8. mandibular orthognathic procedures(113) Dr. RAHUL TIWARI

Good Morning

Mandibular OrthognathicProcedures

Presenter-Dr. Rahul Tiwari

Final Yr MDSOMFS, SIDS

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CONTENTS • Introduction

• Surgical anatomy

• Revascularisation & healing of

orthognathic surgical procedures

• Classification

• Surgical procedures

• Ramus osteotomies

• Body osteotomies

• Symphysis osteotomies

• Soft tissue changes after mandibular orthognathic procedures

• Complications of mandibular orthognathic surgeries

• References

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• Orthognathic in Greek Orthos- straight ; Gnathos- jaw

• Orthognathic surgery refers to surgical procedures designed to correct jaw deformities

• Orthognathic procedures are divided into three categories:• Maxillary surgery• Mandibular surgery• Bimaxillary procedures

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• Indications to orthognathic surgery

• Impaired mastication• Temporomandibular pain • Dysfunction• Sleep apnea • Susceptibility to caries and periodontal

disease• Unaesthetic appearance

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• Once growth has ceased, the combination of

orthognathic surgery with orthodontics, usually becomes the only means of correcting severe dentofacial deformities

• In severe malocclusion there are three possibilities for correction: • Growth modification• Orthodontic treatment• Orthognathic surgery in conjunction with

orthodontics to establish proper jaw relationship

• Orthognathic surgery was originally developed in the United States of America (Steinhäuser ).

• The first mandibular osteotomy is considered to be Hullihen´s procedure in 1849 to correct anterior open bite & mandibular dento alveolar protrusion with an intraoral osteotomy.

• Osteotomy of the mandibular body for the correction of mandibular horizontal excess was performed by Vilray Blair.

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HISTORY

• Berger (1897) described a condylar osteotomy for the correction of prognathism.

• Limberg in 1925 first reported the subcondylar osteotomy as an extraoral technique, later it was modified to the intraoral vertical subcondylar osteotomy.

• A variation of the vertical subcondylar osteotomy was suggested by wassmund in 1927,which is similar to the inverted –L-osteotomy.



• Hofer in 1936 demonstrated an anterior mandibular alveolar osteotomy to advance anterior teeth in correction of a mandibular dentoalveolar retrusion.

• In 1954, Caldwell and Letterman developed a vertical ramus osteotomy technique, which had the advantage of minimizing trauma to the inferior alveolar neurovascular bundle.

The greatest development in osteotomies of the vertical ramus is the sagittal split osteotomy credited to obwegeser in 1955. The major modifications in the osteotomies design were first made by Dalpont in 1961.This was further discussed by Hunsuck in 1968 in order to decrease the trauma to overlying soft tissues.

Kent & Hinds in 1971 initially presented the use of single tooth osteotomies of the mandible.Macintosh closely followed with his description of the total mandibular alveolar osteotomy in 1974.



Aesthetics

Function

Stability

AIMS OF MANDIBULAR OSTEOTOMIES

• Patient’s perception of the deformity and expectations

• Surgeon’s recognition of the deformity

• Complete physical examination, model surgery, cephalometric analysis

• Optimal treatment plan

• Counseling of the patient

• Informed consent05/03/2023

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PRINCIPLES IN TREATING MANDIBULAR DEFORMITIES

Vascular

structures

NervesMuscles


ANATOMICAL & PHYSIOLOGICAL CONSIDERATIONS OF MANDIBULAR

OSTEOTOMIES

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Surgical Anatomy

Bell and Levy’s work {1970} demonstrated that blood flow through the mandibular periosteum could easily maintain a sufficient blood supply to the teeth of a mobile segment, even when the labial periosteum was degloved.

subapical osteotomies need to be carefully planned to ensure as large a vascular pedicle as possible.


VASCULAR STRUCTURES

The proximal segment of the vertical sub sigmoid osteotomy maintains its blood supply through the temporomandibular joint capsule and the attachment of the lateral pterygoid muscle.

But the inferior tip of this fragment has undergone vascular necrosis in some studies.

This led to the suggestion that fewer problems may occur if the cut was made above the angle of the mandible.


