This document discusses osteogensis distraction and its biological aspects. It defines distraction osteogensis as new bone formation between bone segments separated by incremental traction. This process has five periods: osteotomy, latency, distraction, consolidation, and remodeling. During distraction, tension stresses stimulate new bone formation parallel to the vector of distraction. Distraction also affects surrounding soft tissues through distraction histogenesis, adapting muscles, nerves, and other tissues to stretching. The document examines the effects of distraction on various tissues and the safety and mechanisms of associated soft tissue lengthening.

1. Dr. Mohammed Alruby
Osteogensis distraction
Part (1)
Prepared by:
Mohammed Alruby

2. Dr. Mohammed Alruby
2
= Definition
= Historical development of craniofacial distraction.
= Distraction device classification.
= Biological aspect of osteogensis distraction.
= Distraction histogensis:
Effect on muscle
Effect on the peripheral nerves.
Effect on TMJ.
Effect on periodontal ligamment.
Effect on gingival tissues.
= Biomechanical effect of distraction device orientation during mandibular lengthening
and widening:
In transverse plane
In Sagittal plane

3. Dr. Mohammed Alruby
3
Distraction osteogensis
Definition:
Is a biologic process of new bone formation between the surfaces of bone segments that
are gradually separated by incremental traction?
This traction force, in turn- generate tension within the tissues that connect the bone segments,
which stimulate new bone formation parallel to the vector of distraction. Importantly, distraction
force applied to bone also create tension in the surrounding soft tissues, initiating a sequence of
adaptive changes termed distraction histogensis. Under the influence of tensional stress
produced by gradual bone distraction, active histogensis occurs in different tissues, including
gingiva, blood vessels, ligaments, cartilage, muscles and nerves. These adaptive changes in the
soft tissues allow larger skeletal movements while minimizing the relapse seen in acute
orthopedic correction
History:
- Although distraction osteogensis offer novel solutions for correction of sever maxillary and
manbibular deformities, the application of tensile and compressive forces to bones of
craniofacial skeleton is not anew concept. Since the 1800, mechanical forces were used to
separate the bones of maxilla at the midpalatal suture. More-over, depending on the
maturational status of the patient, different distraction like palatal expansion procedures have
been applied.
The concept and the technique of distraction osteogensis were first described by- Codvilla
(1905) who tried distraction of long bone that modified in 1951 by Gavrill Ilizarov that design a
new apparatus for bone fixation
==Historical development of craniofacial distraction:
** Dentofacial traction:
In 1728 Fauchard describe the use of expansion arch that apply tensile and compressive
force, when ligating an ideally shaped metal plate to the teeth, this form of traction was limited to
tooth movement only and had limited effect on the shape of the bone. In 1859 Wescott the first
reported the placement of the mechanical force to the bone of maxilla, a year later Angell
performed a similar procedure, using a differentially threaded jackscrew connected across the
palate to both bicuspid on one side and the second bicuspid on the other side
In 1893 Goddard further standardized the palatal expansion protocol.
** Craniofacial osteotomies:
The first surgical procedure for the correction of the craniofacial deformity was reported in
1848 by Hullihen that treat the prognathic mandible, after that Blair demonstrate the use of
bilateral horizontal ramus osteotomy to advance the mandible for treatment of case of class II. In
an attempt to increase the contact surface area between divided bone segment and provide
greater stability of bone fixation as Eieslberg and Pehrgadd that developed step like sliding
osteotomies for lengthening or widening the mandible
In 1927 Rosethal performed the first mandibular osteodistraction procedure by using an
intraoral tooth born appliance that gradually activated over a period of 1 month. Ten years later,
Kazanjian performed mandibular osteodistraction by using gradual incremental traction instead
of acute advancement. In 1948 Crawford applied gradual incremental traction to the fractured
callus of the mandible, in 1959 Kole, describe a method for surgically correcting an anterior

