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Superior repositioning of the maxilla combined with mandibular advancement: Mandibular RIF improves stability
Superior repositioning of the maxilla combined with mandibular advancement: Mandibular RIF improves stability Kai Forssell, DDS, Odont Dr, Timothy A. Turvey, DDS, Ceib Phillips, PhD, MPH, and William R. Proffit, DDS, PhD Turku, Fhdand, and Chapel Hill, N.C. Postsurgical changes in 24 patients who had rigid internal fixation (RIF) of the mandible with screws after combined superior repositioning of the maxilla and mandibular advancement were compared with 53 patients who underwent the same surgery but who had intraosseous wire fixation, skeletal suspension wires, and 8 weeks of maxillomandibular fixation (MMF). During the first 8 weeks after surgery, the mean posterior relapse of the mandible was greater in the MMF group than in the RIF group (for example, -1.1 mm versus 0.15 mm at B point), and the percentage of patients with clinically significant vertical and horizontal changes was greater in the MMF group. By 1 year, there had been slight additional mean relapse in the MMF group ( - 1.5 mm net relapse at B point, with 42% of the patients showing 2 mm or more relapse). In the RIF group, the mandible was more likely to be repositioned forward than posteriorly (net mean change at B point, 0.7 mm forward; 33% had 2 mm or more forward movement). In the RIF group, all but one of the patients (96%) were judged to have an excellent clinical result; in the MMF group, the corresponding figure was 60%. (AM J ORTHOO DENTOFACORTHOP 1992;102:342-50.)
S i m u l t a n e o u s superior repositioning of the maxilla and advancement of the mandible is commonly employed to correct excessive anterior face height (skeletal open bite) combined with mandibular deficiency. In these patients, mandibular surgery alone has a high potential for major relapse, whereas maxillary surgery alone corrects the open bite but not the mandibular deficiency, t Previous reports have shown that when conventional wire fixation and maxillomandibular fixation (MMF) are employed, although clinical results are generally satisfactory, stability after the combined osteotomies is not as good as with either of the procedures alone. 25 Improved stability has been reported for twojaw osteotomies when rigid internal fixation in both jaws replaced wire fixation and MMF68; Krekmanov et al. 9 reported similar results when rigid fixation with screws was used only in the mandible. Skoczylas and associates t~ compared short-term stability of wire and rigid fixation in two-jaw surgery and reported no significant differences between the two fixation groups.
From the Departments of Oral and Maxillofacial Surgery and Orthodontics, University of North Carolina School of Dentistry; This v, ork was supported in part by NIH grant DE-05215 from the National Institute of Dental Research and the North Carolina Dentofacial Study Group. It was carried out during the tenure of a Finland Research Fellowship for Dr. Kai Forssell. 811138526
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This article compares l-year postsurgical stability and clinical results in 77 patients undergoing superior repositioning of the maxilla and mandibular advancement at one institution. In 24 patients, rigid internal fixation (RIF) was used to stabilize the sagittal osteotomy and either wires or plates were used to stabilize the maxilla. This group was compared with a previously reported group of 53 patients who underwent an identical surgery but had osseous wires and maxillomandibular fixation (MMF). Because of the large sample size, the length of follow-up, and the consistency in the methods of analysis within and between groups, this report is unique.
MATERIAL AND METHODS From the University of North Carolina (UNC) database, 77 patients met these selection criteria: (1) combination of one-stage LeFort I downfracture osteotomy of the maxilla combined with bilateral sagittal split osteotomies of the mandible; (2) at least 2 mm superior movement of the maxillary incisors and/or molars, and at least 2 mm anterior movement of B point. There was no upper limit set in the criteria for any point. As previously reported, 2 mm is well beyond the method error'; (3) developmental problems only, i.e., no recognized syndromes or history of trauma as an etiologic agent; and (4) cephalometric films available immediately before surgery (after completion of preparatory orthodontic treatment), immediately after surgery (within 72 hours), and 1-year after surgery. Although not a criterion, an additional cephalometric
Volunle 102 Number 4 film taken at 8 weeks after surgery was available for 75 of the subjects (53 in one group and 22 in the other group). In 24 patients the sagittal osteotomies were fixed with screws (13 with positional screws; 11 with lag screws). In 13 of these 24 patients the maxillas were secured with wire fixation and skeletal suspension wires, whereas the remaining 11 had plate fixation (Fig. 1, A and B). For comparison, a previously rcported group of 53 patients meeting the above criteria but who had stabilization of the maxilla and mandible with intraosseous wire fixation, skeletal suspension wires and MMF during an 8-week period was used. 5 The cephalometric data for both groups were acquired and analyzed exactly as reported previously, 5 with the 140-point UNC digitization model and an x-y coordinate system to differentiate horizontal and vertical changes in the positions of selected landmarks (Fig. 2). All patients had interocclusal wafer splints in place when the immediate postoperative cephalometric radiograph was obtained, and all had them removed when the I-year radiograph was taken. The splint was still in place for all 53 of the wire group who had ccphalometric radiographs at 8 weeks after surgery, but in the rigid group, the splint had been removed previously in all but 9 of the 22 subjects who had an 8-week film. The two groups were very similar in their prctreatment demographics. Of the patients in both groups 88% were female. The mean age at surgery for the RIF group was 24 years (SD = 7 years) and 29 years (SD = 10 years) for the MMF group. The mean pretreatment mandibular plane angle was 44 ~ and 43 ~ and the mean gonial angle 130 ~ and 131 ~ for the RIF and MMF groups, respectively. Before treatment, the only noteworthy difference was the higher frequency of severe anterior open bite in the MMF group (59% versus 46% in the RIF group). A higher percentage of the MMF group had maxillary segmental osteotomics (43% versus 33%), whereas a higher proportion of the RIF group had concurrent genioplasties (54% versus 38%). At surgery, the mean vertical and horizontal movements of the maxilla and the mandible were virtually identical (Table I and I1). The surgical changes for both groups are illustrated in a composite tracing in (Fig. 3). The clinical results were judged at the patient's l-year follow-up visit. The result was classified as follows: Excellent if a Class I canine relationship was maintained with not more than 3 mm ovcrjet and no anterior open bite; satisfactory if the canine relationship was not worse than end-on and the overjet not more than 5 mm, and the bite remained closed; and poor if the canine relationship was Class II, ovcrjet was > 5 mm, or the bite opened anteriorly. For the cephalometric data, descriptive statistics by time interval were generated with SAS statistical package.12 Cephalometric changes for each time interval also were categorized by the extent of the absolute change: < 2 , 2 to 4, and > 4 mm or degrees. The method error for all skeletal landmarks ranged from 0.5 to 0.7 mm. A 2 mm or greater change in landmarks was viewed as clinically significant and outside the random error inherent in the method. Percentages by category are reported in consideration of this "critical clinical value."
Mandibular RIF inlproves stability
343
\
"lb r ~I,~Y';,~ . "'
I
.
