These include the use of burs, saws, piezosurgical devices, blunt or sharp chisels, ...... the following risk factors: females with mandibular retrognathia associated with an ...... Additionally, patients with a compromised medical status, when ...... Oral & Maxillofacial Surgery Clinics of North America ...... Liang KY, Zeger SL.
2012 | School voor Levenswetenschappen
DOCTORAATSPROEFSCHRIFT
On complications of Orthognathic Surgery Proefschrift voorgelegd tot het behalen van de graad van doctor in de biomedische wetenschappen, te verdedigen door: De transnationale Universiteit Limburg is een uniek samenwerkingsverband van twee universiteiten uit twee landen: de Universiteit Hasselt en Maastricht University. De opleidingen informatica/kennistechnologie, statistiek en biomedische wetenschappen/moleculaire levenswetenschappen zijn reeds ondergebracht in dit samenwerkingsverband. De bacheloropleiding in de rechten is een gezamenlijk initiatief van de Universiteit Hasselt, Maastricht University en de K.U.Leuven. Ook in andere wetenschapsdomeinen wordt gezocht naar samenwerking met andere universiteiten.
www.uhasselt.be Universiteit Hasselt | Campus Diepenbeek Agoralaan | Gebouw D | BE-3590 Diepenbeek T + 32(0)11 26 81 11
www.unimaas.nl Postbus 610 | NL-6200 MD Maastricht T + 31(0)43 388 222
Constantinus Politis Promotoren: prof. dr. Marjan Vandersteen prof. dr. Ivo Lambrichts
2012 | School voor Levenswetenschappen
DOCTORAATSPROEFSCHRIFT
On complications of Orthognathic Surgery Proefschrift voorgelegd tot het behalen van de graad van doctor in de biomedische wetenschappen, te verdedigen door:
Constantinus Politis Promotoren: prof. dr. Marjan Vandersteen prof. dr. Ivo Lambrichts
D/2012/2451/25
Good judgement comes from experience. Experience comes from bad judgement.
MEMBERS OF THE JURY
Prof.dr. J-M Rigo, Universiteit Hasselt, Diepenbeek, Belgium, Chairman Prof.dr. M. Vandersteen, Universiteit Hasselt, Diepenbeek, Belgium, Promotor Prof.dr. I. Lambrichts, Universiteit Hasselt, Diepenbeek, Belgium, Promotor Prof.dr. K.J. Van Zwieten, Universiteit Hasselt, Diepenbeek, Belgium Prof.dr. E. Fossion, Emeritus, Universiteit Leuven, Leuven, Belgium Prof.dr. P.J.W. Stoelinga, Emeritus, Radboud University Nijmegen, Nijmegen, the Netherlands Prof.dr. G. R.J. Swennen, Medizinische Hochschule Hannover, Germany and AZ St. Jan Bruges, Belgium Dr. Neil Heath, Honorary Clinical Senior Lecturer, Dental School, University of Glasgow and NHS Consultant
I
TABLE OF CONTENTS
Table of Contents
I
List of Figures
IX
List of Tables
XV
List of Abbreviations
XX
Chapter 1.
Introduction
1
Chapter 2.
A critical appraisal of the literature on complications of orthognathic surgery
9
2.1.
Errors in diagnosis or treatment planning
10
2.2.
Presurgical orthodontic errors
11
2.3.
Problems with model surgery and splint fabrication
12
2.4.
Intraoperative complications
13
2.4.1.
Sagittal Split Osteotomy
13
2.4.2.
Genioplasty
14
2.4.3.
Le Fort I osteotomy
14
2.5.
Reoperation - reintubation
16
2.6.
Death
16
2.7.
Blood transfusion
16
2.8.
Vascular complications
17
2.9.
Infections
18
2.10.
Trigeminal sensory deficit
19
2.11.
Trigeminal neuropathic pain
24
2.12.
Autonomic nerve dysfunction
25
2.13.
Unusual complications
25
2.14.
Velopharyngeal function - speech
26
2.15.
Temporomandibular joint dysfunction
26
2.16.
Condylar resorption
28
2.17.
Muscular dysfunction chewing ability
29
II 2.18.
Relapse
30
2.19.
Patient dissatisfaction
44
2.20.
Postoperative complication classification
46
2.21.
Guidelines and evidence in orthognathic surgery
47
2.22.
Conclusions
47
Chapter 3.
Aims and questions
48
Chapter 4. 4.1.
Predicted versus executed surgical orthognathic Summary
55 56
4.2.
Introduction
57
4.3.
Materials and methods
57
4.4.
Statistical methodology
58
4.5.
Results
59
4.6.
Discussion
66
4.7.
Conclusion
72
4.8.
Acknowledgements
72
Chapter 5.
Lateral cephalometry changes after SARPE
73
5.1.
Summary
74
5.2.
Introduction
74
5.3.
Materials and methods
75
5.4.
Statistical methodology
77
5.5.
Results
77
5.5.1.
Exploratory Data Analysis
78
5.5.2.
Student’s paired t-test
78
5.5.3.
PP-SN Plane angle
80
5.5.4.
Regression analysis
82
5.5.5.
U1-PP AND U1-SN Plane angles
83
5.6.
Discussion
85
5.7.
Conclusion
86
III
Chapter 6.
CBCT-based predictability of attachment of the neurovascular bundle to the proximal segment of the mandible during sagittal split osteotomy
89
6.1.
Summary
90
6.2.
Introduction
90
6.3.
Materials and methods
92
6.3.1.
Study design
92
6.3.2.
CBCT scanning
92
6.3.3.
Assessment of IAN canal position on CBCT images
93
6.3.4.
Clinical assessment of nerve attachment
94
6.4.
Statistical methodology
95
6.5.
Results
96
6.5.1.
Sample description
96
6.5.2.
Effect of measured variables on nerve attachment to the mandible
98
6.5.3.
Predictive ability of Nerve to Inner BC and Nerve to Inner IC distances
99
6.5.4.
ROC curve
100
6.5.5.
Average Probability
101
6.6.
Discussion
103
6.7.
Anterior vertical cut
103
6.8
Conclusion
104
Chapter 7.
Self-reported hypoesthesia of the lower lip after sagittal split osteotomy
105
7.1.
Introduction
106
7.2.
Materials and methods
106
7.2.1.
Patients
106
7.2.2.
Surgery
107
7.2.3.
Data collection
107
7.2.4.
Statistical analysis
109
7.3.
Results
109
7.3.1.
Descriptive statistics
109
IV 7.3.2.
Correlation and regression statistics
114
7.4.
Discussion
119
7.4.1.
Correlation between patient's subjective and assessor's objective assessment of the sensitivity of the lower lip and chin after sagittal split osteotomy of the mandible
119
7.4.2.
Incidence
120
7.4.3.
Risk factors
121
7.4.4.
Follow-up period
125
7.5.
Conclusion
125
7.7.
Clinical significance
125
7.8.
Acknowledgement
125
Chapter 8.
Occurrence of bad splits during sagittal split osteotomy
126
8.1.
Summary
127
8.2.
Introduction
128
8.3.
Materials and methods
128
8.4.
Operative technique
129
8.5.
Statistical methodology
134
8.6.
Results
134
8.7.
Discussion
138
8.8.
Conclusion
140
Chapter 9.
Anaesthesia of the inferior alveolar and lingual nerves following subcondylar fractures of the mandible
141
9.1.
Summary
142
9.2.
Introduction
142
9.3.
Materials and methods
142
9.4.
Statistical methodology
143
9.5.
Results
143
9.6.
Morphometric measurements
150
9.7.
Literature review
157
9.8.
Discussion
161
9.9.
Conclusion
163
V
Chapter 10.
Neuropathic pain after orthognathic surgery
164
10.1.
Introduction
165
10.2.
Materials and methods
165
10.3.
Results
165
10.4.
Discussion
170
10.5.
Conclusions
172
Chapter 11.
Plate removal following orthognathic surgery
173
11.1.
Summary
174
11.2.
Introduction
174
11.3.
Materials and methods
176
11.4.
Operative technique
176
11.5.
Statistical methodology
178
11.6.
Results
178
11.7.
Discussion
181
11.8.
Comparison with plate removal after mandibular fractures
183
11.9.
Conclusion
184
Chapter 12.
Healing of the lower border of the mandible after BSSOadvancement
185
12.1.
Summary
186
12.2.
Introduction
187
12.3.
Materials and methods
191
12.3.1.
Assessment of magnitude of advancement during SSO on a panoramic radiograph
191
12.3.2.
Assessment of the mandibular lower border defects
191
12.4.
Statistical methodology
192
12.5.
Results
192
12.5.1.
Sample description
192
12.5.2.
Logistic generalized estimating equations (GEE) model
193
12.6.
Discussion
195
VI 12.7.
Conclusion
196
Chapter 13.
Visibility of mandibular canal on panoramic radiograph after bilateral sagittal split osteotomy
199
13.1.
Abstract
200
13.2.
Introduction
201
13.3.
Materials and methods
203
13.3.1.
Exclusion criteria for patients in this study
203
13.3.2.
Surgical method
204
13.3.3.
Radiological method
204
13.3.4.
Statistical analysis
205
13.4.
Results
205
13.5.
Discussion
211
13.6.
Conclusion
214
13.7
Acknowledgement
214
Chapter 14.
Bloodloss and transfusion need in orthognathic surgery
215
14.1.
Summary
216
14.2.
Introduction
216
14.3.
Research questions
217
14.4.
Literature review: selection criteria
217
14.5.
Inclusion criteria
218
14.6.
Exclusion criteria
218
14.7.
Search results
219
14.8.
Meta-analysis or systematic review
219
14.9.
Aggregation of data
220
14.10.
Measurement of blood loss
222
14.11.
Measurement of duration of surgery
223
14.12.
Duration of surgery and blood loss
223
14.13.
Hypotension
224
14.14.
Advantages of controlled hypotension
225
14.15.
Minimising perioperative bleeding
226
VII 14.16.
Excessive blood loss
227
14.17.
Criteria for transfusion
227
14.18.
Risk of transfusion
228
14.19.
Preoperative donation of autologous blood
228
14.20.
Mandibular surgery and transfusion need
229
14.21.
Le Fort I single-jaw surgery without additional complex procedures
231
14.22.
Le Fort I single-jaw surgery with additional procedures
236
14.23.
Bimaxillary surgery without additional complex procedures
239
14.24.
Bimaxillary surgery with additional complex procedures
247
14.25.
Conclusions
249
Chapter 15.
Obstructive airway compromise in the early postoperative period after orthognathic surgery
251
15.1.
Summary
252
15.2.
Introduction
252
15.3.
Materials and methods
253
15.3.1.
Technique of BSSO
254
15.3.2.
Technique of Chin osteotomy with oscillating saw
254
15.3.3.
Technique of Chin osteotomy with piezo-surgical unit
254
15.4.
Results
256
15.5.
Discussion
257
15.6.
Conclusion
260
Chapter 16.
Life-threatening haemorrhage after 750 Le Fort I osteotomies and 376 SARPE procedures
261
16.1.
Summary
262
16.2.
Introduction
262
16.3.
Materials and methods
263
16.4.
Results
264
16.5.
Discussion
266
16.6.
Conclusion
271
16.7.
Acknowledgements
271
VIII
Chapter 17.
General discussion and summary
272
17.1.
Errors in prediction of surgical procedure
273
17.2.
Intraoperative complications
274
17.3.
Postoperative complications
276
17.4.
General conclusion
278
17.5.
Practical recommendations
279
Chapter 18.
Nederlandse samenvatting
281
18.1.
Prechirurgische fase
282
18.2.
Peroperatieve fase
282
18.3.
Postoperatieve fase
283
18.4.
Algemeen besluit
285
18.5.
Praktische aanbevelingen gebaseerd op dit proefschrift
286
Reference List
288
Curriculum Vitae
323
Bibliography
324
Dankwoord
328
IX
LIST OF FIGURES
Figure 1.1
Schematic drawing of a bimaxillary osteotomy consisting of a Le Fort I osteotomy in the upper jaw and a sagittal split osteotomy in the lower jaw.
3
Figure 1.2
In surgically assisted rapid palatal expansion of the upper jaw (SARPE) we use the same bone cuts as in a routine Le Fort I osteotomy with in addition a midline split of the maxilla. The same technique of pterygomaxillary disjunction is used. No downfracture of the maxilla is performed.
4
Figure 1.3
Schematic drawing of a bilateral sagittal split osteotomy with advancement of the lower jaw. The left side of the mandible has been stabilized with two miniplates. At the lingual site of the right lower jaw the horizontal cut at the medial side of the ascendic ramus is depicted with the horizontal cut ending directly behind the lingula (Nomina Anatomica: Lingula Mandibulae).
5
Figure 5.1
Cephalometric tracing illustrating measurements
76
Figure 5.2
Superimposition of lateral cephalometry before and after surgery shows that the PP-SN plane angle is increased . This increase is statistically significant (P = 0.003*)
79
Figure 5.3
Boxplot for PP-SN angle pre-SARPE and post-SRPE by gender
80
Figure 5.4
Boxplot for PP-SN angle pre-surgery and post-surgery by occlusion
81
Figure 5.5
Scatter plot of age and PP-SN post surgery
82
Figure 5.6
Scatter plot of PP-SN before and after surgery
82
Figure 5.7
Box plot of the change of U1-SN angle before and after SARPE
84
Figure 5.8
Box plot of the change in U1-PP angle before and after SARPE
84
Figure 6.1a
CBCT image of a patient
91
Figure 6.1b
Series of CBCT images from a single patient with tracing of the course of the inferior alveolar nerve .
91
Figure 6.2
Cross-sectional images of the mandible depicting different locations of the inferior alveolar nerve
92
Figure 6.3
Panoramic radiographic image of the mandible. The dotted lines represent locations where cross-sectional images were obtained
93
Figure 6.4
Cross-sectional images of the mandible showing measured linear distances
94
X Figure 6.5
Predictive ability of the distances from Nerve to Inner BC and Nerve to Inner IC after correction for confounding factors (ROC curve)
100
Figure 6.6
Predicted probability curve that nerve is free by distance (mm).
101
Figure 6.7
Three-dimensional plot of the predicted probability that the interior alveolar nerve is free.
101
Figure 6.8
Three-dimensional plot of the predicted probability freeing the interior alveolar nerve surgically.
102
Figure 7.1
Sites at which the measurements were made on the preoperative CBCT-scan. The distances between mandibular canal and the cortical outer or lower border were measured both at the mesial side of the first molar (M1) and at the distal side of the second molar (M2)
108
Figure 7.2
depicts the distances which were measured (in mm) from the border of the mandibular canal (MC) to both the inner and outer border of the buccal plate (horizontal measurement) and the lower border of the mandible (vertical measurement)
108
Figure 7.3
After the sagittal split, the osteotomy site is inspected. Most of the times the nerve resides at the tooth baring segment. Sometimes the IAN resides in the buccal plate (a). Then the nerve needs detachment from the proximal fragment. This is realised with either non-surgical means (b) or surgical with cutting instruments, usually a piezzo surgical intervention (c)
109
Figure 7.4
Predicted odds ratios for hypoesthesia (Right-Side) versus age-genioplastly
117
Figure 7.5
Predicted probabilities for hypoesthesia (Left-Side) versus age-genioplastly
118
Figure 8.1
Outline of the bone cuts, made with the drill.
130
Figure 8.2
Perioperative pictures after finishing the inferior border cut during SSO.
130
Figure 8.3
Illustration of a favourable split
131
Figure 8.4
Split creeping up to the buccal side
132
Figure 8.5a
Illustration of the proximal fragment of the mandible including the condyle, view from above.
133
Figure 8.5b
Hunsuck - Epker modification of the sagittal split
133
Figure 8.5c
Obwegeser-split of the ascending ramus
134
Figure 8.6
Bad split including the buccal plate as a separate bone fragment
135
Figure 8.7
Buccal plate fracture, view from above
135
of
XI Figure 8.8a+b
Panoramic radiography of salvage procedures in bad splits.
136
Figure 8.9
Distribution of sagittal split osteotomies and bad splits according to the year of surgery
137
Figure 8.10
Distribution of bad splits relative to the number of SSOs performed per age-group
139
Figure 8.11
Unfavourable splits, not considered to be bad splits
140
Figure 9.1
Histogram of the age distribution of patients with condylar and/or subcondylar fractures
144
Figure 9.2
Case 1. Panoramic radiograph of a subcondylar fracture at the right side. Image was acquired shortly after the trauma. (R: right side)
145
Figure 9.3
Case 1.CBCT scan; frontal view of the subcondylar fracture before closed reduction was performed. The condylar head remains in contact with the skull base.
145
Figure 9.4
Case 1. CBCT-scan of the subcondylar fracture after closed reduction. The axial view illustrates the amount of anterior displacement.
146
Figure 9.5
Case 1: Fusion of two axial sections: the displaced condyle (Co) (upper arrow) is in close vicinity to the foramen ovale (FO) (horizontal arrow).
146
Figure 9.6
Case 2. Panoramic radiograph of the subcondylar fracture. Image was acquired shortly after the trauma.
148
Figure 9.7
Case 2. CBCT scan of a subcondylar fracture. Frontal section, right subcondylar area.
148
Figure 9.8
Case 2. CBCT scan of a subcondylar fracture. Axial slice.
149
Figure 9.9
Case 2. MRI scan of a subcondylar fracture. Frontal slice.
149
Figure 9.10
Case 2. Panoramic radiograph of a subcondylar fracture. Postoperative view.
150
Figure 9.11
T-test results. Agreement Plot compares the left and right measurements of the fo_ variable for each skull.
152
Figure 9.12
T-test results. Agreement Plot compares the left and right measurements of the pt_ variable for each skull.
153
Figure 9.13
Dry human skull study; skull base. An example of a short pterygoid plate.
154
Figure 9.14
Dry human skull study; skull base. An example of a very large pterygoid plate.
