Presentation on mandibular osteotomy procedures by Dr.G.Kathirvel M.D.S (OMFS).,

1. MANDIBULAR OSTEOTOMIES
DR.KATHIRVEL
PG - OMFS

2. CONTENTS:
• INTRODUCTION
• SURGICAL ANATOMY OF MANDIBLE
• PRE OP ASSESSMENT
• ARMAMENTARIUM
• TECHNIQUES
• SUBAPICAL OSTEOTOMY
• GENIOPLASTY
• BODY OSTEOTOMY
• RAMUS OSTEOTOMY
• COMPLICATIONS
• RECENT ADVANCES

3. MANDIBLE
A horse shoe shaped bone which forms the lower jaw
Articulates with the temporal bones by a synovial joint the temperomandibular joint
THE BODY OF MANDIBLE
EXTERNAL SURFACE
INTERNAL SURFACE
UPPER OR ALVEOLUS
LOWER OR BASE

4. INTERNAL SURFACE
Mandibular foramen:
• Just posterior to halfway between the anterio-posterior width
of the vertical ramus.
• Mandibular neurovascular bundle enters the mandibular
foramen on the lingual side of the mandible and runs below the
tooth roots in the body of the jaw, in the inferior alveolar
canal.
Lingula:
• Just above mandibular foramen
• The sphenomandibular ligament is attached.

5. Lingula:
Four possible shapes – triangular, truncated, assimilated or nodular
The mandibular foramen is situated infero-posteriorly to the lingula, approximately at the vertical level of
a straight line following the upper border of the alveolar process.
The lingula was consistently located approximately half-way on the medial side of the ramus, and in the
upper third between the sigmoid notch and antegonial notch
Location:
17.0±2.2 mm from the external oblique
17.2±2.7 mm from the sigmoid notch
15.6 ± 1.9 mm from the posterior border of the mandible

6. • Position of lingula in postero inferior in relation
to position of anti lingula
• Osteotomies performed 5 mm posterior to the
antilingula (at the level of the antilingula)- no
risk of damaging the neurovascular bundle
Aziz SR, Dorfman BJ, Ziccardi VB, Janal M. Accuracy of using the antilingula as a sole determinant of
vertical ramus osteotomy position. Journal of oral and maxillofacial surgery. 2007 May 31;65(5):859-62.

8. Vascular Supply
• Blood flow from the periosteum was considered to be centripetal to distinguish it from the
blood flowing from endosteal vessels outward (centrifugal) that was associated with long
bones.
• Inferior alveolar artery had a primary role in nourishing the mandible,
• Bell and Levy demonstrated that there is also a sufficient blood supply from the surrounding
soft tissues, even if the inferior alveolar artery was compromised.
• The proximal segment of VRO maintains its blood supply through TMJ & capsule and
attachment of lateral pterygoid muscle.
• But inferior tip of this segment undergoes avascular necrosis.
• Tooth devitalization - 5 mm is an adequate guideline.

9. Nerves
• The marginal mandibular branch of the seventh cranial nerve
• The third division of the trigeminal nerve and most frequently the IAN.
Marginal mandibular branch:
• Is usually at risk only during extraoral procedures.
• Avoiding damage to this nerve during extraoral approaches to the mandible is a major
surgical goal

10. Medio-lateral position of the mandibular canal
The extension of the sagittal osteotomy cut into the
first molar area is favoured
Reasons :
• The buccal cortical plate is thicker
• Distance between the inner aspect of the buccal
cortical plate and mandibular canal is
consistently greater in this area
• First molar and second bicuspid area – most
favourable area for extension of sagittal osteotomy
Rajchel J, Ellis E, Fonseca R: The anatomical location of the mandibular canal: its relationship to the sagittal split
ramus osteotomy; Int J Adult Orthognath Surg 1986; 1: 37-47

11. • Fusion of cortical plates frequently occurs very near the
superior tip of the lingula and posterior to the lingula
mean length of horizontal cut should be 18mm – So
medial cut should be just above lingula
• Confirmed that the buccal plate is thickest at the lateral
oblique ridge, very favourable for screw placement
Mandibular Ramus Anatomy as It Relates to the Medial Osteotomy of the Sagittal Split Ramus Osteotomy; Smith B,
Rajchel J, Waite D, et al: JOMS 1991;49:112

