Aestheticand reconstructivesurgery
Long-term stability after inferior maxillary repositioning by miniplate fixation
D a v i d L. B a k e r 1, P a u l J. W. S t o e l i n g a 2, Peter A. Blijdorp 2, J o h n J, A. B r o u n s 2 1Department of Oral and Maxillofacial Surgery, University of Washington, Seattle, WA, USA (presently in private practice), and 2Department of Oral and Maxillofacial Surgery, Rijnstate Hospital, Arnhem, The Netherlands
D. L. Baker, P. J. W. Stoelinga, P A. Blijdorp, J. J. A. Brouns: Long-term stability after inferior maxillary repositioning by miniplate fixation. Int. J. Oral Maxillofac. Surg. 1992; 21: 320-326. © Munksgaard 1992 Abstract. Nineteen patients underwent Le Fort I osteotomy and inferior maxillary repositioning. Miniplates were used to maintain the maxilla in its new position. The patients were followed from 12 to 58 months, postoperatively. Fourteen patients were considered to be stable over the long term. Five patients had a long-term relapse of more than 30%. A tendency towards greater relapse was seen in patients with more than 5 mm inferior repositioning, and in patients who had concurrent segmental osteotomies of the maxilla. In spite of the use of miniplates, there continues to be an element of unpredictability with regard to vertical relapse after inferior maxillary repositioning, and this may be related to soft-tissue influences.
Accepted for publication 22 September 1992
Vertical maxillary hypoplasia is relatively rare as compared with other dentofacial deformities 3,H. It does, however, present a significant therapeutic challenge. Varying amounts of skeletal relapse have been reported after inferior maxillary repositioning, ranging from 0 to 100% 1'3-6'12. Several factors have been implicated as contributing to this instability. WESSBERG & EPI(ER discussed greater masticatory muscle activ-
inadequate stabilization techniques, and lack of bone grafts or poor bone-grafting techniques ~°. Several techniques designed to minimize relapse have been described, including coronoidectomy, hydroxylapatite (HA) blocks, and prestretching the elevator muscles 3,9,10.12. Variable results, however, have been reported from these techniques. Only one study documents the stability of the inferiorly reposi-
ity after inferior repositioning of the maxilla, leading to increased relapse tendency 11. ELIASet al. studied myotomies and prestretching of the elevator muscles to prevent relapse and found favorable results 3. WARDROP ~; WOLfORD listed additional factors contributing to instability, including inappropriate presurgical orthodontics, peroperative complications, inadequate maxillary mobilization during downfracture,
Key words: Le Fort I osteotomy; miniplates; stable fixation.
Fig. 2. Cephalometric tracing showing pre-
Fig. 1. Intraoperative plate position with bone grafts.
operatively identified landmarks. A template of the preoperative maxilla was then used for superimposing over subsequent postoperative cephalometric tracings.
321
Inferior maxillary repositioning Fig. 3. The sella-nasion line and a line perpendicular to it were used to measure the maxillary positions.
tioned maxilla in noncleft patients after Le Fort I o s t e o t o m y with miniplates. PE~SSON et al. studied 18 cases a n d f o u n d relapse to vary f r o m 0 to 100% with miniplates, b u t the study's period of follow-up was only 6 m o n t h s 5. This study reports o n the short- a n d l o n g - t e r m stability o f the inferiorly repositioned maxilla in noncleft patients after Le Fort I osteotomies with miniplate fixation.
Material
and
methods
In a 4-year period (1987 90), 191 Le Fort I osteotomies were performed at our institution, but only 19 patients (10%) underwent inferior maxillary repositioning. This group
Group 1 (OtolOa/o)
Group 2(125to25%) Group 3 (30to50%)
12 rnmofchangefrompresurgicalposition 10204611 , 818I~~L~~ 12 24 r ~ 8 j ~ H 6 1
mmof changefrompresurgicalposition ~HR6~H8~[H161002481iO :I11811i5i~3 r l 1 2 4
-4 -6 -g
~1
-4 -6
#10 #2 #13 #4 #16 #6 #7 BSO
NO
NO
BSO
A
NB
NO
NO
S
HA
NO NB
-8
#8 #19 S
NB
#14 #11 #12 #1 #5 NO
#17 #3 #g #18 #15
NO
S
NB
BSO
B
S
S
S
Fig. 4. A) Group l. B) Groups 2 and 3. Horizontal axis shows assigned patient numbers (#) for study. Vertical axis shows mm of change from presurgical position measured at Is. Clear bars represent vertical dimension of movement. Solid bars represent horizontal dimension of movement. First bar on left for each patient shows immediate postoperative position. Second bar is 3-6-month follow-up position. Last bar is latest follow-up position, and number of months after surgery is shown above bar. Range of relapse in vertical dimension is shown for each group in parentheses. BSO=patients with bilateral sagittal split setback osteotomies. S=patients with two or more segments in the maxilla. N o = n o orthodontic treatment, N B = n o bone graft. H A = H A block.