4. Dr. Mohammed Alruby
4
openbite due to maxillary anterior deformity and in the same year Kole also developed the
predecessor of rapid canine distraction method by using of corticotomy technique to assis the
moving teeth as individual or as group with orthodontic mechanics. In the late of the same year
Kole was also the first to demonstrate the combination of orthodontic and surgical technique for
rapid expansion of the palate on adults.
**Mandibular distraction:
In 1989 Mccarthy and colleagues were the first to clinically apply extraoral distraction in
the mandible. In 1990 Gurerrero developing his midsymphyseal mandibualr widening technique
using an intraoral tooth born device. In 1995 Molina and Ortize- Monesterio simplified the
methods established by Mccarthy
**Maxillary and midface distraction:
The first study demonstrating the possibility of maxillary distraction was reported by
Rachmiel in 1993, in 1995 Block and associate demonstrate maxillary advancement using tooth
born distraction device in dog and in the same year Polley and others report the first clinical
application of midface distraction.
** Alveolar ridge distraction:
In 1996, Chin and Toth reported the first clinical application of mandibular alveolar
distraction osteogensis, this technique is indicated in case of:
- Developmental anomalies such as: cleft palate.
- Maxillofacial truma that involve damage of the teeth and associated jaw structure.
- Periodontal disease that lead to bone and tooth loss from the alveolar process
** Distraction device classification:
= According to location:
1- Extraoral device: that are attached to the bone by percuteneous pins
Connected externally to fixation clamps that divided into: unidirectional
BI-directional
Multidirectional
2- Internal device: are located either subcutenously or within the oral cavity
(Intraorally), the intraoral device can be placed above and called extramucosal or below and
called submucosal.
= According to anchorage:
-Bone born
-Tooth born
-Both: hyprid
Biological aspect of osteogensis distraction
- Distraction osteogensis is a unique process of new bone formation between the surface
of the bone segments that are gradually separated by incremental traction. Depending on the
anatomic site where the traction is induced distraction osteogensis technique are divided into
1- Callotasis: which means distraction of the fractured callus.
2- physeal distraction: which distraction of the bone growth plates.
A- distraction epiphysiolysis: involve 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 produce a

5. Dr. Mohammed Alruby
5
fracture of the physis, the subsequent gradual separation of the bone lead to replacement of the
growth plate cartilage by trabecullar bone.
B- chondrodiatasis: utilize a very slow rate of bone segment separation (less than 0.5mm / day)
this allow stretching of growth plate without fracture.
- Callotiasis begins with the development of a reparative callus similar to that observed
during bone repair or fracture healing. New bone formation is initiated when a traction force is
applied to the bone segments, thereby interrupting the process of fracture healing and placing
the callus under tension. As the callus stretched, new bone is regenerated parallel to the
direction of traction. During this stretching, the soft callus is maintained at the center of
distraction gap while routine fracture healing occur at the periphery of the regenerate.
- Clinically, distraction osteogensis consists of five sequential periods:
1- Osteotomy: divides a bone into two segments, resulting in loss of continuity and mechanical
integrity.
2- Latency period: is the period from bone division to the onset of traction, this represent time
allowed for reparative callus formation.
Initially as a result of vascular disruption, hematoma is forms between and around the bone
segment, hematoma is converted to clot and bony necrosis at the end of the fractured segments.
Lasts from 1 to 3 days, at which time the clot is replaced with granulation tissue consisting of
inflammatory cell, fibroblast, collagen and invading capillaries. Following that is formation of
soft callus and this period is marked by continuo ingrowth of capillaries, during this stage the
granulation tissue is converted to fibrous tissue by fibroblast. Cartilage also replaced the
granulation tissue, this occur more toward the periphery of the intersegmentary gap than the
central region.
3- Distraction period: characterized by the application of traction to osteotomized bone segments
that are gradually pulled apart, resulting in formation of new bony tissue within the
progressively increasing intersegmental gap. Through the application of tension stress to the
intersegmentary tissue of the soft callus, the tension stress that develops in the gradually
stretched tissue stimulate changes at cellular and subcellular levels, these changes can be
characterized as growth stimulating effect and a shape forming effect.
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.
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, by the end of the
second week the osteoid begins to mineralize.
4- Consolidation period: is that time between cessation of traction forces and removal of the
distraction device. The period represents the time for complete miniralization of the distraction
degenerate.
5- Remodeling period: is the period from the application of full functional loading to the
complete remodeling of the newly formed bone. It takes a year or more before the structure of
newly formed bony tissue is comparable to that of the preexisting bone.
N.B: the mechanism of new bone formation during distraction osteogensis is dependent on both

