Cẩm Nang Điều Trị Chỉnh Hình Hàm Mặt (Tiếp Cận Đa Chuyên Khoa)

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Handbook of Orthognathic Treatment
5.9  Preparing the casts for
articulation
The dental impressions should be cast in class IV
dental stone. This provides a very hard and accurate
cast and withstands the stresses of re-positioning
when assessing a new final occlusion. The manufac­
turer’s instructions should be followed closely when
mixing these types of stone as failure to do so will
lead to a weak and inaccurate cast.
As an alternative to gypsum based products there
are several dual component model resins which
provide an accurate and very hard model of the den­
tition which will also resist the previously mentioned
stresses and would be the best choice if multiple
occlusal repositioning wafers are to be constructed.
This material will resist breakage of the teeth which
commonly occurs during occlusal repositioning
wafer construction.
The master impressions should be duplicated and
trimmed to provide a set of study models. A good set
of study models will provide a record of the relation­
ship of upper and lower dental centre lines, degree of
over jet, degree of overbite and will allow the assess­
ment of the patient’s occlusion. Additionally, in some
cases a rough measurement of potential changes to
the facial height can be assessed.
The master casts can be trimmed in several ways.
It is common for a conventional semi circular
trimmed cast to be used for model surgery. This shape
of cast particularly in the case of the maxilla will
prevent detrimental rotations about the centre of the
palate being easily detected. Such rotations could
lead to surgically impossible positions being pre­
dicted due to interference with the pterygoid plates
as a result of unseen and unwanted posterior move­
ments being incorporated in the model surgery. The
Figure 5.15  New orthognathic face bow.
Figure 5.16  New orthognathic articulator.
has the bite registration fork attached (Figure 5.15).
The face bow registration is taken in the same way as
previously described. The main operational differ­
ence of this face bow is it is not adjusted to fit the
articulator as the previous adapted Dentatus unit is,
rather the articulator is adjusted to the face bow reg­
istration. The benefits of this are the registration of
differing heights of condyle, such as may be found
in cases of hemifacial microsomia, more accurate
setting of the condylar width and an improved accu­
racy in the representation of any existing occlusal
canting. All of these features are not available using
a semi-adjustable dental articulator, and all are
helpful for orthognathic model surgery planning.
5.8.2  Articulator
The face bow is attached to the condyles on the articu­
lator. The condylar components on the articulator are
adjustable for both width and height. These allow A/P
and height adjustment independently of each other
and are capable of the accurate representation of
asymmetric condylar relationships. There is sufficient
space between the upper cross member and the base
of the articulator to ensure ease of mounting of the
casts. This is a shortcoming of most semi-adjustable
articulators. The mandible has been designed to be
the hinged component as this replicates the human
anatomy more accurately (Figure 5.16). Using the face
bow and articulator allows improved accuracy in
recording the patient’s relevant anatomical structures
and landmarks required for orthognathic model
surgery. This combination of improved face bow and
articulator have proved useful tools in the diagnosis
and treatment of patients with both symmetric and
asymmetric deformities. A full report of the clinical
application and significance of this methodology is
listed in Further Reading at the end of this chapter.

Orthognathic technical procedures
89
5.9.2  Marking out the casts
With the casts mounted on the articulator the model
surgery can commence. The system described has
evolved over a long period of time and has been
effectively used by the author. Many units will have
their own preferences and methods of orthognathic
model surgery, however, when studied the various
systems are all similar. One of the advantages of the
described system is the ability to return the casts to
the start position without the need to repeat the face
bow and cast mounting procedure should modifica­
tions to the final treatment plan be made.
The first stage when marking the casts for model
surgery is to mark datum lines on the upper and
lower casts in order to measure the movements of the
casts as directed by the prescription on the planning
sheet. The casts may also be marked using a system
which will allow the casts to be returned to the start
position. A colour key system is applied to the mark­
ings. The start position of the model surgery is
denoted by red lines; the intermediate position is
denoted by green lines. This system is in use within
our laboratory, however, can be adapted to suit indi­
vidual operators. The use and evaluation of markings
and measurements will be explained as the procedure
is described.
Orthognathic model surgery will require the dental
casts and articulating plaster to have a series of
scribed vertical and horizontal lines. These lines will
be used to measure the prescribed movements on the
repositioned articulated casts. At this stage it is worth
mentioning that the master cast is not trimmed
(unless a segmental procedure is prescribed) this
allows accurate repositioning of the separated casts
to the original articulated position, which allows for
a change of plan without the need for a further face
use of master casts with square bases will allow more
accurate visual assessment of the movements pre­
dicted by the model surgery, clearly showing any
movements as deviations from the square bases
(Figure 5.17).
5.9.1  Articulating the casts
Depending on the operator’s choice of system the
first step in the model mounting procedure is to
attach the face bow or bite jig to the articulator
according to the manufacturer’s instructions. The
maxillary cast is placed in the face bow’s bite registra­
tion fork and is checked for stability. It is not uncom­
mon for the master cast to be unstable in the bite
registration due to interference between the ortho­
dontic brackets (if present) and the bite registration.
The simple solution is to trim areas of contact
between the bite and the cast until stability is
obtained, carefully ensuring that there is no move­
ment of the face bow components or damage to the
teeth or occlusion.
The maxillary cast is trimmed until the base is
parallel to the horizontal. This can easily be done by
marking a line on the base of the cast using an engi­
neering surface gauge. With a line scribed on the base
of the cast it can be trimmed using a plaster model
trimmer (Figure 5.18).
The maxillary cast is attached to the upper arm of
the articulator using anti expansion plaster. On com­
pletion of this procedure the face bow is detached
from the articulator. The mandibular cast is now
occluded with the mounted maxillary cast using the
wax jaw registration and is attached to the lower
arm of the articulator using anti expansion plaster.
The casts are now ready for model surgery to
commence.
Figure 5.17  Arrows showing the movement of the
repositioned cast.
Figure 5.18  Engineering surface gauge marking out
maxillary cast.

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Handbook of Orthognathic Treatment
5.9.4  Marking and measuring the casts for
antero-posterior movements
A line is scribed on the buccal cusp of the upper and
lower first molars (B).
Using a set of Vernier callipers a second meas­
urement is taken from the incisal edge from each of
the upper and lower centrals to the incisal pin on the
articulator (A) (Figure 5.20). This measurement is
scribed on the back of the cast for future reference.
Using these measurements advancement of the
maxilla and advancement and set back of the man­
dible can be evaluated.
5.9.5  Repositioning the casts
There are several considerations when marking and
measuring the casts.
1. Measurements at tooth level will be more accurate
than those taken from the bases of the casts. The
teeth are the only anatomically accurate structures
on the casts. The chosen model surgery method
should always allow the operator to return to the
starting position should the surgery plan change.
2. Avoid measuring in an arc (Figure 5.22). This situ­
ation can occur when the maxillary cast has been
advanced a significant amount and the protruding
cast tempts the operator to arc dividers or callipers
to make a measurement. This will give a false
measurement of movement (Figure 5.21).
3. Measure the advancement from a fixed point and
at tooth level. Vernier callipers are ideal for this
procedure. Maxillary and mandibular advance­
ment should be measured by taking a point
between the upper and lower central incisors and
the articulator pin prior to the commencement of
the model surgery. This can be compared to the
bow recording or new master casts as previously men­
tioned. All lines and markings will be scribed into the
plaster as this assures longevity unlike ink which will
fade over time (Figure 5.19). The expected storage
time of the final plan casts is a minimum of five years.
This is the time from initial surgery to discharge from
hospital care. The markings on the casts and mount­
ing plaster must be legible at the final appointment
to allow for a clear record of the prescribed surgical
movements and to allow the assessment of the surgi­
cal outcome.
5.9.3  Marking and measuring the casts for
vertical movements
The first line scribed on the maxillary cast (1) is a
horizontal line at a distance of 5mm from the base.
A second line is scribed on the mounting plaster (2)
at a distance of 10mm this allows a total of 15mm
between lines (1+2). Trimming to reposition casts
should be limited to the mounting plaster. The dis­
tance of 10mm has been found sufficient to accom­
modate most prescribed movements, however, there
is no requirement to adhere to this measurement and
the individual operator may prefer different dimen­
sions of mounting plaster. It is important to scribe
the distance between the horizontal lines on the
mounting plaster if this differs from job to job this
measurement then allows for calculation of the origi­
nal movements.
Each tooth should be measured from the tip of a
chosen cusp or incisal edge to the uppermost hori­
zontal line on the mounting plaster (3). This meas­
urement is scribed on the mounting plaster. This will
allow for a double check of the prescribed vertical
movement.
Figure 5.20  Markings for A/P movements.
Figure 5.19  Mounted casts showing datum lines for
model surgery.

Orthognathic technical procedures
91
made. This wafer is used intra-operatively to
re-position the surgically separated jaw by relating
the relationship of the upper and lower teeth to each
other. In the case of single jaw surgery one wafer will
be required to record the final occlusal position.
Bi-maxillary osteotomies will require two wafers, the
first to re-position the maxilla and the second to
relate the mandible to the surgically corrected maxilla
which will be the final occlusion. The usual sequence
of bi-maxillary surgery would be to re-position the
maxilla to the prescribed position and relate the man­
dible to the maxilla. There are some exceptional situ­
ations in bi-maxillary surgery where the mandibular
surgery would be carried out first. Severe mandibular
asymmetry would be one such situation. In this case
the mandible would be corrected and the maxilla
related to the new mandibular position. There are
further exceptional circumstances where sub-apical
segmental osteotomies might be required. In such
cases there may be more than the two occlusal wafers.
As a rule each stage of surgery will require one wafer,
so an example might be, first wafer maxillary surgery,
second wafer mandibular sub-apical osteotomy from
canine to canine, third and final wafer mandibular
advancement. It is worth considering a system of
colour coding the intra-operative wafers to avoid
confusion in theatre during surgery. Our chosen
system always colour codes the intermediate wafer in
ivory and the final occlusal wafer clear.
There are several materials and designs for wafer
construction and they are once again operator prefer­
ence. The wafer can be made using self cure acrylic,
heat cure acrylic, light curing materials and silicone.
They can have attachments for securing the wafer
during use such as power chain, holes can be drilled
for wires or cleats can be added. Figure 5.23 shows
Figure 5.21  Parallel measurement.
Figure 5.22  Measurement in an arc.
Figure 5.23  Occlusal re-positioning wafer.
same measurement points post-model surgery and
simple subtraction will provide the amount of
advancement at tooth level.
4. Geometrical movements may occur showing
anomalies in the markings. Two examples of this
would be in the case of a differential impaction,
that is, Posterior maxillary impaction of 6mm and
anterior maxillary impaction of 2mm. The mark­
ings on the sides of the models will show gaps
between the lines and this can be mistaken for
advancement which is not the case. Secondly, a
medio lateral correction of an occlusal cant will
show a similar separation of the datum lines. This
is not rotation of the centrelines, but simply a
differential movement of the cast to correct the
canting.
5.9.6  Occlusal re-positioning wafer
Once the model surgery has been completed to pre­
scription an occlusal re-positioning wafer will be

92
Handbook of Orthognathic Treatment
of selected portions of the skull and jawbones will
improve the accuracy of surgical planning and would
also negate the difficulties associated with the use of
the face bow. This new method has the potential to
be more applicable to patients with complex cranio­
facial problems and pronounced asymmetry. To
obtain an accurate replica of the patient’s skull and
dentition would be beneficial in explaining the pro­
cedure and would be of educational value. It should
be pointed out that three dimensional skull models
are expensive compared to techniques currently
available and rely on experienced personnel to
operate the necessary equipment for their produc­
tion. The cost of the technology is, however, becom­
ing more affordable, which makes it more attractive
for larger specialist units. Smaller units could liaise
with larger units to make full use of this technology
and make it more cost effective.
With the aid of a denture reline jig (Figure 5.24)
the sectioned three-dimensional maxillary dental
alveolar process of the physical skull model was
placed into the lower section of the jig. Before the
top section of the jig was closed a dental impression
material was added to allow an impression to be
taken of the maxillary dentition of the skull. Once
the material was set, the jig was opened and the
three-dimensional dentition of the physical skull was
removed. A polyvinyl splint which had been fabri­
cated on the plaster model of the patient was placed
into the indentations of the teeth within the impres­
sion on the top section of the jig. Plaster was poured
into the fitting surface of the splint to reproduce the
accurate dentition. Cold cure acrylic resin was placed
the author’s preferred design of final occlusal wafer,
this is constructed using self cure acrylic and incor­
porates three cleats which are used to attach the
wafer to the patient’s orthodontic attachments with
power chain. This design allows the patient to remove
the wafer for cleaning which improves oral hygiene.
5.10  Recent advances in model
surgery
With the introduction of CT and MRI volumetric
scanning it has become possible not only to view
digital images of patient data on the computer screen,
but also to create physical skull models from this data
through improved developments in rapid prototyp­
ing. One of the limitations of this technology is the
inaccurate reproduction of the teeth where streak
artefacts are created due to metallic dental restora­
tions and orthodontic brackets being present. In
addition to this the teeth themselves do not replicate
accurately due to their complex structure and result­
ant beam hardening. A technique has been created
for exchanging the inaccurate dentition of a three
dimensional physical skull model with plaster dental
cast taken from a direct impression of the patient.
At present most surgeons use lateral cephalographs
and dental casts for planning orthognathic surgery.
This provides little information about any associated
deformities of the jaw bones, including condylar
abnormalities, mediolateral facial asymmetries, dys­
mophology of the chin, or abnormalities of the infe­
rior border and ramus of the mandible. The inclusion
Figure 5.24  Maxilla and impressions
in jig.

