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Changes after correction of maxillary retrusion by Le Fort I osteotomy
Reconstructive Surgery
Changes after correction of maxillary retrusion by Le Fort l
Ulla-Stina Rondahl, Hans Bystedt, Bj6rn Enqvist and Olle Malmgren Department of Orthodontics, Eastman Institutet and Department of Maxillofacial Surgery, Sabbatsbergs Sjukhus, Stockholm, Sweden
osteotomy A comparison of 2 methods of skeletal fixation U.-S. Rondahl, H. Bystedt, B. Enqvist and O. Malmgren: Changes after correction of maxillary retrusion by Le Fort 1 osteotomy. A comparison of two methods of skeletal fixation. Int. J. Oral Maxillofac. Surg. 1988; 17: 165-169. Abstract. 2 methods of skeletal fixation are compared in 24 patients with maxillary retrusion treated with Le Fort I osteotomy only: group I, intraosseous fixation only (10 patients); group II, enhanced fixation, intraosseous and suspension wires (14 patients). Follow-up checks on the patients were carried out using lateral cephalograms. The changes of the maxillary position in relation to the anterior cranial base were analyzed via a technique of superimposition in a computer system without using conventional landmarks. Vertical and horizontal changes and rotations were studied. The method error was small. In the vertical direction, there was a significant difference between the groups. In group I, the vertical relapse during the early postoperative period was 55%, while in group II, it was only 15%, The conclusion is that a rigid vertical fixation is needed.
Le Fort I osteotomy with anterior and inferior replacement of the maxilla in patients with maxillary retrusion has been reported as unstable in the vertical direction, by WILMAR7, HEDEMARK & FREIHOFER4 and WOLFORD t~ HILLIARD8. Rotation of the maxilla downwardsbackwards has also been found to be unstable by BELL & SCI-~tDEMAN2 and HEDEMARK & FREIHOFER4. In order to minimize the relapse, PERSSON et al. 6 used bone plates, WOLFORD & HILLIARD8 a Steinman pin between the zygomatic butress and the wafer, whilst BELL • SCHEIDEMAN2 used careful application of bone grafts and suspension wires. A problem in recording changes following maxillary surgery is that conventional cephalometric landmarks are affected by the surgical procedure. HOUSTON et al. 5 have recently proposed a superimposition technique to minimize this problem. Cooperation between the disciplines of oral surgery and orthodontics is required to establish good occlusion and optimal aestethics. Before surgery, the orthodontist makes the alignment of teeth over basal bone and coordinates the dental arches to achieve the best possible functional relationship
after surgery. The aim of this study was (1) to find a method for recording changes of the maxilla without using conventional landmarks, (2) to analyze the effect of Le Fort I osteotomy in patients treated by surgeons and orthodontists a n d (3) to compare two methods of fixation regarding postoperative stability: (i) intraosseous fixation only; (ii) enhanced fixation.
Material and methods Patients This study concerns 24 patients (12 female, 12 male) aged from 15-47 years (Table 1). They were all treated with Le Fort I osteotomy as the only surgical procedure at the Clinic of Maxillofacial Surgery, Sabbatsbergs Hospital, Stockholm, between 1977-1985. All patients were diagnosed as having maxillary retrusion, which means a maxillo-mandibular disharmony aestethically manifested in the maxilla and an Angle class III malocclusion with an anterior crossbite. Furthermore, 3 patients had a cleft-lip-palate deformity (CLP) and 2 had a skeletal open bite (Fig. 1).
Surgical technique A horizontal osteotomy was made from the maxillary tuberosity to the piriform aperture.
Key words: Le Fort I osteotomy; orthogenathic surgery; rigid fixation. Accepted for publication 24 November 1987
The maxilla was separated from the base of the nasal septum, the lateral nasal walls and the pterygoid process. After downfracture, the maxilla was moved forwards and downwards. Cancellous bone grafts as thin bone chips were taken from the lilac crest and were closely packed in the space between the osteotomy margins.
