Distraction osteogenesis in maxillofacial surgery
-
Upload
joel-dsilva -
Category
Healthcare
-
view
410 -
download
4
Transcript of Distraction osteogenesis in maxillofacial surgery
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.