Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4421_Библиотеки_им_академика_М_И_Перельмана.pdf
Orthognathic Surgical Considerations forObstructive Sleep Apnea
. Fig. 21.4 Adjustment of head orientation
309
21
nasopharynx, oropharynx, and hypopharynx, which is
the smallest portion in the anteroposterior direction and
lateral pharyngeal dimension in patients with OSA syndrome (OSAS). Furthermore, it is relatively straightforward to evaluate changes before treatment, providing a
baseline from which the patient’s response to treatment
may be gauged over time by superimposition of subsequent follow-up images [32].
21.2 Visualization oftheAirway Space
forVolumetric Analysis
To evaluate the upper airway space, CBCT images were
reconstructed using InVivo5 (Anatomage, San Jose, CA,
USA) in the form of DICOM les. After creating the
3D image of the entire raw dataset, Invivo5 facilitates an
assessment of the specic airway region of interest with
tools to separate and delete opaque areas corresponding to skin and bone (using the “Remove” function of
the volume render of the segmentation tool). The upper
border may be set as the plane across the superior part
of the atlas; the lower border may be set as the plane
crossing the lowermost point of the fourth cervical vertebra. Anteroposterior walls may be dened as the anatomical border of the pharynx. After adjusting opacity
threshold to −750 with the ne tuning bar, the nal 3D
image of each pharyngeal cavity was constructed using
the volume rendering function [31] (.
The 3D reconstructed image allows a detailed comparative evaluation of the pattern of the airway space.
For example, the airway space of non-OSAS group has
a more rounded or rectangular shape, while that of the
Fig.21.5).
patients with OSAS has a more elliptical or concave
shape [33]. Class III skeletal relationships are characterized by a wider and atter anteroposterior direction [31],
and, with advancing age, the airway space widens laterally to become more elliptical [34]. Airow resistance is
directly related to both the size and shape of the airway.
While the airway space may be large in some cases, its
winding path may detrimentally impact airow with
signicant resistance, ultimately impacting respiratory
function. Reconstructed 3D images may be exported as
an STL le and used to analyze the airway airow using
the nite-element study.
21.3 Airway Space Change andStability
Related toOrthognathic Surgery
21.3.1 Mandibular Setback andBimaxillary
Surgery
Skeletal Class III malocclusion may be accompanied by
the combination of a prominent mandible and retracted
maxilla or mandibular prognathism alone [19, 26, 35,
36]. To improve the skeletal discrepancy, orthognathic
surgery (mandibular setback or MMA) is recommended
to improve masticatory function and aesthetics [17]. In
orthognathic surgeries involving mandibular setback,
both preoperative and postoperative evaluation of the
airway space may be performed by CBCT. The advantage of CBCT is that the airway space may be reconstructed in 3D to provide a detailed visualization for
analysis (. Figs.21.6 and 21.7).
310
Y.-I. Kim et al.
21
. Fig. 21.5 3D image construction process of the pharyngeal cavity
Several studies report the correlation between the
change in airway space and orthognathic surgery [22,
23, 27, 28, 37–48]. Mandibular setback surgery for
a skeletal class III malocclusion may cause stenosis
of the upper airway space immediately after surgery
because it repositions the tongue posteriorly as the
mandible moves backward (. Fig.21.6). Some cases
have reported the occurrence of OSA due to a reduction in volume of the retrolingual and hypopharyngeal airway after mandibular setback and change in
position of the hyoid bone [17]. When the mandible is
retracted, the hyoid bone is repositioned downward,
and a posterior displacement of the tongue and soft
palate occurs. This movement eventually results in the
narrowing of the upper airway space in the anteroposterior and lateral directions [49]. In addition, relative
mean negative pressure decreases, as does pharyngeal
airway volume.
