Distraction Osteogenesis for Mandibular Hypoplasia

DISTRACTION OSTEOGENESIS

INDIAN DENTAL ACADEMY

Leader in continuing dental education
www.indiandentalacademy.com





Traditional orthognathic surgery and craniofacial
reconstruction – advancement of osteotomized
bone segments.
Limitations – inability of soft tissues to be acutely
stretched, large skeletal movements
Degenerative changes, relapse and compromised
function



Alternative
gradual bone distraction known as
distraction osteogenisis.

IMPACT

INDUC
TION

INFLA
MATIO
N

SOFT
CALLUS


HARD
CALLUS

REMOD
ELLING

IMPACT

INDUCTI
ON

INFLAM
ATION

SOFT
CALLUS

GRADUA
L
TRACTIO
N


HARD
CALLUS

REMODE
LLING

Fibrocartilagenous tissue of
soft callus
Osteoblasts form hard callus
cappilaries calcifies cartilage
(hard callus) 3-4 months
Remodelling- normal
medullary canal

GROWTH
STIMULATING
EFFECT

GRADUAL
TRACTION-SOFT
CALLUS
SHAPE FORMING
EFFECT


ANGIOGENISISINCREASED
OXYGENATION
FIBROBLAST
PROLIFERATION

ALTERED
EXPRESSION OF
FIBROBLASTS

ALTERED
FIBROBLASTS IIr
VECTOR OF
DISTRACTION

3-7 DAYS
C.FIBRILS,VESSELS
AT DISTAL AND
PROXIMAL ENDS

CAPILLARIES AND
FIBROBLASTS
MULTIPLY 10X

FIBROUS INTERZONEP,MINERALIZED,RADIOLU
CENT

PHERIPHERAL 2
ZONES-LAYER OF
OSTEOBLASTS
GROW 2DS
EACHOTHER


OSTEOBLASTS
INBETWEEN
C.FIBERS LAY
OSTEOID

Distraction osteogenisis is a
biologic process of new bone
formation between the surfaces of
bone segments that are gradually
separated by incremental
traction

I.

Osteotomy of bone site with minimal periosteal
stripping.

II.

Latency period: 3,5, or 7 days, depending on the
surgical site.

III.

Distraction rate : 1.0 mm per day (0.5-2.0mm)

IV.

Distraction rhythm: continuous force application is
best, yet device activation bid is more practical and
allows for better pt compliance.

V.

Consolidation: until a cortical outline can be seen
radiographically across the distraction gap, usually 6
weeks

DISTRACTION

LATENCY(D)

RATE(MM/D)

RHYTHM

MANDIBLE

5

1.0

BID

MAXILLA

5

1.0

BID

ALVEOLUS/IMPLANT

5-7

TRANSPORT

5-7

1.0

BID

CONDYLE:TRANSPOR
T

5-7

1.0

TID,QID

MANDIBLE:CHILDRE

3-5

1.0-2.O

BID

MAND:SAGITTAL

5-7

2.0

BID

TRANSPORT:NECK
DISSECTION

7-10

0.5-1.0

BID

TRANSPORT:XRT

7-10

0.5

BID

0.5-0.7-1.0


BID

i.

Blood supply-overlying muscles, mucosa

ii.

Vector of distraction

iii.

Rate of distraction

iv.

Osteotomy location

v.

Muscle pull

vi.

Fibrous matrix-moulding

vii.

Latency period- more for small segments

viii.

Consolidation period



SYNDROMIC:- bilateral
1) treacher collins syndrome
2) cerebrocostomandibular sydm
3) mobius syndrome
4) arthromyodysplasia
unilateral
1) hemifacial microsomia



NONSYNDROMIC:- bilateral
1) bilateral microsomia
2) post ankylosis
3) post infection
4) tessier-7-cleft
unilateral
1) post traumatic
2) facial hemiatropy









GRADE I:- hypo affects only the gonial angle.
GRADE 2A:- the angle and the ascending ramus
are affected.