A
\
B Fig. 1. A, Diagrammatic representation of fixation with mandibular RIF and wire fixation in maxilla. B, Fixation with bone plates in the maxilla and screws in the mandible.
A repeated measures analysis of variance was used to assess the effect of type of fixation, the effect of time, and the interaction between time and type of fixation for each of the x and y coordinate measures. Paired t tests were used to assess the short-term changes within each group. The level of significance was set at 0.01 because of the number of comparisons performed. At this significance level, the sample sizes in this study are adequate to detect mean differences between the fixation groups of 2 mm with 70% power.if the pooled standard deviations are less than 2.65 mm. The row mean score test was used to compare the clinical outcomes between the fixation groups.
344
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Am. J. Orthod. Dentofac. Orthop. October 1992
Superior Repositioning of the Maxilla With Mandibular Advancement P r e - S u r g e r y to I m m e d i a t e P o s t - o p
6*
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CO
ANS PNS
Go q
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Fig. 2. Changes in x-y coordinate positions of 12 cephalometric landmarks were analyzed by using horizontal line through sella rotated 6 ~ downward from sella-nasion line anteriorly as horizontal reference axis and perpendicular vertical line through sella as vertical reference axis.
RESULTS
Mean postsurgical changes in cephalometric landmark positions for the two groups are illustrated in composite tracings in Figs. 4 and 5, and tabulated data for horizontal and vertical changes in landmark positions are shown in Tables I and II. During the first 8 weeks after surgery, there was less posterior relapse of mandibular landmarks in the RIF group than in the MMF group, with a statistically significant difference at pogonion and menton. For example, in the RIF group 23% of the patients had more than 2 mm change at B point, and the change was as likely to be anteriorly as posteriorly; in the MMF group, 44% had changes of this magnitude and the movement was predominantly posteriorly (Fig. 6). The patients in the RIF group also had, on the average, better short-term vertical stability (Fig. 7). In both groups, gonion tended to move superiorly, but the change was greater with the MMF group (mean change, - 2 . 5 4 mm) than with the RIF group ( - 1 . 6 1 mm). The result was a significantly larger increase in the mandibular plane angle with MMF. Two-thirds of the MMF group had more than 2 ~ increase in thr'rfianciibular plane angle, and 30% had more than a 4 ~ increase.
- --.........
Pre-Surgery I m m e d Post-op - Rigid Fixation (24 patients) I m m e d Post-op - Wire Fixation (53 patients)
Fig. 3. Composite cephalometric tracings showing mean changes for MMF and RIF groups from before to immediately after surgery.
When the splint is removed, the mandible rotates upward and forward somewhat, the amount depending on splint thickness. It should be kept in mind in evaluating short-term mandibular changes that when the 8-week radiograph was taken, the splint had been removed for most of the patients in the RIF group but for none of the MMF group. Changes in the position of the maxilla from surgery to 1 year were small and similar in both groups (Fig. 5). However, there were differences in the mandibular changes (Table I and 11). With MMF, there was a tendency toward continued posterior movement of anterior mandibular landmarks: 42% of the group had 2 mm or more net mandibular relapse at B point (Fig. 6), and the net mean movement was - 1.5 mm. In contrast, a relapse of 2 mm or more at B point occurred in only two patients (8%) in the RIF group, and the net mean change was 0.7 mm anteriorly. Gonion moved superiorly in both groups (Fig. 5), but the changes were greater in the MMF group, and the mandibular plane
Vo/ume 102
Mandibular RIF improves stability
Number 4
Superior Repositioning of the Maxilla With Mandibular Advancement Immediate Post-op to 8 Weeks Post-op
Immed Post-op 8 Weeks Post-op - Rigid Fixation (g patients) 8 Weeks Post-op - Wire Fixation (53 patients)
345
Superior Repositioning of the Maxilla With Mandibular Advancement Immediate Post-op to One Year Post-op
IO .......
lmmed Post-op 1 Year Post-op - Rigid Fixation (24 patients) 1 Year Post-op - Wire Fixation (53 patients)
Fig. 4. Composite cephalometric tracings showing mean changes for MMF and RIF groups from immediately after surgery to 8 weeks.
Fig. 5. Composite cephalometric tracings showing mean changes for MMF and RIF groups from immediately after surgery to 1 year.
angle increased greater than 3 ~ in that group, whereas it increased less than 1~ in the RIF group. As "Fable III illustrates, there was a significant (p = 0.005) difference in clinical outcomes. The outcome was judged excellent in all but one of the R1F patients but in only 60% of the MMF patients. Ten of the I I MMF patients with a poor result had severe anterior open bite before treatment, and the "poor" classification in each of these cases was due to some return to open bite. The one patient with a poor result after RIF had the mandibular fixation screws removed 6 weeks after surgery because of infection and never completed postsurgical orthodontic treatment.
come back down between 6 weeks and 1 year. '3 The result is excellent long-term stability, with over 90% of the patients having no relapse. With mandibular advancement alone and wire fixation, there is a tendency for the mandible to move posteriorly during fixation, but then to come forward again between 6 weeks and 1 year, after fixation is released, ~ so that much of the short-term "relapse" change is recovered. In the short-term, when the two surgical procedures are done simultaneously and wire fixation is used, the changes are similar but not identical to a combination of the changes when the two procedures are done separately. With mandibular surgery alone, there is a tendency for the mandible to slip posteriorly and rotate in a way that increases the mandibular plane; two-jaw surgery accentuates the rotation and with it the loss of c h i n projection. 5 In the long-term, the major difference between the patients with wire fixation and two-jaw versus one-jaw
DISCUSSION Wire fixation. It has been noted previously that with isolated superior repositioning of the maxilla and wire fixation, the maxilla tends to move slightly more superiorly during the first postsurgical weeks, but then to
Forssell et al.
346
Am. J. Orthml. Dentr Orthop. October 1992
Table I. H o r i z o n t a l c h a n g e s Presurgery to posts trgery Wire firation Landmark or angle
Meat1
A point ANS angle PNS angle Maxillary incisor Maxillary molar B point Pogonion Menton Gonion Condylar Mandibular incisor Mandibular molar
1.39 0.43 1.29 i .32 2.37 8.53 12.53 12.85 4.65 - 1.01 7.37 7.27
I
Postsurger3' to 8 weeks
Rigid firation SO
Mea,,
1.94 2.55 2.60 2.81 2.58 3.36 5.25 5.26 3.441 2.281 3.24 3.23
1.44 0.68 1.20 ! .61 2.64 7.33 12.82 13.40 1.84 0.19 5.88 5.29
]
Wire fixation Mean
SD 1.40 2.25 1.94* 1.90* 2.08* 2.82* 4.50" 4.41 * 3.37* 1.29 2.45" 3.26*
]
- 0.43 -0.44 O. 19 - 0.53 0.14 - ! .09 - 2.14 - 2.46 0.73 0.58 - 0.46 - 0.05
Rigid firation SD
Mean
1.28 1.56 1.67 1.69 1.94 2.06 2.08r 2.41 t 2.82 2.05 1.63 1.84
I
0.10 0.05 0.09 - 0.20 -0.29 0.15 - 0.39 - 0.55 - 0.24 -0.16 0.16 0.59
SD 0.98 0.98 0.76 1.35 1.38 1.69 i .8 i 2.18 2.13 2.07 1.32 1.63
Values in millimeters or degrees. ttorizontal changes: + = anterior movement. - = posterior movement. *Significant (P < 0.01) change within group. tSignificant (P < 0.01) difference between groups.