In contrast, Wenzel et al. [48] found decreased
nasopharyngeal volume following mandibular setback,
Orthognathic Surgical Considerations forObstructive Sleep Apnea
311
21
. Fig. 21.6 Mandibular setback in this case led to a reduction in total volume of 4.9cc and a reduction in minimum area of 81.2mm
which remained reduced over a long period of time. If
maxillary advancement is performed with mandibular
setback, the narrowing of the airway can decrease. In
2008, Degerliyurtet al [37]. showed the comparative airway changes between bimaxillary surgery and mandibular setback and suggested that bimaxillary surgery could
prevent airway stenosis. To some extent, the increased
volume of the airway at the nasopharyngeal level in
bimaxillary surgery compensates for the effect at the
hypopharyngeal level [41]. These reports suggest more
effort is needed to maintain a constant pharyngeal airow during the mandibular setback surgery [29]. Clearly,
3D imaging can adequately support airway assessments
for this purpose.
Depending on the type of orthognathic surgery
involving mandibular setback, there are conicting
reports on the degree of reduction and duration of retention in each region of the upper airway space. According
to Park etal. [19], Tselnik and Pogrel [27], Hochban [25],
Wenzel etal. [48], Holmberg etal. [39], Chung and Lee
etal. [50], and Lee et al. [29], there was no signicant
decrease in the nasopharyngeal space; however, the
width of oropharynx and hypopharynx decreased. In
these studies, mandibular setback caused repositioning
312
Y.-I. Kim et al.
21
. Fig. 21.7 Surgery involving both the maxilla and the mandible led to a 12-cc reduction in total volume and, a 128.2-mm reduction in
minimum area
of the tongue in the posteroinferior direction at the skeletal position so that changes of the airway width were
greater in the oropharynx and hypopharynx than in the
nasopharynx.
In contrast to the previous studies that showed that
the nasopharyngeal space remained almost unchanged
during the mandibular setback, Kim et al. [16] and
Wenzel etal. [48] reported a signicant decrease in the
nasopharynx after mandibular setback that remains
reduced over time. In the study by Kim etal. [16], a
reduction in the nasopharyngeal space was observed,
but this reduction was smaller than that of the oropharynx and hypopharynx. There are conicting results
regarding nasopharyngeal space reduction. When the
decrease in the three parts of the pharyngeal space were
compared, reduction in the oropharynx was found to
be most severe, followed by the hypopharynx and nasopharynx. Since the oropharynx is the closest to the posterior of the mandible and tongue, it is presumed to be
the most affected by surgical mandibular movement.
40,000.00
35,000.00
30,000.00
25,000.00
20,000.00
15,000.00
10,000.00
45,000.00
T0 T1
T2
ynx
ab
Orthognathic Surgical Considerations forObstructive Sleep Apnea
40,000.00
313
21
35,000.00
30,000.00
25,000.00
20,000.00
15,000.00
10,000.00
5,000.00
0.00
T0 T1
. Fig. 21.8 Short- and long-term changes in the airway space after
orthognathic surgery of Korean skeletal class III malocclusion
patients. Changes in the airway volume of the group with only mandibular setback are shown in plot A; changes in the airway volume of
the group with simultaneous maxillary advancement and mandibu-
T2
Similar results were obtained in a comparison
between mandibular setback only and bimaxillary
surgery with maxillary forward movement. Samman
etal. [26] reported a decrease in the oropharyngeal and
hypopharyngeal space and Cakarne et al. [35] found
an increase in nasopharyngeal space. Chen et al. [36]
reported changes in the upper airway space in both
short- and long-term follow-ups post-mandibular setback and bimaxillary surgery. The mandibular setback
group showed a signicant decrease in the widths of the
nasopharynx and hypopharynx in both short- and longterm follow-ups. After bimaxillary surgery, width of
the nasopharynx increased, and oropharynx and hypopharynx widths decreased during short-term follow-up
only. However, long-term follow-up showed no signicant spatial changes in the structures. In most cases,
maxillary advancement was performed simultaneously
with bimaxillary surgery, resulting in a decrease in the
amount of mandibular setback. Therefore, the duration of the decrease in the airway is not signicant when
compared to that of mandibular setback only.