GRADE 2B:- hypo is more severe and affects the
angle and ascending ramus, the later having a
flat, rudimentary condyle.
GRADE 3:- complete absence of the ramus and
condyle

I.

UNIDIRECTIONAL

II.

BIDIRECTIONAL


SURGICAL TECHNIQUE:





A 3cmm incission in the lateral vestibule- subperiosteal
discection to expose the gonial angle and ascending
ramus.

The corticotomy is planed to preserve the nerve, the
intramedullary vascularity and the tooth buds.
The corticotomy begins in the retromolar area by
cutting the medial and lateral buttress, then extended
through the lateral aspect of the mand angle, cutting
the entire cortex sparing the cancellous bone.





Along the inferior aspect, it is extended widely
around the angle, so that only 6 to 8mm of
inner cortical bone remains intact to protect the
nerve and the artery.
The simultaneous increase in the vertical ramus
height with new bone formation at the mand
angle alows clockwise mand rotation during
DO and consolidation that closely mimics
growh.






The position of the pin placement determine
the distraction vector.
GRADE I:- the bone cuts extends obliquely
from the post edge of the hypoplastic gonial
angle to the retromolar area.
Then the pins are placed perpendicular to the
cut to obtain an oblique dist vector that
produces larger bone elongation at the angle
and less in the retromolar area



GRADE 2A:- the DO must remodel and
elongate the angle the inferior portion of the
ascending ramus.
The cut is placed obliquely to the junction of
the angle and the ramus, and the pins must be
inserted in an intermediate position between a
vertical and oblique distraction vector.



GRADE 2B:- the cut is placed horizontally at
the base of the ascending ramus and the pins
must follow a vertical dist vector in order to
obtain more elongation of the hypoplastic
ascending ramus.











Two bicortical screws(2 to 3.5mm dia) are percutaneously
introduced 3 to 5 mm in front of and behind the cut.
Care must be taken to position the pins paralell to each other to
facilitate their fixation to the device.
The device is made of two hollow plates with a central hole to
allow fixation to the pins.
A metal screw connects the two plates.
The screw hole in one plate is threaded, but not in the other, so
that as the screw is turned , the distance between the plates can
either be increased or decreased.









Micrognathic pts:- present with bilateral hypoplasia
that affects both the mand body and ascending ramus.

Two corticotomies are done- one vertical in the
mandibular body and the other horizontal in the
ascending ramus.
Three pins are used- a central pin at the mand angle
between the two corticotomies, a second pin in the
mand body and a third pin in the ascending ramus.
One bidirectional device is used on each side, each
device having two dist plates to allow independent
elongation of each segment, with the central pin used
as the fixed pivot for both devices.
DANCING DISTRACTION

DISTRACTION PROTOCOL
a.
Latency- 5 days
b.
Rate-app 1 mm/day
c.
Distraction period- 3-4 weeks
d.
Consolidation period- 6-8 weeks
COMPLICATIONS
I.
Skin scars
II.
Inadequate distraction vector
III. Prolonged consolidation period
IV. Major malocclusion
V.
Device instability
VI. Infection
VII. Device failure
VIII. Bone healing problem

1.
2.

A.
B.

UNIDIRECTIONAL
BIDIRECTIONAL
MANDIBULAR RAMUS DISTRACTION
MANDIBULAR CORPUS DISTRACTION


PREDISTRACTION ORTHODONTICS
 In absence of permanent teeth, orthodontic
treatment is limited to arch coordination and
rapid palatal expansion


Permanent teeth orthodontics involves
maxillary expansion, leveling and aligning of
dental arches, correcting dental
compensation, and correcting dental midlines

SURGICAL TECHNIQUE:•
A wedge shaped incission is made similar to
bsso, so that the device is covered without placing
mucosa under tension.
•

•

The lateral surface of the mand is exposed
subperiosteally from the emergence of the inferior
alveolar nerve to the neck of the condyle.
The anterior border of ramus is exposed to the base
of the coronoid process using a v-shaped
elevator, the posr border is exposed along the body
and gonial angle to the neck of the condyle with a
curved elevator.