154
Figure 9.15
Dry human skull study; skull base. The relationship between the foramen ovale and the pterygoid plate illustrates how the nerve can be compressed against this enlarged pterygoid plate.
155
XII
Figure 9.16a
Dry human skull study; skull base; lateral view of the proximity between the foramen ovale and the enlarged lateral pterygoid plate.
155
Figure 9.16b
Dry human skull study; skull base; axial view of the proximity between the foramen ovale and the enlarged lateral pterygoid plate.
156
Figure 9.17a
Illustrations of a potential compression. Posterior view.
mechanism
for
nerve
156
Figure 9.17b
Illustrations of a potential compression. Lateral view.
mechanism
for
nerve
156
Figure 9.18
Cadaver dissection specimen displays the IAN and LN.
157
Figure 10.1
Patient 3 underwent a BSSO advancement with a large widening at the left side, causing peroperative visible IAN elongation damage. The final occlusion was excellent. The wide gap was not filled with a bone graft of any kind, ultimately resulting in a large defect
167
Figure 10.2
Patient 4 with intra-operative difficult detachment of the IAN from the proximal fragment, but otherwise uneventful bony healing. Successive panoramic radiographs show a narrowing of the mandibular canal at the left side.(Top: Preoperative; Middle: Immediate postoperative; Below: 1 year postoperative panoramic radiographs)
168
Figure 10.3
Patient 5 with uneventful BSSO with undamaged nerve exposed in the osteotomy site at both sides, left and right. Due to the large osteotomy gap a bone substitute was used (Hydroset ®, Stryker). In the postoperative course osteomyelitis and sequestration of bone was noticed. Surgery to remove the foreign bodies (miniplates, Hydroset ®) resulted in hypoesthesia. No pseudarthrosis developed
169
Figure 10.4
Patient 6 with a large BSSO advancement in whom the miniplates were removed after 3 months because of infection. A subsequent pseudarthrosis became evident by upward rotation of the proximal fragment
170
Figure 11.1a
Panoramic radiography showing miniplates in place after a bimaxillary operation. Use of two "long 4-hole plates" in the lower jaw.
177
Figure 11.1b
Panoramic radiography showing two fractured "long 4-hole plates" on the left mandibular ramus. Two "regular 6-hole plates" were used on the right mandibular ramus.
177
Figure 11.2
The reasons for plate removal and the number of patients with plates removed.
179
Figure 11.3
Number of patients with plate removal according to age group.
179
XIII Figure 11.4
Percentage of miniplates removed in the lower jaw according to the type of miniplate and the side of placement
181
Figure 12.1a
Cross-sectional and lateral view of the mandible showing: a) inclusion of only the buccal plate in the split
187
Figure 12.1b
Cross-sectional and lateral view of the mandible showing: b) inclusion of both buccal and lingual plate in the split
187
Figure 12.2
Series of OPG images from a single patient before, immediately after and one year after operation (no defect in the lower border of the mandible)
189
Figure 12.3
Series of OPG images from a single patient before, immediately after and one year after operation (defect in the lower border of the mandible )
190
Figure 12.4
A panoramic radiograph measured linear distances
showing
191
Figure 12.5
Graphical representation of predicted probability of having a defect
194
Figure 12.6
Posterior rotation of the proximal fragment in large BSSOadvancements creating an enhanced risk for a bone healing defect at the lower border.
196
Figure 12.7
Modified approach to the lower border (a) keeping the lingual cortex of the lower border intact (b) . The vertical anterior cut is started from below with the drill no deeper than the bleeding points (c). The the initiation of the split is prepared with a piezo-surgical device trying to make a groove at the lower border dividing lingual and buccal lower border(d)
197
Figure 12.8
Based on the findings of this study the complete section of the lower border (a) has been changed into an approach where the lingual part of the lower border is left in situ (b). The anterior vertical cut is developed from below (c). An additional groove at the lower border to avoid a bad split is adviced. This is done with the piezzo-surgical unit (d)
198
Figure 13.1
An OPG image of the mandible with arrows showing the mandibular canal
201
Figure 13.2
A cross-sectional and lateral view of the mandible. a A neurovascular bundle remains attached to the proximal segment of the mandible (Axial View) . b A freer or a nerve hook-type instrument is used to free nerve from bone (Coronal View) . c An osteotome is used to free nerve from bone (Coronal View)
202
Figure 13.3
A cross-sectional view of the mandible. (a)A neurovascular bundle is entirely surrounded by bone (Axial View) . (b) A chisel is used to remove bone resistance (Axial View)
202
Figure 13.4
An OPG image of the mandible (postoperative)
203
of
the
mandible
XIV Figure 13.5
An OPG image of the mandible, with dotted lines representing locations where MC was assessed at three locations (Angle: most distal dotted line; M2: dotted line, immediately distal to M2; , M1: dotted line mesial to M1)
205
Figure 13.6
MC visibility at Angle
207
Figure 13.7
MC visibility at M2
207
Figure 13.8
MC visibility at M1
208
Figure 13.9
Evolution of visibility over time in the M2 region
213
Figure 14.1
Error-bar chart, dots representing % of transfusion, horizontal lines representing 95% confidence interval; overall % is an estimate based on a beta-binomial model.
234
Figure 14.2
Error-bar chart, Le Fort I single jaw osteotomy with additional surgery; dots representing % of transfusion, horizontal lines representing 95% confidence interval; overall % is an estimate based on a beta-binomial model.
238
Figure 14.3
Error-bar chart, bimaxillary surgery without additional surgery; dots representing % of transfusion, horizontal lines representing 95% confidence interval; overall % is an estimate based on a beta-binomial model.
241
Figure 14.4.
Error-bar chart, bimaxillary surgery with additional surgery; dots representing % of transfusion, horizontal lines representing 95% confidence interval; overall % is an estimate based on a beta-binomial model.
248
Figure 15.1
The reciprocal oscillating saw engages both vestibular and lingual cortex of the chin and penetrates the floor of the mouth (a), severing bloodvessels close to the lingual border (b).
255
Figure 15.2
In contrast the piezosurgical unit will not severe bloodvessels (a) close to the lingual border even when penetrating through the lingual cortex (b).
255
Figure 15.3
Patient the day before the BSSO (24.10.1990)(a) The same patient 2 days after the BSSO (27.10.1990, operation 25.10.1990)(b,c)
260
XV
LIST OF TABLES Table 2.1
Tests for evaluating nerve injury after BSSO
Table 2.2
Comparison of methodological parameters in 6 publications concerning set-back osteotomies of the lower jaw
Table 2.3
Classification classification)
Table 4.1a
Number of operations classification
performed
Table 4.1b
Number of operations classification
planned
Angle
59
Table 4.2
Analysis of the need to change the treatment plan according to different variables
60
Table 4.3
Number of patients with a changed treatment plan according to their Angle classification
60
Table 4.4
Number of osteotomies planned and number of osteotomies operated
60
Table 4.5
Average lip to incisor at rest (LI rest) and during smiling (LI smile) and average overjet (OJ) and overbite (OB) for the compliant and the changed treatment plans, subdivided for (a) Class II and (b) Class III Angle malocclusion
61
Table 4.6
The effects of a SARPE on treatment planning
62
Table 4.7
Indications for surgery of Class I patients
62-63
Table 4.8 a+b
Review of all factors that induced a change in the treatment plan
64-65
Table 4.9a
Main reason for a change in treatment plan in Class II patients
68
Table 4.9b
Main reason for a change in treatment plan in Class III patients
68
Table 4.10
All patients in whom there was a change in treatment plan, due to different parameters. (LI: Lip to Incisor)
71
Table 5.1
The number of patients with or without changes in lateral cephalometric angles before and after surgery
78
Table 5.2
Student’s paired t-test results
79
Table 5.3
Descriptive statistics of PP-SN angle by gender
80
Table 5.4
Descriptive statistic of PP-SN angle by occlusion
81
Table 5.5
Coefficient of regression and their signifance for model angle PP-SN post surgery
83
Table 5.6
Descriptive statistic of U1-SN angle by gender
83
of
Surgical
Complications
25 36-43
(Clavien-Dindo
46
according to the Angle
59
according
to
the
XVI Table 5.7
Descriptive statistic of U1-PP angle by gender
Table 5.8
Present data and previous study results
Table 6.1
Surgical details
96
Table 6.2
The median and first and third quartile (Q1, Q3) deviation of measured variables by status of nerve
97
Table 6.3
Logistic regression analysis, controlling for age, sex, type of movement, and side in each model
98
Table 6.4.
Predictive ability of Nerve to Inner BC and Nerve to Inner IC distance measurements
99
Table 7.1
Demographic data including gender and age (N : total number ; n : number of males or females ; SD : standard deviation ; IQR : interquartile range, Range: min-max
110
Table 7.2
Summary of the surgical movements realized with the BSSO technique. As it appears 105 BSSO advancements were realized, 15 BSSO setbacks, 43 BSSO rotations to correct for a mandibular asymmetry
110
Table 7.3a
Surgical technique used to detach the IAN from the proximal fragment
111
Table 7.3b
Concurrent genioplasty numbers
Table 7.4
Follow-up summary statistics
summary
statistics
83 87-88
111 111112
Table 7.5
Follow-up included
by
sensibility,
all
patients
112
Table 7.6
Self-reported labial sensibility at last follow-up
113
Table 7.7
Summary statistics of vertical distance between MC to inner lower border at sections M1, M2, right and left mandible (NR : not recorded)
113
Table 7.8
Summary statistics of horizontal distance between MC to inner border of the buccal plate at sections M1, right and left mandible (NR : not recorded)
114
Table 7.9
Summary of the results of the univariate logistic regression analysis between the occurence of hypoesthesia and the distances to inner or outer lower or buccal border at sections M1 or M2 of the right and left mandible
115
Table 7.10
Self-reported labial sensibility detachment, right mandible
correlated
with
type
of
115
Table 7.11
Self-reported labial sensibility detachment, left mandible
correlated
with
type
of
116
Table 7.12
Estimated Odds ratio and 95% confidence interval for the predictors age and genioplasty
116
Table 7.13
Univariate logistic regression
119
XVII Table 7.14
Self-reported disturbances of sensibility of the lower lip in patients with BSSO surgery without genioplasty, by side.
119
Table 7.15
Objective neurosensory testing (OBJ) versus subjective findings on IAN disturbance as reported by patients(SUBJ). Modified after Baas et al, 2012; nl = normal; dist = disturbed
120
Table 7.16
Same data as in table 7.15, expressed as true positives (TP), true negatives (TN), false positives (FP) and false negatives (FN). Modified after Baas et al, 2012; nl= normal; dist= disturbed
121
Table 8.1
Incidence of bad splits
129
Table 8.2
Review of reported incidences of bad split occurrence during SSO procedures
138
Table 9.1
Morphometric measurements for deducted from the CBCT images
2,
150
Table 9.2
Descriptive statistics on skull base measurements for 120 dry skulls; cadaver study
151
Table 9.3
Nerve disturbances that have been reported in the literature secondary to dislocated or displaced condylar and/or subcondylar fractures of the mandible
158
Table 10.1
Surgical and demographic data of patients diagnosed with neuropathic pain after orthognathic surgery
166
Table 11.1
Review of reported incidence of plate removal after BSSO and Le Fort I procedures
175
Table 11.2
Number of patients with plate removal according to the type of surgery
176
Table 11.3
Analysis of the need for plate removal for different variables
176
Table 11.4
Occurrence of all plate removals and occurrence of plate removals because of infections according to patient age
180
Table 11.5.
Occurrence of plate removal according to the number of patients and the year of the osteotomy
180
Table 12.1
Proportion defects for categorical covariates
192
Table 12.2
The median and first and third quartile (Q1, Q3) deviation of measured variables by defect status
193
Table 12.3
Simple logistic regression: Univariate analysis of each of the factors and measurements
193
Table 12.4
Multiple logistic regression
194
Table 13.1
MC visibility over time at Angle, M2, and M1 locations for both left and right sides of the mandible
206
Table 13.2
MC visibility over time for patients with nerve detachment, presence/absence of plate, and infection
209
Case
1
and
Case
XVIII Table 13.3
Univariate logistic regression analysis of each factor and measurement, modeling the cumulative probability of visibility of IAN
210
Table 13.4
Multiple logistic regression analysis of each factor and measurement, modeling the cumulative probability of visibility of IAN
210
Table 14.1
Summary of entries in Pubmed, Scopus, Limo
217
Table 14.2
Studies with individual patient data on bloodloss and duration of surgery
224
Table 14.3
Relation bloodloss versus duration of surgery
224
Table 14.4
Transfusion need in SSO
230
Table 14.5a
Transfusion rate in Le Fort I single jaw osteotomy without concomitant procedures
232
Table 14.5b
Transfusion rate in Le Fort I single jaw osteotomy without concomitant procedures: predonation policy versus no predonation policy
233
Table 14.6
Mean blood loss for Le Fort I single-jaw osteotomies without concomitant surgery, sorted according to mean blood loss reported per author
235
Table 14.7
Transfusion need for Le Fort I single jaw surgery with additional procedures
236
Table 14.8
Transfusion rate in Le Fort I single jaw osteotomy with additional surgery: predonation policy versus no predonation policy
237
Table 14.9
Transfusion need bimaxillary surgery procedures, predonation policy
without
additional
239
Table 14.10
Transfusion need bimaxillary surgery procedures, no predonation policy
without
additional
240
Table 14.11
Transfusion need for bimaxillary orthognathic surgery without additional or complex procedures (numbers): summary
241
Table 14.12
Transfusion need for bimaxillary orthognathic surgery without additional or complex procedures (percentage)
242
Table 14.13
Transfusion need for bimaxillary surgery over the years in centres without predonation policy
242
Table 14.14
Transfusion need for bimaxillary surgery over the years in centres with a predonation policy, expressed in numbers of patients transfused.
243
Table 14.15
Transfusion need for bimaxillary surgery over the years in centres with a predonation policy, expressed in % of patients transfused
243
Table 14.16
Transfusion policy according to author, in bimaxillary surgery without concomitant procedures
244
XIX Table 14.17
Transfusions according to predonation policy and grade of hypotension (numbers)
245
Table 14.18
Transfusions according to predonation policy and grade of hypotension (percentage)
246
Table 14.19
Transfusion need in bimaxillary surgery with additional or complex procedures
247
Table 14.20
Transfusion need in bimaxillary surgery with additional or complex procedures;predonation versus no predonation policy, summary
248
Table 14.21
Summary of transfusion rate according to procedure and predonation policy
249
Table 16.1
Studies including at least four weeks postoperative follow-up and analysis of complications, including postoperative hemorrhage requiring reintervention
268
XX
LIST OF ABBREVIATIONS A point
Greatest depression point in the anterior of maxilla
ANB
angle between the line nasion to A-point and the line nasion to B-point
ANB angle
angle made by A point and N point and B point
B point Bimax
greatest depression point in the anterior mandibular Bimaxillary operation
BSSO
bilateral sagittal split osteotomy
CBCT
cone-beam computed tomography
CCD
charged-coupled device
CH
controlled hypotension
CH-NFS CO
controlled hypotension; no further specification centric occlusion
CR
centric relation
CT
computed tomography
EDA
exploratory data analysis
ENT
ear, nose and throat
fo_left fo_right
deepest point of the midfossa (MF) to the lateral edge of the left foramen ovale deepest point of the MF to the lateral edge of the right foramen ovale
GEE IAN
generalized estimating equations inferior alveolar nerve; in the UK the term IDN ‘inferior dental’ nerve is preferred
ICR
idiopathic condylar resorption
IMF
intermaxillary fixation
IVRO
intraoral vertical ramus osteotomy
IWT
agentschap voor Innovatie door Wetenschap en Technologie
LOCF
last observation carried forward
LN
lingual nerve
MMF
maxillo-mandibular fixation
MAP
mean arterial pressure
MC MP
mandibular canal mandibular plane; plane from menton point to gonial angle of the mandible
MRI
magnetic resonance imaging
N Nasion
junction of the nose and the frontal bone
NR
not recorded
OMFS
oral and maxillo-facial surgery
OSAS PA
obstructive sleep apnea syndrome posteroanterior
PCR
progressive condylar resorption
Pog
pogonion
PP
palatal plane
PP plane
plane from anterior nasal spine to posterior nasal spine
PP-Mand. plane angle PP-mandibular plane angle
angle between palatal plane and mandibular plane angle between palatal plane and mandibular plane
PP-SN plane angle
angle between palatal plane and the sella-nasion plane
pt_right
deepest point of the MF to the rim of the base of the right lateral pterygoid plate
pt_left
deepest point of the MF to the rim of the base of the left lateral pterygoid plate
RME
rapid maxillary expansion
RPE S point
rapid palatal expansion middle of sella
SARPE
surgically assisted rapid palatal expansion
SD
standard deviation(s)
S.E.M.
