DISTRACTION OSTEOGENESIS

Joel D’SilvaResident

Department of OMFS

INTRODUCTION

• Acute advancement of osteotomized bone segments. • One of the major limitations is the inability of the soft

tissues to be acutely stretched. • Resulting in degenerative changes, relapse, and

compromised function and aesthetics.

DEFINITION:

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

• The process initiated when a traction force is applied to bone segments and continues as long as the callus tissue are stretched.

• Distraction forces applied to bone also create tension in the surrounding soft tissues, initiating a sequence of adaptive changes termed distraction histiogenesis

HISTORY 

• Hippocrates described the placement of traction forces on broken bones.

• De Chauliac in the fourteenth century, who used a pulley system that consisted of a weight attached to the leg by a cord.

 

• Banon, in 1826, is credited with being the first to perform a surgical division of bone, or osteotomy.

• Codivilla combined these techniques to perform the first limb lengthening using external skeletal traction after an oblique osteotomy of the femur.

• A significant contribution was made by the Russian surgeon Gavril Ilizarov 1951.

• He designed a new apparatus for bone fixation consisting of two metal rings joined together with three or four threaded rods.

• He later developed low energy, subperiosteal osteotomy

technique (corticotomy) and a unique protocol for limb lengthening utilizing a 5 to 7-day latency period, distraction at a rate of 1mm per day performed in four increments of 0.25 mm

EVOLUTION OF CRANIOFACIAL DISTRACTION OSTEOGENESIS 

Dentofacial traction;

• Fauchard 1728 described use of expansion arch

• Wescott first reported the placement of mechanical forces on bones of maxilla in 1859

• Angle introduced palatal expansion screw

1866 Kinsley used extra oral traction for functional appliances

Craniofacial osteotomies

• Hullihen - partial osteoplastic resection of prognathic mandible in 1848

• Blair horizontal ramus osteotomy

• Eiselberg, Pehr, Gadds introduced various osteotomies

DISTRACTION TECHNIQUES:

• 1927 Rosenthal performed first mandibular

osteodistraction• 1937 Kazanjian performed mandibular osteodistraction

with incremental traction• Crawford 1948 – gradual incremental traction to

fracture callus of mandible• Kole 1959 described method of surgically correcting

anterior open bite• In 1973 Snyder introduced Ilizarov’s principles to

craniofacial skeleton

CLASSIFICATION

Depending on the place where tensional stress was induced, these techniques can be categorized as either

Distraction

Callotasis

Physeal Distraction

Distraction epiphysiolysis

Chondrodiatasis

• Distraction epiphysiolysis involves a relatively rapid rate of bone

segment separation, usually ranging from 1.0 to 1.5 mm per day.

• The rapidly increased tension at the growth plate produces a

fracture of the physis.

• The subsequent gradual separation of the epiphysis from the metaphysis leads to the replacement of growth plate cartilage by trabecular bone.

 • Zavialov and Plaskin, in 1967, introduced the term distraction

epiphysiolysis and reported the first clinical application of this technique.

• Chondrodiatasis utilizes a very slow rate of bone segment separation (less than 0.5 mm per day).

• Slowly stretched physis intensifies the biosynthetic activity

of cartilage cells, resulting in accelerated osteogenesis.

• De Bastiani introduced term chondrodiatasis

Theoretically, physeal distraction osteogenesis offers significant advantages:

·         Single-stage operative procedure. ·         No soft tissue incision or osteotomy ·         Simulation of "natural" growth ·         Large areas of new bone formation ·         No additional bone grafts.  

• Callotasis a gradual stretching of the reparative callus forming around bone segments interrupted by osteotomy or fracture.

• Latin noun callum (scar tissue between bone segments) and the ancient Greek noun taois (tension or extension).

 

BIOLOGIC BASIS OF

NEW BONE FORMATION

ILIZAROV DISCOVERED TWO BIOLOGIC PRINCIPLES OF KNOWN AS THE "ILIZAROV EFFECTS".