CategoryA
Category B
lessthan or equalto 5 mm of vertical lengthening n = 7 mmofverticallengthening 6
greaterthan 5 mm of verticallengthening n= 12 rnmofverticallengthening 12
5;-
• tO
•
8
•
•
4-
•
3
•
2
i
6
"
•
4 • 1 patient • 4 patients
1 0
•
I
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1
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]
i
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]
5
J
6
• 1 patient • 2 patients • 3 patients
2 i
7
0
i
0
i
1
i
I
I
I
2 3 4 5 mmofverticalrelapse
;
6
I
7
Fig. 5. One of seven patients with 5 mm or less vertical lengthening
Fig. 6. Eight of 12 patients with more than 5 mm of vertical lengthen-
had vertical relapse,
ing had vertical relapse.
322
B a k e r et al.
Fig. 7. Patient number 9 had 12 mm inferior positioning and 2 mm advancement of the maxilla. A BSO setback of the mandible was also done. Relapse in the maxilla was 30% in the vertical and nearly 100% in the horizontal. The clinical result was not completely satisfying. A, C, E, and G show the preoperative appearance. B, D, and H show the 6month postoperative appearance. F and I show the 24-month follow-up.
included 12 men and 7 women aged of 14M4 years with a mean age of 26. Thirteen of these patients also had a horizontal component to their maxillary repositioning, i.e. four maxillary setbacks and nine maxillary advancements. The patients' follow-up ranged from 12 to 58 months. Patients with cleft lip and palate and edentulous patients were not included in this study. The same surgical technique was used for all patients. The posterior separation was achieved by the tuberosity split technique, as described by TRIMBLE et all. Seven patients had no orthodontic treatment; in these cases arch bars were applied. With the aid of an acrylic splint, temporary intermaxillary fixation (IMF) was obtained
in the desired occlusion. Autogenous bone grafts were harvested from the anterior iliac crest in all but five cases. In three of those patients the anterior inferior repositioning was minimal (1.5-2.0 ram), while adequate posterior bone contact was maintained. In another patient, only plates were used, and in one patient porous H A blocks were used to bridge the gap; otherwise, corticocancellous blocks of appropriate dimensions were interposed between the osteotomy cuts of the lateral maxillary walls and the cortical portion of the graft positioned toward the periosteum. In some cases, onlay bone grafts were placed at the paranasal region to improve contour. Stabilization was achieved by means of four, small, four-hole, stainless
steel, Champy ® miniplates. In some cases Lshaped plates were used and in others straight plates, depending on the anatomy. Two plates were usually placed along the nasal aperture and the others at each zygomatico-maxillary buttress (Fig. 1). At least four screws were used in each plate. Six patients had concurrent maxillary segmental osteotomies performed. In these cases an occlusal acrylic splint was wired to the maxillary dentition, but no additional plates were used. After application of the miniplates, I M F was released and the occlusion checked. Three patients then underwent bilateral mandibular sagittal split setback osteotomies. Neither prestretching of the elevator muscles nor myotomies were performed.
Inferior maxillary repositioning
Postoperatively, two patients were kept in IMF; one for 2 weeks and another for 5 weeks. All patients were instructed to wear the acrylic occlusal splint for 2-6 weeks. The patients who had segmental osteotomies wore the splint wired to the maxillary dentition for 4-6 weeks. Sixteen patients had all plates removed 6-18 months postoperatively. Standard cephalometric radiographs in natural head position with teeth in centric relation or in a prefabricated splint were obtained preoperatively, 1-2 d postoperatively, 3 6 months postoperatively, before plate removal, and at the latest follow-up. The preoperative cephalometric head films were traced by the reference points described in Fig. 2. In the subsequent postoperative films, points Ptm, Sp, and Is were often more difficult to identify because of swelling, surgically altered landmarks, or orthodontic tooth movement. We therefore used the technique described by PERSSONet al. 5 to superimpose the preoperative maxilla on the postoperative films, using the hard palate and the incisor as a guide. With this technique, unit maxilla as a whole could better be assessed for stability than by relying on incisor position.