Table II. V e r t i c a l a n d a n g u l a r c h a n g e s Presurget T to postsurgery Wire fLtation Landmark or angle A point ANS angle PNS angle Maxillary incisor Maxillary molar B point Pogonion Menton Gonion Condylar Mandibular incisor Mandibular molar Mandibular plane Gonial angle
Mean -3.00 - 3.62 - 2.07 - 3.84 - 3.31 -0.39 - 1.79 - 0.63 0.40 0.81 - i .47 - 0.76 - 4.51 2.32
Postsurgery to 8 weeks
Rigid firation
Wire f&ation
SD
Mean
SD
2.65 2.64 2.19 2.82 1.88t 3.39 3.69 3.07 2.58 2.36 3.12 1.951 3.76 6.031
-2.28 - 2.15 - 1.48 - 2.66 - 2.15 0.20 - 0.87 0.48 0.96 0.25 - 0. ! 8 1.20 - 5.31 - 3.14
2.47* 2.34* 2.31 * 2.16" 1.52* 2.39 2.89* 1.8 I 2.70 1.22 1.98 ! .84 3.18* 4.69
Mean - 0.29 -0.10
l
Rigid J't~ation SD
Mean
-0.68 -0.92 -0.28 0.23 -0.27 -2.54 -0.57 -0.38
1.65 1.46 1.16 1.56 1.09 2.52 2.00 1.52 2.54 2.11 1.48
-0.54 -0.38 -0.84 - 1.39 -0.93 - 1.61 -0.55 - 1.00
-
1.02
1.49
-
2.80 3.47
1.85t 4.13t
- 0.93
- 0.33 -0.29 - 0.73
l
SD 1.84 0.88 0.86 1.130 1.41 ! .92 2.52 1.35 2.14 i.36 ! .50
1.65
1.68
0.50 0.50
!.36 2.32
Values in millimeters or degrees. Vertical changes: + = inferior movement, - = superior movement. *Significant (P < 0.01) change within group. tSignificant (P < 0.01) difference between groups.
s u r g e r y is t h a t t h e r e c o v e r y o f s h o r t - t e r m c h a n g e s t h a t occur with the isolated surgical procedures occur when they are combined. dency
does not
I n s t e a d , t h e r e is a t e n -
f o r a d d i t i o n a l r e l a p s e a f t e r initial h e a l i n g h a s
It m u s t b e k e p t in m i n d t h a t t h e p a t i e n t s u n d e r g o i n g two-jaw surgery have different mandibular
and facial
structures than those receiving isolated mandibular advancement.
In the two-j~w
patients, the mandibular
o c c u r r e d . T h e m a n d i b l e t e n d s to s l i p f u r t h e F p b ~ f e r i o r l y ,
plane decreases
and the bite may open because of continuing mandibular rotation?
other factors beyond the addition of maxillary surgery
r a t h e r t h a n i n c r e a s e s at s u r g e r y , a n d
the amount of advancement
u s u a l l y is l a r g e r . T h e s e a n d
Volume 102 Number 4
Mandibidar RIF improves stability
Postsurgery to 1 year Rigid firation
Wire f&ation SD
Mean
1.52 1.94 1.87 1.85 2.45 2.72t 3.45"[" 3.37 3.17 2.06 2.20t 2.90
-0.84 - 1.05 0.18 -I.10 0.02 -
1.50
-2.76 - 2.54
0.45 0.72 -
1.25
-0.16
Mean
(
-0.56 -0.96 -0.73 -0.36 - 0.06 0.66 - 0.40 -0.40 1.02 - 0.2 ! 0.49 0.60
SD 1.34" 1.43* 1.35 1.71" 1.92 2.61 3.30 3.82 3.45 1.51 2.34 2.43
Postsurgery to 1 )'ear Wire fixation Mean
I
so
SD
Mean
0.23 0.74 -0.51 -0.01 -0.48 - 1.47 - 0.51 - 1.06 -4.05 - 1.03
2.03 1.46 1.26 1.58 1.28 2.41 3.29 2.09 2.73 2.10
O. 13 -0.30 -0.16 --0.25 -0.17 -2.45 - 0.65 - ! .92 -2.25 -0.56
-
1.92
- 2.24
1.67*
1.79 2.72t 4.62
-2.65 0.68 2.22
2.67 3.51"
1.72
-2.17 3.22 3.49
[
Rigid fL~ation
2.01 1.94
i.16 1.40
1.31 2.00* 2.78 1.45*
3.42* 1.90"
1.63"
may contribute to the different pattern of postsurgical change. Rigid fixation. For superior repositioning of the maxilla alone, the effect of replacing wire fixation of the maxilla with bone-plate fixation has not been well documented. There is no reason to expect a major difference from the excellent stability obtained with wire
347
fixation, nor have we observed any differences clinically. When bone screws are used for isolated mandibular advancement, there are major differences from wire fixation in the first postsurgical weeks, 14"15but by lyear after surgery the recovery shown by wire fixation patients has made the minor differences in relapse no longer significant. 16 A previous study indicates that the type of screws used and the technique of placement (position versus lag) is not a factor influencing the stability of mandibular advancement. 17 In addition, there were no differences noted either cephalometrically or clinically between these two subgroups in this study. Previous workers have suggested, 7"9and this article confirms, that with two-jaw surgery and mandibular RIF, there is better short- and long-term stability than was observed with wire fixation. Both the tendency for the mandible to relapse posteriorly and for the maxilla to rotate up posteriorly are largely eliminated. The improved stability presumably is related to the greater ability of bone screws to withstand muscle pull and/or forces from stretched soft tissues, but this may not be the whole story. It is possible that differences in technique because of the use of RIF, as opposed to the effect of the fixation itself, can contribute to the better clinical results. At least two differences in the techniques of RIF as opposed to wire fixation could be important. First, when the maxilla is moved superiorly and the mandible is advanced, it is critically important to place the condyles correctly in their fossae before fixation is applied. If the condyles are distracted medially and inferiorly immediately after surgery, the mandible is much more likely to relapse posteriorly than if the condyles are seated. Each of the 77 patients studied had preoperative and postoperative panoramic radiographs with the teeth in occlusion obtained with the same equipment. For the 53 MMF patients, these radiographs were scrutinized and compared with the presurgery radiograph for condyle-fossa relationships. In those patients (2) where condyles were judged to be down or out of the fossa, immediate reoperation was undertaken. For the 24 RIF patients, similar radiographs were obtained but none required reoperation. The use of screws for fixation allows the surgeon the opportunity of removing MMF during surgery to check the condylar position. This is not possible when wire fixation of the mandible is employed. Thus, better control of condylar position at surgery associated with RIF would be expected to produce better stability and better clinical results. Second, the jaws are immobilized for an extended period with wire fixation, whereas limited function resumes in a few days at most with rigid fixation. Early jaw mobilization favors early resolution of edema, ap-
348
Forssell et al.