We should minimize the periosteal and muscle attachment stripping on the medial surface of the proximal fragment with either the C or L osteotomy or any of their variations.

The greater distance from the apices of the teeth not only minimizes direct pulpal injury but increases the vascular pedicle to the mobile segment as well.


NERVES

• In most cases in orthognathic surgery avoiding injury to marginal mandibular branch of facial nerve is achieved because soft tissue anatomy in patients undergoing the surgery has not been disturbed by disease or trauma.

• The course of the inferior alveolar nerve into the vertical ramus and then through the body of the mandible makes it extremely susceptible to damage from almost every mandibular surgical procedure.

• Main goal – “To minimize the trauma because its avoidance is impossible”


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MUSCLESOrthognathic surgery affects muscles in

primarily two ways:

• It changes the length of a muscle or it changes the

direction of muscle function.

• The muscles commonly discussed in orthognathic

surgery of the mandible have been the muscles of

mastication and the suprahyoid group of muscles .

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• A- S to lingula - 14.8 +/-

2.90 mm• C- S to mandibular foramen

– 21.6 +/- 3.31 mm

• B- Horizontal distance from lingual to anterior border of ramus –

17.7 +/- 2.89 mm• D- Mandibular foramen to

ramus – 18.6 +/- 2.49 mm

Int. J. Oral Maxillofac. Surg, 2008

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• At a distance between 7.5

to 13.3 mm above the lingula

Buccal and lingual cortex fusion occurs at a rate of • 20% in the anterior ramus• 39% in the posterior ramus

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• The position of the lingula is posterior-inferior relative to the position of the antilingula

• Any osteotomies performed at a measurement of 5 mm posterior to the antilingula (at the level of the antilingula)- no risk of damaging the neurovascular bundle

Accuracy of Using the Antilingula as a Sole Determinant of Vertical Ramus Osteotomy Position . J Oral Maxillofac Surg,

2007

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Position of IAN at

second molar• Bone thickness from

mandibular canal to buccal plate- 7.2 +/- 1.47 mm

Int. J. Oral Maxillofac. Surg, 2008

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Tsuji et al, Int. J. Oral Maxillofac. Surg, 2005

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• PATTERNS OF ANTERIOR LOOP OF MENTAL NERVE

J Oral Maxillofac Surg, 2007

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Revascularisation & Healing

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• Blood flow is crucial for revascularisation and healing

• Blood flow will be decreased in the areas where the mucoperiosteum will be elevated

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• Immediate post-operatively

• Intermedullary circulation between the proximal and distal segments

• Margins of osteotomy- avascular

• One week post-op• Level of hypervascularity around surgical

site• No soft tissue re-attachment• Isolated areas of sub- periosteal bone

formation

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• 2 weeks post-op

• Avascular zone at the proximal osteotomy site • Necrotic zone at the distal osteotomy site• No soft tissue attachment at the distal

necrotic zone

• 3 weeks post-op• Soft tissue re-attachment • Vascular anastamoses between proximal and

distal segments • Osteoid formation through out marrow

formation

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• 6 weeks post-op

• Circulation reconstituted across the osteotomy site

• Soft tissue re- attachment established

• 12 weeks post- op• Circulation between the segments is

continuous

CLASSIFICATION


MANDUBULAR ORTHOGNATHIC PROCEDURES

BODY

OSTEOTOMIES

SUB APICAL OSTEOTOMIES

RAMUS OSTEOTOMIES

HORIZONTAL OSTEOTOMY

OF CHIN

SAGGITAL SPLITOSTEOTOMY

VERTICAL RAMUS

OSTEOTOMY

INVERTED “L” &“C” OSTEOTOMY

ANTERIOR SUB APICAL

OSTEOTOMIES

POSTERIOR SUB APICAL

OSTEOTOMIES

TOTAL SUB APICAL OSTEOTOMIES

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Bilateral Saggital Split Osteotomy

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• First described in 1942 by Schuchardt in German literature

• Most widely used surgical procedure for correcting mal- positioned mandible

• It has been modified in many ways, but for longer than 50 years, benefits and advantages of the procedure have remained unchanged

