Keywords
Sagittal split ramus osteotomy - Le Fort osteotomy - Orthognathic surgery
INTRODUCTION
The goal of orthognathic surgery is to correct aesthetic and functional problems of
the jaw by reshaping the maxilla and mandible within a short period. Sagittal split
ramus osteotomy of the mandible is the most frequently used method for correcting
retrognathic and prognathic mandibles. Rigid fixation with plates or screws has been
widely favored for stabilization in the sagittal split ramus osteotomy [[1]]. However, this has several sequelae, including temporomandibular joint (TMJ) dysfunction
and postoperative relapse, as the proximal condylar segment is movable in 3 dimensions
after osteotomy of the mandibular ramus, which affects the condylar head position.
Many studies have investigated the factors that impact postoperative sequelae, including
a displaced condylar head, method and duration of intermaxillary fixation, magnitude
and direction of mandible movement, orthodontic treatment, incomplete bony union,
and masticatory function [[2]]. It is especially evident that a displaced condylar head is a major factor. Therefore,
it is important to maintain the anatomic position of the mandibular condyle within
the glenoid fossa during orthognathic surgery in order to reduce the relapse rate
and minimize the risk of TMJ dysfunction [[3]].
Numerous condylar repositioning methods have been reported, including a manual method,
rigid retention, navigation, and sonographic monitoring in order to limit the movement
of the condyle [[4]]. In addition, various means of evaluating the efficacy of these methods have been
proposed, which have been largely unsuccessful due to image distortion resulting from
the complex anatomic structure around the TMJ, irreproducible preoperative and postoperative
images, and multidirectional displacement of the condylar head [[5]]. Most condylar repositioning methods are 2-dimensional or require complex procedures
involving a long operation time and a highly trained surgeon.
This study aimed to introduce a new technique using a centric relation (CR) splint
to achieve a centric relationship and a simple 3-dimensional condylar repositioning
plate, validated by an objective evaluation method.
METHODS
The subjects were recruited from among patients who underwent surgery for skeletal
jaw deformities between January 2008 and December 2011. All of them were operated
on by the same surgeon. A total of 387 patients (199 male and 188 female) were followed
up in our outpatient clinic for more than 1 year. The average age of the patients
was 22.3 years (range, 17–52 years). The preoperative procedures included presurgical
orthodontics, final surgical treatment objectives, manufacture of CR splints, and
model surgery, including facebow transfer, impression model mounting, and manufacture
of final intermediate and centric occlusion splints.
The sequence of operative procedures was based on the preoperative planning and model
surgery. The main procedures performed were Le Fort I osteotomy and bilateral sagittal
split ramus osteotomy. First, a condylar repositioning plate was applied between the
maxilla and mandible after a CR splint was placed ([Fig. 1A]). The drilling holes for the plate were set above the Le Fort I osteotomy line and
behind the sagittal split ramus osteotomy vertical line. Two 4-mm screws were usually
utilized on each side to hold them firmly ([Fig. 1B, C]). After removing the condylar repositioning plate and CR splint, Le Fort I osteotomy
was usually performed first. An intermediate splint was then used to guide the movement
of one jaw relative to the other jaw. Four 4-hole L-type mini-plates were used for
the Le Fort I osteotomy. The remaining jaw was then repositioned based on the final
splint. Once the proximal segment of the mandible was repositioned, the condylar repositioning
plate was applied on the same drilling hole and bicortical screws 2 mm in diameter
and 12–18 mm long for bilateral sagittal split ramus osteotomy were used for rigid
fixation. The condylar repositioning plate was removed immediately after the rigid
fixation of the mandible [[6]].
Fig. 1 Operative procedure using condylar repositioning plate
(A) Three-dimensional condylar repositioning plate. (B) Intraoperative view of the
condyle repositioning plate. (C) Condyle repositioning plate on a skull model.
The following evaluation methods were used: (1) physical examination to detect preoperative
and postoperative TMJ dysfunction, (2) 3-dimensional computed tomography (3D-CT) and
oblique transcranial TMJ radiography to measure 3-dimensional condylar head movement
([Figs. 2], [3]), and (3) standard posteroanterior and lateral cephalometric radiography to identify
the amount of preoperative and postoperative movement of bony segments and the relapse
rate.
