Transcript
GOOD MORNING
DISTRACTION OSTEOGENESIS
PRESENTED BY DR RISSHI BHATT
GUIDED BY PROF.HOD.DR.S.M.AGRAWAL
CONTENT INTRODUCTION HISTORY BIOMECHANICAL PARAMETER BIOLOGIC PARAMETER CLASSIFICATION SEQUENTIAL PERIOD OF DO STAGES OF # HEALING EFFECT OF DO ON SKELETAL MUSCLE EFFECT OF DO ON PERIPHERAL NERVE EFFECT OF DO ON TMJ DISTRACTION DEVICES INDICATION & CONTRAINDICATION
TREATMENT PLANNING COMPLICATION CONCLUSION REFRENCES
INTRODUCTION
Samchukov et al., 1998 described
Distraction osteogenesis as a biologic process of new bone formation between the surfaces of bone segments that are gradually separated by incremental traction
The traction generates tension that stimulates new bone formation parallel to the vector of distraction
HISTORY AND EVOLUTION
DO evolved from three procedures
skeletal traction
bone segment fixation
osteotomy tech.
First described by CODIVILLA in 1905 on femur
GAVRIL ILIZAROV (1951)
Ilizarov effects :
1. tension stress effect
2. influence of blood supply
ILIZAROV’S EXPERIMENTS
Stable fixation with preserved axial micromotion generates membranous bone formation.
Preservation of osteogenic tissue during osteotomy.
Bone regenerates within the distraction gap is always formed along the vector of applied traction.
Bone formation depends on both rate and rhythm
0.5mm/day : premature consolidation
1.5mm/day : local ischemia
Blood supply must be proportional to mechanical loading.
Mc Carthy & colleagues were the first to clinically apply extra oral distraction osteogenesis on four children with congenital abnormalities.
Latency period – 7 days
Distraction – 1mm/day in two increments
Consolidation – 10 weeks
Guerrero (1990) devolped his mid symphyseal mandibular widening technique.
Molina & Ortiz simplified the method of Mc Carthy
- corticotomy with medial cortex intact
- one pin fixation on either side
BIOMECHENICAL PARAMETERS
1. Extrinsic
2. Intrinsic
3. Device orientation
4. Vector orientation
BIOLOGICAL PARAMETERS
1. Osteotomy
2. Latency period
3. Fixation
4. Direction of distraction
5. Rate and rhythm
6. Consolidation
7. Proportional relationship between loading
and newly formed bone
DISTRACTION DEVICE CLASSIFICATION
Craniofacial Distraction Devices
External Internal
Bone borne
Subcutaneous
Intraoral
1. Bone borne
2. Tooth borne
1. Unidirectional
2. Bidirectional
3. Multidirectional
Distraction device classification
Unidirectional device
Bidirectional device
Multidirectional device
Intra oral device
Sequential periods of DO:
1. osteotomy
2. latency
3. distraction
4. consolidation
5. remodeling
Bone physiology
Process of bone formation is called osseogenesis
Intramembranous
Endochondral
6 steps of # healing:
- impact
- induction
- inflammation
- soft callus
- hard callus
- remodeling
HOW DISTRACTON OSTEOGENESIS WORKS
The bone is a viscoelastic material, which means
that it has viscous as well as elastic properties,. A
series of mechanical tests have revealed its
Young’s Modulus. Which is pertinent information
for the design of the distraction device. Young’s
modulus of bone has been found to be 19.4 GPa
longitudinally and 15.0 GPa transversely.
Young’s Modulus for collagen is found to be
approximately 1000 MPa, and after about 3-4 %
strain, the collagen no longer acts elastically; it
only deforms plastically. Because the strain
acting on the soft tissue in the distraction gap,
during distraction osteogenesis, is much greater
than this value. The collagen will plastically
deform at the projected value of approximately 1
mm per day.