It has been reported that the airway changes after
orthognathic surgery are sustained for long periods of
time and that a reduction in airway volume also persists. In addition, some research shows that the airway
changes occur temporarily during tissue re-adaptation.
Enacar etal. [24] reported postoperative changes in the
oropharyngeal space, reporting that the reduced area
of the oropharyngeal airway persisted for more than
18months. Studies by Kim etal. [16], Tselnik etal. [27],
and Hochban etal. [25] reported postoperative oropharyngeal width decreased and adapted to the reduced
dimensions during the follow-up period. Signicant
5,000.00
0.00
lar setback are shown in plot B. X-axis: T0 (preoperative), T1
(4.6months after surgery), T2 (1.4years after surgery). Y- axis: airway volume. The Y-axis (air volume) was measured in cubic millimeters (mm
3
) at the X-axis (baseline, T1, T2)
reductions in the hypopharyngeal space after surgery
suggest a functional readjustment of the hyoid bone,
tongue muscle, and neck muscle, leading to changes in
the airway space [51] (.
Few studies report the application of 3D upper airway
images, and even fewer report the relationship between
changes of the upper airway and post-surgical stability.
A study conducted by Park etal. [19] at Pusan National
University Dental Hospital (PNUDH) employed 3D
CBCT to evaluate how the upper airway changed after
orthognathic surgery in patients with skeletal Class III
deformities and to analyze the relationship between the
changes in the upper airway and post- surgical stability.
A total of 36 adult subjects were included (23 men, 13
women; mean age 22.97± 3.01 years; range 19 to 29)
who had been diagnosed with class III skeletal deformities and underwent surgical orthodontic treatment. As
an alternative approach to the analysis of the anatomical characteristics of the upper airway, the anteroposterior length (APL), largest transverse width (LTW), and
cross-sectional area (CSA) in ve planes and in four volumes were calculated for all subjects (.
Patients were divided into groups by type of orthognathic surgery performed: group A (n=20) underwent
mandibular setback sagittal split ramus osteotomy
(SSRO with rigid xation), and group B (n=16) underwent a LeFort I osteotomy with advancement and mandibular setback SSRO.A 3D CBCT examination was
performed at three stages: T0 (before surgery), T1 (an
average of 4.6months after surgery), and T2 (an average of 1.4years after surgery). While airway decreases
were observed in both groups, the oropharyngeal and
hypopharyngeal airways in group A showed signi-
Nasopharynx
Oropharynx
Hypophar
Total
Fig.21.8).
Fig.21.9).
314
Y.-I. Kim et al.
21
. Fig. 21.9 Upper airway measurements. Five planes for upper airway measurement: PNS-Vp, CV1, CV2, CV3, and CV4 planes
cantly decreased volumes 4.6 months post-procedure
(P<0.05) and these diminished airways had not recovered 1.4 years post-surgery. Group B demonstrated
post- surgical stability based on the APL of the hypopharyngeal. Group A, however, showed maxillary relapse
based on the cross-sectional area of the nasopharynx
correlated (P<0.05).
Several studies have insisted that with bimaxillary
surgery (compared with mandibular setback surgery),
the reduction effect of the mandibular setback is moderate [26, 36, 37, 52]. Results reported by Park et al.
are consistent with those ndings; however, in patients
who had excessive mandibular setback or who already
showed signs of sleep apnea (such as obesity, excessive
daytime sleepiness, and excessive snoring), other OSA
interventions should be considered before orthognathic
surgery is pursued [53]. Furthermore, a reduction in oropharyngeal and hypopharyngeal volume was observed
4.6 months after mandibular setback. This decreased
volume did not recover until 1.4years after surgery. The
bimaxillary surgery group showed decreased volume
of the oropharyngeal airway [19]. Long-term, 12-year
follow- up showed a reduction in the hypopharyngeal
airway, but the nasopharyngeal and oropharyngeal airways continued to decrease for 12years [17].
