anatomy and cephalometric analysis with step by step procedure of genioplasty

1. Genioplasty
By – Dr. Shalini Singh
PG OMFS

2. Contents
•Introduction
•Anatomy
•Preoperative evaluation
• Facial analysis
• Cephalometric evaluation
•History of genial procedures
•Chin classification
•Various techniques to correct deformities of chin
• Osseous genioplasty
• Alloplastic genioplasty
•Complications
•Conclusion
•References

3. Introduction
• Genioplasty is the surgical procedure used to alter the size
and morphology of the bony chin with concomitant changes
in the surrounding soft tissues. It can be used as a single
procedure or it can be used as an adjunctive procedure along
with other major osteotomies of the jaw.

4. Anatomy

6. Anatomy

7. Preoperative Evaluation
• Chin deformitiesChin deformities can manifest incan manifest in three dimensionsthree dimensions, but, but
the vast majority is in the horizontal planethe vast majority is in the horizontal plane..
• Analysis --Analysis --scrutiny of the skeletal, dental, and soft tissuescrutiny of the skeletal, dental, and soft tissue
structures.structures.
• Vertical balanceVertical balance of the face can be judged by usingof the face can be judged by using
relative size and proportions of the various structures.relative size and proportions of the various structures.
• Harmony is more important than absoluteHarmony is more important than absolute
proportionalityproportionality..
• These include lip position, shape and depth of theThese include lip position, shape and depth of the
labiomental fold, and the soft tissue envelope coveringlabiomental fold, and the soft tissue envelope covering
the mandibular symphysis.the mandibular symphysis.

9. CEPHALOMETRIC EVALUATION
• Down's,Down's,
Steiner's,Steiner's,
andand
Tweed'sTweed's
analysesanalyses
The bony chin position can be evaluated in the anteroposterior (AP) dimension
by using Sella-Nasion (SN)-pogonion (range, 72 to 88 degrees; mean, 80
degrees), SN-B point (72 to 87 degrees; mean, 79 degrees).
Other cephalometric evaluations also exist, includ­ing the Y growth axis (range,
53 to 66 de­grees; mean, 59 degrees).

10. SOFT TISSUE EVALUATION
• Gonzales-Ulloa andGonzales-Ulloa and
StevensStevens, in which a, in which a
line is constructedline is constructed
perpendicular to theperpendicular to the
Frankfort horizontalFrankfort horizontal
and passing throughand passing through
the soft tissue nasion.the soft tissue nasion.
The soft tissue chinThe soft tissue chin
should be tangent toshould be tangent to
this linethis line..

11. Merrifield's "Z" angle
• is a line from the soft tissue chin tangent to the most pro­cumbent lip,is a line from the soft tissue chin tangent to the most pro­cumbent lip,
which forms an angle with the Frankfort horizontal.which forms an angle with the Frankfort horizontal.
• The upper lip should fall on the profile line, with the lower lip tangent toThe upper lip should fall on the profile line, with the lower lip tangent to
or slightly behind the profile line.or slightly behind the profile line.

12. Ricketts aesthetic plane
• a line from the tip of the nose to the chin. He found thata line from the tip of the nose to the chin. He found that
in aesthetically pleasing profiles,in aesthetically pleasing profiles, the upper lip was 4 mmthe upper lip was 4 mm
and the lower lip 2 mm behind the aesthetic planeand the lower lip 2 mm behind the aesthetic plane..

13. • HoldawayHoldaway suggested a line tangent to the chin andsuggested a line tangent to the chin and
upper lip. This line forms an angle with a lineupper lip. This line forms an angle with a line
between the nasion and basion and should be aboutbetween the nasion and basion and should be about
7 to 9 degrees.7 to 9 degrees.

14. • ZimmerZimmer proposed a line from theproposed a line from the anterior nasal spineanterior nasal spine toto
Down's "B" pointDown's "B" point and demonstrated that the nose and lips,and demonstrated that the nose and lips,
as well as the chin, were almost identical in thickness whenas well as the chin, were almost identical in thickness when
compared with this plane and that the nose had ancompared with this plane and that the nose had an
approximate ratio of 2:1 to any of the other soft tissueapproximate ratio of 2:1 to any of the other soft tissue
structures.structures.

