BIOMECHANICAL CONSIDERATIONS IN DISTRACTION OSTEOGENESIS.pptx

1. BIOMECHANICAL CONSIDERATIONS
IN
DISTRACTION OSTEOGENESIS
Dr. Genoey George

2. INTRODUCTION
• Distraction osteogenesis of the craniofacial skeleton has become
increasingly popular as an alternative to many conventional orthognathic
surgical procedures.
• As in traditional combined surgical/ orthodontic procedures, the
orthodontist has a role in the preoperative assessment of craniofacial
skeleton, evaluation of occlusal function, planning the pre distraction and
post distraction orthodontics, and the distraction procedure itself.

3. INTRODUCTION
• Various factors combine to determine the ultimate selection and
placement of the distraction device on the mandible.
• The biological and mechanical forces that shape the regenerate, are key
elements in determining appliance position.
• The desired mandibular change in shape and function can be achieved by
selecting and controlling the force vectors that operate during active
distraction.

4. • The biological forces influencing the morphology of the bone regenerate
(newly formed bone) arise from the surrounding neuromuscular envelope.
Atlas Oral Maxillofac Surg Clin North Am 1999:7;1.)

5. Mechanical forces
• activation of the distraction devices,
• Specific orientation to skeletal anatomy,
• Application of intermaxillary elastics during the active phase of distraction,
• Intercuspation of the dentition.
• During the process of planning mandibular distraction, it is imperative to
consider the powerful impact of both biological and mechanical force
systems to anticipate their resultant effects.

6. DEVICE PLACEMENT

7. VERTICAL DEVICE
Treatment Planning and Vector Analysis of Mandibular Distraction Osteogenesis. Atlas Oral Maxillofac Surg
Clin North Am1999:7;1.)

8. It is desirable to overcorrect the shape of the growing mandible. The young
patient with greater future growth potential requires a greater amount of
overcorrection than is required for the older patient.
Grayson BH, LaBatto FA, Kolber AB, McCarthy JG. Basilar multiplane cephalometric
analysis. Am J Orthod Dentofacial Orthop 1985;88:503-516.
VERTICAL DEVICE

9. HORIZONTAL DEVICE
Treatment Planning and Vector Analysis of Mandibular Distraction Osteogenesis. Atlas Oral Maxillofac Surg
Clin North Am1999:7;1.)

10. • The gonial angle has been observed to open between the ramus and the body
when activating a device that is placed horizontally. In these cases, however,
there was a return of the predistraction gonial angle with subsequent
mandibular growth.
• It is important to overcorrect the sagittal jaw position of the young, growing,
severely retrognathic patient in order to compensate for the reduced growth
potential of the deficient mandible.
Grayson BH, McCormick SU, Santiago PE, McCarthy, JG. Vector of device placement and
trajectory of mandibular distraction.J Craniofac Surg 1997;8:473-480.
HORIZONTAL DEVICE

11. DEVICE DESIGN
UNIPLANAR DEVICE
• Single calibrated rod with two clamps
• Each clamp holds two 2-mm half-pins
• 20-24mm of bone posterior to last tooth bud

12. DEVICE DESIGN
UNIPLANAR DEVICE
LIMITATIONS
• Difficulty in predicting direction
• Inability to change direction
• Scarring
In 1994, McCarthy et al introduced this appliance to successfully lengthen the
mandible unilaterally in 3 children's having unilateral craniofacial microsomia
McCarthy JG. The role of distraction osteogenesis in the reconstruction of the mandible in
unilateral craniofacial microsomia. Clinics in plastic surgery. 1994 Oct 1;21(4):625-31.

13. BIPLANAR DEVICE
Molina and Ortiz Monasterio
• Two geared arms 5 cm in length
• Middle screw - change angulation
• Double osteotomy (horizontal in ramus and vertical in corpus)
• Two 2-mm pins in each segment of bone

14. BIPLANAR DEVICE
• Biplanar distractor provides an additional plane of correction
.
• Following a single or double osteotomy, one can distract both
vertically and horizontally.
• More severe mandibular hypoplasias, such as Nager’s syndrome, which
involves deficiency in more than one plane.
• In very difficult cases of mandibular hypoplasia, a double osteotomy may
be undertaken in order to obtain two callus sites. This allows a more rapid
distraction as well as the development of a mandibular angle.

15. MULTIPLANAR DEVICE
• Two distraction rods with sliding clamps connected by multiplanar hinge in
the middle
• Two arms extend with pin clamps at either end
• Each quarter turn results in 0.25 mm of expansion

16. Vertical and horizontal deficiencies may be addressed with these devices,
but adjustments in the angulation are limited during the distraction process and
the movements are independent of each other.
McCarthy JG, Williams JK, Grayson BH, Crombie JS. Controlled multiplanar distraction of the
mandible: device development and clinical application. J Craniofac Surg. 1998 Jul;9(4):322-9.

