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Three-dimensional quantification of post-surgical condylar displacement

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Three-dimensional quantification of post-surgical condylar displacement

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Three – Dimensional Quantification
Of Post-Surgical
Condylar Displacement

by
Paula Zabalegui
May 2016

A Thesis Presented to the Faculty Of The USC Graduate School
University Of Southern California in Partial Fulfillment of the Requirements for the
Degree Master Of Science (Craniofacial Biology)

1
Acknowledgements
This project would have not been possible without Dr. Dan Grauer’s guidance and
mentoring.
Special thanks to Dr. Michael Gunson who provided the data for our study.

I would also like to thank my family for all the support and encouragement throughout
this journey. Mom, Dad, Gonzaga, I love you.

2
Table of Contents

I. List of Figures ………………………………………………………………………. 3
II. List of Tables ……………………………………………………………………….. 4
III. Abstract ……………………………………………………………………………. 5
IV. Introduction ……………………………………………………………………..…. 6
V. Literature Review ………………………………………………....………..…... 6
a. Digital Imaging in Orthodontics ……………………………….…... 7
b. CBCT in Orthodontics …………………………………………………..… 9
c. CBCT in Orthognathic Surgery ……………………………..….……….. 17
d. Condyle Position and Changes After Orthognathic Surgery…… 20
e. Methods Of Assessing Condylar Position Changes …………...… 23
f. Condylar Resorption And Surgical Stability …………………...…. 31
VI. Materials and Methods ……………………………………………..………… 35
a. Sample …………………….………………………………………,…………. 35
b. Method…………………….…………………………………………..…..…. 36
VII. Results ………………………………………………………………………..……. 42
VIII. Discussion…………………..………………………………………..…………… 51
IX. Conclusion……………………………………………………………………....…57
X. Appendix……………………………………………………….………….……… 58
XI. References ……………………………………………………..………………… 75

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I. LIST OF FIGURES
Fig 1: Diagram showing the basic 3-stage concept of a CBCT scan.
Fig 2: Protocol for the selection of appropriate CBCT FOV.
Fig 3: Virtual surgical treatment planning.
Fig 4: Basilar film to determine the angle between the long axis of each condyle and
midsagittal plane. (Will et al. 1984)
Fig 5: Superimpositions of condylar contours (Will et al. in 1984)
Fig 6: Pullinger and Hollender method.
Fig 7: Axial slide as reference image in left and right TM. (Alder et al 1999)
Fig 8: Sagittal section through mid-condyle and coronoid process. (Alder et al 1999)
Fig 9: Two-dimensional reformat perpendicular to condyle long axis. (Alder et al 1999)
Fig 10: CMF application allows the identification of the greatest displacement of a specific
anatomic region.
Fig 11: Isolation of the region of interest for segmentation.
Fig 12: Segmentation.
Fig 13: Superimposition of pre and post condyles.
Fig 14: True displacement of the condyles pre-surgery and post-surgery.
Fig 15-18: Condylar resorption present prior to surgery and abnormal anatomy.
Fig 19: Dawson Technique for condylar seating.
Fig 20: Dawson Technique during surgery.
Fig 21: shows rotation on Z plane. Blue is pre surgical and red post-surgical.
Fig 22: shows medial rotation of the left condyle.

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II. LIST OF TABLES
Table 1. Effective radiation dose expressed in microSieverts and produced by cone-beam
computed tomography at different resolutions and FOV in comparison with multi-slice CT
and conventional radiograph.
Table 2. Effective dose in Sv for the different FOV and CBCT devices used in
orthodontics compared to MSCT, rotational panoramic and cephalometric radiography.
Table 3: Results.
Table 4: Range, minimum, maximum, mean and standard deviation.
Table 5: Mean and S.D on each plane for right and left condyles.
Table 6: Mean and S.D on each plane by gender.
Table 7: significance values for all six variables
Table 8: Significance values comparing right and left sides

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III. ABSTRACT
Background: Condylar displacement following orthognathic surgery has been related to
post-surgical relapse. Although postoperative changes in condylar position have been
reported in previous studies, no study has precisely quantified these variations in three
dimensions (3D). The development of cone beam computed tomography (CBCT) has
enabled the accurate measurement of changes in condylar position in three planes of
space (x, y, z).
Purpose: To quantify, in 3D, the amount and direction of condylar displacement relative
to the glenoid fossa after bi-maxillary surgery.
Materials and Methods: The sample consisted of 17 patients undergoing orthognathic
surgery treated consecutively by one surgeon. The pre-surgical and 2-week post-surgical
CBCT DICOM files were collected for each patient. The regions of interest in the
temporomandibular joint complex were segmented and the pre- and post surgical
condyles were superimposed using the glenoid fossa as the reference structure.
Condylar translation and rotation were compared before and after surgery for each
patient in three planes of space.
Results: The average condylar displacement was 0.78 mm on x plane, -3.80 mm on y and
0.14 mm on z plane. As for rotation, the average movement was 0.06 º on x plane, 0.30º
on y and -0.27 on z. The only statistically significant movements were translation on Y
plane and rotation on Z plane.
Conclusion: Minimal changes in condyle position do occur immediately after bi-maxillary
surgery and it is possible to accurately assess the amount and direction of this
displacement in 3D.

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IV. INTRODUCTION
The importance of determining the change in position of the condyle after orthognathic
surgery has been a topic of interest because it may lead to postoperative complications
such as idiopathic condylar resorption, functional disorder, and post-operative relapse.
Postoperative changes in condylar position have in fact been reported in previous studies,
however, no study has precisely quantified these variations in three dimensions (3D). The
development of cone beam computed tomography (CBCT) enables the accurate
measurement of changes in condylar position in three planes of space (x, y, z), as well as
changes in rotation, allowing the doctor to evaluate both rotational and translational
changes.
The purpose of this study is to establish a method to measure, in three dimensions,
translation and rotation of the condyle 2 weeks after orthognathic surgery relative to the
glenoid fossa and temporal bone.

V. LITERATURE REVIEW
Today’s advances in technology reveal a new dimension when treatment planning and
analyzing changes that occur with growth and development. It is key for the
contemporary practitioner to embrace this third dimension and improve patient
treatment quality and outcomes.

7
A. Digital Imaging In Orthodontics
Currently, in the field of orthodontics, two-dimensional (2D) digital imaging is the system
of choice. The diagnostic records for the orthodontic practice recommended by the ADA
and AAO are panoramic and cephalometric radiographs and intraoral and extra oral
photographs.
These 2D digital radiographs are being used to assess the skeletal and dental
relationships throughout the different phases of orthodontic treatment: from diagnosis,
treatment planning and evaluation of growth and development, to assessment of
treatment progress and outcomes (American Academy of Oral and Maxillofacial
Radiology 2013).
Linear measurements that consist of lines angles and ratios are traced on these 2D planar
radiographs and provide a general description of the patient’s skeletal and dental
malocclusion as well as its deviation from the norm. However, these measurements are
derived from the superimposition of 3-dimensional (3D) structures in 2 planes of space,
adding a lot of limitations to our diagnosis and evaluation of treatment outcomes and
stability since a lot of information is inherently lost. Other limitations of 2D radiographic
imaging include magnification, geometric and projective displacements and rotational
errors (Kapila S. 2011). This is one of the reasons why relapse and unfavorable responses
to orthodontic therapy still remain poorly understood. Multiple radiographic projections
are taken in attempt to display complex anatomic relationships and surrounding
structures, like the condyles, but interpreting these is challenging (American Academy of
Oral and Maxillofacial Radiology 2013; Kapila S. 2011). Because most dentofacial
problems involve all 3 dimensions, the development of cone beam computed
tomography (CBCT) in the last 15 years has become of great interest in the different
dental specialties.
CBCT scanners capture images of the desired region of interest (ROI) and provide an
accurate 3D representation of craniofacial structures, teeth and roots, with no
superimpositions (Kapila S. 2011).

8
This three dimensional treatment planning technology uses a cone-shaped X-ray beam
and a detector that revolves around the patient to capture a sequence of 2D images in the
3 planes of space, which are then converted into a 3D image using a computer software
(Scarfe et al 2006). There are 3 basic stages involved in this process: the first stage is the
X-ray beam orbiting around the patient, obtaining the data in a cylindrical volume. The
second stage is the primary reconstruction- the computer divides the cylinder into tiny
cubes or voxels. Stage three is the multiplanar reconstruction in the sagittal, coronal and
axial planes. (Fig 1)

Fig 1. Diagram showing the basic 3-stage concept of a CBCT scan.

There is no doubt that CBCT has some advantages over conventional imaging. It offers a
3D image with no superimpositions or magnification which makes diagnosis and
treatment planning much more accurate. Also it has much better image resolution than
conventional imaging. Voxel size, which determines image resolution, ranges from 0.076

9
to 0.4mm, although at 0.3mm and beyond, the reconstruction accuracy and
reproducibility decreases significantly (De Maret et al. 2012). Another benefit is scanning
time. Because it acquires all images in a single rotation, scan time only takes 10-70
seconds, much faster than conventional CT. When compared to conventional
radiographs, such as a panoramic radiograph, it has been found to be more accurate to
the real size object and has shown to have a lower level of metal artifacts, which allows a
better visualization of teeth and anatomical structures (Scarfe et al 2006; De Vos et al
2009).
For these reasons, the use of CBCT is supported by the American Dental Association
(ADA), American Academy of Oral and Maxillofacial Radiology (AAOMR) and American
Association of Orthodontists (AAO) in some cases, as long as it is offering information
that cannot be obtained with lower-dose dental radiographies (American Academy of
Oral and Maxillofacial Radiology 2013; American Dental Association Council on Scientific
Affairs 2012; Kapila S. 2011).
Currently in the field of orthodontics, CBCT has not been linked to a clear diagnosis
classification (Grauer et al. 2009). However, there are some indicators of when using 3D
imaging is a benefit over 2D.