Measurements from SN and SNP were used to evaluate vertical and horizontal movements (Fig. 3). Cephalometric radiographs were made in the physiologic rest position during the planning phase; this allowed for better clinical assessment of the required amount of inferior vertical movement (Fig. 86). Results
Fig. 4 shows the postoperative changes. Any m o v e m e n t greater than 0.5 m m from the immediate postoperative position was recorded. The patients were divided into three groups according to the amount of relapse. Postoperative change in either the horizontal or the vertical direction was used to group the patients. G r o u p 1 consisted of nine patients who showed no relapse, except for one patient who had 10% relapse in a horizontal direction. The range for inferior maxillary repositioning in this group
323
was 1.5-9.5 mm. The range of movement in the horizontal dimension was - 4 to + 6 mm. Two patients in this group had concurrent bilateral sagittal split setback osteotomies, and two patients had maxillary segmental osteotomies concurrently performed. G r o u p 2 had five patients with 12-25% vertical or horizontal relapse. Vertical surgical m o v e m e n t ranged from 7 to 10 mm. The range of horizontal surgical m o v e m e n t was - 7 to + 6 mm. Relapse began between surgery and 6 months postoperatively in all five patients. N o patient in this group had other concurrent osteotomies performed. G r o u p 3 included five patients with 30-50% vertical postsurgical relapse. Horizontal relapse up to 100% occurred in one patient. Inferior maxillary repositioning in group 3 ranged from 1.5 to 12 mm. In the horizontal plane surgical m o v e m e n t ranged from - 6 to ÷ 5 mm.
324
B a k e r et aL
Fig. 8. Patient number 6 had 10 mm maxillary
inferior positioning and 6 mm maxillary advancement. No relapse was seen in this patient. No orthodontics were performed. A, C, and E show the preoperative appearance. G shows the physiologicrest position. B, D, and H show the 6-month follow-up appearance. F and I show the 15-month follow-up.
Relapse for group 3 patients began early and continued after the 3-6-month follow-up period, except in one patient in whom relapse began after the 3-6month follow-up period. Four of the five patients had concurrent maxillary segmental osteotomies, and one patient had a bilateral sagittal split setback osteotomy. The follow-up periods were similar for each of the three groups. No significant difference was identified relating the age or sex of the patients and postoperative relapse between groups. No difference was seen between patients
treated with or without orthodontics. No relationship between the timing of plate removal and the occurrence of relapse was seen except in one patient (no. 18, Fig. 4B) whose plates were removed because of pain 2 months postoperatively. No patient in any group had a poor postoperative occlusion, but some were found to have flaring of the maxillary incisors. Analysis of the data was also done by grouping the patients into two other categories (Figs. 5 and 6). Category A was for patients with less than 5 mm of lengthening, and category B for patients
with 5 mm or more vertical lengthening. Six of seven patients in category A had no relapse, and one patient (no. 3 from Fig. 4B) had 2.5 mm relapse. Four of 12 patients in category B had no relapse, six had 1-2 mm relapse, and two had more than 2 mm relapse. Discussion
It appears from these data that inferior repositioning of the maxilla at Le Fort I level is relatively rare. Only 10% of the patients undergoing a Le Fort I osteotomy had vertical lengthening of the
Inferior maxillary repositioning
maxilla. It is therefore understandable that little information is available on the long-term stability of this procedure. Sufficient information is available on the stability of Le Fort I osteotomies using rigid fixation, when used to impact or advance the maxilla2,4. All patients, except one who experienced postoperative relapse, began to show relapse in the early postoperative period (3-6 months), a finding similar to those of other authors 3's. In all five patients from group 2, all of the relapse occurred during the first 6 months. The five patients in group 3 continued to relapse beyond the short-term followup period. Four of the five patients in group 3 had segmental maxillary osteotomies. No other significant treatment differences were identified between the three groups. A L e Fort I osteotomy advancement alone has the advantage of adequate bone contact. However, advancement
