Distraction Osteogenesis.ppt

Distraction Osteogenesis BY DR. CHITRACHAKRAVARTHY

1. DR.CHITRA CHAKRAVARTHY
PROF.& HOD DEPT OF OMFS
NAVODAYA DENTAL COLLEGE

2. Revolutionized the treatment options available to the
patients with craniofacial abnormalities.
Distraction osteogenesis (DO), is a technique by which
lengthening of a bone can be brought about by new
bone formation as a part of a normal healing process

3. Bone is osteotomised surgically
Ends are gradually distracted away from each other
Regular controlled force applied
New bone formation takes place between the 2
osteotomised segments.

4. Alternative to Orthognathic surgery.
Ability of the soft tissue envelope of the bone to
accommodate the gradually enlarging underlying
skeletal framework is its greatest advantage.
Factor unique to this technique -stability of this
procedure.

5. The concept originated as early as 1905 with
orthopedic surgeons. It was used to solve the problem
of leg length discrepancies

6. 1950’s Ilizarov introduced distraction osteogenesis for
the treatment of fractures and non unions of the long
bones of Russian soldiers.
Snyder was the first to experiment on a canine
mandible in 1973.
1992 feasibility of distraction technique on
membranous bones of the craniofacial skeleton was
reported by Mc Carthy in his 4 cases of mandibular
lengthening

7. Advantages over Orthognathic
surgery:
Safer surgical technique
Decreases the length of hospitalization
Decreased operating time
More conservative procedure
Done at a younger age of the patient rather than waiting for
growth completion as is done in case of Orthognathic
surgery.
No need for autogenousbone grafting which may at times
be required in Orthognathicsurgery.
Associated soft tissues also grow with it, i.e. the muscles,
mucosa, skin etc.

8. Indications for Distraction
osteogenesis:
Mandibular procedures
Hemifacial microsomia
Bilateral mandibular hypoplasia
Syndromic conditions such as Pierre Robin’s
syndrome, Goldenhar syndrome etc.
TMJ ankylosis leading to bird face deformity
Traumatic injuries to the mandible or pathologies
resulting in mandibular deficiency
Transverse deficiency of the mandible.

9. Maxillary procedures
Maxillary deficiency due to presence of cleft lip/palate
Severe midfacial deficiency
Palatal expansion

10. Craniofacial procedures:
Apert’s syndrome
Frontofacial advancement
Crouzon’s syndrome
Alveolar augmentation in the upper and lower
atrophic ridges-implants.

11. Technique and principles:
Distraction osteogenesis -formation of a surgically
created fracture
Gradual and controlled movement of these segments
away from each other.
Bone formation begins to take place between the cut
ends of bone.
Initially-immature but later transforms into mature
strong bone similar to the remaining skeleton.

12. Defined by Ilizarov after whom the technique has been
named.
Basic principles :
Bone cut
Latency period
Rate
Rhythm and
Consolidation

13. Bone cut or osteotomy:
Surgical fracture is created in the planned site in the
bone.
Preserve the blood supply of the bone
Preserve the integrity overlying periosteal envelope
during the surgery.
At the end of the osteotomy, the distraction device is
attached to the bone

15. Latency
Advisable to retain the bone in position with the device
for a period of around 5-7 days.
This is known the period of latency.
Formation of an adequate fibrovascular bridge between
the bony ends of the osteotomy.
Just like what happens in a fractured wound-callus
Wound passes into phase II of wound healing -provides
a regenerative environment.
In younger patients , the latency period may be
shortened to 1-2 days.

16. Rate:
The amount of separation to be achieved between the
osteotomisedbone ends per day.
The tensile stress that is applied when the bone ends are
separated by 1mm per day creates the best regenerated bone.
For younger children the rate may be increased to 1.5-2.0mm
per day.
If the bone segments are advanced more than this, the blood
supply to the regenerated bone is compromised.
Also the vascular supply of the overlying and surrounding
soft tissues gets compromised and leads to necrosis.
Compromised blood supply 0.5-1.0mmper day.

17. Rhythm
Refers to the number of times the distraction force is
applied to the device in a day.
A distraction force is ideally applied continuously
throughout the day.
Clinically however he force is best applied twice a day.
This is done by activating the device 2 times; each time
0.5mm is done to make it 1.0mm a day.
This is known as the rhythm of distraction.

18. If the patient experiences pain during the process, the
rhythm altered to smaller increments per day.
Applied as 0.25mm in four increments which makes it
1.0mm in a full day.

19. Consolidation phase:
New bone formation takes place between the bony
segments.
The regenerate is stabilized in position for complete
ossification.
The distraction device is held in neutral position for a
period of 4-6 weeks similar to a healing fracture.
After adequate ossification, a cortical outline is seen
radiographically of the newly generated bone.
If the device is removed prematurely, the chances of
relapse

20. Retention phase:
The distraction device is removed
The jaws are stabilized with orthodontic appliances or
occlusal splints.