B. CBCT In Orthodontics
Accurate imaging is essential in the orthodontic field for an appropriate diagnosis and
treatment planning as well as a good assessment of treatment progress and outcome.
This is why there has been a dramatic increase in the use of CBCT.
Despite the number of publications on the use of this technology, few authors have
presented high levels of evidence or have measured the impact of CBCT in altering
treatment planning decisions in orthodontics (American Academy of Oral and

10
Maxillofacial Radiology 2013). The AAO recognizes that only in some clinical cases this
digital imaging may be of value, and is not required routinely for orthodontic care.
Nevertheless, a hierarchy of indicators for CBCT imaging is emerging. Since its use has
not yet been supported by rigorous scientific studies, its utilization is being justified by
published case reports showing its contribution to diagnosis, treatment planning and
monitoring a specific type of case (Kapila S. 2011).
CBCT has demonstrated clinical efficacy in treatment planning impacted and unerupted
teeth; monitoring root resorption; obtaining accurate measurements of airway volume
and skeletal asymmetries; determining the skeletal jaw relationship and assessing
growth; and viewing the condyle position and the temporomandibular joint (TMJ) in three
dimensions. It can also be applied to evaluate other supplementary findings like
periodontal issues, post treatment TMD and placement of temporary skeletal anchorage
devices (Machado 2015; American Academy of Oral and Maxillofacial Radiology 2013;
Kapila S. 2011).
As for cephalometric radiographs, the question arises whether CBCT can replace the
conventional set of radiographs. This recent technology does provide the means to
generate distortion-free images replicating the lateral cephalometric radiograph and
panoramic radiograph. In order to be able to compare the new modalities with our
current databases, algorithms have been created to extract information from the CBCT
image and to simulate a conventional lateral cephalogram, P-A cephalogram, and
panoramic projection. Since sequential cephalograms provide an easy clinical method for
assessing growth and treatment changes 3-D registration and superimposition of CBCT
data is being developed (Grauer et al 2010). Grauer et al. evaluated differences in
landmark position between CBCT–generated cephalograms and conventional digital
cephalograms and showed there were no systematic differences between modalities in
the position of most landmarks. However, CBCT scans should not replace all headfilms
indiscriminately since it would be costly and unethical. Nijkamp et al, demonstrated that
important decisions regarding treatment rarely were influenced by cephalometric
parameters. Therefore routine use of CBCT to obtain cephalometric analyses may be

11
superfluous (Kapila S. 2011; Nijkamp et al 2008). In case of craniofacial anomalies or in
need of a specific analysis of TMJ a CBCT scan may replace conventional radiographs
(Kapila S. 2011; Grauer et al 2010).
Currently, cases where CBCT is not indicated are those where it will not provide valuable
new information, for example, constructing custom fixed appliances and / or fabricating
custom wires. There are non-radiologic digital imaging technologies available that are
adequate alternatives. Another case would be root positioning. There is no data available
that suggests that this enhanced information results in better or more efficient treatment
(Kapila S. 2011; Halazonetis 2012). Nevertheless, this is expected to change in the near
future with the advent of new technologies involving appliance manufacturing.
In any case, the decision to take a CBCT should be made after the clinician has evaluated
the patient history, chief complaint and performed a clinical examination. This careful
selection will ensure maximum benefit balanced against radiation risks (American
Academy of Oral and Maxillofacial Radiology 2013; Kapila S. 2011). CBCT imaging uses
ionizing radiation, therefore clinical benefits should be balanced against radiations risks
and this type of imaging will only be used when the clinical question cannot be answered
adequately by a lower-dose conventional radiograph or non-ionizing imaging modality.
On the contrary, Ii the clinical examination indicates that a CBCT study is indicated, avoid
taking additional conventional 2D radiographs (American Academy of Oral and
Maxillofacial Radiology 2013;).
Although doses from CBCT are relatively low, patient dose remains a concern in dental
diagnostic imaging. To decide which is the most appropriate CBCT imaging in each
circumstance, there are recommendations for specific imaging selections. Several factors
should be taken into account when taking a CBCT. Reducing the size of the irradiated
area Field of View (FOV) and modifying settings such as peak kilovoltage (kVp) and
milliampere (mA) can help reduce the effective radiation dose.
In order to choose the appropriate FOV for the CBCT, treatment difficulty, dental
structure anomalies and/ or skeletal discrepancies, will be taken into account, knowing

12
that the orthodontist that orders or performs the CBCT will be responsible for
interpreting the entire image volume (De Vos et al 2009):
- A small FOV is limited to a few teeth, a quadrant. It is normally < 10cm.
- A medium FOV includes the dentition of at least one arch, or even both dental
arches. It varies from 10-15cm
- A Large FOV includes the TMJ articulations, anatomic landmarks necessary for
cephalometrics and airway. Its cylinder height is >15cm.
The small FOV CBCT allows minimizing certain limitations we have with 2D radiographs.
In case of impacted teeth, multiple 2D radiographs would be needed to locate the tooth
and these images can be enlarged, distorted or overlapped, reducing the image quality
and diagnostic accuracy. One single CBCT is enough to exactly locate the impacted tooth,
know its size and shape without distortion, and get a more detailed view of the bone and
structures adjacent to it.

The large field view can be very variable. It has not been recommended as a routine
orthodontic radiography, since the radiation dosage of a CBCT can sometimes double
that of a panoramic and cephalogram. However, there are many settings that can be
adjusted to lower the radiation dose to that of the medium or small FOV. Also, when
diagnosing and treating skeletal asymmetries and congenital malformations, this full
head 3-dimensional x-ray will be a more accurate tool since it allows seeing rotational
movement of all craniofacial structures (Tarajima et al. 2009; Haney et al. 2010;
Cevidanes et al. 2006). Figure 2 describes the FOV recommended for each case where
CBCT is indicated.

13

Fig 2. Protocol for the selection of appropriate CBCT FOV (Kapila S. 2011)

When it comes to radiation dose and exposure, many factors like kVp, mAs, voxel size,
tissues scanned, scanning time, degree of rotation, collimators and filters used are part of
the equation. Different CBCT units have different radiation dose per scan and modifying
settings such as peak kilovoltage (kVp) and milliampere (mA) can help reduce the
effective radiation dose. Another way to reduce radiation dose would be using a scanner
that rotates only 190º-210º instead if a full 360º rotations, since it will reduce scan time
and thereby, radiation dose (Machado 2015; Scarfe et al 2006; American Academy of Oral
and Maxillofacial Radiology 2013; American Dental Association Council on Scientific
Affairs 2012; Kapila S. 2011; Ludlow and Walker 2006).
The effective radiation dose for a patient from a CBCT machine can range from 18
microsievert (μSv) to 1073 μSv (8) depending on the field of view (FOV). The reported
dose for a full mouth series is 150 μSv (6) and 50 μSv for a panoramic radiograph (Daniela
G et al. 2014; Kiefer H et al 2004). These data are summarized in Table 1.

14

Table 1. Effective radiation dose (EICRP 2007) expressed in microSieverts (mSv) and produced by cone-beam
computed tomography at different resolutions and FOV in comparison with multi-slice CT and conventional
radiograph. (Daniela G et al. 2014)

Table 2 shows the effective doses in microSieverts for the different FOV and CBCT
devices used in orthodontics, compared to multi-slice computed tomography (MSCT),
rotational panoramic and cephalometric radiography (American Academy of Oral and
Maxillofacial Radiology 2013). CBCT dose varies substantially depending on the device,
FOV and selected technique factors. There is a major inconsistency in the reported CBCT
properties and settings so there is a lack of evidence based data on the radiation dose for
this type of imaging (De Vos et al 2009).
Type of radiograph Dose (μSv)
CBCT of face and cranium (FOV > 15 cm) 52 to 1073
CBCT of face (FOV 10 - 15 cm) 61 to 603
CBCT of the jaws (FOV < 10 cm) 18 to 333
Multi-slice CT 426 to 1160
Panoramic radiograph 6 to 50
Cephalogram 2 to 10
Full mouth series 150

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All in all, CBCT effective dose can be several to many times higher than conventional
panoramic imaging but many times lower than reported doses for conventional CT
(Ludlow et al 2006). Therefore routine use of CBCT for orthodontics may be superfluous
but in case of craniofacial anomalies, or in need of a specific analysis of TMJ a CBCT scan
may replace conventional CT (Kapila S. 2011).

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Table 2: Effective dose in Sv for the different FOV and CBCT devices used in orthodontics compared to MSCT,
rotational panoramic and cephalometric radiography.

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C. CBCT In Orthognathic Surgery
Up to the 21
st
century, cephalometric analysis on a 2D lateral cephalogram has been the
method used to diagnose and treatment plan patients with severe malocclusions that
require orthognathic surgery.
The human skull is very complex structurally, which makes radiographic interpretations
very challenging, especially using conventional lateral cephalographs because they suffer
the well-known problems that arise when a 3D object is projected onto a 2D plane:
magnification, superimpositions, distortions and inconsistency in head position during
imaging. In addition, the third dimension in the coronal plane is largely overlooked and
the posterior-anterior (PA) cephalogram used to compensate this is not very precise due
to errors in head position (pitch, yaw and roll), which lead to an inaccurate diagnosis
(Motta et al. 2010, Mah et al. 2004, Kapila S. 2011).

Over the past decades, orthognathic cases have been planned and prepared through a
very labor-intensive and time-consuming method. Model surgery and virtual 2D
cephalometric surgery are performed by the surgeon to plan the surgical correction. In an
asymmetric face, many details and specifics cannot be captured or measured adding
additional problems (Kapila S. 2011).

