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The surgical treatment of skeletal anterior open-bite deformities with rigid internal fixation in the mandible
The surgical treatment of skeletal anterior open-bite deformities with-rigid internal fixation in the mandible Monty Reitzik, MB, ChB, BDS, FDSRCS (Eng.),* Philip G. Barer, DMD, MSD,** W. Michael Wainwright, BDS, DDS, MS,** and Bernard Lim*** Vancouver, British Columbia, Canada
The rationale for the surgical correction of skeletal anterior open-bite deformities by bilateral mandibular rotation osteotomy is presented. Results of this procedure in which rigid internal fixation is used are reported and show a very high degree of long-term stability. The procedure offers a useful alternative to the more common approach of posterior maxillary intrusion, which does not always address the cosmetic defect. (AMJ ORTHOODENTOFACORTHOP1990;97:52-7.)
T h e successful treatment of anterior openbite deformities represents perhaps one of the most challenging aspects of orthognathic surgery. Apertognathia may exist with Angle Class I, Class II, and Class III occlusal relationships, and its manifestations are protean. The lips may be competent or incompetent at rest, and the mandible may be grossly prognathic or retrognathic) The site of origin of the deformity has been stressed as the key to treatment planning, and Frost et al. 2 stress the importance of appreciating the individual nature of each patient. There appears to be considerable agreement that once puberty has been reached, the prognosis with orthodontic treatment alone is poor) Orthodontic treatment is usually directed at either stunting the growth of the maxilla with high-pull headgear directed to the posterior maxilla or retarding the growth of the mandible with chin cups. Attempts to intrude the teeth in occlusion and extrude those in open bite give very poor esthetic results and lead to relapse. 46 Habit-control techniques in the prepubescent patient are probably unnecessary, since this type of simple open bite often closes spontaneously. 6 Skeletal open bites require surgical intervention for a stable and esthetically pleasing result. It would seem axiomatic that if the site of abnormality is corrected, then a harmonious and functional result should be obtained. It is important, therefore, to examine the ceph-
From the Faculty of Dentistry, University of British Columbia. *Division of Oral and Maxillofacial Surgery. **Division of Orthodontics. ***Dental student.
811110-456 52
alometric anatomy to determine the cause of the apertognathia. In an excellent review of the literature, Ellis et al. 7 found no consensus with regard to the spatial position of the palatalplane in relation to the cranial base. Accordingly, it is not surprising that they found no significant.differences between open-bite and non-openbite eases in their series. They also reported that sophisticated studies, which had separated the occlusat plane into maxillary and mandibular components, had reported no significant differences in the maxillary ocelusal plane between non-open-bite and open-bite cases. They further suggest that the apertognathia arises below the maxillary dentition, although they reported that the upper molars were about 3 mm lower in their open-bite series. Inasmuch as the upper incisors are not usually displaced in the vertical plane, this does suggest some overgrowth of the posterior maxillary alveolus, at least in some cases. There seems to be universal agreement among most investigators7 that the posterior face height is shorter in apertognathia and the gonial angle is significantly greater. Ellis et al. 7 found that the increased mandibular plane angle ( + 8 . 3 °) was due mainly to an increased gonial angle ( + 5 . 4 °) in conjunction with clockwise rotation of the mandible (+2.9°). There was a concomitant 1.2 mm shortening of the posterior facial height. It is not clear whether this clockwise rotation of the mandible is the cause or the effect of the posterior maxillary alveolar hypertrophy. The consensus among most oral surgeons is that in Class II cases either the posterior maxilla alone or the entire maxilla should be surgically intruded to obtain a good occlusion, t'~ It is thought that the secondary an-
Volume 97 Number 1