(1) The tension-stress effect on the

genesis and growth of tissues, and

(2) The influence of blood supply and

loading on the shape of bones and joints.

• The first Ilizarov principle postulates that gradual traction

creates stress that can stimulate and maintain regeneration and

active growth of living tissues.

• Clinically, after distraction, newly formed bone rapidly remodels

to conform to the bone's natural structure.

• The second Ilizarov principle theorized that the shape and mass of

bones and joints are dependent on an interaction between

mechanical loading and blood supply.

• If blood supply is inadequate to support normal or increased

mechanical loading, then the bone cannot respond favorably,

leading to atrophic or degenerative changes.

DISTRACTION OSTEOGENESIS (CALLOTASIS) CONSISTS OF FIVE SEQUENTIAL PERIODS:

(1) Osteotomy, (2) Latency, (3) Distraction, (4) Consolidation, (5) Remodeling

Osteotomy

Latency

is the period from bone division to the onset of traction and represents the time required for reparative callus formation between the osteotomized bone segments.

is the surgical separation of a bone into two segments.

The distraction periodis that time when a traction

force is applied to bone segments, and new bone, or

distraction regenerate, is formed within the

intersegmentary gap.

Two major parameters are of critical importance during this period:

        The rate          Rhythm of distraction.

• The rate of distraction represents the total amount of bone segment movement performed per day

• The rhythm of distraction is the number of increments per day into which the rate of distraction is divided.

 

The consolidation

period

The remodeling

period

begins after achieving the desired amount of lengthening when traction forces are discontinued.

This period allows mineralization and corticalization of the newly formed bone tissue prior to distraction device removal.

is the time after removal of the distraction device.

Distraction osteogenesis begins with the development of a reparative callus between the edges of two bone segments divided by a low-energy

osteotomy.

• Gradual incremental separation of bone segments places the callus under tension; this aligns the inter-segmentary gap tissues parallel to the direction of distraction.• After the desired amount of bone length is achieved,

the distraction force is discontinued. The newly formed bone (distraction regenerate) then undergoes maturation and remodeling until it becomes undistinguishable from the residual host bone.

OSTEOTOMY• An osteotomy divides a bone into two

segments, resulting in a loss of continuity and mechanical integrity; this is also referred to as a fracture.

• Discontinuity of a skeletal segment triggers an evolutionary process of bone repair known as fracture healing.

• This process involves recruitment of osteoprogenitor cells, followed by cellular modulation or osteoinduction, and establishment of an environmental template (osteoconduction).• As a result, a reparative callus is formed within and

around the ends of the fractured bone segments; under normal conditions, the callus undergoes gradual replacement by lamellar bone, which is mechanically more resistant.

FRACTURE HEALING HAS BEEN DESCRIBED AS CONSISTING OF

SIX STAGES OR PHASES:

• The stage of impact takes place at the moment of stress and lasts until there is complete dissipation of energy, which is absorbed by the bone until failure occurs.• The stage of induction provides modulation of cells

needed for the repair process. Possible inductors include products of cell death, oxygen gradient, electric potential, noncollagenous proteins, and others.

LATENCY PERIOD.

The latency period is the period from bone division to the onset of traction. This period represents the time allowed for reparative callus formation.

• The sequence of events occurring during the latency period is similar to that seen during fracture healing.

Initially, as a result of vascular disruption, a hematoma forms between and around the bone segments. The hematoma is converted to a clot and bony necrosis occurs at the ends of the fracture segments.

There is an ingrowth of vasoformative elements and capillaries for the restoration of blood supply, and tremendous amount of cellular proliferation.

Lasts from 1 to 3 days, at which time the clot is replaced with granulation tissue consisting of inflammatory cells, fibroblasts, collagen and invading capillaries.

• Following inflammation is the soft callus stage, which lasts approximately 3 weeks. This period is marked by a continuous in growth of capillaries into the fracture callus.

• On the fifth day after osteotomy, a minicellular network of growing capillary loops is formed in the medullary canal of both proximal and distal segments in the areas adjacent to the fracture line.