6. Dr. Mohammed Alruby
6
the blood supply and rate of distraction. The most appropriate rate of mandibular distraction is
between 0.5 and 1.0 mm / day.
**Tooth movement into regenerate bone formed:
Several experimental studies were made to describe the tooth movement for the distracted
area (area of regenerate bone) at the beginning of distraction (group I), at the end of distraction
(group 2) and at the consolidation period (group 3). The studies indicated that the movement of
the tooth in-group 2 is more accepted movement and more safes during and after movement and
there are several factors that affect the tooth movement:
1- systemic: bone quality calcium level
General health blood supply
2- tooth born related factors:
=Size and shape of the tooth root.
=The quality of the surrounding bones
=Amount of bone between osteotomy and tooth root.
3- mechanical factors:
The type of tooth movement.
The stretched dentoalveolar and gingival fibers during distraction that applying forces to the
tooth.
**Implant and distraction osteogensis:
The technique of distraction osteogensis allows the creation of significantly more alveolar
bone than commonly achieved with grafts, which may enhance the over all prosthetic
rehabilitation as will as esthetics. So several studies were made to analyze the osteointegration of
endosseous implant placed into the regenerated bone area, the radiographic evaluation of these
studies indicated that:
Immediately after implant placement no bone was observed around the implant but after four
weeks the density of bone trabeculae had increased, twelve weeks after implant placement the
distraction regenerate was totally mineralized and no radiolucent area was observed at the
implant area.
- By histological evaluation:
Twelve week after implant placement newly formed lamellar bone observed around the
implant, however only few areas with direct bone / implant contact were seen, after 24 week for
implant placement, there are abundant newly formed mature lamellar bone around the implant.
** Histology of bone 1 year after distraction:
The mechanism of bone formation during osteodistraction is controversial, Karp in 1992
reported that the bone formed intramembranous method but Komuro in 1994 demonstrated that
the bone was formed by both endochondral and intramembranous bone formation especially in
the mandibular distraction. This supported by the presence of fibrocartilage island within
human mandubular regenerate bone, all the histologic evaluation of the regenerated area
indicated that the bone reach quality after 1 year from distraction.
Distraction histogensis:
Lengthening of the soft tissue is an important part of the distraction osteogensis process.
Ideally, the bone segment and the associated soft tissue should lengthen proportionally.
However, bone lengthening is possible because the bone is surgically divided into multiple
segments, whereas the soft tissues are stretched without surgical separation. Because of this,
different biologic mechanisms are involved in the soft tissue response to gradual stretching. This
process is termed distraction histogensis.

