Comprehensive description of distraction osteogenesis for craniofacial deformities

1. Slide 1
Distraction
Osteogenesis
Dr (Col) Suresh Menon
Vydehi Institute of Dental Sciences
Bengaluru

2. Slide 2
Sub headings
• Definition
• Need for distraction
• History
• Biology
• Types
• Factors influencing distraction
• Diagnosis & treatment planning
• Device selection
• Vector planning
• Presurgical orthodontics
• Indications

3. Slide 3
Sub headings
• Distraction histiogenesis
• Simultaneous distraction
• Transport distraction
• Alveolar distraction
• OSA
• Complications
• Current concepts
• TMJ ankylosis

4. Slide 4
Definition
 Biological process of new bone formation between the
surfaces of bone segments that are gradually
separated by incremental traction.

5. Slide 5
Need
There are limitations with acute advancement of osteotomized
bone segments due to:
(a) Inability to stretch soft tissues
(b) Surrounding soft tissues cannot adapt to the new position
resulting in degenerative changes, relapse and compromised
function and aesthetics
(c) In the midface most deficiencies involve all three planes;
vertical, sagittal and transverse
(d) Orthognathic surgery can only be taken up after active
growth ceases unlike distraction which can be performed in
infancy too.

6. Slide 6
Instability after osteotomy
• Int. J. Oral Maxillofac. Surg. 2016; 45: 1501–1507
Midface advancement – 15 % relapse
• Erbe et al J Craniomaxillofac Surg 24:109, 1996 - After 59
months of follow-up, reported 40% relapse after 4.6 mm
maxillary advancement.
• Hirano and Suzuki Cleft Palate Craniofac J 38:1, 2001 -
After 6.9 mm movement, 24.1% in the horizontal plane and
70% in the vertical plane relapsed.
• Thongdee and Samman Cleft Palate Craniofac J 42:664,
2005 - 31% in the horizontal plane and 52% in the vertical
plane, as well as 30% rotationally.
• Most relapses occurred in the first 6 months after surgery

7. Slide 7
Stability after distraction
 Wiltfang et al Br J Oral Maxillofac Surg 40:473, 2002 – 2
Year follow up
Intraoral distraction 5.55% relapse
Extraoral distraction 7.92% relapse
 Figueroa et al Plast Reconstr Surg 114:1382 (discussion
1393), 2004
3 Year follow up using RED – Mean advancement -9.6 mm
 Rachmiel et al Int J Oral Maxillofac Surg 34:473, 2005 - 2-
year follow-up - Mean of 13.66 mm advancement with
relatively stable results, along with a relapse rate of 7.32%
after 2 years

8. Slide 8
History
• Codvilla 1905 : 1st limb lengthening procedure using external
skeletal traction after oblique osteotomy of femur
• In 1951, Gavril Ilizarov performed corticotomy for limb
lengthening. He postulated the Ilizarov effects
• 1973-Snyder did the 1st experimental distraction on dogs’
mandible
• 1989 – Joseph McCarthy performed the 1st extra oral distraction in
human craniofacial region
• 1995 – Polley & Figuera designed the rigid external distractor for
midface
• 1996 – Chin & Toth did the 1st alveolar distraction
• 1999 -1st simultaneous distraction by Molina & Ortiz Monasterio

9. Slide 9
Biology
• Traction force applied to segments lead to
stretching of callus.
• This generates tension in the tissue stimulating new
bone formation parallel to vector of distraction.
• In addition, it also creates tension in the
surrounding tissues, initiating a sequence of
adaptive changes in the surrounding tissues known
as distraction histiogenesis.

10. Slide 10
Biology
TYPES
• Depending on the place where tensional stress is induced,
distraction can be classified as (a) Physeal distraction
(b)Callotasis
• Physeal distraction is the distraction of the bone growth
plate and can either be distraction epiphysiolysis – where
the separation occurs at 1-1.5 mm per day resulting in bone
formation, or chondrodiatasis; where a slow rate of
separation less than 0.5 mm per day is done.
• Callotasis refers to gradual stretching of the reparative
callus forming around bone segments interrupted by
osteotomy or fracture.

11. Slide 11
Procedure
 Osteotomy
 Placement of distractor
 Latency
 Distraction
 Consolidation

12. Slide 12
Osteotomy
• This triggers an evolutionary process of bone repair
involving recruitment of osteoprogenitor cells followed by
osteoinduction.