standard error of the mean
SME
slow maxillary expansion
XXI SN plane
plane passed from S point and N point
SNA SNA angle
angle between sella-nasion line and A-point angle made by S point and N point and A point
SNB
angle between sella-nasion line and A-point
SNB angle
angle made by S point and N point and B point
SN-Mand. plane angle
angle between SN plane and mandibular plane
SN-Mand.angle
angle between SN (sella-nasion)plane and mandibular plane
SN-mandibular plane angle
angle between SN plane and mandibular plane
SORG
Strasbourg Osteosynthesis Research Group
SSO
sagittal split osteotomy
TMJ
temporomandibular joint
TPD
Transpalatal Distractor
TSEP
trigeminal somatosensory-evoked potential
U1
plane passed from coronal tip and root apex of the central incisors
U1
upper incisor
U1-palatal plane angle
angle between upper incisor and palatal plane
U1-PP plane angle
angle between U1 and palatal plane
U1-SN plane angle
angle between upper incisor and sella-nasion plane
U1-SN plane angle
angle between U1 and the SN plane
XXII
CHAPTER 1 INTRODUCTION
Chapter 1
Orthognathic surgery is a pillar of contemporary oral and maxillofacial surgery, involving the surgical movement of the tooth-bearing segments of the upper jaw and lower jaws. Additional surgical procedures including genioplasty, rhinoplasty, zygomatic osteotomy, and soft tissue procedures are often performed in the same session. In combination with orthodontics, achieving a functional occlusion is possible. The repositioning of the skeletal fragments of the face directly influences the position of the muscles attached (Dicker, 2012) , the volume and shape of the nasopharyngeal and/or oropharyngeal airway, the soft tissues overlying the skeletal framework, and the nerves, vessels, and fascias. Indirectly, the condylar surface is influenced, and the positions of the hyoid and tongue and lips, the swallowing mechanism, and even speech in some procedures are affected. Improvement of phonation has been documented (Kharrat et al, 2006). The surgical change in maxillofacial anatomy and the change in occlusion through orthodontics are powerful agents with potentially beneficial effects. The correction of skeletal proportions in the vertical, transverse, and sagittal dimensions produces faces in harmony and balance. Muscles that were in disuse (open bite, Class II) regain posture and tonus and can produce lipseal, alleviate lip incompetence and loss of saliva, and heal perlèche. Increasing the airway volume together with its shape influences breathing patterns, constituting a powerful treatment for obstructive sleep apnea syndrome and mouth breathing. Correcting mouth breathing prevents dehydration of the oral cavity with improvement of the health of dental and periodontal tissues. Correcting the apnea–hypopnea index in obstructive sleep apnea patients influences cardiovascular parameters and quality of sleep and results in improved psychological well-being. Occlusion correction results in improvement of chewing ability and constitutes a stabilising factor in temporomandibular joint (TMJ) function with an often beneficial effect in TMJ dysfunction and associated signs and symptoms. Additionally, this correction improves periodontal health and longevity of dental tissues after correction of traumatic occlusion and deep bite pathology. The chewing ability is further improved by allowing prosthetic rehabilitation after surgical correction of dysgnathic relations between the upper and lower jaws. Speech is often improved after the volumetric change of the oral cavity, after closure of dental and skeletal spaces, and after achieving the ability to seal the anterior part of the oral cavity. The change in the soft tissue envelope of the face overlying the skeletal framework is the first striking change after orthognathic surgery. Its appearance influences how the patient and others perceive the face. Through displacement and compression or surgical enhancement, the soft tissue effects of orthognathic surgery may be considerable with a profound influence on the social and psychological function of the facial appearance. In children, it can influence the psychosocial development of the dysgnathic child. Displeasing or maturational and age-related changes of the integumental soft tissue drape can be significantly improved. The application of orthognathic surgery can further be extended to aesthetic facial skeletal contouring, changing the ethnic appearance of patients, and achieving transgender feminisation of the facial skeleton. The surgical techniques of orthognathic surgery are also heavily applied in the correction of congenital and posttraumatic malformations and serve well in the transmaxillary approach of skull-base tumours and the transmandibular approach of the infratemporal fossa. Surgical techniques having such far-reaching consequences that are multidisciplinary in nature (orthodontist, general dentist, prosthodontist, speech pathologist, ENT surgeons, plastic surgeons) are prone to having simultaneous potential benefits and risks. Because orthognathic surgery targets locating the optimal balance of skeletal structure, function, and aesthetics, it is far more than a surgical technique and rather constitutes a orthognathic chain involving good clinical diagnosis and judgement, optimal intra- and interdisciplinary decision-making, proper communication, precise planning, orthodontic and surgical execution, and meticulous follow-up. Any undesired effect in one of the steps in the orthognathic surgical chain could be seen as a complication. In orthognathic surgery, the term ‘complication’ even applies when the surgical treatment goals have not been achieved and the results obtained are not acceptable from a functional and/or aesthetic point of view (Reyneke, 2011). This chain encompasses diagnosis/treatment planning, the surgical phase, the short-term postoperative period, and long-term stability. Most side-effects of orthognathic surgery resolve spontaneously. Surgeons rely heavily on the patient’s healing capacities in resolving postoperative edema and hematoma formation, trismus, joint tenderness, wound closure, bone-healing, correction of arterial and venous blood supply, lymphatic drainage, and 2
Chapter 1
infection control. Side-effects of orthognathic surgery include scar formation, thinning of the soft tissues, fat necrosis, less than optimal bone remodelling, less than optimal joint remodelling, limited opening of the mouth, increased recurrence to the original condition, and insufficient adaptation of muscles and airway. Side-effects become complications when these are undesired in the perception of the patient or the surgeon. As such, we define complications in orthognathic surgery as effects in one of the steps in the orthognathic surgical chain that are perceived as undesirable by the patient and/or surgeon. It may well be that the perceived adverse event was caused by pre-existing factors that were outside the surgeon’s control. Patients are not the same in health, habits, immunity, or healing power and have varying susceptibility to complications. A medical legal fault implies proven defective judgement, deficient knowledge, or carelessness and cannot be synonymous with a complication. The term ‘error’ is rarely used other than in the statistical sense in publications on orthognathic surgery. To know when a statistical error becomes an outlier implies knowledge of the population examined. That in itself is a difficulty because there is no such parameter as a population mean in a matter as individual as someone’s face. Consider the maxilla, the mandible, the chin having three possible positions (normal, hypo-, hyper-) for their vertical, transverse, sagittal, and rotational dimensions. Together, they constitute 312=531,441 combinations, not taking into account all other variables that constitute the oro-facial mosaic. To describe the possible errors for each individual is not a realistic goal. The phase of communication with the patient and informed consent are ideally suited to bridge the gap between the patient’s expectations and the surgeon’s intellectual and technical effort. Patients usually accept well the fact that surgery is only capable of moving bony parts of the face while the patient often sees soft tissues extra-orally and experiences intra-oral changes. Distraction osteogenesis (vertical, sagittal) and surgical procedures to correct the skeleton in congenital anomalies are a further extension of orthognathic surgery and bridge the gap towards reconstructive surgery. Despite the variability among individuals, only a few surgical approaches have persisted over the history of orthognathic surgery: Le Fort I osteotomy (Figure 1.1) , surgically assisted rapid palatal expansion (SARPE), BSSO, intra-oral vertical ramus osteotomy (IVRO), and osseous genioplasty. Differences exist according to a number of schools of thought, and wide individual variations or approaches are common.
Figure 1.1. Schematic drawing of a bimaxillary osteotomy consisting of a Le Fort I osteotomy in the upper jaw and a sagittal split osteotomy in the lower jaw.
In the Le Fort I osteotomy, differences concern the type and location of the pterygomaxillary disjunction. Most often, the separation is located at the pterygomaxillary junction. Others prefer the posterior split before the ptergyomaxillary junction, at the location of the upper third molar. Most still use a mallet and chisel while others use micro-oscillating or piezoelectric saws to achieve the disjunction. Still others
3
Chapter 1
prefer not to osteotomise the pterygomaxillary disjunction and directly proceed to the downfracture of the maxilla. With SARPE, much more variation exists. Most practitioners perform the horizontal Le Fort I osteotomy cut. Then, any or all of following bone cuts can be made: separation of the septum, lateral sinus wall, lateral wall of the nose, or midpalatal separation between both upper central incisors. Most use access to the Le Fort I osteotomy to achieve any of these cuts. Others prefer a transpalatal access to realise the midpalatal split or favour a paramedian split instead. The widening of the midpalatal suture is either realised with a bone-borne transpalatal device or with a tooth-borne orthodontic transpalatal device.
Figure 1.2. In surgically assisted rapid palatal expansion of the upper jaw (SARPE) we use the same bone cuts as in a routine Le Fort I osteotomy with in addition a midline split of the maxilla. The same technique of pterygomaxillary disjunction is used. No downfracture of the maxilla is performed.
More important differences exist in the BSSO of the lower jaw. Irrespective of the instruments used, in one school of thought, one goal is to achieve the horizontal split in the ascending ramus as a complete split of the entire width of the ascending ramus, while the other school targets ending the split in the ascending ramus directly behind the lingula (short split). The school of thought in favour of this method will argue that there are fewer problems in set-backs with a short split. Arguments in favour of short splits are that there is no need to free the pterygomasseteric sling, which remains attached at the condyle-bearing fragment. No stripping of the pterygomasseteric sling prevents aseptic necrosis of the mandibular angle. Another advantage is argued to be that in rotations and large advancement, there is less interference of the distal part of the tooth-bearing fragment with the proximal fragment. This factor is of influence in the rotation of the condyle and the amount of gap at the site of the vertical mandibular body split. Yet a further advantage in set-backs is that a short split avoids any interference with the facial nerve when retropositioning the proximal fragment.
4
Chapter 1
Figure 1.3. Schematic drawing of a bilateral sagittal split osteotomy with advancement of the lower jaw. The left side of the mandible has been stabilized with two miniplates. At the lingual site of the right lower jaw the horizontal cut at the medial side of the ascendic ramus is depicted with the horizontal cut ending directly behind the lingula (Nomina Anatomica: Lingula Mandibulae).
Those who favour the split along the complete width of the ascending ramus will find more bony contacts between the proximal and distal fragments, promoting bone healing in large advancements and facilitating the placement of transbuccal bicortical screws. In the body of the mandible, the vertical cut can be located at any location between the second premolar and the angle of the mandible. Usually, those who favour fixation of the lower jaw with osteosynthesis plates and monocortical screws will prefer a more anterior location of the vertical cut at the mandibular body, whereas those who prefer internal rigid fixation with bicortical screws without plates will prefer a more posterior location of the split. In some cases of set-back, the mandibular cut at the buccal side of the mandible is not placed vertically at the body of the mandible but high up in the ascending ramus, not far from the internal cut. This technique, however, is only possible with the use of the endoscope, requires special instrumentation, and is not widely used. All of these techniques are designated as ‘sagittal split osteotomy’ (SSO) but feature a number of important variations. Numerous variations further exist in the techniques used to achieve the split once the cuts are made. These include the use of burs, saws, piezosurgical devices, blunt or sharp chisels, heavy or thin chisels, spreaders, separators, or other instruments to complete the split. Equally numerous variations exist in handling of the IAN during the completion of the sagittal split of the lower jaw. The genioplasty requires a horizontal bony cut through the outer and inner cortices of the chin (menton) and can vary according to the location and the extent of the horizontal cut and has less defined osteotomy margins. These bony cuts can be realised either with a drill, an oscillating saw, or the piezosurgical osteotome. Some will perform a genioplasty concomitantly with SSO, but others will defer the genioplasty to a later surgical time because of a fear of inflicting too much damage to the IAN when it is performed simultaneously with SSO. The vertical ramus osteotomy of the mandible is performed with particular instruments to that end through an intraoral route. Few perform this technique through an open extra-oral access. Contemporary orthognathic surgery avoids any extra-oral access to realise osteotomies. However, transoral fixation techniques through stab incisions are used to introduce endoscopes or to facilitate screw fixation at places that are inaccessible through an intra-oral route. Historically, the upper jaw has been fixed with osteosynthesis wires; however, osteosynthesis plates and screws currently are used for fixation of the upper jaw. In the lower jaw, wire fixation of the bony parts has been abandoned in favour of fixation with osteosynthesis plates or bicortical screws without plates (Stoelinga and Borstlap, 2003). When using osteosynthesis plates, one can use either one plate or two to bridge the osteotomy gap at the body of the mandible. Proponents of miniplates and monocortical screws 5
Chapter 1
to stabilise BSSO-advancement surgery of the lower jaw list a number of advantages over lag screws or positional screws: avoidance of external incisions; avoidance of excessive rotation of the proximal fragment by bending the miniplates; avoidance of inferior alveolar nerve or lingual nerve damage from monocortical screws; ease of correction a perioperative condylar sag; easy removal of miniplates in case of necessity; and ease of readjustment of the plates in training centres (Stoelinga and Borstlap, 2003). Bicortical screws can be used either as lag screws or positioning screws without compression of the bony parts. Ochs (2003) listed a number of factors that influence the choice of fixation after a mandibular osteotomy: bony anatomy, osteotomy design, surgical movement/vector, third molars, unfavourable split or craze lines, IAN position, palpability, bulk of overlying soft tissues, proximal segment positioning, cost, and surgeon preference. Risk for lingual nerve (LN) damage, surgical routine (Reyneke, 2010), and minimal instrumentation can be added to that list. Rigid internal fixation with miniplates has been used in orthognathic surgery since 1981 (Drommer and Luhr, 1981). Rigid fixation has become the standard of care for a number of reasons, including: increased fragment stability, better airway management, increased postoperative dietary options, shorter hospital stay, patient convenience, earlier jaw mobilisation, decrease in postsurgical maxillomandibular fixation time, earlier function, and earlier return to work. Over the years, several concerns have arisen about rigid fixation, including: the incidence of increased neurosensory damage; the debatability of increased longterm stability for a number of skeletal movements; and the more frequent mediolateral torquing or posterior positioning of the condyle with rigid fixation techniques, possibly resulting in TMJ dysfunction or even condylar resorption. The presence of foreign material in the lower and upper jaws is an issue in its own, comparable to the problem of foreign material in fracture healing of the jaws. Infection is the most common cause of removal in symptomatic patients. Again, here one finds two schools of thought. The SORG group (SORG, 1991) recommends routine removal of osteosynthesis plates, at least if the removal procedure does not cause undue risk to the patient, under the presumption that once healing has occurred, the plate becomes a non-functional implant with unknown effects on the patient over the long term. The advantage of stability that has been gained with rigid osteosynthesis hardware clearly has had a cost. The gain in one complication type has resulted in an increase in other complications. No rules or guidelines exist concerning gap filling of the osteotomy at the osteotomy site in the upper jaw and lower jaw and at the chin. The old process of filling the osteotomy gap with autologous bone has long been abandoned in the era of rigid internal fixation with osteosynthesis plates and screws. No cutoff point has been calculated beyond which a bone graft is necessary. Some practitioners use autologous bone from the iliac crest or the cranial vault, some use synthetic bone, and some prefer the use of plasma-rich protein. Others prefer interpositional grafts with freeze-dried or alloplastic bone or cartilage while still others will use a mixture of any of these materials. Bone substitutes are undergoing a change from a simple replacement material to an individually created composite biomaterial with osteoinductive properties to enable enhanced defect bridging (Kolk et al, 2012). In terms of risk factors, obviously opposing views exist, and further prospective studies are necessary. As far as intermaxillary wire fixation is concerned, some practitioners use intermaxillary fixation on brackets, others will use arch bars, and others will use any form of skeletal intermaxillary fixation. In most settings, elastics are employed to guide the occlusion in the postoperative period. The use of a final splint or wafer is favoured by some schools whereas others try to achieve a functional interdigitation perioperatively. The administration of antibiotics varies from none at all to various regimes, including presurgical only to a prolonged postoperative regime. The use of an intraoral drain is centre dependent. Some routinely place an intraoral drain after a BSSO procedure (Kuhlefelt et al, 2012); however, we adhere to the Stoelinga school of thought, which does not place an intraoral drain as a routine. Blood transfusion policy has been a matter of debate for a long time. Nowadays, most centres avoid preoperative autologous blood donation, and even routine preoperative cross-matching of blood is considered superfluous (Kurian and Ward, 2004). 6
Chapter 1
Controversy exists about the timing of third molar removal. The school of thought arguing in favour of timely removal of third molars advocates a removal ranging from 6–9 months (Bays, 1997) before performing mandibular surgery and argues based on the following advantages: less risk of a bad split (buccal plate, lingual plate) (Van Sickels, 2011); less risk for IAN injury; reduced surgical time; and increased technical osteotomy difficulty when present (Reyneke, 2002). An opposing view is held by Doucet et al (2011), who presented data suggesting that the presence of third molars during SSO is associated with a statistically significant decreased incidence of neurosensory disturbance of the IAN at 3 and 6 months postoperatively. In their study, the surgeon’s experience had no effect on the sensory recovery of the IAN after SSO. They also found that the presence of a mandibular third molar during surgery did not increase the incidence of unfavourable fractures or operating time to any clinically significant degree (Doucet et al, 2011). Treatment of TMJ disorders is another area of controversy. Some clinicians want TMJ disorders to be treated before orthognathic surgery, and some wait until months after the orthognathic procedure because many TMJ complaints disappear after surgery. Still others advocate concomitant joint surgery and orthognathic surgery (Wolford, 2003; 2007). Technical innovations and changes have been manifold at all steps of the SSO and the IVRO and less so in the Le Fort I osteotomy. Endoscopically assisted approaches have been introduced (Kim and McCain, 2008). For a long time, the use of presurgical orthodontics was standard. Currently, however, different schools of thought favour surgery-first protocols and orthodontics afterward. Usually, these regimes involve multisegmental osteotomies of the upper jaw. In these cases, the surgery-first protocol is used as an alternative to presurgical orthodontics with or without a SARPE procedure of the upper jaw. Until recently, the surgical protocol in bimaxillary surgery involved the Le Fort I osteotomy, to be finished first, followed by osteotomy in the lower jaw. In more recently emerging schools of thought, the reverse protocol is favoured, with completion of the osteotomy of the lower jaw first, followed by the upper jaw osteotomy. The rationale behind this reversed order is that a posterior extrusion of the maxilla is easier when the mandible is done first and that the position of the lower jaw becomes independent of the TMJ if it is finished first with the upper jaw still in its original fixed position. This school of thought also reflects a changing view concerning the stability of the surgical result. From the traditional perspective, it is not possible to lengthen the posterior height of the face in a stable way over a prolonged period of time (Lake et al, 1981; Nanda et al, 1990). This traditional view has been challenged by those who extrude the maxillomandibular complex posteriorly to achieve a counterclockwise rotation with an advanced projection of the lower jaw and chin (Rosen, 1993; Wolford et al, 1993; Wolford et al, 1994; Chemello et al, 1994) . Treatment planning still varies widely among surgical teams. Some surgical teams treat most of their surgical cases with bimaxillary surgery. Kretschmer et al (2008) stated that they treat less than 20% of their caseload (approximately 125 bimaxillary surgeries per year) with single-jaw surgery. The Arnett school of thought typically advocates treating patients with bimaxillary surgery and multisegmental Le Fort I osteotomies. Concomitant surgical procedures can significantly increase blood loss and operation time. The range varies for genioplasty, septoplasty, inferior turbinate reduction, removal of third molars, TMJ arthroscopy, rhinoplasty, liposuction, liposculpture, and facial sculpting. Orthognathic surgery in cleft patients and craniofacial malformations differs as to the extent and frequency of complications because of the compromised healing capacities of the tissues (scars, vascularity), anatomical constraints, and large surgical changes and displacements that are necessary in these patients. Whether the complications concern relapse, vascular complications, or compromised healing, they all occur more frequently in these groups.