12. Cephalometric Analysis of mandible
A. By size
1. Ramus height
2. Body length
B. By position
1. SNB
2. N perpendicular to point B
C. Orientation
1. Angle of the mandible
2. Mandibular plane angle

13. Measure by Size
Ramus Height (Ar-Go)
Distance between the Articulare and the Gonion is measured to
determine the length of the ramus.
Normal values: Males—52 mm ± 4.2 Females—46.8 mm ± 2.5
Mandibular Body Length (Go-Gn)
It is the distance between the Gonion and the Gnathion.
An increase in this value denotes increased length of the body of the
mandible, and vice versa.
Normal values: Males—83.7 mm ± 4.6 Females—74.3 mm ± 5.8

14. Measurement by Position
SNB
It is the angle that the line joining the nasion and the point B makes
with the SN plane .
An increase in SNB indicates forward positioning of the mandible,
and vice versa.
Normal values: 80° ± 2°
N-Perpendicular To Point-B
A perpendicular from the horizontal plane is dropped from the
Nasion point. Then the distance from the Point-B to this
perpendicular is measured to find the positioning of the mandible in
relation to the cranium.
An increase in the value indicates retrusion of the mandible while a
decrease indicates protrusion.
Normal values: Males—5.3 mm ± 6.7 Females—6.9 mm ± 4.3

15. Orientation of the Mandible
Angle of the Mandible
The angle formed between the lines Ar-Go and Go-Gn determines the
angle of the mandible.
An increase in this angle is projected as an increase in anterior vertical
measurement of the mandible, and vice versa.
Normal values: Males—119.1° ± 6.5 Females—122.0° ± 6.9
Mandibular Plane Angle
It is the angle that the mandibular plane makes with the horizontal
plane.
An increase in the angle indicates clockwise rotation of the mandible
resulting in increased lower anterior facial height. On the other hand, a
decrease in this angle is indicative of decreased lower anterior facial
height.
Normal values: Males—23.0° ± 5.9 Females—24.2 ± 5

16. • Mandibular protrusion
a. Skeletal
b. Dentoalveolar
• Mandibular retrusion
a. Skeletal
b. Dentoalveolar
• Mandibular transverse deformity
a. Broad
b. Narrow
• Chin deformity-excess
a. Vertical
b. Transverse
c. Anteroposterior
• Chin deformity-deficient
a. Vertical
b. Transverse
c. Anteroposterior
• Deep bite deformity
• Open bite deformity (Apertognathia)
• Asymmetry
Mandibular deformity classification

17. Mandibular excess:
Clinical features:
1. Prognathic mandible.
2. Anterior cross bite.
3. Elongated face.
4. Relatively long lower third of the face
5. Concave facial profle.
6. Lower lip and chin are more anteriorly placed than normal (SN perpendicular)
7. Class III relationship of occlusion.
8. Angle SNB—more than 82°.

18. Mandibular deficiency:
Clinical features:
1. Bird face appearance.
2. Severe over jet.
3. Class II relationship of dentition.
4. Crowding of lower anterior teeth.
5. Flaring compensation of lower anterior teeth.
6. Face appears small.
7. Lower third of the face is short.
8. Angle SNB—less than 78°.

19. Asymmetry:
1. Hemifacial microsomia/dysplasia
2. Unilateral cleft lip and palate, and other unilateral clefting syndromes
3. Childhood trauma especially to the condyle
4. Early unilateral loss of teeth
5. Faulty use of functional appliances
6. Pathologies and childhood surgeries of the face

20. Osteotomies of the Mandible
1. Dentoalveolar complex
(a) Anterior subapical
(b) Posterior subapical
(c) Total subapical
2. Body osteotomy
3. Genioplasty
4. Ramus Osteotomy
(a) Vertical sub-sigmoid osteotomy—intra- and extraoral
(b) Inverted L and C osteotomy
(b) Sagittal split ramus osteotomy (BSSO)
5. Subcondylar osteotomy

21. Hypotensive Anesthesia:

22. ARMAMENTARIUM
Merrill-levaseur Bauer Nerve hook Smith spreader

23. Anterior Subapical Osteotomy
• Hullihen performed the first ever anterior subapical
osteotomy in 1849
• Hofer used anterior subapical osteotomy to advance
anterior teeth for correction of mandibular
dentoalveolar retrusion.
• Kole used this technique to correct an anterior open
bite.