17. • It is important to note that the angular changes should commence after creation
of a substantial amount of regenerate.
• The regenerate is initially created through simple linear expansion. Angular
changes should occur concurrently with linear activation; failure to do so may
result in premature consolidation.
Williams JK, Rowe NM, Mackool RJ, Levine JP, Hollier LH, Longaker MT, Cutting CB, Grayson
BH, McCarthy JG. Controlled multiplanar distraction of the mandible, part II: Laboratory
studies of anteroposterior and superoinferior movements.J Craniofac Surg 1998;9:504-513.

18. Intermaxillary Elastics During Active
Distraction
• The vectors of distraction may be further modified by the use of
intermaxillary elastics during the active distraction phase.
• The occlusal response to elastic forces is secondary to molding of the
regenerate and dentoalveolar remodeling. Thus, intermaxillary elastics can
be used to modify the direction of skeletal change and fine tune the
occlusal outcome of distraction.

19. Intermaxillaryelastics at this point have been shown clinically
to alter skeletal and dental relationships. It is believed that the
observed occlusal response to elastic forces is secondary to
molding of the regenerate an dentoalveolar remodeling.

20. INTERMAXILLARY ELASTICS DURING ACTIVE
DISTRACTION
X. Qiu, H. Sun, M. Zhu et al., Using orthodontic elastic traction during the active period of distraction osteogenesis
to increase the effective vertical extension of hemifacial microsomia patients: A multi-center randomized clinical
trial, Journal of Cranio-Maxillo-Facial Surgery

21. INTERMAXILLARY ELASTICS DURING ACTIVE
DISTRACTION
In the experimental group, the overcorrection was enhanced compared with the control
group. The vertical overcorrection was longer in the experimental group, indicating that
there was less recurrence in the experimental group 6 months after the tractor was removed.
Thus, better effects can be achieved in the symmetry of bone and soft tissues after
distraction osteogenesis.
X. Qiu, H. Sun, M. Zhu et al., Using orthodontic elastic traction during the active period of distraction
osteogenesis to increase the effective vertical extension of hemifacial microsomia patients: A multi-
center randomized clinical trial, Journal of Cranio-Maxillo- Facial Surgery

22. BILATERAL MANDIBULAR LENGTHENING
• The effect of distraction device orientation on bilateral mandibular
lengthening, either alone or in combination with simultaneous
midsymphyseal widening, was evaluated in the transverse and sagittal
direction
• Mandible is in V shape when viewed in the transverse plane, the anatomic
axis of right and left side of mandible are not parallel to each other
• For this reason, proper orientation of the distraction appliance to
anatomic axis of mandible and desired direction of distraction in the
transverse plane is critical to prevent complications

24. • The distraction devices remained rigidly fixed to the bone segments during
distraction.
• The orientation of the distractors relative to the surface of the mandible
was constant during bone distraction.
• The proximal bone segments were fixed in space anteroposteriorly, so that
during distraction, the proximal segments could move only mediolaterally
as the distal bone segments translated anteriorly.

27. • Every 1 mm of bilateral mandibular corpus lengthening resulted in
approximately 0.5 mm of ICW increase.
• Likewise, every 5-degree increase of the AMA led to further widening of
the ICW by approximately 0.4 mm and 0.8 mm after 5 mm and 10 mm of
mandibular corpus lengthening, respectively.

28. Cope JB, et al: J Oral Maxillofacial Surgery 57:952, 1999

29. Cope JB, et al: J Oral Maxillofacial Surgery 57:952, 1999

30. BILATERAL MANDIBULAR LENGTHENING WITH
MIDLINE WIDENING
• They used to analyse the effect of distraction device
orientation when bilateral mandibular lengthening was
performed simultaneously with midline widening.
• In these models, a third osteotomy was simulated through the
middle of mandibular symphysis and a third distractor was
placed on the bone segments of the anterior mandible.

32. • The condylar rotation seen during midline widening, if not
compensated, can create in appropriate loading on the
articular surface of the condyles, potentially causing
degenerative changes.
• Investigation on adult Macaca mulatta by Harper et al.,
demonstrated histologic changes in the temporomandibular
joint after midline osteodistraction.
Harper RP, Bell WH, Hinton RL et al: Reactive changes in the temporomandibular joint
after mandibular midline osteodistraction, Br J Oral Maxillofac Surg 35:20, 1997.