Foundation: Distraction Regenerate” http://www.globalmednet.com/do-cdrom/Biol/Histomor/rh07.htm
Strain
- physiologic - 2000-3500
- hyper physiologic - > 10,000
Woven lamellar bone - 2000 microstrains
Trabecular pattern - 20,000 microstrains
Fibrous - 200,000 microstrains
Multiple increments - higher extent of bone formation
> 20,000 - chondroid formation
-Ulrich Mayer et al
STRAIN - stimulatory effects
increased callus formation
increased osteoblast proliferation
20,000 microstrains with 10 cycles/day – fast results
AUTOMATED DISTRACTORS
-Ulrich Mayer et al
OSTEOTOMY
Division of bone in two segments
Triggers bone healing ( # healing )
- recruitment of osteoprogenitor cells
- osteoinduction
- osteoconduction
LATENCY PERIOD
Period from bone division to onset of tractionRepresents time allowed for callus formation
Sequence of events
-Hematoma
-Clot -Bone necrosis at the ends of # segments
Ingrowths of vasoformative elements & cellular proliferation
Stage of inflammation ( 1-3 days )
clot is replaced by granulation tissue
5 th day minicellular network of growing
capillaries is formed In medullary canals of both
# segments.
granulation tissue is converted to fibrous tissue
Cartilage also replaces the granulation tissue – more
towards periphery
Inflammation leads to soft callus stage
-callus formation is the response of determined
osteoprogenitor cells originating in periosteum and
endosteum
- it depends on many factors like:
cytokines and growth factors
- role of callus formation
Enlarges the diameter of segments
Serves as solid base for new bone formation
DISTRACTION PERIOD
Application of traction forces to osteotomised bone
segments.
Bone segments are gradually pulled apart resulting in
formation of new bone tissue with in progressively
increasing inter segmentary gap.
Normal # healing:
-fibrocartilagenous tissue of
soft callus is replaced by
osteoblasts into hard
callus.
- stage hard callus lasts for
3-4 months followed by
remodeling.
Distraction :
-normal process of healing
is interrupted by
application of gradual
traction which leads to
microenvironment.
- changes at cellular and
sub cellular level
- growth stimulating effect
- shape forming effect
Growth stimulating effect:
- prolongation of angiogenesis
- increased fibroblast proliferation
Shape forming effect:
- causes altered phenotypic expression of fibroblasts
( distraction fibroblast )
- polarization of these distraction fibroblasts parallel to
vector of distraction.
- soft callus becomes longitudinally oriented along the axis
of distraction
Between 3-7 day of distraction capillaries grow into
fibrous tissue
During the 2nd week of distraction primary
treabeculae begins to form
Osteogenesis is started at existing bone wall and
progress towards the center of distraction gap.
By the end of 2nd week osteoid begins to mineralize
CONSOLIDATION PERIOD
Time between cessation of traction and removal
of distraction devices.
This period represents the time required for
complete mineralization
Distraction regenerate forms predominantly via
membranous ossification.
REMODELING PERIOD
Period from the application of full functional
loading to the complete remodeling of
newly formed bone.
Last stage of cortical reconstruction normalizes
the bony structure ( 1 year )
EFFECT OF DISTRACTION ON SKELETAL MUSCLES
Muscle orient in a plane parallel to distraction force & adapt with compensatory regeneration.
( Guerrirre & co workers )
Sarcomere is the smallest unit of muscle contraction.
Force devolped by muscle during isometric
contraction is dependent on sarcomere length.
During distraction fibers of the attached muscles
undergo incremental gradual stretching of muscle
fibers which in turn stretches the sarcomeres
increasing their length.
Diminishes the number of
connecting bridges between
actin and myosin,
compromising muscle
function.
To preserve muscle function
sarcomeres must return to
optimal range.
Slower rate leads to good muscle adaptation but early consolidation.
Maintain the balance.(.75mm – 1mm per day)
More fractioned rhythm leads to less muscle injury
Mizumoto & coworkers
Amount of distraction:
10%-12% - no damage (only stretching)10%-20% - muscle growth>20% - irreversible muscle damage
20% - critical point
Nerve supply
Blood supply
EFFECT OF DISTRACTION ON PERIPHERAL NERVES
Distraction osteogenesis may result in
serious complications including peripheral
nerve injury.