7
Chapter 1
During the last two decades, orthognathic surgery has witnessed a shift from monomaxillary to bimaxillary surgery, mainly to improve facial harmony in addition to reaching a stable and functional occlusion. This shift has been realized largely by addition of monosegmental or multisegmental Le Fort I osteotomies. Because no surgery is risk free, this change in attitude comes at a price for the patients involved. Complications indeed weigh more in elective surgery than in non-elective surgery. The patient should be well informed about possible complications before the start of orthodontic treatment if surgery is planned. For an important complication such as bleeding after Le Fort I osteotomies or SARPE, the incidence is insufficiently established. The need for blood transfusion after orthognathic surgery is poorly documented. Genioplasty is considered safe in the plastic surgery literature and has been promoted as an office-based procedure, but this support is based on scarce data. Risk factors for the occurrence of hypoesthesia and/or neuropathic pain after BSSO surgery are still insufficiently established. A predicted surgical plan at the start of the orthodontic treatment may change after presurgical alignment, but the risk factors for a change in treatment plan are ill-defined. The body of this thesis focusses on addressing the aforementioned issues. The chosen approach and the purpose of this thesis is to study complications in sufficiently large samples to allow for identification of risk factors that may adversely affect outcome in orthognathic surgery. Large sample sizes also allow study of unusual complications. Because many complications are technique sensitive and depend on patient characteristics, most research findings in orthognathic surgery fall short of satisfying a statistician. Multicentre approaches are rare (Borstlap et al, 2004a, b, c), and the available study population is rarely homogeneous enough to fulfil the sample size requirements in cohort and case-control outcome studies (Cryer, 1999). The total number of orthognathic procedures officially filed for reimbursement in Belgium in the year 2002 involved 810 patients (Politis, 2007). This thesis has some unique characteristics for the study of complications after orthognathic surgery. The techniques used in all patients have been consistent throughout the years. Both the Le Fort I osteotomy and the BSSO have been executed as they were taught by Professor P.J.W. Stoelinga (Stoelinga and Borstlap, 2003). One difference in the Le Fort I osteotomy is the use of the chisel at the pterygomaxillary junction. The main difference in the BSSO is the use of two miniplates at each osteotomy site. From 1989 to 31 July 2012, 2213 patients have been operated with orthognathic surgery at our centre. BSSO was performed in 1316 patients, Le Fort I osteotomies in 808 patients, genioplasty in 365 patients, and SARPE in 419 patients. The author participated during surgeries of more than 2100 patients, either as first surgeon or as supervising surgeon. One surgeon devised the surgical plan in these patients. One author wrote all of the operative charts according to a standard protocol. The postoperative follow-up was executed according to a fixed time frame and a fixed protocol. Postoperative radiographic examinations were completed within 1 week postoperatively and at 6 weeks, 6 months, and 1 year postoperatively and in the intervals as needed in case of complications. Most chapters are based on large patient samples. Both prospective and retrospective studies have been performed. The large sample sizes make evaluation of unusual occurrences possible. Based on the large sample size and the key features of a single institution, single surgeon, single technique, standardized operative charts written by a single surgeon, few missing data, and high patient compliance with follow-up, the study design is valid for both the prospective and retrospective parts of this thesis.
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CHAPTER 2 A CRITICAL APPRAISAL OF THE LITERATURE ON COMPLICATIONS OF ORTHOGNATHIC SURGERY
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Outcome study comparison becomes extremely difficult in orthognathic surgery because of huge variability in diagnoses, surgical techniques used, and confounding factors. This difficulty is exacerbated by the fact that data collection varies widely among studies, whether it concerns frequent complications (relapse, neurosensory deficits, infection, condylar resorption) or infrequent complications (hemorrhage). Identification of the objective and subjective parameters of the collected data and identification of the time frame before or after the orthognathic surgical procedure are of paramount importance. Sample size is also an issue in an orthognathic population. Long-term follow-up of these young patients is made difficult by the fact that they move and change address due to studies or marriage. The problem of missing data may influence statistical methods. Furthermore, valid, reliable indicators of outcome and also widely accepted valid and reliable measuring instruments need to be further developed in orthognathic surgery (Cryer, 1999). In addition to these generalised problems, specific problems concerning the study population arise depending on the complication topic. The outline followed is the patient’s treatment trajectory with complications arising from the first contact until the follow-up recall after the end of treatment.
2.1. ERRORS IN DIAGNOSIS OR TREATMENT PLANNING Errors in diagnosis and treatment planning are not limited to orthognathic surgery alone. The main difficulty of planning relates to the difficulty of precisely predicting the soft tissue outcome that accompanies the planned bony movements, both clinically or based on cephalometric analysis (Pospisil, 1987). Cephalometric tracing orientation can significantly affect surgical facial results when based only on cranial cephalometric analysis (Wylie et al, 1987). Planning either with cephalometric software or manually, based on two-dimensional lateral cephalograms, carries the burden of a large standard error, even on points that are believed to be predicted safely (Segner and Höltje, 1991). To achieve facial balance with soft tissues that satisfies the patient cephalometric analysis, model analysis must be complemented with clinical information and clinical decision-making. Cephalometric prediction of soft tissues falls short of the three dimensionality of the facial framework, especially in surgery of the upper jaw and in bimaxillary surgery. Superimposition of CBCT data can reliably be done merging the skull base using the maximum mutual information algorithm (Lee et al, 2012). For evaluation of surgical treatment results, image fusion is an accurate and reliable method that is not affected by spatial or surgical changes (Lee et al, 2012). Bianchi et al (2010) used prediction software based on preoperative CBCT data to predict the soft tissue outcome of bimaxillary orthognathic surgery (4/10 with genioplasty), comparing the prediction results with the CBCT data obtained at 6 months postoperatively. The methodology produced a percentage of simulations within the range of 71.5% to 98.0% for which the outcome error was 2 mm or less than the prediction. In 2011, the same group (Marchetti, 2011) reported that the reliability of the soft tissues preview was >91% when comparing simulation results with 1-year postoperative CT data of the same patient group. The range is not the mean but is important, too (75.5–98.8). This hitherto unseen accuracy needs to be reproducible before there can be claims of having solved the issue of soft tissue prediction in orthognathic surgery. To date, the area of the nose is not recalculated in prediction software because that area is not included in the predicted model. The difference between simulation and outcome is displayed via colour-coded distance magnitude and vector maps, using colours to highlight areas with large errors. This method, however, in addition to surface registration errors, is prone to bias because different algorithms lead to different results of surface distance (Kim et al, 2010). The biggest drawback of these tools is the lack of validation of the surgical outcome quantification (Paniagua et al, 2011). If these three-dimensional methods are used to offer options to patients who might not otherwise have been recommended for treatment and induce an increase in concomitant surgical steps, this rationale should be viewed with caution. The ranges of occlusion, function, and facial aesthetics are widely different. The occlusal result is easily judged and has a narrow envelope between acceptable and unacceptable. The facial potential is, in contrast, very wide because the patient is not aware of the possible improvement versus the acquired improvement. It may well be that the patient will 10
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be happy and satisfied with a less extended surgical treatment plan that carries a lesser risk of surgical complications. Little or no research has covered that topic. Whatever improvement is offered, it should be measured against the patient’s expectations when aiming for patient satisfaction. Phillips et al (2001), in a study evaluating the effects of a computerised treatment simulation on patient expectations for orthognathic surgery, found that more than three fourths of their patient group (220 patients) expected at least a moderate improvement in oral function and profile appearance at the end of treatment and more than 40% at least a moderate improvement in general appearance, self-confidence, feelings about themselves, and confidence when out in public. Rustemeyer et al (2010) surveyed 77 Caucasian Class III patients who had been treated with orthodontics and bimaxillary orthognathic surgery at 1 year postoperatively. The patient expectations for surgery were at 71.4% for an improvement in both chewing function and in facial appearance. A total of 77.9% of patients were very satisfied with the outcome both for chewing function and facial appearance. If patients had a perception of aesthetic facial improvement, their satisfaction was high regardless of functional problems such as hypoesthesia and TMJ complaints (numbness, prickle sensations, pain in the TMJ area, or restrictions in mouth opening). The treated Class III patients of this survey with a postoperative lower SNB (75.3°±2.7°; p=0.033) were significantly less satisfied than patients with a higher SNB (≥80). Cephalometric changes of the upper jaw seemed of less overall influence. Satisfaction of family and friends correlated significantly with patient satisfaction. The influence of a patient support network was also a finding in Chen et al (2002). In a retrospective study in Class II patients treated with a sagittal split advancement osteotomy, the change in appearance after treatment as noticed by peers was a significant factor in treatment satisfaction (Trovik et al, 2008). A similar influence on patient satisfaction of improved facial aesthetics and acceptance of sensory disturbance in the trigeminal area was reported earlier by Maurer et al (2002). There is an effect of age in this relationship: older patients (>35 y) seem to suffer more from neurosensory disturbances than do younger patients with similar sensory impairments after orthognathic surgery (Westermark et al, 1999). There seems to be a weighted ranking of gains, risk factors, and complications in orthognathic surgery patients where a balance exists with gains at one plane and losses at the other. The weight may vary individually, implying a tailored approach both in informed consent, patient communication, and treatment planning. Errors of planning consist of diagnostic omissions (complete patient history, radiographic and clinical evaluation of the TMJs, model analysis, facial examination, cephalometric analysis) and of setting inappropriate goals.
2.2. PRESURGICAL ORTHODONTIC ERRORS Presurgical errors may lead to unsatisfactory results because of errors during the presurgical orthodontic preparation or during the presurgical setup and model surgery. The acceptance of a compromised presurgical orthodontic preparation or the failure to recognise it leads to compromised surgical results, built-in relapse, and additional surgical steps that could have been avoided. The list of orthodontic problems that can negatively influence the surgical outcome relates to consideration of maxillary or mandibular extractions, dental compensations, dento-alveolar transversal expansion of the upper jaw, insufficient decompensation of incisors, inappropriate positioning and axial inclination of incisors on the maxillary or mandibular base, levelling of the curve of Spee, tooth size discrepancies, the impossibility of obtaining adequate perioperative interdigitation, arch width and arch form incompatibilities, root parallelism when interdental osteotomies are planned, built-in instability of presurgical tooth movements, active archwires at the time of surgery, active transpalatal arches at the time of surgery, inappropriate dental midlines, mainly in the lower jaw when the chin midline coincides with the facial midline, inappropriate plane of occlusion, skewing, and periodontal damage through violation of the boundary conditions of bone. A special consideration is necessary in Class III patients during compensatory orthodontic treatment that fails. Delay of surgical treatment and observation of growth are wise, but if the decision is to go ahead with surgery, dental compensations need to be eliminated to avoid insufficient facial balance. 11
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Failure to cut an archwire when dental compensations are suspected is to accept postsurgical occlusal complications.
2.3. PROBLEMS WITH MODEL SURGERY AND SPLINT FABRICATION Problems with model surgery and splint fabrication are manifold (Nattestad et al, 1991; Nattestad and Vedtofte, 1992; Nattestad and Vedtofte, 1994) and directly affect the surgical result. An erroneous diagnostic waxbite will lead to an erroneous position of the upper jaw during bimaxillary surgery. In addition, postoperative malocclusions that are out of orthodontic range often are initiated perioperatively by insufficient surgical control over interdigitation, overjet, and overbite. We reviewed our experiences with ‘erroneous’ waxbites in 40 patients, all scheduled for bimaxillary surgery. The plaster casts were mounted in a Dentatus ARH articulator through facebow transfer. The waxbite was taken with the patient in the supine position, with the thumb of the clinician gently guiding the patient into a centric relation (CR) position. The waxbite is usually taken with a thickness of 3–4 mm to allow for extrusion of the maxilla during model surgery without the need to open the incisal pin of the articulator. This method facilitates avoiding errors attributed to condylar rotation, which is different in the patient as in the articulator. In the ARH Dentatus articulator, the condylar slope is set at 42° with a Bennet angle of 15°. The fit of the waxbite was checked both by the first assistant and separately by the surgeon at three time points before surgery. Once the patient was intubated at the time of the surgical procedure, the waxbite was inserted. Interference from the tongue was carefully removed. In 3 out of 40 patients, the waxbite did not fit properly. In the three patients, a more retruded and symmetric CR position was found. We were surprised that the three patients all happened to be Class III patients in whom a Le Fort I ‘advancement/extrusion’ was planned of ‘5/0’, ‘7/6’, and ‘6/1’ mm, respectively, together with a BSSO setback. These three patients had a severe Class III malocclusion. Bamber et al (1999) studied the effect of posture and anaesthesia on the occlusal relationship in orthognathic surgery and found no difference in Class III patients between the upright or supine conscious and the supine unconscious CR position. The effects of an ill-fitting waxbite at the time of surgery are two-fold. In the first place, a more retruded mandibular position will place the maxilla in a more retruded sagittal position because of transfer or the intermediate wafer. In Class III patients, a larger setback of the mandible also needs to be realised in the second part of the osteotomy when the upper jaw is done first. There is, however, a second, less obvious consequence of an ill-fitting waxbite at the time of surgery, when the mandible is positioned towards the maxilla in a Class I relationship by virtue of the final wafer and rigid fixation. The change from centric relation in the supine anaesthetized position to the postoperative conscious centric occlusion position might cause cumulative discrepancies from postural changes. In addition to postural changes, edema of the condylar tissues could provoke early relapse after bimaxillary class III surgery. It is wise, therefore, to build two safety measures into the treatment of patients with large Class III surgeries. The first is a final wafer in a slight class II position to allow for intraoperative overcorrection. This method, however, diminishes stability because maximum intercuspation at the time of surgery is believed to be the best protection against relapse (Arnett, 2004). A second safety measure is to build in room for postoperative orthodontic compensation. The best way to achieve this envelope of compensation is to ensure sufficient preoperative decompensation and a few diastemata in the lower jaw that can be closed postoperatively. Once navigational aids become a mainstay in orthognathic surgery, three-dimensional positioning errors during surgery could be solved (Bell, 2011; Füglein and Riediger, 2011; Sadiq et al, 2012). Postoperative postural changes, however, will remain a problem and need to be addressed with postoperative elastics and postoperative orthodontic treatment (Stoelinga and Borstlap, 2003).
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2.4. INTRAOPERATIVE COMPLICATIONS
2.4.1. Sagittal Split Osteotomy Intraoperative complications of the SSO can be summarised as bony, joint, nerve, vascular, and dental complications. Bony complications An unfavourable split can include a bad split, being either a buccal plate fracture or a lingual plate fracture. Risk factors for bad splits are believed to include the presence of third molars and age, but this is disputed (Chrcanovic and Freire-Maia, 2012); other risk factors such as an incomplete or inadequate osteotomy design are not disputed. A horizontal fracture of the ascending ramus or the condylar process is possible. Incomplete sectioning can be a problem when not diagnosed or with an erroneous bone cut. A drill can fracture and get lost in the soft tissues or remain as a foreign body in the cancellous bone. If the lower border remains at the buccal fragment after the split in a large advancement, a bony defect remains at the lower border of the gap. Joint complications Dislocation of the disc during manipulation or vigorous condylar seating is possible as are condylar distraction, joint compression, condylar malposition in the sagittal, vertical, or transverse direction, and malpositioning of the proximal segment. Excessive torque on condyles due to lag screw fixation with bicortical screws or plates not being passively bent are also possibilities, along with condylar torque and midline shift caused by use of fragment clamping. Muscular complications Counterclockwise rotation of the distal segment is possible. Lesions of trigeminal and facial nerve branches The IAN can be damaged at all surgical levels, at all surgical stages of cutting, splitting, manipulating, and fixation of proximal and distal segments, ranging from compression, stretching, crushing, tearing, avulsing, incomplete or complete sectioning with chisels, drills, saws, piezosurgical tips, or surgical retractors. The nerve injury can vary from neuropraxia to axonotmesis or neurotmesis. The LN is at stake during an osteotomy of the tooth-bearing fragment and during the positioning of bicortical rigid fixation at the ramus while the buccal nerve can be injured at the very beginning of the incision in the buccal vestibule. The facial nerve can be injured during large mandibular set-backs, and lesions of the marginal branch of the facial nerve due to traction with surgical retractors at the lower border are relatively frequent. Lesions of the soft tissues Herniation of the buccal fat pad is possible. Lesions to teeth Roots of molars can be damaged during the cut at the body of the mandible, especially in narrow mandibles with little distance between the roots and the buccal cortex. Hemorrhage Rarely, the inferior alveolar artery or the retromandibular veins can be troublesome. On rare occasions, even the maxillary artery can be severed during manipulations at a level higher than the lingula, causing troublesome bleeding. Hemorrhage from the facial artery during SSO has been reported (van Merkesteyn et al, 1987).
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Soft tissue tears Gingival detachment can occur, especially during simultaneous removal of wisdom teeth. Hardware problems Lesions to teeth can arise during placement of miniplates and screws. Improper and non-passive placement of miniplates or placement of screws too close to the gap margin can induce tiny fractures at the margin of the proximal segment. Periodontal lesions during placement of maxillomandibular fixation are also possible. Errors related to the final wafer cause improper occlusion. Brackets or orthodontic bands can fail and get lost in the soft tissues or in the airway (Godoy et al, 2011).