13. Slide 13
Latency
• This is the period from bone division to onset of
traction.
• It represents the time allowed for reparative callus
formation.
• The sequence of events is similar to fracture
healing.
• In growth of vasoformative elements and cellular
proliferation occurs in this inflammatory phase
lasting 1-3 days.
• The soft callus then begins to form.

14. Slide 14
Distraction
• This is characterized by the application of traction forces to
the osteotomized bone segments, gradually pulling them
apart resulting in new bone formation within the
progressively increasing intersegmentary gap.
• The tension stress stimulates changes at the cellular &
subcellular level resulting in prolonged angiogenesis and
increased fibroblast proliferation. Capillaries grow into this
fibrous tissues and trabeculae form by the 2nd week of
distraction.

15. Slide 15
Consolidation
• This is the period between the cessation of
distraction & removal of the device. This is the time
required for complete mineralization of the
distraction regenerate.
Remodeling
• This the period from complete functional loading to
complete remodeling of the newly formed bone.

16. Slide 16
Factors for success of distraction
Biomechanical parameters:
• Extrinsic or fixator related
• Intrinsic or tissue related
Biological parameters:
• Lower power osteotomy with maximum preservation of osteogenic tissues
& periosteal/endosteal blood supply
• Adequate period of latency period
• Stable but not rigid fixation
• Precisely calculated direction of distraction
• Optimal rate & rhythm of distraction
• Sufficient time for consolidation & remodeling

17. Slide 17
Diagnosis & treatment planning
• Treatment planning should consider all issues
related to surgical correction as well as the
potential for future skeletal growth & development,
the need for over correction & possible future
operations.

18. Slide 18
Clinical examination
 Assessment of facial aesthetics
 Racial diversity
 Ideal proportions
 Facial symmetry

19. Slide 19
PA CEPH LATERAL CEPH
Cephalometric analysis

20. Slide 20
Classification of devices
External devices Internal devices
Sub cutaneous Intraoral
Tooth borne Bone borne Hybrid
Mandibular intraoral devices can also be divided into ramus or
body distracters
They can also be divided into unidirectional or bi/multi directional
devices

21. Slide 21
Device selection
The device selection depends on mechanical capabilities &
patient acceptance.
External devices offer excellent control of bone segment
movement & are available in longer lengths. They are much
easier to place & maintain and are easy to remove on
completion.
Internal devices are more aesthetically acceptable. However
they are more difficult to place. They would also require a
second surgery to remove the device.

22. Slide 22
Device selection
 Deficiency site & area
 Complexity of the asymmetry
 Economics

23. Slide 23
Device selection
Extraoral
 Greater magnitude
 Multiaxial distractors
 Better directional control
 Interim changes possible
 Cumbersome
 Pin track scars

24. Slide 24
Device selection
• In mandible the intraoral devices are
preferred due to the ease of application and
comfort of the patient. Depending on the area
involved, the device can either be a vertical or
a horizontal distractor.

25. Slide 25
• In the midface, both internal and external distracters
are in use.
• The internal distracters are ideal for limited
advancement and are placed on the maxillary
anterior aspect/zygomatic buttress region.
• Rigid External Distractor (RED) are ideal in cleft
cases since the scarred tissues cannot be
manipulated by internal devices.
Device selection

26. Slide 26
Midface
Intra oral distractor

27. Slide 27
Midface
Extra Oral Device

28. Slide 28
Disadvantages of external devices
• Bulky affecting social life
• Facial scars are left
• Potential for injuring oneself
Advantages
• Can produce larger movement of segments
• Ability to change vector during the distraction
Disadvantage of internal devices
• Difficult to place within the confines
• Limited bone available for fixation
Advantages
• Does not interfere with normal routine

29. Slide 29
Vector planning
The distraction vector defines the desired direction that
the distal segment must move during lengthening.
Factors that affect the vector include osteotomy design
& location, device orientation, masticatory muscle
influence, occlusal interferences, device adjustment
& orthodontic applied forces.
Device orientation is the primary factor that influences
the vector. Ideally devices should be placed parallel
to the vector desired.