Inferior alveolar nerve injury
direct
- intraoperative manipulation
- contact with fixation devices
indirect
- compression by postoperative odema
- constriction of medullary canal
Adaptation of peripheral nerves to distraction
peripheral nerve trunks are highly resistant to stretching
15% lengthening - early degenerative changes of myelinated nerves, swelling of schwan cells
20% lenthening - similar changes in non
myelinated nerves
20% -50% lengthening – wallerian degeneration
Regeneration of nerve fiber during consolidation
No acute injury with 10 mm distraction
Mild IAN changes in 10-15 % nerve fibers
- samchukov et al
TMJ ALTERATIONS DURING DISTRACTION
Different biological responses:
Compression – permanent degenerative changes
Adaptive joint remodeling
Functional adaptation to the changing environment
Distraction devices
Extra oral devices
Unidirectional devices: mandibular lengthening was possible in one direction only distraction was determined by the angle between Frankfurt horizontal plane and distraction device cannot be adjusted after insertion
Bidirectional devices
allows distraction in two directions as well
as adjustment of angle between two arms of the device.
single or double level osteotomy is possible.
Multidirectional devices
essential component of these devices are angulation joints and two geared rods of variable lengths.
in bidirectional devices the middle joint is simple hinge whereas in multidirectional devices it is multifunctional double ball joint.
device can be adapted according to individual anatomic situations.
Semi-rigid extra oral distraction devices
Intra oral distraction
In 1996 Chin and Toth described the feasibility and potential advantages of using intra oral devices for distraction osteogenesis.
Intraoral distraction devices
MD – DOS Device ROD custom distractor device Buried bidirectional telescopic mandibular
distractor Multiaxis intra oral distractor New spiral distractor Distractor with micro hydraulic cylinder
MD – DOS DEVICE - Morrice Mommarts
Started clinical application of this device in 1997
Consists of four major components
PFU – posterior fixation unit
AFU - anterior fixation unit
Spacer
DU - distractor unit
Posterior end of PFU is fixed in ascending ramus.
Depth of PFU penetration is controlled by PFU
screw length and bar spacer.
Anterior end of PFU is connected to posterior end of DU by hinge which allows DU to rotate along vertical axis.
Anterior end of DU is connected to AFU which is basically a modified five hole plate.
ROD intra oral custom distractor device
programmed along a desired vector.
there are five categories of ROD devices.
with ROD device it is possible to distract first and than decompensate the teeth.
Device fabrication
Distractor device consists of three components
Anterior activated expander , male and female attachments.
Male attachment is soldered to the crowns.
Male attachment also have vertical slots for wire fixation.
Female part is soldered to expansion screw
The intra oral attachment allows prefabrication of
device presurgically and cementation of
distractor device prior to osteotomy with removal
of distractor screws with the female part.
The vector planning ROD lab. alignment tool was devolved to properly position the distractor bilat.
Buried Bidirectional Telescopic Mandibular Distractor
Most of the current intra oral devices are
unidirectional with limited possibilities of
intraoperative adjustments.
BTMD has mediolateral offset with an adjustable screw allowing intraoperative adjustment of distractor vector and postop correction of midline occlusal discrepancies.
BTMD is stainless steel device that can be attached to mandible with upto 1.9 to 2.3 mm monocortical or bicortical screws
Activation is done by transmucosal approach.
BTMD has also shown its use in mandibular defect reconstruction.
Multiaxial intra oral distractor
Distractor that allows distraction in more than one direction
Requirement of such distractor are:
- should provide independent horizontal and
vertical distraction
-allows gradual changes between horizontal and
vertical axis
Basic unit of such distractor:
angulation gear – allows angulation change of 15’ vertical distractor is attached to posterior fixation
plate by a clamp horizontal distractor is attached to anterior fixation
plate
Spiral Distractor
Several authors suggest that mandible grows in archival fashion which has been hypothesized to be along logarithmic spiral.
Based on this information semi buried distractor with curvilinear vector was devolved.
By placing the osteotomy and device at mandibular ramus the archival path of distraction would mimic the logarithmic spiral of mandibular growth.