Fig. 2 Three-dimensional computed tomography
(A) Frontal view. (B) Lateral view. (C) Basal view. (D) Two-dimensional computed tomography,
transverse view. FZ, line between the frontozygomatic sutures; FRA, angle between
FZ and RVR; FLA, angle between FZ and LVR; RVR, right vertical ramus line; LVR, left
vertical ramus line; HL, line between the external acoustic meatus and inferior orbital
rim; LRA, angle between HL and PR; PR, posterior ramus line; RCA, right condylar axis
angle to MM'; LCA, left condylar axis angle to MM'; MM', line between the anterior
surfaces of the mastoid process.
Fig. 3 Oblique transcranial temporomandibular joint radiography
FS, parietotemporal fissure; EM, anterior eminence; X, superior point parallel to
the FS-EM line; FC1 distance, posterior joint space; FC2 distance, superior joint
space; FC3 distance, anterior joint space.
The postoperative 3D-CT and other radiographs were typically taken 3 months and 1
year after the operation during follow-up examinations at the outpatient clinic. The
radiologic findings were measured by two plastic surgeons and one orthodontist, and
the mean values were used for the statistical analysis.
On the frontal view of the 3D-CT images, the angles between the line between the frontozygomatic
sutures (FZ) and the vertical ramus line (VR) from both sides were measured. On the
lateral view of the 3-dimensional scan, the angles between the line between the external
acoustic meatus and inferior orbital rim (HL) and posterior ramus line (PR) were measured.
On the basal view of the 3D-CT, the angles between the line between the anterior surfaces
of mastoid process (MM') and the line connecting the medial and lateral ends of the
condylar head were measured, along with the distances between the MM' and the outer/inner
pole of the condyle on the 2-dimensional transverse view.
The landmarks were defined and abbreviated as follows: RVR, right vertical ramus line;
LVR, left vertical ramus line; FRA, the angle between FZ and RVR; FLA, the angle between
FZ and LVR; LRA, the angle between HL and PR; CC', the distance between the inner
condylar poles; RCA, the right condylar axis angle to MM'; LCA, the left condylar
axis angle to MM'; RLD, the distance between MM' to the outer pole of the right condyle;
RMD, the distance between MM' to the inner pole of the right condyle; LMD, the distance
between MM' to the inner pole of the left condyle; LLD, the distance between MM' to
the outer pole of the left condyle; FS, the parietotemporal fissure; EM, the anterior
eminence; and X, the superior point parallel to the FS-SE line. Additionally, the
posterior joint space (PJS) was defined as the FC1 distance, the superior joint space
(SJS) as the FC2 distance, and the anterior joint space (AJS) as the FC3 distance.
Skeletal relapse was measured by changes in the position of the supramentale (B),
pogonion (Pog), and menton (Mn) points, while dental relapse was measured by the changes
in the position of the tip of the upper and lower incisors.
Statistical analysis was performed with SPSS Ver. 22.0. (IBM Corp. Armonk, NY, USA).
A subgroup analysis was performed using the paired t-test. Statistical significance
was set at P<0.01.
RESULTS
The average period of postoperative intermaxillary fixation was only 1 day, with no
additional splint for occlusal stability. The average follow-up duration was 15.3
months. Of the 387 patients, 34 had a reciprocal click sound accompanied by TMJ pain,
78 had a closing click sound without any subjective symptoms, and the rest had no
symptoms before surgery. The patients with preoperative click sounds retained them
after surgery, while 6 patients exhibited a new click sound without any clinical symptoms.
In the preoperative 3D-CT scans, the average vertical axis angle was 82.73°±4.47°
(FRA) on the right and 83.32°±4.24° (FLA) on the left on the frontal view, 84.35°±5.49°
(LRA) on the right and 85.58°±5.04° (LLA) on the left on the lateral view, and the
average long-axis angle of the condylar head was 20.93°±5.55° (RCA) on the right and
19.89°±5.40° (LCA) on the left on the basal view. In the preoperative 2-dimensional
computed tomography images, the average vertical distances between the MM' and the
inner and outer pole of the right condyle (RMD and RLD, respectively) were 13.48±3.86
mm and 19.69±4.62 mm, respectively. The average vertical distances between the MM'
to the inner and outer pole of the left condyle (LMD and LLD, respectively) were 13.31±3.34
mm and 19.58±3.86 mm, respectively.
In the postoperative 3D-CT scans, the average vertical axis angle was 80.25°±4.74°
(FRA) on the right and 80.58°±4.30° (FLA) on the left on the frontal view, 81.26°±5.72°
(LRA) on the right and 81.87°±5.48° (LLA) on the left on the lateral view, and the
average long axis angle of the condylar head was 21.79°±6.04° (RCA) on the right and
21.21°±5.52° (LCA) on the left on the basal view. In the postoperative 2D-CT images,
the average vertical distances between the MM' and the inner and outer pole of the
right condyle (RMD and RLD, respectively) were 14.03±3.78 mm and 20.94±4.43 mm, respectively.
