Distraction osteogenesis (DO)MATTICK 2000

Distraction osteogenesis (DO) is a biologic process of new bone formation between bone

segments that are gradually separated by incremental traction.

This controlled distraction, generates new bone within the distracted gap. So in a way, it is

an in-vivo bone tissue engineering

History Alessandro Codivilla in 1905, was the first to perform DO surgery. He published a case

report of femoral extension by applying axial forces of distraction.

Distraction osteogenesis for bone lengthening was an accidental discovery off Ilizarov when

he observed callus formation in a patient who had mistakenly distracted his frame instead

of compressing it.

The Russian surgeon, Gavriil Ilizarov, who pioneered the biological principles of bone and

soft tissue regeneration and popularized the technique of distraction osteogenesis, (Ilizarov,

1989).

McCarthy from United States, reported the first craniofacial DO in humans and Guerrero

was the first to use inta-oral device to widen mandibular arches.

Sequence of DOI. Osteotomy

• Trigger fracture healing will initiate: Angiogenesis, fibrogenisis, Osteoinduction &

Osteoconduction

a. Latency phase (3 to 7 days)

• Phase immediately following the osteotomy,

• Reparative callous formation

b. Distraction phase

• Gradual distraction at a rate of ~1.0 mm day

c. Consolidation phase (6-10 weeks)

• Distraction is ceased

• Mineralization and Corticalisation. The bone produced is less dense and of lower volume

than the ‘original’ bone, but is believed to have equivalent growth potential.

d. Remodeling Phase

• Continues approxiamtely for a year after completion

Histologically distinct stages of DONormally, four histologically distinct stages of bone repair are observed:

1. an inflammatory phase, immediately following an osteotomy, blood fills the space between

the separated bone segments, and an inflammatory cell infiltrate is observed. This

inflammatory stage represents an acute response to the injury and lasts several days. If DO

started at this stage, then the result is decreased bone formation, often with cartilaginous

elements present, and decreased mechanical strength of the newly created bone. An

important consideration in treatment planning for mandibular lengthening is how the bone

cuts will be coordinated with placement of the distractor. Some recommend:

Making the cortectomy, placing the distractor, and then completing the osteotomy with the

distractor in place. With that approach, the distractor may hinder completion of the

osteotomy.

First cortectomies followed by completion of the osteotomy through activation of the device

Completion of the osteotomy and placing the distractor after completing the initial incision

and dissection, doing the buccal cortectomy, removing the distractor and completing the

osteotomy, and then finally placing a distractor with the original relationships of the

segments intact.

2. The initial hematoma is then replaced by granulation tis sue. Large numbers of fibroblasts

and mesenchymal stem cells arc recruited to the region, and synthesis of type 1 collagen is

seen within the fracture zone. In addition, there is a vascular response marked by formation

of new capillaries. These fibrous structures create a soft callus that bridges across the

fractured bone segments. DO should start at this stage. The blood supply duitng DO

increased *7 times.

The cellular basis for induction of regeneration under stretching is that:

• Any cells under pressure will demonstrates catabolic state where it starts degeneration by

releasing of tissue resorbing factors. This in the pressure side of orthodontic tooth

movement.

• Any cells under stretch will demonstrates anabolic state where it starts regeneration by

releasing of tissue forming factors. This is the stretch phase in DO.

There are two important variables in the activation:

I. Rate, or the amount of distraction per day, and rhythm, or how frequently the device is

activated. If the rate of distraction is too small, there is a risk of premature consolidation. On

the other hand, too great a rate of distraction may place undue stress on the soft callus,

resulting in thinning of all dimensions in the mid-portion of the regenerate and an

"hourglass" at the distraction site. This can be likened to the effect of pulling taffy apart

II. With regard to rhythm, constant activation probably would be ideal, although this is not

possible with current devices.

a. Ilizarov felt that rhythm was critical to osteogenic activity. His recommendation was for 0.25

mm four times a day.

b. In the majority of maxillofacial cases described in the literature, the most common protocol

is 0.5 mm increments twice daily. Clinical experience suggests that activation of more than

0.5 mm at a time results in a marked increase in pain, from more aggressive stretching of

the periosteum and musculature.

c. In some instance activation of 0.5 mm may result in complaints of pain by the patient, and in

such cases distraction at a rate of 0.25 mill four times daily is an acceptable alternative.

d. Due to the fast healing response of infants, distraction can be initiated immediately, at the

rate of 1.5 mm per day in three 0.5 mm activations.

e. During the stabilization phase the use of orthodontic elastics guides the dentition, and is

also thought to aid vectorization and ‘mould’ the developing regenerate.

f. One of the primary considerations in treating hypo plastic mandibles is the extent to which

lengthening of the ramus versus the body is desired. Proportional analysis is one way to

establish this. The average relationship of ramus height (Co-Go) to body length (Go-Gn) is

5:7; the relationship of the maxillary jaw length (ANS-PNS) to mandibular body length is 2:3.