In conclusion, mandibular setback movement
reduces a part of the upper airway space in the short and
long term [18]. A study by Kim etal. [16] that evaluated
the amount of mandibular setback reported no signicant changes in the upper airway space when the amount
of retraction was less than 11mm–12mm; however, a
signicant change was observed when the amount of
retraction was 12mm or more. Thus, the amount of the
mandibular setback is the factor that affects the degree
of the change in the upper airway space. To clarify the
regional airway changes and duration and the relationship between the amount of mandibular setback and
change in the upper airway space, additional studies
should be performed.
21.3.2 Vertical Movement ofthe
Maxillomandibular Complex
Orthognathic surgery involving maxillary vertical correction is required in dolichocephalic patients with a skeletal
class III malocclusion, represented by long face syndrome
and a gummy smile. This skeletal discrepancy can be
resolved through vertical repositioning of the maxilla and
rotation and setback of the mandible, which is usually
accompanied by occlusal plane rotation (. Fig.21.10).
Although surgery that involves occlusal plane rotation
and vertical movement of the maxilla to relieve gummy
smile is commonly performed, most studies on upper
airway space change following orthognathic surgery are
either on procedures performed only on the mandible or
focused on the horizontal change in the maxilla. However,
a 2008 study by Kim etal. [54] set out to observe changes
in the vertical movement of the maxilla in 24 patients
(9 men, 15 women) with a mean age of approximately
Orthognathic Surgical Considerations forObstructive Sleep Apnea
315
21
. Fig. 21.10 Airway changes after orthognathic surgery with maxillary vertical movement (reduction in total volume of 1.2cc and reduc-
tion in minimum area of 13.8mm)
22years who underwent preoperative orthodontic treatment and surgery involving vertical movement of the
maxilla with a Le Fort I osteotomy and mandibular
setback. Cephalometric radiographs were taken preoperatively (T0), postoperatively (T1, just or within 2weeks
after surgery), and at 6-month follow- up (T2). The radiographs were compared using a paired t-test to show differences in the change in upper airway width based on the
vertical movement of the maxilla (. Fig.21.11).
The PAS(R) (starting point of the nasopharynx)
observed to be decreased after surgery (T1) (P<0.01),
however, showed an increase at 6-month follow-up (T2).
Swelling of the soft tissue from intubation during general anesthesia may cause the airway space to decrease
in the short term, but soft tissues are known to quickly
adapt and contract. The PAS region formed by the palatal plane (NL) showed a signicant increase at T1 and
T2 due to the vertical movement of the maxilla and the
anterior movement component; however, longer term
observation is necessary. PAS formed by the occlusal
plane (OL) increased at T1 and T2, which may be attributable to the change of the location of the tongue and
the soft palate. At T1, the soft palate increased in thickness, but at T2 was observed to be similar to the initial
316
Y.-I. Kim et al.
1) Linear measurements
Pharyngeal airway space width
PAS (R) :Dista nce-Pharyngeal airway spa ce be tween
PAS-1 and PNS
P AS (NL): Distance between PAS-2 and PNS
•
PAS (OL): Distance between PAS-3 and PAS-6
•
PAS (UT): Distance between PAS-4 and UT
•
•
PAS (ML): Distance between PAS-5 and TB
Skeletal change
•
Vertical PNS: Distance PNS-FH plane
Vertical ANS: Distance ANS-FH plane
•
Horizontal PNS: Distance PNS-N
•
perpendicular plane
21
. Fig. 21.11 Pharyngeal airway space points
thickness or decreased. The angle between the FH plane
and the soft palate increased at T2 and appeared to be
affected more by the anteroposterior movement of the
maxilla rather than the vertical movement. This change
likely results from a change in the maxillary anteroposterior position and the biological response to maintain
the airway space rather than the muscular relaxation
and constriction due to the maxillary vertical position
change.