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• Versatility of the procedure allows wide application

• It increases the range of possible movements compared with orthodontic treatment alone

• Broad bony overlap of the separated fragments allow not only advancement or setbacks of the distal tooth- baring mandible, but also rotations

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• A. Trauner & Obwegezer, 1957

• B. Dal pont, 1961

• C. Hunshuck, 1968

• D. Epcker, 1977

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• Bell and Schendel established the

biological basis for BSSO

• Minimal detachment of the pterygomassetric sling there is decreased intra- osseous ischemia, and necrosis of the proximal segment

• 1976, Spiessel advocated rigid internal fixation of BSSO to promote primary healing, restore early function, and attenuate relapse

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Indications

• Mandibular deficiency• Advancements beyond 10- 12 mm, extra oral

approach should be considered

• Mandibular prognathism• Large setbacks of more than 7 -8 mm, IVRO/

inverted L osteotomy should be considered

• Mandibular asymmetry

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Surgical Procedure

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ADVANTAGES

• Broad bony overlap of

osteotomised segments

• Minimal alteration of natural

position of muscles of mastication

• Minimal alteration in position of

TMJ

• Short operating time and low

complication rate

DISADVANTSGES

• Requires additional

maxillary surgery for most

dentofacial deformities

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Osteosynthesis

• Post- operative fixation of the osteotomised segments was once a great challenge

• Initially, No fixation of the fragments Healing- intermaxillary splinting of the teeth

• Introduction of wires for fixation

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• Major breakthrough- development of “stable compression osteosynthesis”-

Spiessl in 1974

• The degree of immediate postoperative stability achieved with this technique completely obviated the need for intermaxillary fixation

• Wide variety of methods and materials for fixation are available

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• Initially the use of three 2.7 mm “lag” screws on each side was advocated

• Concern • Compression may cause increased nerve

damage • Displacement of the condyles, with

subsequent temporomandibular joint dysfunction

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• The position screw or bicortical screw

This technique permits maintenance of the gaps between the proximal and distal fragments, with no compression of the two segments together

• Osteosynthesis with miniplates• 4- holed plate with 2screws on each side of

the osteotomy cut

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• Resorbable screws• Obvious advantage of resorbable fixation is

to obviate the need for future hardware removal

• 4 screws have to be placed on each side of the mandible

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Vertical Ramus Osteotomies

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• 1st described by Caldwell and Letterman in 1954- extra oral

• Introduced by Moose in 1964- intra-oral technique performed from lingual aspect

• Wistanley, 1968- performing the technique from the lateral aspect of the mandible

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Comparison between SSRO and VRO

SSRO VROOSTEOTOMY PA Saggital split Latero medial cut

Open procedure Blind procedureAlong IAN Rear to IANFrequent exposure of IAN

No exposure of IAN

BONE HEALING Contact on marrow to marrow

Contact on cortex to cortex

BONE FIXATION Rigid internal fixation No fixationCONDYLAR HEAD

Original position New equilibrated position

POST OP IMF None or shorter period Required PROGNOSIS Weakely dependent on

PTStrongly dependent on PT

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Indications

• Horizontal mandibular excess

• Mandibular asymmetry

• Minor occlusal discrepancy after

isolated Le Fort I osteotomy

• Asymmetric lateral open bite

• Failure to achieve passive rotation

of the mandible after the release of

MMF

• Patients with significant TMJ

complaints

Contraindications

• Advancement of the distal

segment

• Aesthetic assessment of the soft

tissues of the neck is the integral

factor in planning mandibular

set back by ramus surgery

• Recent condylar fractures

• Should be differed for 6-12

months

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ADVANTAGES

• Can be performed on OPD basis

• Inherent anatomic architecture of the

mandible poses little interference to

place the cuts

• Less chance of damaging the IAN

bundle

• Found to have curable effects in pts

with pre-op TMD

• Less incidence of condylar sag

DISADVANTSGES

• Need for MMF

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• IMF-7-10 days .elastic traction-4-5 weeks