The lateral osteotomy is done so that both cortices
of the inferoposterior and anterosuperior borders
are completely cut to facilitate a greenstick
fracture.

The intraoral distractor is then placed and the two
post pins are inserted transbuccally into the pin
fixation clamps.
The minimal skin incission for screw placement is
located ant to the distal camp, where cheek
elasticity will allow placement of the two ant pins
later in the same incission.

The osteotomy is converted to a total osteotomy
with an osteotome at the superior border.







The anterior pins are then placed using the same
transbuccal incission.
The rods should be oriented in such a way so that they
emerge through an incission in the submental area.

The wound is closed covering the entire distractor and
about ¾ of the shaft.

1.
Latency- 4 days
2.
Rate- twice a day at 1mm per day
3.
Consolidation period- 3 to 4 weeks

POST DISTRACTION ORTHODONTICS
Decidious dentition- functional orthodontics
Permanent dentition- occlusal corrections

INDICATIONS
1. Young patients with unsuccessful functional
appliance treatment.
2. Traditional orthognathic pts with severe
deficiencies that increase relapse potential.
PREDISTRACTION ORTHODONTICS
includes correction of crowding/spacing, tip and
torque correction, leveling of curve of
spee, and arch alignment/ coordination.

SURGICAL TECHNIQUE
 Procedure is almost similar to ramus distraction exepct for
location of cuts.




Briefly subperiosteal exposure, incomplete osteotomy of the
corpus, partial device fixation, osteotomy completion with
separation forceps, and device fixation.
It is important to leave space between device and bone to
prevent the bone from impinging on the rod during
activation.

DEVICE ORIENTATION
 The distractor must be placed to avoid or diminish the
possibility of an anterior openbite.

POSTDISTRACTION ORTHODONTICS
 Intermaxillary elastics to close the anterior and lateral open
bites



Ct images of the tmj prvide clearer images of bony detail, mr
imaging allows visualization of the intraarticular soft tissues
of the tmj.

1.

Condylar morphology remained unchanged

2.

Contours remained regular , with no post or lateral
flattening

3.

In some cases joint space altered, condyle minimally
repositioned or laterally subluxated.

4.

Moreover in some cases pretreatment of bilateral
subluxation of the meniscus was corrected during
distraction and the anatomic tmj relationships returned to
normal.

DISTRACTION

BONE GRAFTS

As early as 4 years

Min puberty

Less invasive

More invasive

No external site morbidity

Donor site morbidity

Soft tissues also lengthened

No soft tissue lengthining

Less risk of relapse

More risk of relapse

Less failure of device

More risk of failure of graft

No –ve impact on tmj

Negative impact on tmj observed

Less neurosensory disturbances

Neurosensory dist inevitable

No limit for bone lengthining

Limited lengthining possible


INDICATIONS

Transport distraction involves creating a transport disk in the
bone stump, adjacent to a discontinuity defect or resection site.
SURGICAL TECHNIQUE

An extraoral submandibular incission below the inferior
mandibular border is performed.






Lateral border of the mandible is exposed using with minimal
periosteal stripping on the buccal cortex and no periosteal
stripping on the lingual side.
A corticotomy is created through the lateral and inferior aspects of
the mand approximately 15mm proximal to the distal end of the
proximal bone stump.
The alveolar ridge is cut using a fine chisel taking care to avoid
perforating the gingival tissues.









A small bone plate can be placed to allow
completion of distractor pin placement.
The transport device is then applied using
bicortical pin fixation. To avoid a significant
scar, the pins are placed through individual
stab incisions rather than through the
submandibular incision.
The device is then attached to the
pins, verifying the vector and trajectory of the
planned transport segment.
Closure of the surgical site is done in layers.

1.

Latency period- adults- 5 days, children-3 to 5
days, in pts with compromised blood supply7 to 10 days.