7. Dr. Mohammed Alruby
7
Distraction histogensis is a biologic process of soft tissue adaptation to gradual
stretching. This process is initiated by the tension created when applying distraction force to the
bone segments. Under the influence of tension stress, active adaptation occurs in all of the soft
tissues. Depending on the elasticity and capacity of regeneration, the various soft tissues respond
differently to gradual stretching. Nonetheless, two predominant mechanisms of soft tissue
adaptation occur during distraction histigensis: (1) soft tissue regeneration following disruptive
and degenerative changes and (2) neohistogensis as a result of generalized cellular proliferation
and growth.
Effect on muscles:
The structural and functional unite of the muscles is the muscle fibers that covered by
thick membrane called sarcolemma and surrounded by connective tissue called Endomysium.The
muscle fiber coalesces together to form muscle bundles, each bundles is covered by connective
tissue called perimysium.
- The muscle bundles coalesce together to form the whole muscle which covered by
connective tissue fascia called epimysium, these connective tissue contain blood vessels,
nerves and lymph vessels. The sarcomer is the smallest functional unite of muscle contraction,
it has been shown that the force developed by muscle during isometric contraction is
dependent on sarcomere length.
- In order to preserve or restore muscle function, the length of sarcomeres must be returned to
the optimal range and this depend on one of these mechanisms:
the sarcomer length decrease during skeletal lengthening due to decrease the distance between
the muscle origin and insertion point.
Optimizing the sarcomer length in stretched muscle fiber is by rearranging the muscle fiber
relative to the axis of force generation.
- The length of the sarcomer could also be returned to the optimal range by addition of new
sarcomeres within the stretched muscle fibers.
The result from several studies for histologic evaluation of the geniohyoid muscle indicated that
certain range of adaptive changes in response to 10 mm. of bilateral mandibular lengthening-
some changes such as local atrophy of myofibers, focal necrosis, were unspecific and fairly
limited in extent. Concurrently, there was evidence of muscle fiber regeneration in response to
muscle traction.
** Bone – muscle lengthening ratio:
Several studies demonstrate that muscles take smaller length increase than the bone, as
Day and co – workers studies, demonstrate 6% increase of muscles with 10% tabial lengthening.
**Does muscle grow or stretch:
A number of studies were designed to address the fundamental question of whether gradual
distraction promotes muscle growth or whether muscle fibers are stretched.
- Matan and co- authors described the changes in sarcomer length, which increased immediately
after bone elongation, then decreased gradually and return to predistraction values with
concurrent increase in number of sarcomers
- histological studies also support the hypothesis of muscles growth under the influence of
tension stress. These studies have demonstrated that muscle neogenesis does occur during
gradual distraction and is thought to progress from myoblast proliferation to myoblast fusion
into myotubes.
- Other studies based on: progressive bone distraction progressively stretches the muscles,
resulting in repetitive microlesions and focal necrosis of individual muscle fibers, macrophages

8. Dr. Mohammed Alruby
8
immediately migrate to the disrupted fibers to engulf the muscle fibers. Damage of the basal
lamina stimulate the release of stellite cells, which play an integral role in regeneration and
growth of skeletal muscles. Release and activation of stellite cells coincide with massive
proliferation of myoplast, the myoplast then fuse into myotubes, which after synthesis of
contractile elements give rise to the new muscle fibers growing independly or incorporating with
the ends of existing muscle fibers.
- With regarding to the rate and rhythm of distraction, Illizarove and other investigators
demonstrated excellent bone regenerate formation and favorable soft tissue response with the
rate of distraction 1 mm./ day.
- Other finding suggest a more fractionated rhythm of distraction promotes more effective
myogensis, this is in arrangement with a report of Mizumoto and co-authors, they found that an
increased frequency of distraction resulted in higher DNA synthesis thereby providing better
muscle growth and regeneration during lengthening.
**Safety amount of distraction:
It noted that limb lengthening up to 10% to 12% poses no damage to the muscle and other
associated soft tissue, with up to 10% lengthening the muscle may stretch to accommodate the
increased length.
- With greater lengthening, the muscles undergo changes including myofiber atrophy,
degeneration. Several studies to compare the results for increasing the length more than 20%
indicated irreversible muscle damage.
Effect of gradual traction on peripheral nerves:
The nervous system is composed of an intercommunicating network of specialized cells
called neuron, which are characterized by a cell body, along process (axon), numerous short
process (dendrites), and specialized cell functions (synaps). The neuron is the structural and
functional units of the nervous system .The over all studies results demonstrate that distraction
osteogensis might produce significant abnormalities on inferior alveolar nerve (IAN) function.
These abnormalities primarily resulted from the surgical procedure (either osteotomy or fixation
screw placement).
- The osteotomy is one of the most critical procedure for IAN integrity and therefore has to be
performed with careful attention to the neurovascular anatomy and its individual variation,
several mandibular osteotomy techniques have been developed to minimize trauma to the
neurovascular bundles and enhance new bone formation during subsequent distraction. Some
authors place full thickness cortical drill holes along the osteotmy line and then connect them
with reciprocating or oscillating saw, and others divide lateral, superior and inferior aspect of
the mandible leaving the medial cortex intact
N.B: IAN injury may also be related to insertion the fixation pins or screws for distraction device
anchorage,. Extraoral devices with transcutenous endosseous pins have been associated with
higher risk of direct IAN injury.
**Adaptation of peripheral nerves to gradual incremental traction
Several experimental studies have demonstrated that peripheral nerve trunk are highly
resistant to stretching. Wall and co-warkers reported that during acute tabial rabbit nerve
stretching, significant nerve conduction changes were first observed at 6% strain. At 12% strain,
complete nerve conduction block was documented.
** Amount and rate of distraction:

9. Dr. Mohammed Alruby
9
Illiazarov demonstrate progressive degenerative changes of nerve fibers for 50% limb
lengthening, the first 5% of lengthening was mainly characterized by early degenerative changes
of myelinated nerve fibers with segmental constriction of nerve axons and shwann cells.
- It was postulated by Illizarov that 1.0 mm rate of daily distraction performed in a high
fractionated rhythm creates the most optimal environment for both regenerate bone formation
and surrounding soft tissue adaptation
Effect of gradual traction on gingival tissue
From several studies on the gingival tissue due to distraction osteogensis, the results
indicated that gingival tissue responds favorably to gradual stretching during osteodistraction. It
initially undergoes mild inflammation and reactive changes during distraction for few weeks of
consolidation, followed by reparative changes with neohistogensis to restore the structural and
functional integrity of the masticatory mucosa during the second through the eight week of
consolidation.
Effect of gradual traction on the periodontal ligament
The PDL is the connective tissue that attaches the tooth root to the alveolar process,
although the PDL thickness ranges from 0.15 to 0.38 mm, it is fairly consistent around the tooth.
- The PDL is composed of collagen fibrils that protect the tooth against forces from
multiple direction. The mechanism of PDL adaptation to gradual traction during craniofacial
distraction osteogensis is similar to that for orthodontic tooth movements, by starting
compression and tension stimulate adaptive mechanisms as resorption, cementogensis and
thereby restoring the equilibrium in length and tension of PDL. The sequence of adaptive
changes is affected by the placement of distraction forces, whether to the tooth or to bone
segment.
- Tooth born distraction device do not transmit all distraction forces to the bone segments
due to the elasticity of the surrounding soft tissue and stretching of PDL, this often results in
greater dental movement than skeletal movement and therefore should be taken into account
during preoperative planning when calculating distraction parameters such as duration of the
distraction period and distraction rate.
- Although bone borne distraction devices produce proportional skeletal movements, dental
relapse and tipping of the adjacent teeth may often occur. Therefore preventive measures
such as using full-sized arch wires completely ligated into place or retaining teeth during
distraction and consolidation are probably indicated.
Effect on TMJ:
Since the mandible and TMJ are considered a functional unite, so the mechanical
loading of the osteotomized mandible may have effect on joint position and physiology.
* Biologically: the TMJ is a synovial joint like other joint in the body is composed of articular
cartilage – synovial fluids – synovial membrane.
- The synovial fluids cover the articular surface, and essential for joint lubrication and
nutrition. Structural alteration in the synovial membrane may cause changes in the content of
the synovial fluids, resulting in altered cartilage metabolism.
- From the biomechanical point of view, there are several factors that ifluncing TMJ during
distraction osteogensis as:
1- Movement within the architecture of the joint.
2- Restriction imposed by the soft tissue envelope.
3- The load characteristic particularly of the articular surface and the applied
pressure.