30. Slide 30

31. Slide 31
Craniofacial distraction
• 3 dimensional problem
• Multi vector problem

32. Slide 32
Factors influencing the vector
• The appliance is usually placed on the lateral surface, far
from the midline center of gravity
• The distractor only takes up a small portion of the wide
mandibular surface
• Physiological forces of occlusion and masticatory muscle
contraction
J Oral Maxillofac Surg 64:610-619, 2006

33. Slide 33
Factors influencing the vector
• Pull of the masseter, temporalis and medial pterygoid results
in anteroinferior rotation of the distal segment
Hendrickx K, Mommaerts MY, Jacobs W, et al: J Craniomaxillofac Surg
27:383, 1999

34. Slide 34
Sagittal Vector
• Distractors oriented parallel to the body of the
mandible caused a lateral displacement of the
posterior components of the distractor
• Inappropriate forces in the TMJ due leading to
degenerative changes
• Potential clinical complications: Bending of the
distraction device or loosening of fixation screws
or pins
Samchukov ML, Cope JB, Harper RP, et al:
J Oral Maxillofac Surg 56:51, 1998

35. Slide 35
Sagittal Vector
• Placing the distractor parallel to inferior border due to anatomical
constraints can cause undesirable occlusal changes.
• The vertical relationship between the distal mandibular segment and
maxilla is an important consideration.

36. Slide 36
Vertical vector
• Vertical distraction along the ramus long axis results
in oblique distraction as the ramus is not at right
angles to the occlusal plane. Ideally the distractor
should be placed perpendicular to the occlusal
plane.

37. Slide 37
Transverse vector
• Indications: A narrow mandible
• Selection of the osteotomy site : The symphyseal osteotomy
does not necessarily have to be made between the central
incisors.
• If the expansion is bilateral, the vertical osteotomy may be
placed anywhere between the four mandibular anterior teeth
• If the expansion is unilateral, the vertical osteotomy is made
between the cuspid and the ipsilateral lower lateral incisor.

38. Slide 38
Transverse vector

39. Slide 39
2 planes of deficiency
• Oblique placement of the distractor will achieve
simultaneous vertical and horizontal movements of the
distal segment. This can be changed to more vertical or
more horizontal depending on the magnitude of movement
desired.

40. Slide 40
Problems in vector
• Open bite
• Multifactorial
1. Myofunctional problems (tongue, habits, tissue stretch, etc.)
2. Flexibility of the distractor-Flexible distractors allow bending
of the mandible and an open bite will develop.
3. Orientation of monodirectional distracters
Journal of Cranio-Maxillofacial Surgery (2010) 38, 19e25

41. Slide 41
Floating Bone Concept
Hoffmeister B, Marks CH, Wolf KD; International Journal of Oral and
Maxillofacial Surgery, Volume 28, Supplement 1, 1999, Page 90

42. Slide 42
Parallelism of devices

43. Slide 43
Midface
 The greatest disadvantage of single vector
distraction in the midface is that the device
cannot be manipulated to move the maxilla
in 3 dimensions.

44. Slide 44
Vector control in IO devices

45. Slide 45
Vector control in IO devices
Vector Guidance Splint for Internal Maxillary Distraction J Oral
Maxillofac Surg 65:1852-1856, 2007

46. Slide 46
Future growth & overcorrection
• Structural & functional result with distraction is
definitive for skeletally mature patients
• It may be a temporary treatment objective for
growing patients
• Therefore skeletal age and future growth potential
must be considered in these individuals.
• Sometimes overcorrection can be performed to
reduce total number of surgical procedures.

47. Slide 47
• The orthodontist is an integral part of
treatment planning for predistraction
orthodontic preparation, orthodontic therapy
during distraction & consolidation & post
consolidation management.

48. Slide 48
• Predistraction assessment of the craniofacial skeleton and
occlusal function
• Plans distraction device placement and the predicted vectors of
distraction
• The primary aim is to move the teeth to near ideal positions
relative to basal bone.
• Another component of presurgical orthodontics is fabrication of
distraction stabilization appliances. These include maxillary
expansion appliance or mandibular lingual holding arch.
Presurgical orthodontics

49. Slide 49
Presurgical orthodontics

50. Slide 50
Orthodontics during distraction
• The “floating bone concept” of Hoffmeister where the device
is removed before consolidation and orthodontic forces are
used to achieve the treatment end position before allowing
consolidation of the callus.
• Closely monitor the patient during the active distraction
phase, using intermaxillary elastic traction, sometimes
combined with guide planes, bite plates, and stabilization
arches, to mould the newly formed bone (regenerate) while
optimizing the developing occlusion.