ticiockwise autorotation of the mandible that is achieved will produce sufficient profile improvement to be esthetically acceptable. If micrognathia or microgenia is very marked, then a genioplasty should be performed tO complete profile harmony.~ Orthognathic procedures in the ascending ramus of the mandible are frowned On since they are thought to have a very high relapse potential. 8.9 If we accept the dictum that surgical correction of a deformity should return the skeletal reiation to normal to improve function and facial esthetics, 2 and if we further note that many skeletal open-bite deformities are characterized by a decreased posterior face height and a short mandibular ramus with a steep gonial angle, ~°,jt then it must follow that the operation of choice in these cases should be an osteotomy in the ascending ramus. This will lengthen the ramus, correct the gonial angle, and rotate the body of the mandible in an anticlockwise direction to correct occlusion. This approach has attracted scant attention because of its high relapse potential. However, the use of rigid internal fixation to overcome relapse makes this a p proach possible and, indeed, the operation of choice in those cases in which it is indicated. We have advocated the use of rigid .internal fixation for mandibular advancement osteotomies. These procedures have been shown to be extremely stable in patients without anterior apertognathia/2"~4 One of us (M.R.) has also recently reported a new technique for mandibular reduction osteotomies for patients with mandibular prognathism~5in which rigid internal fixation has resulted in complete interfragmentary stability. Skeletal anterior open bites are treated with maxillary surgery alone, mandibular surgery alone, or a combination of the two. This article reports the longterm results in those patients who had mandibular surgery an d is part of a larger study that was undertaken to measure the long-term stability as well as the incidence of complications, such as lip dysesthesia, paresis, hemorrhage, infection, postoperative joint symptoms, scar acceptance, etc. This article reports on the interfragmentary stability as measured by a longitudinal cephalometric analysis. The other parameters measured will be reported elsewhere, ~6 but in summary the correction of 100 cases of mandibular retrusion with or without anterior open bite, by the same operatioa reported in this article, was surveyed by an independent observer. A very low incidence (6%) of permanent mental paresthesia was found. In all cases, the area of paresthesia was small, and the severity was categorized as very mild. Scar acceptance by the patient and the observer was rated between good and excellent. Post-
Surgical treatment of anterior open-bite deformities 53 Operative hemorrhage or infection was not seen throughout th.e series. Patients were asked whether they would have preferred a cadaver bone graft in place o f the autograft they received and, without exception, they preferred the aut~raft. No long-term complications from the graft donor dites were reported, apart from a stump neuroma within the scar in one patient. Forty patients in this series had some manifestations of temporomandibular joint pain dysfunction syndrome at the initial preopei'ative visit, and 65% of these patients were cured of their symptoms by the end of treatment. In two cases (of 100), temp0romandibular joint pain was experienced for .the first time after the operation. It is often stated that patients in North America would find the external approach unacceptable, especially in view of the addition of a bone graft. That has not been out~experience. All the patients in this series were given the option o f the internal approach with its inevitably higher incidence and severity of permanent lip paresthesi a of approximately.50%. ~7"Is Although some patients chose to have a sagittal split procedure, for Obvious reasons they are not included in this series. Only those who chose the external approach are reported. THE OPERATION
All patients in this series were operated on during the course of orthodontic treatment. The ascending ramus was approached ihrough a modified Risdon incision in a skin crease below the angle of the mandible. After division of the platysma and the masSeter muscle just above the lower border of the mandible, the masseter was stripped off the ascending ramus and a reverse-L cutwas made with a reciprocating saw (Fig. 1). The distal fragment of the mandible was moved forward and-rotated in an anticlockwise d]rection,'so that a predetermined occlusion of the teeth cotild be fixed by means of an interocclusal wafer and maxillomandibular fixation. Once this had.been achieved, the proximal fragments were rigidly fixed to the distal fragment with Howmedica mandibular mesh and 8 mm Luhr screws. The proximal fragments were maintained in the same position postoperatively as they were in preoperatively to ensure that the position, angulatlon, and rotation of the condyles remained unchanged. This step is important if dysfunctional joint syndromes are to be avoided. There should be no contact between the two proximal fragments and the distal fragrhent. This is important to ensure that the condyles can be placed in a physiologically neutral position at operation. The gaps between the proximal and distal fragments may be grafted with homografts, heterografts, or allo-
54
Reitzik et al.
Am. ,I. Orthod. Dentofac. Orthop. January 1990
\
,~'-,~-..
" ~:"A'~
Fig. 1. The operation.