24. Anterior subapical osteotomy
Indications:
1. To retrude the lower anterior dentoalveolar segment
2. To close minimal anterior open bite
3. To intrude the anterior segment in deep bite deformity

25. Anterior Subapical Osteotomy
PROCEDURE
Incision:
• Begins about 1 cm behind the planned vertical osteotomy and
is carried forward about 4 to 5 mm below the attached
gingiva until reaching the cuspid
Flap elevation:
• The periosteum is elevated, exposing the lateral cortex of the
mandible, with care around the mental foramen as well as
attention paid to leaving soft tissue attachments at the inferior
border to ensure stability of the soft tissue–chin morphology.

26. Osteotomy:
• The vertical osteotomies are made using parallel cuts when the
posterior movement of the segment is planned.
• If parallel horizontal cuts are planned to move the anterior
segment apically, the superior cut is made first.
• The inferior cut is then made, and the segment of bone is
removed
• The horizontal cut at least 5 mm below the tooth apices

27. • After ensuring an adequate seating of the teeth into the
surgical splint, the segment is stabilized by either wiring the
splint to the teeth individually or placing circumferential
mandibular wires that can be combined with IMF.
• Plates and monocortical screws can be used with the splint
• Bone gaps caused by movement of the segment, especially by
vertical movement necessary for the closure of an anterior
open bite, should be grafted.
• The surgical site is then irrigated thoroughly and closed with
resorbable sutures.

28. Posterior Subapical Osteotomy
INDICATIONS
• Correction of supraeruption of posterior mandibular teeth or ankylosis of one or more
posterior teeth.
• Abnormal buccal or lingual positioning of these teeth can also be improved upon with
this technique when orthodontics is not available or feasible.

29. Posterior Subapical Osteotomy
TECHNIQUE:
Incision:
• Begins 3 to 4 mm lateral to the attached gingiva, beginning at the
anterior border of the vertical ramus and carried forward to the
cuspid region.
Flap elevation:
• The periosteum is stripped superiorly and inferiorly sufficiently to
expose the lateral cortex for the planned osteotomies.

30. Osteotomy:
• The vertical cuts are made first through both cortices with a fine
osteotome or thin saws.
• The horizontal cut is carried only through the buccal cortex, and a
thick splitting osteotome is used to complete the osteotomy.
• Care is taken to ensure that the IAN is not caught in the mobile
segment and that appropriate bony adjustments are made to permit
the planned movement.
• The segment is positioned and stabilized with an acrylic splint and
wire.

31. Total mandibular alveolar osteotomy:
• Mcintosh in 1974 described total mandibular alveolar osteotomy.
• In 1942, Hofer described horizontal osteotomy of mandible for horizontal defciency
or excess and asymmetry.

32. Indications:
Dentoalveolar deformity with normally positioned Maxilla and Mandibular skeletal
bases
• To increase the height of the mandible
• To level the occlusal plane

33. Technique
Incision:
• Begins on the external oblique ridge of the base of the vertical
ramus, carried down to bone and extends forward 4 to 5 mm
below the attached gingiva and positioned inferiorly in the region
of the canine and forward where it meets the contralateral incision
at the midline.
Elevation:
• The periosteum is elevated to expose the lateral cortex, with care
taken around the mental nerve, as well as leaving some
attachment at the inferior border of the symphysis for the soft
tissue chin.

34. Osteotomy:
• The vertical cut posterior to the terminal molar is made first and
carried down to the level of the planned horizontal osteotomy.
• As with the step osteotomies, the horizontal cut needs to be placed
appropriately, based upon preoperative periapical radiographs.
• The mobile segment is related to the maxilla with an acrylic
interocclusal splint and IMF.
• Osseous fixation can be achieved either with the lateral cortical
wires placed in the first bicuspid area along with maintaining IMF
or by rigid internal fixation with monocortical plates and screws.