combined with inferior positioning generally leads to little or no bone contact other than grafted bone. In these cases, most of the early postoperative stability is then dependent on the mode of fixation and to a lesser degree on the bone graft. Thus, even small inferior maxillary movements rely heavily on miniplates for stability. Five patients from our series had no bone grafts at all. Three patients were felt to have enough posterior bone contact to provide bony union. These three patients did not show any relapse. One patient (no. 3, group 3) had 5 mm inferior repositioning of the maxilla, as measured at Is. Despite this amount of downward repositioning, he received no bone grafts or H A blocks to bridge the gap. He relapsed 20% over the first 6 months and 30% from 6 months to 14 months. This patient shows that bone grafts are probably necessary for any gap larger than approximately 3 mm. One patient
325
received H A blocks to span the gap. This patient did not reveal any relapse. The primary force leading to relapse in patients with inferior maxillary repositioning is a result of the lengthening of the mandibular elevator muscles 3,11. The outcome of attempts to overcome these forces with miniplates is not yet predictable. This may be due to several factors. The miniplates are often longer than is necessary for other Le Fort I procedures. This is particularly true when a horizontal component is associated with the movement. Forces in both vectors are working against the maintenance of the new position. Longer plate length may allow for greater forces of leverage against the screws of the plate. Guiding elastics add to the strain on the screws. Thin bone from a hypoplastic maxilla may prevent firm screw placement. TURVEY has noted that despite efforts to control the new position of the max-
326
Baker et aL
illa mechanically, surgeons must deal with a biologic process, and thus the new position must be in harmony with the muscles of mastication if relapse is to be predictably controlled 8. He has further suggested that by instituting treatment that limits the change at the gonial angle, and thereby elevator muscle position, more stable results will follow 8. The early relapse seen in our patients and noted by other investigators may be the result of elevator muscle forces before their adaptation to the new position. It appeared that longterm relapse was greater among those who had segmental maxillary surgery. The sectioning of the maxilla in multiple segments, in spite of the dentally wired acrylic splint, may have allowed for some continued movement of the segments during healing, and this movement may also have contributed to relapse. As can be seen from the data in Figs. 4 and 5, eight patients with greater than 5 mm vertical lengthening had relapse, whereas only one with 5 m m or less vertical lengthening had relapse. Thus, the greater the vertical movement, the more likely some relapse may occur. Clinically, all patients in each group had acceptable long-term postoperative dental occlusion. In some cases, however, the occlusion was associated with maxillary incisor flaring. Appearance and
function had, however, subjectively improved in all cases (Figs. 7 and 8). It appears from this study that miniplates alone are not able to overcome completely the forces that cause relapse when used for inferior maxillary repositioning, but, in general, acceptable results can be achieved, provided that gaps are adequately grafted.
References
1. BELL WH, SCHEIDEMANGB. Correction of vertical maxillary deficiency: stability and soft tissue changes. J Oral Surg 1981: 39: 666-70. 2. CARPENTER CW, NANDA RS, CURRIER GF. The skeletal stability of Le Fort I downfracture osteotomies with rigid fixation. J Oral Maxillofac Surg 1989: 47: 922-5. 3. ELLIS E, CARLSON DS, FRYDENLUND S. Stability of midface augmentation: an experimental study of musculoskeletal interaction and fixation methods. J Oral Maxillofac Surg 1989: 47: 1062-8. 4. HEDEMARKA, FREIHOFER HPM. The behaviour of the maxilla in vertical movements after Le Fort I osteotomy. J Max.fac Surg 1978: 6: 244-9. 5. PERSSONG,~HELLEM S, NORD PG. Bone plates for stabilizing Le Fort I osteotomies. J Max.-fac Surg 1986: 14: 69-73. 6. QUEGADAJG, BELLWH, KAWAMURAH, et al. Skeletal stability after inferior maxillary repositioning. Int J Adult Orthod Orthogn Surg 1987: 2: 67-74.
7. TRIMBLE LD, TIDEMAN H, STOEL1NGA PJW. A modification of the pterygoid plate separation in low-level maxillary osteotomies. J Oral Maxillofac Surg 1983: 41: 544-6. 8. TURVEYT. Discussion of inferior maxillary repositioning. J Oral Maxillofac Surg 1989: 47:1069 71. 9. VAN NICKELSJE, JETERTD, ARAGONSB. Rigid fixation of maxillary osteotomies: a preliminary report and technique article. J Oral Surg 1985: 60: 262-5. 10. WARDROP RW, WOLFORD LM, Maxillary stability following downgraft and/or advancement procedures with stabilization using rigid fixation and porous block hydroxylapatite implant. J Oral Maxillofac Surg 1989: 47: 336-42. 11. WESSBERGG, EPKERBN. Sur~cal inferior repositioning of the maxilla: treatment considerations and comprehensive management. J Oral Surg 1981: 52:349 56. 12. WOLEORDLM, HILLIARDFW. The surgical-orthodontic correction of vertical dentofacial deformities. J Oral Surg 1981: 39: 883-97.