Orthognathic technical procedures
93
input from many colleagues over a number of years,
all of whom contributed in some way to the tech­
niques presented. It is hoped this brief insight might
enthuse the reader to seek further information on
this highly rewarding aspect of maxillofacial surgery.
We must acknowledge the input and assistance of
three of our valued colleagues for their assistance in
the preparation of this chapter: Mr Michael O’Neil,
Principal Maxillofacial Prosthetist, Regional Maxil­
lofacial Surgery Unit, Southern General Hospital,
Glasgow, for his expertise in the use of three dimen­
sional software and associated models, Ms Barbara
Thomson, Maxillofacial Prosthetist, Regional Maxil­
lofacial Surgery Unit, Southern General Hospital,
Glasgow, for numerous face bow recordings, and
James Eyland, our medical photographer, for his
patience in preparing the images used to illustrate
this work.
5.11  Suggested further reading
Barbenel, J.C., Paul, P.E., Khambay, B.S., Walker, F.S., Moos,
K.F. and Ayoub, A.F. (2010) Errors in orthognathic surgery
planning: the effect of inaccurate study model orienta­
tion. International Journal of Oral and Maxillofacial Surgery,
39, 1103–1108.
Paul, P.E., Barbenel, J.C., Walker, F.S., Khambay, B.S., Moos,
K.F. and Ayoub, A.F. (2012) Evaluation of an improved
orthognathic articulator system: 1. Accuracy of cast orien­
tation. International Journal of Oral and Maxillofacial
Surgery, 41(2), 150–154.
Paul, P.E., Barbenel, J.C., Walker, F.S., Khambay, B.S., Moos,
K.F. and Ayoub, A.F. (2012) Evaluation of an improved
orthognathic articulator system: 2. Accuracy of occlusal
wafers. International Journal of Oral and Maxillofacial
Surgery, 41(2), 155–159.
O’Neil, M., Khambay, B., Moos, K.F., Barbenel, J., Walker, F.
and Ayoub, A. (2012) Validation of a new method for
building a three-dimensional physical model of the skull
and dentition. British Journal of Oral and Maxillofacial
Surgery, 50(1), 49–54.
Walker, F., Ayoub, A., Moos, K.F. and Barbenel, J. (2008) Face
bow and articulator for planning orthognathic surgery: 1
face bow. British Journal of Oral and Maxillofacial Surgery,
46, 567–572.
Walker, F., Ayoub, A., Moos, K.F. and Barbenel, J. (2008) Face
bow and articulator for planning orthognathic surgery: 2
articulator. British Journal of Oral and Maxillofacial Surgery,
46, 573–578.
between the plaster base and the maxilla to hold
them together. The jig was reassembled and bolted
down to ensure that the dentition was orientated in
an accurate position and to maintain the vertical
dimension. The jig was opened and the splint
removed, leaving the accurate plaster dentition
attached to the dental alveolar process of the three-
dimensional printed skull model. The dental alveolar
process of the skull bearing the plaster teeth was
removed from the transfer jig and returned to the
three-dimensional physical skull using locating plates
and screws (Figure 5.25). This technique allows the
skull with the mandible to have the surgical proce­
dures carried out and the bones re-positioned to
simulate the proposed surgery with an anatomical
accuracy not available using conventional dental
articulators and face bows. This method of model
surgery eliminates many of the errors inherent in the
presently used systems because of the improved ana­
tomical accuracy and represents a significant step
forward in model surgery techniques.
The model surgery techniques presented in this
short chapter do not represent a definitive guide to
this highly complex procedure. More detailed expla­
nation of many of the techniques described is avail­
able in the papers listed under further reading. The
overview presented has been formulated with the
Figure 5.25  Patients 3D model with dentition replaced.

Prediction planning
6
94
Intended learning outcomes
By the end of this chapter the reader should:
• Be aware of the current methods of prediction
planning.
• Understand and be able to apply the two-
dimensional planning process in routine clinical
practice.
• Be aware of the advantages and disadvantages of
two-dimensional planning.
• Understand the steps in producing a three-
dimensional ‘virtual patient’.
• Have knowledge of navigation surgery and its
potential future role in orthognathic surgery.
Chapter overview
Intended learning outcomes, 94
6.1 Introduction, 94
6.2 Prediction planning for orthognathic
surgery, 95
6.3 Methods of prediction planning, 95
6.3.1 Model planning, 95
6.3.2 Soft tissue profile prediction planning, 95
6.3.3 Computerised prediction, 96
6.3.4 Factors affecting the accuracy of prediction
planning, 97
6.3.5 Hard tissue and soft tissue ratios, 97
6.3.6 Summary, 99
6.4 The two dimensional planning
process, 100
6.4.1 Acquisition of lateral cephalogram, 100
6.4.2 Acquisition of the lateral profile
photograph, 100
6.4.3 Superimposition of lateral cephalogram and
profile photograph (Matching), 101
6.4.4 Planning, 102
6.4.5 Simulation, 104
6.4.6 Surgical planning sheet, 104
6.5 Three dimensional prediction software,
104
6.6 The three dimensional planning
process – acquisition of different imaging
modalities, 106
6.6.1 CBCT, 106
6.6.2 Three-dimensional stereophotogrammetry, 106
6.6.3 Planning, 108
6.7 Navigation surgery, 108
6.7.1 Summary, 109
6.8 References, 110
6.1  Introduction
The aim of this chapter is to introduce the different
methods of orthognathic prediction planning, high­
lighting current practice to state of the art three-
dimensional planning. The strength and short
comings of each method of planning will be dis­
cussed. This chapter will describe in detail the
methods of planning that are currently used by the
Team; both two dimensional prediction software
(CASSOS – Computer Assisted Surgical Simulation for
Orthognathic Planning) and three dimensional pre­
diction software (Maxilim)*. The majority of compu­
ter planning programs apply a similar methodology
Handbook of Orthognathic Treatment: A team approach, First Edition. Ashraf Ayoub, Balvinder Khambay, Philip Benington,
Lyndia Green, Khursheed Moos, and Fraser Walker.
© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.
* The Authors have no financial interest in these companies.

Prediction planning
95
6.3  Methods of prediction planning
6.3.1  Model planning
Model surgery prediction is based on surgical proce­
dures performed on study models, which are sec­
tioned to achieve normal occlusal relationships. This
gives an indication of the surgical skeletal move­
ments required to correct the malocclusion but pro­
vides no information about the soft tissue change. It
was soon realised that this approach may be detri­
mental to the facial profile and that an approximately
ideal occlusion may not be accompanied with the
best facial aesthetic results. However, model planning
is still essential to predict the final dental occlusion
and to construct the intermediate and final orthog­
nathic wafers to guide the surgical procedure. This is
dealt with in greater detail in Chapter 5 Orthognathic
technical procedures.
6.3.2  Soft tissue profile prediction
planning
Combined cephalometric tracings and
photographs
Henderson (1974) introduced a technique that com­
bined cephalometric radiographic tracings with pho­
tographs. A lateral transparent positive 1:1 photograph
was superimposed on the patient’s lateral cephalom­
etric radiograph. A tracing was made of the relevant
hard tissue structures from the cephalometric radio­
graph onto the photograph. The photograph was
then sectioned along the planned osteotomy sites
and moved according to the desired surgical move­
ments. The soft tissues were then moved according to
which will help the reader transfer knowledge and
techniques learned in this chapter into their own
clinical practice.
6.2  Prediction planning for
orthognathic surgery
The successful outcome of orthognathic surgery
requires precise surgical technique and comprehen­
sive orthodontic treatment. More importantly the
final outcome must provide an aesthetic improve­
ment that meets the patient’s expectations and an
occlusion that is functional. Involving the patient in
the decision making process is an important part of
pre-surgical planning and as such providing patients
with a ‘realistic’ simulation of the post-surgical result
is becoming a necessity. The current method of plan­
ning uses profile views of the patient in the form of
lateral cephalograms and profile photographs. The
challenge of planning is to position the teeth in an
ideal class I incisor relationship whilst at the same
time producing the correct final soft tissue appear­
ance bearing in mind that the skeletal hard tissue lays
in between (Figure 6.1).
Orthognathic surgical planning should achieve the
following objectives:
1. Determine the final post-surgical dental occlusion
– termed ‘model planning’.
2. Illustrate to the patient and Team the potential
post-surgical soft tissue profile facial appearance
– termed ‘soft tissue profile prediction planning’.
3. Determine the magnitude of skeletal hard tissue
movement necessary at the time of surgery.
Figure 6.1  Shows the interaction
between soft tissue, hard tissue and
teeth during the planning and
execution phases of orthognathic
surgery. Source: Ayoub, A.F. and
Khambay, B. (2012) A paradigm shift
in the diagnosis and management of
dentofacial deformities. The Saudi
Dental Journal, 24, 121–125.
Reproduced with permission of
Elsevier.
Decide on final
soft tissue appearance
How much hard tissue movement needed
to produce the soft tissue change?
PLANNING
EXECUTION
Teeth are attached to hard tissue.
Need to make sure incisors class l
Wafer production
Cephalometric
planning
Model
surgery

96
Handbook of Orthognathic Treatment
of profile prediction. Following the evolution and
development of computer hardware and software,
prediction imaging packages are able to incorporate
lateral profile photographs of the patient, which
could then be morphed to produce photo realistic
predictions.
All of the modern commercially available packages
are in essence computerisations of the manual plan­
ning technique. Firstly, specific landmarks are digi­
tised on both the lateral cephalometric radiograph
and the profile photograph; the number of land­
marks vary for each program. The prediction software
then automatically superimposes the radiograph and
photograph. Obviously the soft tissue on both the
cephalogram and the profile photograph needs to be
identical for the best superimposition. The method
of superimposition is often not known to the opera­
tor and the factors which may effect the accuracy are
therefore unknown. The orthodontist or surgeon is
then able to analyse dental, skeletal and soft tissue
variables against standardised sets of linear and
angular measurements and plan the surgery on-screen.
The software is programmed using mathematical
algorithms to allow the simulation of hard and soft
tissue movements. The final profile prediction is a
‘morphed and smoothed’ photo realistic prediction
of the proposed surgical outcome. Some packages
allow the clinician to “tidy-up” the lips if they appear
incorrect; this however introduces a subjective
element to the prediction which may introduce even
larger inaccuracies.
Advantages of computerised prediction
1. Computerised planning has greatly simplified the
prediction process and reduced operator time. For
most packages digitisation of the landmarks on
the radiograph and profile photograph is time
consuming but the real advantage comes from
the known ratios of hard to soft tissue movements, as
in Figure 6.2.
These photocephalometric planning techniques
have proved useful in orthognathic planning and
have been used in many centres, and are still being
used in many units, to plan the outcomes of orthog­
nathic surgery. These techniques, however, have a
number of limitations:
1. The method of planning is complex and time-
consuming.
2. The ratios of hard tissue to soft tissue movement
have become increasingly complex and the
surgeon or orthodontist must be very experienced
to be able to predict the response of the soft tissues
to bony movements. A degree of artistic skill is
required when using such planning techniques.
3. The methods are not consistent and reproducible
and are open to human error.
4. Differential movement of the soft tissues can be
complex. It requires multiple cuts and small
numerous segments to reproduce the soft tissue
profile. This results in a number of step defects in
the profile outline which does not provide a real­
istic prediction of facial appearance to patients.
5. The final plans are easily distorted and with time
the adhesive degrades with parts of the plan
moving or even being lost. This makes audit and
research from these records difficult.
6. An experienced surgeon or orthodontist is able to
visualise the results of prediction planning, but
for the patient the sectioned photographs are dif­
ficult to interpret.
6.3.3  Computerised prediction
In an attempt to overcome the limitations of the
manual techniques, a number of computer-based
packages have been developed. The early computer
packages were able to generate simple line drawings
Figure 6.2  1:1 prediction planning.
Pre-operative profile (a).
Superimposed lateral cephalogram
radiograph showing predicted hard
and soft tissue movements following
a maxillary advancement (b).
a)
b)

Prediction planning
97
sign a waiver stating that the prediction is only an
approximation of the actual surgical outcome. The
Team has however determined the validity of
CASSOS scientifically (Jones et al., 2007).
4. The increased accuracy of prediction planning
must be matched by surgical accuracy.
5. The majority of computer programs cannot deal
with ‘incompetent lips’ and as a result the final
prediction around the lips is often poor. Some
manufacturers have added ‘tools’ which allow for
correction but this can undermine the process and
once again introduces subjectivity.
6.3.4  Factors affecting the accuracy of
prediction planning
The accuracy and reliability of prediction planning is
dependant on a number of factors. These include:
1. Cephalometry. Lateral cephalograms are subject to
errors of projection during capture as well as land­
mark identification and measurement errors.
2. Photography. Photographs are two-dimensional
representations of three-dimensional objects and
are therefore subject to the same errors as lateral
cephalometric radiographs.
3. Superimposition of radiographic and photo­
graphic images. Manual methods of superimposi­
tion have been shown to be inaccurate. The errors
are the result of three factors: differential magni­
fication and distortion of the cephalometric
radiograph and photograph, errors of landmark
identification on both the photograph and radio­
graph are combined during superimposition
increasing potential errors.
4. Soft tissue response to the underlying hard tissue
movements. The ratios of hard to soft tissue move­
ment currently used in prediction planning are
average responses. Ratios will only describe a rela­
tionship between two specific points and it is
unlikely that a series of ratios will be able to
predict the response of the entire soft tissue drape.
Unfortunately there is considerable individual
variation and this can lead to inaccurate predic­
tions of the outcome of orthognathic surgery.
6.3.5  Hard tissue and soft tissue ratios
Regardless of the method of prediction planning the
hard and soft tissues are broadly the same and based
on historical data, Figure 6.3. Orthognathic surgical
simulation programs are based on algorithms that
relate soft tissue response to the underlying skeletal
change. The soft tissues are stretched, or become thin­
ner as the maxilla is advanced in surgery and inter­
preting this interaction is important in predicting
being able to rapidly and accurately analyse and
predict surgical results. The operator can easily
explore a number of orthodontic and surgical
options.
2. The software may be programmed with a number
of complex non-linear mathematically derived
algorithms to predict the soft tissue response to
the surgical movements. The software can easily
be updated and the software algorithms adjusted,
based on any new data that becomes available.
3. The computer software package is able to morph
and smooth the image meaning less artistic skill
is required. Some packages do have the option
of using touch-up tools to enhance the final
prediction.
4. The use of computer packages has improved the
reproducibility of orthognathic surgical planning.
The process of planning is standardised from digi­
tising landmarks and superimposition through to
morphing and smoothing of the final prediction.
Orthodontists and surgeons are able to produce
similar predictions and in the same format.
5. Computerised predictions are easily stored and
retrievable at a later date. This method lends itself
to audit and research more so than the manual
prediction technique. It is relatively easy to back
up patient data and plans and electronically trans­
fer information between various hospital sites.
6. The greatest advantage of software prediction
packages is the ability to produce photorealistic
post-surgical predictions. This greatly improves
patient participation in the planning process and
communication between orthodontist, surgeon
and patient. This has a clear positive impact on
patient satisfaction following surgery.
7. As a result of the ability of computer packages
to calculate calibrated distances and angles it is
more accurate to calculate the desired surgical
movements.
Disadvantages of computerised prediction
1. Initial set up cost of the hardware and software.
2. As with any new technique there is a learning
process.
3. The patient may perceive the photo realistic
images to imply a guarantee of treatment result.
In reality the actual surgical outcome is usually
more aesthetically pleasing than the prediction.
To prevent patients believing that the prediction
will be a guarantee of the actual surgical outcome
some authors have advocated adding the phrase
‘Treatment Simulation Only’ to all predictions. It
has also been suggested that the patient should

98
Handbook of Orthognathic Treatment
naso-labial angle to surgical advancement of the
maxilla reveals a wide variation of results. Table 6.1
lists a number of studies and their findings, adapted
from McCollum et al., 2009.
The use of linear ratios for prediction planning has
its limitations. For example, with maxillary advance­
ment, initially there will be no change in soft tissues
due to the labial sulcus space between the upper lip
and incisors. As the maxilla is advanced, contact will
be made with the lip and the magnitude of soft tissue
movement will increase. Further advancement of the
maxilla results in stretching and resistance of the
upper lip. The lip becomes thinner and the ratio of
soft tissue change to the underlying bone movement
decreases.
the outcome. The relative changes are expressed as
mean ratios of soft tissue movements versus those of
the hard tissues, and the software packages are based
on these values. Therefore, though clinically useful,
computerised predictions of soft tissue profile changes
after orthognathic surgery are imprecise. This is
because the treatment simulation is only as accurate
as the data used. Historically, reporting of soft tissue
changes following orthognathic surgery concentrated
more on profile changes associated with mandibular
procedures in the early 1970s. Maxillary procedures
were reported, but to a lesser extent, only increasing
later in the decade as they became more popular. A
review of the literature concerning the soft tissue
reaction of the nose tip, nasal base, upper lip and the
Figure 6.3  Diagrams showing approximate hard to soft tissue ratio for (a) incisor movement (orthodontics), (b)
maxillary surgery, (c) mandibular surgery, and (d) genioplasty.
c)
d)
b)
a)