35. GENIOPLASTY
• Genioplasty is a facial balancing procedure in adjunction to assisting with soft tissue
contours and chin-neck enhancement
• Trauner and Obwegeser in 1957, published the first article on intraoral sliding
osseous genioplasty
• In 1942, Hofer first described advancement genioplasty through an external approach
Indications:
To correct Chin deformity - excess and deficient
a. Vertical
b. Transverse
c. Anteroposterior

36. Technique:
Incision:
• Labial vestibule and extends posteriorly to the first bicuspid region and
is carried through the mentalis muscle
Flap elevation:
• The periosteum is elevated inferiorly to a point just below the intended
level of the osteotomy. Laterally, the periosteum is elevated to the
mental foramen and then extended posteroinferiorly to the mandibular
inferior border below the mental foramen bilaterally.

37. Osteotomy:
• It is helpful at this point to inscribe a vertical mark into the bone
across the planned osteotomy site in the anterior mandible so that
the transverse position of the inferior fragment can be more
easily reoriented after completion of the osteotomy.
• The osteotomy cut is then made with a reciprocating saw

38. • The stabilization of the segment in its new position can be done with cortical wires,
circumandibular wires, plates and screws, prebent chin plates
• The wound is irrigated and closed in two layers, mentalis muscle and mucosa, with
resorbable suture.
• Care should be taken to reapproximate the mentalis muscle formally in order to prevent
chin ptosis (“witch’s chin”) postoperatively.
• Elastoplast tape or similar tape, should be placed across the lip and chin to support and
maintain mentalis position, and it is continued for 2 to 5 days to minimize hematoma
formation and to support the suture repair.

39. TYPES OF GENIOPLASTY:
• Augmentation genioplasty
• Reduction genioplasty
•Horizontal sliding genioplasty
Advancement genioplasty
Setback genioplasty
• Vertical genioplasty
• Propeller genioplasty
• Tenon Mortise genioplasty

40. AUGMENTATION GENIOPLASTY
• Here the genial segment is repositioned inferiorly and the defect is
grafted.
• Point to be noted that the amount of vertical increase is predetermined
and then the segment fixated with 2 bone plates

41. REDUCTION GENIOPLASTY
• A predetermined segment of bone is removed from the genial segment.
• The genial segment is repositioned superiorly and fixated

42. Horizontal sliding genioplasty
• The position of the horizontal osteotomy is controlled by the level of the
mental foramen and inferior alveolar canal.
• It is mandatory to position the horizontal osteotomy 3 to 4 mm below the
inferior edge of the mental foramen to prevent injury to the neurovascular
bundle.

43. Advancement genioplasty
• The horizontal osteotomy is performed at least 5 mm below the apex of the
canine root and the mental foramen.
• Advancement genioplasty along a high angle will reduce the height of the
chin, and the opposite will occur with a setback procedure

44. SET BACK
• The horizontal osteotomy is performed at least 5 mm below the apex of the
canine root and the mental foramen.
• For the set back procedure bone plate fixation is the method of choice

45. VERTICAL OSTEOTOMIES:
• For transverse genial deformities, vertical
osteotomies can also be performed.
• This allows widening or narrowing of the
chin.
• In case of widening, additional bone
grafts or alloplastic implants (eg, ceramic
blocks) are needed

46. PROPELLAR GENIOPLASTY
• The facial midline is marked on the superior aspect of the chin, then the first
osteotomy is performed parallel to the lower border of the chin after that the
second osteotomy is performed parallel to the horizontal.
• The bone segment will be rotated by 180 degress

47. TENON MORTISE GENIOPLASTY ( 1974)
The Tenon Mortise functional genioplasty is an osteotomy
of the anterior mandible which reduces excessive
lower anterior facial height .
Surgical technique
• The surgical technique involves creation of a tenon and mortise which not only
preserves the insertions of both the labiomental muscles and at least some of the
suprahyoid muscles but also improves the stability of transosseous fixation.
• Superior repositioning and advancement of the chin and myocutaneous structures
produce both functional and esthetic benefits for the patient.