15. COGS (cephalometric analysis
for orthognathic surgery)
B – Pg (ll MP): This is the
distance from point B to a
line perpendicular to
mandibular plane through
pogonion. This short line
describes the prominence of
the chin related to
mandibular denture base.
B – Pog (ll HP) = 7.2 ± 1.9

16. N – B (ll HP): This is also
measured in a plane
parallel to HP from point
B to the perpendicular
line dropped from N. This
measurement describes
the horizontal position of
the apical base of the
mandible in relation to N.
normal value = -6.9 +/-
4.3
N – Pg (ll HP): This is
measured in the same
manner as N-A and N-B
and indicates the
prominence of the chin.
Normal value = -6.5 +/-
5.1

17. • SteinerSteiner also used soft tissue components to define pleasingalso used soft tissue components to define pleasing
profiles. He constructed a plane from the middle of the columella,profiles. He constructed a plane from the middle of the columella,
midway between the curves of the upper lip and nasal tip. The lipsmidway between the curves of the upper lip and nasal tip. The lips
should fall on this line.should fall on this line.

18. • All cephalometric assessments should be critically weighedAll cephalometric assessments should be critically weighed
against clinical judgment and the individual needs of theagainst clinical judgment and the individual needs of the
patient.patient.
• The aesthetic desires of the patient should be a priority andThe aesthetic desires of the patient should be a priority and
the clinical and radiographic assessment used to achieve thatthe clinical and radiographic assessment used to achieve that
endpoint.endpoint.

19. History of Genial
Procedures
• HoferHofer(1942) first described horizontal sliding osteotomy---(1942) first described horizontal sliding osteotomy---
extraoral incisionextraoral incision
• Converse(Converse(1950), discussed the feasibility of bone grafts1950), discussed the feasibility of bone grafts
introduced through intraoral approachesintroduced through intraoral approaches
• Trauner and ObwegeserTrauner and Obwegeser, (1957), used the horizontal, (1957), used the horizontal
osteotomy through an intraoral incision with de-gloving of theosteotomy through an intraoral incision with de-gloving of the
anterior mandible.anterior mandible.
• Converse and Wood-SmithConverse and Wood-Smith described various applicationsdescribed various applications
and versatility of, the horizontal osteotomyand versatility of, the horizontal osteotomy
• Reichenbach and colleaguesReichenbach and colleagues (1965)proposed wedge(1965)proposed wedge
osteotomy and vertical shortening of the chin.osteotomy and vertical shortening of the chin.
• Hinds and Kent(Hinds and Kent(1969) realize the importance of maintaining1969) realize the importance of maintaining
the soft tissue attachment along the inferior segment and thethe soft tissue attachment along the inferior segment and the
role of these attachments in achieving maximal soft tissuerole of these attachments in achieving maximal soft tissue
changechange.

20. CHIN CLASSIFICATION:
• Guyuron, et al. have put forth a system to convey abnormalities with the
chin. it can serve as a useful means of documentation.
• Class
• I Macrogenia: horizontal, vertical, combined
• II Microgenia: horizontal, vertical, combined
• III Combined: horizontal macro/ vertical microgenia, horizontal
microgenia/vertical macrogenia
• IV Asymmetric: a) short, b) normal, c) long anterior facial height
• V Witch’s Chin: soft tissue ptosis
• VI Pseudomacrogenia: normal bony volume with excess soft tissue volume
• VII Pseudomicrogenia: normal bone volume with retrogenia secondary to
excessive maxillary growth and clockwise rotation of mandible
• VIII Iatrogenic malposition
• Guyuron B, Michelow BJ and Willis L: Practical classification of chin
deformities. Aesthetic Plast Surg 19: 257, 1995.

21. Types of genioplasty
•Osseous genioplasty
•Alloplastic genioplasty
Incisions
•Intraoral- labial sulcus incision
•Extraoral- submental incision

22. • Types of osseous genioplasty
• Horizontal osteotomy with advancement
• Horizontal osteotomy with AP reduction
• Tenon technique
• Double sliding horizontal osteotomy
• Vertical reduction genioplasty
• Vertical augmentation
• Alloplastic genioplasty- different types of alloplast
• Hydroxy apatite
• Silastic
• Hard tissue replacement

24. Horizontal Osteotomy
with Advancement

25. Horizontal Osteotomy with
Advancement

27. Double Sliding Horizontal
Osteotomy

28. Overlapping Genioplasty

29. Horizontal Osteotomy with
Anteroposterior Reduction

30. Tenon Technique---Michelet and
associates 1974.
• The tenon technique allows for mortising of the tenon into the mobilizedThe tenon technique allows for mortising of the tenon into the mobilized
fragment when the chin is advanced. In the setback procedure, the tenonfragment when the chin is advanced. In the setback procedure, the tenon
is reversed and the mobilized fragment is mortised into the mandibleis reversed and the mobilized fragment is mortised into the mandible.