Another guideline is that the anterior cranial base length (S-N) is slightly less than (2 to 3

mm) the mandibular body length.

g. Weekly panoramic radiographs arc taken until the distractor is fully activated

3. Approximately 2 week; following the initial injury, there is a progressive mineralization of

the soft callus, resulting in formation of a hard callus. The hard callus is composed of

immature bone. In the final phase of fracture repair, there is extensive remodeling of this

"woven" bone, and the normal lamellar architecture is regained. If DO started at this stage

the distraction device may be unable to further separate the bony segments. In the Case of

large advancements. additional stabilization can be obtained from a brief period of

maxillomandibular fixation during the consolidation phase. With internal distraction devices

in children, a consolidation period of 4- months is recommended before the distractor is

removed, bur in older patients or patients with a compromised physical condition, 6 months

may be a minimal, and in some cases (e.g., multiple previous operations, patient who

smokes), consolidation may be considered for up to a year.

Differences between DO in facial region and long bone

Distraction of the jaws differs from distraction of the limbs in at least four ways:

1. The requirements for movement of the bony segments are more complex and requires

complex three-dimensional movements

2. There are complex soft tissue and muscle attachments.

3. Mobilization of the maxilla involves separation at several Sutures as well as osteotomy

across skeletal buttresses, and new bone formation must occur along the thin cortical

plates.

4. Facial aesthetic issues

5. Smaller devices often with multidirectional vectors of force

6. Beyond early childhood, the dental occlusion requires precise control of the magnitude and

direction of movement of the jaws.

Advantages

• Less mobilisation

• Reduced operative time

• Reduced hospital stay

• Expands soft tissue (CFM / Cleft palate)

• Avoid bone grafts (Donor site morbidity)

• ? Increased stability

• Reduced blood transfusion

• Avoid prolonged fixation

• Can clinically judge end point of treatment

• The ability to lengthen previously grafted bone.

• The ability to repeat distraction osteogenesis at a later date if need be.

• Allows larger movements

Disadvantages

• Second surgery required to remove distractor

• Pain during distraction phase

• Bony movements dependent on distractor position

• Distractor integrity crucial

• Scarring with external devices.

• Significant cooperation is required from both the patient and their family in most cases.

• Technical considerations include the very small size of the jaw, patient management after

surgery during the distraction phase, and avoiding tooth buds and the inferior alveolar

nerve during osteotomy and placement of the appliance. Stereolithographic models

facilitate treatment planning. Current models can identify the presence of tooth buds and

the nerve, as well as provide an opportunity to contour the device prior to surgery.

Complications

Non compliance and premature removal of distractor

Pain may be significant and prevent completion of treatment- usually from the TMJ's and

traction elastics can help to "un-load" the joints

Premature consolidation

Neurological damage

Failure to form a callus

Incorrect vectors and therefore incorrect occlusion

Relapse

VPI because of large movements

TMJ ankylosis

Failure to "grow" normal and need for more surgery

Applications

1. Mandibular distraction can be used to

A short mandihular ramus that must be lengthened, but with conventional surgery, the

musculature of the pterygomandibular sling does not adapt to lengthening of the ramus.

Distraction histogenesis, at least theoretically, could be a way to overcome this limitation

Mandibular hypoplasia with airway risk (e.g. Pierre robin neonate/child or nager’s

syndromes)

Mandibular retrognathia severe class ii skeletal pattern more than 10 to 15 m

Mandibular asymmetry hemifacial microsomia, ankylosed child temporomandibular joint

Post-mandibulectomy previous ablative surgery

Sleep apnoea diagnosed by sleep physician due to short ramus and body

2. Mid symphyseal distraction osteogenesis (MSDO)

3. Maxillary distraction

Bring the midface forward, and holds potential for people with cleft lip and palate and

patients with craniofacial syndromes. However, a Cochrane review by Kloukos in 2016

showed that there is only one small randomised controlled trial concerning the effectiveness

of distraction osteogenesis compared to conventional orthognathic surgery. Based on

measured outcomes, distraction osteogenesis may produce more satisfactory results;

however, further prospective research comprising assessment of a larger sample size with

participants with different facial characteristics is required to confirm possible true

differences between interventions.