Curvilinear vector is chosen by VTO
Distractor with Micro Hydraulic Cylinder
Device is based on the concept of hydraulic pump.
it consists of two major parts
- cylinder
- piston
Both piston and cylinder have integrated fixation plates with two holes for bone fixation using conventional 3.5 mm bicortical screws
Depending on situation both incremental and continuous distraction can be applied
Indications of Distraction Osteogenesis
Children or infants with severe retrognathia associated with a syndrome (Pierre Robin syndrome, Treacher Collins syndrome) Unilateral hypoplasia of the mandible (Hemifacial microsomia)
Mandibular hypoplasia due to trauma and/or ankylosis of the temporomandibular joint
Nonsyndromic mandibular hypoplasia associated with a dental malocclusion where movement of mandible required is >10mm
Mandibular transverse deficiency associated with a dental malocclusion and dental crowding
Severe obstructive sleep apnea in patients who are morbidly obese
Shortened vertical height of the alveolar bone to receive an implant
Contraindications of Distraction Osteogenesis
Patients who are unable or unwilling to comply with the distraction schedule
Infants < 6 months of age due to fragility of bones to place distraction devices
Inadequate bone surface to accept distraction device
Inadequate bone surface area to provide regeneration of bone
Caution must be exercised in patients who have undergone radiation therapy. This is because of delayed bone formation due to reduced number of stem cells
Caution must be exercised in elderly patients because of the decreased number of mesenchymal stem cells
Treatment planning
History Records Patient expectations Distraction device selection Predistraction, intradistraction and
postdistraction treatment objectives Determination of vector Distraction protocol
Distraction device selection
External Internal
External devicesAdvantages : multidirectional excellent control of bone segment available in longer lengths easier to place and maintain simple to remove
Disadvantages :
skin scarring
poor patient compliance
Intaoral devices
Advantages :
no scarring
better patient compliance
Disadvantages :
difficult to place risk of injuries to nerves, vessels and tooth
buds second surgical procedure is required for
removal
Lack of availability of multidirectional devices
Factors for device selection
• desired lengthening• desired angular correction• vector• psychological requirements of patients
Lengthening capabilities
Lengthening capabilities
To achieve desired amount of lengthening and angular correction appropriate length of distractor must be selected.
Ratio of amount of device activation and observed amount of distraction can go as high as 2:1
Incorporation of angular correction further decreases total amount of linear distraction
Direction of distraction
Based on type of deformity and main goal of positional changes.
If only ramus or body lengthening is required unidirectional distractor would be utilized.
If simultaneous ramus and body lengthening is required, distractor may be placed according to the following formula:
Pin placement angle = 180 – gonial angle x ramus def / total def Pin placement angle = angle between vector of distraction and mandibular plane
Amount of Distraction:
The amount of distraction can be determined by simply drawing a triangle two sides of which represents the amount of mandibular corpus and ramus shortening respectively.
The angle between these two sides is the gonial angle and third side indicates amount of distraction. This can be calculated by using the formula:
Distraction amount = Dc + Dr – 2 (Dc x Dr) x Cos aDc = Corpus deficiencyDr = Ramus deficiencyA = Gonial angle
Amount of distraction
In case of simultaneous maxillary defficiency amount of maxillary correction is also included in calculation.
If deformity correction requires mandibular lengthening in combination with gonial angle change or transverse change, multidirectional distractor is required.
Bone ends should be separated by 10 mm before starting angular correction.
Double level osteotomy can be performed in difficult cases.
Orthodontics
Predistraction orthodontics
Intradistraction orthodontics
Postdistracrtion orthodontics
The distraction vector defines the desired direction that the distal segment must move during lengthening.
VECTOR PLANNING
Despite precise planning the actual distal segment movement is difficult to predict and is affected by various forces:
osteotomy design
osteotomy location
distracton device orientation
masticatory muscle influence
occlusal interferences
distraction device adjustment
orthodontically applied forces
Distraction device orientation
Device should be placed parallel to vector
vertically
horizontally
obliquely
Biomechanical effects of distraction device orientation
Mandible is V shaped when viewed in transverse plane, anatomic axis of right and left sides of mandible are not parallel to each other or to desired direction of distraction.