Am. J. Orthod. Dentofac. Orthop. October 1992
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Fig. 6. Bar graph shewing percentage of patients in MMF and RIF groups who demonstrated horizontal changes greater than 2 mm.
Table
III. Clinical outcomes I
Wire fixation Rigid fixation
Excellent 32 (60%) 23 (96%)
]
Good 10 (19%) 0
[.
Poor 11 (21%) 1 (4%)
pears to facilitate healing, and contributes to a general feeling of well-being for patients. To some extent, the improved clinical results also may be related to early function.
The UNC experience with these two-jaw surgery patients indicates, as Krekmanov9 suggested, that the improved stability is largely due to the use of mandibular RIF. Whether this occurs because it allows the surgeon to check condylar position at surgery, or because the screws better maintain the condyle-fossa relationship better during the healing phase, is not known. In the present series, all the patients had screws in the mandible, but half also had bone plates on the maxilla. The others had intraosseous wiring of the maxilla. Our sample is still not large enough to detect small differences that might exist between the groups with and
Vot,,me 102
Mandibular RIF hnproves stability
Number 4
Patients Demonstrating
Change
Immed Postop to 8 Weeks Postop
Immed Postop to I Year Postop
% 70
i!
S
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349
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Group [ ]
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Group [ ]
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Fig. 7. Bar graph showing percentage of patients in MMF and RIF groups who demonstrated vertical changes greater than 2 mm.
without bone plates for the maxilla, but we have noted no o b v i o u s clinical differences. T h e results o f two-jaw surgery appear greatly improved with only m a n d i b u l a r RIF. In this series of 77 patients u n d e r g o i n g superior repositioning o f the maxilla and m a n d i b u l a r advancement, no differences in stability or clinical results were identified b e t w e e n those patients u n d e r g o i n g single piece or multiple piece maxillary surgery. Similarly, genioplasty was also not significant. The presurgical presence o f an open bite and its high association with posttreatment failure has b e e n previously reported in the 53 M M F patients, s This same association for the R I F group was not made. Previous reports have shown that success rates reflecting clinical criteria in excess o f 90% are possible for m a n d i b u l a r a d v a n c e m e n t alone and superior repositioning of the maxilla alone. The present data indicate, that with m a n d i b u l a r RIF, similar success c a n : b e attained for the c o m b i n a t i o n o f these procedures. We thank Debora Price for technical assistance.
REFERENCES
1. Proffit WR. Treatment planning: the search for wisdom. In: Proffit WR, White RP Jr., eds. Surgical-orthodontic treatment. St. Louis: CV Mosby, 1990: pg. 142-91. 2. Brammer J, Finn R, Bell WH, Sinn D, Reisch J, Dana K. Stability after bimaxillary surgery to correct vertical maxillary excess and mandibular deficiency. J Oral Surg 1980;38:664-70. 3. LaBanc JP, Turvey TA, Epker BN. Results following simultaneous mobilization of the maxilla and mandible for the correction of dentofacial deformities: analysis of 100 consecutive patients. Oral Surg Oral Med Oral Pathol 1982;54:607-12. 4. Bell WH. Vertical maxillary excess and mandibular deficiency. In: Bell WH, ed. Surgical correction of dentofacial deformities. New concepts. Vol III. Philadelphia: WB Saunders, 1985: pg. 86-107. 5. Turvey TA, Phillips C, Zaytoun HS, Proffit WR. Simultaneous superior repositioning of the maxilla and mandibular advancement. A report on stability. AM J ORTtIODDENTOFACORTHOP 1988;94:372-83. 6. Hennes JA, Wallen TR, Bloomquist DS, Crouch DL. Stability of simultaneous mobilization of the maxilla and mandible utilizing internal rigid fixation, lnt J Adult Orthod Orthogn Surg 1988;3:127-41. 7. Satrom KD, Sinclair PM, Wolford LM. The stability of double jaw surgery: a comparison of rigid versus wire fixation. A.',l J ORmoo DLwrornc OR'mOP 1991;99:550-63.
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Am. J. Orthod. Dentofac. Orthop. October 1992
Forssell et al.
8. Law JH, Rotskoff KS, Smith RJ. Stability following combined maxillary and mandibular osteotomies treated with rigid internal fixation. J Oral Maxillofac Surg 1989;47:128-36. 9. Krekmanov L, Lilja J, Ringqvist M. Simultaneous correction of maxillary and mandibular dentofacial deformities without the use of postoperative intermaxillary fixation. A clinical and cephalometric study. Int J Oral Maxillofac Surg 1988;17:363-70. 10. Skoczylas LJ, Ellis E I!I, FonsecaRJ, Gallo WJ. Stability of simultaneous maxillary intrusion and mandibular advancement: a comparison of rigid and non-rigid fixation techniques. J Oral Maxillofac Surg 1988;46:1056-64. 11. Phillips C, Turvey TA, McMillian A. Surgical orthodontic correction of mandibular deficiency by sagittal osteotomy: clinical and cephalometric analysis of 1 year data. A,',t J ORTtIOD DENTOFACORT|IOP 1989;96:501-6. 12. SAS Institute Inc. SAS user's guide: statistics. Version 5 ed. Cary, North Carolina: SAS Institute Inc. 1985. 13. Proffit WR, Phillips C, Turvey TA. Stability following superior repositioning of the maxilla by LeFort 1 osteotomy. A,',iJ OR'I-IIOD DEN'rOFACORTttOP 1987;92:15 !-61. 14. Thomas Phi, Tucker MR, Prewitt JR, Proffit WR. Early skeletal
and dental changes following mandibular advancement and rigid internal fixation. Int J Adult Ortbod Orthogn Surg 1986;3: 171-8. 15. van Sickles JE, Larsen AJ, Thrash WJ. Relapse after rigid fixation of mandibular advancement. J Oral Maxillofac Surg 1986;44:698-702. 16. Watzke IM, Turvey TA, Phillips C, Proffit WR. Stability of mandibular advancement by sagittal osteotomy with screw and wire fixation: a comparative study. J Oral Maxillofac Surg 1990;48:108-21. 17. Watzke IM, Tucker MR, Turvey TA. Lag screw versus position screw techniques for rigid internal fixation of sagittal osteotomies: a comparison of stability. Int J Adult Orthod Orthogn Surg 1991;6:19-27. Reprh~t requests to:
Dr. Timothy Turvey Department of Oral and Maxillofacial Surgery School of Dentistry, CB# 7450, Brauer Hall University of North Carolina Chapel Hill, NC 27599-7450
AAO MEETING CALENDAR
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S i m u l t a n e o u s superior repositioning of the maxilla and advancement of the mandible is commonly employed to correct excessive anterior face height (skeletal open bite) combined with mandibular deficiency. In these patients, mandibular surgery alone has a high potential for major relapse, whereas maxillary surgery alone corrects the open bite but not the mandibular deficiency, t Previous reports have shown that when conventional wire fixation and maxillomandibular fixation (MMF) are employed, although clinical results are generally satisfactory, stability after the combined osteotomies is not as good as with either of the procedures alone. 25 Improved stability has been reported for twojaw osteotomies when rigid internal fixation in both jaws replaced wire fixation and MMF68; Krekmanov et al. 9 reported similar results when rigid fixation with screws was used only in the mandible. Skoczylas and associates t~ compared short-term stability of wire and rigid fixation in two-jaw surgery and reported no significant differences between the two fixation groups.
