas, butneither the amount of genial advancement nor the ageat surgery were significant predictors. It is clear,therefore, that age at genioplasty, which affects theamount of incisor eruption afterward, does make adifference in the extent of both bone apposition and

remodeling, with more apposition and remodeling inpatients younger than 15 years, less in late adoles-cents, and still less in adults.

Stability of the Surgical Repositioning

It is important to keep in mind that postsurgicalchanges in the position of the chin were due to acombination of mandibular growth and surface remode-ling at and near the chin. For the younger patients, thisis best evaluated by comparing the change in group 1with the control group. The mean A-P change at Pg aftergenioplasty (T2–T3) of group 1 was less than the controlgroup (ie, the genioplasty patients were slightly morestable), but the difference was small and not statisticallysignificant (see Figure 4). The vertical change at Meafter surgery also was similar to the control group (seeFigure 5).

The data show, therefore, that forward and down-ward growth at the chin in this sample was notsignificantly affected by genioplasty and that thechanges in chin position produced by the genioplastywere maintained in growing patients.

DISCUSSION

The data from this study make it clear that both theamount of new bone formation after genioplasty andthe extent of remodeling around the repositioned chin

Table 5. Vertical Changes in Coordinate Position

T2–T3 (Postsurgery to 2 Years) T1–T3 (Presurgery to 2 Years)

Group n Mean SD

Intragroup

Significance Mean SD

Intragroup

Significance

Vertical change

D B point Group 1 (,15 years) 28 21.75 2.49 .001 21.93 2.73 .001

Group 2 (15–19 years) 16 20.53 3.70 n.s. 20.67 3.50 n.s.

Group 3 (.19 years) 9 20.09 2.90 n.s. 20.02 2.47 n.s.

Group 4 (controls) 23 22.89 3.65 .001 22.89 3.65 .001

D Pg Group 1 (,15 years) 28 24.10 3.36 ,.001 21.75 3.59 .016

Group 2 (15–19 years) 16 22.71 2.32 ,.001 0.01 2.69 n.s.

Group 3 (.19 years) 9 21.04 2.52 n.s. 1.86 3.12 n.s.

Group 4 (controls) 23 23.69 4.08 ,.001 23.69 4.08 ,.001

D Me Group 1 (,15 years) 28 25.01 3.09 ,.001 22.14 3.30 .002

Group 2 (15–19 years) 16 22.57 2.43 .001 0.90 3.69 n.s.

Group 3 (.19 years) 9 21.26 2.35 n.s. 2.60 2.83 .025

Group 4 (controls) 23 24.46 4.61 ,.001 24.46 4.61 ,.001

D FMA Group 1 (,15 years) 28 0.40 1.61 n.s. 25.89 2.50 ,.001

Group 2 (15–19 years) 16 0.86 0.90 .002 25.48 2.25 ,.001

Group 3 (.19 years) 9 0.39 1.28 n.s. 26.14 2.07 ,.001

Group 4 (controls) 23 20.72 1.62 .044 20.72 1.62 .044

D ADH (anterior dental height) Group 1 (,15 years) 28 3.11 1.93 ,.001 22.78 1.98 ,.001

Group 2 (15–19 years) 16 1.20 1.13 .001 24.86 2.39 ,.001

Group 3 (.19 years) 9 0.74 0.89 .036 25.29 1.92 ,.001

Group 4 (controls) 23 1.84 1.86 ,.001 1.84 1.86 ,.001

D PGP to MP Group 1 (,15 years) 28 1.17 1.29 ,.001 22.84 1.88 ,.001

Group 2 (15–19 years) 16 0.62 0.88 .013 23.26 1.75 ,.001

Group 3 (.19 years) 9 0.30 1.00 n.s. 23.79 1.27 .025




are greater in patients who are still in mid-adolescencethan in late adolescents and adults. Our results bothconfirm and extend the earlier report by Martinez thatshowed better healing in patients younger than age 157

and support other findings6,14–18,21 that after genioplas-ty, bone remodeling occurs at the inferior border of theproximal segment between the distal point of theosteotomy cut and the advanced distal segment. Ourgroups 1 and 2 showed a statistically significant meanreduction of this notch (1.2 6 1.3 mm and 0.6 6

0.9 mm, respectively), while the adult group had amodest nonsignificant reduction of 0.3 6 1.0 mm.