Regression analysis revealed the change in the width
of the upper airway was not signicantly related to maxillary vertical movement. Mean superior movement of
the maxilla for bimaxillary surgery was observed to be
4.40±1.14mm, resulting in a non-signicant change to
the upper airway space. Therefore, biological adaptation
can take place naturally [54].
However, there are factors that limit maxillary
movement, which include the presence of anatomical structures, such as the nasal septum, and nasal
•
Horizontal ANS: Distance ANS-N
perpendicular plane
Horizontal Bpoint:Dista nceB-point-S
•
perpendicular plane
2) Angular measurements
•
FH-uvul ar angulation :Angle between FH
plane and PNS-UT
breathing habits [55]. Vertical-only movement of the
maxilla is rare in bimaxillary surgery; vertical movement coupled with advancement is more common. In
this study, about 50% of the vertical maxillary movement was also involved in maxillary advancement
[54]. More studies are needed to examine the changes
resulting from the maxillary superior posterior rotation or the maxillary superior movement. In addition,
further studies using 3D CT need to be done to understand the biological and functional aspects of the 3D
changes.
21.3.3 Maxillomandibular Setback
Some patients have both maxillary and mandibular
excess and a skeletal class III malocclusion with an acute
nasolabial angle. To resolve this maxillomandibular
skeletal problem, maxillary retraction can be an effec-
T0 T0T1 T1
nx
x
ab
Orthognathic Surgical Considerations forObstructive Sleep Apnea
12,000.00
317
21
10,000.00
8,000.00
6,000.00
4,000.00
2,000.00
0.00
. Fig. 21.12 Change in airway volume. Change in the airway vol-
ume with mandibular posterior movement of mandible a. Change in
the airway volume with posterior movement of maxilla (clockwise
tive treatment option. In addition, aesthetic results can
be achieved by performing a clockwise rotation of the
maxilla in patients with a recessed midface, at occlusal plane, and prominent chin with an acute nasolabial
angle [29]. Total maxillary setback surgery with or without clockwise rotation is often needed for the correction
of a class III malocclusion in Asians.
When maxillomandibular rotation is required and
both maxilla and mandible retraction are performed,
narrowing of airway and a decrease in airway volume
may occur. These types of maxillary movements can
cause a concomitant decrease in the airway volume.
The posterior movement of the maxilla can reduce the
airway volume—it not only adversely affects the nasopharyngeal airway, but also increases the amount of
posterior movement of the mandible.
Studies on the changes of the upper airway space
after two-jaw surgeries that involve the posterior impaction or setback of the maxilla are rare [56]. A 2013
study by Lee etal. [29] used CBCT to observe changes
in upper airway space volume in patients with class III
skeletal deformities. Patients in group A (n=24) under-
10,000.00
8,000.00
6,000.00
4,000.00
2,000.00
0.00
rotation) before surgery (T0) and 6 months after surgery (T1) b.
Y-axis volume (air volume) was measured in units of cubic millimeters (mm
3
) at each time point on the X-axis (Baseline, T1)
In group B, the upper airway volumes were narrowed by the maxillary and mandibular setback movement (APL on the CV1, CV2, CV3, and CV4 planes, the
LTW on the PNS-Vp, CV1, and CV3 planes, and the
CSA on the PNS-Vp, CV1, CV2, CV3, and CV4 planes
decreased after the surgery (P<0.05)). Maxillary movement is known to decrease airway volume by its deleterious effect on the nasopharyngeal airway and can
also increase the extent of movement from the mandibular setback. Upper airway volumes (including the
nasopharyngeal airway) were signicantly decreased in
group B in comparison to those in group A (P<0.01).
Additionally, APL, LTW, and CSA on the PNS-Vp
plane were signicantly different (P<0.05) [29]. While
movement from maxillary setback was shown to
increase the extent of the movement from a mandibular
setback, no patients developed OSA postoperatively.