• Less differentiated, free circulating osteogenic cells are located inside the terminals of the newly formed capillaries.

• During the soft callus stage, granulation tissue is converted to fibrous tissue by fibroblasts. Cartilage also replaces the granulation tissue. This occurs more toward the periphery of the intersegmentary gap than in the central region by a front of endochondral ossification.

• The amount of cartilage in the intersegmentary gap is variable.

• It seems that if the callus outgrows its blood supply, cartilage provides a suitable material that is less demanding of oxygen, which temporarily bridges the gap until the blood supply catches up.

• Callus formation is the response of determined osteoprogenitor cells, originating principally in the periosteum and endosteum, to a number of activating factors released from freshly injured bone tissue.

• The mechanical role of callus formation is obvious; it gradually enlarges the diameter of the segment ends and thereby the cross-sectional area of the segment sites.

• Histologically, callus formation occurs mainly by a mixture of gap healing and direct appositional bone formation, and its main sites of occurrence (outer and inner surfaces of the segment ends) selves a solid base on which new bone tissue is deposited.

DISTRACTION PERIOD  The distraction period is characterized by the

application of traction forces to osteotomized bone segments.

Bone segments are gradually pulled apart, resulting in formation of new bony tissues within the progressively increasing intersegmentary gap.

• During normal fracture healing, the fibrocartilaginous tissue of the soft callus is replaced by osteoblasts into fiber bone (hard callus stage). The cartilage calcifies as capillaries invade and osteoblasts lay down new bone on the calcified cartilage matrix.

• The stage of hard callus lasts 3 to 4 months for many fractures and is followed by the stage of remodeling. When fiber bone is slowly remodeled to lamellar bone and the medullary canal is reconstituted.• The stage of remodeling ends when the bone has completely

returned to normal with restoration of the medullary canal.

• During osteodistraction, however,the normal process of fracture healing is interrupted by the application of gradual traction to the soft callus.

• A dynamic microenvironment is created.

• The tension stress that develops in the gradually stretched tissues stimulates changes at the cellular and subcellular levels.

• These changes can be characterized as a growth-stimulating effect and a shape-forming effect.

• The growth-stimulating effect of tension activates the biologic elements of the intersegmentary connective tissue.

THIS INCLUDES

• (1) prolongation of angiogenesis with increased tissue oxygenation, and

• (2) increased fibroblast proliferation with intensification of biosynthetic activity.

• The shape-forming effect of tension causes an altered phenotypic expression of the fibroblasts. • The shape forming effect also polarizes these "distraction"

fibroblasts, orienting them and their secreted collagen parallel to the vector of distraction.

• New tissue formation in a direction parallel to the vector of traction. As distraction begins, the fibrous tissue of the soft callus becomes longitudinally oriented along the axis of distraction.

• Fibers are also oriented along the direction of distraction. These cells form collagen fibrils that are grouped into fibers at the distal and proximal ends of the intersegmentary tissues.

• Between the third and seventh days of distraction, capillaries grow into the fibrous tissues, thereby extending the vascular network not only toward the center of the gap but also toward the medullary canal of both adjacent bone segments.

• The newly formed capillary loops are parallel to each other as well as to the axis of distraction.

• Very often, newly formed vessels in the distraction regenerate have a spiral pathway and numerous circular folds suggesting growth rates much higher than the rate of distraction, and 10 times faster than vessel growth during normal fracture healing.• Capillary terminals actively invade the fibrous tissues,

supplying them with less differentiated cells that differentiate into fibroblasts, chondroblasts, or osteoblasts.

• During the second week of distraction, primary trabeculae begin to form.

• The osteoblasts, located among the collagen fibers, lay down osteoid tissue on these collagen fibers and eventually become enveloped as bone spicules gradually enlarge by circumferential apposition of collagen and osteoid.

• Osteogenesis is initiated at the existing bone walls and progresses toward the center of the distraction gap.

• By the end of the second week, the osteoid begins to mineralize.