Widening the Maxilla: SARPE as a Form of Distraction

4. augmentation of alveolar ridges

5. Regeneration of mandibular tissue following tumour resection show considerable promise.

Mid symphyseal distraction osteogenesis (MSDO)

A narrow mandible or a severely constricted mandible which could be associated with any

one of these syndromes (Russell Silver Syndrome, Treacher Collins Syndrome, Craniofacial

Microsomia, Pierre Robin sequence, Apert Syndrome)

In situations where you have a severe crowding in the lower arch but the upper arch has no

crowding and is normal. The patient has a very obtuse nasolabial angle and you cannot

afford to retract the upper

Reduced Intercanine width.

Narrow chin. If it is not desirable to widen the chin, a Genioplasty be performed to maintain

the genial width.

Types of distractors for MSDO

I. Tooth borne

Simpler with less surgical time

But….

Disproportional widening at the basal and dentoalveolar level. Del Santo et al. (2000) used

tooth borne devices and found insignificant increases in bicondylar, bigonial, and

biantegonial widths after mandibular widening. He demonstrated that dentoalveolar

expansion was greater than basal bone expansion with tooth-borne distraction devices.

Alveolar bone widening not supported by apical base, is usually unstable1

Periodontal problems, fenestration defects2

Buccal root resorption

Anchorage loss

II. Bone-borne

Others state that a greater skeletal effect can be achieved using the bone-borne appliance

owing to the fact that bone-borne distractors transfer the distraction forces directly to the

mandible (Conley and Legan, 2003; Bayram et al., 2007).

Malkoc et al. (2006) stated that parallel widening of the mandible could be achieved with ̧

tooth- and bone- borne distraction devices.

More skeletal changes (Mommaerts et al, 2008)

But….

Complications (infection, gingival recession, breakage)

Morbidity seemed to be higher

Higher cost

TMJ symptoms secondary to MSDO

Every 1 mm of mandibular midline widening = 0.34” of Lateral rotational movement of each

mandibular condyle (Computer simulation data by Samchukov et al)

However, identifying the cause of postoperative TMJ symptoms in patients treated with

distraction osteogenesisof the mandibular symphysis will be difficult.

Good occlusion and adaptation to gradual distraction ensures normal joints

MSDO is kinder to the TMJ due to slower rate of movement compared with traditional

orthognathic procedures with acute skeletal movements

Technique of MSDO

I. Pre-surgical Orthodontics

Align and level the maxillary arch

Obtain ideal maxillary arch

Placement of rectangular surgical maxillary arch

Fabrication of the intraoral distractor appliance

Placement of the distractor appliance on the mandibular arch

II. Post-Surgical Orthodontics

Placement of lower anterior brackets

Maintenance of the dental gap for 2 months with a plastic tooth

Orthodontic mechanics are undertaken 2 months after surgery

Periodically stripping of plastic tooth

Mobilization of teeth into the distraction site

Align and level, arch interdigitation and finishing followed by retention

TOOTH Movement after MSDO: When should we start?

I. Early tooth movement leads to

Root resorption (established in canine models)

Periodontal and bony defects in addition to potential loss of at least 1 tooth

II. Consolidation periods of at least 6-10 weeks before moving tooth into the new bone

Radiographs for evaluating the bone density in the gap

Mandibular Distraction Devices

These were placed ulilizing intraoral incision to visualize the osteotomy cuts and small stab

incision to place the pins on which the device was mounted.

Advantages

multiplane distraction can be more easily incorporated into the design,

the device can be removed easily.

Activation may be easier than with an internal device as well.

Disadvantages

excessive scarring

increased urgency to remove the device because it is so apparent.

the psychosocial problems associated with an external device may be such that the

consolidation period is shortened more than is reasonable.

an external distractor must be placed at distance from the mandible, which decreases the

rigidity of fixation.

Intraoral device

Types

Bone borne,

Hybrid (bone-borne and tooth-borne)

Tooth-borne

Advantages: Because an intraoral device is much less apparent, it can be left indefinitely

without great pressure from the patient

Disadvantages

Second surgical procedure is required for removal. In addition, when the ramus is being

lengthened, it may be difficult to activate the appliance entirely within the mouth.