Address: Dr P. J. W. Stoelinga Department of Oral and Maxillofacial Surgery Rijnstate Hospital GZ Wagnerlaan 55 6815 AD Arnhem The Netherlands
Long-term stability after inferior maxillary repositioning by miniplate fixation
D a v i d L. B a k e r 1, P a u l J. W. S t o e l i n g a 2, Peter A. Blijdorp 2, J o h n J, A. B r o u n s 2 1Department of Oral and Maxillofacial Surgery, University of Washington, Seattle, WA, USA (presently in private practice), and 2Department of Oral and Maxillofacial Surgery, Rijnstate Hospital, Arnhem, The Netherlands
D. L. Baker, P. J. W. Stoelinga, P A. Blijdorp, J. J. A. Brouns: Long-term stability after inferior maxillary repositioning by miniplate fixation. Int. J. Oral Maxillofac. Surg. 1992; 21: 320-326. © Munksgaard 1992 Abstract. Nineteen patients underwent Le Fort I osteotomy and inferior maxillary repositioning. Miniplates were used to maintain the maxilla in its new position. The patients were followed from 12 to 58 months, postoperatively. Fourteen patients were considered to be stable over the long term. Five patients had a long-term relapse of more than 30%. A tendency towards greater relapse was seen in patients with more than 5 mm inferior repositioning, and in patients who had concurrent segmental osteotomies of the maxilla. In spite of the use of miniplates, there continues to be an element of unpredictability with regard to vertical relapse after inferior maxillary repositioning, and this may be related to soft-tissue influences.
Accepted for publication 22 September 1992
Vertical maxillary hypoplasia is relatively rare as compared with other dentofacial deformities 3,H. It does, however, present a significant therapeutic challenge. Varying amounts of skeletal relapse have been reported after inferior maxillary repositioning, ranging from 0 to 100% 1'3-6'12. Several factors have been implicated as contributing to this instability. WESSBERG & EPI(ER discussed greater masticatory muscle activ-
inadequate stabilization techniques, and lack of bone grafts or poor bone-grafting techniques ~°. Several techniques designed to minimize relapse have been described, including coronoidectomy, hydroxylapatite (HA) blocks, and prestretching the elevator muscles 3,9,10.12. Variable results, however, have been reported from these techniques. Only one study documents the stability of the inferiorly reposi-
ity after inferior repositioning of the maxilla, leading to increased relapse tendency 11. ELIASet al. studied myotomies and prestretching of the elevator muscles to prevent relapse and found favorable results 3. WARDROP ~; WOLfORD listed additional factors contributing to instability, including inappropriate presurgical orthodontics, peroperative complications, inadequate maxillary mobilization during downfracture,
Key words: Le Fort I osteotomy; miniplates; stable fixation.
Fig. 2. Cephalometric tracing showing pre-
Fig. 1. Intraoperative plate position with bone grafts.
operatively identified landmarks. A template of the preoperative maxilla was then used for superimposing over subsequent postoperative cephalometric tracings.
321
Inferior maxillary repositioning Fig. 3. The sella-nasion line and a line perpendicular to it were used to measure the maxillary positions.
tioned maxilla in noncleft patients after Le Fort I o s t e o t o m y with miniplates. PE~SSON et al. studied 18 cases a n d f o u n d relapse to vary f r o m 0 to 100% with miniplates, b u t the study's period of follow-up was only 6 m o n t h s 5. This study reports o n the short- a n d l o n g - t e r m stability o f the inferiorly repositioned maxilla in noncleft patients after Le Fort I osteotomies with miniplate fixation.
Material
and
methods
In a 4-year period (1987 90), 191 Le Fort I osteotomies were performed at our institution, but only 19 patients (10%) underwent inferior maxillary repositioning. This group
Group 1 (OtolOa/o)
Group 2(125to25%) Group 3 (30to50%)
12 rnmofchangefrompresurgicalposition 10204611 , 818I~~L~~ 12 24 r ~ 8 j ~ H 6 1
mmof changefrompresurgicalposition ~HR6~H8~[H161002481iO :I11811i5i~3 r l 1 2 4
-4 -6 -g
~1
-4 -6
#10 #2 #13 #4 #16 #6 #7 BSO
NO
NO
BSO
A
NB
NO
NO
S
HA
NO NB
-8
#8 #19 S
NB
#14 #11 #12 #1 #5 NO
#17 #3 #g #18 #15
NO
S
NB
BSO
B
S
S
S
Fig. 4. A) Group l. B) Groups 2 and 3. Horizontal axis shows assigned patient numbers (#) for study. Vertical axis shows mm of change from presurgical position measured at Is. Clear bars represent vertical dimension of movement. Solid bars represent horizontal dimension of movement. First bar on left for each patient shows immediate postoperative position. Second bar is 3-6-month follow-up position. Last bar is latest follow-up position, and number of months after surgery is shown above bar. Range of relapse in vertical dimension is shown for each group in parentheses. BSO=patients with bilateral sagittal split setback osteotomies. S=patients with two or more segments in the maxilla. N o = n o orthodontic treatment, N B = n o bone graft. H A = H A block.