2.

Rate- 0.5 mm twice a day, in compromised pts
0.25mm twice a day

3.

Consolidation period- 6 to 8 weeks


CONCEPT






During the process of bone transport the leading
edge of the transport disk becomes enveloped with
a fibrocartilagenous cap.

In mand corpus recon, this cap is removed to allow
osseous continuity between transport disk and
docking site.
It cap is not removed, then a pseudoarticulation
develops. This concept is used to create a
neocondyle.

SURGICAL TECHNIQUE








Once the bony or osseous ankylosis is released, a transport
, a transport disk is created by placing a reverse Losteotomy from the sigmoid notch to approximately 10mm
above the mand angle.
Then the device should be oriented in a vertical vector(
parallel to the post border of the mand) to elongate the post
ramus and increase post vertical height, when indicated.
For pts with bony ankylosis , a gap arthroplasty is
performed as usual and no muscle flap or intervening fascia
is placed in the gap site.
If the pt is at risk for heterotrophic bone formation, then the
gap site may be packed with an autogenous fat graft. Care
should be taken to shape the neofossa to an anatomic
configuration.

1.

Latency period-5 days

2.

Rate- 0.5mm twice per day

3.

Consolidation period- until a cortical outline is
visible radiographically, pt symptoms such as
increased pressure in the joint region felt.

4.

Pt should undergo active physical therapy(mouth
opening excercises), this allows for the functional
remodeling of the transport segment to become a
neocondyle.







For bilateral cases, attention must be paid to
the occlusion as an openbite may be present
due to condylar resorption or created
surgically as the ankylosis is released.
Temporalis muscle stripping is done to
counteract the strong muscle pull.
Occlusion must be controlled with orthodontic
appliances and intermaxillary elastics.




The lack of hard and soft tissues in the cleft deformities
lends them to treatment by distraction osteogenisis.

ALVEOLAR CLEFTS






Reconstruction of the alveolar clefts can be performed
by creating an osteotomy in the posterior maxilla and
horizontally advancing the segment anteriorly to close
the clefted alveolus.
The power of bone transport is that both bone and
gingival tissues are generated.
The arch can be alligned orthodontically after
distraction.





If the premaxillary segment is missing, the
local tissues can be used to create a neo
alveolus.
Simple distraction devices can be made by
modifying existing orthodontic appliances.








A pt with velopharyngeal insuffiency can also
be treated by transport distraction osteogenisis.
After speech therapy, if valopharyngeal
insuffiency persists and a pharyngeal flap is
being contemplated, the pt may be
alternatively treated by distracting the hard
palate and its associated palatal soft tissue
posteriorly.
When adequete bone stock is present, a palatal
osteotomy is created and the distractor is
placed across and anterior to the bone cut.

INDICATIONS
 Moderate to severe dentoalveolar bimaxillary
protrusion or anterior crowding with maximum
anchorage requirement, severe classII division I
malocclusions, and mild to moderate skeletal class
III malocclusion.


The tech was primarily designed for adults who
required short treatment times and maximum
anchorage control.

CONCEPT
The rcr tech consists of surgically undermining the
interseptal bone distal to the canine followed by
rapid tooth movement into the previously
extracted first premolar socket.

PRESURGICAL ORTHODONTICS
 Canine distraction must be performed before
ossification of the first premolar socket, so it
should be completed prior to extraction.




The 1st molar band should include a triple tube on
the buccal surface.
The anchor units are the first molars and 2nd
premolars bilaterally.

SURGICAL TECHINIQUE
 Immediately after the extraction of the 1st
premolar, the interseptal bone distal to the canines
is undermined and reduced in thickness.









Because the 1st premolar socket depth is always less
than that of the canine, the bone located distal to the
canine root apex would resist tooth movement during
distraction. Therefore the 1st premolar extraction socket
must be extended to the same depth as canine socket.
The interseptal bone is reduced to a thickness of 1 to
1.5mm.