51. Slide 51
Post consolidation orthodontic therapy
This is primarily for eruption guidance and final alignment of
the dentition including closure of any open bite.

52. Slide 52
Mandibular Indications
1. Sagittal deficiency
2. Inadequate vertical length
3. Transverse deficiency
4. OSA
5. Congenital deformities like HFM

53. Slide 53
Midface distraction
 Indications:
1. Moderate and severe retrusion that needs large
advancement as in CLP
2. Forward and downward lengthening of the maxilla
without need for graft

54. Slide 54
Simultaneous distraction
• The efficacy of simultaneous distraction is best seen in the
management of Hemifacial microsomia. This deformity
involving the 1st brachial arch affects both hard and soft
tissues.
• The main skeletal deformity is mandibular hypoplasia and
may also involve the maxilla and zygoma.

55. Slide 55
Procedures
Deformity : Includes maxilla
 Simultaneous distraction of mandible &
maxilla using individual distractors
Paolo Scolozzi et al Plastic and Reconstructive surgery; April 2006 ; 1530 - 1540

56. Slide 56
Procedures
 Simultaneous maxillomandibular distraction osteogenesis
 Le Fort I osteotomy with alveolar distraction device
 Intraoral vertical ramus osteotomy
Kensuke Yamauchi et al J Oral Maxfac Surg Vol 63 Issue 9 Sep 2005 1398-
1401

57. Slide 57
Procedures
• NAVID distractor
• Maxillary-driven simultaneous maxillo-mandibular
distraction for hemifacial Microsomia
• J Cr Maxfac Surg 39(2011) 549-553

58. Slide 58
Single distractor in ramus

59. Slide 59
Timing of Surgery
Early Treatment
• Age - Mixed dentition stage
• Optimize growth potential by placing structures in a more
normal anatomic position
• Releasing restricted growth of adjacent skeletal structures
• Improve the appearance and socialization of the child
Leonard B. Kaban, Bonnie L. Padwa J Oral Maxillofac Surg
56:628-638, 1998

60. Slide 60
Late Treatment
• Postpone the distraction until growth has ended
• Functional treatment modalities for growth
modification
• Prolong consolidation period
• Orthopedic or functional devices during the
retention period
• Polley JW, Figueroa AA, Liou EJW, et al Plast Reconstr
Surg 99 : 328 , 1997
• Rune B, Selvik G, Sarnas IN, et al. Cleft Palate J 18128,
1981

61. Slide 61
Transport distraction
• This method involves the gradual movement of a free
segment of bone across an osseous defect.
• After the transport segment reaches the residual target bone
segment, compression forces are applied at the docking site
until the bone margins of both segments are fused.
• When the bridging is complete, the leading edge of the
transport disk is covered by fibrocartilage and this must be
removed for the final union by compression of the two
segments.
Indications:
• Mandibular continuity defects
• Calvarial defects
• Construction of a neocondyle
• Reconstruction of alveolus in cleft maxilla

62. Slide 62
Alveolar distraction
Indications:
• Atrophic alveolar process due to periodontal disease,
trauma or congenital deformity
• Segmental deficiencies of the ridge that compromise the
implant placement
• Defect due to removal of pathology
• Orthodontic indications in ankylosed teeth
• Distraction of fibula graft for increasing the height
• Narrow alveolar ridges
• Gradual vertical shift of an osseointegrated implant along
with surrounding alveolar bone

63. Slide 63
Contraindications:
• Severely atrophic mandible
• Osteoporosis
• Advanced age
Types of devices:
• Extraosseous or subperiosteal distractor
• Endosseous distractor
• Endosseous distraction implant : This represents a
combination of distraction device and an endosseous dental
implant

64. Slide 64
Advantages of alveolar distraction:
• No morbidity of donor area
• Less possibility of hard tissue exposure and less
chances of graft resorption
• More predictable volume of bone
• Shorter bone consolidation period
Complications :
• Lack of device activation
• Paraesthesia of the nerve
• Incorrect vector of the transport segment
• Dehiscence and plate exposure
• Immature bone at time of removal of distractor
• Fracture of screw

65. Slide 65
OSA
Obstructive sleep apnoea is a much underdiagnosed condition
in children.
One of the primary causes is the deficient maxillomandibular
bone stock in the sagittal plane.
While surgical procedures involving nasal cavity, pharynx and
tongue have been in vogue, the role of advancing the
maxillomandibular component has been recognized as a
good alternative
The advantage of doing distraction in very young children has
been a boon in the advancement of mandible or both
mandible and maxilla in improving the nasopharyngeal and
oropharyngeal airway dimensions in these patients.