Additionally, because the natural shape of the mandible is transversely wider in its posterior

aspect and narrower in its anterior aspect, the distractor appliances need to be adjusted by

creating a 5- to 8-mm step in the anterior fixation plates so that the distractor’s screw can

be placed parallel to the axis of distraction. If this is underestimated, the reciprocal forces

exerted on the mandible by the appliance will advance the mandible by moving the

proximal segment not only posteriorly but also laterally and exert very detrimental forces on

the TMJ, which will cause pain, dysfunction, and damage to the joints. In addition, there will

be lateral torque force against the condyle, loosening of the screws, and bending of the

appliance as the muscle forces bend the device. This situation is overcome with the use of

heavy class II elastics, 6 oz per side, during the activation and consolidation period

Maxillary Distraction Osteogenesis

Even though there is still an ongoing debate if rapid maxillary expansion is a version

of maxillary distraction osteogenesis, the first study on true midfacial distraction was

initiated on an ovine model by Rachmiel et al. in 1993 (Rachmiel et al. 1995), in

which they were able to achieve 36 mm of midfacial advancement on the

nasofrontal area with 7 % relapse in 1 year follow-up time.

This study sets a starting point for the correction of midfacial deformities by

distraction osteogenesis. Currently, the most frequent indications of maxillary

distraction osteogenesis can be counted as cleft lip and palate, and craniofacial

dysostosis associated with maxillary hypoplasia (Imola and Tatum 2002).

About 25 % of these cleft cases with class III malocclusion require secondary surgical

intervention to correct the maxillomandibular relationship (Ross 1987).

Types of distractors

1. Extraoral Distraction osteogenesis of maxilla with external tension devices, which takes anchorage

from the temporal region of the head using pin retained hemi halo and screw generated pull

by elastics, provided a solution to the sagittal discrepancies of cleft cases.

This device provided high advancement amounts on

the higher regions of the facial skeleton with low

relapse rate (Figueroa and Polley 1999; Figueroa et al.

2004)

It provide Greater movements in Multiplanar

Easy to adjust in DO phase

Psychosocial implications

Pin site infection and scars

Nerve damage

2. Intraoral Lin et al 1999, Rachmiel et al 2000

Avoid cutaneous scars

Socially more convenient

Need space for device

3d control not good

Archwise Distraction on Fixed Orthodontic Appliances

DOCKING SITE SURGERY, Once the two segments dock with each other, a second procedure

is required for uniting the two segments. The epithelial tissue between the two segments is

removed, as well as the hypotrophic bone edges from each disk, as described for the

mandible.

Class II Correction by Anterior Alveolar Distraction

This method has several advantages upon the conventional methods:

Shortening the treatment time: Conventional treatment protocol in such cases, in which

either orthognathic surgery or fixed functional orthodontic treatment is an option, takes 16–

24 months time. However, in this approach, alveolar distraction followed by dental implants

shortens the treatment time significantly

It can be performed under local anesthesia, and it is less invasive.

Room available for the tongue can increase significantly without any changes to the

muscular structure compared to the mandibular advancement.

Risk of hemorrhage and developing lip paresthesia is reduced.

As the tooth movement is less in this method, the root resorption risk and the periodontal

problem risk are reduced as well.

Alveolar DISTRACTION OSTEOGENESIS

• Patients medically compromised in whom major bone grafts are not indicated

• As an alternative for reintervention after an unsuccessful bone graft reconstruction

• A need to minimize costs related to the expense of prolonged surgery and hospitalizations

• After removal of benign tumors

• Reconstruction of gunshot wound defects

• Management of osteomyelitis

• Treatment for malunions or nonunions

VELOPHARYNGEAL INCOMPETENCE

The use of pharyngoplasties, pharyngeal flaps, and secondary push-backs to correct

velopharyngeal incompetence has been overcome by distraction osteogenesis of the

palatine bones to project the palate posteriorly. This technique permits titration of the

movement until the velopharyngeal competence is achieved, with predictable results and a

low morbidity, avoiding hyponasality, snoring, and nasal obstruction

Nerve Lengthening

Histologically, there are three possibilities after distraction. First, the nerve may exhibit

perineural thickening and decreased surface area of axons, various axonal abnormalities,

myelin thickening, and disruption of the lamellar pattern, and there is a direct relationship

between the number of millimeters advanced and alterations in the nerve. Second, the

nerve can be damaged during surgery and have no axonal connection, with the subsequent

development of fibrosis. Third, a distractor screw can be placed within the nerve canal and

cause damage to or displace neural structures.