48. Mandibular body Osteotomies
• Described by Blair in 1907.
• This was one of the earlier procedures used for
mandibular progathism.
Indications:
• Mandibular setback
• In Mandibular prognathism with ramus procedure.
• In Mandibular prognathism where long body in
relation to ramus
• Mandibular advancement- less used

49. Technique:
Incision:
• Made 4 to 5 mm below the level of the attached gingiva and is
carried forward at this level to the cuspid, where it can be dropped
down 5 mm and extended forward to the midline.
Flap elevation:
• The periosteum is elevated inferiorly until the mental foramen is
located and then the remainder of the periosteum is stripped to
expose the area of the osteotomy.

50. Osteotomy:
• The vertical cut through the alveolus is made with either a saw or
a bur.
• A finger should be kept on the lingual aspect of the mandible to
prevent the power instrument from penetrating the mucosa.
• The vertical cuts are carried inferiorly to the level of the planned
horizontal cut, which would be at least 5 mm below the dental
apices.
• The inferior vertical cuts are then made, again using parallel cuts
as necessary for a setback of the distal fragment.
• Finally, the horizontal cut is made, preferably by a saw, to
minimize bone removal and endangering of the apices or the IAN

51. Ramus Osteotomies
History:
• Limberg in 1925 reported subcondylar oblique osteotomy
• In 1927 Wassmund described the inverted “L” osteotomy.
•
• In 1937 Lane described a sagittal osteotomy.
• Obwegeser modifed the Lane’s technique in 1955, and the
technique of sagittal split osteotomy is credited to him

52. Various procedures of ramus osteotomy are :
• Extraoral vertical ramus osteotomy
• Intraoral vertical ramus osteotomy
• Inverted L and C osteotomy
• Saggital split osteotomy

53. Vertical ramus osteotomy
• This was one of the most popular procedures for correcting
mandibular prognathism.
Indications:
• Horizontal mandibular excess
• Mandibular asymmetry
• Minor occlusal discrepancy after isolated Le Fort I osteotomy
• Hall and Mc Kenna later revived this indication for minor (2–3
mm) advancements.

54. Extra-oral vertical ramus osteotomy
Technique:
Incision
• Submandibular with an approximately 4-cm incision made 2 cm
below the angle and the inferior border of the mandible.
• Care is taken to avoid damaging the marginal mandibular branch of
the facial nerve.
• After incising through the periosteum, The lateral aspect of the
ramus is inspected for a small bulge corresponding to the lingula.

55. Osteotomy:
• The osteotomy is performed from superiorly posterior to the bulge
so that the mandibular nerve is not injured.
• The external approach has been advocated for large mandibular
setbacks of greater than 10 mm, difficult asymmetries, or large
vertical moves in patients with unusual facial structure.
Complications:
• Bleeding may occur due to injury to the retromandibular vein or
masseteric artery where it crosses laterally through the sigmoid
notch.

56. Intraoral Vertical Ramus Osteotomy:
With the development of small offset oscillating blades with a long shaft,
and adequate retraction, the intraoral route has become preferred.
Technique
Incision:
• In the mucosa from midway up the anterior border of the ramus to the
first molar area.
Flap elevation:
• The periosteum is reflected laterally to expose the entire ramus, with
the exception of the condyle neck and coronoid tip.
• A special retractor, Merrill-Levaseur, fits around the posterior border
and retracts tissue laterally, so that an oscillating saw can be used.
• Also, Bauer retractors, left and right, can be used superiorly in the
sigmoid notch and inferiorly in the antegonial notch for additional
retraction and visualization.

57. Osteotomy:
• Antilingula has been proposed as the landmark for the mandibular
foramen.
• The cut should be made no more than 5 to 7 mm anterior to the
posterior border at the anticipated level of the foramen, using the
retractor as a guide to the posterior border.
• The cut is carried through the medial cortex, starting in the middle of
the ramus.
• It is carried superiorly to the sigmoid notch and then finished at the
inferior border

58. Inverted-L and C Ramus Osteotomies:
Both are generally approached extraorally, although intraoral variants are possible.
Indications:
• The L and C osteotomy is generally reserved for treatment of horizontal mandibular deficiency,
with some authors suggesting that it can be used to close an anterior open bite.
• Large setbacks of ≥7–8 mm need an inverted “L” osteotomy.
• Generally, advancements of the distal segment with either technique require bone grafting to
ensure adequate bone union.