2.4.2. Genioplasty Complications of genioplasty include: hemorrhage from the vessels in the floor of the mouth and the facial artery; inadvertent cuts or drill lesions at the roots of the anterior teeth; lesions of the mental nerve and its incisor branch; and sagging chin due to inappropriate reapproximation of the muscles.
2.4.3. Le Fort I osteotomy Intraoperative complications of the Le Fort I osteotomy can be summarised as bony, positioning, nerve, vascular, dental, hardware, and soft tissue complications (Kramer et al, 2004). Bony problems The osteotomy cuts can be too low or too high. The pterygomaxillary separation can cause different problems: fracture of the pterygoid plates, very high fracture extending to the skull base, fracture at the level of the sutura transversa of the palate instead of the Le Fort I level, and incomplete fracture at the pyramidal process. In impactions, there can be bony interferences with an artery. Insufficient pyramidal bone release causing bony interferences, when undetected, can result in an inaccurate bite. Hemorrhage Perioperative hemorrhage can arise from the following vessels: the maxillary artery and its terminal branches; the descending palatal arteries; the pterygoid venous plexus; and, rarely, branches of the internal carotid artery. Nasolacrimal duct Epiphora is usually transient but has been described as leading to dacryocystitis with the necessity of a dacryorhinostomy. Retrograde hemorrhage (hemolacria) from the lacrimal puncta is usually self-limiting but can be associated with nasal packs in the treatment of epistaxis and is due to an incompetence of Hasner’s valve with retrograde hemorrhage through the nasolacrimal system or to a tear in the nasolacrimal duct (Humber et al, 2011). Nerves Injury to the infraorbital nerve is possible. Unfavourable fractures extending to the skull base may involve other cranial nerves. Septal problems One possible complication is a crooked nasal septum due to insufficient trimming and reduction of the nasal septum.
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Nasal widening This issue can arise because of insufficient bone trimming or an inappropriately large advancement; no nasal cinch; or no subnasal osteotomy-type Le Fort I. Nasolacrimal duct damage This damage is usually the result of injury with a drill or screw or a large maxillary impaction. Nasal airway obstruction. In large impactions, the nasal turbinates need to be trimmed or removed to avoid their becoming obstructive. Damage to teeth. This damage occurs mainly in segmental osteotomies or in surgically assisted rapid palatal expansion. Damage during placement of miniplates or a low Le Fort I osteotomy cut is also possible. Damage to the naso-endotracheal tube. Damage to the naso-endotracheal tube can occur during chiselling of the nasal septum, during repair of the nasal floor, or during the nasal cinch. Oronasal communication. Tearing the palatal mucosa during maxillary segmental osteotomies or during surgically assisted rapid palatal expansion can result in this problem. Hardware problems. These problems include inability to place rigid fixation in multisegmented maxillae or very atrophic maxillae; very wide gaps, making stabilisation an issue without interpositional bone grafts; insufficient graft material from the iliac crest or cranial vault; loosening of brackets with difficulties in placing maxillomandibular fixation; loss of brackets or fractured drill in tissues of the maxilla; inadequate fixation (size, position, shape), leading to loosening or annoying sensation of the plates or to exposure and infection; incorrect intermediate wafer; or incorrect final wafer. Soft tissue problems These can include prolapse of Bichat’s buccal fat pad or tearing of the soft tissues of the nasal floor. Mucosal or gingival tears. Excessive tears or stripping may lead to ischemic necrosis of parts of the maxilla in multisegmented maxillae or in cleft patients. Improper maxillary positioning The reasons are manifold: improper condylar seating; inadequate mobilisation of the maxilla; bony interferences with improper manual positioning; insufficient surgical reference landmarks; soft tissue interferences; rotational mistakes (yaw, roll, pitch); improper planning resulting in inadequate intermediate wafer; technical problems with surgical splints, condylar edema, unbalanced repositioning of the upper jaw with cant of the occlusal plane, using internal measurements only without additional extraoral measurements, or navigation systems mainly leading to overimpaction or underimpaction; and initial waxbite not reflecting centric relation. Inadequate post–Le Fort I follow-up. The most common postoperative malocclusions following (multisegmental) Le Fort I or bimaxillary surgery are overextrusion, overimpaction, midline deviations, anterior or posterior open bite, a Class II overjet, a Class III overjet, and a narrow multisegmental Le Fort I. Elastics and interceptive orthodontic 15
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action can correct a number of these postoperative problems, but some of these may persist and constitute a complication if reoperation is necessary. The approximate limits of postsurgical manipulation are usually within 2–3 mm except for midlines, which barely can be corrected (1–2 mm). Anaesthesia-related problems typical for orthognathic surgery. Typical orthognathic surgery–related intraoperative anaesthesia complications relate to difficult intubation, traumatic tube lesions during surgery, induced hypotension–related problems, maintenance of the airway immediately after extubation, and venous thromboembolism.
2.5. REOPERATION – REINTUBATION Return to theatre after bimaxillary orthognathic surgery is supposed to be an infrequent occurrence. This concurs with our experience. Reyneke (2011) focussed on reoperative orthognathic surgery mainly from an occlusal and aesthetic point of view. Choi et al (2009), in a prospective study on blood loss after bimaxillary orthognathic surgery, reported that 3 out of 73 consecutive patients had to be excluded from the study because of re-intubation or re-operation during the hospital stay.
2.6. DEATH A fatal outcome is extremely rare and has only been reported by Washburn and Hyer (1982), Van de Perre et al (1996), and Cunningham and Moles (2009). All cases occurred during the postoperative course and were unrelated to the surgical procedure strictu sensu. Lanigan (1984) reported one death after a massive bleed in the postoperative period following a Le Fort I osteotomy, before discharge of the patient from the hospital.
2.7. BLOOD TRANSFUSION According to Mahy et al (2002), excessive blood loss is the most frequently encountered perioperative problem in maxillary surgery, sometimes necessitating blood transfusion. Transfusion can be considered a complication and will be based either on individual clinical judgement or on strict criteria such as a hemoglobin less than 7 g/dL in a healthy young adult. Blood transfusion in itself can lead to complications, such as the transmission of disease or graft-versus-host reactions. The following determinants have been implicated relative to perioperative blood loss and/or need for transfusion: - perioperative vascular injury - bleeding disorder - duration of operation - type of surgery: monomaxillary, bimaxillary, segmental surgery, added procedures - gender - surgical skills (compression, ligation of vessels, cauterisation) - anaesthesia techniques - application of nasally applied cocaine - acute normovolemic hemodilution - controlled (moderate) hypotension - preoperative injection of human recombinant erythropoietin (not routine in OMFS) - head-up position - the use of tranexamic acid (antifibrinolytic agent) - the use of aprotinin (serine protease inhibitor) - the use of desmopressin
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Controversy certainly exists concerning the relative weights of different risk factors. Risk factors for increased blood loss during orthognathic surgery were reported to be longer operative time, less surgical experience, and female gender in a study by Rummasak et al (2011). In contrast to the general belief, Enlund et al (1997) found that controlled hypotension did not significantly influence duration of surgery, quality of the surgical field, and final result in the 36 patients studied. This group of 36, however, included only 4 bimaxillary operations. Choi and Samman (2008) performed a systematic review of controlled hypotension in orthognathic surgery and concluded that hypotension appears to be effective in reducing blood loss, especially in bimaxillary surgery. Several reports propose a linear proportional relationship between the duration of the intervention and the bleeding volume (Martini et al, 2004; Ueki et al, 2005). The operative time and blood loss are usually greater for bimaxillary surgery than for surgery affecting only the upper jaw or the mandible. Kramer et al (2004) defined hemorrhage as when transfusions of erythrocyte concentrates of foreign donors were required after the autologous blood donation already had been given. In reports concerning blood loss after orthognathic surgery, the definition of blood loss, the way it was measured, and the way it was addressed differ markedly.
2.8. VASCULAR COMPLICATIONS During SSO, the alveolar artery and the facial artery or branches of these can be injured. Branches of the maxillary artery and the retromandibular venous plexus can be injured too. Both during SSOs and IVROs, lacerations of the maxillary artery have been reported (Lanigan et al, 1991). Lai et al (2005) reported on 960 consecutive BSSOs, including two cases with intraoperative vascular complications and another two with late vascular complications. In contrast to the Le Fort I where the cause of the bleeding can be distant to the surgical site, in the mandible, both late and early bleeding complications are related to contact injuries with vessels either through a bony interference or through instrumentation (Lai et al, 2005). Panula et al (2001) reported one lesion of the maxillary artery during BSSO among a total of 515 BSSO procedures. Moen et al (2011) report 2 cases of excessive bleeding after BSSO in 36 patients, without mentioning the source of the bleeding. Problematic hemorrhage from a venous source has not been reported after BSSO. In our series of 1281 consecutive BSSOs, two brisk bleedings were encountered while preparing the medial ramus with the freer to create the pouch for the medial channel retractor. In both cases, vascular clips were able to stop the bleeding, which was located above and posterior to the lingula. Silva et al (2007) report a case of pseudoaneurysm of the maxillary artery after a BSSO. Precious et al (2012) report cases of pseudoaneurysms of the facial artery after BSSO. Bleeding during a Le Fort I osteotomy is caused by the sphenopalatine artery and the descending palatine artery, the pterygoid plexus, and the internal maxillary artery and its collateral branches to the upper jaw. The maxillary artery and its branches are the most vulnerable to injury during pterygomaxillary disjunction. During the maxillary downfracture specifically, the descending palatine artery can be damaged if the maxilla is advanced to a significant degree, intruded posteriorly, or retruded. Lanigan has extensively reported the vascular complications after the Le Fort I osteotomy in a number of articles and has proposed an alternative approach to pterygomaxillary separation, suggesting that this is the highest contributing factor to the arterial system distant to the surgical field (Lanigan et al, 1990b; Lanigan et al, 1991a; Lanigan and Guest, 1993). To date, however, these alternative approaches are not widely adopted, nor is it proven that no early or late vascular incidents may arise using that approach. The incidence of major vascular events after Le Fort I osteotomies is not well documented. Samman et al (1996) reported on 360 orthognathic surgical cases (291 bimaxillary osteotomies) with 5 hemorrhagic complications during the operation but gave no further details. The range of blood loss in that report was between 50 mL and 5000 mL.
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Dhariwal et al (2004), reporting on 9 blood transfusions in 115 consecutive bimaxillary orthognathic procedures, noted that in 5 patients, a transfusion could have been avoided, but that it was appropriate in 4 patients. The reasons were intraoperative problems in two patients, one with a bleeding vessel in the pterygoid region, the other with an aberrant vessel in the maxillary antrum, and two postoperative returns to the theatre to control postoperative bleeding, one facial artery bleeding and one undefined arterial bleeding. Late epistaxis after orthognathic surgery is usually due to the formation of an arteriovenous fistula or a pseudo-aneurysm, but the angiography may fail to visualise the culprit vessel. Anterior and posterior nasal packs and embolisation have been used to treat this complication. Avascular necrosis of parts of the maxilla after Le Fort I osteotomies have been extensively studied by Lanigan et al (1990a; Lanigan, 1997). Risk factors include: ligation of the descending palatine artery and multisegmental Le Fort I osteotomies, particularly with superior repositioning and/or significant transverse expansion. Ischemic complications in a series of 1000 Le Fort I procedures have been reported at an incidence of 0.8%, all of which occurred after a large advancement >9 mm or a segmentation of the maxilla simultaneously with a transversal expansion (Kramer et al, 2004). Kretschmer and Wangerin (2011) reported on 1380 Le Fort I osteotomies and the frequency of segmentation of the upper jaw during the Le Fort I osteotomy at their centre: 605 (43.8%) one-piece maxilla; 212 (15.3%) two-piece maxilla; 557 (40.4%) three-piece maxilla; 5 (0.4%) four-piece maxilla; and 1 (0.1%) five-piece maxilla segmentations. Their observation was that they still had a high degree of 3-piece maxilla segmentations (40.4%) in spite of a tradition of surgically assisted transversal expansion in their surgical patient population. They describe two cases of avascular necrosis of parts of the upper jaw in segmented Le Fort I procedures and advise keeping the transversal expansion during multisegmental osteotomies limited to a maximum 6 mm in the molar area to minimise the danger of avascular necrosis. If more is needed, a SARPE is done first. They also advise against ligation of the descending palatine artery during multisegmental osteotomies.
2.9. INFECTIONS Wound-healing problems are frequent after SSOs. Alpha et al (2006) in a retrospective cohort evaluation observed wound healing problems in 15% of 1066 osteotomy sites, necessitating plate removal in 10% of patients. No adverse effects such as non-union or relapse of the osteotomy site were observed after plate removal. Disturbances of wound healing were not related to the direction of movement of the mandible and were lower when hardware was placed closer to the inferior border. After Le Fort I osteotomy, maxillary sinusitis is uncommon. Kramer et al (2004), in a prospective study of 1000 Le Fort I osteotomies, reported an infection incidence of 1.1%. Maxillary sinusitis accounted for 0.6% and abscess formation for 0.5%. The abscesses occurred only in bimaxillary osteotomies. PereiraFilho (2011) reported an incidence of 4.76% for maxillary sinusitis but in a small sample size of 21 Le Fort I osteotomies. Chow et al (2007) retrospectively reviewed 2910 orthognathic procedures in 1294 consecutive patients and found a postoperative infection rate of 7.4%, of which 58.3% were considered acute infections and 41.7% were considered chronic infections. Abbott (1997) reviewed the literature and found a paucity of well-designed, double-blind prospective studies concerning infections after orthognathic surgery. A problem is the significant difference between authors concerning the definition of infection. Some reports use the following clinical findings to define infections: prolonged alteration in wound healing (ie, wound dehiscence), formation of granulation tissue in the region of the operation wound, local swelling and redness, or abscess formation. Others follow the guidelines set by the US Centers for Disease Control and Prevention: purulent or positive serosanguineous drainage from the surgical site, pain or tenderness, localised swelling and redness of the wound margin and surrounding tissue, an increase of body temperature to greater than 38.5°C after more than 48 hours, and clinical diagnosis of infection. Other reports do not define infection at all. As an example, in a review of perioperative complications following SSO of the mandible, Teltzrow et al (2005)
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documented 35/1264 (2.8%) patients who developed infections. All of these patients needed extraoral incision. One developed osteomyelitis of the mandible. No definition of infection was given, but obviously a more restrictive definition was used because all patients needed extraoral incision. The consequence of different definitions of infections is that the prevalence of infection after maxillary and mandibular osteotomies has been reported to range from 1% to 33%. A number of risk factors are thought to influence infection rates in orthognathic surgery: age, length of surgery, type of orthognathic procedure, type and quantity of osteosynthesis material for fixation (Cataldo et al, 2011), quality of wound closure, the use of prophylactic antibiotics, the period of coverage of antibiotics, bone sequesters, general condition of the patient, smoking (Kuhlefelt et al, 2011), alcohol consumption, magnitude of the gap, and the use of a drain in the sagittal split wound (Spaey et al, 2005). Odds ratios for these risk factors do not exist. For maxillary sinusitis, the following risk factors are added (Pereira-Filho, 2011): formation and retention of a large blood clot, previous sinusitis, secondary dental infection due to iatrogenic apical trauma, tissue ischemia or lack of vascularization, debris in the sinus and sutures, and plates or screws in the sinus cavity. Zijderveld et al (1999), in a randomised, double-blind, and placebo-controlled clinical study, concluded that there was a statistically significant increased risk of having an infectious complication after bimaxillary orthognathic surgery without antibiotic prophylaxis. No significant difference in the incidence of infectious complications was found between a penicillin or a cephalosporin as prophylactic medication. Controversy exists over the duration of antibiotic coverage. Danda and Ravi (2011), in a meta-analysis, concluded that a pre- and postoperative antibiotic regimen in orthognathic surgery is effective but that more trials are needed to standardise a proper regimen. Obviously, no consensus exists about hardware removal in case of early postoperative infection. If done too early, removal can jeopardise stability. Borstlap et al (2004a) recommend plate removal after 6 months, even in case of infection. Most plates in their series were removed before the first postoperative year. Acebal-Bianco et al (2000) observed infectious complications in 53 patients with 41 of them necessitating surgical drainage and only 5 necessitating hardware removal because of the infection. The distribution of these complications was 14 in the maxilla (2.3%) (14/606 Le Fort I) and 36 (4.5%) in the mandible (36/802 sagittal split). Manor et al (1999) recommended plate removal in case of infection, and patient age was the only risk factor they found associated with plate infection. Although most postoperative infections after orthognathic surgery are benign, a recent case report draws attention to a fatal methicillin-resistant Staphylococcus aureus infection after a Le Fort I osteotomy (Smith, 2011).