• At that time the distraction regenerate has specific zonal structure. • A poorly mineralized, radiolucent fibrous interzone is

located in the middle of the distraction gap, where the influence of tensional stress is maximal. • This zone consists of highly organized, longitudinally

oriented, parallel bundles of collagen with spindle-shaped fibroblast-like cells and undifferentiated mesenchymal cells

• The interzone functions as the center for fibroblast proliferation and fibrous tissue formation.

• The mixture of fibrous and cartilage tissues within the interzone suggests that during distraction, both membranous and endochondral processes play an important role in the process of bone formation.

• At the periphery of this fibrous interzone, there are two zones with longitudinally oriented cylindrical primary trabeculae, which are covered by a layer of osteoblasts that grow toward each other.

Bone formation occurs along the vector of tension and is maintained by the growing apexes of the primary trabeculae, which remain open during the distraction period.

These areas therefore function as the "growth zone" of the distraction regenerate, providing active osteogenesis throughout the period of elongation.

• This zonal distribution of newly formed tissues in the distraction regenerate and remains until the end of the distraction period.

• In addition, two new zones of primary trabeculae remodeling may become evident at the junction of the regenerate and the host bone segments.

 

Consolidation Period

The consolidation period is that time between cessation of traction forces and removal of the distraction device.This period represents the time required for complete mineralization of the distraction regenerate.

After distraction ceases, the fibrous interzone gradually ossify and one distinct zone of fiber bone completely bridges the gap.

Distraction regenerate forms predominantly via membranous ossification, isolated islands of cartilage may also be observed. Suggesting endochondral bone formation.

• In addition, focal regions of chondrocytes surrounded by a mineralized matrix may be observed, suggesting a third type (transchondroid) of bone formation, in which

• cartilage forms, possibly due to decreased oxygen tension; but is then directly transformed into bone, rather than by the traditionally accepted endochondral pathway.

• As the regenerate matures, the zone of primary trabeculae significantly decreases and later is resorbed completely.

 REMODELING PERIOD

The remodeling period is the period from the application of full

functional loading to the complete remodeling of the newly

formed bone.

• Initially formed bony scaffold is reinforced by parallel- fibered lamellar bone. Both the cortical bone and marrow cavity are restored.

 • Haversian remodeling. Representing the last stage of

conical reconstruction. Normalizes the bone structure. It takes a year or more before the structure of newly formed bony tissue is comparable to that of the preexisting bone.

  

Bio-

mec

hani

cal

para

met

ers

Extrinsic or fixator-related

Intrinsic or tissue-related

Distraction device orientation

Distraction vector orientation

Biologic parameter

Low power osteotomy

Adequate duration of

latency

Stable, but not rigid

direction of distraction

with maximum preservation of osteogenic tissues and periosteal /

endosteal blood supply

to allow development of the fracture callus,

fixation of the bone segments, allowing their dimensional movement while preserving axial micro motion

Which is precisely calculated

Optimal rate and rhythm of distraction

Sufficient time for consolidation and remodeling of the newly formed bone prior to unrestrained functional loading

Proportional relationship between mechanical loading of the newly formed bone and its blood supply

TREATMENT PLANNING

• Thorough clinical examination to reveal and structural

abnormalities and functional deviations that require correction.

• Accurate orthodontic/surgical records -include lateral and

posteroanterior cephalometric radiographs, computed tomography

with three dimensional reconstruction, photographs, and models

 

This information is coupled with an understanding of the

patient's expectations to finalize the treatment goals and

predistraction, intradistraction, and postdistraction

treatment objectives.

• Osteotomy design and location, • Selection of a distraction device, • Determination of the distraction vector, • Duration of the latency period, • Rate and rhythm of distraction • And duration of the consolidation period.

OSTEOTOMY DESIGN AND LOCATION

DISTRACTION DEVICE SELECTION

• Craniofacial distraction devices have been developed for both external and internal applications. • Device selection is based on mechanical capabilities and

patient acceptance.