59. Techniques
Incision:
Submandibular incision, 6 cm in length is made 2 cm below the angle
and inferior border of the mandible, the posterior portion is curved
superiorly to follow the cervical skin
Dissection:
• Sharp dissection is used down through the platysma, and then blunt
dissection is begun to minimize risk to the marginal mandibular
branch of the facial nerve.
• The incision through the pterygomandibular sling and periosteum is
made along the inferior border and is carried around the angle and up
the posterior border about 2 cm.
• Periosteum and attachments for the masseter are completely stripped
off the lateral cortex of the vertical ramus up to the level of the
sigmoid notch.

60. Osteotomy:
• The posterior vertical osteotomy is made at least 7 mm in front of the
posterior border and extends to a point of the inferior border just in front
of the angle.
• The horizontal cut is made above the anticipated position of the inferior
alveolar foramen .
• Internal fixation is generally recommended
• A small drain should be placed.
• External pressure dressings are maintained for 24 to 48 hours

61. C osteotomies:
• This technique was first described jointly by Caldwell and coworkers
They described a variation of their basic vertical-L with the addition of
a horizontal cut that extended forward from the vertical cut below the
inferior alveolar canal. This permitted a larger amount of bone contact
when the mandible was advanced.
• Arcing the inferior cut was suggested to permit increased bone contact
as the distal segment was advanced

62. • Unfortunately, the proposed arc cannot always be made because
the position of the neurovascular bundle may interfere. Sagittal
splitting of the inferior limb of the C osteotomy was proposed
both to increase the bone contact area when the mandible was
advanced and to decrease the problem of “notching” of the
inferior border

63. Bilateral Sagittal Split Osteotomy
The BSSO of the vertical ramus has in a relatively short time become the predominant
orthognathic procedure of the mandible.

64. Indications:

65. Hugo Obwegeser & Trauner: 1957
The horizontal osteotomy cut on the lingual side was made to the full of the
ramus.
Sagittal split ramus osteotomy
HISTORY

66. Dalpont (1961)
The first modification of the sagittal split by Dal Pont. the buccal and
lingual osteotomy lines are indicated. Advanced the oblique cut towards
molar region and made it vertical through the lateral cortex.

67. Hunsuck (1968)
Modified the cut he Shortened the cut through the medaial cortex taking it only as
far as the mandibular foramen.

68. BELL SCHENDEL (1977) & EPKER (1978)
Introduced a fourth cut, placed on the inferior border of the mandible for
easier split

69. Technique:
Incision:
• From anterior portion of the vertical ramus, midway between the
occlusal planes, carried downward through the middle of the retromolar
fossa to a point about 5 mm behind the second molar.
• Then the incisions wind laterally and forward to a point distal just to the
first molar.
Flap elevation:
• The periosteum is reflected to expose the lateral cortex of the mandible
down to the inferior border for the vertical cut only.
• Exposure ends at about the antegonial notch, and the masseter muscle is
reflected minimally - to maximize the blood supply to the proximal
fragment
• Inferiorly, the medial cortex is exposed to the lingula, with care being
taken to minimize trauma to the IAN just below this area.

70. Osteotomy:
• The osteotomy is begun by making a horizontal bone cut
through the medial cortex of the vertical ramus that extends
from a point just posterior to and above the lingula to the
anterior border of the ramus.
• Anteriorly, the cut is made about halfway through the ramus
• The vertical cut through the buccal cortex is generally made just
distal to the second molar and extends from the inferior border
superiorly to the external oblique ridge.

71. • The cut should be as close to perpendicular to the inferior border as possible and extended
just into cancellous bone.
• The vertical and horizontal cortical cuts are connected, starting superiorly at the anterior
border of vertical ramus and continuing down just inside the external oblique ridge to the
vertical cut.

72. • A narrow (4-mm) thin osteotome may be driven along the horizontal cut
and directed so that it cuts through the medial cortex above and behind the
lingula.
• Wide-wedging osteotomes have been used to slowly complete the split.
• Smith spreader, is used along with a smaller osteotome to allow more
control of the split.
• Generally, the split is initiated along the vertical cut and carefully extended
posteriorly.