In this study, the control group had a slight butsignificant resorption at B point (0.4 6 0.6 mm), whichis consistent with the usual pattern of growth at thechin in adolescence. Following genioplasty, as in Parket al.,18 Shaughnessy et al.,19 and Precious et al.,11,17

we found that bone apposition occurred at B point, witha similar change in all three age groups (0.7 to1.0 mm). Bony angles above the repositioned chinbecame rounded, and rough edges became smooth.Shaughnessy et al.19 suggested that the autogenousbone grafts from the iliac crest that they placed in this

area were responsible for the improved contours.Since none of the patients of the present studyreceived a graft and all had significant apposition atB point, we question the indication for grafting boneinto that area, particularly with bone from a donor sitesuch as the iliac crest that requires invasive surgery.

Would it have made a difference if we used skeletalage instead of chronologic age in separating the threegroups? It would have been possible to do that withoutadditional radiation by using maturation of the cervicalvertebrae. The conclusion of a recent review ofmethods to establish peak growth at adolescence,however, concluded that chronologic age is better.10 Itis possible that the group younger than 15 years hadsome relatively mature girls, while the age 15–19group had some relatively immature males, but thatwould have minimized rather than augmented thedifferences we observed.

The increased remodeling of the facial alveolar boneabove the osteotomy site is important in the context ofbone support for the lower incisors, because lowerincisors tend to be proclined in individuals with adeficient chin even without treatment. This often is

Figure 4. Horizontal change at Pg. The younger genioplasty patients and the controls showed significant forward growth at Pg; the change at Pg

for groups 2 and 3 was nonsignificant. The growth change of group 1 was not statistically different from the controls (ie, there was no evidence of

decreased forward growth in the young genioplasty patients).



Figure 5. Vertical change at Me. Vertical growth change at Me after surgery (T2–T3) was significant for groups 1 and 2 and was similar to the

control group, showing that vertical growth at Me was not affected by genioplasty.



increased during their orthodontic treatment as thelower arch is expanded to align crowded incisors and/or Class II elastics are used to correct the occlusion.The result can be bone dehiscence and stripping ofgingival tissue. Our data show that as the boneremodels after genioplasty, there is formation of newalveolar bone facial to the teeth at a higher level in the

younger patients, and this can be attributed topostgenioplasty eruption of the teeth as face heightincreases more in the younger group.

Our patients also had formation of new bone onthe lingual side behind the prominence of the chin, witha greater increase in symphysis thickness in theyounger patients that persisted during the first 2 years

Figure 6. Vertical alveolar dental change. All changes were statistically significant for each group. Note that the mean 6-mm difference between

the young genioplasty patients and controls created by surgery was maintained at 2-year recall.



posttreatment. The symphysis is a highly stressedarea during normal function. Is greater symphysisstrength a long-term outcome of genioplasty via lowerborder osteotomy? We have no data to support thatpossibility, but there is nothing to indicate thatgenioplasty before the completion of mandibulargrowth weakens the chin.

Does repositioning the chin have a deleterious effecton mandibular growth? That is a valid concern and hasbeen a major reason for delaying it until growth isessentially completed. Our control group of mandibulardeficient young patients who did not accept genioplastyallows a comparison of mandibular growth in treatedand untreated individuals with similar mandibularmorphology. Growth at the chin is largely due to growthof the mandible, but in the normal growth pattern, thechin becomes more prominent, not by apposition in thepogonion area, but by resorption above pogonion thatextends upward toward point B.14 In a growing individualwith an indication for forward-upward genioplasty, datafrom our control group show that lip incompetencypersists, facial convexity is maintained, bone resorptionoccurs at point B, and symphysis thickness has atendency to decrease. Change or the lack of it in atypical control patient is shown in Figure 9.

Although our data show no evidence to support anegative effect on mandibular growth from a lowerborder osteotomy, whether it is done in early adoles-cence or later, it will be important to follow the youngerpatients until the end of the normal growth period to besure that there is no residual effect, and this isplanned. The mandibular plane angle decreases

slightly during normal adolescent growth, and this iswhat we observed in both the younger genioplastypatients and the controls. It can be difficult to avoidunerupted permanent teeth during a lower borderosteotomy in a child, and this is a contraindication forearly genioplasty. Eruption of mandibular canines,usually around age 12–13 years, removes thatlimitation for most individuals.