EXTERNAL DISTRACTION DEVICES:PLACED USING TRANSCUTANEOUS PINS.

The multidirectional devices, offer excellent control of bone segment movement,

Available in longer lengths. Easier to place and maintain, and are simple to replace during distraction and at the completion of lengthening.

DISADVANTAGES

• Skin scarring • Poor acceptance by patient. However,

placing the pins with minimal soft tissue tension and/or within the submandibular fold can minimize skin scarring.

INTERNAL DISTRACTION DEVICES:

Placed either submucosally (buried) or mucosally (intraoral).

Tooth borne HybridBone –borne

• neither produce facial scarring • nor have the negative psychosocial

impact of the external devices. It should be noted however, that a small

external incision is sometimes necessary for activation arm access, may be positioned aesthetically.

DISADVANTAGES

• Difficult to place especially when orientation is required, such as in the case of a hypoplastic ramus. • The higher risk of injury to nerves and anatomic

structures • A second surgical procedure is often necessary to remove

the devices following completion of consolidation. • Lack of the multidirectional adjustment capability

LENGTHENING CAPABILITIES.

• In order to complete the desired amount and angulation of distraction, the appropriate length of distraction device must be selected. • Although the magnitude of lengthening is registered on

distraction device, it does not always correlate to the clinically observed amount of actual bone distraction, which is usually less than anticipated and difficult to predict prior to distraction.

• The amount of bone distraction clinically observed during lengthening is a result of linear device activation altered by the effect of extrinsic and intrinsic biomechanical factors

• Amount of device activation and the observed amount of bone distraction varies, but reaches as high as 2:1 in some cases.

• When angular correction is incorporated into linear activation, the total amount of linear distraction decreases even more, further increasing the length requirement of the distraction device.

DIRECTION OF DISTRACTION.

• For a simple linear advancement, a unidirectional distraction device is suitable.

• If lengthening of the jaw is planned in two or more directions, a multidirectional device is required.

DISTRACTION VECTOR PLANNING

• The distraction vector defines the desired direction that the distal segment must move during lengthening.

• Despite precise planning, the actual distal segment movement is still difficult to predict and is affected by various forces.

• Treatment planning allows the clinician to compensate for, avoid, or eliminate undesirable reactive forces.

Factors that affect the vector of distraction include • osteotomy design and location, • distraction device orientation, • masticatory muscle influence, • occlusal interferences, • distraction device adjustment, • orthodontically or orthopedically applied forces.

DISTRACTION DEVICE ORIENTATION.

• Although osteotomy design and location may affect the muscle tension exerted on the proximal and distal segments, distraction device orientation is the primary factor that influences the vector of distraction.

• In order to minimize adverse biomechanical effects, devices should be placed parallel to the desired vector of distraction. Based on the orientation of the distraction vector, the distraction device can be placed vertically, horizontally, or obliquely.

• Orientation of the distraction device parallel to the Vertical long axis of the ramus often results in an oblique

distraction vector as it relates to the occlusal plane, since the ramus is not actually oriented perpendicular to the occlusal plane.

• If vertical elongation of the ramus and posterior occlusal bite opening is desired, it can more predictably be achieved by placing the distraction device perpendicular to the occlusal plane rather than parallel to the long axis of the mandibular ramus.• If anteroposterior advancement of the

mandibular corpus is desired, placement of the distraction device parallel to the occlusal plane is recommended.

• When the distraction device is placed parallel, to the long axis of the mandibular corpus, a divergence of the occlusion may occur, often resulting in a skeletal anterior openbite during lengthening.• Oblique distraction device orientation produces simultaneous

vertical and horizontal movements of the distal segment. • When an oblique device orientation is chosen, anteroposterior

positional changes occur along with hyper divergence of the mandible, resulting in clockwise rotation and anterior bite opening.

• In patients with a deep bite, this may be advantageous. In most cases, however, clockwise mandibular rotation results in an undesirable anterior openbite. • The oblique orientation of the distraction device

may be changed to either more vertical or more horizontal depending on whether the ramus or mandibular body requires more lengthening, respectively.