2.10. TRIGEMINAL SENSORY DEFICIT The intimate proximity of the IAN and the LN to the surgical site during SSOs of the mandible causes postoperative neurosensory disturbances to be common after orthognathic surgery. At present, no purely objective clinical neurosensory testing modalities exist for evaluation of iatrogenic injury to the terminal branches of the trigeminal nerve. All require patient cooperation and are based on a patient response, thus introducing a subjective component to the ‘objective’ process. Furthermore, all testing is commonly performed at the post-injury stage, so no individual baseline testing results are available for comparison and true determination of the magnitude of the resultant damage. This makes the clinical diagnosis complicated and explains the diversity of findings, with scientifically meaningless evaluation categories like ‘good,’ ‘fair,’ or ‘poor’ levels of sensory function. The lack of standardisation of objective methods to evaluate sensory dysfunction after SSOs results in a vast range of reported prevalence of neurosensory disturbance 1 or 2 years postoperatively, with ranges from 0% up to 85% (Wijbenga et al, 2009). Poort et al (2009) reviewed the literature between 1987–2007 and retained 35 studies on nerve injuries after mandibular osteotomies that were prospective and described the neurosensory evaluation method used. They reported a temporary IAN injury rate after mandibular osteotomy ranging from 20% to 98% and a persistent nerve injury rate ranging from 0% to 82%. Poort et al (2009) recommend the light touch test with Semmes-Weinstein monofilaments for grading and additionaly a visual analog scale-based questionnaire to evaluate subjective sensibility. A problem with any sensibility testing which requires
19
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patient’s cooperation, is a possibly poor intraexaminer and interexaminer repeatability (Yilikontiola, 2002). A matter of concern is terminology. While most papers use terms as hypoesthesia, reduced sensitivity, numbness (Westermark et al, 1998b), others use paresthesia as a synonym for identical findings (Hanzelka et al, 2011). Colella et al (2007) performed a systematic review and reported an incidence of persistent nerve impairment of the IAN at 1 year after SSO surgery of 12.8% with objective testing and 18.4% when subjective measures were used. The spontaneous recovery of IAN function after SSO has the greatest improvement in the first 3 months. The cutoff point for a decision concerning the patient with a neurosensory disorder after SSO is currently set at 3 months. If after 3 months the patient has an unacceptably persistent total loss of sensory function, microsurgical repair should be offered as a possible treatment. If the patient has partial but unacceptable recovery of sensation at 3 months after nerve injury, the patient can be followed at regular intervals every one or two months as long as symptoms are improving. Successful outcome decreases with increasing time between injury and its surgical repair. Colella's systematic review (Colella et al, 2007) has shown that the frequency of nerve impairment evaluated by subjective methods was higher than that indicated by studies adopting objective methods, indicating that subjective reporting may include sensory impairments which do not appear to be confirmed by objective testing. From that point of view the subjective reporting has a lesser specificity (=number of true negatives/(number of true negatives + number of false postives)). On the other hand, patient satisfaction does not depend on objective test results but on patients' perception of altered sensation following orthognathic surgery (Phillips et al, 2010). Leira et al (1991) were unable to find false negative patient reports of sensory impairment when comparing subjective reporting and objective IAN testing after SSO surgery, which means that the examiners were unable to demonstrate any detectable deficit in those patients who were selfassessed as normal . Patient assessment of their labial sensory outcome is probably the single most important criterion of the success of the procedure (Pratt et al, 1996). Lemke et al (1998) analyzed data from 116 patients with BSSO advancement surgery. Patients rated their level of subjective problems with swallowing liquids or solids, smiling, spitting, kissing, speaking, eating, and drooling. A significant correlation was observed between hypoesthesia and difficulty in chewing and kissing. No correlation was observed between any of the remaining seven oral behaviors and hypoesthesia.Intrestingly, Lemke et al (1998) needed to exclude several patients who showed significant hypesthesia preoperatively as measured with Semmes-Weinstein Pressure Aesthesiometer filaments. Patients with bilateral hypesthesia did not seem to report more problems than patients with unilateral hypesthesia. An important concern is when authors rely on one method of neurosensory testing, deemed as reliable and objective, to accept equivalence of different techniques of sagittal split osteotomy. Ueki et al (2012) assess trigeminal nerve hypoaesthesia in the region of the lower lip using the trigeminal somatosensoryevoked potential (TSEP) method. The statement they make is that this method is 'highly objective and reliable' as the potential changes of cerebral origin can be detected on the scalp in human subjects following electrical stimulation of the peripheral nerves. This method is subsequently used in a number of publications by the same group (Ueki et al, 2012; Ueki et al, 2007; Nakagawa et al, 1997; Nakagawa et al, 2001; Nakagawa et al, 2003; Hashiba et al, 2007; Hashiba et al, 2008; Takazakura et al, 2007). Jääskeläinen (1999) evaluated TSEP studies to be extremely divergent in regard to the different components, latencies, and neural generators of the waveforms. Teerijoka-Oksa (2003) , reviewing clinical and electrophysiologic tests in nerve injury diagnosis after mandibular sagittal split osteotomy, questions the reliability of these TSEPs-components and makes the additional remark that cortical SEP may overlook peripheral nerve damage because of central amplification of the responses. Westermark et al (1999b) compared purely clinical impressions of the sensitivity of the lower lip and chin with objective assessments of it and concluded that there is a relatively good positive correlation between subjective evaluation and objective assessment of the sensitivity of the lower lip and chin after sagittal split osteotomy of the mandible. They conclude with a clear statement "The patients know quite well how good sensitivity is in their lower lip and chin ". As they rightfully point out, it is only of academic intrest if an objective assessment could identify a subclinical small impairment of sensitivity which is not even 20
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identified by the patient (false negatives). In statistical terms, the patients impression of labial sensibility is a method with high sensitivity. Age is significantly associated with outcome after IAN injury during SSO. The older the patient, the lower the chance for spontaneous recovery after injury of the IAN (Bagheri et al, 2011). Bagheri et al (2010) reported on 54 patients with microsurgical repair after peripheral trigeminal nerve injuries caused by mandibular SSO. The IAN (n=39) was most frequently injured, followed by the LN (n=14), and the long buccal nerve (n=1). The main sensory complaint was numbness in 57.4% of the patients, while 37% complained of pain and numbness, and 5.5% of patients complained of pain without mention of numbness. The most common intraoperative finding in the microsurgical repair group was a discontinuity defect (33.3%), followed by partial nerve severance (27.8%), neuroma-in-continuity (20.3%), and compression injury (18.5%). All the LN injuries (n=14) were partial or complete severances. If a nerve lesion is observed during the surgery and left unrepaired, a meticulous description of the location of the injury is necessary because postoperative visualisation of the severed nerve is routinely impossible. When microsurgical expertise is present, a transected IAN can be repaired immediately (Stockmann et al, 2010). Moen et al (2011) report a transection of the IAN in 1/36 BSSO patients. Tay et al (2008) report 4 operator-witnessed IAN transections during SSO (4/260 SSO patients). Three of the four transections occurred at the anterior vertical osteotomy cut, performed between the first and second lower molar (Tay et al, 2008). They report that the risk of nerve transection is greater if the IAN is more superficial at this point. These findings concur with these of Bagheri et al (2010) and are technique dependent. Advanced MRI imaging techniques that allow for high quality visualisation of the IAN and LN (Terumitso et al, 2011) are not commonly used because of high cost and possibly the limited availability of highresolution, functional, or metabolic-based MRI imaging techniques of the IAN (Miloro and Kolokythas, 2011). If the nerve injury goes unobserved, determining the exact location of the injury is problematic. Bagheri et al (2010) gave a detailed description of the lesions they found: most of the IAN injuries in their study were found at the site of the anterior vertical osteotomy; occasionally, the entire IAN from the vertical osteotomy site to the lingula was missing or entirely replaced with scar tissue, probably the result of crushing the nerve within the canal, or the nerve having been inadvertently displaced out of the canal before application of osseous fixation. The IAN is at jeopardy during SSO when placing a retractor behind the lingula to retract the soft tissues away from the medial surface of the mandible to allow cutting of the horizontal osteotomy (Westermark et al, 1998). Further jeopardy is possible during the vertical osteotomy through cortical bone on the lateral surface of the mandible, anywhere along the inferior alveolar canal between the vertical osteotomy and the lingula, and during the placement of the rigid internal fixation. The panoramic radiograph contains insufficient information about morphological risk factors for neurosensory disturbance during the SSO. Because of the threat of a high radiation load in a young population, CT scans are not routinely taken, if at all, even if the risk factors would be identified. CBCT offers the advantages of 3D imaging at a very low radiation dose and is becoming routinely performed to visualise the position of the mandibular canal. Once the nerve is left unprotected after surgical freeing outside its protected environment of the mandibular canal or the cancellous bone environment, caution is warranted not to injure it. Teerijoki-Oksa et al (2002) performed orthodromic sensory nerve action potential recordings during the SSO and proved that neither the exposure nor the manipulation of the nerve usually had any effect on nerve function. Longer duration of SSO, low mandibular body height, and the location of the mandibular canal at the inferior border of the mandible were identified as risk factors, increasing the probability of injury to the IAN. Aizenbud et al (2012), based on a literature review, listed a number of reported anatomical risk factors for IAN damage during SSO:
21
-
distribution and thickness of cancellous and cortical bone in the mandibular ramus
-
total thickness of mandible through the centre of the mandibular canal
-
thickness of buccal and lingual cortical plates
-
narrowest portion of bone marrow space between the outer mandibular canal and both the buccal and lingual cortices
-
distance from buccal plate to mandibular canal at the second molar
-
distance from mandibular canal to the inferior border of the mandibular body
Chapter 2
-
distance from the mandibular foramen to the highest tip of the lingula
-
distance from the mandibular foramen to the anterior margin of the oblique ridge
-
position and course of the mandibular canal from the mandibular foramen to the mandibular body at the level of the second molar
-
lack of a bone marrow space on the buccal side
-
the transversal thickness of the mandibular ramus
-
distance between the cortical bone of the mandibular corpus and the IAN
-
distance between the surface of the mandibular ramus and mandibular canal
-
the distribution of cancellous bone in the mandibular ramus (between the external plate of the mandibular ramus and the mandibular canal)
-
the distance from the mandibular canal to the external cortical bone in the ramus
-
visibility of the mandibular canal
-
buccolingual width of the mandible at the level of the second molars
-
the distances from the canal walls to buccal and lingual bone surfaces
-
location of the fusion of the buccal and lingual cortical plates that occurs in the upper mandibular ramus (absence of medullary bone in the mandibular ramus)
-
size of the medullary space in the mandibular ramus
-
the width between the mandibular canal and the buccal cortical plate of the ascending ramus
When evaluating the references that are presented in Table 6 of Aizenbud et al (2012), the evidencebased approach reveals the following difficulties: - Papers from Ma et al are in Chinese and need translation (refs 15,16 in Table 6; Aizenbud et al, 2012). - Yu and Wong give only an anatomical description of the lingula based on CT findings (ref 36). - Tsuji et al present anatomical variations of the course of the mandibular canal based on CT (ref 27). - Pilling et al present anatomical CT data on 29 patients concerning the transversal thickness of the lower jaw and the diameter of the ascending ramus of the mandible at the proximal osteotomy site (ref 20). - Muto et al (ref 18) evaluate the cortical anatomy of the ascending ramus at three horizontal planes between the lingula of the ascending ramus and the incisura. - Hallikainen et al (ref 10) assessed the visibility of the mandibular canal with cross-sectional spiral tomography in 55 subjects in an anatomical study. - Smith et al (ref 25) examined the anatomy of the ascending ramus in 50 dried skulls and made 3 frontal sections through the ascending ramus perpendicular to the occlusal plane. - Haase et al (ref 9) examined the anatomy of the ascending ramus with a CT scan. - Nakagawa et al (ref 19) measured postoperatively the distance between the mandibular canal and the ostectomised surface of the mandibular ramus in 28 patients with BSSO set-back osteotomy; no information is given about the type of split; they analysed 30 CT sections through the ramus and gave weighted scores if the distance between the mandibular canal was >2 mm, 1 year) neurosensory disturbance of 8% in the BSSO group and 10% in the distraction osteogenesis group. Permanent infraorbital neurosensory disturbance after Le Fort I osteotomy is rare. Acebal-Bianco et al (2000) report 0% permanent infraorbital neurosensory disturbance after 1 year and only one tooth with lost vitality and needing endodontic treatment. Recovery of infraorbital nerve disturbance after Le Fort I osteotomy is more rapid (±3 months) than recovery of IAN disturbance after SSO (6–12 months) (Schultze-Mosgau et al, 2001).
2.11. TRIGEMINAL NEUROPATHIC PAIN Trigeminal neuropathic pain is probably an underestimated condition after orthognathic surgery. Panula (2003) reported three cases of very severe IAN neuropathy after BSSO, presenting as painful, mostly burning sensations. Two out of three continued to feel pain while one case resolved after a few months. Panula also reported that no nerve was visibly injured in these operations and that a common feature of all of these patients was the relatively older age at operation: 49, 55, and 57 years. Age seems to be a risk factor for the development of neurosensory disturbances (Panula et al, 2001; 2004) together with the degree of manipulation of IAN, the magnitude of intraoperative mandibular movement (Ylikontiola et al, 2000), and the surgeon’s skill (Westermark et al, 1998). The treatment of pain with or without numbness remains a challenging problem in orthognathic surgery. Jääskeläinen et al (2005) examined 58 patients with iatrogenic IAN (29/58) and LN (22/58) sensory deficits. BSSO was responsible for 9 (7 IAN, 2 LN) deficits. In this group of 58 patients, 45% suffered from neuropathic pain. Renton and Yilmaz (2011) evaluated 216 patients with iatrogenic IAN injuries and LN injuries and found that approximately 70% of all patients presented with neuropathic pain, despite the additional presence of anaesthesia, hypoesthesia, and paraesthesia. The injuries following orthognathic surgery in this group were two IAN injuries and one LN injury. Neuropathic pain is clearly part of the clinical picture when evaluating iatrogenic trigeminal nerve injuries. Patients who continue to have pain rather than numbness as their chief complaint after 3 months may benefit from nerve exploration, if at least they have significant abnormalities on neurosensory testing (Renton and Yilmaz, 2011). The rate of somatosensory recovery critically depends on the type of surgical nerve injury after SSO. Demyelinating injuries caused by compression mainly affect tactile afferent fibres (with a thick myelin sheath). These recover quickly and completely by 4 months whereas more severe axonal injuries (eg, after partial laceration) give rise to more persistent abnormal thermal findings up to one year. This persistence results from the fact that warmth perception depends on spatial summation mechanisms and requires more recovery time to accumulate sufficient numbers of afferent fibres for warmth detection. The recovery time for other sensory modalities like touch, vibration, and two-point discrimination is shorter than for thermal perception (Svensson et al, 2011). In the course of compression injuries, the larger A-beta nerve fibres are injured first, followed by the A-delta, and finally, the C fibres (Caissie et al, 2007). Teerijoki-Oksa et al (2003) recommend clinical and electrophysiological tests to detect different types of damage in the sensory afferent fibre population. Table 2.1. is modified after Teerijoki-Oksa et al (2003) and represents the test method for a specific fibre and the way the test is measured. A total absence of blink reflex on neurosensory testing should raise suspicion for IAN transection. Neurography and thermal quantitative sensory testing can document the nerve damage (Jääskeläinen et al, 2005). Small axonal Aβ afferent fibre involvement is essential in the development of neuropathic pain after peripheral nerve damage; a transection of the nerve is not necessary to develop neuropathic pain. A partial axonal injury to the IAN is sufficient because the occurrence of neuropathic pain can be inversely related to the degree of damage. 24
Chapter 2
Table 2.1. Tests for evaluating nerve injury after BSSO Sensory afferent fibre
Test
Dependent measure
Brush-stroke directional discrimination
A-beta
Percent correct
Touch detection threshold
A-beta
Minimum detectable force (mN)
Grating orientation discrimination
A-beta
Minimum spatial period required for discrimination
Mental nerve blink reflex
A-beta
Latency in ms
Nerve conduction study
A-beta
Latency in ms, amplitude in µV
Warm/cold discrimination
A-delta
Percent correct
Sharp/blunt discrimination
A-delta
Percent correct
Cold detection threshold
A-delta
Degree °C for cooling detection
Warm detection threshold
C
Degree °C for warming detection
Heat pain threshold
C
Degree °C for heat pain detection
Warm/cold discrimination
C
Percent correct
Pain without significantly abnormal neurosensory testing results or that is not temporarily abolished by a local anaesthetic block of the suspected nerve is not considered a regular indication for surgical intervention. These patients tend to be operated later than other patients (Bagheri et al, 2011). Jääskeläinen et al (2005) found a significant association between the occurrence of contralateral thermal hypoesthesia to innocuous cold and warm stimuli and neuropathic pain. Their findings indicate that the spread of thermal hypoesthesia in patients with IAN injury beyond the involved classical neuroanatomical distribution seems to be a risk factor for the development of trigeminal neuropathic pain.