From the Departments of Oral and Maxillofacial Surgery and Orthodontics, University of North Carolina School of Dentistry; This v, ork was supported in part by NIH grant DE-05215 from the National Institute of Dental Research and the North Carolina Dentofacial Study Group. It was carried out during the tenure of a Finland Research Fellowship for Dr. Kai Forssell. 811138526
342
This article compares l-year postsurgical stability and clinical results in 77 patients undergoing superior repositioning of the maxilla and mandibular advancement at one institution. In 24 patients, rigid internal fixation (RIF) was used to stabilize the sagittal osteotomy and either wires or plates were used to stabilize the maxilla. This group was compared with a previously reported group of 53 patients who underwent an identical surgery but had osseous wires and maxillomandibular fixation (MMF). Because of the large sample size, the length of follow-up, and the consistency in the methods of analysis within and between groups, this report is unique.
MATERIAL AND METHODS From the University of North Carolina (UNC) database, 77 patients met these selection criteria: (1) combination of one-stage LeFort I downfracture osteotomy of the maxilla combined with bilateral sagittal split osteotomies of the mandible; (2) at least 2 mm superior movement of the maxillary incisors and/or molars, and at least 2 mm anterior movement of B point. There was no upper limit set in the criteria for any point. As previously reported, 2 mm is well beyond the method error'; (3) developmental problems only, i.e., no recognized syndromes or history of trauma as an etiologic agent; and (4) cephalometric films available immediately before surgery (after completion of preparatory orthodontic treatment), immediately after surgery (within 72 hours), and 1-year after surgery. Although not a criterion, an additional cephalometric
Volunle 102 Number 4 film taken at 8 weeks after surgery was available for 75 of the subjects (53 in one group and 22 in the other group). In 24 patients the sagittal osteotomies were fixed with screws (13 with positional screws; 11 with lag screws). In 13 of these 24 patients the maxillas were secured with wire fixation and skeletal suspension wires, whereas the remaining 11 had plate fixation (Fig. 1, A and B). For comparison, a previously rcported group of 53 patients meeting the above criteria but who had stabilization of the maxilla and mandible with intraosseous wire fixation, skeletal suspension wires and MMF during an 8-week period was used. 5 The cephalometric data for both groups were acquired and analyzed exactly as reported previously, 5 with the 140-point UNC digitization model and an x-y coordinate system to differentiate horizontal and vertical changes in the positions of selected landmarks (Fig. 2). All patients had interocclusal wafer splints in place when the immediate postoperative cephalometric radiograph was obtained, and all had them removed when the I-year radiograph was taken. The splint was still in place for all 53 of the wire group who had ccphalometric radiographs at 8 weeks after surgery, but in the rigid group, the splint had been removed previously in all but 9 of the 22 subjects who had an 8-week film. The two groups were very similar in their prctreatment demographics. Of the patients in both groups 88% were female. The mean age at surgery for the RIF group was 24 years (SD = 7 years) and 29 years (SD = 10 years) for the MMF group. The mean pretreatment mandibular plane angle was 44 ~ and 43 ~ and the mean gonial angle 130 ~ and 131 ~ for the RIF and MMF groups, respectively. Before treatment, the only noteworthy difference was the higher frequency of severe anterior open bite in the MMF group (59% versus 46% in the RIF group). A higher percentage of the MMF group had maxillary segmental osteotomics (43% versus 33%), whereas a higher proportion of the RIF group had concurrent genioplasties (54% versus 38%). At surgery, the mean vertical and horizontal movements of the maxilla and the mandible were virtually identical (Table I and I1). The surgical changes for both groups are illustrated in a composite tracing in (Fig. 3). The clinical results were judged at the patient's l-year follow-up visit. The result was classified as follows: Excellent if a Class I canine relationship was maintained with not more than 3 mm ovcrjet and no anterior open bite; satisfactory if the canine relationship was not worse than end-on and the overjet not more than 5 mm, and the bite remained closed; and poor if the canine relationship was Class II, ovcrjet was > 5 mm, or the bite opened anteriorly. For the cephalometric data, descriptive statistics by time interval were generated with SAS statistical package.12 Cephalometric changes for each time interval also were categorized by the extent of the absolute change: < 2 , 2 to 4, and > 4 mm or degrees. The method error for all skeletal landmarks ranged from 0.5 to 0.7 mm. A 2 mm or greater change in landmarks was viewed as clinically significant and outside the random error inherent in the method. Percentages by category are reported in consideration of this "critical clinical value."
Mandibular RIF inlproves stability
343
\
"lb r ~I,~Y';,~ . "'
I
.
A
\
B Fig. 1. A, Diagrammatic representation of fixation with mandibular RIF and wire fixation in maxilla. B, Fixation with bone plates in the maxilla and screws in the mandible.
A repeated measures analysis of variance was used to assess the effect of type of fixation, the effect of time, and the interaction between time and type of fixation for each of the x and y coordinate measures. Paired t tests were used to assess the short-term changes within each group. The level of significance was set at 0.01 because of the number of comparisons performed. At this significance level, the sample sizes in this study are adequate to detect mean differences between the fixation groups of 2 mm with 70% power.if the pooled standard deviations are less than 2.65 mm. The row mean score test was used to compare the clinical outcomes between the fixation groups.
344
Forssell et a/.
Am. J. Orthod. Dentofac. Orthop. October 1992
Superior Repositioning of the Maxilla With Mandibular Advancement P r e - S u r g e r y to I m m e d i a t e P o s t - o p
6*
L
CO
ANS PNS
Go q
Me
Fig. 2. Changes in x-y coordinate positions of 12 cephalometric landmarks were analyzed by using horizontal line through sella rotated 6 ~ downward from sella-nasion line anteriorly as horizontal reference axis and perpendicular vertical line through sella as vertical reference axis.