Prediction planning
99
Table 6.1  Soft tissue to hard tissue ratios for various soft tissue points (adapted from McCollum et al., 2009).
Soft tissue point
Author
Ratio
Comments
Nasal tip
Louis et al., 2001
0.16:1
Mansour et al., 1983
0.17:1
Teuscher and Sailer, 1982
0.22:1
Freihofer, 1977
0.25:1
Altug-Atac et al., 2008
0.25:1
Soncul and Bamber, 2004
0.30:1
Carlotti et al., 1986
0.34:1
Rosen, 1988; Chew, 2005
0.35:1
Proffit and White, 1991
The nose tip elevates slightly
Nasolabial angle
Louis et al., 2001
The nasolabial angle became more acute, decrease of 5°,
unrelated to the amount of maxillary advancement
Conley and Boyd, 2007
The nasolabial angle decreased by 3.9°
Subnasal
Proffit and White, 1991
0.20:1
Mansour et al., 1983
0.24:1
Lines and Steinhauser, 1974
0.39:1
Freihofer, 1977
0.50:1
Anterior nasal spine removed
0.67:1
Anterior nasal spine left intact
Rosen, 1988
0.51:1
Chew, 2005
0.60:1
Chinese adults
Carlotti et al., 1986
0.67:1
V-Y lip closure and an alar base cinch
Superior labial
sulcus
Carlotti et al., 1986
0.78:1
Lin and Kerr, 1988
0.81:1
A strong correlation with A point
Chew, 2005
0.73:1
Conley and Boyd, 2007
0.96:1
With additional surgical procedure
Labrale superius
Altag-Atac et al., 2008
0.40:1
Proffit and White, 1991
0.60:1
Teuscher and Sailer, 1982
0.63:1
Rosenberg et al., 2002
0.64:1
Without an alar base cinch and an intact anterior nasal
spine (ANS)
Chew, 2005
0.73:1
No additional surgery
Louis et al., 2001
0.80:1
V-Y closure only
Lin and Kerr, 1998
0.81:1
Found a moderate correlation to A point
Rosen, 1988
0.82:1
Hack et al., 1993
0.82:1
After 1 year
0.91:1
After 5years
Carlotti et al., 1986
0.90:1
Alar base cinch. Suture and V-Y lip closure
Conley and Boyd, 2007
0.96:1
Piriform fossa recontouring, ANS removed
Peled et al., 2004
0.89:1
Simple continuous suturing
0.90:1
V-Y lip closure technique
6.3.6  Summary
A shortcoming of two-dimensional prediction plan­
ning is that the prediction is only as accurate as the
ratios used for soft tissue movements in response to
hard tissue changes, which are based on historical,
varied and questionable evidence. Moreover, based
on profile prediction only anterior-posterior and ver­
tical changes can be determined. The technique does
not investigate, and therefore cannot report on, the
transverse dimension.

100
Handbook of Orthognathic Treatment
begin prediction planning, as in Figure 6.4. One solu­
tion is to construct a wax wafer, with the mandible
in the rest position, to provide a stable ‘stop’ for the
patient to bite against during lateral cephalogram
and profile imaging.
Procedure for wax wafer construction
1. Position patient in NHP.
2. Place mark on nose and chin.
3. Ask patient to say ‘Mississippi’ and ‘N’, lick lips
gently and put lips together.
4. Measure distance between marks using calipers.
5. Repeat stages 3 & 4 and record the average value.
6. Place softened wax (several sheets if necessary)
into hot water and construct a wax wafer.
7. Place wax wafer in between patient’s teeth and
ask them to gently close, simultaneously measur­
ing the distance between the marks. Once the
measured distance in stage 5 is reached stop,
remove wafer and chill in cold water.
8. Trim excess wax buccally with a sharp scalpel to
prevent any soft tissue distortion.
9. Re-insert wafer into patient’s mouth and
re-measure the distance between the dots ensur­
ing there is no soft tissue distortion.
10.  Keep this wax wafer safe since it will be
used again for photocephalometric planning,
three-dimensional stereophotogrammetry image,
CBCT and model surgery.
For the application of any computer software
package the cephalogram has to be in a digital format.
Conventional hard copy cephalograms are scanned
as black and white images with a back lit high quality
scanner at the desired resolution; size and saved in
the appropriate format, that is, normally JPEG, but
this is software dependant. This file is then imported
into the software prediction package (CASSOS).
6.4.2  Acquisition of the lateral profile
photograph
In order to produce the best possible profile predic­
tion, given the limitations of the method, each stage
must be executed with the minimum amount of
error. The process relies on superimposing the hard
and soft tissues of the cephalogram on the soft tissue
profile of the lateral profile photograph. Therefore
the morphology of the two soft tissue profiles should
be identical. The gold standard method, therefore, is
to capture the cephalogram and profile photograph
simultaneously, whilst the patient is still in the
cephalostat. This may not be logistically practical, in
which case the photograph needs to be taken after
the cephalogram. This should be carried out as soon
6.4  The two-dimensional planning
process
The planning process requires a method of producing
a two-dimensional ‘virtual’ patient by simultane­
ously capturing the profile facial hard and soft tissues.
The lateral cephalogram achieves this but without
the colour soft tissue texture. The addition of a profile
photograph overcomes this deficiency.
6.4.1  Acquisition of lateral cephalogram
The procedure of lateral cephalogram acquisition
should be a relatively simple procedure for orthodon­
tic patients but poses some difficulties for the orthog­
nathic patient. The two main controversies are head
position and occlusion.
Head position
At present two methods are used to position the
patient’s head during exposure; Frankfort Plane (FP)
parallel to the floor or in natural head position (NHP).
For routine orthodontic patients the use of FP is often
satisfactory, but for patients with facial dysmorphol­
ogy NHP may be more representative taking into
account aberrant facial and cranial base positions.
Planning should therefore be based on NHP as this is
the position the patient’s head would adopt during
‘normal’ function. As indicated in Chapter 2 the posi­
tion of the patient’s head can have a marked effect
on the perceived skeletal jaw relationship of the
patient.
Occlusion
The routine for orthodontic patients is to take the
lateral cephalogram with the teeth in occlusion and
the soft tissues at rest and recorded lips at repose.
Again, for the majority of orthognathic patients, this
may be satisfactory but may not be appropriate for
others. Patients who are skeletal class II have a ten­
dency to posture their mandibles forward (perhaps
subconsciously) masking the severity of their maloc­
clusion. To overcome this, patients must be imaged
in a retruded contact position. High angle class II and
class III patients with incompetent lips, often approx­
imate their lips together during imaging to obtain an
oral seal. This will distort the labial soft tissues and
produce an erroneous profile prediction. The last
group of patients are those with vertical maxillary
deficiency and they tend to ‘over close’ due to the
excessive freeway space. This is a source of error, as
the mandible ‘over rotates’ into occlusion, the upper
lip is distorted by the lower lip; again producing an
incorrect initial soft tissue pattern from which to

Prediction planning
101
zoom is used and not the digital zoom which may
distort the final image.
6.4.3  Superimposition of lateral
cephalogram and profile photograph
(Matching)
This process involves identifying corresponding land­
marks on the lateral cephalogram and the profile
photograph. Some software packages use only the
anterior soft tissue landmarks for this process whilst
others add a posterior landmark forming a triangle.
This triangulation process in our opinion is a more
accurate technique of superimposition. The method
of matching is derived by the programmers and
as possible using a digital camera, maintaining the
same soft tissue position as for the cephalogram using
the same wax wafer if necessary.
In order to reduce perspective error it is important
to make sure that the photograph is taken perpen­
dicular to the patient’s sagittal plane with the camera
focused on the external auditory meatus. To help
enhance the soft tissue profile we have found it useful
to place an illuminated source behind the patient.
This is either secured to the wall or held by a nurse
during photography. When taking the photograph it
is important to make sure that the image fills the full
view using the zoom function on the camera. If
zooming in is required it is vital that only the optical
Figure 6.4  Example of a patient who
requires a wax wafer to control the
vertical dimension and prevent soft
tissue distortion.
Patient in occlusion – note distorted upper lip
Patient at rest with wax wafer in situ

102
Handbook of Orthognathic Treatment
face. The types of surgical movements that can be
carried out are again determined by each computer
package. The basic principles should be similar across
all prediction software packages in that the maxilla
and/or mandible are moved in one piece or segmen­
tally whilst the ‘linked’ soft tissue moves accordingly.
The amount of hard and soft tissue movement will
therefore the user generally has no ability to change
the technique but only to follow it according to the
‘matching wizard’ (Figure 6.5).
6.4.4  Planning
This is carried out on the matched images which
display both the hard and soft tissue profiles of the
Figure 6.5  Stages of computer
prediction from hard tissue
acquisition, soft tissue acquisition to
merging of ‘matched’ ready to plan
surgery.
Lateral cephalogram
Traced lateral cephalogram
Landmarked lateral portrait
photograph
Matched lateral portrait photograph &
cephalogram ready for surgical planning
Lateral portrait photograph

Prediction planning
103
Remember that the required surgical movements
produced must produce a class I incisor relation­
ship. It is essential to have the articulated model
surgery prediction plan available to allow verifica­
tion of the magnitudes of skeletal movement and the
final occlusion. The surgical movements obtained
during model surgery must be similar, within 1mm,
to the computerised prediction plan, whilst simulta­
neously producing the desired profile soft tissue
result.
be dependant upon the ratios or algorithms used by
the software programmers. Some software packages
allow these values to be changed but the question is,
what should they be changed to?
When planning for orthognathic surgery, treat­
ment starts with the position of the upper incisors
and maxilla, once this is corrected the mandible
is then moved into the desired position and the
chin position assessed, if necessary a genioplasty is
considered. These stages are shown in Figure 6.6.
Figure 6.6  Surgical planning
stages and simulations generated
using CASSOS.
Stages in planning
Stages 1
6 mm maxillary
advancement
Maxilla
Maxilla & mandible
Maxilla, mandible & chin
6 mm maxillary
advancement & 5 mm
mandibular set back
6 mm maxillary
advancement, 5 mm
mandibular & 5 mm set-back
genioplasty
Stages 2
Surgical simulations
Stages 3

104
Handbook of Orthognathic Treatment
Figure 6.7  Surgical simulations
generated using CASSOS.
(a) transparent superpositions
(b) before and prediction
complete profiles side by side.
a)
b)
6.4.5  Simulation
Each specific jaw effect on the soft tissue is simulated
by the computer. In CASSOS this can be displayed as
a complete profile before and prediction image or a
transparent superimposition of complete profiles, as
in Figure 6.7. Again the final simulation image is
dependant on the software used for prediction
planning.
6.4.6  Surgical planning sheet
The final agreed surgical plan can then be printed out
showing the direction and amount of each jaw move­
ment that has been decided upon, as in Figure 6.8.
To this any other adjunctive procedures can be added,
that is, simultaneous bone graft, extraction of teeth
and so on. This is then taken to theatre and used
peri-operatively so that no confusion or omission
occurs.
6.5  Three-dimensional prediction
software
Interest in three-dimensional planning with soft
tissue prediction in maxillofacial surgery started over
25 years ago. Many research groups have since con­
tinued working on the simulation of soft tissue defor­
mation for maxillofacial surgery. There has been
overlap of two and three-dimensional prediction
planning as progressive evolution occurred in image
acquisition modalities, surgical techniques, patient
expectations and technological innovations in both
computer hardware and software.
The ideal three-dimensional surgical planning
computer software system should integrate all essen­
tial requirements forming a pipeline for the entirety
of the patient’s journey including initial diagnosis,
high quality digital three-dimensional data records,
virtual surgical planning, wafer construction, accu­
rate prediction and subsequent reviews. At present
such a comprehensive surgical planning system does
not exist. However the combination of the latest
technologies in this field of work is moving closer to
the envisioned goal.
Virtual surgery is performed on a virtual patient
which has been produced by the ‘fusion’ of three-
dimensional soft, hard and dental tissue. The stages
are as follows:
1. Conebeam CT acquisition of the patient. This pro­
duces simultaneously volumetric hard and soft
tissue data.
2. Colour three-dimensional surface soft tissue
capture. This is acquired using either stereophoto­
grammetry or laser scanning.
3. Superimposition of a colour soft tissue surface
image over the soft tissue CBCT volumetric data.
This is based on corresponding anatomical land­
marks followed by a ‘refined’ alignment.
4. Three-dimensional dental model production. This
is acquired using either laser scanning or CBCT
scanning of plaster models or impressions to
produce three-dimensional virtual study models.
5. Alignment of virtual dental models into the hard
tissue CBCT scan and replacement of the distorted
dentition. The dentition is often distorted by
the CBCT scan which produces ‘streak artefacts’,
mainly due to metal fixed appliances or metallic
restorations.
6. Final image fusion of the three component images
into a single ‘virtual patient’.
These techniques include the use of computer
tomography, three-dimensional reconstructions of
models colour texture mapping, and real-time soft
tissue modelling. These fused images are then used by
the surgeons enabling them to undertake virtual oste­
otomies on a three-dimensional computer generated
skull model with a soft tissue surgical prediction.
The latest versions of software are now in their
infancy in predicting in three-dimensional soft tissue

Prediction planning
105
model, map texture information of two-dimensional
or three-dimensional photographs to the three-
dimensional CT skin surface, provide tools to perform
a three-dimensional cephalometric analysis, simulate
osteotomies with three-dimensional movements of
bony segments and simulate accompanying soft
tissue changes.
Case reports and description of the surgical plan­
ning pipeline have been published, confirming that
three-dimensional soft tissue simulation still requires
improvement and the clinician should be careful
in communicating this information to the patient,
especially for patients with long faces and facial
asymmetries.
changes following orthognathic surgery, with some
being used in academic research institutions and
others being marketed commercially. Programs have
been developed specifically for orthognathic surgery,
which are being used for orthognathic surgery
planning.
The commercially available packages generally
attempt to create a three-dimensional environment
for assessing maxillofacial anatomy, simulating surgi­
cal moves and predicting a soft tissue response.
These are often modular or ‘wizard’ based with each
performing various functions: importing DICOM
(Digital Imaging and Communications in Medicine)
CT image files to create a three-dimensional CT
Figure 6.8  Final surgical planning sheets generated using CASSOS.
PLANNING REPORT
Osteotomies
Key Cephalometric Analysis for Planning
Unit Pre-OP Simulate
Le Fort 1:
Ramus (SSO/VRO):
Genioplasty:
Translate: X = 6.0 mm, Y = 0.0 mm
1. SNA
2. SNB
3. Percentage Nose
4. U1-SN
5. L1-MD Plane
6. Occlusal Plane-FH
7. Facial Convexity
8. Zero Meridian to Pog′
9. Naso-labial Angle
10. U1 Exposure
11. Vertical Lip-Chin Ratio
12. Angle of PP-MD Plane
°
°
%
°
°
°
°
mm
°
mm
%
°
72.3
85.0
40.5
102.6
84.4
5.9
–1.0
20.8
110.3
5.0
43.5
30.9
78.7
83.2
42.7
102.6
82.8
4.2
10.8
15.1
117.5
6.7
45.8
28.1
Translate: X = 5.2 mm, Y = 2.9 mm
Translate: X = –5.0 mm, Y = 0.0 mm
Patient Name
Sex
Age/DOB
Race
Hospital No
FH
FH
Report Time/Date
Report Name
Date Source
CASSOS REPORT