The average vertical distances between the MM' and the inner and outer pole of the
left condyle (LMD and LLD, respectively) were 14.40±3.24 mm and 20.86±3.82 mm, respectively.
In the long-term postoperative 3D-CT scans, the average vertical axis angle was 81.35°±4.55°
(FRA) on the right and 82.49°±4.21° (FLA) on the left on the frontal view, 83.24°±5.31°
(LRA) on the right and 84.36°±5.53° (LLA) on the left on the lateral view, and the
average long axis angle of the condylar head was 21.24°±5.58° (RCA) on the right and
20.72°±5.44° (LCA) on the left on the basal view. In the long-term postoperative 2D-CT
images, the average vertical distances between the MM' and the inner and outer pole
of the right condyle (RMD and RLD, respectively) were 13.56±3.83 mm and 20.40±4.92
mm, respectively. The average vertical distances between the MM' and the inner and
outer pole of the left condyle (LMD and LLD, respectively) were 13.84±3.18 mm and
20.18±3.79 mm, respectively. Significant differences were found between the preoperative
and postoperative measurements ([Table 1]).
Table 1
Mean measurements and statistical results of preoperative, 3-month postoperative,
and 1-year postoperative 3-dimensional and 2-dimensional computed tomography imaging
|
Measurement
|
T0 (mean)
|
T1 (mean)
|
TL (mean)
|
Paired t-test
|
|
T0–T1
|
T1–TL
|
T0–TL
|
|
T0, preoperative; T1, 3 months postoperative; TL, 1 year postoperative; FRA, angle
between FZ and RVR; FLA, angle between FZ and LVR; LRA, angle between HL and PR on
the right on the lateral view; LLA, angle between HL and PR on the left on the lateral
view; RCA, right condylar axis angle to MM'; LCA, left condylar axis angle to MM';
RLD, distance between MM' and the outer pole of the right condyle; RMD, distance between
MM' and the inner pole of the right condyle; LMD, distance between MM' and the inner
pole of the left condyle; LLD, distance between MM' and the outer pole of the left
condyle; FZ, line between the frontozygomatic sutures; RVR, right vertical ramus line;
LVR, left vertical ramus line; HL, line between the external acoustic meatus and inferior
orbital rim; PR, posterior ramus line; MM', line between the anterior surfaces of
the mastoid process.
*P<0.01.
|
|
FRA
|
82.73
|
80.25
|
81.35
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
FLA
|
83.32
|
80.58
|
82.49
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
LRA
|
84.35
|
81.26
|
83.24
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
LLA
|
85.58
|
81.87
|
84.36
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
RCA
|
20.93
|
21.79
|
21.24
|
< 0.01*
|
< 0.01*
|
0.03
|
|
LCA
|
19.89
|
21.21
|
20.72
|
< 0.01*
|
0.03
|
< 0.01*
|
|
RLD
|
19.69
|
20.94
|
20.40
|
< 0.01*
|
0.12
|
0.02
|
|
RMD
|
13.48
|
14.03
|
13.56
|
< 0.01*
|
< 0.01*
|
0.18
|
|
LMD
|
13.31
|
14.40
|
13.84
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
LLD
|
19.58
|
20.86
|
20.18
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
In addition, the average distance at the AJS was 2.48±0.41 mm on the right and 2.32±0.34
mm on the left, the average distance at the SJS was 2.32±0.39 mm on the right and
2.40±0.36 mm on the left, and the average distance at the PJS was 2.35±0.37 mm on
the right and 2.43±0.41 mm on the left in the preoperative oblique transcranial TMJ
radiographs. In the postoperative oblique transcranial TMJ radiography, the average
distances at the AJS were 2.25±0.41 mm on the right and 2.12±0.38 mm on the left,
2.66±0.37 mm on the right and 2.68±0.43 mm on the left at the SJS, and 2.73±0.41 mm
on the right and 2.76±0.40 mm on the left at the PJS. In the long-term postoperative
oblique transcranial TMJ radiography, the average distance was 2.43±0.38 mm on the
right and 2.29±0.36 mm on the left at the AJS, 2.46±0.34 mm on the right and 2.50±0.37
mm on the left at the SJS, and 2.46±0.37 mm on the right and 2.52±0.36 mm on the left
at the PJS. Statistically significant differences were found between the preoperative
and postoperative measurements ([Table 2]).