RESULTS
Mean postsurgical changes in cephalometric landmark positions for the two groups are illustrated in composite tracings in Figs. 4 and 5, and tabulated data for horizontal and vertical changes in landmark positions are shown in Tables I and II. During the first 8 weeks after surgery, there was less posterior relapse of mandibular landmarks in the RIF group than in the MMF group, with a statistically significant difference at pogonion and menton. For example, in the RIF group 23% of the patients had more than 2 mm change at B point, and the change was as likely to be anteriorly as posteriorly; in the MMF group, 44% had changes of this magnitude and the movement was predominantly posteriorly (Fig. 6). The patients in the RIF group also had, on the average, better short-term vertical stability (Fig. 7). In both groups, gonion tended to move superiorly, but the change was greater with the MMF group (mean change, - 2 . 5 4 mm) than with the RIF group ( - 1 . 6 1 mm). The result was a significantly larger increase in the mandibular plane angle with MMF. Two-thirds of the MMF group had more than 2 ~ increase in thr'rfianciibular plane angle, and 30% had more than a 4 ~ increase.
- --.........
Pre-Surgery I m m e d Post-op - Rigid Fixation (24 patients) I m m e d Post-op - Wire Fixation (53 patients)
Fig. 3. Composite cephalometric tracings showing mean changes for MMF and RIF groups from before to immediately after surgery.
When the splint is removed, the mandible rotates upward and forward somewhat, the amount depending on splint thickness. It should be kept in mind in evaluating short-term mandibular changes that when the 8-week radiograph was taken, the splint had been removed for most of the patients in the RIF group but for none of the MMF group. Changes in the position of the maxilla from surgery to 1 year were small and similar in both groups (Fig. 5). However, there were differences in the mandibular changes (Table I and 11). With MMF, there was a tendency toward continued posterior movement of anterior mandibular landmarks: 42% of the group had 2 mm or more net mandibular relapse at B point (Fig. 6), and the net mean movement was - 1.5 mm. In contrast, a relapse of 2 mm or more at B point occurred in only two patients (8%) in the RIF group, and the net mean change was 0.7 mm anteriorly. Gonion moved superiorly in both groups (Fig. 5), but the changes were greater in the MMF group, and the mandibular plane
Vo/ume 102
Mandibular RIF improves stability
Number 4
Superior Repositioning of the Maxilla With Mandibular Advancement Immediate Post-op to 8 Weeks Post-op
Immed Post-op 8 Weeks Post-op - Rigid Fixation (g patients) 8 Weeks Post-op - Wire Fixation (53 patients)
345
Superior Repositioning of the Maxilla With Mandibular Advancement Immediate Post-op to One Year Post-op
IO .......
lmmed Post-op 1 Year Post-op - Rigid Fixation (24 patients) 1 Year Post-op - Wire Fixation (53 patients)
Fig. 4. Composite cephalometric tracings showing mean changes for MMF and RIF groups from immediately after surgery to 8 weeks.
Fig. 5. Composite cephalometric tracings showing mean changes for MMF and RIF groups from immediately after surgery to 1 year.
angle increased greater than 3 ~ in that group, whereas it increased less than 1~ in the RIF group. As "Fable III illustrates, there was a significant (p = 0.005) difference in clinical outcomes. The outcome was judged excellent in all but one of the R1F patients but in only 60% of the MMF patients. Ten of the I I MMF patients with a poor result had severe anterior open bite before treatment, and the "poor" classification in each of these cases was due to some return to open bite. The one patient with a poor result after RIF had the mandibular fixation screws removed 6 weeks after surgery because of infection and never completed postsurgical orthodontic treatment.
come back down between 6 weeks and 1 year. '3 The result is excellent long-term stability, with over 90% of the patients having no relapse. With mandibular advancement alone and wire fixation, there is a tendency for the mandible to move posteriorly during fixation, but then to come forward again between 6 weeks and 1 year, after fixation is released, ~ so that much of the short-term "relapse" change is recovered. In the short-term, when the two surgical procedures are done simultaneously and wire fixation is used, the changes are similar but not identical to a combination of the changes when the two procedures are done separately. With mandibular surgery alone, there is a tendency for the mandible to slip posteriorly and rotate in a way that increases the mandibular plane; two-jaw surgery accentuates the rotation and with it the loss of c h i n projection. 5 In the long-term, the major difference between the patients with wire fixation and two-jaw versus one-jaw
DISCUSSION Wire fixation. It has been noted previously that with isolated superior repositioning of the maxilla and wire fixation, the maxilla tends to move slightly more superiorly during the first postsurgical weeks, but then to
Forssell et al.
346
Am. J. Orthml. Dentr Orthop. October 1992
Table I. H o r i z o n t a l c h a n g e s Presurgery to posts trgery Wire firation Landmark or angle
Meat1
A point ANS angle PNS angle Maxillary incisor Maxillary molar B point Pogonion Menton Gonion Condylar Mandibular incisor Mandibular molar
1.39 0.43 1.29 i .32 2.37 8.53 12.53 12.85 4.65 - 1.01 7.37 7.27
I
Postsurger3' to 8 weeks
Rigid firation SO
Mea,,
1.94 2.55 2.60 2.81 2.58 3.36 5.25 5.26 3.441 2.281 3.24 3.23
1.44 0.68 1.20 ! .61 2.64 7.33 12.82 13.40 1.84 0.19 5.88 5.29
]
Wire fixation Mean
SD 1.40 2.25 1.94* 1.90* 2.08* 2.82* 4.50" 4.41 * 3.37* 1.29 2.45" 3.26*
]
- 0.43 -0.44 O. 19 - 0.53 0.14 - ! .09 - 2.14 - 2.46 0.73 0.58 - 0.46 - 0.05
Rigid firation SD
Mean
1.28 1.56 1.67 1.69 1.94 2.06 2.08r 2.41 t 2.82 2.05 1.63 1.84
I
0.10 0.05 0.09 - 0.20 -0.29 0.15 - 0.39 - 0.55 - 0.24 -0.16 0.16 0.59
SD 0.98 0.98 0.76 1.35 1.38 1.69 i .8 i 2.18 2.13 2.07 1.32 1.63
Values in millimeters or degrees. ttorizontal changes: + = anterior movement. - = posterior movement. *Significant (P < 0.01) change within group. tSignificant (P < 0.01) difference between groups.