106
Handbook of Orthognathic Treatment
Head posture is not generally controllable during
CBCT scanning. The patient needs to be placed in a
specific volume of space to allow imaging of the
desired region and the head needs to stabilised. Sta-
bilising is important to prevent any motion artefacts
during the CBCT scan, this is achieved normally by
the use of a chin cup. Since the chin cup distorts the
soft tissue around the chin region it will render it
unusable for planning, it should be avoided and a
high head strap used. The head strap should lie as
high up towards the hair line as possible in order to
prevent any forehead soft tissue distortion. Following
imaging the data is stored in a DICOM format which
will be later loaded into appropriate software.
6.6.2  Three dimensional
stereophotogrammetry
A disadvantage of CBCT imaging is that the soft
tissue/air boundary interface is a uniform non-skin
coloured texture following rendering. A colour three-
dimensional image of the patient can be captured
using three-dimensional stereophotogrammetry or
laser scanning (see Figure 6.10), which can then be
superimposed over the soft tissue of the CBCT scan.
As with any superimposition the two images need to
be as similar as possible; again this can be achieved
with simultaneous CBCT and three-dimensional ster-
eophotogrammetry capture. These obviously can be
taken at two different time points but the error of
superimposition may then occur. The superimposi-
tion technique involves choosing corresponding
landmarks on both the CBCT and three-dimensional
photographic images. These correspondences need to
be as far apart as possible and across all three planes
of space to allow accurate superimposition. The com-
puter then rigidly aligns these two images based only
6.6  The three-dimensional planning
process – acquisition of different
imaging modalities
6.6.1  CBCT
Conebeam CT simultaneously provides an image of
the hard and soft tissues of the maxillo-facial region
(see Figure 6.9). As previously discussed, it is impor-
tant that the occlusion and the position of the soft
tissue are appropriate prior to CBCT capture. As with
all images created using ionising radiation, the ideal
image should be obtained once on the first occasion
to reduce radiation exposure to the patient. It is rec-
ommended that a CBCT machine in which the
patient sits upright rather than lies supine, this
should prevent the unwanted effects of gravity on the
soft tissues.
Figure 6.9  Conebeam CT simultaneously provides an
image of the hard and soft tissues of the maxillo-facial
region. Source: Benington, P.C., Khambay, B.S. and
Ayoub, A.F. (2010) An overview of three-dimensional
imaging in dentistry. Dental Update, 37, 494–6, 499–500.
© George Warman Publications (UK) Ltd.
Image not available in this digital edition
Figure 6.10  The equipment used to
capture three dimensional
stereophotogrammetric photograph
of the patient. Source: Benington,
P.C., Khambay, B.S. and Ayoub, A.F.
(2010) An overview of three-
dimensional imaging in dentistry.
Dental Update, 37, 494–6, 499–500.
© George Warman Publications (UK)
Ltd.
Image not available in this digital edition

Prediction planning
107
ning these produce streak artefacts which distort the
teeth and the occlusion. Therefore techniques have
been developed which attempt to replace the denti-
tion, some of which include the ‘triple scan’ (Swennen
et al., 2009).
In this procedure the patient’s head is scanned at
0.4mm voxel size from the hair line above to below
menton. Alginate impressions are taken of the
patient’s teeth using a tray which simultaneously
records the upper and lower dentition. These impres-
sions are then scanned at a higher resolution of 0.2
on these corresponding points. To further refine
the superimposition specific corresponding areas are
chosen. These areas are made up of thousands of
points and these are used to refine the alignment.
Finally the two images are merged together to produce
a CBCT scan with a photo-realistic texture, as in
Figure 6.11.
The last structure which requires replacement is the
distorted dentition. Nearly all orthognathic patients
proceed with metallic fixed orthodontic appliances
or may have metallic restorations. During CT scan-
Figure 6.11  Stages for alignment and
fusion of CBCT scan soft tissue and
three dimensional
stereophotogrammetric photograph
of the patient. Source: Benington,
P.C., Khambay, B.S. and Ayoub, A.F.
(2010) An overview of three-
dimensional imaging in dentistry.
Dental Update, 37, 494–6, 499–500.
© George Warman Publications (UK)
Ltd.
Image not available in this digital edition

108
Handbook of Orthognathic Treatment
or motions to the user. It allows the use of ‘feel’ in a
virtual environment.
The lack of tactile feedback (haptics) makes several
aspects of orthognathic planning difficult, including
the final occlusion based on intercuspation between
the teeth. As clinicians we determine the final occlu­
sion by ‘best fit’ or maximum contact between the
teeth. This is not possible with any degree of accuracy
using software which lacks haptic planning. As a
result the final occlusion is difficult to find and the
wafer becomes difficult to construct. It is expected
that in the future this problem will be overcome. In
fact it has been suggested that ‘virtual’ wafers are
associated with poor fit because they are too accurate
and can not be fully seated!
Once a virtual wafer has been produced, the image
can then be exported as an STL file and used in a
rapid prototyping machine to produce the physical
wafer (Figure 6.14). This method of wafer production
obviously negates the use of a face bow and the asso­
ciated errors, but may introduce new types of inac­
curacies which require fuller assessment.
6.7  Navigation surgery
One possible solution to determine the final position
of the osteotomy segments during surgery and elimi­
nate the need for occlusal wafers may be using navi­
gational surgery.
The first bone segment navigation system for pre­
operative planning was the Surgical Segment Naviga­
tor (SSN), developed in 1997 at the University of
Regensburg, Germany, with the support of the Carl
Zeiss Company. This novel system did not require
any mechanical surgical guides (such as a headframe).
It was based on an infrared (IR) camera and IR trans­
mitters attached to the skull. At least three IR trans­
mitters were attached in the neurocranium area to
compensate the movements of the patient’s head.
There were also three or more IR transmitters attached
to the bones which required repositioning. The three-
dimensional position of each transmitter was identi­
fied by the IR camera, using the same principles as
voxel. Finally the tray is re-inserted into the patient’s
mouth and a 0.4mm voxel scan is taken of the upper
and lower dentition with the tray in situ, this is the
second occasion the patient receives a CBCT scan but
the area of interest is smaller. Using this method the
virtual dentition generated from the CBCT scan of
the impression can be used to replace the dentition
in the limited field of view patient scan using the tray
as the common structure in each image and ignoring
the soft tissue which will be distorted by the protrud­
ing tray handle. This composite image of skeletal
hard tissue and teeth can be used to replace the hard
tissue of the CBCT scan of the whole head leaving
the undistorted soft tissue intact.
Alternative methods of replacement of the denti­
tion have been developed utilising intra-oral registra­
tion techniques which prevent extra-oral soft tissue
distortion. These methods require only one CBCT
scan of the patient with the intra-oral registration
device in situ. An impression of the patients’ denti­
tion is than taken with the device in place and a
plaster model obtained. Following laser scanning or
CBCT scanning of the plaster model, the intra-oral
registration device which is common to both the
CBCT skull image and the plaster model image is
used to align and replace the distortion dentition on
the CBCT scan using CAD/CAM software, as in Figure
6.12. (Narin et al., 2013)
6.6.3  Planning
As stressed previously each program will have its own
method of planning with regard to procedure type
and hard and soft tissue ratios and so on (see Figure
6.13). One of the problems of virtual planning is that
the software is unable to deal with ‘collision detec­
tion’ satisfactorily. For example it is possible to carry
out a 15mm maxillary impaction on the computer
since the maxillary image can be readily displaced
through the skull structure. This cannot be avoided
unless the program has some form of ‘collision detec­
tion’ algorithm or ‘haptic’ technology which is used
in conjunction with the software. Haptic technology
is tactile feedback technology that takes advantage of
a user’s sense of touch by applying forces, vibrations,
Figure 6.12  Replacement of the
distorted dentition (streak artefacts)
on the CBCT model (a), with the
laser scanned or CBCT image of the
plaster teeth (b) to produce a
‘composite image’ with a workable
dentition (c).
a)
b)
c)

Prediction planning
109
6.7.1  Summary
The evolution of orthognathic surgical techniques
and the accompanying need to correct facial and
dental aesthetics have made orthognathic surgery
planning more complex. The necessity to move the
maxilla and mandible in three planes of space has
required surgical expertise and clinical judgement, to
ensure both the surgeon’s and the patient’s expecta-
tions are fulfilled. Therefore the long-term aim for
for satellite navigation. The workstation of the Surgi-
cal Segment Navigator (SSN) was constantly visualis-
ing the actual position of the bone fragments,
comparing them with the pre-planned position.
Thus, fragments could be very accurately re-positioned
into the target position. These surgical navigators
have been used routinely in neurosurgery, but are
now being used in some centres for orthognathic
surgery (Marmulla and Niederdellmann, 1998).
Figure 6.13  An asymmetric
case planned using Maxilim.
The hard tissue images on
the left show the virtual
osteotomies and on the
right the corresponding
predicted soft tissue change
is shown. Source: Benington,
P.C., Khambay, B.S. and
Ayoub, A.F. (2010) An
overview of three-
dimensional imaging in
dentistry. Dental Update, 37,
494–6, 499–500. © George
Warman Publications (UK)
Ltd.
Image not available in this digital edition

110
Handbook of Orthognathic Treatment
orthognathic surgery planning is to produce an
accurate method of three-dimensional assessment,
develop a planning and prediction tool that will also
allow digital construction of study models and occlu­
sal wafers, thus eliminating some of the inherent
inaccuracies in the current methods of planning.
6.8  References
Altug Atac A.T., Bolatoglu H. and Memikoglu U.T. (2008)
Facial soft tissue profile following bimaxillary orthog­
nathic surgery. The Angle Orthodontist, 78, 50–57.
Carlotti A.E., Jr, Aschaffenburg P.H. and Schendel S.A. (1986)
Facial changes associated with surgical advancement of
the lip and maxilla. Journal of Oral and Maxillofacial
Surgery, 44, 593–596.
Chew M.T. (2005) Soft and hard tissue changes after bimaxil­
lary surgery in classIII patients. Angle Orthodontist, 75,
959–963.
Conley R.S. and Boyd S.B. (2007) Facial soft tissue changes
following maxillomandibular advancement for treatment
of obstructive sleep apnea. Journal of Oral and Maxillofacial
Surgery, 65, 1332–1340.
Freihofer H.P.M. Jr. (1977) Changes in nasal profile after
maxillary advancement in cleft and non-cleft patients.
Journal of Maxillofacial Surgery, 5, 20–27.
Hack G.A., de Mol van Otterloo J.J., Nanda R. (1993) Long-
term stability and prediction of soft tissue changes after
Le Forte 1 surgery. American Journal of Orthodontics, 104,
544–555.
Henderson D. (1974) The assessment and management of
bony deformities of the middle and lower face. British
Journal of Plastic Surgery, 27, 287–296.
Jones R.M., Khambay B.S., McHugh S., Ayoub A.F. (2007) The
validity of a computer-assisted simulation system for
Figure 6.14  Virtual wafer ready for rapid prototyping in
STL format.
orthognathic surgery (CASSOS) for planning the surgical
correction of class III skeletal deformities: single-jaw
versus bimaxillary surgery. International Journal of Oral
Maxillofacial Surgery, 36, 900–908.
Lin S.S. and Kerr W.J. (1998) Soft tissue changes in classIII
patients treated by bimaxillary surgery. European Journal of
Orthodontics, 20, 25–33.
Lines P.A. and Steinhauser E.W. (1974) Soft tissue changes in
relationship to movemen t of hard structures in orthog­
nathic surgery: A preliminary report. Journal of Oral
Surgery, 32, 891.
Louis P.J., Austin R.B., Waite P.D. and Mathews C.S. (2001)
Soft tissue changes of the upper lip associated with maxil­
lary advancement in obstructive sleep apnea patients.
Journal of Oral and Maxillofacial Surgery, 59, 151–156.
Mansour S., Burstone C. and Legan H. (1983) An evaluation
of soft tissue changes resulting from Le Fort I maxillary
surgery. American Journal of Orthodontics, 84, 37–47.
Marmulla R., Niederdellmann H. (1998) Computer-assisted
bone segment navigation. Journal of Craniomaxillofacial
Surgery, 26, 347–359.
McCollum A., Dancaster J., Evans W., Becker P. (2009) Sagit­
tal soft-tissue changes related to the surgical correction of
maxillary-deficient class iii malocclusions. Seminars in
Orthodontics, 15, 172–184.
Nairn N.J., Ayoub A.F., Barbenel J., Moos K., Naudi K., Ju X.,
Khambay B.S. (2013) Digital replacement of the distorted
dentition acquired by cone beam computed tomography
(CBCT): a pilot study. International Journal of Oral and
Maxillofacial Surgery (in press).
Peled M., Ardekian L., Krausz A.A. and Aizenbud D. (2004)
Comparing the effects of V–Y advancement versus simple
closure of the upper lip aesthetics after Le Fort I advance­
ment. Journal of Oral and Maxillofacial Surgery, 62,
315–319.
Proffit W.R., White R.P. (eds): Surgical-Orthodontic Treatment.
(1991) St. Louis, Mosby, 170–171.
Rosen H.M. (1988) Lip-nasal aesthetics following Le Fort I
osteotomy. Plastic and Reconstructive Surgery, 81, 171–
179.
Rosenberg A., Muradin M.S., van der Bilt A. (2002) ��������
Nasola­
bial esthetics after Le Fort I osteotomy and V–Y closure:
Statistical evaluation. International Journal of Adult Ortho­
dontics and Orthognathic Surgery, 17, 29–39.
Teuscher U. and Sailer H.F. (1982) Stability of Le Fort I oste­
otomy in ClassIII cases with retropositioned maxillae.
Journal of Maxillofacial Surgery, 10, 80–83.
Soncul M. and Bamber M.A. (2004) Evaluation of soft tissue
changes with optical surface scan after surgical correction
of classIII deformities. Journal of Oral and Maxillofacial
Surgery, 62, 1331–1340.
Swennen, G.R., Mollemans, W., De Clercq, C., Abeloos, J.,
Lamoral, P., Lippens, F., Neyt, N., Casselman, J. and
Schutyser, F. (2009) A cone-beam computed tomography
triple scan procedure to obtain a three-dimensional aug­
mented virtual skull model appropriate for orthognathic
surgery planning. Journal of Craniofacial Surgery, 20(2),
297–307.