A
z~
r -r2
T2 - T3
SNA
-0.8 °
-0.4 °
SNB
+4.0 °
-0.4 °
SNMP
-4.7 °
+0.6 °
Angle measured
Gon
-9.0 °
+0.3 °
-2.0 °
+1.0 °
-1.0 °
-0.7 °
Fig. 2. The first column represents the mean changes attributable to the operation. The second column indicates long-term stability or instability•
grafts, according to the surgeon's preference. We used iliac crest bone taken from the inner surface only. This procedure adds less than 15 minutes to the length of the whole operation, is almost totally free of compli-
cations, '6 and, in our opinion, provides die best graft available. The wound was then closed in layers in the usual manner. A vacuum drain may be used for the first 12 to 24 hours to counteract any tendency to hematoma formation, but is not essential. Maxillomandibular fixation was removed at the end of the operation, and the patient was iransferred to the postanesthetic recovery room without fixation. This greatly simplifies the immediate postoperative nursing management. METHODS AND MATERIALS
The sample consisted of 20 consecutively treated patients who required mandibular advancement osteotomy together with anticlockwise rotation of the distal fragment and who had been Operated on more than 12 months before this study was undeiaaken. In 16 cases, complete records were available. Four cases were discarded because of incomplete radiographic records, but they were clinically stable. None of the cases in this series showed any tendency to clinical relapse, and in all cases incisal contact has been maintained for up to 8 years. Cases in which there was a negative vertical overbite of the incisor teeth together with a positive overjet were classified as Class II anterior open bites. Cephalometric radiographs were taken on the same machine before operation (TI), 3 days after the operation (T2), and a m~nimum of 12 months (range, 12 to 86 months) later (T3). The angles measured were SNA (sella, nasion, A
Volume 97 Number I
Surgical treatment of anterior open-bite deformities 55 30-
GONIAL ANGLE CHANGE
.= .,.j (/)
o
20
• []
Mean Closure 9 Degrees
Closure Net Closure
o 0 f/J Q)
P
10
Q 0 3
8
1
9
6
16
7
Case
14
No.
5
2
4
13 15 12 11 10
Fig. 3. Changes recorded in the gonial angles of each case.
.,~ 20
I
MANDIBULARPLANE (TO SN) CHANGE Mean Surgical Closure 4.3 Degrees
/
o
Mean Relapse 0•6 Degrees
o t0"4
•
L
III
Closure
0 3
8
1
9
6
16
7
14
Case No.
5
2
4
13 15 12 11 10
Fig. 4. Changes recorded in the SNMP angle in each case.
point), SNB (sella, nasion, B point), SNMP (sella, nasion, mandibular plane), gonial angle, SN (axial inclination of upper incisor to sella nasion), and MP (lower incisor axial inclination to mandibular plane)• Templating was used to verify accurate reproduction of point gonion in all tracings. This was made possible by the presence of the rigid internal fixation mesh, which acted as a bone marker.
RESULTS The mean changes in the 16 cases studied are summarized in Fig. 2. Mean changes are perhaps the only way of comparing the results of one operation with those of another or, alternatively, the same operation in different centers. Relapse due to interfragmentary instability is indicated primarily by an increase or opening of the gonial angle. ~'~5 Confirmation can usually be obtained by observation of an increase in the SNMP angle. In this series, the mean long-term opening of the gonial angle was 0.3 °, an insignificant amount when compared with the mean increase in the gonial angle that can be expected when rigid internal fixation is not used or when rigid internal fixation fails and the gonial
angle opens by about 10°. ~s As the gonial angle was closed by 90 by the operation, the relapse of 0.3 ° represents a loss of about 3.3% of the closure gained surgically. The SNMP angle opened 0.6 ° postoperatively. Detailed study of individual cases is often tedious and unrewarding but can sometimes provide useful information. Figs. 3 and 4 represent individual results. In nine cases, the gonial angle closed in the postoperative period or remained stable. In a further four cases, '2'5 although the gonial angle opened slightly, this change was accompanied by stability or closure of the SNMP angle, thus excluding even cephalometric relapse. Only two cases exhibited significant opening of both angles (cases 4 and 5) in spite of the fact that they remained clinically stable (Fig. 5). Examination of the changes in SNA angle and the incisor axial inclination angles revealed little of interest but they are included for completeness.
DISCUSSION Dattilo et al. 19 reported the results of surgical correction of open-bite deformities by reverse-L 0ste-
56
Reitzik el al.
Am. J. Orthod. Dentofiw. Orthop. Jattltary 1990
Fig. 5. Preoperative and postoperative profile and occlusal changes in case 5, which actually recorded the greatest amount of cephalometric relapse in spite of remaining clinically stable for 6 years.
