DISTRACTION OSTEOGENESIS AND ITS RELEVANCE IN CONTEMPORARY PRACTICE OF ORAL /MAXILLOFACIAL SURGERY

SEMINER PRESENTATION IN ORAL /MAXILLOFACIAL

SURGERY DEPT BY

DR ONAIWU I.M

Outline Introduction/Definition. History of Distraction Osteogenesis. Aims and objectives Indications Contraindications Histology/Pathophysiology Surgical Procedures Advantages/disadvantages Causes of failure Criteria for success Conclusion

Introduction Distraction Osteogenesis is a slow application of

force to a surgically disrupted bone thereby widening the gap and resulting in introduction of new bone as well as soft tissues. In the 1960’s and 1970’s many surgeons stressed the importance of bone grafting technique and extensive osteotomies to address this difficult scenario; research concentrated on methods of bone grafting to achieve good long term results but today we know that bone can regenerate itself without the use of bone grafts or bone growth promoting factors but by the mode of distraction. Hence, the concept of Distraction Osteogenesis.

Definition

Distraction Osteogenesis (DO) also called callostasis can be defined as the process of generating new bone by the slow stretching of callus in the gap between two bone segments in response to the application of graduated tensile stress across the bone gap.

History of Distraction of Osteogenesis

The technique of bone lengthening by DO was first described in 1905 by Codivilla, when he reported lengthening of a Femur by axial distraction forces. The first trail of distraction Osteogenesis on human mandible in unilateral micrognathia and asymmetry of the face was reported by Alexander A. Limberg in 1928.

CON’TD The technique remained undeveloped until

DR. Gavriel A. Ilizarov, a Russian physician, further developed the technique in 1950’s. His patients initially were fractures and non-unions. He utilized a primitive external ring fixator to compress the injured ends. By chance a patient reversed the compression rods, thereby distracting the bone fragments. Ilizarov’s observed new bone formation radiographically and pursued this new method both experimentally and clinically.

CONT’D Later he developed the techniques of bone

transportation and limb lengthening. Based on Ilizarov’s reports, numerous

studies have been conducted to extend the application of this technique for facial bone deformities.

Syndel et al in 1972 – to lengthen the mandible.

Michieli and miotti in Italy in 1977 Karp in 1990 e.t.c

Aims and objectives To lengthen the mandible (Unifocal treatment). To advance the maxilla/midface. Bone segment transportation (Bifocal distraction

treatment). Trifocal distraction treatment. Distraction for Alveolar Augmentation procedures. Distraction implantology. To allow multidimentional modelling of the

regenerated bone. To reduce cost effect of craniofacial surgery

Indications

Mandibular Distraction Osteogenesis.

Maxillary Distraction Osteogenesis. Mid facial and/or cranial Distraction

Osteogenesis. Simultaneous mandibular and

maxillary Distraction Osteogenesis. Distraction implants.

Mandibular DO Hemifacial microsomia Teacher – Collins Syndrome. Congenital micrognathia Pierre Robins Syndrome. Retrognathia/facial cleft Craniofacial microsomia Segmented bone defect (Trauma/pathological

disease) Transverse discrepancies Alveolar Augmentation Hypoplasia due to trauma or TMJ ankylosis Obstructive sleep apnoea

MAXILLARY DO

Orofacial Clefts Unilateral cleft lip and palate Bilateral cleft lip and palate Undefined cleft Unilateral cleft palate

Cleidocranial dysostosis Maxillary atrophy Alveolar Augmentation

Midfacial and/or cranial DO . cranial synostosis

crouson’s syndrome apert syndrome undefined craniosynostosis unilateral coronal synostosis saggittal synostosis carpenter’s syndrome

midfacial cleft severe midface atrophy

Simulteneous mand/max DO

Hemifacial microsomia Teacher’s Collins synd

Distraction Implants

Alveolar Atrophy

Contraindications of DO Insufficient quantity or quality of bone which

inhibit fixation of the device such as in osteoporosis

Inability to comply with the post operative distraction regimen and follow up schedule

Metal Allergies Infections Certain neuropsychotic disorder e.g. Epilepsy Immunosuppression Compromised medical condition

HISTOLOGY In the latency period, haematoma

formation begins following osteotomy The gap between cut ends is composed of

fibroblast & collagen within a matrix of undifferentiated cells

Early bone formation is as a result of trabecullae of bone which extend from bony ends. Bone matrix is lay down by activation of osteoblast.

Remodeling takes place with bone apposition & resorption. Osteoclast increases in number.

Pathophysiology

Distraction Osteogenesis is based on the tension-stress theory of Ilizarov which states that slow steady traction of tissues causes them to be metabolically active, resulting in increase in their proliferating and biosynthetic functions (histogenesis)

CONT’D The mechanical forces are directed

predominantly away from the site of the surgically disrupted bone.

Distraction Osteogenesis takes place by intramembranous ossification by induction of the native tissue. The newly formed bone between the distracted ends will result in a stable lengthening.

SURGICAL PROCEDURESClinical protocols

Patient selection The decision to use Distraction Osteogenesis

should be based on the following criteria: Age of patient (paediatric, adolescent and adult

patient) Severity of the anatomical malformation which

can affect the soft tissue and bony skeleton to a varying degree.

Potential for bone growth depending on the etiology.

Functional and aesthetic effects Secondary malformations Psychological considerations.