31. Transverse deformities of chin
• Transverse deficiencyTransverse deficiency
• Transverse excessTransverse excess
• Asymmetry of chinAsymmetry of chin

32. Widening/narrowing of
chin

33. Correction of mandibular
asymmetry
Transverse sliding osteotomy

34. sliding Double lateral
osteotomy

35. Oblique sliding wedge
ostectomy

36. Vertical Reduction Genioplasty
• vertical height changes can be obtainedvertical height changes can be obtained duringduring
advancement or setbackadvancement or setback by altering the angle of theby altering the angle of the
osteotomyosteotomy..
• Approximately 3 to 5 mmApproximately 3 to 5 mm
• If it is desirable to greatly shorten the chin with orIf it is desirable to greatly shorten the chin with or
without AP change, a wedge reduction is indicated.without AP change, a wedge reduction is indicated.
• This can be accomplished using the tenon technique,This can be accomplished using the tenon technique,
as well as horizontal osteotomy.as well as horizontal osteotomy.

37. Wedge vertical reduction ostectomy allows for anteroposterior
repositioning in addition to (B) vertical shortening.

38. Technique to increase chin height

39. Vertical Augmentation
IndicationIndication
to increase the lower facial height, especially when theto increase the lower facial height, especially when the
deficit is in the mandibular alveolus or symphysis.deficit is in the mandibular alveolus or symphysis.
• accomplishedaccomplished by interpositional grafting or alloplasticby interpositional grafting or alloplastic
implantimplant place­ment between the osteotomizedplace­ment between the osteotomized
segments following horizontal osteotomy of thesegments following horizontal osteotomy of the
mandible.mandible.
• Autogenous bone and hydroxyapatite are the mostAutogenous bone and hydroxyapatite are the most
commonly used materials. It is also possible to make APcommonly used materials. It is also possible to make AP
changes, if desiredchanges, if desired

40. Alloplastic Augmentation
• The use of alloplasts affords the possibility of notThe use of alloplasts affords the possibility of not
only AP augmentation but also vertical and,only AP augmentation but also vertical and,
more importantly, lateral augmentation.more importantly, lateral augmentation.
• TheThe drawbacks of osseous genioplastydrawbacks of osseous genioplasty includeinclude
the possibility of asymmetric advancement,the possibility of asymmetric advancement,
inadvertent vertical changes, and narrowing ofinadvertent vertical changes, and narrowing of
the anterior mandible with large advancements.the anterior mandible with large advancements.
• The use of alloplasts with lateral extensions canThe use of alloplasts with lateral extensions can
eliminate this problem.eliminate this problem.

41. •Alloplasts are still somewhatAlloplasts are still somewhat
controversialcontroversial, in that they have been, in that they have been
associated with underlying bony re­associated with underlying bony re­
sorption, postoperative infection,sorption, postoperative infection,
and nonin­fectious inflammatoryand nonin­fectious inflammatory
responses.responses.
•A variety of surgical techniques canA variety of surgical techniques can
be used for the insertion of anbe used for the insertion of an
alloplastalloplast

42. • Place­ment through the submental fold can be combined withPlace­ment through the submental fold can be combined with openopen
lipectomy or liposuctionlipectomy or liposuction.. IntraoralIntraoral surgical approaches include asurgical approaches include a
vestibular incisionvestibular incision as previously described or a midline verticalas previously described or a midline vertical
incision with a tunneling technique.incision with a tunneling technique.
• Great care must be taken when using limited­access incisions toGreat care must be taken when using limited­access incisions to
ensure symmetric placement of the implant, in addition toensure symmetric placement of the implant, in addition to
appropriate positioning in a vertical plane.appropriate positioning in a vertical plane.