• Rigid fixation-uncommonly used because of• Technical difficulty• Increased operation time• Good results with wire fixation or IMF

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Bony interference

• Occurring between the overlapped proximal and distal segments- causing a backward rotation of the of the proximal segment• If interference is not

reduced- forward skeletal relapse upon IMF release

• Contact between the condyle and coronoid

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Inverted L/C Osteotomies

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• These are designs in the vertical ramus that include both the condyle and coronoid in the same segment

• Most commonly done via an extraoral approach

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• Indications

• Large advancements >12mm• Mandibular setback -10mm or more-bypasses the

need for coronoidectomy• Secondary correction of proximal segment

malrotation following BSSO• Simultaneous advancement and lengthening of ramus

in case of severe ramus under development.

• Less risk of condylar sag compared with VRO

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Vertical Body Osteotomies

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• Blair -1907-as an extra oral procedure

• Dingman –combination of extraoral and

intra oral access

• Now contemplated only as an intraoral

procedure.

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Indications

• Mandibular setback• Mandibular prognathism with ramus procedure.• Mandibular prognathism where long body in

relation to ramus

• Anterior open bite closure• Curve of spee reduction• Progenia correction

• In class III-anterior body osteotomy –wedge of bone removed and set back

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Pitfalls

• Anatomic discrepancies leading to reduction in bone to

bone contact

• Segment control

• Torquing of the proximal segments is the classic

problem

• Root anatomy is variable

• Difficult to perform osteotomy in the premolar

region when trying to skrit the mental nerve and

root of the 1st premolar

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Sub-apical Osteotomies

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ANTERIOR MADIBULAR SUB-APICAL OSTEOTOMY

• Earliest referenced description of symphyseal osteotomies was by Trauner in 1952

• Aids in correction of dentofacial deformities.

• When combined with AMO non skeletal open bite or bimaxillary protrusion can be corrected

• Useful to level the plane of occlusion with out decreasing the vertical facial height

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Complications

• Loss of bone or teeth in osteotomised segment.(lingual tissues not protected-decrease in blood supply)

• Bone cuts placed close to the teeth-loss of vitality and periodontal defects

• Mental nerve paresthesia-directly related to the amount of trauma

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Posterior Subapical Osteotomy

• First described by- Peterson Indications

• Correction of super eruption of posterior mandibular

teeth

• Ankylosis of one or more posterior teeth

• Abnormal buccal or lingual position of these teeth

especially if orthodontics is not feasible

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Total Mandibular Subapical Osteotomy

• Oldest procedures used to correct Jaw Deformity.

• Described by HULLIHEN in 1849.

• Popularised by Hofer and Koele.

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• Primary indication Malocclusion caused by

Mandibular Dentoalveolar deformity with normally positioned Maxilla and Mandibular skeletal bases

• Bell concluded that horizantal osteotomy be completed 0.5cm or more from the apices of teeth in order to preserve pulpal circulation.

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Horizontal Osteotomy of the Symphysis

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• Facial features often form a basis for stereotyping of personality charecteristics

• Chin is most prominent facial feature

• Chin deformities can manifest in 3 dimensions but majority are in the horizontal direction

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• Horizontal sliding osteotomy-first described by Hofer in 1942-through extra oral approach.

• Trauner and Obwegeser-1957- horizontal osteotomy through an intra oral incision.

• Reichenbach-1965-wedge osteotomy and vertical shortening of the chin.

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Types Of Genioplasties

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Double Sliding Horizontal Osteotomy

• Indication- severe chin deficiency

• Surgical technique involved-creation of a stepped intermediate wafer between the inferior fragment and mandible.

• Inferior fragment also advanced to provide bony contact between upper and lower fragments.