Most previous studies of stability after genioplastyhave reported that it is the most stable of theorthognathic surgery procedures and that significantrelapse is almost never observed.15,19,20 Tulasne,16

using a different surgical procedure than the one inthis study, reported greater relapse (about a 40%change) for young patients. Martinez et al.7 also notedgreater relapse in their younger group (a 16% change),but it was neither clinically nor statistically significant.Our findings do not support a greater relapse at Pg foryounger growing patients. Since almost all of ourpatients (91%) had wire fixation, better postsurgicalstability with more costly bone screws may not be aconsideration for this type of genioplasty.17

CONCLUSIONS

N Benefits of genioplasty via a lower border osteotomythat moves the chin forward and upward (a functionalgenioplasty) include increased symphysis thickness,bone apposition at B point, and remodeling at theinferior border. Better bone apposition and remodel-ing is observed in younger patient compared withadults.

Table 6. Pairwise Comparisons Between Groups

T2–T3 T1–T3

Group

1–Group 4

Group

1–Group 2

Group

1–Group 3

Group

2–Group 3

Group

1–Group 4

Group

1–Group 2

Group

1–Group 3

Group

2–Group 3

Horizontal change

D B point n.s. n.s. .012 n.s. n.s. n.s. n.s. n.s.

D BPg to MP ,.001 n.s. n.s. n.s. .002 n.s. n.s. n.s.

D Pg .069 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.

D Symphysis thickness ,.001 n.s. .004 n.s. ,.001 n.s. .002 n.s.

D Me .049 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.

D Pg relative to N perpendicular to FH n.s. n.s. n.s. n.s. ,.001 n.s. n.s. n.s.

Vertical change

D B point n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.

D Pg n.s. n.s. .006 n.s. n.s. n.s. .018 n.s.

D Me n.s. .022 .003 n.s. n.s. n.s. .013 n.s.

D FMA .017 n.s. n.s. n.s. ,.001 n.s. n.s. n.s.

D ADH (anterior dental height) .021 ,.001 ,.001 n.s. ,.001 .013 .003 n.s.

D PGP to MP ,.001 n.s. .156 n.s. ,.001 n.s. n.s. n.s.

Sagittal relationship

D ABOP occlusal relationship .028 n.s. n.s. n.s. .001 n.s. n.s. n.s.

D/1-APg n.s. .004 n.s. n.s. ,.001 ,.001 n.s. .012



Figure 7. Remodeling at the inferior border. The notch at the inferior border of the proximal segment between the distal point of the osteotomy cut

and the advanced distal segment was significantly reduced for groups 1 and 2 (1.2 6 1.3 mm and 0.6 6 0.9 mm, respectively), while the adult

group had a modest nonsignificant reduction of 0.3 6 1.0 mm. The net outcome at T3 showed a significant decrease of the depth of this notch

when comparing group 1 to adults (P 5 .018).



N When indications for such a genioplasty are recog-nized, early surgical correction (before age 15)produces a better outcome in terms of bone remodel-ing. This is related primarily to greater vertical growth ofthe dentoalveolar process in the younger patients.

N There is no difference in postsurgical stability inyounger and older genioplasty patients.

ACKNOWLEDGMENTS

We thank Dr Dany Morais for his surgical excellence, Mr.Warren McCollum for creating the graphs and charts, MsRamona Hutton-Howe for preparation of photographs forpublication, Mr David Emond of Laval University for statisticalconsultation, and the Orthodontic Fund of the Dental Foundationof North Carolina for support of production costs. The juniorauthor is supported by a doctoral scholarship from theDesjardins Foundation, the Quebec Research Fund on Societyand Culture, and Social Sciences and Humanities ResearchCouncil of Canada.

REFERENCES

1. Trauner R, Obwegeser H. The surgical correction ofmandibular prognathism and retrognathia with considerationof genioplasty. II. Operating methods for microgenia anddistoclusion. Oral Surg Oral Med Oral Pathol. 1957;10:899–909.

2. Precious DS, Delaire J. Correction of anterior mandibularvertical excess: the functional genioplasty. Oral Surg OralMed Oral Pathol. 1985;59:229–235.