Table II. V e r t i c a l a n d a n g u l a r c h a n g e s Presurget T to postsurgery Wire fLtation Landmark or angle A point ANS angle PNS angle Maxillary incisor Maxillary molar B point Pogonion Menton Gonion Condylar Mandibular incisor Mandibular molar Mandibular plane Gonial angle
Mean -3.00 - 3.62 - 2.07 - 3.84 - 3.31 -0.39 - 1.79 - 0.63 0.40 0.81 - i .47 - 0.76 - 4.51 2.32
Postsurgery to 8 weeks
Rigid firation
Wire f&ation
SD
Mean
SD
2.65 2.64 2.19 2.82 1.88t 3.39 3.69 3.07 2.58 2.36 3.12 1.951 3.76 6.031
-2.28 - 2.15 - 1.48 - 2.66 - 2.15 0.20 - 0.87 0.48 0.96 0.25 - 0. ! 8 1.20 - 5.31 - 3.14
2.47* 2.34* 2.31 * 2.16" 1.52* 2.39 2.89* 1.8 I 2.70 1.22 1.98 ! .84 3.18* 4.69
Mean - 0.29 -0.10
l
Rigid J't~ation SD
Mean
-0.68 -0.92 -0.28 0.23 -0.27 -2.54 -0.57 -0.38
1.65 1.46 1.16 1.56 1.09 2.52 2.00 1.52 2.54 2.11 1.48
-0.54 -0.38 -0.84 - 1.39 -0.93 - 1.61 -0.55 - 1.00
-
1.02
1.49
-
2.80 3.47
1.85t 4.13t
- 0.93
- 0.33 -0.29 - 0.73
l
SD 1.84 0.88 0.86 1.130 1.41 ! .92 2.52 1.35 2.14 i.36 ! .50
1.65
1.68
0.50 0.50
!.36 2.32
Values in millimeters or degrees. Vertical changes: + = inferior movement, - = superior movement. *Significant (P < 0.01) change within group. tSignificant (P < 0.01) difference between groups.
s u r g e r y is t h a t t h e r e c o v e r y o f s h o r t - t e r m c h a n g e s t h a t occur with the isolated surgical procedures occur when they are combined. dency
does not
I n s t e a d , t h e r e is a t e n -
f o r a d d i t i o n a l r e l a p s e a f t e r initial h e a l i n g h a s
It m u s t b e k e p t in m i n d t h a t t h e p a t i e n t s u n d e r g o i n g two-jaw surgery have different mandibular
and facial
structures than those receiving isolated mandibular advancement.
In the two-j~w
patients, the mandibular
o c c u r r e d . T h e m a n d i b l e t e n d s to s l i p f u r t h e F p b ~ f e r i o r l y ,
plane decreases
and the bite may open because of continuing mandibular rotation?
other factors beyond the addition of maxillary surgery
r a t h e r t h a n i n c r e a s e s at s u r g e r y , a n d
the amount of advancement
u s u a l l y is l a r g e r . T h e s e a n d
Volume 102 Number 4
Mandibidar RIF improves stability
Postsurgery to 1 year Rigid firation
Wire f&ation SD
Mean
1.52 1.94 1.87 1.85 2.45 2.72t 3.45"[" 3.37 3.17 2.06 2.20t 2.90
-0.84 - 1.05 0.18 -I.10 0.02 -
1.50
-2.76 - 2.54
0.45 0.72 -
1.25
-0.16
Mean
(
-0.56 -0.96 -0.73 -0.36 - 0.06 0.66 - 0.40 -0.40 1.02 - 0.2 ! 0.49 0.60
SD 1.34" 1.43* 1.35 1.71" 1.92 2.61 3.30 3.82 3.45 1.51 2.34 2.43
Postsurgery to 1 )'ear Wire fixation Mean
I
so
SD
Mean
0.23 0.74 -0.51 -0.01 -0.48 - 1.47 - 0.51 - 1.06 -4.05 - 1.03
2.03 1.46 1.26 1.58 1.28 2.41 3.29 2.09 2.73 2.10
O. 13 -0.30 -0.16 --0.25 -0.17 -2.45 - 0.65 - ! .92 -2.25 -0.56
-
1.92
- 2.24
1.67*
1.79 2.72t 4.62
-2.65 0.68 2.22
2.67 3.51"
1.72
-2.17 3.22 3.49
[
Rigid fL~ation
2.01 1.94
i.16 1.40
1.31 2.00* 2.78 1.45*
3.42* 1.90"
1.63"
may contribute to the different pattern of postsurgical change. Rigid fixation. For superior repositioning of the maxilla alone, the effect of replacing wire fixation of the maxilla with bone-plate fixation has not been well documented. There is no reason to expect a major difference from the excellent stability obtained with wire
347
fixation, nor have we observed any differences clinically. When bone screws are used for isolated mandibular advancement, there are major differences from wire fixation in the first postsurgical weeks, 14"15but by lyear after surgery the recovery shown by wire fixation patients has made the minor differences in relapse no longer significant. 16 A previous study indicates that the type of screws used and the technique of placement (position versus lag) is not a factor influencing the stability of mandibular advancement. 17 In addition, there were no differences noted either cephalometrically or clinically between these two subgroups in this study. Previous workers have suggested, 7"9and this article confirms, that with two-jaw surgery and mandibular RIF, there is better short- and long-term stability than was observed with wire fixation. Both the tendency for the mandible to relapse posteriorly and for the maxilla to rotate up posteriorly are largely eliminated. The improved stability presumably is related to the greater ability of bone screws to withstand muscle pull and/or forces from stretched soft tissues, but this may not be the whole story. It is possible that differences in technique because of the use of RIF, as opposed to the effect of the fixation itself, can contribute to the better clinical results. At least two differences in the techniques of RIF as opposed to wire fixation could be important. First, when the maxilla is moved superiorly and the mandible is advanced, it is critically important to place the condyles correctly in their fossae before fixation is applied. If the condyles are distracted medially and inferiorly immediately after surgery, the mandible is much more likely to relapse posteriorly than if the condyles are seated. Each of the 77 patients studied had preoperative and postoperative panoramic radiographs with the teeth in occlusion obtained with the same equipment. For the 53 MMF patients, these radiographs were scrutinized and compared with the presurgery radiograph for condyle-fossa relationships. In those patients (2) where condyles were judged to be down or out of the fossa, immediate reoperation was undertaken. For the 24 RIF patients, similar radiographs were obtained but none required reoperation. The use of screws for fixation allows the surgeon the opportunity of removing MMF during surgery to check the condylar position. This is not possible when wire fixation of the mandible is employed. Thus, better control of condylar position at surgery associated with RIF would be expected to produce better stability and better clinical results. Second, the jaws are immobilized for an extended period with wire fixation, whereas limited function resumes in a few days at most with rigid fixation. Early jaw mobilization favors early resolution of edema, ap-
348
Forssell et al.
Am. J. Orthod. Dentofac. Orthop. October 1992
Go Mdl B
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MxM
to 8 Weeks
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,
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I
,
,
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i
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Post = POsteriorMovement Ant = AnteriorMovement
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Fig. 6. Bar graph shewing percentage of patients in MMF and RIF groups who demonstrated horizontal changes greater than 2 mm.
Table
III. Clinical outcomes I
Wire fixation Rigid fixation
Excellent 32 (60%) 23 (96%)
]
Good 10 (19%) 0
[.
Poor 11 (21%) 1 (4%)
pears to facilitate healing, and contributes to a general feeling of well-being for patients. To some extent, the improved clinical results also may be related to early function.