66. Slide 66
Mandibular Deficiency
Obstructive Sleep Apnoea

67. Slide 67
Complications in distraction
• Mistakes and complications
• A mistake is an inattentive action that results in a
deviation in the course of the treatment, thereby
leading to the development of a complication
• Complication is an unexpected deviation from the
treatment plan that without appropriate correction
will lead to worsening of the existing, development
of a new or recurrence of the initial pathologic
process.

68. Slide 68
Potential mistakes:
• Iatrogenic
• Primary: Made during treatment planning & include
improper indications and unrealistic treatment
objectives
• Secondary: Due to poor decisions when correcting
a developing complication
• Technical : These are made during the surgical
procedure when fitting the device or applying
distraction
• Patient related mistakes are often due to wrong
activation of the device.

69. Slide 69
Potential complications
• Regenerate malformation: this could be hypoplastic regenerate,
hyperplastic regenerate or regenerate fracture
• Axial deviations: These are usually due to iatrogenic mistakes
and should be corrected by replacing/reorienting the devices.
• Soft tissue over stretching
• Infection
Hardware related
• Difficulty in device activation
• Device rotating backwards
• Improper vector
• Inadequate device length
• Unstable device
• Device deformation or breakage
• Pin loosening

70. Slide 70
Hard and soft tissue related
• Pain at bony generate site
• Hypertrophic scar
• Cyst caused by pins
• Psychological problem
• Neuropraxia
• Infection
• Trismus during treatment or device removal
• Parotid gland injury
• Tooth follicle damage
• Premature ossification
• Fibrous union
• TMJ ankylosis and degenerative changes
• Incomplete osteotomy

71. Slide 71
DO in ankylosis
• The role of distraction in TMJ ankylosis is twofold:
(a) Reconstruction of Ramus condyle unit
(b) Correct the deformity
Reconstruction of Ramus condyle unit
• Osteoplastic bone flap : Vascularized portion of the
mandibular ramus is used to fashion a ramus–condyle unit
(RCU). A transport disc is fashioned from the ramus

72. Slide 72
Correction of the deformity
2 schools of thought in sequencing the surgical procedures of
ankylosis release and distraction in ankylosis.
1. 1st school of thought: Release of ankylosis followed by
distraction
Points favoring it:
• Addressing the patients’ primary problem of limited mouth
opening first
• Allow good physiotherapy in the post op phase before
correcting the deformity
• Ensure dental decompensation after adequate mouth opening
before planning distraction
2. 2nd school of thought: Release of ankylosis after distraction
Points favoring it:
• Concomitant obstructive sleep apnoea present

73. Slide 73
Distraction osteogenesis in a boy who had right sided
TMJ arthroplasty
• Evaluate clinical features depending on the age of the
patient and time of onset of ankylosis
• Evaluate and define the quantum and area of deficiency in
the unilateral mandible
• Plan the device accordingly
• Vector determination depending on planes of involvement
• Presurgical orthodontics
• Distraction
• Possible genioplasty during removal of distractor

74. Slide 74
Orthognathic surgery v/s distraction osteogenesis
Advantages of orthognathic surgery
• Most clinicians would agree that the predictability of
obtaining the desired occlusion is very high with BSSO
when advancing a retrognathic mandible. With BSSO, the
patient’s final occlusion will be obtained intraoperatively
• Single surgery to achieve desired results
Disadvantages of orthognathic surgery:
• Neurosensory deficit of inferior alveolar nerve
• The unpredictable stability associated with BSSO
• Soft tissue resistance
• Velopharyngeal incompetence
• Age

75. Slide 75
Advantages of distraction
Stability and relapse
Growth after distraction
Soft tissue profile changes
Velopharyngeal changes
Psychological effects
No neurosensory deficit
TMJ

76. Slide 76
Disadvantages of distraction
• Attaining the predicted occlusion using DO has been much
more difficult and requires the distractors be perfectly
positioned to provide the appropriate vector to obtain the
desired outcome.
• Overall treatment time longer.
• Mechanical distractor failures, loosening of the distractors,
infections around the distraction devices
• Premature consolidation
• The cost of treatment
• Require a second surgical procedure to remove them.