otomies of the ascending ramus. They state: "Due to the previous failure of the sagittal ramus split osteotomy to successfully treat this deformity, mandibular ramus procedures have all but been abandoned in favor of maxillary procedures." They reported a mean relapse of 11.4% in the treatment of Class II cases by a surgical technique that was very similar to the operation reported in this article, with one significant exception. T h e y relied on 8 weeks of maxillomandibular fixation to effect bony healing and did not use rigid internal fixation. Therefore it would have been highly instructive to compare the two series to evaluate the effect of rigid intemal fixation as the only variable. Unfortunately, they reported only one parameter of measurement, the X and Y coordinate position of pogonion. This point is inherently noisy because such variables as autorotation of the mandible during .postoperative orthodontic recovery or condylar sag at release of fixation cannot be taken into account. Thus the reported relapse rates of these two series cannot be compared directly. Similarly, Frost et al.-" reported a 25% relapse of the SNMP angle in a series of 13 cases. Only four
patients had ascending ramus osteotomies, and two of these were setbacks. In addition, all patients had maxillary osteotomies; thus comparison was rendered impossible. This highlights the difficulty of a literature search to gainfully compare surgical techniques. It is our contention that the only parameters of measurement that reveal the total picture of mandibular position in space as well as the relationship of the surgical fragments to each other are those discussed in this article and others that report operations for treatment of unmixed deformities 121~ that separate out early (surgical) relapse from long-term relapse due to interfragmentary instability. It must be remembered, however, that the gonial angle is sometimes difficult to find and reproduce accurately in a longitudinal series of films. The presence of a radiopaque bone marker (such as the rigid internal fixation device) greatly enhances the accuracy of this parameter. In summary, it would appear that the key to interfragmentary stability in all ascending ramus procedures is rigid internal fixation. The preoperative incisor vertical relationship makes little if any difference to the end result. A mandibular ascending ramus procedure
Volume 97 Number 1
can be safely used for correction of skeletal open bite if esthetic considerations indicate that it is the operation of choice. REFERENCES 1. Epker BN, Fish LC. Surgical orthodontic corrections of openbite deformity. AM J ORI"tIOD 1977;71:278-99. 2. Frost DE, Fonseca RJ, Turvey TA, Hall DJ. Cephalometrie diagnosis and surgical-orthodontic correction of apertognathia. At*,! J ORTHOD 1980;78:657-69. 3. Gile RA. A longitudinal cephalometric evaluation of orthodontically treated anterior open bite cases [Master's thesis]. Seattle, Washington: University of Washington, 1973. 4. Schendel SA, Eisenfeld JH, Bell WH, Epker BN, Miselevich DJ. The long face syndrome: vertical maxillary surgery. A~.l J ORrriOD 1976;70:398-408. 5. Wolford LM, Epker BN. The combined anterior and posterior maxillary ostectomy: a new technique. J Oral Surg 1975;33:84251. 6. Worms FW, Meskin LH, Isaacson RJ. Open bite. AM J OR'moo 1971 ;59:589-95. 7. Ellis E, McNamara JR, Lawrence TM. Components of adult Class II open-bite malocclusion. J Oral Maxillofac Surg 1985;43:92-105. 8. McNeil WR, Hooley JR, Sundberg RI. Skeletal relapse during intermaxillary fixation. J Oral Surg 1973;31:212-27. 9. Poulton DR, Ware WH. Surgical-orthodontic treatment of severe mandibular retrusion. A~,l J ORTHOD 1971;59:244-65. 10. Subtelny JD, Sakuda M. Open bite: diagnosis and treatment. AM J OR'I-HOD1964;50:337-58. 11. Nahoum HI, Horowitz SL, Benedicto EA. Vertical proportions: a guide for prognosis and treatment in anterior open bite. AM J ORTHOD 1977;72:128-46.
Surgical treatment of anterior open-bite deformities
57
12. Reitzik M. Mandibular advancement surgery: stability following a modified fixation technique. J Oral Surg 1980;38:893-7. 13. Reitzik M, Lowe A, Schmidt E. Stability following mandibular advancement using rigid internal fixation, lnt J Oral Surg 1981;10:276-80. 14. Barer PG, Wallen TR, McNeill RW, Reitzik M. Stability of mandibular advancement osteotomy using rigid internal fixation. AM J OR'HtOD DEt,/'rOF,~COR'mOP 1987;92:403-1 I. 15. Reitzik M. The surgical correction of mandibular prognathism using rigid internal fixation--a report of a new technique together with its long term stability. Ann R Coil Surg Engl 1988;70:380-5. 16. Reitzik M, Lim B. Complications following the surgical correction of micrognathia using rigid internal fixation [in press]. 17. Pepersack WJ, Chausse JM. Long term follow up of the sagittal splitting technique for correction of mandibular prognathism. J Maxillofac Surg 1978;6:117-40. 18. Kiyak HA, Hohl T, Sherrick P, West RA, McNeill RW, Bucher F. Sex differences in motives for and outcomes of orthognathic surgery. J Oral Surg 1981;39:757-64. 19. Dattilo DJ, Braun TW, Sotereanos GC. The inverted L osteotomy for treatment of skeletal open-bite deformities. J Oral Maxillofac Surg 1985;43:440-3.