10. Dr. Mohammed Alruby
10
* Physiologically: articular cartilage provides a nearly frictionless surface for transmission
and distribution of joint loads exhibiting little or no wear over decades of use. The maintenance
of the articular cartilage due to the balance of the anabolic and catabolic activities of
chondrocyte cell population.
- The results from several studies about the changes on TMJ, revealed that :
1- Permanent degenerative alteration in the TMJ leading to a clinical impairment of joint
function.
2- Initial disturbance may be associated with adaptive joint remodeling and subsequent
growth stimulation.
3- The joint may functionally adapt to the changing mechanical environment by altering
structural integrity.
According to these results some author support distraction protocol without extensive
mechanical loading using incremental approach to achieve optimal and predictable results for
mechanical lengthening
Biomechanical effect of distraction device orientation
During mandibular lengthening and widening
The successful application of the distraction osteogensis technique is equally dependent
on biologic and biomechanical factors. The biomechanical parameters of osteodistraction can be
divided into several categories that include extrinsic or fixator-related factors, intrinsic or tissue
related factors, and factors related to device orientation.
= Extrinsic parameters affect the mechanical integrity of the distraction device, which in turn
influences the stability of bone fixation. These parameters include the number, length, and
diameter of fixation pins; the rigidity of the distraction mechanism; and material properties of
device. Intrinsic parameters affecting the quality of the forming distraction regenerate include
the geometric shape, cross sectional area and density of the distracted bone segments; the length
of the distraction regenerate; and the tension of the soft tissue envelop (skin, fascia. tendons, and
ligaments). Another critically important Biomechanical parameter of distraction osteogensis is
the orientation of the distraction device and the resulting distraction vector relative to the
anatomic axis of the bone segments, occlusal planes, and desired direction of distraction.
= Because the mandible is V shaped when viewed in the transverse plane, the anatomic axis of
the right and left sides of the mandible are not parallel to each other or to the desired direction
of distraction. So the proper orientation of the distraction device and its relation to the axis of the
mandible prevent any complicated problem.
1- Transverse plane:
a- bilateral mandibular lengthening:
There are two models were designed to evaluate the effect of distraction device orientation
on bilateral mandibular lengthening:
In model I: the distractors were oriented parallel to the lateral surface of the mandibular
corpus.
In model II: the distractors were oriented parallel to each other and to the midsagittal axis
-By computer model analysis: for model I, caused an increase inter condylar width
during distraction due to limited lateral mobility of the condyles and rigid fixation of distraction
appliance to the body of the mandible, the tendency toward lateralization of the proximal

11. Dr. Mohammed Alruby
11
segments may generate unfavorable reactive forces that may lead to bending of the distractor
device, localized pressure- resorption of bone around the screw and under the fixation plates and
/or rotation of the proximal segments about the condyles causing joint compression and
potentially leading to degenerative changes. But in model II the inter condylar width did not
change at all during bilateral mandibular corpus lengthening.
Although the inter canine, inter premolar and inter 1st
molar widths changed slightly throughout
the study with no significant difference were seen between the two groups.
N.B: Gross examination of the TMJ from group I revealed site specific changes, which
correspond to the location of compressive area due to condylar rotation and lateral widening of
the proximal segment.
b- bilateral mandibular lengthening and midline widening:
There are two models, model III that similar to model I and model IV that similar to
model II and both have anterior distractor for widening at the anterior segment of the mandible.
- The Biomechanical effects of device orientation during the subsequent 10 mm of bilateral
mandibular lengthening were similar to those observed for model I and II, but the inter
condylar distance increase was less in case of model III and IV than for I and II.
2- Sagittal plane:
The effect of distraction device orientation on bilateral mandibular lengthening in the
Sagittal plane was also evaluated using two models, a simulated osteotomy of the mandibular
corpus was performed posterior to the third molars bilateral.
- Model V: the linear distractor was oriented parallel to the inferior border of the mandible.
- Model VI: the distractor was oriented parallel to the maxillary occlusal plane.
For both models, the distal bone segment was then moved 10 mm anteriorly in 1mm increments.
In the Sagittal plane, mandibular lengthening with linear distraction parallel to the inferior
border of the mandible increase the distance between the mandibular and maxillary occlusal
plane, resulting in an increased amount of lower anterior facial height, the magnitude of this
increase was proportional to the amount of lengthening, each mm of distraction generated
approximately 0.3mm of lower anterior facial height increase. However, when the distractor
were oriented parallel to maxillary occlusal plane no changes in the lower anterior facial height
occurred during 10 mm mandibular lengthening.
** Diagnosis and ttt plane:
Mandibular deficiency is one of the most common dentofacial deformity, this deformity
may be present in three dimension: anteroposterior – vertical – transverse, so careful evaluation
of the diagnostic record is required for developing an ideal treatment plane.
All diagnostic record with clinical examination give a general idea about the case and determine
the defect dimension and position and this help for detected the ttt plane and degree of
distraction needed for correction.