Table 2
Mean distance of joint space on oblique transcranial radiographs
|
Measurement, mm
|
T0 (mean)
|
T1 (mean)
|
TL (mean)
|
Paired t-test
|
|
T0–T1
|
T1–TL
|
T0–TL
|
|
T0, preoperative; T1, 3 months postoperative; TL, 1 year postoperative; AJS, anterior
joint space; (R), right side; (L), left side; SJS, superior joint space; PJS, posterior
joint space.
*P<0.01.
|
|
AJS (R)
|
2.48
|
2.25
|
2.43
|
< 0.01*
|
< 0.01*
|
0.02
|
|
AJS (L)
|
2.32
|
2.12
|
2.29
|
< 0.01*
|
< 0.01*
|
0.34
|
|
SJS (R)
|
2.32
|
2.66
|
2.46
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
SJS (L)
|
2.40
|
2.68
|
2.50
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
PJS (R)
|
2.35
|
2.73
|
2.46
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
|
PJS (L)
|
2.43
|
2.76
|
2.52
|
< 0.01*
|
< 0.01*
|
< 0.01*
|
Standard anteroposterior and lateral cephalic radiography scans were performed in
order to analyze 3-dimensional bony movement and relapse. The reference points were
the sella turcica (S), nasion (N), B, Pog, Mn, and the vertical reference plane (VP).
The VP was orthogonal to the horizontal reference plane (HP), which was rotated 7°
clockwise from the line connecting S and N. The distances from VP to Po and Mn were
designated as hPo and hMn, respectively. The distances from N to the projections of
Po and Mn onto the VP were designated as vPo and vMn, respectively.
In the preoperative images, the mean SNB angle was 81.34°±6.24°, hPo was −2.95±14.62
mm, hMn was −10.34±14.83 mm, vPo was 126.72±8.66 mm, and vMn was 134.31±8.95 mm. In
the postoperative images, the mean angle was 78.04°±4.85°, hPo was −8.45±10.91 mm,
hMn was −14.98±11.27 mm, vPo was 125.97±7.89 mm, and vMn was 132.74±7.94 mm. In the
long-term postoperative images, the mean angle was 78.31°±4.85°, hPo was −8.22±10.77
mm, hMn was −14.58±11.74 mm, vPo was 125.54±7.56 mm, and vMn was 132.38±7.76 mm.
A relapse rate of 0.3% was observed in the coronal plane, while a relapse rate of
2.8% was observed in the sagittal plane. This cannot be distinguished from the dental
relapse rate in orthodontic treatment ([Table 3]). The condylar repositioning plate was unable to fully prevent the movement of the
condylar head, but the relapse rate was minimized. This implies that the movement
of the condylar head was controlled within tolerable limits.
Table 3
Changes in landmarks on lateral cephalic radiographs
|
Measurement, mm
|
T0 (mean)
|
T1 (mean)
|
TL (mean)
|
Paired t-test
|
|
T0–T1
|
T1–TL
|
T0–TL
|
|
The reference points were the sella turcica (S), nasion (N), supramentale (B), pogonion
(Pog), menton (Mn), and the vertical reference plane (VP). The VP was orthogonal to
the horizontal reference plane (HP), which was rotated 7° clockwise from the line
connecting S and N. The distances from VP to Po and Mn were designated as hPo and
hMn, respectively. The distances from N to the projections of Po and Mn onto VP were
designated as vPo and vMn, respectively.
T0, preoperative; T1, 3 months postoperative; TL, 1 year postoperative.
*P<0.01.
|
|
SNB
|
81.34
|
78.04
|
78.31
|
< 0.01*
|
0.05
|
< 0.01*
|
|
hPo
|
–2.95
|
–8.45
|
–8.22
|
< 0.01*
|
0.45
|
< 0.01*
|
|
hMn
|
–10.34
|
–14.98
|
–14.58
|
< 0.01*
|
0.50
|
< 0.01*
|
|
vPo
|
126.72
|
125.97
|
125.54
|
0.21
|
0.08
|
0.04
|
|
vMn
|
134.31
|
132.74
|
132.38
|
0.01
|
0.05
|
< 0.01*
|
DISCUSSION
Many clinicians are concerned that rigid internal fixation can induce significant
changes in the position of the condyle.