The final step is to undermine the margins of the
interseptal bone distal to canine so that it can be broken
during distraction.
In order to do this, a bur is used to make two vertical
grooves from from the inferior to the superior aspect of
the socket on both the mesiobuccal and mesiolingual
line angles of the extraction socket.











One pair of intraoral distraction devices is placed on the
teeth.
At the same time, a continuous ss archwire is placed from
the 1st molar to the 1st molar.
The device is used to deliver the force and the archwire is
the base wire on which the canine is distracted distally.

Activation of the canine retraction device is begun the day of
insertion and continues until the canines have been
distracted into the desired position.
It is activated twice per day(0.35mm/turn), once in morning
and once in night because max cell proliferation in the PDL
occurs late in the evening and early in the morning.

COMPLICATIONS:- root resorption, tooth tipping alveolar
bone fracture.

INDICATIONS
1.
Unilateral cleft lip and palate
2.
Bilateral cleft lip and palate
3.
Unilateral cleft palate
4.
Mandibular prognatism
5.
Nasomaxillary dysplasia
PRESURGICAL ORTHODONTICS

This include skeletal and dentoalveolar expansion
of the maxilla, alignment of the permanent
incisors in the cleft area in some pts or
bonegrafting at 8 to 10years of age in other cases.





The day before surgery a modified quad-helix appliance
was placed in the palate.
In order to maintain maxillary expansion during distraction,
an extra transverse arch is fixed to both premolar bands,
which have vestibular hooks attached for elastic wear.

SURGICAL TECHNIQUE




Two 3-4cm long incissions are made in the maxillary
vestibule, leaving 2cm of intact mucosa between the two
incisions.
Subperiosteal dissection is performed from the piriform
fossae to the lateral maxillary buttress on each side to
expose the anterior and lateral aspects of the maxilla to the
level of the infraorbital nerve.











Dissection on the nasal floor is limited to the
lateral part only.
The septal base and the cleft remain intact
The osteotomy is performed above the roots of the
canines and molar tooth buds as seen in the
radiographs.
Osteotomy of the anterior maxillary surface must
maintain the integrity of the maxillar antral
mucoperiosteum for vascularity.

The osteotomy extends into the maxillary
butress, but pterygomaxillary disjunction is not
performed.

1.
Latency- 5 days
2.

Distraction forces are initiated using the previously
cemented intraoral appliance and a face mask supported by
the forehead and chin.

3.

Two elastics per side are attached from the vestibular hooks
in the canine region to a bar on the face mask.

4.

The initial force delivered by elastic is 900gm, which is
applied by wearing facemask for 16-18hrs per day.

5.

By applying distraction force, an advancement of 2-3mm is
achieved per week, distraction period is complete in 3-4
weeks

6.

Once the maxilla is advanced to a satisfactory classII molar
relationship, the amount of force is decreased to one elastic
per side(450gm) for another two months(consolidation
period)

DISTRACTION VECTORS
 Maxillary deficiency may be vertical, sagittal, or
transverse.






We three different orientations of maxillary distraction
vectors:- anterosuperior, anterior, and anteroinferior.
Commonly used is anterior, in which the horizontal
vector must be paralell to the desired occlusal plane in
order to minimize the development of an anterior open
bite.
An anteroinferior vector can be used to decrease the
vertical height of the maxilla. This is accomplished by
altering the position of the bar on the facemask in order
to change the direction of elastics.

CASE STUDY: A 17 yr old male pt with complete unilateral cleft lip and
palate and a classIII deformity.


He also had boderline velopharyngeal incompetence that
developed after multiple surgeries.

SURGICAL TECHNIQUE
 The max advancement was performed in a standard
foshion.




Under direct visualization, the max fracture was completed
and followed by a transverse osteotomy through the
palatine bones and partially through the suture joining the
maxillary and palatine bones.
The intraoral 12mm dist device was fixed to the palate in an
AP direction with 4 screws.