Intended learning outcomes
By the end of this chapter the reader should:
• Have an understanding of the indications and
applications of the various orthognathic surgical
procedures.
• Have an awareness of the basic orthognathic
surgical techniques.
Basic orthognathic surgical
procedures
7
Chapter overview
Intended learning outcomes, 111
7.1
Introduction, 112
7.2
Le Fort I osteotomy, 112
7.2.1 Indications, 112
7.2.2 Surgical technique, 112
7.2.3 Le Fort I segmental osteotomies, 116
7.2.4 Complications, 119
7.3
Anterior maxillary osteotomies, 119
7.3.1 Indications, 119
7.3.2 Surgical technique, 119
7.3.3 Complications, 121
7.4
Sagittal split ramus osteotomy, 123
7.4.1 Indications, 123
7.4.2 Procedure, 123
7.4.3 The condylar segments, 125
7.4.4 Complications, 127
7.5
Vertical Subsigmoid Osteotomy
(VSSO), 128
7.5.1 Indications, 128
7.5.2 Procedure, 128
7.5.3 Complications, 130
7.6
Mandibular body osteotomy, 130
7.6.1 Indications, 130
7.6.2 Procedure, 130
7.6.3 Complications, 131
7.7
Inverted L ramus osteotomy, 132
7.7.1 Indications, 132
7.7.2 Procedure, 132
7.7.3 Complications, 133
7.8
Anterior mandibular osteotomies, 133
7.8.1 Lower anterior segmental osteotomy, 133
7.8.2 Anterior mandibulotomy, 134
7.8.3 Complications, 136
7.9
Genioplasty, 136
7.9.1 Indications, 136
7.9.2 Procedure, 136
7.9.3 Complications, 137
7.10  Medical preoperative/intraoperative
considerations and general
postoperative care, 137
7.10.1 Informed consent, 137
7.10.2 Blood tests, 137
7.10.3 Operative considerations, 138
7.10.4 General postoperative care, 138
7.11 Distraction osteogeneis, 139
7.11.1  Mandibular distraction osteogenesis, 140
7.11.2 Maxillary distraction, 143
7.11.3 Compression bifocal and multifocal distraction
osteogenesis, 143
7.12 Further readings, 145
111
• Have an awareness of the potential surgical
complications.
• Have an understanding of the general medical
consideration during and following orthognathic
surgery.
Handbook of Orthognathic Treatment: A team approach, First Edition. Ashraf Ayoub, Balvinder Khambay, Philip Benington,
Lyndia Green, Khursheed Moos, and Fraser Walker.
© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

112
Handbook of Orthognathic Treatment
height before surgery. The distances between internal
points marked on the maxilla above the level of the
Le Fort I osteotomy cut can provide reference for
vertical height changes and horizontal shifts. The
right and left bases of the nose (alar bases) are marked
through the skin using the sharp end of a needle
to measure the width of the nose before surgery
(Figure 7.1b).
Soft tissue reflection
A U-shape incision is made across the mucosa and
deep to the periosteum of the buccal sulcus from the
distal aspect of the first molar around to the opposite
side (Figure 7.2a). A full mucoperiosteal flap is raised
to expose the maxilla from the pyriform aperture
anteriorly to the pterygo-maxillary suture posteriorly
(Figure 7.2b). The infra orbital nerves are identified
and protected. The nasal muco-periosteum is reflected
from the floor of the nose starting at the lateral
margin of the pyriform aperture and extended medi­
Figure 7.1a  Recording the anterior facial height before
surgery.
Figure 7.1b  Recoding the alar base width before surgery.
7.1  Introduction
This chapter illustrates basic surgical techniques for
the correction of dento-facial deformities, it also
highlights the main indications and potential com­
plications of each procedure.
7.2  Le Fort I osteotomy
This procedure is used routinely for the correction of
maxillary positions and discrepancies in jaw size.
7.2.1  Indications
1. Correction of the hypoplastic and retrognathic
maxilla. Due to the anatomical position of the
pterygoid plates, a maxillary posterior shift is
limited to 2–3 mm and removal of bone in the
tuberosity area may be required. The pterygoid
plates should prevent a significant posterior shift
of the maxilla.
2. Correction of vertical maxillary excess and defi­
ciency. Vertical movements of the maxilla at the
Le Fort I level can be used for the correction of
disparities between the upper lip length and the
magnitude of teeth show at rest and with
maximum smile. Surgical lengthening of the
upper lip is usually limited to 2–3 mm.
3. The correction of occlusal canting by impacting
the longer side or down grafting the shorter side
or a combination of both.
4. Correction of an anterior open bite. This is usually
achieved by impaction of the posterior part of the
maxilla to allow the mandible to auto rotate and
close the anterior open bite.
5. Correction of a narrow maxilla and narrow dental
arch.
6. Correction of a prominent anterior maxillary
segment with or without extractions.
7.2.2  Surgical technique
Preparation
Under general anaesthesia an external midline refer­
ence point is usually established at the nasion point
using either a Kirschner wire or a mono-cortical
screw. This is used as a reference point for measuring
the vertical height, before mobilising the maxilla, in
relation to the upper incisal edge or the central point
between the orthodontic brackets on both the right
and left maxillary central incisors (Figure 7.1a). The
distance between the medial canthus and the tip of
the canine can also be used to record the vertical

Basic orthognathic surgical procedures
113
pterygo maxillary suture. The lateral nasal wall is cut
from the palate using a lateral nasal chisel (Figure
7.3c). The maxillary septum is separated from the
palate using a nasal septal chisel (Figure 7.3d).
Separation and mobilisation
The maxillary bone is gradually separated from the
base of the skull using a Smith spreader on each side
(Figure 7.4a). Pterygo-maxillary disarticulation is
achieved using Rowe’s disimpaction forceps (Figures
7.4b, 7.4c, 7.4d). Some surgeons advocate the use of
a curved osteotome but the inappropriate application
of this instrument for the separation of the maxillary
tuberosity from the pterygoid plates can lead to
excessive bleeding and fracture of the pterygoid
plates. Once the maxilla is down-fractured a pair of
Tessier mobilisers is inserted behind the tuberosities
Figure 7.2a  A U-shape muscosal incision on the labial
sulcus across the mucosa and deep to the periosteum.
Figure 7.2b  A full mucoperiosteal flap is from the
pyriform aperture anteriorly to the pterygo-maxillary
suture posteriorly.
Figure 7.2c  Reflection of the nasal mucosa using
Hawath’s periosteal elevator and recording the posterior
height of the maxilla.
Figure 7.2d  Marking the lateral surface of the maxilla to
guide the level of bone cut and avoid occlusal canting.
ally up the nasal septum with a Howarth periosteal
elevator. Internal reference points above the molar
region can be applied to measure the posterior facial
height which guides the vertical changes of the pos­
terior part of the maxilla (Figure 7.2c). Marking the
level of bone cut on the maxilla maintains the verti­
cal symmetry of the osteotomy and prevents canting
of the occlusion (Figure 7.2d).
Bone cut
The outer surface of the maxilla is marked using a
marking pen (Figure 7.2d) before it is cut using a
surgical bur or a saw from the buttress part of the
zygoma upward and forward to the lateral corner of
the pyriform aperture about 8 mm above the apices
of the roots (Figures 7.3a, 7.3b). A curved saw is used
to complete the cut backwards and downwards to the

114
Handbook of Orthognathic Treatment
Figure 7.3a  Bone cut using surgical saw about 8 mm
above the apices of the teeth.
Figure 7.3b  Saw from buttress part of the maxilla upward
and forward to the lateral corner of the pyriform aperture.
Figure 7.3c  Cutting the lateral nasal wall using a lateral
nasal chisel.
Figure 7.3d  Separation of the septum from the palate
using a nasal septal chisel.
Figure 7.4a  Gradual separation of the maxilla from the
base of skull using a Smith spreader.
Figure 7.4b  The application of Rowe’s dysimpaction
forceps for pterygo-maxillary disarticulation.

Basic orthognathic surgical procedures
115
lary sinus (the lateral nasal wall) and the inferior
border of the nasal septum itself which is readily ac­
cessible from the nasal surface of the palate (Figure
7.4f). Inferior turbinectomy may be required in cleft
cases and where significant impaction is needed. In
cases of maxillary down grafting, iliac bone graft may
be inserted as interpositional material (Figure 7.5a).
However, this will depend on the magnitude of the
inferior maxillary shift, the associated advancement
and quality of bone. The standard method of fixing
the maxilla into its final position is by using four
1.7 mm bone plates. Two placed on each side, one at
the pyriform aperture and the other in the buttress
part of the maxilla (Figure 7.5b). Poly L-Lactide
(PLLA) resorbable plates can also be used for fixation
(Figures 7.5c, 7.5d). The stability of a large maxillary
advancement can be improved with the insertion of
cortico-cancellous bone blocks in the gap created be­
tween the maxilla and the base of the skull at the
Figure 7.4c  The position of the mobilisation forceps’
blades on the nasal surface of the maxilla.
Figure 7.4d  The position of the mobilisation forceps’
blades on the oral surface of the maxilla.
Figure 7.4e  The application of Tessier mobilisers behind
the tuberosities to mobilise and advance the maxilla.
Figure 7.4f  Shows the greater palatine artery at the
posterior edge of the palate.
to mobilise and advance the maxilla (Figure 7.4e).
This is a mandatory manoeuvre aimed at stretching
the soft tissues attached to the maxilla, to minimise
postoperative relapse. Damage to the greater palatine
artery (Figure 7.4f) should be avoided during the
manoeuvre.
Final adjustments and fixation
The prefabricated occlusal wafer is seated on the in­
cisal edges and occlusal surfaces of mandibular teeth.
The maxilla is then placed in the pre planned antero-
posterior occlusal relationship and kept in place using
temporary intermaxillary fixation. The vertical height
is adjusted in relation to the external or internal refer­
ence points to achieve the pre planned vertical posi­
tion of the maxilla. Bone removal is required for
maxillary impaction. It is usually removed from the
buttress area of the maxilla, and from the septum at
the mid-palatal suture, the medial wall of the maxil­

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Handbook of Orthognathic Treatment
through the same penetration point of the skin to
inside the mouth to anchor the alar cartilage. This is
repeated with the same suture for the other alar car­
tilage of the opposite side and the two ends of the
suture are then anchored through a hole drilled in
the anterior nasal spine (Figure 7.6c). A cinch stitch
can be also carried out by anchoring each alar carti­
lage separately to a drilled hole through the anterior
nasal spine.
7.2.3  Le Fort I segmental osteotomies
Mid-palatal split (Figures 7.7a, 7.7b)
Indications.  The main indication of this surgical
procedure is the correction of a narrow maxilla and
Figure 7.5b  Two 1.7 mm plates placed on each side, one
at the pyriform aperture and the other in the buttress part
of the maxilla.
Figure 7.5c  Poly L-Lactide (PLLA) resorbable plates.
Figure 7.5d  The application of PLLA plates for fixation of
Le Fort I osteotomy.
Figure 7.5a  Bone graft inserted as interpositional
material.
buttress area posteriorly, at the buccal surface of the
maxilla and at the pyriform aperture. There is con­
siderable debate in the literature regarding the indica­
tions of bone grafting, however, there is a general
agreement that maxillary advancements more than
8 mm with or without vertical height augmentation
would benefit from grafting.
Closure
A V-Y closure may be considered where lip lengthen­
ing is required. This is achieved by suturing, in the
midline, the mucosal surface of the upper lip first
followed by suturing the mucoperiosteal flap bucally
and labially (Figure 7.6a). A cinch stitch can then be
applied to maintain or achieve the desired alar base
width which tends to widen in Le Fort I osteotomy
cases. This is usually carried out using a 3(0) non-
resorbable suture that is passed from inside the
mouth underneath the reflected mucoperiosteum to
the skin of the right alar base (Figure 7.6b), then

Basic orthognathic surgical procedures
117
Figure 7.6a  Suturing, in the midline, the mucosal surface
of the upper lip first followed by suturing the
mucoperiosteal flap bucally and labially to achieve a V-Y
closure for lip lengthening.
Figure 7.6b  Cinch stitch passed from inside the mouth to
the skin of the base of the nose to anchor the alar
cartilage.
Figure 7.7a  A fine fissure bur is used for the para sagittal
palatal bone cut.
Figure 7.7b  The application of Smith spreader to split the
maxilla into two segments across the midline.
Figure 7.6c  A cinch stitch carried out by anchoring alar
cartilages to a drilled hole in the anterior nasal spine.
narrow dental arch. This technique deals with poste­
rior cross bite where correction is indicated and
is beyond the scope of orthodontic treatment. A
maximum 8–10 mm increase in the posterior maxil­
lary width can be achieved with mid-palatal osteot­
omy. It is an unstable procedure, therefore, adequate
fixation and mid-palatal bone grafting are necessary
to reduce postoperative relapse.
Technique.  Right and left para-sagittal bone cuts are
made through the nasal surface of the palate with a
fissure bur (Figure 7.7a). A fine fissure bur and a thin
spatula osteotome are used for the remaining vertical
labial bone cut between the roots of the central max­
illary incisors and palate. This area is exposed by
tunnelling from above the labial mucoperiosteum
between the central incisors. The attached gingiva
should be kept intact. Following this, the maxilla can
be split into two segments using a Smith spreader

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Handbook of Orthognathic Treatment
(Figure 7.7b). The removed mid-palatal strip of bone
can be cut into sections for grafting and wedging in
the same surgical site at the mid-palatal suture fol­
lowing the mobilisation of the two halves of the
maxilla. Mobilisation is essential, and this is usually
achieved after reflection of the palatal mucoperios­
teum at the para-sagittal cut from the nasal side.
Maintaining the integrity of the mucoperiosteum is
essential in segmental Le Fort I osteotomies and una­
voidable perforations require careful suturing. Some
surgeons advise additional fixation of the two maxil­
lary segments by applying an extra plate on the labial
surface of the maxilla below the pyriform aperture.
Two piece maxillary osteotomy (Figures 7.8a, 7.8b)
The main indication of this surgical procedure is the
correction of an anterior open bite. This is usually
achieved by impaction of the posterior part of the
maxilla to allow the mandible to auto rotate and
close the anterior open bite.
Figure 7.8a  The horizontal cut across the palate to
separate the anterior part of the maxilla from the
posterior segment.
Figure 7.8b  Fixation of the two-piece maxillary
osteotomy using 1.7 mm titanium plates.
Figure 7.8c  Anterior maxillary osteotomy of the three-
piece maxillary osteotomy.
Surgical technique.  This can be most easily achieved
once the maxilla is down fractured at the Le Fort I
level. Access to the buccal surface of the maxilla in
the area of the first or second premolars is achieved
by incising the gingival sulcus around the premolars
and tunnelling the mucoperiosteum using a periostel
elevator. The bone cuts are made using a tapered
fissure bur from the horizontal maxillary osteotomy
line to the alveolar crest on each side of the maxilla.
A thin spatula osteotome can facilitate this bone cut
which should extend to involve the palatal bone
whilst maintaining the integrity of palatal mucoperi­
osteum. The ends of the two vertical osteotomy lines
are connected to the horizontal bone cut across the
nasal surface of the palate (Figure 7.8a). The anterior
maxillary segment can then be mobilised, reposi­
tioned in to its final position guided by the acrylic
occlusal wafer and fixed in position using two plates
on each side (Figure 7.8b).
Three-piece maxillary osteotomy (Figure 7.8c)
Indication.  The main indication of this surgical pro­
cedure is the correction of a narrow posterior maxilla
and allowing differential vertical movements of the
anterior and posterior segments of the maxilla. The
procedure should be considered for correction of
anterior open bite which is associated with a narrow
maxillary dental arch posteriorly.
Technique.  This surgical technique provides a com­
bination of anterior maxillary osteotomy and poste­
rior mid-palatal split. The sagittal palatal bone cut is
achieved as explained above but would only extended
to the horizontal palatal cut of the anterior part of
the maxilla, that is, no vertical cut is made between
the roots of the central incisors. The three bone seg­