Reprint requests to: Dr. Monty Reitzik Division of Oral and Maxillofacial Surgery Faculty of Dentistry University of British Columbia 2199 Wesbrook Mall Vancouver, B.C., Canada V6T IZ7
The rationale for the surgical correction of skeletal anterior open-bite deformities by bilateral mandibular rotation osteotomy is presented. Results of this procedure in which rigid internal fixation is used are reported and show a very high degree of long-term stability. The procedure offers a useful alternative to the more common approach of posterior maxillary intrusion, which does not always address the cosmetic defect. (AMJ ORTHOODENTOFACORTHOP1990;97:52-7.)
T h e successful treatment of anterior openbite deformities represents perhaps one of the most challenging aspects of orthognathic surgery. Apertognathia may exist with Angle Class I, Class II, and Class III occlusal relationships, and its manifestations are protean. The lips may be competent or incompetent at rest, and the mandible may be grossly prognathic or retrognathic) The site of origin of the deformity has been stressed as the key to treatment planning, and Frost et al. 2 stress the importance of appreciating the individual nature of each patient. There appears to be considerable agreement that once puberty has been reached, the prognosis with orthodontic treatment alone is poor) Orthodontic treatment is usually directed at either stunting the growth of the maxilla with high-pull headgear directed to the posterior maxilla or retarding the growth of the mandible with chin cups. Attempts to intrude the teeth in occlusion and extrude those in open bite give very poor esthetic results and lead to relapse. 46 Habit-control techniques in the prepubescent patient are probably unnecessary, since this type of simple open bite often closes spontaneously. 6 Skeletal open bites require surgical intervention for a stable and esthetically pleasing result. It would seem axiomatic that if the site of abnormality is corrected, then a harmonious and functional result should be obtained. It is important, therefore, to examine the ceph-
From the Faculty of Dentistry, University of British Columbia. *Division of Oral and Maxillofacial Surgery. **Division of Orthodontics. ***Dental student.
811110-456 52
alometric anatomy to determine the cause of the apertognathia. In an excellent review of the literature, Ellis et al. 7 found no consensus with regard to the spatial position of the palatalplane in relation to the cranial base. Accordingly, it is not surprising that they found no significant.differences between open-bite and non-openbite eases in their series. They also reported that sophisticated studies, which had separated the occlusat plane into maxillary and mandibular components, had reported no significant differences in the maxillary ocelusal plane between non-open-bite and open-bite cases. They further suggest that the apertognathia arises below the maxillary dentition, although they reported that the upper molars were about 3 mm lower in their open-bite series. Inasmuch as the upper incisors are not usually displaced in the vertical plane, this does suggest some overgrowth of the posterior maxillary alveolus, at least in some cases. There seems to be universal agreement among most investigators7 that the posterior face height is shorter in apertognathia and the gonial angle is significantly greater. Ellis et al. 7 found that the increased mandibular plane angle ( + 8 . 3 °) was due mainly to an increased gonial angle ( + 5 . 4 °) in conjunction with clockwise rotation of the mandible (+2.9°). There was a concomitant 1.2 mm shortening of the posterior facial height. It is not clear whether this clockwise rotation of the mandible is the cause or the effect of the posterior maxillary alveolar hypertrophy. The consensus among most oral surgeons is that in Class II cases either the posterior maxilla alone or the entire maxilla should be surgically intruded to obtain a good occlusion, t'~ It is thought that the secondary an-
Volume 97 Number 1
ticiockwise autorotation of the mandible that is achieved will produce sufficient profile improvement to be esthetically acceptable. If micrognathia or microgenia is very marked, then a genioplasty should be performed tO complete profile harmony.~ Orthognathic procedures in the ascending ramus of the mandible are frowned On since they are thought to have a very high relapse potential. 8.9 If we accept the dictum that surgical correction of a deformity should return the skeletal reiation to normal to improve function and facial esthetics, 2 and if we further note that many skeletal open-bite deformities are characterized by a decreased posterior face height and a short mandibular ramus with a steep gonial angle, ~°,jt then it must follow that the operation of choice in these cases should be an osteotomy in the ascending ramus. This will lengthen the ramus, correct the gonial angle, and rotate the body of the mandible in an anticlockwise direction to correct occlusion. This approach has attracted scant attention because of its high relapse potential. However, the use of rigid internal fixation to overcome relapse makes this a p proach possible and, indeed, the operation of choice in those cases in which it is indicated. We have advocated the use of rigid .internal fixation for mandibular advancement osteotomies. These procedures have been shown to be extremely stable in patients without anterior apertognathia/2"~4 One of us (M.R.) has also recently reported a new technique for mandibular reduction osteotomies for patients with mandibular prognathism~5in which rigid internal fixation has resulted in complete interfragmentary stability. Skeletal anterior open bites are treated with maxillary surgery alone, mandibular surgery alone, or a combination of the two. This article reports the