21. Pathophysiology
Similar to the tension-stress model
When a slow steady traction is applied to soft tissues,
it makes them metabolically active
This metabolically active tissue has the capacity to
proliferate.
It also behaves similar to the tissues in that region.

22. Gradual distraction force-fibrous tissue and bone
formed in the interfragmentary area tends to
proliferate.
Since the rate of distraction is slow-more immature
bone is formed.
When retained in stable position -transform into
mature bone and then remodels
Whether in the long bones or in the bones of the
craniofacial region, distraction osteogenesis basically
takes place through intramembranous ossification.

23. STAGES OF MATURE BONE
FORMATION
Stage 1:
Stage of fibrous tissue:
Region between the cut bone segments consists of
fibrous tissue.
Histologically this is composed of longitudinally
oriented spindle shaped fibroblasts contained within a
mesenchymal matrix of undifferentiated cells.

24. Stage 2:
Stage of extending bone formation:
A slender trabecular pattern of bone is observed along
the bony edges towards the fibrous tissue.
Early bone formation is seen to advance from the bony
edges along the collagen fibres.
The osteoblasts lay down the bone matrix.
Blood histochemical investigations will reveal an
increased level of alkaline phosphatase, pyruvic acid
and lactic acid.

25. Stage 3
Stage of bone remodeling:
There are advancing fields of bone resorption and
apposition.
There is increase in the number of osteoclasts.

26. Stage 4:
Stage of mature bone formation:
Early areas of compact cortical bone are seen to form
close to the mature bone of the non distracted areas.
This bone is less longitudinally oriented and resembles
the normal bone architecture.
By around 8 months the newly formed bone achieves
almost 90% of the bony architecture.
The bone then responds to the functional loads
applied to it.

28. Types of distractors:
Extraoral distraction devices
These can further be divided into:
Unidirectional appliances
Bidirectional appliances
Multidirectional appliances


30. Intraoral devices
Intraoral devices can further be divided into:
tooth borne appliances
Bone supported devices

32. Extraoral devices-disadvantage
An external scar formation
Infection along the extraoral pins
Loosening of the pins
Hypertropic scar formation
Damage to extraoral structures such as facial nerve
and salivary glands
Lack of patient cooperation

33. Intraoral devices –advantage
Devices are concealed therefore better patient
compliance
Simpler to apply and to use
No extraoral scars
No inhibition of patient’s social activity

34. Disadvantage -intraoral devices
Does not allow multidirectional forces for lengthening
in more than one direction
If the appliance is bone supported, a second surgical
procedure is required for its removal.

35. Presurgical planning
Clinical examination
Radiographs with cephalometricanalysis
Other radiographs-OPG, PA view etc
CT scan, 3D reconstruction
Photographs taken in profile view and frontal view
Fabrication of study models of the occlusion to assess the
changes
Blood investigations for surgery
Selection of the direction of the device placement or the
vector
Selection of the device required for distraction.

36. VECTORS OF DISTRACTION
Vertical orientation: increase the vertical dimension of
the mandibular ramus.
Horizontal orientation: results in the increase in the
anteroposterior dimension of the mandibular body.
This results in an increased sagittal projection of the
symphysis.
Oblique orientation: increase in both the vertical and
horizontal dimensions of the ramus and the body of
the mandible.

37. Surgical phase
Anesthesia:Thesurgical phase is usually performed under
general anesthesia..
Incision:
intraorallyor extraorallydepending on the exposure
required.
intraoral incision -crevicularincision or a translabial
incision.
Subperiostealexposure of the buccalsurface of the
mandible taking care to protect the mental nerve.
If vertical device is to be placed, the ramusof the mandible
is exposed.

38. Osteotomy:
Placement of the device and not the osteotomydirection
dictates the distraction vector.
The osteotomyplaced in such a way so as to avoid injury to
any important structures
The osteotomysite is marked out on the bone.
The device is placed prior to making the osteotomycut.
A reciprocating saw or a fissure bur is used to initially place
a cut through the buccalcortex.
To osteotomisethe lingual cortex, care is to be taken to
avoid damage to the inferior alveolar nerve
check for mobility in all directions and the distraction
device is fixed to it.

40. Fixation of device:The device is then checked by
turning the screws to create a distraction of 3-4 mm.
The fragments are then brought back in close
approximation and the device left in this position.
Wound closure: Prior to wound closure, the direction
of turning of the device is to be noted. The incision is
then closed with mattress sutures.

41. Midfacialdistraction:
Le Fort I osteotomy

42. PALATAL EXPANSION

43. MANDIBULAR DISTRACTION

44. Complications of distraction
osteogenesis
Failure of the device or breakage
Loosening of the device due to lack of adequate bone
structure
Injury to the developing tooth bud
Injury to vital structures such as inferior alveolar nerve
Pin track infection in case of extraoraldevices
Relapse of the distraction achieved.
Early removal of the device may lead to fracture of the
jaw due to inadequate bone formation
Fibrous union instead of a mature bony union.