Basic orthognathic surgical procedures
119
2. Gingival recession and loss of the inter-dental
papillae.
3. Loss of the vitality of the teeth adjacent to the
osteotomy lines.
4. Oro-antral communications due to perforation of
the palatal mucoperiosteum.
5. Relapse which is the most common complication.
6. Loss of bone segments due to infection and
damage to the blood supply which is rare.
7.3  Anterior maxillary osteotomies
7.3.1  Indications
The anterior segment of the maxilla can be osteot­
omised separately using the Wassmund or the
Wunderer approach. The following are the main indi­
cations for this osteotomy:
1. Maxillary prognathism where posterior move­
ment of the maxilla is not required.
2. Anterior vertical maxillary excess with excessive
gingival show.
3. Protrusion of the anterior segment of the maxilla
with proclined upper incisors but a satisfactory
posterior occlusion (Figure 7.9).
4. Anterior open bite caused by anterior vertical defi­
ciency of the maxilla with reduced tooth show.
7.3.2  Surgical technique
Wassmund approach
This approach is used for the correction of discrepan­
cies in the antero-posterior position and axial inclina­
tion of the anterior part of the maxilla whilst
producing minimal change in vertical height.
ments (right posterior maxillary, left posterior maxil­
lary and anterior maxillary segments) are adjusted
into their pre-planned position, guided by the acrylic
occlusal wafer, temporary inter maxillary wiring is
applied and the segments are finally fixed in place
with mini plates.
Four-piece maxilla (Figure 7.8d)
Indication.  The main indication of this surgical pro­
cedure is the correction of a transverse maxillary defi­
ciency which involves both the inter-canine and
inter-molar width. It also allows differential vertical
movements of the anterior and posterior segments of
the maxilla. The procedure should be considered for
correction of anterior open bite which is associated
with a narrow maxillary dental arch at the canine and
molar regions.
Technique.  This provides a combination of the full
antero-posterior mid-palatal split of the maxilla,
including the vertical labial bone cut between the
roots of central incisors, and the standard anterior
maxillary osteotomy. The sagittal palatal bone cut
is achieved as explained above. This is then con­
nected with the horizontal palatal cut of the anterior
maxillary osteotomy. This allows widening of the
posterior part of maxilla medio-laterally as well as an
increase in the inter-canine width. The maxilla is split
into four segments (right posterior maxillary, left pos­
terior, right anterior and left anterior) which are then
adjusted into their pre-planned position, using the
occlusal wafer, and fixed in place using mini plates.
7.2.4  Complications
The following are the most common complications
associated with segments Le Fort I osteotomies:
1. Damage to the side of the roots and apices of the
teeth adjacent to the osteotomy cut.
Figure 7.9  A preoperative and postoperative profile
photograph shows the improvement of appearance
following anterior maxillary osteotomy.
Figure 7.8d  Four piece Le Fort I maxillary osteotomy.

120
Handbook of Orthognathic Treatment
main blood supply to the osteotomised segment and
should be kept intact.
Guided by the occlusal wafer and temporary inter-
maxillary fixation the segment is fixed in the pre-
planned position using mini plates. Bone removal is
usually required between the two cut surfaces (ante­
rior and posterior maxillary bone segments), both
buccally and palatally, to allow accurate positioning
of the anterior maxillary segment. Wounds are closed
using 4 (0) resorbable sutures.
Wunderer approach
This approach is used mainly for correction of verti­
cal discrepancies of the anterior part of the maxilla
with minimal antero-posterior changes.
The approach to the buccal surface of the maxilla
is similar to the Wassmund approach. The buccaly
bone cut is usually at the first premolar region.
A curved or inverted L incision is performed above
the apex of the first premolar. A buccal mucoperio­
steal flap is reflected to expose the buccal surface of
the maxilla from the alveolar crest to the pyriform
aperture on each side. The nasal floor is reflected
using the rounded end of the Mitchell’s osteo-
trimmer. Through a palatal gingival sulcus releasing
incision from the canine to the second premolar the
palatal mucoperiosteum is tunnelled from the alveo­
lar crest to the mid-palatine suture bilaterally.
A bone cut is performed on each side using a surgi­
cal fissure bur after the extraction of the first premo­
lar or at an edentulous area distal to the maxillary
canine. The cut extends from the pyriform fossa dis­
tally above the apices of the teeth and vertical down
at the edentulous area or through the alveolar bone
before or after the extraction of the first premolar
(Figure 7.10a). The buccal cortical bone cut extends
to the palatal cortex. The use of a spatula osteotome
facilitates the bone cut at the maximum height of the
palate. The tunnelled palatal mucoperiosteum (Figure
7.10b) provides the necessary access for a surgical
fissure bur and osteotome to complete the bone cut.
Through a vertical incision of the labial mucoperios­
teum overlying the anterior nasal spine (Figure 7.10c,
a) nasal septal chisel is applied to separate the nasal
septum for full mobilisation of the anterior maxillary
segment. The palatal mucoperiosteum provides the
Figure 7.10a  Bone cut extending from the pyriform fossa
distally above the apices of the teeth and vertical down
on the buccal surface of the maxilla.
Figure 7.10b  Tunnelling of the palatal mucoperiosteum
to facilitate palatal bone cut.
Figure 7.10c  A vertical incision of the labial
mucoperiosteum overlying the anterior nasal spine to
facilitate cutting of the nasal septum.

Basic orthognathic surgical procedures
121
incision (Figure 7.11c). Bone is removed from the
latter using a surgical cylindrical bur (Figure 7.11c)
or bone nibblers for upward movement of the ante­
rior maxillary segment without interference with
the nasal mucoperiosteum.
Fixation of the anterior maxillary segment and
closure of the surgical wounds are similar to the
Wassmund approach in addition to careful suturing
of the palatal flap.
7.3.3  Complications
1. Perforation of the palatal mucoperiosteum with
the Wassmund approach and inadequate closure
of the palatal mucoperiosteum with the Wunderer
approach can lead to an oro-nasal fistula. Careful
tunnelling of the palatal mucoperiosteum and
double suturing of the palatal mucoperiosteum in
the Wunderer approach should minimise this risk.
An oro-nasal fistula requires surgical repair.
2. Gingival recession and damage to the roots of the
teeth adjacent to the osteotomy cut are potential
complications which are avoidable through careful
planning and presurgical orthodontic adjustment
of the angle of the roots of the teeth adjacent to
the osteotomy cut.
3. Relapse is usually minimal with these procedures
due to limited occlusal changes and minimal alter­
ations of the oro-facial muscles.
General complications associated with maxillary
osteotomies
1. Surgical complications
Excessive bleeding during surgery is unusual. The
average blood loss associated with Le Fort I osteot­
omy is about 500 ml. Excessive blood loss during
Through a transverse palatal incision from the first
premolar of one side to the other, the palatal muco­
perioteum is reflected backward and the palatal
bone is exposed (Figure 7.11a). The palatal bone cut
is readily performed using a surgical fissure bur. The
application of a spatula osteotome through the
bone cuts on the buccal and palatal surfaces facili­
tates the mobilisation of the anterior segment of
the maxilla. The osteotomy segment is rotated in
an anti-clockwise direction (Figure 7.11b) so that its
nasal surface becomes accessible through the palatal
Figure 7.11a  Transverse palatal incision from the first
premolar of one side to the other, the palatal
mucoperiosteum is reflected backward and the palatal
bone is exposed. Source: Medical Illustration Department,
Glasgow Royal Infirmary, Greater Glasgow & Clyde NHS
Trust.
Figure 7.11b  Rotating the osteotomy segment in an
anti-clockwise direction so that its nasal surface becomes
accessible through the palatal incision.
Figure 7.11c  Bone removal from the posterior edge and
superior surface of the anterior part of the maxilla.

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Handbook of Orthognathic Treatment
uncommon following a Le Fort I osteotomy. Avoiding
the damage to the nasal mucoperiosteum minimises
the risk of this bleeding; it tends to settle within 24
hours, the application of a nasal pack may have to
be considered.
c.  Vomiting
Vomiting is more likely to occur within the first few
hours following surgery and patients must be
informed of this possibility. Intermaxillary fixation
may be required to be released, if this was in place,
but in most cases where guided elastics are used, the
inter-occlusal space will allow vomit to escape.
Routine administration of antiemetics minimise the
incidence of vomiting.
d.  Relapse
• Immediate
Relapse occurs within the first few days post-
operatively following the release of the intermaxil­
lary elastics, this manifests as an anterior open bite.
This is usually in cases where sufficient posterior
impaction of the maxilla for closure of an anterior
open bite was not achieved. The result is distraction
of the condyle out of the glenoid fossa per-operatively,
rather than true autorotation of the mandible.
• Delayed
Relapse is the most common complication following
Le Fort I osteotomy. A Le Fort I maxillary impaction
is the most stable surgical movement. On the other
hand, maxillary downward movement is the most
unstable movement, the application of autogenous
bone graft following significant maxillary downward
movement tends to minimise postoperative relapse.
There is sufficient evidence in the literature to
support the concept that relapse is directly related to
the magnitude of maxillary advancement. The most
unstable surgical movement is medio-lateral poste­
rior widening of the palate. The use of rigid fixation,
the application of bone graft at the mid-palatal
suture and positive intermaxillary occlusal inter-
digitation following surgery should minimise this
complication. The use of an occlusal wafer, as an
external method of fixation of the two maxillary
segments minimises the magnitude of medio-lateral
relapse.
3. Delayed complications:
a. Effects on the nose
Deviation of the nasal septum and widening of the
alar base have been reported following Le Fort I maxil­
lary impaction and advancement. The former can be
avoided by ensuring that there has been sufficient
nasal septal reduction and palatal bone removal. The
application of a nasal cinch stitch to approximate the
alar cartilages and the surgical widening of the pyri­
surgery can be prevented with careful handling of the
soft tissues and by avoiding damage to major blood
vessels close to the surgical sites. Excessive bleeding
may result from damage of the descending greater
palatine vessels and the pterygoid venous plexus.
This can be reduced by avoiding high posterior max­
illary cut, ensuring gentle pteyrgo-maxillary disar­
ticulation
and
by
the
use
of
hypotensive
anaesthesia.
Damage to the roots of the teeth is a potential
complication. This is more likely to occur in segmen­
tal osteotomies due to the close proximity of the
osteotomy cuts to the roots of the adjacent teeth.
This can usually be avoided through orthodontic
divergence of the adjacent roots. Damage to the roots
of teeth can also occur during plate fixation due to
close proximity of the root apices to the tips of the
fixation screws.
Tearing of the palatal mucoperiosteum is most
likely to occur with segmental osteotomies used
for extensive posterior widening of the maxilla.
Careful suturing of any localised tear is essential
together with the maintenance of an intact nasal
floor mucosa.
Difficulty in achieving the required magnitude of
movement is a serious problem which may occur due
to unrealistic pre-planned maxillary advancement or
due to inaccuracies in face bow recording, occlusal
registration and model surgery planning. These can
all introduce errors into the fabrication of the occlu­
sal wafer which determines the antero-posterior sur­
gical movements of the maxilla.
2. Immediate postoperative complications:
a.  Pain
Pain is the most common complication reported by
patients who have undergone a Le Fort I maxillary
osteotomy. A standard protocol of pain management
should be readily available for delivery by the desig­
nated nurse or the consultant anaesthetist during the
immediate postoperative period. Morphine injection
should be considered provided the respiratory rate
and oxygen saturation are within the normal range.
b.  Swelling
Swelling may not be a major complication following
surgery because of steroid injections during surgery
and postoperatively in the first 24 hours. Patients
should be warned that facial swelling is likely to
increase after the effects of the steroid wear off and
may remain for up to a few weeks after surgery.
Localised swelling, due to a surgical hematoma,
should be recognised as early as possible, this may
require surgical intervention with drainage or by
dealing with the damaged tissues. Epistaxis is not

Basic orthognathic surgical procedures
123
angle and posterior part of the body of the mandible
laterally. The first cut is limited to the medial cortex
just above the lingula, the inferior dental nerve
should be identified and protected (Figure 7.12b).
The higher the cut, the less the chance of an uncom­
plicated split of the ramus. To avoid a potential unfa­
vourable split this cut is kept short, just behind the
lingula and does not extend to the posterior border
of the mandible (Hunsuck modification) (Figure
7.12b). A routine surgical fissure bur or Lindemann
bur or straight saw can be used to make this cut.
Using a standard fissure bur the sagittal bone cut is
made just lingual to the external oblique ridge of
the buccal cortex of the mandible connecting to the
lingual cut (Figure 7.12c) and then passing down
form should prevent flaring of the alar base. However,
the long term stability of the cinch stitch is doubtful.
b. Altered sensation
Persistent alteration of sensation around the cheeks,
lateral side of the nose and the upper lip can occur
as a result of damage to the infra orbital nerve. This
can be avoided by careful protection of the nerve and
positioning of the plates during surgery. Patients may
also complain of altered sensation around the gingi­
vae due to damage to the branches of the superior
alveolar nerves. In most cases the sensation gradually
improves with time.
Oro-antral and oro-nasal fistulae, loss of the vitality
of maxillary teeth especially with segmental osteoto­
mies, and exposure of fixation plates are late compli­
cations that have been reported in the literature.
7.4  Sagittal split ramus osteotomy
(Figure 7.12a)
This technique is used routinely for the surgical cor­
rection of both mandibular deficiency and prognath­
ism. The technique was developed by Trauner and
Obwegeser and has undergone several modifications
to improve its reliability and safety.
7.4.1  Indications
1. Surgical correction of mandibur retrognathism
and antero-posterior deficiency.
2. Correction of mandibular prognathism.
3. Correction of mandibular asymmetry.
4. Correction of small anterior open bite.
7.4.2  Procedure (Figure 7.12a)
Surgery is carried out under general anaesthesia
exposing subperiosteally the ramus medially and the
Figure 7.12a  Plastic model showing the bone cuts of the
sagittal split osteotomy.
Figure 7.12b  Medial cortex short horizontal bone cut just
above the lingual and does not extend to the posterior
border of the mandible (Hunsuck modification) the
vertical line illustrates the pattern of medical cortex split
from the outer cortex of the ramus of the mandible.
Figure 7.12c  A sagittal bone cut made just lingually to
the external oblique ridge of the buccal cortex of the
mandible.