As opposed to 2D radiographs, CBCT combined with computer-aided surgical simulation
(CASS) offers many enhancements, optimizing diagnosis and treatment objectives. It
improves the analysis of craniofacial deformities, facilitates surgical planning (Fig 3.),
minimizes damages to structures such as nerves, aids planning for interferences around
the proximal segments and helps fabricate customized fixation devices for orthognathic
surgery. In addition, pre- and post- surgical superimpositions of CBCT scans can be
performed to evaluate treatment outcome and its precision achieving pre-operative

18
plans, as well as to document any condylar changes (Kapila S. 2011; American Academy
of Oral and Maxillofacial Radiology 2013; Mah et al. 2004).
CBCT imaging is useful particularly in the diagnosis and treatment planning of
asymmetries, since discrepancies often manifest in all three planes of space. It facilitates
identifying and quantifying asymmetries in pitch, roll and yaw of the skeletal bases. Size
and shape of the maxilla and / or the mandible may be altered, and anatomic structures
like the condyle, condylar neck, ramus and body of the mandible can be affected. A 3
dimensional image allows the surgeon to see these with minimal projection error,
allowing for a more realistic examination. Another important consideration is the fact
that the pre-surgical centric relation may be visualized and post-operative alterations in
condylar anatomy and position as well as errors in achieving centric relation after surgery
may be evaluated. There are several computer softwares that will allow pre and post-
surgical superimpositions to document any condylar changes (Swennen et al, 2009;
Kapila S. 2011; American Academy of Oral and Maxillofacial Radiology 2013; Bholsithi et
al, 2009; van Vlijmen et al., 2012; Zamora et al, 2012; Terajima et al. 2009; Haney et al.
2007; Cevidanes et al. 2006).

Fig 3. Virtual surgical treatment planning. (Kapila S. 2011)

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As for treatment planning orthognathic surgeries, surgical simulations have always been
used and now CBCT allows for this process to be more accurate, cost effective and more
efficient, achieving more consistent surgical outcomes when compared to the use of 2D
imaging. (Hsu et al. 2013). For this reason, CBCT is currently an ideal option for planning
orthognathic surgeries.
When it comes to long-term follow-up of surgical cases the orthodontist and surgeon
have relied on a series of 2D cephalometric radiographic superimpositions. However, this
2D view is a less accurate method of superimposition because it is a representation of a
3D structure. The introduction of 3D registration, allows the superimposition of models
and craniofacial CBCT scans to quantify the amount of anteroposterior, transverse, and
vertical movements of craniofacial structures involved in orthognathic surgery and to
study the position, movement, stability, and remodeling of the condyles before and after
orthognathic surgery (Motta et al. 2010; Terajima et al. 2009; Haney et al. 2007;
Cevidanes et al. 2006; Hino et al. 2014).
The registration process and semitransparent superimpositions of 3D images have played
a great role in the analysis of short-term and long-term orthognathic surgical stability,
and have been a great instrument for clinical, scientific, and educational orthodontics and
surgical application (Motta et al. 2010).
Recent 3-D analysis of the distal segments of the mandible after orthognathic surgery
have greatly contributed to the understanding of the anterior, posterior, medial, and
lateral movements of the condyle within the TMJ (Cevidanes et al 2005). The location,
magnitude, and direction of mandibular rotations during surgery can be clearly visualized
by 3-D model superimpositions and surface distance calculations. Furthermore, 3-D
imaging has allowed for the quantification of vertical transverse and anteroposterior
ramus rotation for mandibular surgery (De Clerck 2012, Cevidanes et al. 2005).

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D. Condyle Position And Changes After Orthognathic Surgery
The relationship between the mandibular condyle and glenoid fossa has long been
debated and still remains one of the most controversial issues.
CT scans have traditionally been used to attempt visualizing the condyle and its relation
to the fossa and different methods may be used to produce and interpret the images
obtained (Utt TW. et al, 1995). However, imaging of the temporomandibular joint (TMJ) is
not a routine record for asymptomatic orthodontic patients. A panoramic radiograph is
used to view the condyles with subsequent specific imaging ordered for TMJ if bony
changes are noted. When a CBCT volume is used for orthodontic assessment and
orthognathic surgery, it generally includes the right and left temporomandibular joints
making them available for routine review. A 3D image of the condyles with real size and
form allows for a more realistic examination and a more accurate evaluation (Motta et al.
2010; Larson BE 2012).
3D analysis of the distal segments of the mandible after orthognathic surgery has greatly
contributed to the understanding of the anterior, posterior, medial, and lateral
movements of the condyle within the TMJ. The location, magnitude, and direction of
mandibular and condylar rotations during surgery can be clearly visualized by 3-
dimensional scan superimpositions. To analyze these changes at different time points,
Cevidanes et al found that the structures along the cranial base for adults and the anterior
cranial fossa for growing children were stable and reliable to use as reference structures.
(Cevidanes et al. 2006; Cevidanes et al. 2009; Motta et al. 2010).
Condylar position is known to be affected postoperatively by factors such as the
rotational movement of the distal segment, muscle equilibrium, fixation method, and
surgeon’s experience. Because sagittal split ramus osteotomy of the mandible is known
to affect the condylar positioning postoperatively, it is important to accurately assess the
position of the condyles to maximize the stability of the surgery and predict treatment
(Kim et al. 2012). These small changes in the condylar position can be accommodated by
the physiologic adaptation leading to later skeletal relapse or condylar remodeling (Kim

21
et al. 2011). To increase skeletal stability and prevent relapse, the control of the proximal
segment is always important. (Chen et al. 2013)
Compared to patients who underwent split sagittal ramus osteotomy (SSRO), those that
received intraoral vertical ramus osteotomy (IVRO) showed a specifically altered long axis
postoperatively as well as an outward rotation of the condylar long axis. Furthermore, the
degree of rotation in the condyles that remodeled was significantly larger on average
than those without bone formation (Katsumata et al. 2006). Nonetheless, condylar
displacement and the condylotomy effect were minimized with the intraoral vertico-
sagittal ramus osteotomy (IVSRO) surgical technique therefore decreasing the symptoms
of postoperative iatrogenic temporomandibular joint disorder (Kim YJ et al. 2014).
Multiple studies were conducted to track the post-operative movement of the condyles
after certain periods of time. Kim et al found that immediately after surgery, there is
anterior displacement of the condyle. At 3 months, a distal movement was seen from the
axial view and an inward rotation from the coronal view. There was evident rotation of
the condyle 3-6 months later, and condylar stability 6 months later (Kim YJ et al. 2014).
Other studies found different condylar movements. Chen et al found that immediately
after surgery, the condyles had moved posterior-inferiorly followed by an anterior-
superior movement 3 months after surgery. Ultimately, there was a net posterior-superior
movement when comparing the condyle position pre-surgery and 3 months post-surgery
and remains stable during the 1-year follow-up. (Chen et al. 2013, Rotskoff et al. 1991,
Schendel et al. 1980, Sickels et al. 1999, Motta et al. 2011). Chen et al concluded that the
posterior displacement may be caused by the manual manipulation of the proximal
segment during surgery (Chen et al. 2013). However, these measurements were taken
from 2 dimensional images extracted from a 3D volume, therefore it is not as accurate as
if they had been measured in the original 3D image.
In class III malocclusion surgical patients, Kim YJ et al also stated that the condyles moved
anteriorly during the surgery and posteriorly after the surgery. They also stated that the
initial anterior displacement of the condyles could be related to the surgical edema or

22
hemarthrosis. When examined more carefully, they found that, up until 3 months after
surgery, the condyle moved more distally, and the mesio-lateral distance decreased
causing the narrowing of the intercondylar distance. After 3 months for asymmetric
cases, the undeviated side moved towards the midline whereas the deviated side moved
pack to its presurgical position. Also, the tendency of the proximal segment to autorotate
may cause the mandibular condyle or ramus after surgery to autorotate anteriorly. This
may be related to the direction of surgical relapse. However, after 6 months, the condylar
positions were relatively stable (Kim et al. 2013).
Carvalho found torqueing of the ramus with mandibular advancement (Carvalho et al.
2010). On the contrary, Kim et al found that condylar angulations in all dimensions did
not change after single-jaw surgery unlike that of those that received double-jaw surgery
who showed a forward and medial rotation in the sagittal and axial planes respectively
(Kim et al. 2012). Cevidanes concluded that condylar displacement associated with 2-jaw
surgery was not significant when compared to maxillary only surgery (Cevidanes et al.
2005)
Condyle positional changes after orthognathic surgery are difficult to predict. Many
studies have been conducted to examine the changes of the structures before and after
orthognathic surgery in mandibular-only surgery, bi-maxillary surgery, and unilateral
osteotomies. However, condylar displacement is difficult to differentiate from errors in
conventional 2D radiography because the condyles may have been displaced in more
than one plane during surgery in both position and inclination. Three-dimensional
models, registered on the anterior cranial base are a more reliable way to compare pre
and post-surgical condylar changes since translation and rotation may be seen in all
planes of space at the same time (Cevidanes et al. 2005, De Clerck 2012).

23
E. Methods Of Assessing Condylar Position Changes
Several radiographic modalities have been used to evaluate condylar displacement, such
as linear tomography, submentovertex radiography, lateral cephalometric radiograph,
computed tomography and MRI (Will et al 1984, Alder et al 1999, Pancherz et al. 1999).
More recently, CBCT has been applied in the maxillofacial region because it provides
accurate 3-dimensional imaging of the TMJ complex (Chen et. al 2013, H.J. Yang and S.J
Hwang 2014; Kim et al 2011, Carvalho et al 2012, Cevidanes et al 2007, De Clerck et al
2012).