33. • In other studies, three-dimensional positional changes of the
distracted mandibular segments and associated clinical
problems were analyzed during simultaneous intraoral
widening and bilateral lengthening on Papio anubis baboons.
Intercondylar width increased from 4.2 mm to 8.6 mm in all animals. These
changes were always combined with an increase in the intercondylar angle,
which varied from 9.8 degrees to 33.8 degrees
Bell WH, Gonzalez M, Guerrero CA, Samchukov ML: Intraoral widening of the mandible by
distraction osteogenesis: histologic and radiographic assessment, J Oral Maxillofac Surg
55:97, 1997

34. COMPENSATION

35. BILATERAL MANDIBULAR LENGTHENING IN
SAGITTAL PLANE
• The vertical relationship between the distal mandibular segment and the
maxilla during distraction is another important consideration of
preoperative planning for mandibular lengthening.
• An increase in lower anterior facial height occurs when the vector of
distraction is oriented parallel to the mandibular plane instead of being
parallel to the maxillary occlusal plane.

37. • There was a proportional relationship between the amount of LAFH
increase and the ADv.
• In Model V, as the ADv increased, the LAFH also increased.
• However, when the ADv increased to 50 degrees, almost 8 mm of LAFH
increase was generated during the same 10 mm of mandibular
lengthening.
• Clinically, vertical increase in LAFH may manifest as the development of
an anterior or posterior openbite depending on the location of the
osteotomy.
Each millimeter of distraction generated approximately 0.3 mm of LAFH

38. BILATERAL MANDIBULAR LENGTHENING IN
VERTICAL
• The vertical relationship between the distal mandibular
segment and the maxilla during distraction is another
important consideration of preoperative planning for
mandibular lengthening.
• An increase in lower anterior facial height occurs when the
vector of distraction is oriented parallel to the mandibular
plane instead of to the maxillary occlusal plane.

40. • The magnitude of the developing openbite is proportional to the amount
of distraction.
• An increase in the angle between the vector of distraction and the
occlusal plane proportionally increases the vertical deviation of the actual
direction of distraction from the desired (anteroposterior) direction, again
creating an anterior open bite, which can be calculated by the formula:
ΔLAFH = a x sin ADV

41. • In order to prevent the development of an anterior openbite,
placement of the distraction devices as parallel to the desired
direction of distraction (usually the maxillary occlusal plane)
must be a primary consideration during preoperative planning
of mandibular distraction.
• Several intrinsic factors (e.g., soft tissue tension, bone quality,
anatomy of the mandible seen in severe mandibular
deficiencies) often prevent placement of the distraction
devices parallel to the maxillary occlusal plane.

42. CONCLUSION
Although other extrinsic and intrinsic factors affect the Success
of mandibular lengthening and widening, the orientation of
distraction appliances relative to the anatomic axis of the bone
segments, occlusal planes, and desired direction of distraction is
one of the most important biomechanical parameters of
osteodistraction that must be considered during the
preoperative planning.

43. REFERNCE
• Craniofacial Distraction Osteogenesis - Mikhail L. Samchukov, Jason B Cope,
Alexander M Cherkashin.
• Orthodontic and Dentofacial Orthopedic Treatment – Thomas rakosi and
Thomas graber.
• Contemporary treatment of Craniofacial deformity – William R Profit,
Raymond P White, David M Sarver
• Seminars in Orthodontics, Vol 5, No 1 (March), 1999: pp 9-24 Barry 14.
Grayson and Pedro E. Santiago.
• Atlas Oral Maxillofac Surg Clin North Am 1999:7;1.)
• Treatment Planning and Vector Analysis of Mandibular Distraction
Osteogenesis. Atlas Oral Maxillofac Surg Clin North Am1999:7;1.)
• Grayson BH, LaBatto FA, Kolber AB, McCarthy JG. Basilar multiplane
cephalometric analysis. Am J Orthod Dentofacial Orthop 1985;88:503-516.
• Grayson BH, McCormick SU, Santiago PE, McCarthy, JG. Vector of device
placement and trajectory of mandibular distraction.J Craniofac Surg
1997;8:473-480.
• McCarthy JG, Williams JK, Grayson BH, Crombie JS. Controlled multiplanar
distraction of the mandible: device development and clinical application. J
Craniofac Surg. 1998 Jul;9(4):322-9.

44. REFERNCE
• Williams JK, Rowe NM, Mackool RJ, Levine JP, Hollier LH, Longaker MT, Cutting
CB, Grayson BH, McCarthy JG. Controlled multiplanar distraction of the
mandible, part II: Laboratory studies of anteroposterior and superoinferior
movements.J Craniofac Surg 1998;9:504-513.
• X. Qiu, H. Sun, M. Zhu et al., Using orthodontic elastic traction during the active
period of distraction osteogenesis to increase the effective vertical extension of
hemifacial microsomia patients: A multi-center randomized clinical trial, Journal
of Cranio-Maxillo-Facial Surgery