CategoryA
Category B
lessthan or equalto 5 mm of vertical lengthening n = 7 mmofverticallengthening 6
greaterthan 5 mm of verticallengthening n= 12 rnmofverticallengthening 12
5;-
• tO
•
8
•
•
4-
•
3
•
2
i
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"
•
4 • 1 patient • 4 patients
1 0
•
I
0
J
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]
i
2 3 4 mmofverticalrelapse
]
5
J
6
• 1 patient • 2 patients • 3 patients
2 i
7
0
i
0
i
1
i
I
I
I
2 3 4 5 mmofverticalrelapse
;
6
I
7
Fig. 5. One of seven patients with 5 mm or less vertical lengthening
Fig. 6. Eight of 12 patients with more than 5 mm of vertical lengthen-
had vertical relapse,
ing had vertical relapse.
322
B a k e r et al.
Fig. 7. Patient number 9 had 12 mm inferior positioning and 2 mm advancement of the maxilla. A BSO setback of the mandible was also done. Relapse in the maxilla was 30% in the vertical and nearly 100% in the horizontal. The clinical result was not completely satisfying. A, C, E, and G show the preoperative appearance. B, D, and H show the 6month postoperative appearance. F and I show the 24-month follow-up.
included 12 men and 7 women aged of 14M4 years with a mean age of 26. Thirteen of these patients also had a horizontal component to their maxillary repositioning, i.e. four maxillary setbacks and nine maxillary advancements. The patients' follow-up ranged from 12 to 58 months. Patients with cleft lip and palate and edentulous patients were not included in this study. The same surgical technique was used for all patients. The posterior separation was achieved by the tuberosity split technique, as described by TRIMBLE et all. Seven patients had no orthodontic treatment; in these cases arch bars were applied. With the aid of an acrylic splint, temporary intermaxillary fixation (IMF) was obtained
in the desired occlusion. Autogenous bone grafts were harvested from the anterior iliac crest in all but five cases. In three of those patients the anterior inferior repositioning was minimal (1.5-2.0 ram), while adequate posterior bone contact was maintained. In another patient, only plates were used, and in one patient porous H A blocks were used to bridge the gap; otherwise, corticocancellous blocks of appropriate dimensions were interposed between the osteotomy cuts of the lateral maxillary walls and the cortical portion of the graft positioned toward the periosteum. In some cases, onlay bone grafts were placed at the paranasal region to improve contour. Stabilization was achieved by means of four, small, four-hole, stainless
steel, Champy ® miniplates. In some cases Lshaped plates were used and in others straight plates, depending on the anatomy. Two plates were usually placed along the nasal aperture and the others at each zygomatico-maxillary buttress (Fig. 1). At least four screws were used in each plate. Six patients had concurrent maxillary segmental osteotomies performed. In these cases an occlusal acrylic splint was wired to the maxillary dentition, but no additional plates were used. After application of the miniplates, I M F was released and the occlusion checked. Three patients then underwent bilateral mandibular sagittal split setback osteotomies. Neither prestretching of the elevator muscles nor myotomies were performed.
Inferior maxillary repositioning
Postoperatively, two patients were kept in IMF; one for 2 weeks and another for 5 weeks. All patients were instructed to wear the acrylic occlusal splint for 2-6 weeks. The patients who had segmental osteotomies wore the splint wired to the maxillary dentition for 4-6 weeks. Sixteen patients had all plates removed 6-18 months postoperatively. Standard cephalometric radiographs in natural head position with teeth in centric relation or in a prefabricated splint were obtained preoperatively, 1-2 d postoperatively, 3 6 months postoperatively, before plate removal, and at the latest follow-up. The preoperative cephalometric head films were traced by the reference points described in Fig. 2. In the subsequent postoperative films, points Ptm, Sp, and Is were often more difficult to identify because of swelling, surgically altered landmarks, or orthodontic tooth movement. We therefore used the technique described by PERSSONet al. 5 to superimpose the preoperative maxilla on the postoperative films, using the hard palate and the incisor as a guide. With this technique, unit maxilla as a whole could better be assessed for stability than by relying on incisor position.