Former Methods of Assessing Changes in Condylar Displacement
Will et al. in 1984 took a submental vertex film, a lateral cephalogram, and right and left
temporomandibular joint tomograms to evaluate to assess condylar position
preoperatively and at three specific times postoperatively.
First, the basilar film was analyzed to determine the angle between the long axis of each
condyle and the midsagittal line (Fig 4). The long axis of the condyle was defined as a line
connecting the medial- and lateral-most points of the contour, and the midsagittal plane
was constructed as a “best fit” line between the internal occipital protuberance, the
posterior limit of the foramen magnum, the anterior limit of the foramen magnum, and
the frontal crest. The perpendicular distance from the midsagittal plane to the center of
the condylar axis was also measured to determine the depth of cut for the tomograms,
which were then exposed with the patient’s head rotated to position the long axis of the
condyle parallel with the patient’s mandible manually positioned by the examiner.

24

Fig 4: Basilar film to determine the angle between the long axis of each condyle and midsagittal plane. (Will et
al. 1984)

The lateral films were traced and superimposed using the ethmoid triad, nasion, the
posterior cranial fossa, and the soft tissue contour of the upper face as references. The
center of the condyle (CC) was located on the film in which it was most evident and
transferred to successive films during superimposition, insuring constancy of its position.
This permitted quantification of proximal fragment movement by measuring linear
changes between points CC and Gonion.
Tomograms were traced and superimposed to measure superoinferior and
anteroposterior movements of the condyle and inclination of the condyle in a sagittal
plane. Inclination of the proximal condyle and distal fragment were referred to as either
clockwise, with the anterior portion moving inferiorly, or counterclockwise, with the
anterior portion moving superiorly. On the preoperative films two arbitrary points were
located along the neck of the condylar process as an axis and a cross of perpendicular
lines was constructed through the more superior point. Two additional points were
arbitrarily marked in the cranial base (Fig 5).

25
Their study showed that there was no significant rotation or change in the
anteroposterior position of the condyles. Although there were tendencies for
counterclockwise inclination and inferior movement of both condyles, these were not
statistically significant.

Fig 5: On the top, tomograms including condylar contour with axis points and cross for reference; contour of
glenoid fossa; cranial base detail and reference points. On the bottom, superimpositions of condylar contours
using perpendicular cross as reference to show successive movements of condyles.

Pullinger and Hollender in 1986 measured the condyle position in tomograms. The
methods used to evaluate the condyle position were: linear measurements of the
posterior and anterior joint space; horizontal displacement of condylar midpoint from the
fossa’s midpoint; posterior interarticular dimension and the anterior interarticular
dimension. (Figure 6)

26

Fig 6: Pullinger and Hollender method

Alder et al. in 1999 used Computed Tomography to determine preoperative and 8 week
postoperative condylar position. Orbital walls, zygomatic arches, and external auditory
meatus were the landmarks superimposed to compare before and after CT scans. The
condylar positions that they looked at were: Mediolateral condylar position and condylar
angulation (Fig 7); Superior-inferior condylar position and rotational changes in condylar
position from sagittal view (Fig 8) and anterior-posterior condyle movement (Fig 9).

27

Fig 7: Axial Slice.
To look at condylar angulation and mediolateral position, the axial slice with the greatest
mediolateral dimension of condyle was used as reference image in left and right TMJ. The
midsagittal line (A) was identified as a line drawn from height of clivus of sphenoid
through base of vomer. A second line (B) was drawn through long axis of condyle to
determine angle (BC). The Distance (C) was measured from medial pole of each condyle
to the midsagittal line.

Fig 8: Sagittal section through mid-condyle and coronoid process.

28
From the sagittal view, a 2-dimensionally reformatted image through center of condylar
and tip of coronoid process was captured to measure rotational movements and superior-
inferior condylar changes. An initial line was drawn from the head of the condyle to the
tip of the coronoid process (A). A second line was drawn from the articular eminence to
the superior border of the glenoid fossa (B). A third line (C) was drawn beginning at the
most superior part of the glenoid fossa and extended parallel to line A; this third line
represents distance between head of condyle and top of glenoid fossa. The distance is
measured perpendicular to lines A and C (Fig 8).

Fig 9: Two-dimensional reformat perpendicular to condyle long axis.

To measure the antero-posterior condyle movement, a reference line (A) was drawn from
the most superior point on condyle to the posterior border of ascending ramus. A second
line (B) was drawn from most superior part of glenoid fossa inferiorly parallel to line A.
Distance (C) is measured between lines A and B.
Eventhough, the CT data was transferred to a workstation that can perform 2-
dimensional and 3- dimensional reconstruction and measurements, all measurements
were made exclusively on 2-dimensionally reformatted images.

29

Recent Methods of Assessing Changes in Condylar Displacement
In 2010, Carvalho et al took CBCT scans before and after surgery, and evaluated condyle
movement following the method developed by Cevidanes et al in 2006, which allows
analyzing and superimposing 3-dimensional CBCT models. First, the structures of interest
are segmented from the CBCT DICOM files using ITK-SNAP software. Then the pre-
surgical and post-surgical models are registered with the cranial base as a reference
structure (since this is not altered during surgery) using IMAGINE software. This software
compares 2 images by using the intensity of gray scale for each voxel of the pre-surgical
cranial base. Then condyles, rami and chin are relocated with the cranial base.
CranioMaxilloFacial software (Maurice Muller Institute, Bern, Switzerland) is used to
quantify differences between the 2 surfaces in 3D. This software calculates thousands of
color-coded point-to-point comparisons (surface distances in millimeters) between the 3-
dimensional models, so that the differences between 2 surfaces at any location can be
precisely quantified. (Fig 10)

30

Fig 10 : CMF application allows the identification of the greatest displacement of a specific anatomic region.

More recently, Chen et al. collected CBCT scans of 31 patients before and after surgery.
However, condylar position changes were evaluated using Kamelchuk’s technique in 2-
dimensions and Pullinger and Hollender’s method (Pullinger and Hollender in 1986;
Kamelchuck et al 1196; Chen et al 2013).
Other methods described so far to calculate surface distances in 3D include Geomagic
Studio Software, (Geomagic U.S. Corp, Research Triangle Park, NC: Vultus, 3dMD,
Atlanta, GA), which calculates the closest points between 2 surfaces. (Cevidanes et al
2006; Carvalho et al 2010)

31
Eventhough 3D analysis grants additional information compared to traditional
radiographic methods when assessing condylar position, quantification of the 3D
positional changes is still challenging. However, current studies are focusing on
developing methods to quantify vectorial displacement, which will improve evaluation of
condylar changes after surgery.

F. Condylar Resorption And Surgical Stability
The importance of determining the change in position of the condyle has been a topic of
interest because of the possibility of condylar resorption and surgical relapse.
Condylar resorption was first reported in the eighties. It has been defined in many
different ways, and its definition is still being questioned. It is described as an extreme
structural change of the condyle that leads to the decrease in condylar and ramus height,
which decreases posterior facial height (Hoppenreijs et al. 1999, Cutbirth et al. 1998).
Kobayashi et al not only described condylar resorption to be of an obvious reduction in
the height of the ramus, but also a posterior rotation of the proximal segment. Moore et
al. claim that the term condylar resorption should be defined as total condylar resorption
in the presence of systematic disease.
However, only the definition of condylar resorption is a topic of debate. Its cause is still
under study too. Researchers have tried to connect condylar resorption with different
factors, and they have found that certain condyle shapes and deformities are more
susceptible to condylar resorption, but the etiology is still unclear (Moore et al. 1991;
O’Ryan et al. 1984; Kobayashi et al. 2012; Park et al. 2012).
Condylar resorption can be caused by patient factors such as systemic diseases and
disorders, anatomy-dependent factors, and also surgical factors. Furthermore,
remodeling of the condyles has been associated with prosthodontics rehabilitation,

32
orthodontic treatment, condylar fractures, and osteotomies of the mandibular ramus
(Lambert et al. 1986, Hoppenreijs et al. 1998).
Other than morphologic changes of the condyle due to the change in position and forces
of the hard and soft tissue, other factors were found to make certain groups more prone
to condylar resorption. Posteriorly inclined condylar necks were considered a nonsurgical
risk factor for resorption (Chen et al. 2013). Furthermore, resorption was found to be
more prevalent in women, especially those with high mandibular plane angles,
preoperative temporomandibular dysfunction, a large mandibular advancement, and
counterclockwise rotation of distal segment (Cutbirth et al. 1998). Hoppenreijs et al also
reported progressive condylar resorption to be more prevalent in females with
preexisting TMJ dysfunction, within the age range from 20-30, and those that have
undergone large advancements of the mandible (Hoppenreijs et al. 1999). Additionally,
hormonal changes may also be a prominent factor in condylar resorption (Kobayashi et
al. 2012). Even the predisposed occlusal relationship can cause certain patients to be
prone to resorption. Isolated resorption of the superior part of the condyles was a
tendency in patients with a deep bite (Hoppenreijs et al. 1999). However, even with all the
association with progressive condylar resorption, the etiology is still unclear (Kobayashi
et al. 2012, Park et al. 2012).
In orthognathic surgery, there are multiple theories of what causes condylar resorption.
Kobayashi et al concluded that condylar resorption may occur when mechanical loading
exceeds the adaptive capacity of the condyle when the surrounding soft tissue
components are stretched. This tension will ultimately cause a retrusive force into the
fossa (Kobayashi et al. 2012).
Another surgical risk factor in the etiology of condylar resorption is the mechanical
loading during or after bilateral sagittal split osteotomy (BSSO) since it impedes the
blood flow in the condyle and the capsule of the TMJ. Furthermore, the interdigitation of
an unstable occlusion can produce loading of the condyles. Therefore, the stabilization of