longterm results in those patients who had mandibular surgery an d is part of a larger study that was undertaken to measure the long-term stability as well as the incidence of complications, such as lip dysesthesia, paresis, hemorrhage, infection, postoperative joint symptoms, scar acceptance, etc. This article reports on the interfragmentary stability as measured by a longitudinal cephalometric analysis. The other parameters measured will be reported elsewhere, ~6 but in summary the correction of 100 cases of mandibular retrusion with or without anterior open bite, by the same operatioa reported in this article, was surveyed by an independent observer. A very low incidence (6%) of permanent mental paresthesia was found. In all cases, the area of paresthesia was small, and the severity was categorized as very mild. Scar acceptance by the patient and the observer was rated between good and excellent. Post-
Surgical treatment of anterior open-bite deformities 53 Operative hemorrhage or infection was not seen throughout th.e series. Patients were asked whether they would have preferred a cadaver bone graft in place o f the autograft they received and, without exception, they preferred the aut~raft. No long-term complications from the graft donor dites were reported, apart from a stump neuroma within the scar in one patient. Forty patients in this series had some manifestations of temporomandibular joint pain dysfunction syndrome at the initial preopei'ative visit, and 65% of these patients were cured of their symptoms by the end of treatment. In two cases (of 100), temp0romandibular joint pain was experienced for .the first time after the operation. It is often stated that patients in North America would find the external approach unacceptable, especially in view of the addition of a bone graft. That has not been out~experience. All the patients in this series were given the option o f the internal approach with its inevitably higher incidence and severity of permanent lip paresthesi a of approximately.50%. ~7"Is Although some patients chose to have a sagittal split procedure, for Obvious reasons they are not included in this series. Only those who chose the external approach are reported. THE OPERATION
All patients in this series were operated on during the course of orthodontic treatment. The ascending ramus was approached ihrough a modified Risdon incision in a skin crease below the angle of the mandible. After division of the platysma and the masSeter muscle just above the lower border of the mandible, the masseter was stripped off the ascending ramus and a reverse-L cutwas made with a reciprocating saw (Fig. 1). The distal fragment of the mandible was moved forward and-rotated in an anticlockwise d]rection,'so that a predetermined occlusion of the teeth cotild be fixed by means of an interocclusal wafer and maxillomandibular fixation. Once this had.been achieved, the proximal fragments were rigidly fixed to the distal fragment with Howmedica mandibular mesh and 8 mm Luhr screws. The proximal fragments were maintained in the same position postoperatively as they were in preoperatively to ensure that the position, angulatlon, and rotation of the condyles remained unchanged. This step is important if dysfunctional joint syndromes are to be avoided. There should be no contact between the two proximal fragments and the distal fragrhent. This is important to ensure that the condyles can be placed in a physiologically neutral position at operation. The gaps between the proximal and distal fragments may be grafted with homografts, heterografts, or allo-
54
Reitzik et al.
Am. ,I. Orthod. Dentofac. Orthop. January 1990
\
,~'-,~-..
" ~:"A'~
Fig. 1. The operation.
A
z~
r -r2
T2 - T3
SNA
-0.8 °
-0.4 °
SNB
+4.0 °
-0.4 °
SNMP
-4.7 °
+0.6 °
Angle measured
Gon
-9.0 °
+0.3 °
-2.0 °
+1.0 °
-1.0 °
-0.7 °
Fig. 2. The first column represents the mean changes attributable to the operation. The second column indicates long-term stability or instability•
grafts, according to the surgeon's preference. We used iliac crest bone taken from the inner surface only. This procedure adds less than 15 minutes to the length of the whole operation, is almost totally free of compli-
cations, '6 and, in our opinion, provides die best graft available. The wound was then closed in layers in the usual manner. A vacuum drain may be used for the first 12 to 24 hours to counteract any tendency to hematoma formation, but is not essential. Maxillomandibular fixation was removed at the end of the operation, and the patient was iransferred to the postanesthetic recovery room without fixation. This greatly simplifies the immediate postoperative nursing management. METHODS AND MATERIALS
The sample consisted of 20 consecutively treated patients who required mandibular advancement osteotomy together with anticlockwise rotation of the distal fragment and who had been Operated on more than 12 months before this study was undeiaaken. In 16 cases, complete records were available. Four cases were discarded because of incomplete radiographic records, but they were clinically stable. None of the cases in this series showed any tendency to clinical relapse, and in all cases incisal contact has been maintained for up to 8 years. Cases in which there was a negative vertical overbite of the incisor teeth together with a positive overjet were classified as Class II anterior open bites. Cephalometric radiographs were taken on the same machine before operation (TI), 3 days after the operation (T2), and a m~nimum of 12 months (range, 12 to 86 months) later (T3). The angles measured were SNA (sella, nasion, A
Volume 97 Number I
Surgical treatment of anterior open-bite deformities 55 30-
GONIAL ANGLE CHANGE
.= .,.j (/)
o
20
• []
Mean Closure 9 Degrees
Closure Net Closure
o 0 f/J Q)
P
10
Q 0 3
8
1
9
6
16
7
Case
14
No.