2.12. AUTONOMIC NERVE DYSFUNCTION The role of autonomic nerve stimulation in orthognathic surgery has been studied by El Deeb et al (1981). Stimulation of the cervical sympathetic chain reduces blood flow in the ipsilateral tissues after a Le Fort I osteotomy. The role of the sympathetic nervous system in regulating blood flow appears to be modified and does not return to its normal bilateral regulatory status 6 weeks postoperatively in the animal model they used (macaques). Clinically, autonomic nerve dysfunction is exceptional after orthognathic surgery. A case has been reported of secremotor rhinopathy resulting from marked autonomic neural imbalance to the nasal and lacrimal glands after a Le Fort I maxillary osteotomy (Marais and Brookes, 1993). This complication occurred after a Le Fort I maxillary setback procedure. Nowadays, maxillary setback procedures are avoided. In the current technique of the Le Fort I osteotomy, the cuts are too low to damage fibres of the branches of the sphenopalatine nerve that are directed to the nasal mucosa (Sadeghi et al, 1997). Only the palatal branches of the sphenopalatine nerve are sectioned, obviously without adverse clinical outcomes. 2.13. UNUSUAL COMPLICATIONS Steel and Cope (2012) reviewed the literature of complications occurring after orthognathic surgery up to August 2010. In total, the content of 180 papers on the subject was reviewed (Steel and Cope, 2012). They define ‘complication’ as an unintended consequence of the surgery that causes harm to the patient, occurring either intraoperatively or early or late postoperatively. As ‘unusual’, they refer to a complication that may not normally be considered as part of the consent or surgical planning process. The following complications were categorised as unusual or rare: injury to cranial nerves II, III, IV, VI, VII, VIII, X, XI, and XII; ophthalmoplegia; neurosensory deafness; secretomotor rhinopathy; Frey syndrome; altered tear secretion; hemolacria; blindness; Adie’s tonic pupil; retrobulbar hemorrhage; brain abscess; actinomycosis; bone graft donor-site infection; osteonecrosis of maxilla/mandible; avulsion of maxilla; 25
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condylar dislocation; condylar resorption (progressive, idiopathic, condylar atrophy); vomero-sphenoidal disarticulation; cerebrospinal fluid leak; cerebrovascular accident (stroke, subarachnoid hemorrhage); severe hemorrhage; arteriovenous fistula; false aneurysm; carotid-cavernous sinus fistula; cavernous sinus thrombosis; malignant hyperpyrexia; herniation of tube cuff; tube sectioning; conversion disorder; severe clinical depression; acute pulmonary edema; apnea; pneumomediastinum; pneumothorax; surgical ciliated cyst; traumatic neuroma; dysphagia; compartment syndrome; perforated lateral nasal wall; perforated septum; oroantral fistula; oronasal fistula; loss of orthodontic bracket into airway; severe eustachian tube malfunction; ischemic finger injury; and death. In addition to this list, Kim et al (2011) presented a case of descending necrotising mediastinitis and permanent injury to the facial nerve. Tosun et al (2005) presented a case of subcutaneous cervicofacial emphysema associated with Munchausen’s syndrome. Postoperative anorexia can be added to that list (personal observations). Although Steel and Cope (2012) include the Vth cranial nerve in their list of rare complications, this cranial nerve is particularly associated with damage after orthognathic surgery. Steel and Cope's view is that it is inappropriate to routinely discuss all of these rare complications with the patient. Of interest, Steel and Cope (2012) in the same article also list the more common complications of orthognathic surgery: postoperative nausea and vomiting; respiratory difficulty; neck pain; localised skin burns; temporary tympanomimetic changes; acute infection; chronic infection; maxillary sinusitis; excessive bleeding; soft-tissue damage; tooth injury; loss of pulpal vitality; periodontal disease; gingival recession; nerve exposure; IAN disturbance; LN disturbance; temporary taste disturbance; instrument fracture; instrument loss; screw loss; screw loosening; foreign body; buccal plate fracture; lingual plate fracture; bad split; incomplete or undesirable fracturing; malunion; condylar resorption; TMJ effects; relapse, both skeletal and dental; and malocclusion.
2.14. VELOPHARYNGEAL FUNCTION - SPEECH Orthognathic surgery normally improves speech errors related to malocclusion. Cleft patients with a borderline velopharyngeal function or with pre-existing velopharyngeal impairment (Chanchareonsook et al, 2006), however, may suffer from deterioration of speech after large advancements. This risk is undefined because no prospective, randomised controlled studies exist (O'Gara and Wilson, 2009). In a prospective study in 52 patients, Murphy et al (2011) report moderate to large improvements in speech in 13 patients (25%) after orthognathic surgery, but in 4% of the patient sample a deterioration of speech was determined. The majority in their sample were Class III maloccusions. Van Lierde et al (2006) found no improvement in speech in thirteen Class II patients, corrected with a BSSOadvancement osteotomy.
2.15. TEMPOROMANDIBULAR JOINT DYSFUNCTION Patients with pre-existing TMJ problems can get better or worse after surgery. Patients without preexisting TMJ problems can also develop postoperative TMJ-related issues or even condylar resorption. Laskin et al (1986) warned about offering orthognathic surgery to patients presenting with a major skeletal disharmony and symptoms of mandibular pain and dysfunction based on an erroneous causal association, because at that time, no sufficient scientific data were available to sustain the claim the orthognathic surgery is beneficial for TMJ symptoms. Westermark et al (2001) followed 1516 orthognathic surgery patients for temporomandibular joint dysfunction, but this group included different operation techniques, different movements (set back, advancement) and different fixation methods with and without maxillomandibular fixation. According to their data, there is an overall beneficial effect of orthognathic surgery, but the most striking finding was that patients with mandibular asymmetry and severe pre-operative temporomandibular joint dysfunction had very favorable outcomes. Jerjes et al (2011) performed a systematic review of the available literature between 1980–2008 and concluded that TMJ symptoms are significantly reduced after orthognathic treatment of the lower jaw for patients with preoperative symptoms. A percentage of dysgnathic patients who were preoperatively
26
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asymptomatic can develop TMJ disorders after surgery, but this risk is low. Al-Riyami et al (2009) reached the same conclusion in a meta-analysis of the available literature. A more critical systematic review of the subject by Lindenmeyer et al (2010) concluded that insufficient scientific data are available to advise orthognathic surgery as a relief for TMJ symptoms and warned against encouragement of unnecessary surgery that may upregulate TMJ disorders to intractable pain and occasional litigation. This position is no different than that of Laskin et al in 1986. Postoperative TMJ complications include pain, joint sounds, limited opening of the mouth, fibrous ankylosis (Nitzan and Dolwick, 1989), and condylar resorption. Female patients with an abnormal psychological profile seem to be at an increased risk for persistent postoperative TMJ pain after orthognathic treatment of an open bite deformity(Aghabeigi et al, 2001). Postoperative immobilisation in itself does not seem to constitute a surgical risk factor for the development of postoperative TMJ disorders (Nemeth et al, 2000). Many other surgical risk factors that have been associated with postsurgical condylar resorption are not retained in the systematic reviews as a probable cause for postoperative TMJ dysfunction. In a systematic literature review, no final conclusions could be drawn concerning the influence of rigid fixation to the TMJ after BSSO advancement (Kersey et al, 2003). Yamashita et al (2011) reported a consistently higher Helkimo index score in a patient group with screw fixation versus a group with miniplate fixation after a BSSO advancement in a long-term study, but hard data are lacking to conclude that non-compressive screw fixation would be more damaging for the TMJ than miniplate fixation at a clinical level. Becktor et al (2008) indicated that transverse displacements of the proximal segments do occur after BSSO surgery with both miniplate and lag screw fixation techniques. The use of passively adapted miniplates is no guarantee that TMJ dysfunction will be avoided after SSO. A relevant prospective, multicentre study was conducted under the auspices of the Strasbourg Osteosynthesis Research Group (SORG) in which seven European departments of oral and maxillofacial surgery participated. From this study, Borstlap et al (2004a, b, c; 2005) reported that in 56% of the 87 patients who had pre-existing signs and symptoms of TMJ dysfunction, these signs and symptoms had disappeared while in 22% of the 135 patients without pre-existing TMJ dysfunction symptoms, symptoms developed, indicating TMJ dysfunction. Kallela et al (2005) used anamnestic and clinical TMJ dysfunction indices in 40 patients who underwent BSSO surgery with two biodegradable positioning screws as the fixation method. Their mean follow-up was 2.2 years. According to the anamnestic dysfunction index, the TMJ findings improved in 18 patients (45%), remained unchanged in 17 (42.5%), and worsened in 5 (12.5%). According to the clinical dysfunction index, the TMJ findings improved in 10 (25%), remained unchanged in 26 (65%), and worsened in 4 (10%) (Kallela et al, 2005). A total of 118 adult patients were prospectively followed for at least 1 year and examined using the Helkimo Anamnestic and Clinical Dysfunction index. Øland et al (2010) identified a marked presence of oral dysfunction symptoms among patients seeking orthognathic surgery indicating that reported signs of TMJ were more prevalent among patients before initiation of treatment than among the age- and sexmatched controls. A total of 76 patients (64.4%) reported severe dysfunction at the beginning of the treatment, and 24 patients (20.3%) reported severe dysfunction at the end of the treatment. Only 9.3% 11 patients (9.3%) without clinical dysfunction at the time of inclusion developed some dysfunction during treatment. The assessed and perceived functional postsurgical outcome correlated significantly with patients’ subjective post-treatment satisfaction levels (Øland et al, 2010). At our centre, TMJ symptoms are not a contraindication to proceeding with orthognathic surgery unless additional signs and symptoms qualify the patient as high risk for condylar resorption. Otherwise, the stance is to proceed with orthognathic surgery and evaluate residual symptoms at the 12-month followup visit. A group of 173 patients were evaluated before and 1 year after BSSO surgery. The routine preoperative exam checked TMJ complaints, maximum opening of the mouth, the pattern of mouth opening, the lateral excursions of the mandible, joint pain upon palpation, and joint sounds. This exam was repeated at the 12 months postoperative follow-up period. Most patients (100/173=57.80%) had no complaints before surgery and remained without complaints afterward. Disappearance of symptoms in patients with pre-existing TMJ-dysfunction signs and symptoms was established in 56 patients (56/173=32.37%) at the 1-year postoperative follow-up visit. This value represented the majority of the patients with pre-existing complaints or symptoms (56/68=82.35%). A small number (12/173=6.94%) of patients had complaints before surgery and did not improve after surgery. An even smaller group (5/173=2.89%) was symptom free before surgery and developed
27
Chapter 2
complaints and symptoms after BSSO surgery. The mean age (32.9 years) of the patient group that showed no improvement was higher than the overall average age in this chart review (26.9 years). In that no-improvement group, we identified one patient who needed arthroscopic surgery, which resolved the complaints. The four other patients developed TMJ sounds without, however, limitation of the opening of the mouth. These findings are in line with the findings of Borstlap et al (2004a). The fact that a high number of patients became complaint free after surgery might be attributed to the early removal of osteosynthesis plates in a high number of patients at our centre (Falter et al, 2011). Borstlap et al (2004c) observed that clicking and preauricular pain 3 months postoperatively after BSSO surgery were significantly correlated with the radiographic alterations of the condyle during the follow-up period and speculated that an intervention within 3 months, such as removal of osteosynthesis plates, could possibly ease unfavourable loading of the joints by allowing for some adaptation at the osteotomy site. This idea has yet to be evaluated in further studies. Osteosynthesis with miniplates allows for sufficient condylar remodelling even with manual repositioning of the condyle with a ramus pusher during surgery. 2.16. CONDYLAR RESORPTION Condylar resorption represents pathologic and destructive remodelling of the condyle leading to a progressive decrease in condylar mass and alteration of condylar shape. De Bont and Stegenga (1993) subdivided condylar resorption into primary (idiopathic) and secondary, depending on the presence of predisposing factors. Posnick and Fantuzzo (2007) instead differentiated between idiopathic condylar resorption (ICR) when the origin is unknown and progressive condylar resorption (PCR) as a more general term for known or suspected etiology (juvenile rheumatoid arthritis, lupus erythematosis, trauma, steroid use, etc). Condylar resorption has a female preponderance with a 9:1 ratio. The pathogenesis of condylar resorption remains unclear. One theory correlates it with increased, abnormal joint loading and subsequent pressure resorption and may occur after orthodontics, orthognathic surgery, occlusal therapy, internal derangement, parafunction, trauma, and unstable occlusion (Arnett et al, 1996a, b; Gunson et al, 2012). Another theory postulates that the mechanism of condylar resorption is the same as that seen in avascular necrosis of the femoral head. Others believe that condylar resorption may be the result of loss of the normal remodelling capacity of the condyle caused by factors such as age, systemic illness, and hormones (Gunson et al, 2009). The incidence of condylar resorption after orthognathic surgery is reported to range from 1% to 31%, depending on various nonsurgical and surgical factors (Papadaki et al, 2007; Dicker, 2012). The first radiologic signs of resorption usually present at 6 or more months postoperatively. Mandibular advancement, maxillary impaction, mandibular autorotation, and bimaxillary osteotomies can induce condylar resorption. Condylar resorption after orthognathic surgery should be suspected when relapse occurs and in cases of an apparent postoperative open bite, an increasing overjet, or a receding chin. Limited mandibular range of motion, TMJ symptoms, and pain may be present. If pain and TMJ sounds occur in the first few months after orthognathic surgery, this should be suspicious for condylar changes occurring in the following months. Panoramic radiographs, serial lateral cephalograms, CBCT, technetium isotope bone scan, and positron emission tomography–MRI may be used to establish the diagnosis. Both non-surgical and surgical risk factors have been implicated in resorption, but without conclusive evidence. Non-surgical risk factors include age, sex, open bite, antecedent TMJ dysfunction, presurgical orthodontics, condyles with a posterior inclination, small, thin condyles, a high mandibular plane angle with a low posterior-to-anterior facial height ratio, posterior rotation of the mandible with increased overjet, estrogen imbalance, nutritional status (dietary omega-3 fatty acids, vitamin D), individual patient genetic susceptibility, bruxism, repetitive oral habits, displaced articular discs, adolescent ICR, reactive arthritis, and connective tissue and autoimmune diseases. Surgical risk factors are controversial. Autorotation of the mandible, vigorous positioning of the proximal segment during mandibular surgery, rotation of the distal fragment (clockwise, counterclockwise), rotation of the proximal fragment (clockwise, counterclockwise coronal, axial-torque-), mandibular surgery in steep high-angle mandibles, amount of advancement, rigid fixation, duration of maxillomandibular fixation, the postoperative use of heavy Class III elastics, and improper occlusal splint fabrication all have been implicated as possible risk factors. A systematic review of the literature concerning condylar resorption up to August 2006 allowed Gill et al (2008) to identify the following risk factors: females with mandibular retrognathia associated with an increased mandibular plane angle; presence of pretreatment condylar atrophy; surgically induced 28
Chapter 2
posterior condylar displacement; and upward and forward rotation of the mandible. In this review, pretreatment TMJ dysfunction, type of fixation (wires, screws, or plates in BSSOs), and posteriorly inclined condylar necks were not identified as risk factors for condylar resorption (Gill et al, 2008). Secondary surgery to treat the malocclusion resulting from condylar resorption is frequently followed by additional relapse. The cause of condylar resorption is multifactorial, but because it is difficult to identify risk factors at a statistically and clinically significant level, expressing the existing risk factors as odds ratios has not been possible to date.
2.17. MUSCULAR DYSFUNCTION CHEWING ABILITY Stockmann et al (2010) followed 66 patients for 8 years in a prospective study. They demonstrated that all 66 patients, undergoing a BSSO according to Obwegeser-Dal Pont, regained their preoperative maximum incisal edge distance at 1 year postoperatively, with a minimum incisal edge distance at the second week postoperatively. Osteosynthesis was performed with three to four screws on each side in triangular geometry using the transbuccal approach. Postoperatively, no intermaxillary fixation was used, but occlusion was guided with intermaxillary elastics. The results were the same for both bioresorbable screws and titanium screws. Ueki et al (2008) demonstrated similar results at 1 year postoperatively in 68 patients treated for mandibular prognathism with BSSO, IVRO, Le Fort I advancement, or bimaxillary surgery. The maximal opening of the mouth never fully regained the preoperative values and was at its minimum 1 month after surgery. There was a correlation between the duration of the postoperative maxillomandibular fixation period and the maximal opening of the mouth, which was significant when measured at 1 and 6 months, but without any significance any more at 1 year postoperatively or later. The osteosynthesis was performed with miniplates and monocortical screws. Yang et al (2007) followed 63 patients with a sagittal split set-back osteotomy prospectively for only 6 months, but at that point, lateral movements of the joint had already returned to their original values as had the protrusion ability of the mandible. The maximum opening of the mouth was, however, as could be expected with such a short follow-up, still not returned to the preoperative values (33.71±7.74 vs 36.25±6.01 mm, statistically significant difference). Their protocol was a Hunsuck-modified sagittal split set-back, stablised with miniplate osteosynthesis and monocortical screws. In a prospective study, Borstlap et al (2004a, b, c) evaluated 222 patients who underwent a BSSO for mandibular advancement and found that all patients returned to a normal maximal mouth opening postoperatively with only a slight, non-significant difference in opening between the preoperative and 2year postoperative period. Both setback and advancement opening of the mouth. The slight fact that the interincisal opening orthodontically altered position of
osteotomies with rigid fixation allow patients to return to their initial differences found are usually non-significant and must be judged by the is influenced both by the surgical movement of the mandible and the the incisors.
A new or persistent mouth opening problem should be a ‘red flag’ for an intra- or extracapsular TMJ problem. Shabtaie and Schwartz (2000) reported a case of extra-articular ankylosis with an interincisal opening of the mouth of 20 mm resulting from a failed mandibular osteotomy and subsequent bony ankylosis between the mandibular ramus and the mastoid. Limited opening of the mouth after a sufficient length of time postoperatively should lead to suspicion of TMJ problems or even an active condylar resorption, depending on the associated complaints and symptoms. We were unable to find any report of decreased chewing performance after orthognathic surgery. A systemic review by Magalhães et al (2010) concluded that orthognathic surgery is capable to improve masticatory performance by correcting malocclusion and increasing occlusal contact areas providing greater dental support. It is unclear which other factors influence increased bite force and EMG activity and/or improved chewing performance after orthognathic surgery: changes in of muscle size; sensitivity of teeth, muscles, and the temporomandibular joints; the patients’ willingness to exert maximum effort (Lee and Yu, 2012; Ellis et al, 1996). For retrognathic patients, requiring a BSSO advancement, only 29
Chapter 2
patients with reduced chewing performance seemed to benefit from surgical correction of the malocclusion and it may take up to 5 years before this improvement gets significant (van den Braber et al, 2006).