33
the occlusion will allow for the TMJ to be restored to a functional equilibrium
(Hoppenreijs et al. 1999, Chen et al. 2013).
Looking at surgical stability, there are many reasons for relapse: Worms et al expressed
that condylar resorption contributes to relapse (Worms et al. 1980, Hoppenreijs et al.
1999). Park et al believe that pre-existing unrecognized and untreated TMJ pathologic
features or orthognathic surgery-incurred TMJ conditions such as joint damage may lead
to postoperative instabilities, although they also believe that morphologic changes and
dysfunction of the TMJ will not occur as long as the condylar displacement is within the
physiologic capability of the adaptive mechanics (Park et al. 2012). Kim et al concluded
that condylar positional changes and soft-tissue tension are frequent findings in early
post-surgery instability. However, even if the condylar position is controlled, the increase
in muscle and soft tissue tension may cause future relapse (Kim et al. 2011). Epker agreed
that skeletal relapse may occur even though skeletal stabilization is employed and the
proximal segment is controlled. The two reasons being, one of dental nature, and the
other of skeletal growth. Dental compensations before surgery may relapse after surgery
therefore compounding the situation which is inherently a post-surgical problem.
Furthermore, delayed skeletal growth may also cause relapse due to growth of the
mandible or maxilla or condylar degeneration (Epker et al. 1982).
Kim et al believed that postoperative occlusion and positional change of the condyle are
major factors related to surgical relapse (Kim et al. 2012). Peterson and Wilmar-Hogeman
found that the degree of post-operative condylar displacement and the incidence of
resorption had a positive correlation (Peterson et al. 1989), which Park et al later
confirmed that condylar positional change can induce postoperative early or later skeletal
relapse as well as TMJ symptoms (Park et al. 2012).
The movement of the maxilla, mandible, or both can highly influence the incidence of
condylar resorption. With bimaxillary orthognathic surgery, there was a decrease in the
condylar heights and condylar head remodeling (Park et al. 2012). However, long-term
stability studies revealed that maxillary advancement surgery was more stable than bi-

34
maxillary orthognathic surgery (Cevidanes et al. 2005). Nonetheless, Kim et al. stated
that the extent of maxillary movement may highly influence the vertical relapse rate (Kim
et al. 2011).
With mandibular advancement, the incident of progressive condylar resorption can be up
to 31% depending on the population studied (Bouwman et al. 1994, Kobayashi et al.
2012). The immediate relapse subsequent to a mandibular advancement surgery with
rigid fixation has been well documented (Cutbirth et al. 1998). Hoppenreijs et al found
that progressive condylar resorption occurs after sagittal split advancement osteotomies
regardless of whether it is accompanied by maxillary surgery or not (Hoppenreijs et al.
1999).
Post-surgical relapse has been a major concern in orthognathic surgical corrections. With
the introduction of rigid internal fixation, some of the problems have been resolved
(Strauss et al. 1993). Furthermore, the incidence of condylar resorption after bimaxillary
osteotomies was reduced after intermaxillary fixation was avoided (Bouwman et al.
1994).
Skeletal relapse due to resorption is apparent at specific time points post-surgery.
Condylar resorption can be first seen radiographically starting at 6 months after surgery
(Cutbirth et al. 1998, Hoppenreijs et al. 1998, Katsumata et al. 2006). Therefore, with the
presence of resorption, open bites can be seen within the first 6 months postoperatively
(Hoppenreijs et al. 1998). Not only is skeletal relapse a change that can be seen after 6
months but also occlusal changes can be seen (Kobayashi et al. 2012). Franco et al
observed that small condylar changes continue beyond one year post-surgery with
variation in the direction of change (Franco et al. 2013).
The change in position of the condyle can cause certain areas of the condylar head to
remodel or resorb and ultimately cause relapse post-surgery. In 1992, Arnett et al
suggested that condylar resorption and late relapse may occur if rigid fixation results in
mediolateral torqueing or posterior positioning (Arnett et al. 1992). Because
inappropriate condylar positioning can lead to postoperative complications such as

35
idiopathic condylar resorption, functional disorder, and post-operative relapse, it is
important to study the condylar positional change after surgery (Kim et al. 2013; Chen et
al. 2013). Several studies have proved that CBCT provides an accurate 3D image of the
TMJ complex and is possibly the best choice for evaluating condylar displacement after
orthognathic surgery since it allows accurately studying the position, movement, and
remodeling of the condyles. (Chen et al. 2013; Maal et al. 2012; Kobayashi et al. 2012).

VI. MATERIALS AND METHODS

A. Sample
Subjects
The subjects of the present study included 17 consecutive patients (10 male, 7 female)
diagnosed with skeletal Class II or Class III malocclusion (14 skeletal class II patients and 3
skeletal class III). All of them received pre-surgical orthodontic treatment and underwent
bi-maxillary surgery by the same oral surgeon. The surgeon had used Medical Modeling
(VSP Orthognathics; Golden, Colorado) to virtually treatment plan the surgeries.
Surgical technique and postsurgical protocol
All patients were treated by the same surgeon with a maxillary Le Fort I osteotomy and
Bilateral Sagittal Split Osteotomy (BSSO) and used rigid fixation (plates).
Data Acquisition
For each patient, pre-surgical and 2-week post-surgical CBCT scans were acquired using
the same machine (iCat 3D dental imaging system,) to a standard protocol (120 kVp; 5
mA; 23cm x 17 cm field of view; with a scanning time of 67 seconds; and image acquisition

36
at 0.4mm voxel size). Scans had to include both condyles and both glenoid fossas in order
to accurately compare the pre-surgical and post - surgical condylar positions.
The scanned data were then exported as DICOM files which were anonymized, and stored
in a directory by a code. The age and sex of the patients were the only information
collected. Other personal information was not recorded.
These DICOM files were then imported into ITK-SNAP software to segment 3D images
for further analysis.

B. Method
Selecting the Region of Interest
Each pre-surgical and 2-week post-surgical DICOM file was uploaded into ITK-Snap
(version 2.4.0; www.itksnap.org) to segment the regions of interest within the
temporomandibular joint (TMJ).
The image summary on the wizard for loading a grayscale image had dimensions set at
400, 400, 547 slices, spacing set at 0.40mm, 0.40mm, 0.40mm, and the orientation was
set at RAJ. The crosshairs mode was used to view the condyle on the orthogonal axial,
coronal, and sagittal planes. The image contrast of the isolated grayscale image was then
adjusted to show the greatest contrast between the glenoid fossa and the condylar head.
The curve control point was set at 1 point. Prior to initiating segmentation, the label color
was set. The active drawing label color was set to draw over a clear label to allow the
condyle to be drawn in red and the glenoid fossa in green.
The semi-automatic segmentation mode was then used on each temporomandibular
joint complex to isolate the region of interest (Fig 11). This area isolated was defined as
follows:

37
 The posterior margin of the region of interest was set to include the most inferior
border of the mastoid process seen on the sagittal slice.
 The anterior margin was set to include the frontal bone of the cranial base from
the sagittal slice.
 The medial margin was set to include the apex of the petrous temporal bone seen
on the frontal slice.
 The lateral margin was set to include the outermost layer of the skin.
 The superior margin included the frontal bone of the cranial base.
 The inferior margin was set to include the body of the ramus just above the
lingual foramen.

Fig 11: Isolation of the region of interest for segmentation

38
Once the selection box contained the structures of interest, the segmentation process
was initiated.
For step 1, pre-processing, the intensity regions were adjusted. With the selection of the
combined display, the hard tissue can be seen more clearly. The upper threshold was set
to its maximum and the lower threshold and smoothness was adjusted so that the border
of the condylar head and glenoid fossa was clearly defined.
For step 2, geodesic snake initialization, the initialization centers were placed evenly
spaced throughout the structure of interest. The radii of the spheres were adjusted to
stay within the structure of interest.
Finally step 3, segmentation, was initiated until the spheres grew to coalesce with one
another and fill the structure of interest, and ultimately finalized when the structure of
interest was identified. (Fig 12)

Fig 12: Segmentation. Spheres coalesce until the structure of interest is identified.

39
To refine the segmentation, the mesh was edited using the scalpel to cut the gross
structures segmented due to the leakage of the nucleoids. Starting with the axial view
and using the coronal and sagittal view as verification, the polygon option was used. The
labels were adjusted to either draw in the un-segmented object of interest with the
appropriate label color over a clear label, or it was used to erase an unwanted area by
drawing over the label color with a clear label.
Once the object of interest was segmented and refined, the segmentation was saved in a
“.gipl” and “.stl" format.
Evaluation of condylar displacement using superimposition
To make comparisons of the measurements at different times possible, Geomagic Studio
Software (Version 10; Geomagic U.S., Research Triangle Park, NC) was used to
superimpose and analyze the movement of the condyles before and after surgery, using
the glenoid fossa as the reference structure. Because each time a CBCT scan is taken it
has a different orientation (as it is very difficult to take radiographs in exactly the same
position at different time points), the glenoid fossa was registered to be the stable
reference structure. This helped reveal the true movement of the condyle resulting from
manual manipulation of the proximal segment during surgery and intra-articular edema,
ruling out the effect of head positioning during the scan.
For each patient, the “.stl” format of the segmented pre-surgical and post-surgical
condyles and glenoid fossa were imported into the Geomagic Studio Software (Version
10; Geomagic U.S., Research Triangle Park, NC). The glenoid fossa was hidden until the
registration of the structures.
The right and left condyles were registered separately to prevent one condyle from
affecting the registration of the other condyle. With only the pre-surgical (PreC) and
post-surgical condyles (2wkPostC) of one side visible, a copy (2wkPostC
copy
) was made of
2wkPost. PreC and 2wkPostC were “pinned” (a software program option that prevents
any movement of the object) to prevent any movement of these two objects. To crop the

40
post-surgical condyle at the same level as the pre condyle, to allow for similar volumes,
the 2wkPostC
copy
was manually registered to the pinned PreC. This was done using 3
landmarks visible on both condyles, selected upon the visual judgment of the evaluator.
Then they were globally registered to ensure an accurate superimposition. Once the
2wkPostCcopy was cropped at the same level as the pre, it was registered to the pinned
2wkPostC
copy
to move the cropped object to its original position. (Fig 13)

Fig 13: Superimposition of pre and post condyles to be cropped at the same level.