5
2
4
13 15 12 11 10
Fig. 3. Changes recorded in the gonial angles of each case.
.,~ 20
I
MANDIBULARPLANE (TO SN) CHANGE Mean Surgical Closure 4.3 Degrees
/
o
Mean Relapse 0•6 Degrees
o t0"4
•
L
III
Closure
0 3
8
1
9
6
16
7
14
Case No.
5
2
4
13 15 12 11 10
Fig. 4. Changes recorded in the SNMP angle in each case.
point), SNB (sella, nasion, B point), SNMP (sella, nasion, mandibular plane), gonial angle, SN (axial inclination of upper incisor to sella nasion), and MP (lower incisor axial inclination to mandibular plane)• Templating was used to verify accurate reproduction of point gonion in all tracings. This was made possible by the presence of the rigid internal fixation mesh, which acted as a bone marker.
RESULTS The mean changes in the 16 cases studied are summarized in Fig. 2. Mean changes are perhaps the only way of comparing the results of one operation with those of another or, alternatively, the same operation in different centers. Relapse due to interfragmentary instability is indicated primarily by an increase or opening of the gonial angle. ~'~5 Confirmation can usually be obtained by observation of an increase in the SNMP angle. In this series, the mean long-term opening of the gonial angle was 0.3 °, an insignificant amount when compared with the mean increase in the gonial angle that can be expected when rigid internal fixation is not used or when rigid internal fixation fails and the gonial
angle opens by about 10°. ~s As the gonial angle was closed by 90 by the operation, the relapse of 0.3 ° represents a loss of about 3.3% of the closure gained surgically. The SNMP angle opened 0.6 ° postoperatively. Detailed study of individual cases is often tedious and unrewarding but can sometimes provide useful information. Figs. 3 and 4 represent individual results. In nine cases, the gonial angle closed in the postoperative period or remained stable. In a further four cases, '2'5 although the gonial angle opened slightly, this change was accompanied by stability or closure of the SNMP angle, thus excluding even cephalometric relapse. Only two cases exhibited significant opening of both angles (cases 4 and 5) in spite of the fact that they remained clinically stable (Fig. 5). Examination of the changes in SNA angle and the incisor axial inclination angles revealed little of interest but they are included for completeness.
DISCUSSION Dattilo et al. 19 reported the results of surgical correction of open-bite deformities by reverse-L 0ste-
56
Reitzik el al.
Am. J. Orthod. Dentofiw. Orthop. Jattltary 1990
Fig. 5. Preoperative and postoperative profile and occlusal changes in case 5, which actually recorded the greatest amount of cephalometric relapse in spite of remaining clinically stable for 6 years.