Measurements from SN and SNP were used to evaluate vertical and horizontal movements (Fig. 3). Cephalometric radiographs were made in the physiologic rest position during the planning phase; this allowed for better clinical assessment of the required amount of inferior vertical movement (Fig. 86). Results
Fig. 4 shows the postoperative changes. Any m o v e m e n t greater than 0.5 m m from the immediate postoperative position was recorded. The patients were divided into three groups according to the amount of relapse. Postoperative change in either the horizontal or the vertical direction was used to group the patients. G r o u p 1 consisted of nine patients who showed no relapse, except for one patient who had 10% relapse in a horizontal direction. The range for inferior maxillary repositioning in this group
323
was 1.5-9.5 mm. The range of movement in the horizontal dimension was - 4 to + 6 mm. Two patients in this group had concurrent bilateral sagittal split setback osteotomies, and two patients had maxillary segmental osteotomies concurrently performed. G r o u p 2 had five patients with 12-25% vertical or horizontal relapse. Vertical surgical m o v e m e n t ranged from 7 to 10 mm. The range of horizontal surgical m o v e m e n t was - 7 to + 6 mm. Relapse began between surgery and 6 months postoperatively in all five patients. N o patient in this group had other concurrent osteotomies performed. G r o u p 3 included five patients with 30-50% vertical postsurgical relapse. Horizontal relapse up to 100% occurred in one patient. Inferior maxillary repositioning in group 3 ranged from 1.5 to 12 mm. In the horizontal plane surgical m o v e m e n t ranged from - 6 to ÷ 5 mm.
324
B a k e r et aL
Fig. 8. Patient number 6 had 10 mm maxillary
inferior positioning and 6 mm maxillary advancement. No relapse was seen in this patient. No orthodontics were performed. A, C, and E show the preoperative appearance. G shows the physiologicrest position. B, D, and H show the 6-month follow-up appearance. F and I show the 15-month follow-up.
Relapse for group 3 patients began early and continued after the 3-6-month follow-up period, except in one patient in whom relapse began after the 3-6month follow-up period. Four of the five patients had concurrent maxillary segmental osteotomies, and one patient had a bilateral sagittal split setback osteotomy. The follow-up periods were similar for each of the three groups. No significant difference was identified relating the age or sex of the patients and postoperative relapse between groups. No difference was seen between patients
treated with or without orthodontics. No relationship between the timing of plate removal and the occurrence of relapse was seen except in one patient (no. 18, Fig. 4B) whose plates were removed because of pain 2 months postoperatively. No patient in any group had a poor postoperative occlusion, but some were found to have flaring of the maxillary incisors. Analysis of the data was also done by grouping the patients into two other categories (Figs. 5 and 6). Category A was for patients with less than 5 mm of lengthening, and category B for patients
with 5 mm or more vertical lengthening. Six of seven patients in category A had no relapse, and one patient (no. 3 from Fig. 4B) had 2.5 mm relapse. Four of 12 patients in category B had no relapse, six had 1-2 mm relapse, and two had more than 2 mm relapse. Discussion
It appears from these data that inferior repositioning of the maxilla at Le Fort I level is relatively rare. Only 10% of the patients undergoing a Le Fort I osteotomy had vertical lengthening of the
Inferior maxillary repositioning
maxilla. It is therefore understandable that little information is available on the long-term stability of this procedure. Sufficient information is available on the stability of Le Fort I osteotomies using rigid fixation, when used to impact or advance the maxilla2,4. All patients, except one who experienced postoperative relapse, began to show relapse in the early postoperative period (3-6 months), a finding similar to those of other authors 3's. In all five patients from group 2, all of the relapse occurred during the first 6 months. The five patients in group 3 continued to relapse beyond the short-term followup period. Four of the five patients in group 3 had segmental maxillary osteotomies. No other significant treatment differences were identified between the three groups. A L e Fort I osteotomy advancement alone has the advantage of adequate bone contact. However, advancement
combined with inferior positioning generally leads to little or no bone contact other than grafted bone. In these cases, most of the early postoperative stability is then dependent on the mode of fixation and to a lesser degree on the bone graft. Thus, even small inferior maxillary movements rely heavily on miniplates for stability. Five patients from our series had no bone grafts at all. Three patients were felt to have enough posterior bone contact to provide bony union. These three patients did not show any relapse. One patient (no. 3, group 3) had 5 mm inferior repositioning of the maxilla, as measured at Is. Despite this amount of downward repositioning, he received no bone grafts or H A blocks to bridge the gap. He relapsed 20% over the first 6 months and 30% from 6 months to 14 months. This patient shows that bone grafts are probably necessary for any gap larger than approximately 3 mm. One patient