 

INFLUENCE OF MASTICATORY MUSCLES.

• The second factor that affects distal segment movement during distraction is the force generated by the masticatory muscle. Patients undergoing distraction functional compensations for their gradually changing occlusions. In order to aid in masticatory function patients may posture their mandibles anteriorly.

• The surgeon and orthodontist may also alter this untoward distal movement by making adjustments in sequential amount of activation of the multidirectional device

OCCLUSAL INTERFERENCES- • Alter the planned distraction vector. • Planned and executed predistraction orthodontic

preparation,• occlusal interferences may effectively be recognized

and eliminated in many instances. A developing openbite can be addressed during distraction with the utilization of bite plane or bite block appliances.

Distraction Device Activation.

Depending on the dimensional capability of the device, its activation can be performed linearly and/or angularly in the sagittal and/or transverse planes.

In the sagittal plane produces rotation of the distal segment around the axis located in the center of the hinge. Angular rotation of the distal segment occurs in harmony with rotation of the entire mandible around the axis located at the mandibular condyle, thereby creating the ability to open or close the bite anteriorly.

• Angular activation reduces the anteroposterior length of the mandible and must therefore be accompanied by additional linear distraction in order to maintain the mandibular advancement achieved. • Importantly, at least 10mm of linear advancement must

precede any angular activation to avoid undesirable approximation of the proximal and distal segments, potentially resulting in premature consolidation.

• In the transverse plane angular activation is affected by the resistance of the temporomandibular joints posteriorly and mandibular symphysis anteriorly • This may affect the temporomandibular joint anatomy as

well as result in chin point deviation. • Transverse adjustment must be made with caution,

always monitoring segment movement and temporomandibular joint function.

DIRECTION OF DISTRACTION The direction of distraction and the distraction utilized are determined based on the identified deformity and main goal of positional changes, • mandibular ramus or corpus lengthening, • gonial, or transverse intergonial distance correction.

In cases with simultaneous ramus and corpus lengthening, the distractor may be placed according to the simple formula: '

 Pin Placement Angle =

180 - Gonial Angle x Ramus Deficiency

Total deficiency  Where Pin Placement Angle = the angle between the

distraction vector and the mandibular plane.

Later, this formula was tested and modified with more accurate mathematical calculations:

Pin Placement Angle =arctan (Db/Dr) _ Sin a

Cos a

•   where a = gonial angle, Db = corpus deficiency, Dr = ramus deficiency.

 

AMOUNT 0F DISTRACTION

The amount of distraction can be determined by simply drawing a triangle, two sides of which represent the amount of mandibular corpus and ramus shortening, respectively. The angle between these two sides is equal to the gonial angle, and the third side of the triangle indicates the amount of distraction.

The amount of distraction can also be calculated using a formula:

Distraction Amount = Dc + Dr - 2(Dc x Dr) x cos a 

where Dc = corpus deficiency, Dr = ramus deficiency,

and a = gonial angle. 

• In cases with a simultaneous maxillary deficiency, the amount of maxillary correction should be identified and therefore included in the calculation of the amount of mandibular lengthening.

FUTURE GROWTH AND OVERCORRECTION

• Finally, the amount of overcorrection must be added when mandibular lengthening is performed on the growing child• This parameter is calculated based on the duration of remaining

mandibular growth and percent of yearly growth deficiency.

RATE AND RYTHM OF DISTRACTION • 1 mm per day in 0.25mm increments

• Children 1.5-2 mm in 0.5 mm increments

• Can be adjusted

• 360 degree turn 0.5 mm movement

DURATION OF LATENCY

7 days Young 5 days

CONSOLIDATION

•4- 6 weeks•6-8 weeks•Depending on radiographic evidence of bone ossification

Journal of cranio maxillofacial surgery 2004Biomechanical and clinical implications of distraction osteogenesis in craniofacial surgeryMeyer, Kleinheinz, Joos