otomies of the ascending ramus. They state: "Due to the previous failure of the sagittal ramus split osteotomy to successfully treat this deformity, mandibular ramus procedures have all but been abandoned in favor of maxillary procedures." They reported a mean relapse of 11.4% in the treatment of Class II cases by a surgical technique that was very similar to the operation reported in this article, with one significant exception. T h e y relied on 8 weeks of maxillomandibular fixation to effect bony healing and did not use rigid internal fixation. Therefore it would have been highly instructive to compare the two series to evaluate the effect of rigid intemal fixation as the only variable. Unfortunately, they reported only one parameter of measurement, the X and Y coordinate position of pogonion. This point is inherently noisy because such variables as autorotation of the mandible during .postoperative orthodontic recovery or condylar sag at release of fixation cannot be taken into account. Thus the reported relapse rates of these two series cannot be compared directly. Similarly, Frost et al.-" reported a 25% relapse of the SNMP angle in a series of 13 cases. Only four
patients had ascending ramus osteotomies, and two of these were setbacks. In addition, all patients had maxillary osteotomies; thus comparison was rendered impossible. This highlights the difficulty of a literature search to gainfully compare surgical techniques. It is our contention that the only parameters of measurement that reveal the total picture of mandibular position in space as well as the relationship of the surgical fragments to each other are those discussed in this article and others that report operations for treatment of unmixed deformities 121~ that separate out early (surgical) relapse from long-term relapse due to interfragmentary instability. It must be remembered, however, that the gonial angle is sometimes difficult to find and reproduce accurately in a longitudinal series of films. The presence of a radiopaque bone marker (such as the rigid internal fixation device) greatly enhances the accuracy of this parameter. In summary, it would appear that the key to interfragmentary stability in all ascending ramus procedures is rigid internal fixation. The preoperative incisor vertical relationship makes little if any difference to the end result. A mandibular ascending ramus procedure
Volume 97 Number 1
can be safely used for correction of skeletal open bite if esthetic considerations indicate that it is the operation of choice. REFERENCES 1. Epker BN, Fish LC. Surgical orthodontic corrections of openbite deformity. AM J ORI"tIOD 1977;71:278-99. 2. Frost DE, Fonseca RJ, Turvey TA, Hall DJ. Cephalometrie diagnosis and surgical-orthodontic correction of apertognathia. At*,! J ORTHOD 1980;78:657-69. 3. Gile RA. A longitudinal cephalometric evaluation of orthodontically treated anterior open bite cases [Master's thesis]. Seattle, Washington: University of Washington, 1973. 4. Schendel SA, Eisenfeld JH, Bell WH, Epker BN, Miselevich DJ. The long face syndrome: vertical maxillary surgery. A~.l J ORrriOD 1976;70:398-408. 5. Wolford LM, Epker BN. The combined anterior and posterior maxillary ostectomy: a new technique. J Oral Surg 1975;33:84251. 6. Worms FW, Meskin LH, Isaacson RJ. Open bite. AM J OR'moo 1971 ;59:589-95. 7. Ellis E, McNamara JR, Lawrence TM. Components of adult Class II open-bite malocclusion. J Oral Maxillofac Surg 1985;43:92-105. 8. McNeil WR, Hooley JR, Sundberg RI. Skeletal relapse during intermaxillary fixation. J Oral Surg 1973;31:212-27. 9. Poulton DR, Ware WH. Surgical-orthodontic treatment of severe mandibular retrusion. A~,l J ORTHOD 1971;59:244-65. 10. Subtelny JD, Sakuda M. Open bite: diagnosis and treatment. AM J OR'I-HOD1964;50:337-58. 11. Nahoum HI, Horowitz SL, Benedicto EA. Vertical proportions: a guide for prognosis and treatment in anterior open bite. AM J ORTHOD 1977;72:128-46.
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12. Reitzik M. Mandibular advancement surgery: stability following a modified fixation technique. J Oral Surg 1980;38:893-7. 13. Reitzik M, Lowe A, Schmidt E. Stability following mandibular advancement using rigid internal fixation, lnt J Oral Surg 1981;10:276-80. 14. Barer PG, Wallen TR, McNeill RW, Reitzik M. Stability of mandibular advancement osteotomy using rigid internal fixation. AM J OR'HtOD DEt,/'rOF,~COR'mOP 1987;92:403-1 I. 15. Reitzik M. The surgical correction of mandibular prognathism using rigid internal fixation--a report of a new technique together with its long term stability. Ann R Coil Surg Engl 1988;70:380-5. 16. Reitzik M, Lim B. Complications following the surgical correction of micrognathia using rigid internal fixation [in press]. 17. Pepersack WJ, Chausse JM. Long term follow up of the sagittal splitting technique for correction of mandibular prognathism. J Maxillofac Surg 1978;6:117-40. 18. Kiyak HA, Hohl T, Sherrick P, West RA, McNeill RW, Bucher F. Sex differences in motives for and outcomes of orthognathic surgery. J Oral Surg 1981;39:757-64. 19. Dattilo DJ, Braun TW, Sotereanos GC. The inverted L osteotomy for treatment of skeletal open-bite deformities. J Oral Maxillofac Surg 1985;43:440-3.
Reprint requests to: Dr. Monty Reitzik Division of Oral and Maxillofacial Surgery Faculty of Dentistry University of British Columbia 2199 Wesbrook Mall Vancouver, B.C., Canada V6T IZ7