Before continuing with the superimposition process, it was verified that the coordinates
of the 2wkPostC
copy
were back to (0,0,0) to avoid errors in the measuring process.
The pre-surgical glenoid fossa (PreGF) was pinned and the post-surgical glenoid fossa
(2wkPostGF) was then globally registered to PreGF. The transformation matrix describing
the movement of 2wkPost GF was then saved and loaded to 2wkPost C
copy
to move the 2
week post-surgical condyle the same distance and direction as its corresponding 2 week
post-surgical glenoid fossa. This way the true displacement of the condyles pre-surgery
and post-surgery was revealed. (Fig 14)

41

Fig 14: True displacement of the condyles revealed pre-surgery (blue) and post-surgery (red)

Evaluation of condylar displacement using a coordinate system for bodily shift and
rotational changes
Once the true displacement of the condyle was revealed, having extracted the error of
head orientation when taking the CBCT scan, the pre surgical condyle and 2 week post-
surgical were reoriented in the 3 planes of space to (0,0,0) so that the amount of
movement measured included no error.
In order to assess the amount of movement and rotation in the 3 planes of space, the pre-
surgical condyle (PreC) was pinned and the 2wkPostC
copy
condyle were manually and
globally registered.
The transformation matrix describing the movement of the 2 week post-surgical condyle
was then saved and a table was made with the amount of translational and rotational
movement. (Table 3)

42
Statistical Analysis
Descriptive statistics and statistical analysis were performed using SPSS software (SPSS
Inc, Chicago, IL) in order to determine if condylar changes in six degrees of freedom were
statistically significant and if there was a relationship between age and gender and
amount of movement.
ANOVA test was used to see if there was any relationship between the groups (age and
gender). A One Sample T-Test was used to see if there were any statistically significant
differences between right and left condyles. To assess method error and reproductibility
of all measurements, 11 random cases were selected and measured again one month
later and an Intraclass Correlation Coefficient of 99% was achieved.
In order to avoid Type I Error due to multiple comparisons, we applied the Bonferroni
correction (p<0.008).

VII. RESULTS
This study included 17 consecutive patients (10 male, 7 female) diagnosed with skeletal
Class II or Class III malocclusion (14 skeletal class II patients and 3 skeletal class III) of ages
between 20 – 53 years. The amount of condylar displacement between pre-surgical and 2
week post-surgical CBCT scans is collected in Table 3. Six measurements were extracted
per patient and per side (translation and rotation on the 3 planes of space).

43

Table 3: Amount of condylar displacement per patient and condyle on the 3 planes of space (x, y, z), for both,
translation and rotation

44
A. Evaluating Condylar Movement in 3 planes of space: Translation & Rotation
The average condylar displacement was 0.78 mm on x plane, -3.80 mm on y and 0.14 mm
on z plane. As for rotation, the average movement was 0.06 º on x plane, 0.30º on y and -
0.27º on z. The greatest displacements were translation in y axis (anteroposterior) and
rotation on z plane (superoinferior), which were also the only movements statistically
significant (p<0.008). (Table 4 and Table 5)

Table 4: Range, mínimum, máximum, mean and standard deviation of condylar movement

45

Table 5: Significance values for all six variables

When comparing right and left sides, statistical significant differences were found only on
the amount of translation on Y plane (Table 6 and 7)

Translation
o X Plane: 30 out of the 34 condyles moved between 0 - 2.5mm and only 4 moved
between 2.51 – 5mm. None moved more than 5 mm on X Plane.
o Y Plane: 19 moved between 0 – 2.5mm; 5 moved between 2.51-5 mm and 10 moved
more than 5mm
o Z Plane: 26 condyles moved less than 2.5mm; 7 moved between 2.51-5; and only 1
moved more than 5 mm.

46
Rotation
o X Plane: 24 out of the 34 condyles moved between 0 - 2.5 degrees; 9 moved between
2.51 – 5º and only 1 moved more than 5º on X Plane.
o Y Plane: 22 moved between 0 – 2.5º; 9 moved between 2.51-5º and just 1 moved
more than 5º
o Z Plane: 7 condyles moved less than 2.5º; 9 moved between 2.51-5º; and 18 moved
more than 5º

B. Identifying Factors Affecting Greater Condylar Movement
When comparing right and left sides, only differences in Translation on Y plane were
found to be statistically significant (p<0.008). Table 6 compares the differences in mean
and movement between right and left condyles and Table 7 shows the significance values.

47
Table 6: Mean and S.D on each plane for right and left condyles.

Table 7: Significance values comparing right and left sides

No relationship was found between age and amount of condylar movement or between
gender and condylar movement (p>0.05). Table 8 shows the means of movements in
each plane, by gender.

48
Table 8: Mean and S.D on each plane by gender.

When looking individually at the cases, patients with condylar resorption present prior to
surgery or with abnormal anatomy, were the ones with the greatest amount of
movement, both on Y plane translation and Z plane rotation. (Eg: Fig 15-13)

49

Fig 15: Condylar resorption present prior to surgery and abnormal anatomy. Blue is pre-surgical position and
red post surgical.

Fig 16: Condylar resorption present prior to surgery and abnormal anatomy. Blue is pre-surgical position and
red post surgical.

50

Fig 17: Condylar resorption present prior to surgery and abnormal anatomy. Blue is pre-surgical position and
red post surgical.

Fig 18: Condylar resorption present prior to surgery and abnormal anatomy. Blue is pre-surgical position and
red post surgical.

51
VIII. DISCUSSION
Condylar displacement following orthognathic surgery is a great area of interest because
of its relation with condylar resorption and surgical relapse. Many have studied the effect
of orthognathic surgery on condylar position, traditionally on 2-dimensional radiographs
and more recently in 3D. However, there are many difficulties in conducting three-
dimensional measurements of condylar position changes and most studies, eventhough
they have used 3 dimensional records, they have evaluated these changes in 2
dimensions, with its inherent limitations knowing that changes in the TMJ are 3
dimensional.
In the present study, CBCT scans were taken before and 2 weeks after bi-maxillary
surgery to assess immediate condylar positional changes. The mean movements for
translation and rotation were measured separately in three planes of space for right and
left condyles (Table 4 and Table 6) using the glenoid fossae as registration surfaces. The
average condylar displacement was 0.78 mm on x plane, -3.80 mm on y and 0.14 mm on z
plane. As for rotation, the average movement was 0.06 º on x plane, 0.30º on y and -0.27
on z. The only significant translation movement was on Y plane (anteroposterior
changes), and rotation on z plane (superoinferior).
According to previous studies, condylar displacement immediately after mandibular
advancement surgery is variable. The present study’s results coincide with Chen et al.
who found that condyles moved posteroinferiorly with surgery. Posterior displacement
can be attributed to the manual manipulation of the proximal segment during surgery,
and inferior displacement is a result of intra-articular edema immediately after surgery
(Chen et al 2013). Rotskoff et al. in 1991 also found a significant inferior movement
immediately after surgery (Rotskoff et al. in 1991). Will et al. in 1984 observed a
significant superior movement, which can be expected from the masticatory muscle pull
during fixation.
However, quantitative comparisons cannot be made considering that the methods to
evaluate the amount of movement are different in each study. Rotskoff et al. obtained

52
full head tomograms one day after surgery and made linear measurements on these.
Chen et al, in spite of taking CBCT scans 1 day after surgery, also calculated the amount
of movement in 2 dimensions by the method of Pullinger and Hollender.
In contrast, Yeon-Joo Kim et al. found that condyles moved anteriorly during surgery,
which they also related to surgical edema or hemarthrosis. Their results coincide with Kim
YI et al. in 2010. Yeon-Joo Kim et al. also noticed that mandibular condyles tended to
move mesially, decreasing intercondylar distance, although this movement was not
statistically significant. In our study there was also a mean movement of 0.78mm medially
and an inward torqueing of the condyles is visible in some cases (x plane rotation). (Kim
YJ et al 2014; Will et al. 1984; Kim YI et al. 2010).
Other authors like Carvalho et al. in 2010 and Motta et al. in 2011 also visualized changes
in condylar displacement in 3 dimensions. Using color mapping and CMF software they
calculated the amount of displacement and also found a postero-superior displacement
of the condyles with surgery. Yet, in spite of taking CBCT scans and evaluating condylar
position changes in 3D, they only measured condylar movement in one plane, and used
color mapping to visually assess condylar displacement. This study, on the contrary, is the
only one that has measured condylar displacemet in its six degrees of movement
therefore its results cannot be compared to any other study.
Eventhough there are more studies that evaluate condylar position after surgery (Kim et
al. 2012; Kim et al. 2011; Katsumata et al 2006), it is not possible to compare their results
to our study on the grounds that their x-rays were taken after splint removal. Once the
splint is removed post surgery, the mandible autorotates and hence, there is some
amount of condylar displacement. Also at this timepoint, as previous studies have
shown, condyles start to move back towards their preoperative position. (Chen et al.
2013)
The only statistically significant movements found in this study were translation on y axis
(anteroposterior) and rotation on z plane.

53
A posterior movement of the condyle was identified, although the Dawson Technique
was used to seat the joint in the fossa superiorly (Fig 19-20). This technique consists on
pushing down at the chin (a) and pushing upwards at the angle of the mandible (b),
seating the condyle in a vertical position.