124
Handbook of Orthognathic Treatment
the anterior border of the ramus connecting with a
buccal surface osteotomy (Figure 7.12d). According
to the Dal Pont modification the buccal bone cut is
located more anteriorly away from the angle of the
mandible just distal to the second molar tooth. This
bone cut is limited to the buccal cortex connecting
with the sagittal osteotomy, with the bone cut at the
inferior border of the mandible. The latter is achieved
using a surgical fissure bur after careful reflection and
retraction of the mucoperiosteum at the inferior
border of the mandible. That cut must be limited to
the inferior cortical bone taking into consideration
the position of the inferior dental nerve. Some sur­
geons tend to carry the sagittal osteotomy of the
inferior border of the mandible posteriorly to achieve
a more precise sagittal split of the ramus, however,
this is not universally practised.
After completion of the bone cuts the ramus is split
sagittally using a combination of osteotomes (Figure
Figure 7.12d  The osteotomy of the buccal surface
connecting to the sagittal bone cut.
Figure 7.12e  Completion of the sagittal split bone cut
using an osteotome.
Figure 7.12f  Gradual separation of the lateral surface of
the ramus (proximal segment) from the rest of the
mandible (distal segment) using Smith spreader.
Figure 7.12g  Gradual separation of the two segments to
avoid fracture of the buccal or the lingual cortices.
7.12e) and Smith spreader (Figure 7.12f) which allows
gradual separation of the lateral surface of the ramus
(proximal segment) from the rest of the mandible
(distal segment) (Figure 7.12g) and much reduces the
risk of damage to the inferior dental nerve which is
the main complication of this procedure. Gradual
separation of the two segments allows the identifica­
tion of the inferior dental bundle (Figure 7.12h).
Ideally, it should be located on the distal segment;
however, in some cases the nerve may be attached to
the proximal segment within the bony canal of the
mandible. In these cases it should be carefully dis­
sected out using a combination of fine osteotomes
and an excavator. A fissure bur can be used for bone
removal and de-roofing of the mandibular canal fol­
lowed by using a blunt dissection instruments to
ensure the nerve bundle is freed from the proximal
segment, this helps to ensure it lies lingually on the
distal segment.

Basic orthognathic surgical procedures
125
Figure 7.12h  Identification of the inferior dental bundle
with the gradual separation of the osteotomy segments.
Figure 7.12i  The trans-buccal approach for a direct
access to the osteotomy site.
Figure 7.12j  Three bi-cortical screw used for fixation of
the sagittal split osteotomy.
Figure 7.12k  PLLA resorbable screw fixation of the
sagittal split osteotomy.
The pterygo-masseteric sling should be detached
from the inferior border of the distal segment to
allow free mobilisation of the body of the mandible
in an antero-posterior direction.
Guided by a prefabricated occlusal wafer, several
methods have been used successfully for fixation of
the mandible in its final position. These include
three bicortical screw fixations or a 2 mm titanium
plate fixation on each side of the mandible. Despite
the fact that a wire fixation alternative may achieve
a satisfactory fixation of the bony segments, the long
term results showed suboptimal stability due to the
quality of the bone formation at the osteotomy site
with this type of fixation. The author uses the trans-
buccal approach routinely which provided a direct
access to the bone segments (Figure 7.12i) and the
insertion of a three bi-cortical screws for fixation
(Figure 7.12j). The trans-buccal approach may not
be required if an upper border plate is used for fixa­
tion of the osteotomy segments. Despite the fact that
titanium bicortical screws have routinely been used
for fixation, PLLA resorbable screws have also been
successfully utilised for this purpose (Figure 7.12k).
7.4.3  The condylar segments
The most important and trickiest manoeuvre during
fixation of the sagittal split osteotomy is the accurate
repositioning of the condyle or the proximal segment
in its normal anatomical position. Various methods
have been used to guide the condyle into its fossa
using positioning plates and condylar devices (Figure
7.13a), however, their application is cumbersome and
time consuming which limits their routine use (Figure
7.13b). Every effort should be made to maintain the
condyle in its fossa, avoiding posterior displacement.
Gentle extra oral vertical pressure at the angle of the
mandible and light intra oral posterior force at the
anterior border of the ramus would facilitate the posi­
tioning of the condylar segment in the articular fossa
(Figure 7.13c).

126
Handbook of Orthognathic Treatment
Figure 7.13a  A condylar positioning device maintaining
the relationship between the ramus and the zygoma.
Figure 7.13b  Insertion of a condylar positioning device.
Figure 7.12l  CBCT
showing the medio-lateral
width of the ramus, the
position of the mandibular
foramen, and the course
of the inferior dental
nerve.
Bone removal from the anterior border of the prox­
imal segment will be required in mandibular setbacks
to allow appropriate overlap and adequately fix the
bone segments.
Asymmetric advancement of the mandible tends
to lead to lateral displacement of the proximal segment
on one side. Due to the shape and angulation of the
mandibular rami in relation to the mid-sagittal plane,
lateral displacement of the condylar segments may
also occur following symmetrical mandibular advance­
ment. Torquing of the condylar segments (proximal
segments) medially to achieve bony contact during
fixation should be avoided. In these cases removal
of bone from the medial surface of the proximal
segment would be indicated to improve the adapta­
tion between the osteotomy segments during fixation,
thus minimising the torque on the proximal segment.
This should reduce the incidence of TMJ dysfunction
following surgery, unwanted excessive remodelling
of the condyle and ultimately mandibular relapse.
For most cases drains are not required following
sagittal split ramus osteotomy. Resorbable sutures are

Basic orthognathic surgical procedures
127
These complications could be avoided by careful
planning, meticulous bone cutting and the avoid­
ance of excessive pressure during splitting of the
ramus from the body of the mandible. Fracture of the
lingual plate would necessitate the use of buccal bone
plate for fixation of the osteotomy segments. The
fractured lingual segment may be kept in place pro­
vided the surrounding mucoperiosteum is intact. A
fractured buccal plate may be replaced and fixed back
into its position using mini plates, small segments
could be safely removed or left to act as bone graft.
Horizontal fracture of the ramus may require fixation
before final splitting of the mandible. In unusual
cases where a sagittal split of the ramus cannot be
achieved the surgeon may abort the procedure and
consider a vertical subsigmoid osteotomy in cases
where a mandibular set back is required or body oste­
otomy and bone graft could be used to achieve the
required mandibular advancement.
Damage to the inferior dental nerve can occur with
the sagittal split osteotomy due to the following:
1. Insufficient knowledge of the position and course
of the nerve which can only accurately be achieved
from analysis of the preoperative CBCT (Figure
7.12l).
2. Excessive force applied during splitting of the
proximal segment of the ramus.
3. Extending the depth of the buccal bone cut
beyond the outer cortex.
4. Cutting more than the inferior border of the man­
dible vertically in an occlusal direction beyond the
cortex.
5. Penetration of the bundle and nerve during screw
fixation.
A cut nerve during a sagittal split osteotomy may
require the nerve to be repaired. A contused nerve
would gradually recover, but patients may suffer from
residual alteration of sensation which can manifest
as paraesthesia rather than complete numbness.
Immediate postoperative complications
The most common immediate postoperative compli­
cations are pain, swelling and limitation of mouth
opening. These are likely to improve within a few
days of surgery. The more serious complication is
immediate relapse upon the release of intermaxillary
elastic fixation. This could be manifested as one of
the following clinical features:
1. Anterior open bite.
2. Displacement of the mandible toward one side
with mouth opening.
3. Posterior displacement of the mandible with an
increase of overjet.
used for closure of the intraoral incision and 5 (0)
Ethilon for the trans-buccal skin incision of the
cheek. Light elastics should be applied to guide the
mandible into its new postoperative position.
7.4.4  Complications
Surgical
The most common surgical complication of this
osteotomy is an unfavourable split of the mandible
which can manifest as one or a combination of the
following:
1. Fracture of the lingual plate of the distal segment
of the mandible.
2. Fracture of the buccal cortex of the proximal
segment.
3. Failure to separate the proximal from the distal
segments.
4. Fracture of the ascending ramus of the mandible.
Excessive force during splitting of the mandible is
the likely cause of this complication. Anatomical
variations may also play a role especially in syndro­
mic cases and may cause an unfavourable split. The
use of preoperative cone beam CT, which is routinely
obtained for our cases, it allows the assessment of the
medio-lateral thickness of the ramus and the position
of the inferior dental nerve to minimise the risk of
this complication and damage to inferior dental
nerve (Figure 7.12l). It has been shown that early
removal of mandibular wisdom teeth can minimise
the risk of unfavourable sagittal split osteotomy.
Figure 7.13c  Positioning the condylar segment in the
articular fossa by gentle extra oral vertical pressure at the
angle of the mandible and light intra oral posterior force
at the anterior border of the ramus.

128
Handbook of Orthognathic Treatment
3. Management of TMJ dysfunction syndrome.
4. Where it is essential to minimise loss of sensation
of the lower lip.
7.5.2  Procedure
This technique has been developed and modified to
be performed intra-orally for correction of mandibu­
lar prognathism. The procedure is performed under
general anaesthesia. Through an intra-oral approach
the outer surface of the ramus is exposed from the
sigmoid notch to the angle of the mandible. Specific
retractors need to be used (Bower’s retractor for the
sigmoid notch and a Levasseur-Merril retractor for
reflection of retro-mandibular soft tissues (Figure
7.14a)) to provide protection of the saw as it cuts the
the ramus vertically. Excellent illumination is manda­
tory to perform this surgical technique safely. An
oscillating right angle surgical saw (Figure 7.14b)
The cause for these immediate postoperative com­
plications is usually displacement of condylar segment
during internal fixation. Postoperative radiographs
would show displacement of the condylar segment
which would require further surgical intervention to
reseat the condylar segment into its correct position.
Long term complications
Alteration in the sensation of the lower lip is the most
common complication reported by the patients who
had had sagittal split osteotomy. The manifestation
ranges from localised alteration of sensation at a par­
ticular area to complete numbness of the lower lip.
In most of the cases patients show a high level of
adaptation to this complication and it is unlikely that
altered lip sensation following sagittal split osteot­
omy would affect the quality of their life. This may
not be the case if the lip numbness is secondary to
removal of wisdom teeth.
Delayed relapse is the second most common com­
plication following sagittal split osteotomy and
research has proved the following factors to contrib­
ute to this complication:
1. The magnitude of mandibular advancement.
2. Quality of postoperative occlusion.
3. Condylar position during fixation of sagittal split
osteotomy.
4. Rigidity of sagittal split fixation.
5. Stretching of the supra hyoid muscles due to anti-
clockwise rotation of the distal segment.
6. Bone quality and postoperative infection.
7. Preoperative condylar shape and size.
This could be minimised with appropriate plan­
ning, accurate execution of the surgery, avoidance of
condylar displacement, stable internal fixation and
excellent postoperative occlusion.
Numbness of the tongue and submandibular region
has been reported due to damage to the lingual nerve
and damage to the nerve to mylohyoid muscle which
supplies innervations to the mental area. Infection
and exposure of the fixation plates and screws have
been reported in about 10% of the cases and they
would require surgical removal of the fixation device.
Scarring at the site of the skin incision of the trans-
buccal approach has been noted in some cases.
7.5  Vertical Subsigmoid Osteotomy
(VSSO) (Figure 7.14)
7.5.1  Indications
1. Correction of mandibular prognathism.
2. Correction of mandibular asymmetry where a uni­
lateral VSSO may be performed with or without a
sagittal split osteotomy on the opposite side.
Figure 7.14a  Levasseur-Merril retractor is inserted intra
orally for reflection of retro-mandibular soft tissues and
also to provide protection of the saw as it cuts the ramus
vertically.
Figure 7.14b  The application of an oscillating right angle
surgical saw for vertical cutting of the ramus.

Basic orthognathic surgical procedures
129
7.14e) attached to the lateral pterygoid muscle and
the capsule of the condyle. To avoid extensive lateral
flaring of the condylar segment a non-resorbable
stitch may be applied to approximate the segment to
the buccal surface of the ramus of the mandible and
promote satisfactory initial bone healing, it also pre­
vents sagging of the condylar segment. The classic
method of fixation of vertical subsigmoid osteotomy
is by inter-maxillary fixation and the condylar seg­
ments would find their own presurgical anatomical
position. However, surgeons have attempted internal
fixation of the condylar segment using bicortical
screws and plates to avoid the inconvenience associ­
ated with wiring the maxillary and mandibular teeth
together. Internal fixation may require trans-buccal
approach to allow direct access for application of
plates or screws.
The VSSO had been introduced and adopted by
surgeons to avoid the following complications which
were associated with sagittal split osteotomy for a
mandibular set back:
1. Damage to the inferior dental nerve.
2. Anterior relapse.
3. Displacement of the condylar segment.
However, damage of the inferior dental nerve
during surgery has not been totally eliminated with
VSSO and inter maxillary fixation may compromise
immediate postoperative recovery and undoubtedly
does cause significant inconvenience for the patient.
Delay of applying IMF for a few days after surgery has
been suggested to facilitate postoperative recovery,
but there are risks for the proximal segment to be
displaced inferiorly and for anterior open bite to
facilitates bone cutting from the sigmoid notch to the
inferior border of the mandible just anterior to the
angle of the ramus and posterior to the lingula. Once
the cut is complete, a periosteal elevator is inserted
at the sigmoid notch to laterally mobilise the condy­
lar (proximal) segment in relation to the ramus of
the mandible (Figure 7.14c). The attachment of the
medial pterygoid muscle is reflected to allow poste­
rior movement of the distal segment. The proximal
segment is kept lateral to the ramus (Figures 7.14d,
Figure 7.14c  Insertion of a periosteal elevator to laterally
mobilise the condylar (proximal) segment in relation to
the ramus of the mandible.
Figure 7.14d  VSSO with the proximal segment kept
lateral to the ramus.
Figure 7.14e  Radiographic appearance of the VSSO.