73. • If mandible is to be advanced, medial pterygoid is
separated from the inferior border
• If mandible is to set back, medial pterygoid and
masseter needs to be stripped off to prevent
displacement of condylar segment
• In large advancements, bone sometimes has to be
removed from the remaining portion of the anterior
border of the vertical ramus of the distal segment just
anterior to the lingula to prevent encroachment of the
segment against the maxillary tuberosity

74. • It is acceptable to apply IMF without the use of an interocclusal splint.
• The placement of osseous fixation is performed at this point.
• After placement of osseous fixation, if rigid fixation is used, the IMF is released,
allowing the occlusion to be evaluated.
• The wounds are thoroughly irrigated and closed with the use of a resorbable running
suture.

77. Advantages
• Lower risk of ‘‘bad split’’ in the basilar region of
the mandible
• Possibility of lowering the mandibular angles in
cases of hyperdivergent Class II
• It does not increase the intergonial distance
• Preservation of the mandibular base, both during
the forward and backward movements, allowing
minor movements of counterclockwise rotation
and large movements of clockwise rotation
• Absence of a step at the base of the mandible,
avoiding skin marking and leading to better
aesthetic results.

78. Complications:
(1) Wrong split
(2) Injury to the neurovascular bundle
(3) TMJ problems
(4) Excessive bleeding
(5) Relapse.

79. • Also called “Buccal plate fracture”
• Small Proximal Fragment
• Free Fragment is checked for compatibility
• Secure the segment with plate
FRACTURES ON THE PROXIMALPORTION
Beukes J, Reyneke JP,Damstra J. Unilateral sagittal split mandibular ramus osteotomy: indications and
geometry. British Journal of Oral and Maxillofacial Surgery. 2016 Feb 29;54(2):219-23.

80. 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
Beukes J, Reyneke JP,Damstra J. Unilateral sagittal split mandibular ramus osteotomy: indications and
geometry. British Journal of Oral and Maxillofacial Surgery. 2016 Feb 29;54(2):219-23.

81. • Reasons for Tear or Cut Inferior Alveolar Nerve (IAN)
• Stretching of the nerve by retractors
• Forced osteotomy with reciprocating saw or chisel during splitting
• Abnormal anatomic position of the IAN canal
• Measures to Prevent Injury to the IAN During BSSO
• Prevent Stretching of the nerve from the medial protecting retractors
• Rotating instruments and saws may be used only to open the mandibular cortex
• Osteotome may penetrate only very superficially into the mandible during
splitting
• Removal of impacted third molars at least 6 months before surgery
NERVEDAMAGE
Beukes J, Reyneke JP,Damstra J. Unilateral sagittal split mandibular ramus osteotomy: indications and
geometry. British Journal of Oral and Maxillofacial Surgery. 2016 Feb 29;54(2):219-23.

82. Injury to the Lingual Nerve
• Less common
• Higher incidence of neurosensory disturbance with bicortical screws than monocortical
screws
Measures to Prevent Lingual Nerve
• Measurement of the depth of the drilling hole when screws longer than 15mm are used
• Drainage of larger hematomas to allow quick recovery from pressure on lingual nerve
Beukes J, Reyneke JP,Damstra J. Unilateral sagittal split mandibular ramus osteotomy: indications and
geometry. British Journal of Oral and Maxillofacial Surgery. 2016 Feb 29;54(2):219-23.
NERVEDAMAGE

84. TMJ Problems
• Improper plating can pull or push the condyle to an untoward position.
• Displacement of the condyle from the fossa is one of the main reasons for relapse
• Occurrence of pain and TMJ sounds in the first few months postoperatively are highly
indicative of condylar changes to occur in the proceeding months.
• Postoperative X-rays are taken to assess the situation.

85. Condylar sag :
Defined as an immediate or late change in position of the condyle in the glenoid fossa
after surgical establishment of a preplanned occlusion and rigid fixation of the bone
fragments, leading to a change in the occlusion.