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Propellar Genioplasty

•

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Saggital Splilt Genioplasty

Sagittal Split Genioplasty: A New Technique . J Oral Maxillofac Surg, 2010

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Transverse Reduction Genioplasty

Transverse Reduction Genioplasty to Reduce Width of the ChinJ Oral Maxillofac Surg, 2010

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Chin Sheild Genioplasty

Chin shield osteotomy – a new genioplasty technique avoiding a deep mento-labial fold in order to increase the labial competence . Int. J. Oral Maxillofac. Surg, 2009

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M- Shaped Genioplasty

M- shaped genioplasty: new surgical technique for vertical and saggital chin augmentation: 3 case

reports J Oral Maxillofac Surg, 2012

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Soft Tissue Changes After Mandibular Orthognathic

Procedures

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• The major goal of orthognathic surgery is the establishment of a balanced and stable dentoskeletofacial complex

• Most important aspect- achieving aesthetically pleasing facial soft tissue envelope

• Ability to predict soft and hard tissue changes before an orthognathic surgical procedure is critical to treatment planning

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• Change in soft tissue morphology after orthodontics + surgery depends upon

• Method of wound closure• New spatial arrangement of skeletal and

dental elements• Adaptive qualities of soft tissues • Vector of tooth movement• Lip thickness, tonicity, lip area, competence,

strength, postop oedema, etc.

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Anterior Repositioning• Little change in upper lip &

none above ANS

• Variable advancement in lower lip, it often lengthens

• Lower labial sulcus & chin adhere to bone, so advance more than lower lip-opening of labiomental fold

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Posterior Repositioning

• No effect on subnasale or the tissues superior to subnasale

• Slight posterior displacement of upper lip, with lengthening can occur

• Slight increase in nasolabial angle• Soft tissues follow the mandible posteriorly, with

chin following most closely, followed by inferior labial sulcus

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Autorotation

• During autorotation of mandible, the soft tissues follow the osseous landmarks on approximately 1:1 basis

• But lower lip falls slightly lingual to arc of rotation

• Slight increase in labiomental angle

• Slight thickening of lower lip

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Soft Tissue Changes After Genioplasty

• The soft tissue changes depend on magnitude & direction of positional change of the genial segment, design of mucosal & osseous incisions, amount of soft tissue stripping, & other concomitant jaw movements

• Advantage of genial surgery is preservation of normal tissue contour

• Vertical reduction allows larger soft tissue advancement

Anterior repositioning

• Majority of change is in soft tissue of chin; less effect is in labial sulcus &

lower lip

• Soft tissue follow hard tissue without chin droop

• Small but negligible effect on labiomental sulcus

• Increase in submental length

• Improved lower lip to tooth relationship

• Less soft tissue thinning

• Improved neck chin angle

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Posterior repositioning

• Little improvement in profile

• Soft tissue changes are little correlated with hard tissue movements (than with advancement)

• Contraindicated in patient with minimal or no labiomental fold

• Undesirable changes in neck chin proportion

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COMPLICATIONS

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• Surgical relapse to varying degree can

occur after mandibular surgery

• Complications in orthognathic surgery• Pre-operative phase • Intra-operative phase • Post-operative phase

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PRE-OPERATIVE PHASE

• Limitations on surgical movement- failure to eliminate dental compensations

• Molar root fenestrations, transverse surgical relapse- Failure to manage transverse discrepancy

• Immpossibilility in achieving class I cusp relation, overjet and over bite- failure to indentify and manage tooth size discrepancies

• Root damage during osteotomies- failure to properly level and achieve root divergence in segmental cases

• Psychological preparation of the patient

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INTRA-OPERATIVE PHASE

• Attributed to improper surgical technique and/or failure to appreciate patient’s anatomy

• Unanticipated intra-op complications are not unheard of

• Can be categorised into• Unfavourable osteotomy splits• Nerve injury• Bleeding• Proximal segment malpositioning• Miscellenaeous

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Sagittal Split Ramus Osteotomy

UNFAVORABLE OSTEOTOMY SPLIT • Incidence- 18%

Bad split

Abort the procedure& perform after healing

Correct the split &Complete the procedure

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Proximal segment fracture• Also called “Buccal plate fracture”• Most frequent

• Presence of impacted 3rd molar• Recent removal of 3rd molar• Age of the patient• Incomplete transection of the inferior border • Surgeon’s experience

• # of distal segment occurred more often in young people with impacted 3rd molars

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• Role of impacted 3rd molars in unfavorable # is debatable• Advocated removal 6months prior surgery