77. Slide 77
Discuss with examples the current
concepts and controversies in
management of craniofacial
anomalies

78. Slide 78
Current concepts
Automatic distraction osteogenesis (British Journal of Oral and
Maxillofacial Surgery 43 (2005) 324–328)
• An increase in the frequency of distraction improves the
quality of bone formation. This is difficult to achieve using
manually activated devices, as the maximum frequency that
can be achieved with these devices is four to five steps for
1mm lengthening each day.
• This is the first case of lengthening of the human mandible
by automatic microincremental distraction using this device.

79. Slide 79
• Modification of the osteotomy design in body
distraction to SSO design for more bone to bone
contact. (Journal of Cranio-Maxillofacial Surgery
(2001) 29, 165-173)
• Anterior maxillary distraction using tooth borne
device in hypoplastic cleft maxilla thus avoiding and
compromise in the velopharyngeal mechanism (J
Oral Maxillofac Surg 69:e542-e548, 2011
Current concepts

80. Slide 80
Curvilinear DO (J Oral Maxillofac Surg 67:996-1008, 2009)
• This design is based on a computed tomography (CT)
based 3-dimensional (3D) treatment planning system to be
used with a semiburied curvilinear distraction device to
obtain advancement and counterclockwise rotation of the
mandible.
• The concept and use of a fixed trajectory curvilinear
distraction device to accomplish 3D mandibular movements
is described.
Current concepts

81. Slide 81
Magnetic activation(Journal of Cranio-Maxillo-Facial
Surgery 44 (2016) 684e688)
• Craniofacial distraction needs to be done through a
transmucosal or transcutaneous activator, leading
to multiple potential problems such as bacterial
infection, activator rod discomfort, chronic
wounding, rod cover up, etc.
• This describes a prototype device based on the
principles of static magnetic field.
Current concepts

82. Slide 82
Amniotic fluid (Int. J. Oral Maxillofac. Surg. 2015; 44: 404–411)
• A rich content of growth and trophic factors such as
epidermal growth factor (EGF), FGF, and insulin-like growth
factors I and II (IGF-I and IGF-II), which are critical for
development, have been identified in human amniotic fluid
(HAF). Additionally, hyaluronic acid (HA), hyaluronic acid
stimulating activator (HASA), chondroitin-4- and - 6-
sulphate, dermatan sulphate, and heparan sulphate have
been identified in HAF.
• This experimental study suggests that the local injection of
HAF in the distraction gap after DO increases new bone
formation and the number of fibro- blasts significantly.
Current concepts

83. Slide 83
3D printing (British Journal of Oral and Maxillofacial Surgery
55 (2017) 74–76)
• Introduction of 3D models help visualize transport vectors,
and the footplates can be adapted preoperatively, so that
they lie against the bone. The device can be secured to the
model and the distraction simulated and altered until the
desired reconstruction is achieved.
• Passive movement can be done by prebending the
footplates, because it prevents uneven traction through the
footplate screws.
Current concepts

84. Slide 84
1. Endoscopic technique
2. Resorbable device
3. Osteotomy free distraction across suture sites in
infants
4. VGEF adenovirus & BMP-2 adenovirus show earlier
ossification
5. Endothelial progenitor cells (Adult stem cells)
Future concepts

85. Slide 85
Controversies
• Age of intervention
• Choice of surgery
• Choice of device
• Sequence of surgery

86. Slide 86
Criteria for success of craniofacial
distraction osteogenesis
Criteria %
1. Planned distraction distance is obtained 10
2. Planned distraction vector is obtained 10
3. No pseudarthrosis 10
4. No nerve injury 10
5. No tooth damage 10
6. No persistent pain, discomfort or infection 10
7. No dentoalveolar compensations 10
8. Occlusal balance and adequate function 10
9. Patient satisfaction with esthetic and psychological outcome 10
10. Skeletal stability 1 year after the end of the contention period 10
100
 Minimum level for success is a success rate of 90% after 1 year
Int. J. Oral Maxillofac. Surg. 2001; 30: 89–103 Craniofacial distraction osteogenesis:
a review of the literature. Part 1: clinical studies G. Swennen & co workers

87. Slide 87
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