Fixation methods The patients were divided into 2 groups, according to the type of fixation: group I (n = 10), intraosseous fixation only; group II (n = 14), enhanced fixation. Both groups received intermaxillary fixation (IMF). The intraosseous fixation was made with ligatures seated in the region of the piriform aperture and below the zygomatic process (Fig. 2). The enhanced fixation was made with intraosseous fixation and suspension wires over the piriform aperture in 6 patients, around the
Table 1. Age range at surgery, 12 female, 12 male Age (years)
No. of patients
15-20 20-25 25-30 35-40 40
12 5 2 4 1
total
24
166
R o n d a h l et al.
Fig. 1. A 20-year-old female patient with a maxillary retrusion and an Angle CI III malocclusion with an anterior crossbite. She was treated with a fixed orthodontic appliance and a Le Fort I osteotomy. The maxilla was moved 9 m m forwards, 2 m m downwards and rotated 2 °. (A), (B) and (C), before treatment. (D), (E) and (F), 2 years after treatment.
zygomatic arch in 4 patients and around the infraorbital crest in 2 patients. In 2 patients, the enhanced fixation consisted of C h a m p y ® bone plates. The enhanced fixation and I M F was maintained for 5 6 weeks (Fig. 3). The method of analysis
Follow-up checks of the patients were made with lateral cephalograms. Lateral headfilms were taken before surgery, 3-5 days after surgery, after release of intermaxillary fixation (IMF) and 12-24 m o n t h s after surgery. The X-ray method was standardized with a linear
magnification of 10%. The changes of the maxillary position in relation to the anterior cranial base were analyzed with a computer system. Horizontal and vertical changes and rotations were studied. The anterior cranial base and the maxilla were superimposed in pairs ofheadfilms (before surgery after surgery; after surgery at release of IMF, etc.). The technique for superimposition was developed according to principles given by BAUMRIND & MIntER ~ and further developed by HOUSTON et aU. In the first film of each pair, 4 reference points ("fidusial points") were marked directly on the film. In marking
the fidusial points, a clear plastic template with 4 holes, making a 100 m m square, was used. The 4 points were then transferred to the 2nd film of the pair by superimposing on the anterior cranial base and copied to a tracing film. In the next step, the maxilla was used for superimposition and the 4 fidusial points were marked again on the same tracing. There were then 8 reference points making 2 squares on the tracing. These 8 reference points were digitized. The m e a n of the Ist 4 and the 2nd 4 reference points in the xand y-dimensions was calculated. The difference between these 2 means was the change
Fixation in Le Fort I osteotomy
167
B Fig. 2. Fixation method used in patients; group I (N= 10); intermaxillary fixation with a wafer, intraosseous fixation only. of the position of the maxilla. The rotation was calculated as the change of the midline through the respective squares (Fig. 4). The method error of the superimposing technique has been studied by repeated registrations. 3 different methods for superimposing of the maxilla have been investigated. (1) Superimposition on the hard palate and the central incisors. (2) Superimposition on a posterior and an anterior intraosseous wire. (3) Superimposition on the hard palate and an anterior intraosseous wire. The accuracy of each of these 3 methods was decided by superimposing 5 pairs of randomly chosen lateral headfilms. The superimpositions were made by one person (USR) on 2 occasions and separated by at least 1 week. The error of the measurement was calculated with the formula cS=l/Xd2/2N , where d is the difference between the 2 registrations and N is the number of repeated registrations. The least difference between the 2 occasions was found using method (3). This method was analysed once more in a series of independent repeated superimpositions of 10 pairs of head films. The method error was less than 0.4 mm in the vertical and horizontal direction and less than 0.9 ° for rotation. This method was used in the continued study. Results
Intraosseous fixation only (group I, n = 10) and enhanced fixation (group II, n = 14) (Table 2) A t surgery, the maxilla was m o v e d alm o s t the same distance in b o t h groups. T h e a n t e r i o r m o v e m e n t was 5.6 m m in g r o u p I a n d 5.9 m m in g r o u p II a n d the
C
D
Fig. 3. Fixation methods used in patients; group II ( N - 1 4 ) ; intermaxillary IIA~ d wlth a wafer. Suspension wires (A) over the piriform aperture, (B) around the infraorbital crest and (C) around the zygomatic arch. Intraosseous fixation with bone plates (D). "
inferior m o v e m e n t was 2.0 m m a n d 1.2 m m , respectively. The maxilla was rotated d o w n w a r d s b a c k w a r d s 3.2 ° in g r o u p I a n d 2.9 ° in g r o u p II.