Although the use of condylar positioning devices (CPDs) seems reasonable from this
point of view, no critical evaluation of their use is currently available. In particular,
the effects of a condylar repositioning plate on condylar position and relapse have
never been studied in detail. In a review by Costa et al. of the English-language
literature since 1990, only 6 papers comparing the use of CPDs with traditional methods
were found since a comprehensive review on the use of CPDs in orthognathic surgery
was published in 1994 by Ellis [[4]
[7]].
To summarize these 6 studies, the outcomes of 141 patients with CPDs were compared
with those of 112 patients treated using conventional manual repositioning. Three
studies supported the use of CPDs, 1 study supported the use of CPDs only in patients
with temporomandibular disorders (TMDs), and 2 studies did not support the use of
CPDs because they failed to improve skeletal stability or TMJ function, irrespective
of the skeletal deformities treated [[4]
[8]
[9]
[10]
[11]
[12]
[13]].
In our study, for the determination of acceptable patient outcomes and patient suitability
for the procedure, we used broader criteria than those used in previous studies of
orthognathic surgery that used only simple numeric criteria. The criteria took into
account the patient's aesthetic requirements as the most important factor, followed
in order by morphological esthetics, jaw deformities not being overcome by correction,
and asymmetry exceeding 3 mm and 3°. In order to statistically verify the outcomes
with multiple variables, a large sample size and a sufficient follow-up period were
incorporated into the study design.
With respect to outcome evaluation, X-ray based methods have been used frequently,
and CT-based methods are also used. Accordingly, we used both X-ray and CT imaging.
The present study was not designed as a comparative study between a group that used
CRP and a group that did not use CRP. Instead, it was a study of the usefulness of
a novel method of CRP design and placement, in contrast to the overly complicated
conventional methods currently in use. Now that we have shown that this novel method
was successful and not time-consuming, a future study is being planned to compare
this group to those who did not use a CRP.
The time required in using a CRP was not measured each time, but it generally took
5–10 minutes for the first CRP and 1–2 minutes to fix the distal segment to the proximal
segment and to fix the sagittal split ramus osteotomy. This occurs because the proximal
segment is fixed to the upper jaw, meaning that it is more stable than fixation without
a CRP, which consequently shortens the time for fixation to the lower jaw. Therefore,
it is believed that this novel method has virtually no effect on operative time. However,
it should be mentioned that the CR splint must be produced prior to the surgery, which
requires approximately 20–30 minutes.
The key goal of this article was to establish the usefulness of using a CRP. Although
various factors are involved, we analyzed a large number of patients treated by a
single surgeon when studying the effects of the CRP, in order to link measureable
outcomes to the effects of the CRP. Of course, this study has limitations, but to
study all the factors that could affect this operation would be very difficult. Accordingly,
the present study aimed to clarify the effects of CRP as meaningfully as possible.
Controversy exists about the appropriate management of patients with preexisting TMDs
who require orthognathic surgery for the correction of malocclusion and jaw deformities.
Two significantly different philosophies exist: although Wolford et al. [[14]] contended that orthognathic surgical procedures help in the reduction of TMD dysfunction
and symptoms, Cottrell et al. [[15]] showed that orthognathic surgery in such patients caused further deleterious effects
on the TMD and thus worsened the symptoms and dysfunction after surgery. The latter
philosophy proposes surgical management of the TMD pathology as an initial separate
procedure or one that may be performed concomitantly with orthognathic surgery when
indicated [[14]]. However, a retrospective analysis has suggested that orthognathic surgery itself
improves the symptoms of TMD. In that analysis, 53% of patients undergoing orthognathic
surgery had signs and/or symptoms of TMD and 78% of those patients reported an improvement
in symptoms after surgery [[16]]. These findings are, however, not applicable to this study because the patients
had no clinical problems and were accustomed to a symptom-free TMJ.
In this study, the effect of the condylar repositioning plate on condylar position
and relapse was evaluated by the paired t-test and regression. The condylar repositioning
plate could not entirely prevent the movement of the condylar head, but did minimize
the relapse rate according to our statistical analysis. This implies that the condylar
head movement was within tolerable limits.
Although some researchers do not support the use of CPDs, their main objection is
not the precision of such devices, but rather the amount of time that they add to
procedures. Once less time-consuming methods are available, there are likely to be
few objections to the use of CPDs. Our condylar repositioning method using a CR splint
and mini-plate in orthognathic surgery was simple and effective in patients suffering
from skeletal jaw deformities. The CT scans, transcranial TMJ radiographs, and cephalometric
radiographs all confirmed that condylar head movement was within acceptable limits.
Therefore, we believe that this method is effective and reliable.