2.18. RELAPSE Knowledge of the nature of relapse is mandatory for understanding the value of literature and data collection. Relapse occurs at three sources: the condyle, the osteotomy site, and the dentition. The condyle can be a source of relapse both in the short term and in the long term. Condylar positioning is a difficult part of the SSO. Both manual methods and methods employing positioning devices have been used, without consensus about which method is the standard of care. A condylar sag will be evident immediately after release of intermaxillary fixation, whether perioperatively or after 6 weeks, or after a few days when edema has regressed. Rigid fixation has had a huge impact on this type of relapse because rigid fixation allows the perioperative release of the maxillo-mandibular fixation to check the occlusion. However, even with rigid fixation, the effect of edema at the condylar tissues will be masked during surgery. Rigid fixation is not always possible in case of a complicated bad split or in case of an IVRO. In contrast to a condylar sag, the proximal fragment can be overrotated backwards, possibly leading to a relapse in Class III patients (Proffit et al, 1996). Condylar resorption, which occurs in response to compression and remodelling of the joint structures, may begin from 9 to 18 months after surgery. Only sufficient follow-up will reveal this kind of relapse. Condylar growth may occur when the osteotomy is performed in a child who is still growing. In a skeletal Class III patient, it therefore may be difficult to know which part is relapse and which part is continued growth of the mandible. Only sufficient follow-up will reveal this kind of relapse. Healing over the osteotomy gap constitutes secondary gap-healing and usually occurs within 6–8 weeks. A number of factors influence the healing at the osteotomy gap: -
amount of gap
-
stability of the gap between the proximal and distal bone segments
-
type of fixation: some instability at the osteotomy gap is inherent ot wire osteosynthesis; this kind of relapse has, for a large part, been solved by rigid fixation techniques
-
additional intermaxillary fixation
-
age
-
gender
-
smoking status
-
general medical conditions
-
infection
-
gap filling with autologous or alloplastic material
-
amount of bony overlap segment
between
proximal
condyle-bearing
segment
and distal tooth-bearing
-
vestibulo-lingual width of the gap between the bony fragments at sites of bony overlap
-
amount of paramandibular connective tissue stretch (Arnett, 1993) consisting of skin, subcutaneous tissue, muscle, and periosteum, which produces force that pulls the tooth-bearing fragment posteriorly after advancement
-
tension at both sides of the gap
The influence of postoperative elastics should not be underestimated in the early postoperative period. In counterclockwise rotations of the mandible in high-angle mandibles, the muscle pull of the masticatory and suprahyoid muscles on the distal segment is believed to exert sufficient force for vertical relapse. Rigid fixation with one miniplate stabilises the horizontal component of the mandibular advancement, but less so the vertical component of the counterclockwise rotation of the distal segment (Matsushita et al, 2011). Non-union over an osteotomy gap (Teltzrow et al, 2005) happens when the gap at the overlapping area 30
Chapter 2
between the proximal and distal fragments is too wide for spontaneous bone healing; when the proximal bone fragment gets necrotic because of extensive soft tissue stripping or interposed soft tissues; or when the clot or interposed graft is lost due to necrosis or infection. If non-union leads to loosening of the rigid fixation, clockwise rotation of the proximal fragment can occur usually with distalisation of the toothbearing fragment, leading to relapse. In a systematic review, Joss and Vassalli (2009) proposed a multifactorial process to explain relapse after BSSO advancement osteotomies: proper seating of the condyles, the amount of advancement, the soft tissue and muscles, the mandibular plane angle, the remaining growth and remodelling, the skill of the surgeon, and preoperative age. Patients with a low mandibular plane angle have increased vertical relapse whereas patients with a high mandibular plane angle have more horizontal relapse. Advancements in the range of 6 to 7 mm or more predispose to horizontal relapse. Joss and Vassalli (2009) identified 488 articles dealing with rigid fixation after BSSO surgery and reported little difference regarding skeletal stability between bicortical screws of titanium, stainless steel, or bioresorbable material and miniplates in the short term, but found a greater number of studies with larger skeletal long-term relapse rates in patients treated with bicortical screws instead of miniplates. Interestingly enough, Dimitroulis (1994), in a discussion on bone grafting in orthognathic surgery, stated that “where the gap between osteotomised segments of bone is large enough to create a substantial likelihood of relapse, then an interpositional bone graft is highly recommended“. He agreed, however, that it is unclear what the minimum gap dimensions are between osteotomised segments to recommend grafting. This is especially true in mandibular advancements where the standard of care to date consists of any form of rigid fixation without bone grafting. To prevent counterclockwise rotation of the distal fragment during an osteotomy, some centres include a Le Fort I posterior intrusion in the treatment protocol. Others do not fear a BSSO with a moderate counterclockwise rotation to close an anterior open bite. Both successful results (Ayoub et al, 1995; Reyneke et al, 2007; Stansbury et al, 2010) and disappointing results (Frey et al, 2007; Hwang et al, 2000; Mobarak et al, 2001) with this approach have been reported. Dental relapse will occur after debanding of the orthodontic devices, which is usually between 3 months and 18 months postoperatively. For the patient, relapse will be defined as a measure of overjet and overbite because these features are visible to the patient. For the surgeon, however, this kind of clinical perception of relapse makes little sense. Dental compensation for skeletal relapse is common during the postoperative orthodontic treatment period before debanding. Even after debanding, dental compensation continues long after the surgical treatment. Again, dental changes can occur in both ends, depending on the amount of change in dental inclination resulting from orthodontics to begin with. For the surgeon, relapse will be defined at different possible landmark points on the cephalometric evaluation of a lateral radiograph. Treatment responses are measured by superimposition of serial tracings on relatively stable bases. A prospective study by Borstlap et al (2004a, b, c) in 222 patients with BSSO advancement surgery revealed 35 patients with occlusal relapse. All of these patients had pre- and postoperative orthodontic treatment. Skeletal relapse was found in 24 patients, and dento-alveolar relapse was seen in 11 patients. In 25 patients, occlusal relapse was less than 3 mm, and only 10 patients had an occlusal relapse of more than 3 mm, none requiring re-operation. The radiographic examination of the condyle in the relapse group revealed no condylar changes in 20 patients (20/35), condylar resorption in 8 patients (8/35), and condylar remodelling in 7 patients (7/35) (Stoelinga and Borstlap, 2003). Relapse is defined as a postoperative movement either towards the preoperative position or in the same direction as the surgery. Because relapse can occur in both directions, any study revealing the ‘mean’ relapse places positive and negative values in one basket, rendering a meaningless value as overall relapse. Another methodological issue is that the distribution of postoperative changes is not ‘normal’. Most of the changes occur in only a few of the patients. Statistical ‘means’ are very misleading in that respect and mask clinically important subgroups of patients. Therefore, Proffit et al (2007) prefer to consider the percentage of patients with clinically significant changes than the mean changes. In doing so, however, comparison among different relapse studies becomes more difficult.
31
Chapter 2
Because relapse studies try to establish the linear change of an achieved surgical movement, it is obvious that only similar surgical movements can be compared with each other. Given the difficulties mentioned, studies reporting relapse often will have limited sample sizes, have limited duration of follow-up, and involve different surgical techniques being applied in the same sample or problems with the cephalometric evaluation method used. In addition, because most relapse studies rely on the lateral cephalogram to compare outcome, a number of limitations inherently apply to this study method. Relapse is four dimensional, with vertical, transversal, sagittal, and rotational components that occur concurrently. On the lateral cephalogram, only sagittal and vertical components are detected. Errors in cephalometrics are inherent and unavoidable. They can derive from various sources (Athanasiou, 1995). In orthognathic patients, it normally concerns non-growing patients, which eliminates one source of error. But three other kinds of error are associated with cephalometric superimposition. The first kind of error finds its origin in the cephalometric imaging technique itself. Each radiographic device that produces lateral cephalograms has its own magnification factor and distortion. The manufacturer's specific magnification factor applies only to the midsagittal structures. Structures on the left side of the face may only be 6-8% enlarged compared to those on the right side, which may be magnified up to 14%. It is normal to see bilateral structures not superimposed over one another (lower border of the mandible, posterior border of the ramus). The divergence of the X-ray beam may mislead in that the lower borders of the mandible can become radiographically superimposed due to this phenomenon, even if there is a clinical mandibular asymmetry. The distance of the object to the film must remain constant to achieve the same magnification factor on serial images. When a study has not accounted for the radiographic magnification error in the results or conclusions, no comparison is possible with other studies if radiographic equipment has been used with different magnification factors. The problem is not different from orthodontics, where Dibbets and Nolte (2002) concluded that the distances listed in commonly used cephalometric atlases differ greatly because of different magnifications and cannot be compared directly and that correction to natural size is essential when comparing cephalometric distances from different sources. That problem is still present when hard copies are traced. When using cephalometric software on directly digital cephalograms, this problem can be accounted for because correction for the magnification is a standard built-in feature. Future development will probably use CBCT-derived lateral cephalograms, without magnification error. CBCTderived cephalograms do not suffer from magnification and suffer less from distortion-related problems inherent in 2D projections (van Vlijmen et al, 2009 a, b). If CBCT images are to be used in follow up of patients post orthognathic surgery, dose considerations should be solved. However, there is no current practice for follow-up studies concerning relapse. A number of patient-related factors are important when choosing the lateral cephalogram as method of evaluation. The rotation of the head is an issue when projected to a two-dimensional film, whether analog or digital. The positioning of the head in the cephalostat must be controlled when making serial films for superimposition. If in one film the head is rotated and not in the second, there will be foreshortening of certain structures and double images of others. A slight tilt of the patient’s head can induce a different level of the lower border of the mandible, mimicking a vertical asymmetry between the mandibular halves. In serial cephalograms, errors can be induced depending on the lower border chosen. The lips need to be repositioned in rest in comparisons of the soft tissues. This is not easy to achieve in each individual patient at each interval. The head should always be directed in the same direction in serial cephalograms. Particularly of importance is the control of the position of the lower jaw at T0, the immediate postoperative lateral cephalogram. In the days of non-rigid fixation, patients all had maxillo-mandibular fixation with wires. Regardless of edema, teeth and jaw position were maintained in position in the immediate postoperative period. Nowadays, with the patient either without elastics or with slight elastics, it is often very difficult for the patient to keep the teeth together in the position that existed at the end of the operation, due to edema. Thus, an immediate postoperative lateral cephalogram is often useless.
32
Chapter 2
When the second radiograph is postponed to the sixth week, the principal postoperative cephalogram is missing, and data about early relapse (up to the sixth week) will be missing.
lateral
If a surgical splint is used, cephalometric analysis of the surgical result should be considered immediately after removing the intermaxillary splint. T0 should be defined, and if one is to compare outcome studies, the interval between the operation and T0 seriously affects comparability among studies. Another source of error includes landmark identification. Most orthodontic textbooks have chapter on cephalometric landmarks. Their description remains sufficiently imprecise, so that even experts tend to disagree about their exact location (Jacobson and Jacobson, 2006). In orthognathic surgery, cephalograms are usually superimposed on SN (sella-nasion). There is no significant difference in landmark identification between hand and computer tracing (Roden-Johnson et al, 2008). In outcome studies, however, often different landmarks are chosen to compare the results; because both angular and linear measurements are possible in cephalometrics, it is not always possible to compare results. The reliability of cephalometric landmark identification is affected by the nature of cephalometric landmarks, the resolution, sharpness, and image contrast of digital images, and the training level or experience of observers (Chen et al, 2004). Chen et al (2004) allowed 12 trained observers to compare soft copy and hard copy versions of storage-phosphor digital cephalometric images and found important location differences for landmarks that are important in surgical outcome studies: landmark nasion (1.40±1.58 mm), sella (1.61±1.18 mm), and pogonion (2.87±2.12 mm). Direct digital cephalometric radiography equipment with a vertical CCD sensor (charged-coupled device) requires that the patient remain motionless during the scanning process for the entire 15 s. In the immediate postoperative radiograph, this often is difficult to achieve, introducing overlap and motion artefacts. This kind of motion error was absent in the analog radiographic equipment. Point A is very often compromised by upper jaw surgery during the Le Fort I osteotomy, and postoperative point A cannot be compared with preoperative point A when SNA is removed during surgery with surgical adaptation of that bony region. In addition, point A might be compromised by surface remodelling (Wall and Rosenquist, 1996) after a Le Fort I osteotomy, not correctly reflecting a change of segment position. Abeltins et al (2011) described how they surgically affected SNA and point A during surgery, necessitating use of a traced template of the maxilla on the postoperative cephalogram to account for the surgically altered SNA and point A. Another source of error concerns tracing errors (Lambert et al, 2010). The skill and training of the person who traces cephalograms are variables that affect error magnitude in landmark identification. Intra- and interobserver calibration is required when pursuing cephalometric comparisons. Using dry skulls, Major et al (1994) showed that there is a considerable range in the magnitude of error with different horizontal and vertical values. Interexaminer landmark identification error was significantly larger than intraexaminer error for many landmarks, which favours having one examiner do the cephalometric follow-up tracings. To statistically assess reproducibility, one measures interobserver and intraobserver error rates, which then are expressed as intraclass correlation coefficients or kappa statistics. These indexes establish whether the examiners can provide uniformity and reproducibility in cephalometric analyses. Kappa makes no distinction among various types and sources of disagreement. Interobserver agreement is tested using Cohen's kappa for the second reading of individual observers and Spearman's rank correlation for the mean of both readings from each observer. A major influence on the outcome and relapse of orthognathic surgery is the amount and direction of surgical movement. This has been extensively studied over the long term by Proffit et al (1996, 2007). The BSSO advancement has been most extensively studied. A systematic review by Joss and Vassalli (2009) concluded that BSSO for mandibular advancement seems less stable than BSSO set-back in the short and long terms. Bicortical screws of titanium, stainless steel, or bioresorbable material show little difference regarding skeletal stability compared with miniplates in the short term. A greater number of studies with larger skeletal long-term relapse rates were evident in patients treated with bicortical screws instead of miniplates. Advancements in the range of 6 to 7 mm or more predispose to horizontal relapse (Joss and Vassalli, 2009).
33
Chapter 2
To illustrate how these issues affect the orthognathic literature, 6 papers discussing relapse are highlighted here (Table 2.2) that have been published in peer-reviewed journals with an impact factor >1. All six suggest a set-back technique of the lower jaw with SSO. Careful assessment of these papers reveals the following concerns: -
Type of surgery: 3 out of 6 papers discuss set-back involving bimaxillary surgery, including genioplasty when pogonion is taken to measure the result.
-
Control group: in 1 paper, the ‘control’ group was retroactively chosen as a group with >4 mm displacement; 1 paper compares bioresorbable screws to titanium screws, 1 paper compares bicortical screw fixation to monocortical fixation, and 3 papers involved a follow-up study of 1 type of osteosynthesis.
-
Study design: only 2 studies have an explicit statement about the study design.
-
Type of fixation: Papers mention rigid fixation miniplates (2), rigid fixation with titanium screws (2), mixed plates and screws (1), and mixed titanium and bioresorbable (1).
-
Type of compression in case of bicortical screw fixation: not stated, lag screw (1), positioning screws (?).
-
Sample sizes: All sample sizes were small except the paper of Hsu et al (2012).
-
Surgical wafer: Was one present at the time of taking the first postoperative cephalogram? If present, how was this accounted for in the tracing?
-
Tracing: Three papers describe manual tracings, two describe computerised tracings, and one provides no description.
-
Superimposition method of tracings: Only 1 paper describes this.
-
Intra- and interobserver agreement: Four papers involve one observer and two provide no information.
-
Landmark identification error: This value varies from 34
145
35
24.1%
17
11.7%
TOTAL
570
157
27.5%
78
13.7%
Age groups (years)
# osteotomies
# plate removals
30 y). Risk factors include the necessity of detachment of the nerve and genioplasty. - Neuropathic pain does not occur after Le Fort I osteotomies or after SARPE procedures or isolated genioplasties; neuropathic pain will develop after BSSO surgery in 0.5% of the cases in which axonal damage of the nerve most likely has occurred. Neuropathic pain needs early intervention as soon as the diagnosis is established: All sources of compression, mal-union, and pseudarthrosis need to be addressed, and the nerve must be embedded in an environment that can provide nutrition and healing. The same attitude has been successful in traumatic anaesthesia of the IAN and LN after condylar fractures with displacement. - Bad splits occur in 0.70% of splits in experienced hands and more frequently in beginning teams; a bad split does not prevent the achievement of a good occlusion and does not seem to be a risk factor for nerve damage. Angle class classification and the type of facial deformity do not seem to be predisposing risk factors. Age is a predisposing risk factor, as is limited surgical experience. - In 25.7% of orthognathic surgery cases, miniplates are removed, mainly because of infection or clinical irritation; age is only a predisposing factor in case of infection. It seems advisable to place the miniplates 279
Chapter 17
closer to the lower border than to the upper border to have periostal coverage; the further away the screws are from the osteotomy gap, the less the chance of microfractures and bone sequestration and necrosis. Overtightening the screws should be avoided. Measures to prevent infection deserve special attention in older patient groups. - A permanent lower border defect in the lower jaw occurs mainly in the older patient, in large advancements >10 mm, or if the entire lower border sticks to the proximal fragment during the split. The left side seems most affected. Two measures to avoid this defect are as follows: First, the split should allow the lingual part of the cortical lower border to remain with the lingual bone plate, which has the additional advantage that the nerve stays away from the proximal fragment during the split. We also advise a modified approach to the lower border. With a round 4-mm drill, the lower border is addressed until the first bleeding point is seen, without removing the lingual part of the lower border. To avoid a bad split, an initiation of the split must be made, done with piezosurgical bone cutting instruments after the anterior vertical cut is made. To gain access and a correct direction of the instruments, the anterior part of the vertical osteotomy needs to be beveled. - The need for blood transfusion in orthognathic surgery is low both in monomaxillary and regular bimaxillary surgery when strict transfusion criteria are followed and when additional surgery is avoided. Neither duration of the surgery nor perioperative blood loss seems to correlate well with the practice of blood transfusion. The preoperative hemoglobin level, general health status of the patient, and age need to be taken into consideration. In young, healthy patients without comorbidities, there is no need for crossmatch of blood for routine single-jaw or double-jaw surgery, unless additional procedures or complex upper jaw surgery is contemplated. - A chin osteotomy with an oscillating saw carries a small risk of bleeding in the floor of the mouth with subsequent airway problems; the inner border of the chin osteotomy should be carried out with a piezosurgical unit to avoid damage to blood vessels and soft tissues in the floor of the mouth. - BSSOs and Le Fort I osteotomies have no surgical effect on the airway unless an episode of perioperative uncontrolled excessive bleeding is encountered. - Life-threatening hemorrhage after Le Fort I osteotomies cannot be prevented and will occur with an incidence of