43. • Implants can be used to lengthen the anteriorImplants can be used to lengthen the anterior
mandibular dimension by extending them below themandibular dimension by extending them below the
anterior mandibular border, as well as to augmentanterior mandibular border, as well as to augment
the parasymphyseal region to a greater extent thanthe parasymphyseal region to a greater extent than
the single-piece osseous genioplasty.the single-piece osseous genioplasty.
• Implants should be stabilized with transosseousImplants should be stabilized with transosseous
wires or position screws to ensure immobility.wires or position screws to ensure immobility.
• Bony resorption under alloplastsBony resorption under alloplasts has been seen inhas been seen in
patients with hyperactive mentalis muscles and lippatients with hyperactive mentalis muscles and lip
incompetence.incompetence.
• Great care should be taken to diagnose theseGreat care should be taken to diagnose these
problems before implant placement to avoid futureproblems before implant placement to avoid future
complications.complications.

44. • Augmentation using implants
• Autologous - Calvarial bone
• Metals - Corrosive & High rate of bone erosion
• Polymers – most commonly used

45. • Polymers – carbon chain based molecules with
crosslinking
• Dimethylsiloxanes Silicone based Silastic○ ○
• Polyamide Supramid○
• Polyethylene (polyester fiber) Mersilene (Polyethylene○
terephthalate) Dacron Medpor (porous polyethylene)○ ○
• Expanded polytetrafluoroethylene (PTFE) Gore-Tex Avanta○ ○
• PTFE Teflon Proplast I and II○ ○
• Polymethylmethacrylate (PMMA) Silicone chin implants
• Composite polymer implants
• Hard Tissue Replacement (HTR) PMMA +○
polyhydroxyethylmethacrylate and calcium hydroxide
• Hydrophilic outer layer for osseointegration
• Silastic implant with Dacron backing Increase interface soft○
tissue ingrowth

49. Soft Tissue Closure
• Redistribution of soft tissues may cause chinRedistribution of soft tissues may cause chin
ptosis if at least a two-layer closure is notptosis if at least a two-layer closure is not
performed. It is essential that the mentalisperformed. It is essential that the mentalis
muscle be accurately reapproximate.muscle be accurately reapproximate.
• In general, the incision should be closed in twoIn general, the incision should be closed in two
to three layers and a pressure dressing appliedto three layers and a pressure dressing applied
to minimize hematoma formation and facilitateto minimize hematoma formation and facilitate
soft tissue reattachmentsoft tissue reattachment

50. Soft Tissue Changes
• Soft tissue changes associated with genioplastySoft tissue changes associated with genioplasty
are highly variable.are highly variable.
• Reports in the literature range from 0.6:1 to 1:1Reports in the literature range from 0.6:1 to 1:1
change in soft tissue compared with bonychange in soft tissue compared with bony
advancement/setback or implant thickness.advancement/setback or implant thickness.
• Vertical and horizontal reduction genioplastyVertical and horizontal reduction genioplasty
appears to have the most variability in osseousappears to have the most variability in osseous
to soft tissue change.to soft tissue change.

51. • Several surgical considerations will ensure a greater and moreSeveral surgical considerations will ensure a greater and more
stable magnitude of bone-to-soft tissue change; the moststable magnitude of bone-to-soft tissue change; the most
important appear to be limited periosteal stripping and meticulousimportant appear to be limited periosteal stripping and meticulous
layered soft tissue reapposition, including reconstruction of thelayered soft tissue reapposition, including reconstruction of the
mentalis muscle.mentalis muscle.

52. Complications
• Prolonged neurosensory disturbanceProlonged neurosensory disturbance
• Avascular necrosis of mobilized segmentsAvascular necrosis of mobilized segments
• Hemorrhage causing lingual hematomaHemorrhage causing lingual hematoma
• Possible airway compromisePossible airway compromise
• Unaesthetic soft tissue changes such as chin ptosisUnaesthetic soft tissue changes such as chin ptosis
• Excessive lower tooth displayExcessive lower tooth display
• Bony resorption under alloplastsBony resorption under alloplasts
• Devitalization of teethDevitalization of teeth
• Mandibular fractureMandibular fracture
• Creation of mucogingival problemsCreation of mucogingival problems
• Asymmetry, andAsymmetry, and
• An unaesthetic end resultAn unaesthetic end result

53. References
•Fonseca vol –IIFonseca vol –II
•Johan P Reyneke – Essentials of orthognathic surgery