When viewed in sagittal plane, the inferior border of mandible is often not parallel to maxillary occlusal plane which is primary plane of reference for ant. mandibular distraction.
If distraction was placed parallel to the inferior border of the mandible, elongation occurred horizontally with opening or obliteration of gonial angle.
If distraction was placed obliquely to both ramus and body, neomandible maintained original form with preservation of gonial angle.
Laskin suggests planning distractor placement
preoperatively to achieve desired results.
Distractors placed parallel to the mandible with out regard to desired direction of distraction create reactive forces leading to following clinical problems:
bending of distractor device loosening of fixation screws
bone resorption
joint compression
The magnitude of lateral displacement tendency is proportional to amount of mandibular lengthening and mandibular arch angle.
Placement of distractor parallel to direction of distraction eliminates the tendency of lateral displacement of proximal segment.
If the distraction cannot be placed parallel to direction of distraction and lateral displacement tendency cannot be corrected they should be compensated either by acute correction or gradually incorporating a hinge element to lengthening device.
The vertical relationship between the distal mandibular segment and maxilla during distraction is another important consideration.
An increase in lower anterior facial height occurs when the vector of distraction is oriented parallel to mandibular plane instead to the maxillary ccclusal plane.
Vertical increase in lower anterior facial height may manifest as development of anterior /posterior open bite.
The amount of open bite is proportional to the amount of distraction.
Increase in angle between occlusal plane and vector = increased vertical deviation from desired ( open bite )
To prevent the development of open bite distractor should be placed as possible to desired direction of distraction, usually maxillary occlusal plane.
But open bite can still develop due to extrinsic and intrinsic factors.
Extrinsic factors: rigidity of distractor stability of screws
Intrinsic factors: soft tissue tension bone quality anatomy of mandible
Influence of masticatory muscles
Soft tissue traction due to physiologic muscle activation may contribute to distal segment instability.
Occlusal interferences
Should be corrected orthodontically
Distraction device activation
Depends on dimensional capability of device
Future growth and overcorrection
Skeletal age and future growth potential must be considered for distraction planning
The amount of distraction required is based on
careful assessment of mandible followed by compensation by growth standards or norms for particular race, sex, and facial skeleton maturity.
Surgical Therapy…..
• The orthodontist and the surgeon must have open communication throughout the entire planning process
• They must share the same treatment objectives
• Osteotomy cutShould be decided before hand with the help of imaging studies
• Osteotomy cut. Where do you place it? …
If the mandible is … Osteotomy cut Distrator plane
Deficient in ramus height
Superior to angle of mandible on ramus
Vertical plane
Deficient in body length Anterior to angle of mandible
Horizontal plane
Combination of both? Anterior and/or superior to angle of mandible?
Oblique plane??
Preoperative work up…..
Osteotomy / Corticotomty
Osteotomy: Division of bone in two segments
Corticotomy: Cancellous bone is kept intact
or
Subtotal / incomplete osteotomy
corticotomy
circumferential
external
External extended
Depending on number
Single Double
Depending on type of correction
Lengthening Widening Alveolar
Ramus
Angle
Corpus
interdental Post.to teeth
Midline
B/W lateral and canine
Horizontal
segmental
corticotomy
osteotomy
Distraction
Before device placement
After device placement
To start with
Distraction protocol
External extended
Preserves vascularity and tooth buds
Cancellous bone is spared
6-8 mm of inner cortical bone remains intact
Ramus osteotomy
Vertical, downward and inward ramus distraction
Required in hemifacial microsomia and other syndrome cases
Angular osteotomy
Downward and forward lengthening
Osteotomy is prepared from distal of 2nd molar down to inferior border of mandible.
10 – 12 mm of lingual cortex is cut with bur protecting the 3rd molar
Ridge corticotomy is done in oblique and anterior direction and than sharply turned posterior to angle of mandible.
Device is placed, marked and removed.