3. Proffit WR, Phillips C. Adaptations in lip posture andpressure following orthognathic surgery. Am J Orthod.1988;93:294–304.

4. McGregor FC. Facial disfigurement, problems and manage-ment of social interactions and implications for mentalhealth. Aesthetic Plastic Surg. 1990;14:249–257.

5. Phillips C, Proffit WR. Psychosocial aspects of dentofacialdeformity and its treatment. In: Proffit WR, White RP Jr,

Sarver DM, eds. Contemporary Treatment of DentofacialDeformity. 5th ed. St Louis, Mo: Mosby; 2003;69–89.

6. Polido WD, de Clairefont RL, Bell WH. Bone resorption,stability, and soft-tissue changes following large chinadvancements. J Oral Maxillofac Surg. 1991;49:251–256.

7. Martinez JT, Turvey TA, Proffit WR. Osseous remodelingafter inferior border osteotomy for chin augmentation: anindication for early surgery. J Oral Maxillofac Surg. 1999;57:1175–1180.

8. Frapier L, Jaussent A, Yachouh J, et al. Impact of genioplastyon mandibular growth during puberty. Int Orthod. 2010;8:342–359.

9. Frapier L, Picot M-C, Gonzales J, et al. Ventilatory disordersand facial growth: benefits of early genioplasty. Int Orthod.2011;9:20–41.

10. Mellion ZJ, Behrents RG, Johnston LE. The pattern of facialskeletal growth and its relationship to various commonindexes of maturation. Am J Orthod Dentofacial Orthop.2013;143:845–854.

11. Precious DS, Armstrong JE, Morais D. Anatomic placementof fixation devices in genioplasty. Oral Surg Oral Med OralPathol. 1992;73:2–8.

12. Bailey LJ, Phillips C, Proffit WR. Long-term outcome ofsurgical Class III correction as a function of age at surgery.Am J Orthod Dentofac Orthop. 2008;133:365–370.

13. Proffit WR, Phillips C, Turvey TA. Long-term stability ofadolescent versus adult surgery for treatment of mandib-ular deficiency. Int J Oral Maxillofac Surg. 2010;39:327–332.

14. Marshall SD, Low LE, Holton NE, et al. Chin development asa result of differential jaw growth. Am J Orthod DentofacOrthop. 2011;139:456–464.

15. Erbe C, Mulie RM, Ruf S. Advancement genioplasty in ClassI patients: predictability and stability of facial profile changes.Int J Oral Maxillofac Surg. 2011;40:1258–1262.

16. Tulasne JF. The overlapping bone flap genioplasty.J Craniomaxillofac Surg. 1987;15:214–221.

17. Precious DS, Cardoso AB, Cardoso MC, Doucet JC. Costcomparison of genioplasty: when indicated, wire osteosyn-thesis is more cost-effective than plate and screw fixation.Oral Maxillofac Surg. In press.

Figure 8. The typical pattern of bone remodeling in young patients as seen in superimposed cephalometric tracings. Note that as growth

occurred, remodeling added bone above the repositioned chin segment and decreased the depth of the notch on the inferior border. These

changes are greater in the younger patients.



18. Park HS, Ellis E, Fonseca RJ, Reynolds ST, Mayo KH. Aretrospective study of advancement genioplasty. Oral SurgOral Med Oral Pathol. 1989;67:481–489.

19. Shaughnessy S, Mobarak KA, Hogevold HE, Espeland L. Long-term skeletal and soft-tissue responses after advancementgenioplasty. Am J Orthod Dentofac Orthop. 2006;130:8–17.

20. Davis WH, Davis CL, Daly BW, Taylor C. Long-term bonyand soft tissue stability following advancement genioplasty.J Oral Maxillofac Surg. 1988;46:731–735.

21. Polido WD, Bell WH. Long-term osseous and soft tissuechanges after large chin advancements. J CraniomaxillofacSurg. 1993;21:54–59.

Figure 9. Facial changes in a typical untreated control patient, who was age 15 years 10 months at the end of orthodontic treatment and age

17 years 9 months on follow-up. Note that the mentalis and lip strain and A-P chin deficiency were not improved at follow-up.



Functional genioplasty in growing patients

Health & Medicine

Transcript of Functional genioplasty in growing patients