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received H A blocks to span the gap. This patient did not reveal any relapse. The primary force leading to relapse in patients with inferior maxillary repositioning is a result of the lengthening of the mandibular elevator muscles 3,11. The outcome of attempts to overcome these forces with miniplates is not yet predictable. This may be due to several factors. The miniplates are often longer than is necessary for other Le Fort I procedures. This is particularly true when a horizontal component is associated with the movement. Forces in both vectors are working against the maintenance of the new position. Longer plate length may allow for greater forces of leverage against the screws of the plate. Guiding elastics add to the strain on the screws. Thin bone from a hypoplastic maxilla may prevent firm screw placement. TURVEY has noted that despite efforts to control the new position of the max-
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Baker et aL
illa mechanically, surgeons must deal with a biologic process, and thus the new position must be in harmony with the muscles of mastication if relapse is to be predictably controlled 8. He has further suggested that by instituting treatment that limits the change at the gonial angle, and thereby elevator muscle position, more stable results will follow 8. The early relapse seen in our patients and noted by other investigators may be the result of elevator muscle forces before their adaptation to the new position. It appeared that longterm relapse was greater among those who had segmental maxillary surgery. The sectioning of the maxilla in multiple segments, in spite of the dentally wired acrylic splint, may have allowed for some continued movement of the segments during healing, and this movement may also have contributed to relapse. As can be seen from the data in Figs. 4 and 5, eight patients with greater than 5 mm vertical lengthening had relapse, whereas only one with 5 m m or less vertical lengthening had relapse. Thus, the greater the vertical movement, the more likely some relapse may occur. Clinically, all patients in each group had acceptable long-term postoperative dental occlusion. In some cases, however, the occlusion was associated with maxillary incisor flaring. Appearance and
function had, however, subjectively improved in all cases (Figs. 7 and 8). It appears from this study that miniplates alone are not able to overcome completely the forces that cause relapse when used for inferior maxillary repositioning, but, in general, acceptable results can be achieved, provided that gaps are adequately grafted.
References
1. BELL WH, SCHEIDEMANGB. Correction of vertical maxillary deficiency: stability and soft tissue changes. J Oral Surg 1981: 39: 666-70. 2. CARPENTER CW, NANDA RS, CURRIER GF. The skeletal stability of Le Fort I downfracture osteotomies with rigid fixation. J Oral Maxillofac Surg 1989: 47: 922-5. 3. ELLIS E, CARLSON DS, FRYDENLUND S. Stability of midface augmentation: an experimental study of musculoskeletal interaction and fixation methods. J Oral Maxillofac Surg 1989: 47: 1062-8. 4. HEDEMARKA, FREIHOFER HPM. The behaviour of the maxilla in vertical movements after Le Fort I osteotomy. J Max.fac Surg 1978: 6: 244-9. 5. PERSSONG,~HELLEM S, NORD PG. Bone plates for stabilizing Le Fort I osteotomies. J Max.-fac Surg 1986: 14: 69-73. 6. QUEGADAJG, BELLWH, KAWAMURAH, et al. Skeletal stability after inferior maxillary repositioning. Int J Adult Orthod Orthogn Surg 1987: 2: 67-74.
7. TRIMBLE LD, TIDEMAN H, STOEL1NGA PJW. A modification of the pterygoid plate separation in low-level maxillary osteotomies. J Oral Maxillofac Surg 1983: 41: 544-6. 8. TURVEYT. Discussion of inferior maxillary repositioning. J Oral Maxillofac Surg 1989: 47:1069 71. 9. VAN NICKELSJE, JETERTD, ARAGONSB. Rigid fixation of maxillary osteotomies: a preliminary report and technique article. J Oral Surg 1985: 60: 262-5. 10. WARDROP RW, WOLFORD LM, Maxillary stability following downgraft and/or advancement procedures with stabilization using rigid fixation and porous block hydroxylapatite implant. J Oral Maxillofac Surg 1989: 47: 336-42. 11. WESSBERGG, EPKERBN. Sur~cal inferior repositioning of the maxilla: treatment considerations and comprehensive management. J Oral Surg 1981: 52:349 56. 12. WOLEORDLM, HILLIARDFW. The surgical-orthodontic correction of vertical dentofacial deformities. J Oral Surg 1981: 39: 883-97.
Address: Dr P. J. W. Stoelinga Department of Oral and Maxillofacial Surgery Rijnstate Hospital GZ Wagnerlaan 55 6815 AD Arnhem The Netherlands