Fracture of coronoid process• Occurs when the horizontal cut is placed

too high where the ramus is thin

• Fracture of distal segments• Inferior border remains attached to distal

segment

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NERVE INJURY

• Damage can occur at many points

• When nerve was transected- usually in 3rd molar

region or anterior to it

• Higher incidence of neurosensory disturbance

with bicortical screws than monocortical screws

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BLEEDING • Incidence decreased from 38% in 1972

to 1% in 2005

• Most common sources• Maxillary artery and its branches (massetric

and inferior alveolar artery)• Retromandibular vein• Facial artery and vein

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PROXIMAL SEGMENT MAL-

POSITIONING• Counterclockwise rotation and condylar

distraction are frequent positional changes in proximal segment

• MINOR DIFFICULTIES• Herniation of buccal fat pad• Difficulty in incision closure • Breaking of bur

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Vertical Ramus Osteotomy

UNFAVOURABLE OSTEOTOMY

• Inadvertent subcondylar osteotomy

• More likely in

• Prognathic mandible with high mandibular

plane angle and ill- defined gonial angle

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NERVE INJURY

• Incidence ranges from 0%- 14%• Less incidence when compared to SSO

• Can occur in 2 phases• If osteotomy is close to mandibular foramen• Medial displacement of the proximal

segment compressing and tearing the nerve

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BLEEDING• Common source- maxillary artery and

its branches

PROXIMAL SEGMENT MALPOSITIONING

• Control of proximal segment- major disadvantage• May be displaced antero- medially, anteriorly

towards articular eminence or can be displaced medially and inferiorly

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Sub- Apical Osteotomies

• Nerve injury• Damage to teeth roots• Non- vitality of teeth • Mal-positioning of mobilised segments

• Inadequate trimming, inadequate bone removal

• Difficulty in stabilisation

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Genioplasty

UNFAVOURABLE OSTEOTOMY• Inadvertent # of body and ramus• Damage to teeth roots

NERVE INJURY• Mental nerve is commonly injured

• incision, reflection and retraction, osteotomies, plating or closure

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• BLEEDING• Damage to lingual soft tissues

• Injury to genioglossus, geniohyoid muscles • Laceration of sublingual and submental

arteries

• Usually not life threatening• Managed by local measures

COMPLICATIONS

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POST-OPERATIVE PHASEEARLY POSTOP

• Excessive swelling • Haemorrhage &

Haematoma • PONV • Neurological

dysfunction• Mandibular

dysfunction• Hypomobility, reduction

in bite force, TMJ dysfunction

• Relapse

Genioplasty

Neurological

dysfunction

Chin asymmetry

Uneven mentalis

muscle contraction

Chin ptosis

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LATE POST-OP

• Long term neurological dysfunction• TMJ dysfunction• Dental and periodontal problems

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• CONDYLAR SAG• Immediate or late caudal movement of condyle in

the glenoid fossa after surgical establishment of the preplanned occlusion and bone fragments leading to change in the occlusion

• Types –• Central• Peripheral

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Central condylar sag

Bilateral

Unilateral

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Peripheral condylar sagType I

Peripheral condylar sagType II

Bilateral

Unilateral

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REFERENCES

• Maxillofacial Surgery-Peter Ward Booth

• Principles Of Oral And Maxillofacial Surgery- Peterson

• Oral And Maxillofacial Surgery-Fonseca

• Essentials Of Orthognathic Surgery-Reyneke

• Chin shield osteotomy – a new genioplasty technique avoiding a deep mento-labial fold in order to increase the labial competence Int. J. Oral Maxillofac. Surg, 2009

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• Transverse Reduction Genioplasty to Reduce Width of the Chin J Oral

Maxillofac Surg, 2010

• Sagittal Split Genioplasty: A New Technique J Oral Maxillofac Surg,

2010

• M- shaped genioplasty: new surgical technique for vertical and saggital

chin augmentation: 3 case reports J Oral Maxillofac Surg, 2012

REFERENCES

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THANK YOU

Health & Medicine

8. mandibular orthognathic procedures(113) Dr. RAHUL TIWARI