POINTS TO BE NOTED

Local periosteal

blood supply and size of distraction segment

Influence the treatment plan

Small segment eg alveolus0.5-0.7 mm / day

mandibular sagittal distraction 2mm / day

SOME POINTS ON MOULDING

During active DO

End of DO

Or at the time of removal of the device manually position & fix it

rigidly with platesTraction elastics to guide segment to final position

Perform moulding >= 3mm

Perform regenerate moulding to

final position

1-3 days latency

Remove distractor

permanently

2-4 days in small bone segments

After three weeks of consolidation

If discrepancy occurs

Perform dancing of DO segment

DISTRACTION SURGERY (ORTHOGNATHIC SX)

• Factors influencing are the amount and trajectory of the planned bone movement• Surgical approach and technique is similar to orthoganthic

surgical technique

Mark osteotomy

Corticotomy

Screw holes for device placement

Corticotomy converted to osteotomy

Device fixation Activation Close 1-2mm

To verify the ability to place distractor in proper orientation

To check the impedance free

movement of segments

MANDIBULAR DISTRACTION

• Sagittal split plus osteotomy cut above the lingula along the ramus to the posterior border of the mandible

• Age dependant correction is a treatment option for the affected side.

• Pruzansky Mulliken classification of macrosomia – treatment –

mandibular do

• Children with macrosomia with airway compromise – mandibular DO

avoiding tracheostomy , drastic improvement has been reported

WITH TMD DISORDERS

• Patient with history of TMD use a modification of the classic sagittal split tech.

• As proximal and distal segments overlap distraction rate is increased to 2mm / day ( 0.5 mm QID)

• Further horizontal bone cut above lingula for impedance free rotation

• Class II elastics are placed to unload the TMJ

• Splints should be used extending to second molar with final occlusion indexed

MANDIBULAR WIDENING

• Often combined with maxillary transverse widening (SAME)

• Surgical procedure is similar to genioplasy with minimal periosteal stripping, use tunnelling technique.

• Distractor of choice is hybrid

• Solely bone borne distractor will create a v shaped regenerate chamber.

• 5-7 days of latency distraction at 1mm / day

NOTE…..• Apply slow incremental distraction forces.• DO forces created during mandibular widening

might translate to mandibular condyle .• Pre auricular pain or limitation in mouth opening

reduce the distraction to 0.5 – 0.25 mm.• Place a pontic on the gap btwn incisors created

due to DO or light springs.• Stabilization wit lingual arch in order to maintain

the new transverse dimension

SIMULTANEOUS MAXILLARY AND MANDIBULAR DISTRACTION

• Pt who has craniofacial microsomia have concomitant maxillary hypoplasia and occlusal cant towards the affected side.• If maxillary molar is in full occlusion or if the patient is in

permanent dentition then concomitant maxillary DO is indicated

Corticotomy Pterygoid Dys-junction

Orthodontic elastic traction guiding into proper plane during the DO process

No downfracture

MAXILLARY DISTRACTION• Surgical approach is similar to conventional Lefort l osteotomy.• Maxilla is freed but not completely downfractured 2-0 poly diaxone

suture at the maxillary 1st molar and zygomatic buttress to prevent the posterior tipping.• Device is pre-bend for the placement• Ideal trajectory – distraction parallel to each other and to the mid

sagittal plane.• Ensure that the resultant moment arm of the two distractors will not

cancel each other as the distractors reach the maximal length• Use anterior elastics to guide maxilla to proper position.

Expanding the soft tissue envelope is the only rate limiting factor Greater than 8-10mm distraction or with platal scarring requires an

external halo frame distractor

Centre of rotation of the maxilla is at the level of roots of maxillary first molar.