Treatment Phase Presurgical, operative, latency, distraction,

consolidation, orthodontic phases. Presurgical phase This involves:

Clinical examination Clinical photographs Study models Model analysis Preparation of templates Biochemical investigations

Radiographic investigations

OPG PA mandible True lateral cephalogram computerized Tomography (plain,

contrast and 3-D images) prediction Tracings

Other investigations

selection of Distraction vector Selection of Distraction device

OPERATIVE PHASEThis involves osteotomy

and placement of device Osteotomy This involves surgical separation

of bony fragments. Osteotomy is performed using a small reciprocating saw or a fissure bur depending on the type of device you want to fix.

Osteotomy is 90% completed before the device is applied, then the osteotomy is completed.

Cont’d

LATENCY PHASE This is the initial healing phase

before application of distraction force. i.e. for callus formation. This varies from 3 – 7 days.

Cont’d DISTRACTION PHASE Pulling of bone segments apart via

activation of distraction device. RATE OF DISTRACTION This can be defined as the number

of millimeters per day at which the bones surfaces are stretched. The rate of 1mm a day is considered optimal.

ORIENTATION OF THE DEVICE For optimal osteogenesis, recent reports

recommend orienting the distraction device parallel to the desired direction of distraction this they say is known to produce tensile strains as compared to compression, this provides the most favourable conditions for osteogenesis.

RHYTHM OF DISTRACTION It can be defined as the number of

distractions per day usually in equally divided increments to total the rate.

The rhythm may vary from one cycle per day of 1mm to 0.25mm four times per day or 0.5mm twice daily

DISTRACTION DEVICE Distraction devices can be classified as: Extraoral distraction devices Intraoral distraction devices SELECTION OF DISTRACTION DEVICE It is dependable on the following factors Type of skeletal deficiency Desired vector of Distraction Compliance of the patient Availability Cost factor

SELECTION OF DISTRACTION DEVICE

It is dependable on the following factors

Type of skeletal deficiency Desired vector of Distraction Compliance of the patient Availability Cost factor

DEVICE REQUIREMENTS Any device should allow for: Transfer of distraction forces directly to the desired

bone ends. Provide for adequate rigidity until osseus consolidation

occurs. Examples of Extraoral distractor devices

Monodirectional appliances Bidirectional appliances Multidirectional appliances

These extraoral appliances are attached by precutaneous pins to the bones. These pins are then attached to fixations clamps. These fixation clamps are in turn connected by a linear distraction bar which when activated pushes the clamps and the corresponding bone segments apart.

DISADVANTAGES OF EXTRAORAL DISTRACTION Pin loosening Pin tract infection External scars Hypertrophic scars Damage to facial nerve Damage to tooth buds Non-compliance of patients Breakage of appliance

INTRAORAL DEVICES

Examples include Bone – bone borne Tooth – bone borne Implant – tooth hybrid devices Implant – implant hybrid devices Extra – mucosal Internal buried devices

ADVANTAGES OF IO -DO No external scars Simple application Simple activation Good patient compliance No damage to facial nerve Near total concealment of the devices Superior psychological tolerance by the patient Does not limit patients activity level. DISADVANTAGES Does not allow multidimentional lengthening A second surgery is required for removal

CONSOLIDATION PHASE

This may be defined as the number of days or months from the operation when the distraction device can be removed and the bone can be exposed to unprotected load bearing forces. This period generally ranges from 6 – 10 weeks. This allow for adequate consolidation and maturation of the callus. New bone formation can be monitored with serial radiographs or CT scan

Orthodontic phase

Involves orthodontic mgt of the distorted occlusion after DO

Usually 3-6 months after consolidation phase.

Post operative period 3-7days post op; maintain fixation Start activation 0.5mm twice daily(1mm per

day for adult and1.5mm per day for px <6yrs) Check occlusion, oral commissure, progress of

distraction. Maintain device in place about 8 wks Long term follow up Overcorrection in children is preferable

ADVANTAGES OF DISTRACTION OSTEOGENESIS Relatively simple operative technique, involving bone

lengthening and soft tissue Good long term stability Potential for growth in children Avoidance of bone grafts Expanded bone is of high quality Can be performed as early as 2 yrs of age. Enables surgeon to have post operative control Shortens hospital stay Feasible to distract bone graft or irradiated bone Results are apparent early Reduced likelihood of relapse Multi dimensional distraction Cost effective

DISADVANTAGES Skin scars with extraoral devices Damage to facial nerve Damage to inferior alveolar nerve Damage to tooth gem Premature consolidation especially in

children Transient changes in TMJ Infection Non-union/inadequate bone formation Device failure.

CAUSES OF FAILURE OF DISTRACTION OSTEOGENESIS Ischaemic Fibrogenesis: Due to inadequate local blood supply during

distraction. Fibrous tissue forms in the distraction gap, bone columns do not form from the avascular lost bone surfaces.

Cystic Degeneration: Occurs when there is blockage of venous outflow from

the system. Fibrocartilage Non-Union: Occurs with an unstable external fixation where

microfractures, haemorrhage and cartilage interposition occurs

Buckling or Bending of the Regenerated bone: Occurs when the fixation device is unstable or

removed prematurely.

Criteria for success of craniofacial Distraction Osteogenesis Planned distraction distance is obtained Planned distraction vector is obtained No pseudoarthrosis No nerve injury No tooth damage No persistent pain, discomfort or infection No dentoalveolar compensation. Occlusal balance and adequate function Patient satisfaction with aesthetic and psychological

outcome Skeletal stability 1 year after the end of the contention

period

CONCLUSION

From the foregoing it is obvious that the relevance of DO in modern day oral/maxillofacial surgery and its reliability in bone augmentation in clinical practice cannot be overemphasized.

THANK YOU.