130
Handbook of Orthognathic Treatment
ing using the Levasseur-Merill retractor. Rarely this
may be due to anatomic variations in asymmetry
cases which can be diagnosed by the assessment of
submento-vertex radiograph or cone beam CT scan
prior to surgery. For minor degrees of asymmetry, the
easy side of the mandible, where the ramus is more
flared laterally, should be osteotomised first as it
renders the other side better access. Patients should
be warned if there is a problem it is always possible
to complete surgery with external submandibular
approach.
7.6  Mandibular body osteotomy
7.6.1  Indications
1. Correction of prognathism due to an increased
body length of mandible.
2. Unilateral correction of asymmetric mandible
with or without ramus osteotomy of the opposite
side.
This method provides good bony contacts between
the proximal and distal segment. Damage to the infe­
rior dental nerve is minimal and the reported long
term stability is excellent.
7.6.2  Procedure
This osteotomy is carried out under general anaesthe­
sia via an intra-oral approach. A full buccal and
lingual segment is removed with the preservation of
the integrity of the inferior alveolar nerve for reduc­
tion of the mandibular body length. The first molar
region is a good site for a body ostectomy, however,
this would depend on the location of the edentulous
area or an extraction and the pre-planned final occlu­
sion. In some cases extraction of the first premolar
provides an adequate reduction of the mandibular
length and this avoids the necessity for exposing the
inferior dental canal and bundle. A buccal mucope­
riosteal flap is raised to allow full exposure of the
body of the mandible from the alveolar crest to the
inferior border at the preplanned osteotomy site.
The adjacent lingual mucoperiosteum is raised and
protected with a periosteal elevator without reflec­
tion of a full mucoperiosteal flap.
A surgical fissure bur is used to cut two vertical
osteotomy lines, which represent the width of the
bone segment to be removed and a horizontal line
2–3mm above the level of the inferior dental nerve
(Figure 7.15a). Guided by the preoperative radio­
graph the bone above the inferior dental nerve is cut
and removed (Figure 7.15b). The cuts are limited to
occur. Reducing the length in IMF for three weeks has
been considered by some surgeons.
7.5.3  Complications
The most common operative complication of the
VSSO is the poor direction of the saw position and
fracture of the proximal segment across the posterior
border of the mandible. This should be avoided by
full exposure of the lateral surface of the ramus of the
mandible, the use of the designated retractors for this
procedure and bone cutting using the correct right
angle surgical saw. Plating of the fractured segment
may be difficult if it is high and near the condyle. In
this case intermaxillary fixation should be applied
and the case is treated as a sub-condylar osteotomy/
fracture. Fracture of the posterior border near to the
inferior border of the mandible may require internal
plate fixation.
Displacement of the condylar segment medially
and extensive bleeding have been reported among
the operative complications of VSSO. The condylar
segment has to be retrieved and positioned laterally
to allow the posterior shift of the mandible. Haemos­
tasis has to be achieved and it may be easier to control
the bleeding once the osteotomy is completed and
the proximal segment is mobilised laterally. The use
of mini drains is recommended for the first 24 hours
following surgery.
The most common immediate postoperative com­
plication following VSSO is slight inferior displace­
ment of the condylar segment which may require
further surgical intervention to trim its inferior
end; this is easily prevented by checking this prior
to closure and improving of its adaptation to the
mandible using an inter osseous wire or a heavy non-
resorbable stitch. Rarely a second surgical intervention
is required to adjust the condylar segment; remodel­
ling at the lower border will occur with time.
Relapse is the most common long term complica­
tion due to bilateral inferior sagging of the condylar
segment per-operatively which would manifest as an
anterior open bite and reduction of the achieved
overjet. This can be avoided with proper seating of
the condylar segment during surgery and it may be
necessary to trim the ramus to allow this to happen.
Adequate reflection of the attachment of the medial
pterygoid muscle from the condylar segment should
allow an unobstructed posterior shift of the
mandible.
Alteration of sensation of the lower lip has been
documented following VSSO. This can be easily
avoided with careful planning and maintaining the
vertical bone cut posterior to the anti-lingula notch­

Basic orthognathic surgical procedures
131
zontal piece of bone lingual to the inferior dental
nerve to protect it while the other side is prepared,
removing the former at the end.
The method has also been used for lengthening the
body of a hypoplastic mandible. In these cases a step
shaped cortical bone cut is performed to allow the
insertion of bone graft in the space created by moving
the distal segment forward and this is done anterior
to the neurovascular bundle to avoid stretching of
the inferior dental nerve, two mini plates are used for
fixation.
7.6.3  Complications
The complication that may be associated with this
technique is the damage to the inferior dental nerve
which is readily avoidable with appropriate planning
and careful execution of the surgical technique.
Figure 7.15a  Two vertical bone cuts which represent the
width of the bone segment to be removed and a
horizontal line 2–3 mm above the level of the inferior
dental nerve.
Figure 7.15b  Removal of the bone above the inferior
dental nerve is cut and removed.
Figure 7.15c  Removal of the bone above and below the
inferior dental nerve.
Figure 7.15d  Fixation of the osteotomy segments in their
final position using two plates.
the buccal cortex, the inferior border is kept intact at
this stage. Removal of the buccal bone segment with
its underlying cancellous bone around the mandibu­
lar canal will expose the inferior dental nerve and the
lingual plate of bone. The nerve is carefully dissected
off the lingual bone using blunt plastic instruments.
This provides direct access to the lingual plate of the
body of the mandible. The lingual bone is cut using
a surgical fissure bur in two segments, one above and
one below the inferior dental nerve (Figure 7.15c).
The two segments are approximated and fixed in
their final position using two plates (Figure 7.15d),
one above and one below the inferior dental nerve.
A window is usually cut on the buccal surface of the
proximal segment or cancellous bone is removed to
allow careful seating of the inferior dental nerve. It
is helpful on the first side cut to leave a small hori­

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Handbook of Orthognathic Treatment
Figure 7.16a  Profile and frontal photographs of one of the cases demonstrating the changes in facial appearance
following inverted L osteotomy and allowing protection of the inferior alveolar nerve.
Figure 7.16b  The horizontal osteotomy through both
lingual and buccal cortices of the ramus just above the
level of lingual using surgical saw.
from the posterior end of the horizontal cut to the
angle of the mandible (Figure 7.16c). A right angle
oscillating surgical saw can be used to achieve this
vertical cut via an intra-oral approach. This cut also
includes both the buccal and lingual cortices of the
ramus of the mandible. The distal segment is mobi­
lised both antero-posteriorly and vertically to achieve
the required lengthening of the vertical height and
an advancement of the ramus of the mandible. The
proximal segment is kept in its presurgical position.
The created gap with the shape of an inverted L is
grafted with cortical autogenous iliac bone. Two
plates, one above and one below the inferior dental
nerve may be used for the fixation of the mandibular
ramus (Figure 7.16d). The access to apply these plates
is usually via a combined intraoral and extra oral
7.7  Inverted L ramus osteotomy
(Figure 7.16)
This is the most reliable method for advancement
and lengthening the vertical height of the ramus of
the mandible. The method is also used when signifi­
cant mandibular advancement is required beyond
the scope of sagittal split mandibular advancement.
A bone graft is required and an extra-oral incision
may be necessary.
7.7.1  Indications
1. Anterior open bite due to severe reduction of pos­
terior vertical height and deficiency of the vertical
length of the ramus of the mandible.
2. Correction of asymmetric mandibular deficiency
with or without ramus surgery on the opposite
side.
3. Significant mandibular advancement beyond the
scope of a sagittal split ramus osteotomy (Figure
7.16a).
7.7.2  Procedure
Most of the osteotomy cuts can be carried out via an
intra oral approach. A standard mucoperisoteal flap
is reflected to expose the buccal surface of the ramus
of the mandible. In addition, a lingual mucoperio­
steal flap is reflected to expose the lingula and allow
protection of the inferior alveolar nerve. The first
horizontal osteotomy cut is carried out using a fissure
bur or a surgical saw (Figure 7.16b) through both
lingual and buccal cortices of the ramus just above
the level of lingula. The posterior border of the man­
dible is kept intact. The vertical bone cut is usually
undertaken via an extra-oral approach and extends

Basic orthognathic surgical procedures
133
Figure 7.16c  Extra-oral approach to undertake the
vertical bone cut is usually from the posterior end of the
horizontal cut to the angle of the mandible to facilitate
fixation.
Figure 7.16d  The application of two plates for fixation of an inverted L osteotomy.
approached. Trans-buccal approach may facilitate the
insertion of bicortical screws.
The extra-oral access is usually achieved via a sub­
mandibular approach to keep the incision line in a
skin crease below the inferior border of the ramus of
the mandible after lengthening.
7.7.3  Complications
Occasionally with this technique there is damage to
the marginal mandibular branch of the facial nerve.
This complication can be minimised with careful
surgical technique. The other complication is the
scarring due to the extra oral skin incision, this
could be avoided if an intra-oral approach is adopted
which may not be easy for complex mandibular
deformities.
7.8  Anterior mandibular osteotomies
7.8.1  Lower anterior segmental osteotomy
The procedure is designed to move the lower anterior
dento-alveolar segment in any direction while main­
taining the integrity of the inferior border of the
mandible.
Indications
1. Correction of a steep curve of Spee to facilitate the
antero-posterior
surgical
movement
of
the
mandible.
2. Excessive or deficient lower incisor show at rest
and with a maximum smile.
3. Decompensation where orthodontic correction of
the axial inclination of the lower incisors is not
possible.
Procedure
A labial mucoperiosteal flap is raised to expose the
labial surface of the chin and the vertical osteotomy
site which is usually in the first premolar region. This
is achieved by a curved incision of the mucosal
surface of the inner surface of the lower lip that
extends to the site of the planned vertical bone cut.
This is connected with a distal releasing incision
above the level of the mental foramen posterior to
the site of the vertical bone cut. The anterior labial
incision depends on cutting the periosteum covering
the chin. The dissection posteriorly is carried out
after identifying and protecting the mental nerve and
its branches. This allows the bone above and below
the nerve to be exposed with minimal stretching of
the mental nerve. The final incision is along the
gingival sulcus of the first premolar and the adjacent
teeth to facilitate the tunnelling of the attached

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Handbook of Orthognathic Treatment
gingivae at the planned vertical osteotomy site
(Figure 7.17a).
The bone cut is achieved using a surgical fissure bur
or a fine saw, it starts at the vertical osteotomy site
to involve bone of the buccal and lingual cortices
with full protection of the lingual mucoperiosteum
using a Howarth periosteal elevator. Extraction of the
first premolar may be considered at this stage to guide
the vertical bone cut. The horizontal cut is achieved
using a reciprocating surgical saw about 5mm below
the apices of the teeth and extended to connect with
the two vertical bone cuts. The depth of the horizon­
tal bone cut should include the lingual cortex of
the chin.
The segment can be mobilised using a Smith
spreader and this is facilitated with spatula oste­
otomes. The mobilised segment is pedicled on the
attached gingiva labially and on the mucoperiosteum
and genial muscles lingually. Guided by an occlusal
Figure 7.17c  Radiographic picture of lower anterior
segmental osteotomy.
Figure 7.17d  Radiographic picture of lower anterior
segmental osteotomy and genioplasty.
Figure 7.17b  Anterior segmental osteotomy and the use
of two plates on each side for fixation.
wafer and temporary intermaxillary fixation the
segment is seated into its final position before fixa­
tion with mini plates (Figures 7.17b, 7.17c). The
wound is closed in layers starting with the mentalis
stitching to the mucoperiosteal flap using 4(0) Vicryle
suture.
The procedure can be combined with a genioplasty
to allow independent adjustment of the chin and
maintaining the integrity of the mandible as one
piece (Figure 7.17d).
7.8.2  Anterior mandibulotomy (Figures
7.18a, 7.18b)
The procedure allows the surgical movement of the
lower anterior segment of the mandible including the
inferior border.
Indications
It has a similar scope of application to the anterior
segmental procedure but it also allows simultaneous
adjustment of the inferior border of the mandible. It
is indicated where surgical movement of the anterior
dento-alveolar segment of the mandible is required
in cases complicated by deficiency of the lower ante­
rior vertical height of the mandible that prevents
adequate segmental movement without damage to
the apices of the teeth.
Figure 7.17a  Lower anterior subapical osteotomy.

Basic orthognathic surgical procedures
135
Figure 7.18a  Mucoperiosteal flap for anterior
mandibulotomy.
Figure 7.18b  Protection of the lingual mucoperiosteum
and buccal bone cuts anterior to the mental nerve.
Figure 7.18c  Completed anterior mandibulotomy leaving
an intact lingual mucoperiosteum.
Figure 7.18d  Fixation of the anterior mandibulotomy
using two plates, one above and one below the mental
nerve.
Procedure
A buccal mucoperiosteal flap is raised starting from
the gingival crest at the edentulous area, connects
anteriorly with a semi-vertical incision which extends
to the muco-labilal fold and connects distally with a
curved posterior incision across the attached ginigiva
(Figure 7.18a). This allows the full exposure of the
osteotomy site and direct observation of the mental
nerve. The lingual mucoperiosteum is protected
using Howarth’s periosteal elevator. Using a fissure
surgical bur or a surgical micro saw two vertical bony
cuts are made on the buccal cortex to allow the
planned posterior movement of the anterior man­
dibular segment (Figure 7.18b). The osteotomy is
completed after removal of the lingual cortex using
a surgical fissure bur or by spatula osteotome, it is
essential to maintain the lingual mucoperiosteum
intact during this procedure (Figure 7.18c). Adequate
fixation is achieved using two plates, one above and
one below the mental nerve (Figures 7.18d, 7.18e).
The procedure can be combined with a genioplasty
(Figure 7.18f) to allow a four-part mandibulo-
genioplasty where the lower genial segment is moved
Figure 7.18e  Radiograpic appearance and a diagram
showing anterior mandibulotomy.

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Handbook of Orthognathic Treatment
mally performed under general anaesthesia, however,
genioplasties have been carried out successfully under
local anaesthesia and sedation in some countries.
7.9.1  Indications
1. Correction of retrogenia.
2. Correction of progenia.
3. Vertical reduction in cases of increased lower ante­
rior facial height.
4. Vertical augmentation in cases of anterior defi­
cient vertical height of the mandible.
5. Correction of an asymmetric chin.
6. Simultaneously with maxillary or mandibular
osteotomies which bring the chin into more
favourable position.
7.9.2  Procedure
Exposure of the chin is achieved via an intra-oral
approach after reflecting a labial mucoperiosteal flap
extending from the right to the left first premolars
(Figure 7.19a). The labial mucosa is cut first followed
by the mentalis muscle which should be carefully
sectioned and resutured with the flap at the end of
the procedure. The mental nerves are identified and
protected. Vertical and horizontal marks on the labial
surface of the bony chin are achieved using a narrow
fissure bur to guide the surgical movement of the
genial segment. The osteotomy is usually undertaken
using a straight reciprocating surgical saw. This allows
cutting of both the labial and lingual cortices with
minimal damage to the bony surfaces. Based on the
desired movement the genial segment can be moved
forward, backward, and rotated in a right or left
direction to correct mediolateral asymmetry (Figure
7.19b). Vertical reduction genioplasty is achieved by
Figure 7.19a  Exposure of the chin after reflecting a labial
mucoperiosteal flap extending from the right to the left
first premolars.
Figure 7.18f  Radiographic picture of anterior
mandibuloplasty and genioplasty which splits the
mandible into four segments.
in a direction different from that of the dento-alveolar
anterior segment. Fixation of the four segments is
complex, the use of an occlusal wafer and temporary
intermaxillary fixation is essential to achieve the
required relationship of the incisal, right posterior
and left posterior mandibular segments. Mini plates
are required for the fixation of the anterior dento-
alveolar segment with the body of the mandible
above the mental nerves with similar plating of the
genial segment to the inferior body of the mandible
below the mental nerves.
7.8.3  Complications
1. Damage to mental nerve
This should be avoided by careful exploration and
protection of the nerves during surgery. Fixation
plates and fixation screws should be applied away
from the mental foramen and the course of the infe­
rior dental nerve.
2. Bone exposure
Careful reflection of the mucoperiosteum and avoid­
ing the damage of the attached gingival would mini­
mise this risk. Careful multi-layer stitching of the
muscle and mucoperiosteum would facilitate healing
and maintain the blood supply to the osteotomy
segments.
3. Loss of the lingual blood supply to the segment
can lead to devitalisation of the teeth and affected
bone segment with its necrosis which would cause
severe deformity. Great care must be taken with
movements of the segments and to ensure the muco­
periosteal flaps are not damaged.
7.9  Genioplasty
This is the most versatile surgical technique for cor­
rection of chin deformities. The procedure is nor­