Fig 19: Dawson Technique for condylar seating

A
B

54

Fig 20: Dawson Technique during surgery. Downward force is applied with an instrument at the distal of the
proximal segment (A) while pushing upwards at the mandibular angle (B)

Translation on Y axis can be explained by initial position of the joint in the fossa. For some
patients, due to abnormal anatomy or severe resorption prior to surgery, it is difficult to
find centric relation both before and during surgery (Figs 15-16). Once the proximal
segment of the mandible is not affected by the occlusion, the condyle relocates in
relation to the glenoid fossa. Therefore, the change assessed includes both, the surgical
change and the condylar relocation change. This is one of the limitations of our study.
No translation on X and Z plane was found because the anatomy of the fossa limits these
types of movements. The disc prevents superoinferior movements and the fossa itself
prevents mediolateral translation of the condyle.
The biggest amount of rotation found was in Z plane. The high range of rotational
movement in Z plane is expected since it’s the plane where surgeons have the most
degree of freedom when placing the proximal segment of the mandible doing clockwise
or counterclockwise rotations (Fig 21). Eventhough the position of the condyle varies
widely on this plane, it rarely causes any compression anywhere on the joint. For this
reason, secondary effects are not expected due to this type of rotation.
A
A
B

55

Fig 21: shows rotation on Z plane. Blue is pre surgical and red post surgical.

There were two cases where a big rotation in X plane was found (mediolateral). This kind
of rotation is not ideal because of the anatomy of the TMJ. As the condyle turns
mediolaterally, areas of the condyle might run into the glenoid fossa and this
compression can cause condylar resorption in the long run (Fig 22).

Fig 22: shows medial rotation of the left condyle

56
This kind of rotation cannot be identified in 2 dimensions and can be mistaken with
condylar sag, seeing that when the condyle rotates in this plane and hits a part of the
glenoid fossa, it pushes the joint inferiorly. If evaluated in 2 dimensions the sagittal cut
will only identify the space between the condyle and the glenoid fossa missing the
contact point where the condyle is actually compressed into the fossa.
What makes joints move in this direction is normally a bony interference between the two
mandibular segments, which forces the surgeon to squeeze them together during
fixation, resulting in X rotation of the condyles. Some cases are also due to the
malpositioning of the segments. In our study, both cases that had the highest rotational
movement on X plane, had big mandible advancements, which makes it harder for the
segments to fit together because of the anatomy of the mandible, and therefore, when
fixation had to be placed, it resulted in a bigger rotation of the condyles on X plane.
The component of translation related to the X rotation depends on where the
interference is. When seating the joints during surgery, if there is a bony contact between
the distal tooth bearing fragment and the condylar bearing fragment, the surgeon looses
feel of where the condyle must be seated. The way to avoid this problem would be to
either displace the proximal segment, which results in a bigger translation of the condyle,
or, the bony interference must be removed to avoid the rotation of the condyle in X
plane.
The disparity on amount of translation on Y plane between right and left condyles cannot
be identified. Both were positioned by the same person standing behind the patient.
Due to the small sample in this study, we could not investigate the effect of the type of
surgery on the amount of displacement nor the relationship between the type of
malocclusion and the condylar changes.
Similarly, our study didn’t have enough power to establish a relationship between age
and amount of movement considering there was a big range of ages in such a small
sample size.

57
IX. CONCLUSIONS
Precise repositioning of the condyles during surgery may ensure stability of the surgical
results and reduce change of post-surgical TMJ problems. The variability in postoperative
adaptations requires additional investigation using 3D superimposition methods.
The posterior displacement seen in our study may be related to the manual manipulation
of the proximal segment during surgery and the rotation in Z plane is expected seeing
that it is the plane with the most degree of freedom when seating the condyle during
surgery.
Rotation in X plane was not statistically significant, but cases with the highest rotation in
this plane had condylar resorption prior to surgery and bigger mandibular advancements.
Further research is needed to evaluate the relationship between condylar resorption
present prior to surgery or abnormal anatomy, and amount of movement up to 12
months after surgery, as well as the association between amount of condylar movement
within the 2 first weeks after surgery and development of post-surgical condylar
resorption.

58
X. APPENDIX
Images of the condylar position changes of all the cases included in this study. Blue is pre-
surgical and red two weeks post-surgical.
039
Right

Left

59

195

Right

Left

60
265
Right

Left

61
344
Right

Left

62
455
Right

Left

498

63
Right

Left

683

64
Right

Left

65
770
Right

Left

783

66
Right

Left

877

67
Right

Left

897
Right

68

Left

911
Right

69

Left

925

70
Right

Left

927

71
Right

Left

965

72
Right

Left

972

73
Right

Left

994
Right

74

Left

75
XI. REFERENCES

1. Alder et al. Short term changes of condylar position after sagittal split
osteotomy for mandibular advancement. Oral Surg Oral Med Oral Pathol Oral Radiol
Endod. 1999 Feb; 87(2):159-65.
2. Al-koshab et al. Assessment of condyle and glenoid fossa morphology using CBCT
in South-East Asians. PLoS One. 2015 Mar 24;10(3)
3. American Academy of Oral and Maxillofacial Radiology. Clinical recommendations
regarding use of cone beam computed tomography in orthodontics. Position statement
by the American Academy of Oral and Maxillofacial Radiology. Oral Surg Oral Med Oral
Pathol Oral Radiol 2013;116: 238-257
4. American Dental Association Council on Scientific Affairs. The use of cone-beam
tomography in dentistry. An advisory statement from the American Dental Association
Council on Scientific Affars. J. Am. Dent. Assoc. 2012; 143:899-902
5. Arnett et al. Temporomandibular joint ramifications of orthognathic surgery, in
Bell WH: Modern Practice in Orthognathic and Reconstructive Surgery, Vol1. Philadelphia,
PA Saunders, 1992, pp 523-93
6. Bholsithi et al. 3D vs. 2D cephalometric analysis comparisons with repeated
measurements from 20 Thai males and 20 Thai females. Biomed Imaging Interv
J. 2009 Oct;5(4):e21.
7. Bouwman et al. Condylar resorption in orthognathic surgery. Oral Surgery Oral
Medicine Oral Pathology 1994;78:138-141
8. Carvalho et al. Three-dimensional assessment of mandibular advancement 1 year
after surgery. Am J Orthod Dentofacial Orthop 2010;137:553-5
9. Cevidanes et al. Clinical application of 3D imaging for assessment of treatment
outcomes. Seminars in orthodontics. 2011;17(1):72-80.
10. Cevidanes et al. Image analysis and superimposition of 3-dimensional cone-beam
computed tomography models. Am J Orthod Dentofacial Orthop 2006;129:611-18
11. Cevidanes et al. Superimposition of 3D cone-beam CT models of orthognathic
surgery patients. Dentomaxillofac Radiol. 2005;34:369-75
12. Cevidanes et al. Superimpositions of 3-dimensional cone-beam computed
tomography models of growing patients. Am J Orthod Dentofacial Orthop 2009;136:94-9
13. Cevidanes et al. Three-dimensional cone-beam computed tomography for
assessment of mandibular changes after orthognathic surgery. Am J of Orthod
Dentofacial Orthop. 2005;131:44-50
14. Chen et al. Short- and Long- term Changes of Condylar Position After Bilateral
Sagittal Split Ramus Osteotomy for Mandibular Advancement in Combination with Le

76
Fort I Osteotomy Evaluated by Cone-Beam Computed Tomography. Journal of Oral
Maxillofacial Surgery. 2013;71:1956-66
15. Coskuner and Ciger. Three-dimensional assessment of the
temporomandibular joint and mandibular dimensions after early correction of the
maxillary arch form in patients with Class II division 1 or division 2 malocclusion. Korean J
Orthod. 2015 May;45(3):121-9.
16. Cutbirth et al. Condylar Resorption after bicortical screw fixation of mandibular
advancement. J Oral Maxillofac Surg 1998;56:178-182
17. De Clerck et al. Three-dimensional assessment of mandibular and glenoid fossa
changes after bone-anchored Class III intermaxillary traction. Am J Orthod Dentofacial
Orthop. 2012 Jul;142(1):25-31.
18. De Vos et al. Cone-beam computerized tomography (CBCT) imaging of the oral
and maxillofacial region: a systematic review of the literature. . Int J Oral Maxillofac Surg
2009;38:609-25
19. Epker et al. Mechanisms of Early Skeletal Relapse Following Surgical
Advancement of the Mandible. British Journal of Oral Surgery 1982;20:175-182
20. Franco et al. Long-term 3-dimensional stability of mandibular advancement
surgery. J Oral Maxillofac Surg 2013;71:1588-1597
21. Garib et al. Is there a consensus for CBCT use in Orthodontics?. Dental Press J
Orthod. 2014 Sep-Oct; 19(5): 136–149
22. Grauer et al. Accuracy and Landmark Error Calculation Using Cone-Beam
Computed Tomography–Generated Cephalograms Angle Orthod. 2010 March ; 80(2):
286–294.
23. Grauer et al. Pharyngeal airway volume and shape from cone-beam computed
tomography: Relationship to facial morphology. Am J Orthod Dentofacial Orthop
2009;136:805-14
24. Grauer et al. Working with DICOM craniofacial images. Am J Orthod Dentofacial
Orthop Sept 2009;136:460-70
25. Halazonetis et al. From 2-dimensional cephalograms to 3-dimensional computed
tomography scans. Am J Orthod Dentofacial Orthop 2004;127:627-37
26. Halazonetis. Cone-beam computed tomography is not the imaging technique of
choice for comprehensive orthodontic assessment. Am J Orthod Dentofacial Orthop
2012;141:403-411
27. Haney et al. Comparative analysis of traditional radiographs and cone-beam
computed tomography volumetric images in the diagnosis and treatment planning of
maxillary impacted canines. American Journal of Orthodontics and Dentofacial
Orthopedics 2010;137:590-597