Osteotomy is completed with spreader
Device is placed
Closure is done
Corpus osteotomy
Horizontal and forward lengthening
Inferior border channel retractor is placed between 2nd and 3rd molar.
Mandible is than transected through both buccal and lingual cortex at inferior border, vertically upto 3mm of inferior alveolar canal
Outer cortex is than sectioned
Protecting the lingual periosteum saw is placed upside down and osteotomy is carried through alveolar crest, sup. Inf. to 3mm superior to canal.
6 mm medial bone is kept intact
Device is placed
Closure is done with small aperture at the top of incision to facilitate vertically placed chisel , which is placed to give final cut followed by complete closure
Mandibular widening
Complete osteotomy is done midline between central incisors below the roots of incisors.
Alveolar bone is than sectioned with bur taking care of teeth and gingiva
If teeth are very close the alveolar bone and gingiva,lingual cortex is green fractured with expansion forceps device.
Postoperative details
What should the surgeon watch for after the placement of distractor ?
During the distraction phase, the patient should be seen every 2-3 days to monitor the advancement and to intercept any potential occlusal discrepancies
During the consolidation phase, the patient should be seen on a weekly basis to monitor healing and ossification of the regenerate
In bilateral expansion of the mandible, the
patient should be distracted until a slight class
III dental occlusion exists (edge-edge incisal
relationship)
In a unilateral expansion, a slight over
correction of the mandibular midline is
recommended to overcome the deficient soft
tissue envelope
COMPLICATIONS
A complication is an unexpected deviation from the treatment plan that, with out appropriate correction will lead to worsening of existing, development of a new, or recurrence of the initial pathologic process
Mistake
Mistake is an inattentive action that results in a deviation of the course of treatment, thereby leading to the development of a complication
Potential mistakes
Iatrogenic
Patient related
Potential complications
Axial deviation
Axial deviation of distracted segment can result from various mistakes.
-inappropriate size and strength of device -inadequate osteotomy level -inadequate device orientation -inadequate hinge placement -inaccurate placement of device -comminuted osteotomy
Correction of axial deviation begins with elimination of main cause of this deviation.
-replacement of distracter device
-repositioning hinge axis
-reorientation
-additional surgery
Soft tissue overstretching
Blood vessels
rare
least tolerant to compressive forces
lead to ischemia
Adjacent joints
degenerative changes
Skin
scaring and necrosis
Infection
incidence is 5-30%, more with extra oral devices
Distraction vs OsteotomyDistraction Osteotomy
Need for bone grafting Not necessary even for defects > 20 mm
Necessary for defects >10 mm
Control over movement 3 Dimensional 2 Dimensional
On infants and children Can be done Think about perma-nent teeth and suffi-ciency of bone
Distortion and loading of the TMJ
Does not cause Risk of causing
Damage to the inferior alveolar nerve
Does not cause Risk of causing
Increasing ramus height
Possible Not Possible
Cost Expensive (distractors and equipment )
Relatively inexpensive
Time Takes time Quick Fix Method
Distraction vs osteotomiesThe argument contnues….
While traditional mandibular osteotomies, such as the bilateral sagittal split osteotomy, will always have a place, distraction osteogenesis allows a surgeon to treat patients who are unable or unwilling to undergo a traditional osteotomy
Distraction osteogenesis is a highly predictable and reliable method of increasing the bone in a deficient mandible
With technology advancements, the distraction devices become smaller and more sophisticated making distraction movements more precise
One of the current controversies involves using distraction osteogenesis instead of the traditional bilateral sagittal split osteotomy
Some authors have gone so far as to state that the bilateral sagittal split osteotomy is an obsolete procedure with no place in current practice
In reality, traditional mandibular osteotomies will always have a place; however, distraction osteogenesis provides the surgeon with another option in treating a wide variety of mandibular deficiencies
References
1. Craniofacial distraction osteogenesis – Mikhail L. Samchukov, Jason B. Cope, Alexander M. Cherkashin
2. Distraction of the craniofacial skeleton – Joseph G. McCarthy.
3. Oral and maxillofacial surgery – Peter Wardbooth.
4. Oral and maxillofacial surgery – Fonceca.
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