Periodic checking mandatory Anterior open bite

If left unchecked

ONCE MAXILLA IS STABLE( 5-6 WEEKS )

Palpable stable

maxilla

Radiographic

evidence

No need of rigid fixation to maxilla

MAXILLARY SEGMENTAL DISTRACTIONAl

veol

ar

clefts

Lesser osteotomy – between premolars

and 1st molarGreater osteotomy – between incisors and

cuspids

Use of orthodontic

appliances and arch wires allows

the distraction segments to

follow the curvature of

maxillary arch

• After distraction use orthodontic spring paralleling to the regenerate chamber 1-2 weeks after distraction ossification• Orthodontic alignment , repositioning of teeth in the regenerate

chamber leaving the defect for implant surgery if required small grafting will be done• This is a form of transport DO

• Use tunnelling technique to perform anterior osteotomy

• Horizontal bone cut parallel to the occlusal plane making the vector in an horizontal axis

• 5 day latency……………………1mm/day

• Anterior traction elastics for the forward thrust of segments

TRANSPORT DO

Transport distraction

involves creating a transport

disc in the bone , stump

adjacent to the discontinuity

defect of a resection site

Transport disc advancement

done 1mm / dayDiscontinuity defect is filled

till

Size of transport disc = size of regenerate chamber

Three points of fixation are necessary for transport DO

1. Proximal stump 2. Distal side

3. Transport discOr use a rigid connector with conventional

distractor

1

23

• Once the transport disc reaches the docking site the segment is

held in neutral position or fixed until cortical outline is formed.

• At the time of distractor removal surgeon might have to place

bone graft between docking site and transport disc.

• Transport disc becomes rounded and encased with fibro

cartilaginous cap. Removal is necessary for bony union

During active DO monitor patient to rule out tissue dehiscence

Woumd care + antibiotic treatment (systemic and local)

Post RT

Compromised blood supply

Advised disc dancing until dehiscence site closes

NOTE• Symphysis region is difficult to reconstruct because regenerate

tends to become a straight line rather than curvilinear shape, so intra oral surgical guides will help maintain the shape

View from

above

View from below

Dento alveolar unit formed is accurate

5 lines2 body, 2 para symp,

and 1 symphysis

So plan for 5 linear distraction vectors for the

mandible

ALTERNATIVE TREATMENT PLAN

Creation of large

transport disc 1.5 – 3 cm

Advance in a linear fashion until the junction of next linear segment

Disc is divided into two segment

s

Disc is held in neutral position

until early ossification occurs

One half of the original transport disc held in

place to the recon plate

After latency of 3-5 days the other half will become the new transport and reoriented in the

proper vector

TRANSPORT DISTRACTION

Primary transport DODone at the time of

resection If neck dissection is done latency period will be 7

days

Secondary transport DODone at the later stage

Limited dissection is advised

There will be excessive scarring due to the

previous sx so rhythm of DO is 4 times/day rather

than 2 times to allow incremental stretching of

soft tissue

Post radiation

With HBO therapy – recommended but not mandatory

Without HBO therapy, careful monitoring and distraction rate

should be reduced to 0.5 mm / day

Transport DO is also done in conjunction with composite free flap

TRANSPORT DO TO GENERATE A NEO-CONDYLE

• During transport DO fibro-cartilagenous cap forms. Use this property to reconstruct a neo-condyle.

• Create a reverse L osteotomy in the ramus of the mandible from the sigmoid notch behind the lingula i.e 1-1.5 cm above the inferior border of the mandible.

• Distractor is placed almost parallel to the posterior border of the ramus to guide the transport disc to the fossa to create a neo-condyle

Patients with bony ankyloses Gap arthroplasty Distraction sx

3D shaping of glenoid fossa

5 day latency period

ALVEOLAR DO FOR DENTAL IMPLANTS

Vertical height for the implant is needed / overlying soft tissue wont support osseous augmentation

Alveolar DO

Vestibular incision

Minimal periosteal stripping

Bone cut Distractor placement

Latency 3-5 days followed by 0.7 – 1mm 0.5 – 0.7 recommended

CONCLUSION

• The facial aesthetics are Gods gift to mankind, if the person is handicapped by any facial deformity that is marring his/ her happiness, thanks to distraction osteogenesis, we as OMFS can make every effort to restore the aesthetics, confidence and the quality of life in the social circle of the affected.