77
28. Hino et al. Three-dimensional analysis of maxillary changes associated with
facemask and rapid maxillary expansion compared with bone anchored maxillary
protraction. Am J of Dentofac Orthop 2014;144:705-714
29. Hoppenreijs et al. Condylar remodeling and resorption after Le Fort I and
bimaxillary osteotomies in patients with anterior open bite. Int J Oral Maxillofac Surg
1998;27:81-91
30. Hoppenreijs et al. Long-term evaluation of patients with progressive condylar
resorption following orthognathic surgery. Int J Oral Maxillofac Surg 1999;28:411-418
31. Hsu et al. Accuracy of a Computer-Aided Surgical Simulation Protocol for
Orthognathic Surgery: A Prospective Multicenter Study. J Oral Maxillofac Surg
2013;71:128-142
32. Kapila S. Cone Beam Computed Tomography in Orthodontics: Indications,
Insights, and Innovations.. Ann Arbor, Michigan: Wiley - Blackwell. 2014.
33. Katsumata et al. Condylar head remodeling following mandibular setback
osteotomy for prognathism: A comparative study of different imaging modalities. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:505-14
34. Katsumata et al. Condylar head remodeling following mandibular setback
osteotomy for prognathism: A comparative study of different imaging modalities. (Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:505-14
35. Kiefer et al. Dose exposure from analog and digital full mouth radiography and
panoramic radiography. Schweiz. Monatsschr. Zahnmed. 2004;114:687–693
36. Kim et al. Do patients treated with bimaxillary surgery have more stable condylar
positions than those who have undergone single-jaw surgery? J Oral Maxillofac
Surg. 2012 Sep;70(9):2143-2152.
37. Kim et al. Condylar positional changes up to 12 months after
bimaxillary surgery for skeletal class III malocclusions. J Oral Maxillofac Surg. 2014
Jan;72(1):145-156.
38. Kim et al. Cone-beam computerized tomography evaluation of condylar changes
and stability following two-jaw surgery: Le Fort I osteotomy and mandibular setback
surgery with rigid fixation. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology,
and Endodontology2011;111:681-87
39. Kim et al. Do patients treated with bimaxillary surgery have more stable condylar
positions than those who have undergone single-jaw surgery? American Association of
Oral and Maxillofacial Surgeons 2012. 0278-2391
40. Kim et al. Stability of mandibular setback surgery with and without presurgical
orthodontics. J Oral Maxillofac Surg. 2014 Apr;72(4):779-87.

78
41. Kim et al. The assessment of the short- and long-term changes in the condylar
position following sagittal split ramus osteotomy (SRRO) with rigid fixation. J Oral
Rehabil 37:262, 2010.
42. Kim et al. Proximal Segment Changes After Bilateral Sagittal Split Ramus
Osteotomy in Facial Asymmetry Patients. J Oral Maxillofac Surg. 2015 Aug;73(8):1592-
605.
43. Kobayashi et al. Progressive condylar resorption after mandibular advancement
British Journal of Oral and Maxillofacial Surgery 2012;50:176-180
44. Kokich V. Cone-beam computed tomography: Have we identified the orthodontic
benefits. Am J Orthod Dentofacial Orthop 2010;137:00
45. Lambert et al. Osteoarthritis and internal derangement of the temporomandibular
joint: A light microscopic study. Journal of Oral Maxillofacial Surgery 1986;44:634-43
46. Larson. Cone-beam computed tomography is the imaging technique of
choice for comprehensive orthodonticassessment. Am J Orthod Dentofacial Orthop. 2012
Apr;141(4):402-410
47. Ludlow and Walker. Assessment of phantom dosimetry and image quality of i-
CAT FLX cone-beam computed tomography. Am J Orthod Dentofacial Orthop
2013;144:802-17
48. Ludlow and Walker. Dosimetry of 3 CBCT devices for oral and
maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT. Dentomaxillofac
Radiol. 2006 Jul;35(4):219-26.
49. Maal et al. One Year postoperative hard and soft tissue volumetric changes after a
BSSO mandibular advancement. Int J Oral Maxillofac Surg 2012;41:1137-1145
50. Machado. CBCT Imaging - A boon to orthodontics. Saudi Den J. January 2015.
51. Mah et al. Three-dimensional craniofacial imaging. Am J Orthod Dentofacial
Orthop 2004;126:308-9
52. Maret et al. Effect of voxel size on the accuracy of 3D reconstructions with cone
beam CT. Dentomaxillofac Radiol. 2012 December; 41(8): 649–655
53. Moore et al. The contributing role of condylar resorption to skeletal relapse
following mandibular advancement surgery: Report of five cases. Journal of Oral and
Maxillofacial Surgery 1991;49:448-60
54. Motta et al. Superimposition of 3D cone-beam CT models in orthognathic surgery.
Dental Press J Orthod. 2010;15:39e1
55. Motta et al. Three-Dimensional Regional Displacements after Mandibular
Advancement Surgery: One Year of Follow-up. Journal of Oral Maxillofacial Surgery.
2011;69:1447-57
56. O’Ryan et al. Temporomandibular joint function and morphology: observation on
the spectra of normalcy. Oral Surgery Oral Medicine Oral Pathology 1984;58:272-79

79
57. Papadaki et al. Condylar Resorption. Oral Maxillofacial Surg Clin N Am
2007;19:223-234
58. Park et al. Effect of bimaxillary surgery on adaptive condylar head remodeling:
metric analysis and image interpretation using cone-beam computed tomography
volume superimposition. J Oral Maxillofac Surg 2012;70:1951-59
59. Pullinger and Hollender. Variation in condyle-fossa relationshipsaccording to
different methods of evaluation in tomograms. (Oral Surc. Oral Med. Oral Pathol.
62~719-727, 1986)
60. Rotskoff et al. Maintenance of Condyle-Proximal Segment Position in
Orthognathic Surgery. Journal of Oral Maxillofacial Surgery. 1991;19:2-7
61. Scarfe et al. Clinical applications of cone-beam computed tomography in dental
practice. J. Can. Dent. Assoc. 2006;72(1):75–80
62. Schendel et al. Results after mandibular advancement surgery: An analysis of 87
cases. Journal of Oral Maxillofacial Surgery. 1980;38:256
63. Sickels et al. Condylar Position with Rigid Fixation versus Wire Osteosynthesis of a
Sagittal Split Advancement. Journal of Oral Maxillofacial Surgery 1999;56:31-34
64. Strauss et al. A technique for Accurate Long-Term Follow-up of Segment
Positional Changes Following Sagittal Split Osteotomies. Journal of Oral Maxillofacial
Surgery 1993;51:815-16
65. Swennen et al. A cone-beam computed tomography triple scan procedure to
obtain a three-dimensional augmented virtual skull model appropriate for orthognathic
surgery planning. J Craniofac Surg. 2009. 20: 297–307.
66. Swennen et al. Three-Dimensional Treatment Planning of Orthognathic Surgery in
the Era of Virtual Imaging Gwen R.J. 2009 American Association of Oral and Maxillofacial
Surgeons J Oral Maxillofac Surg 67:2080-2092, 2009
67. Terajima et al. 3-dimensional method for analyzing the morphology of patients
with maxillofacial deformities. Am J Orthod Dentofacial Orthop. 2009 Dec;136(6):857-867.
68. Utt et al. A three-dimensional comparison of condylar position changes between
centric relation and centric occlusion using the mandibular position indicator. Am J
Orthod Dentofacial Orthop. 1995 Mar;107(3):298-308.
69. Van Vlijmen et al. Evidence supporting the use of cone-beam computed
tomography in orthodontics. J Am Dent Assoc. 2012 Mar;143(3):241-52
70. Will et al. Condylar Position Following Mandibular Advancement: Its Relationship
to Relapse. J Oral Maxillofac Surg 42578-588. 1984
71. Worms et al. Post-treatment Stability and Esthetics of Orthognathic Surgery.
Angle Orthodontics 1980;50:251-73
72. Xi et al. Validation of a novel semi-automated method for three-dimensional
surface rendering of condyles using cone beam computed tomography data. Int. J. Oral

80
Maxillofac. Surg. 2013; 42: 1023– 1029. # 2013 International Association of Oral and
Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved
73. Yang and Hwang. Change in condylar position in posterior bending osteotomy
minimizing condylar torque in BSSRO for facial asymmetry. J Craniomaxillofac Surg. 2014
Jun;42(4):325-32.
74. Yoon et al. Clinical changes of TMD and condyle stability after two jaw surgery
with and without preceding TMD treatments in class III patients. Maxillofac Plast
Reconstr Surg. 2015 Feb 21;37(1):9.
75. Zamora et al.

A study on the reproducibility of cephalometric landmarks when
undertaking a three-dimensional (3D) cephalometric analysis. Med Oral Patol Oral Cir
Bucal. 2012 Jul; 17(4): e678–e688.

Abstract (if available)

Abstract Background: Condylar displacement following orthognathic surgery has been related to post-surgical relapse. Although postoperative changes in condylar position have been reported in previous studies, no study has precisely quantified these variations in three dimensions (3D). The development of cone beam computed tomography (CBCT) has enabled the accurate measurement of changes in condylar position in three planes of space (x, y, z). ❧ Purpose: To quantify, in 3D, the amount and direction of condylar displacement relative to the glenoid fossa after bi-maxillary surgery. ❧ Materials and Methods: The sample consisted of 17 patients undergoing orthognathic surgery treated consecutively by one surgeon. The pre-surgical and 2-week post-surgical CBCT DICOM files were collected for each patient. The regions of interest in the temporomandibular joint complex were segmented and the pre- and post surgical condyles were superimposed using the glenoid fossa as the reference structure. Condylar translation and rotation were compared before and after surgery for each patient in three planes of space. ❧ Results: The average condylar displacement was 0.78 mm on x plane, -3.80 mm on y and 0.14 mm on z plane. As for rotation, the average movement was 0.06° on x plane, 0.30° on y and -0.27 on z. The only statistically significant movements were translation on Y plane and rotation on Z plane. ❧ Conclusion: Minimal changes in condyle position do occur immediately after bi-maxillary surgery and it is possible to accurately assess the amount and direction of this displacement in 3D.

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