Special consideration and caution should be exercised
when performing bimaxillary surgery on patients who
also have a large anteroposterior discrepancy, particularly in skeletal class III patients with a maxillary protrusion [29] (. Fig.21.13).
went mandibular setback surgery. Patients in group B
(n = 23) underwent bimaxillary surgery (mandibular
setback surgery and maxillary setback Le Fort I osteotomy) (. Fig.21.12 and . Table 21.1).
21.3.4 Maxillomandibular Advancement
(MMA)
Mandibular setback movement appeared to signicantly change the volumes of the oropharynx and hypopharynx, as well as a reduced volume of the APL, LTW,
and CSA on the CV1, CV2, and CV3 planes, respectively
(P<0.05). Signicant reductions were also observed in
the APL and CSA volume on the CV
plane (P<0.05).
4
Furthermore, group A’s oropharyngeal region was
observed to be signicantly decreased vs. group B’s
(P<0.05). These data appear consistent with those from
other studies [13, 22, 27].
Class II deformities with a mandibular deciency may be
treated with growth control or compromised treatment
if they are mild, but severe cases require orthognathic
surgery. In such cases, the type of surgery performed is
mainly mandibular advancement rather than maxillary
setback. Patients with mandibular retrognathism that
require orthognathic surgery often already have snoring
problems or OSA.In the 1970s, it was surmised that surgical protraction of the mandible would improve OSA
Nasophary
Oropharynx
Hypopharyn
318
Y.-I. Kim et al.
. Table 21.1 Comparison of airway changes between groups (group A: mandibular setback surgery; group B: bimaxillary
surgery); from Lee etal. [29] (2013)
Group A
n=24
Mean SD Mean SD P
PNS-Vp plane
APL (mm) 1.4 3.15 −2.42 6.49 0.008†
LTW (mm) 1.37 2.73 −4.23 9.35 0.004†
CSA (mm
CV
APL −2.51 2.17 −2.88 7.91 0.869
LTW −2.99 5.17 −2.22 6.43 0.906
CSA −74.42 79.56 −94.6 134.7 0.777
CV
APL −3.39 2.61 −2.52 7.17 0.906
LTW −5.32 4.98 −3.53 9.34 0.346
CSA −112.59 85.97 −82.21 119.44 0.081
CV
APL −2.84 2.64 2.61 4.44 0.715
LTW −1.74 3.48 −1.59 3.63 0.841
CSA −98 88.08 −52.53 101.19 0.138
CV
APL −4.54 3.95 −2.11 2.78 0.944
LTW −0.32 3.45 −1.58 5.16 0.154
CSA −35.37 80.89 −45.62 113.34 0.925
Volume (mm
Nasopharynx −555.03 2135.12 −1604.1 2616.34 0.675
Oropharynx −2345.36 2897.33 −2856.16 2415.32 0.868
Hypopharynx −2455.59 2244.85 −1313.34 2064.61 0.984
2
) 21.26 123.96 − 272 144.86 0.0006
plane
1
plane
2
plane
3
plane
4
3
)
Group B
n=23
21
*P<0.05
†P<0.01 (Mann-Whitney U test)
by improving the retropalatal and retrolingual dimension of the airway during protraction.
In 1983, Powell et al. [57] reported the rst case of
mandibular advancement for the treatment of OSA,
which was achieved by LeFort I and bilateral sagittal
split osteotomies. Mandibular advancement causes the
hyoid bone and tongue muscle to move forward because
the hyoid bone is attached by geniohyoid, suprahyoid,
anterior digastric, and mylohyoid muscles. The soft pal-
ate, tongue, and anterior pharyngeal tissues follow the
movement of the chin. MMA causes an increase in the
volume of the nasopharynx, oropharynx, and hypopharynx, resulting in an increase in the PAS [17]. In addition,
the minimum and mean cross-sectional areas of the
nasopharynx and the mean transverse diameter of the
oropharynx have also been reported to increase with the
procedure [58]. In conclusion, MMA is considered to be
a safe and highly effective treatment for OSA [59].