The UNC experience with these two-jaw surgery patients indicates, as Krekmanov9 suggested, that the improved stability is largely due to the use of mandibular RIF. Whether this occurs because it allows the surgeon to check condylar position at surgery, or because the screws better maintain the condyle-fossa relationship better during the healing phase, is not known. In the present series, all the patients had screws in the mandible, but half also had bone plates on the maxilla. The others had intraosseous wiring of the maxilla. Our sample is still not large enough to detect small differences that might exist between the groups with and
Vot,,me 102
Mandibular RIF hnproves stability
Number 4
Patients Demonstrating
Change
Immed Postop to 8 Weeks Postop
Immed Postop to I Year Postop
% 70
i!
S
,0 1
,o
-
40
7O
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Go
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S = Superior Movement I = Interior MoVement
349
B
MxM
Mxl
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A
%
i
I A
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Mxl
MxM
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Go
MdPI
MdRF [ ]
2 - 4 mm or degrees
MdWF [ ]
2 - 4 mm or degrees
Group [ ]
> 4 mm or degrees
Group [ ]
> 4 mm or degrees
Fig. 7. Bar graph showing percentage of patients in MMF and RIF groups who demonstrated vertical changes greater than 2 mm.
without bone plates for the maxilla, but we have noted no o b v i o u s clinical differences. T h e results o f two-jaw surgery appear greatly improved with only m a n d i b u l a r RIF. In this series of 77 patients u n d e r g o i n g superior repositioning o f the maxilla and m a n d i b u l a r advancement, no differences in stability or clinical results were identified b e t w e e n those patients u n d e r g o i n g single piece or multiple piece maxillary surgery. Similarly, genioplasty was also not significant. The presurgical presence o f an open bite and its high association with posttreatment failure has b e e n previously reported in the 53 M M F patients, s This same association for the R I F group was not made. Previous reports have shown that success rates reflecting clinical criteria in excess o f 90% are possible for m a n d i b u l a r a d v a n c e m e n t alone and superior repositioning of the maxilla alone. The present data indicate, that with m a n d i b u l a r RIF, similar success c a n : b e attained for the c o m b i n a t i o n o f these procedures. We thank Debora Price for technical assistance.
REFERENCES
1. Proffit WR. Treatment planning: the search for wisdom. In: Proffit WR, White RP Jr., eds. Surgical-orthodontic treatment. St. Louis: CV Mosby, 1990: pg. 142-91. 2. Brammer J, Finn R, Bell WH, Sinn D, Reisch J, Dana K. Stability after bimaxillary surgery to correct vertical maxillary excess and mandibular deficiency. J Oral Surg 1980;38:664-70. 3. LaBanc JP, Turvey TA, Epker BN. Results following simultaneous mobilization of the maxilla and mandible for the correction of dentofacial deformities: analysis of 100 consecutive patients. Oral Surg Oral Med Oral Pathol 1982;54:607-12. 4. Bell WH. Vertical maxillary excess and mandibular deficiency. In: Bell WH, ed. Surgical correction of dentofacial deformities. New concepts. Vol III. Philadelphia: WB Saunders, 1985: pg. 86-107. 5. Turvey TA, Phillips C, Zaytoun HS, Proffit WR. Simultaneous superior repositioning of the maxilla and mandibular advancement. A report on stability. AM J ORTtIODDENTOFACORTHOP 1988;94:372-83. 6. Hennes JA, Wallen TR, Bloomquist DS, Crouch DL. Stability of simultaneous mobilization of the maxilla and mandible utilizing internal rigid fixation, lnt J Adult Orthod Orthogn Surg 1988;3:127-41. 7. Satrom KD, Sinclair PM, Wolford LM. The stability of double jaw surgery: a comparison of rigid versus wire fixation. A.',l J ORmoo DLwrornc OR'mOP 1991;99:550-63.
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Am. J. Orthod. Dentofac. Orthop. October 1992
Forssell et al.
8. Law JH, Rotskoff KS, Smith RJ. Stability following combined maxillary and mandibular osteotomies treated with rigid internal fixation. J Oral Maxillofac Surg 1989;47:128-36. 9. Krekmanov L, Lilja J, Ringqvist M. Simultaneous correction of maxillary and mandibular dentofacial deformities without the use of postoperative intermaxillary fixation. A clinical and cephalometric study. Int J Oral Maxillofac Surg 1988;17:363-70. 10. Skoczylas LJ, Ellis E I!I, FonsecaRJ, Gallo WJ. Stability of simultaneous maxillary intrusion and mandibular advancement: a comparison of rigid and non-rigid fixation techniques. J Oral Maxillofac Surg 1988;46:1056-64. 11. Phillips C, Turvey TA, McMillian A. Surgical orthodontic correction of mandibular deficiency by sagittal osteotomy: clinical and cephalometric analysis of 1 year data. A,',t J ORTtIOD DENTOFACORT|IOP 1989;96:501-6. 12. SAS Institute Inc. SAS user's guide: statistics. Version 5 ed. Cary, North Carolina: SAS Institute Inc. 1985. 13. Proffit WR, Phillips C, Turvey TA. Stability following superior repositioning of the maxilla by LeFort 1 osteotomy. A,',iJ OR'I-IIOD DEN'rOFACORTttOP 1987;92:15 !-61. 14. Thomas Phi, Tucker MR, Prewitt JR, Proffit WR. Early skeletal
and dental changes following mandibular advancement and rigid internal fixation. Int J Adult Ortbod Orthogn Surg 1986;3: 171-8. 15. van Sickles JE, Larsen AJ, Thrash WJ. Relapse after rigid fixation of mandibular advancement. J Oral Maxillofac Surg 1986;44:698-702. 16. Watzke IM, Turvey TA, Phillips C, Proffit WR. Stability of mandibular advancement by sagittal osteotomy with screw and wire fixation: a comparative study. J Oral Maxillofac Surg 1990;48:108-21. 17. Watzke IM, Tucker MR, Turvey TA. Lag screw versus position screw techniques for rigid internal fixation of sagittal osteotomies: a comparison of stability. Int J Adult Orthod Orthogn Surg 1991;6:19-27. Reprh~t requests to:
Dr. Timothy Turvey Department of Oral and Maxillofacial Surgery School of Dentistry, CB# 7450, Brauer Hall University of North Carolina Chapel Hill, NC 27599-7450
AAO MEETING CALENDAR
1993--Toronto, Canada, May 15 to 19, Metropolitan Toronto Convention Center 1994--Orlando, Fla., May 1 to 4, Orange County Convention and Civic Center 1995--San Francisco, Calif., May 7 to 10, Moscone Convention Center (International Orthodontic Congress) 1996--Denver, Colo., May 12 to 16, Colorado Convention Center 1997mPhiladelphia, Pa., Ma.y 3t.o 7, Philadelphia Convention Center 1998mDallas, Texas, May 16 to 20, Dallas Convention Center 1999--San Diego, Calif., May 15 to 19, San Diego Convention Center