On the nasal side, the two posterior screws were
fixed to a plate, which converted the two bone
hemiplates into one segment.
The third screw was placed in the plate
superoinferiorly using a dental implant handpiece.

 Imm after completing surgery, the pt developed
severe velopharyngeal incompetence which was
predicted.


After completing 12mm of distraction( themax
amount allowed by the distraction rod), the pt still
had incompetence.





The distraction device was disengaged ant in
the palate, closed, and retracted more post by
screws without changing the position of the
post arms.
An additional 8 mm of dist was performed to
achieve a total of 20mm of device activation.


Case study :
 A 28yr old female presented with short face
syndrome charecterized by 10mm of vertical
maxillary deficiency and a class I occlusion

SURGICAL TECHNIQUE:
 A maxillary vestibular incision made from the
second bicuspid on one side to the second bicuspid
on the other




Total exposure of maxillary anterior wall and the
nasal floor was achieved by sub periosteal
dissection
A leefort I osteotomy was performed , followed by
positioning of the intermaxillary splint.







two vertical distractors (one per side ) were carefully
adapted and attached to the bone superior and inferior to
the planned osteotomy by screws parallel to each other and
to the acrylic splint lines
The distractors were then removed and bone division was
completed with manual soft tissue stretching to fully
moblize the maxilla
The distractors were then reapplied , followed by 1mm of
initial acute distraction and wound closure

DISTRACTION PROTOCOL:
 Latency – 5days




Vertical distraction was initiated at 1mm/day for 12 days
untill 20% of over correction was achieved,this is done to
allow for relapse after device removal
Consolidation – 10 wks

INDICATIONS:

hemifacial microsomia with severe occlusal cant
SURGICAL TECHNIQUE:
MAXILLARY OSTEOTOMY:
 An inncision is made in the upper buccal sulcus adjacent to
first molars , then periosteum is elevated from the pyriform
aperture to the malar area



The nasal mucoperiosteum is then elevated along the lateral
maxillary wall and the nasal floor to the anterior nasal spine






Osteotomy is performed from the pyriform fossa laterally .
The osteotomy is completed posteriorly with an 8mm chisel
pterygomaxillary disjunction is completed via a curved
osteotomy that extends laterally to the pterygoid fossa and
the maxilla is slightly moblised

MANDIBULAR OSTEOTOMY:
 After the maxillary osteotomy, a 5-7cm incision is
made in the inferior buccal sulcus of the affected
mandible








A periosteum is elevated on the lateral aspect of the
mandible , exposing the inferior part of the ascending
ramus and the gonial angle
A subperiosteal tunnel is then made on the medial side
of the mandible posteriorly to the alveolar ridge
towards the posterior edge
A corticotomy is performed on the lateral side of the
mandible posterior to the alveolar ridge towards the
gonial
Completion of the bone division is confirmed by the
bone segment mobilisation

DISTRACTION DEVICE APPLICATION:
 Two bicortical fixation pins are introduced
percutaneously , one in each bone
segment, anterior and posterior to the
osteotomy




The posiution of the screws is one of the most
important parameters that determine sthe
vector of the distraction
Depending upon the grade of mandibular
deformity ( PRUZANSKY Grade I, or 2A , or
2B) the vector of distraction should be
approximatly 45,60,90 degrees to the horizontal
plane respectively

DISTRACTION PROTOCOL:
 latency-5days






Intermaxillary fixation is applied and
distraction is initiated at a rate of 1mm/day till
facial symmetry is achieved

Consolidation – 6-8wks
Through out the treatment, IMF can be
removed for short periods to allow the patient
to eat or brush there teeth.

REGENERATE
DISORDERS

AXIAL
DEVIATIONS

SOFT TISSUE
OVER
STRETCHING

Hypotrophic
regenerate

sagittal

Blood vessels

Hypertrophic
regenerate

coronal

Peripheral
nerves

Regenerate
fracture

horizontal

Skeletal
muscles

Adjacent
joints

skin


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Distraction Osteogenesis for Mandibular Hypoplasia

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