86. Condylar Sag
Central
Unilateral Bilateral
Peripheral
Type I Type II

87. CENTRAL CONDYLAR SAG
• Central condylar sag occurs when the
condyle is positioned inferiorly in the
glenoid fossa and makes no contact with
any part of the fossa.
• After removal of the IMF and in the
absence of intracapsular edema or
hemarthrosis, the condyle will move
superiorly causing a malocclusion

88. PERIPHERAL CONDYLAR SAG - I
• Occurs when the condyle is positioned inferiorly
with peripheral contact with the fossa (lateral,
medial, posterior, or anterior), while the IMF is
in position and the teeth are in occlusion.
• Delayed occlusal relapse occurs as a result of
condylar resorption or change in its shape.

89. PERIPHERAL CONDYLAR SAG - II
• Occurs when the condyle is positioned
correctly in the fossa while IMF is in
position and the teeth are in occlusion;
however, the incorrect placement of rigid
fixation causes flexural stress in the
proximal segment.
• Once the IMF is removed, the tension in
the proximal segment is released and the
condyle moves either laterally or
medially and slides inferiorly.

91. Excessive Bleeding
• Bleeding can be from inferior alveolar neurovascular bundle, medullary bed, and facial
vessels or rarely from retromandibular vein.
• Can be controlled by local measures
• Facial vessels will have to be clamped and tied, for which an extraoral incision may be
required.
• Using the channel retractor with a cup to hold the inferior border prevents injury to the
facial vessels.
• Injury to the retromandibular vein is very rare.

92. RELAPSE
• Mandibular advancements greater than 7 mm
Prevention
• Proximal segment control
• Proper condylar positioning
• Avoidance of condylar rotation
• Decreased when 1-2 week skeletal fixation used
• Suprahyoid myotomies and orthodontic overcorrection
Van Sickels JE: a comparative study of bicortical screws and suspension wires versus bicortical screws in large mandibular
advancements. J Oral & Maxillofac Surg 1991;49;1970

93. Mandibular asymmetry:
Mild mandibular asymmetry
• The midpoint of the chin may be off the facial
midline.
• By horizontal repositioning of the inferior border,
the midpoint of the chin can be brought to the
midline of the face and the mandibular asymmetry
can be camouflaged.
• Stabilization and fixation is usually done using
figure of eight transosseous wires.
• Use of plates and screws for fixation is superior to
traditional transosseous wiring.

94. Extended Genioplasty
• Dissection and exposure of the chin, mental nerve and body of the mandible is
recommended by a degloving incision.
• An extended long osteotomy to the antegonial angle may be carried out.
• The long osteotomy ensures proper proportionality between the advanced segment and the
posterior mandible.
• By laterally sliding the lower border facial asymmetry can be corrected.

95. • Access is made by using 2 separate incisions to provide exposure
of the mental region and the ramus.
• The osteotomy is designed as an eccentric genioplasty
• a full-thickness osteotomy of the lower third of the mandible is
performed along the lower border
• The osteotomy is extended to involve the lateral aspect of the
ramus following the external oblique ridge
• The anterior segment is now positioned to correct midline and
restore vertical and anteroposterior relationship as planned on the
lateral cephalogram

98. Manual twist splitting technique:
• To define the separation better, a thick, finely-tapered osteotome 10
mm wide is driven between the proximal and distal segments of the
mandible through an anterior corticotomy.
• As the anterior corticotomy is opened by a thick, finely tapered
osteotome, the Dunn Dautrey osteotome is driven gently, with only
manual force, between the buccal cortex and the medulla.
• Subsequently, the Dunn Dautrey osteotome is run carefully down to
the inferior border of the mandible.

99. • The vertical cut on the buccal aspect - making anterior extension of
the cut till the area between first and second molar.
• The lower end of cut was kept 5 to 6 mm above and parallel to the
lower border of mandible which was extended backwards till
antegonial notch.
• The lower border of mandible was osteotomized at the antegonial
notch where density of the mandible is less in comparison to the first
molar area.
• Medial and horizontal cut similar to the Hunsuk modification of
Obwegeser technique,the cut was extended just above and posterior
to the lingula and then carefully the modified SSO was finalized with
the help of chisels and modified spreader