During the period immediately after surgery until release o f I M F 5 weeks later, a l m o s t n o h o r i z o n t a l change was seen in either group. In the vertical dimension, there was a significant difference between the groups. In g r o u p I, the vertical c h a n g e was 1.1 m m a n d in g r o u p II 0.2 mm.
During the period from release o f I M F until 12-24 months later, there was a m e a n h o r i z o n t a l relapse o f 1.0 m m posterior in g r o u p I a n d 0.6 m m in g r o u p
II. N o relapse of the vertical changes a n d r o t a t i o n s was observed. Discussion
The p a t i e n t s included in this study constitute a u n i f o r m g r o u p with similar diagnosis (maxillary retrusion) treated with the same surgical technique in the maxilla only, preceded by o r t h o d o n t i c treatment. F o r describing the change of maxillary position, the usual cephalometric points, pterygomaxillare (ptm) a n d a n t e r i o r nasal spine (sp), are n o t ideal as they are situated in the osteo t o m y area. D e n t a l points are likewise
168
R o n d a h l et al.
..-'...-
l
]
@®
(
(9
Q
,.--Q
A
,'-.',®
B
Fig. 4. Superimposition technique used for evaluation of changes in maxillary position in
pairs of lateral head films. (A) In the first film of each pair, 4 reference points were marked directly on the film. The 4 reference points were then transferred to the second film of the pair by superimposing on the anterior cranial base and then copied to a tracing film. (B) Superimposition on the maxilla. The 4 reference points were marked again on the same tracing film. The 8 reference points were used to calculate the change of position of the maxilla.
not suitable, as t o o t h movements are c o m m o n during the period of observation. Therefore, bone-structures outside the osteotomy area and steel liga-
tures were used for the superimposition. The method error was small. H o w ever, HOUSTON et al. 5 point out that one cannot be confident at the 5% level that
Table 2. Changes after Le Fort I osteotomy in 24 patients
Group I intraosseous wires only N=10 At surgery horizontal vertical rotation
x SD x SD x SD
Group II enhanced fixation; intraosseous and suspension wires N=14
5.6 2.6 -- 2.0 1.9 3.2 4.2
5.9 2.4 - 1.2 2.4 2.9 3.0
3-5 days postoperatively to release of IMF horizontal x 0.1 SD 1.0 vertical x l. 1 SD 1.2 rotation x --0.2 SD 1.0
- 0.1 0.8 0.2* 0.6 -0.1 1.0
From release of IMF to check up after 12-24 months horizontal x - i .0 SD 1.7 vertical x - 0.2 SD 1.0 rotation x 0.8 SD 1.6
-0.6 0.9 - 0.4 0.8 - 0.0 1.9
* P < 0.05.~
Horizontal changes measured in mm. A positive value indicates an anterior change, a negative a posterior change. Vertical changes measured in mm. A positive value indicates a superior change, a negative an inferior change. Changes in rotation measured in degrees. A positive value indicates a posterior rotation, a negative an anterior rotation.
changes in the individual reflect real changes, unless the differences are greater than twice the m e t h o d error for that measurement. This means that changes in the horizontal and vertical dimension in the present study less than 0.8 m m and rotations less than 1.8 ° should be interpreted with caution. The follow-up period was 12-24 months. During the fixation period, no horizontal changes were seen. A horizontal relapse was recorded between release o f I M F and the check-up after 12-24 months, which is in agreement with earlier observations by WILMAR7. During the fixation period, the vertical change in group I, with intraosseous fixation only, was 55% of the inferior replacement. A similar a m o u n t o f relapse is reported by WILMAR7, HEDEMARK & FREIHOFER4 and WOLrORD & HILLIARD8. BELL 8~ SCHEIDEMAN2 measured a vertical relapse of 30%. PERSSON et al. 6 reported a relapse of 20% when bone plates were used. The vertical change seen in group II, patients with enhanced fixation, was only 15% of the inferior replacement, which is less than earlier reported. During the period from release of I M F to the check-up 12-24 months later, no further vertical change was seen in either group, which is in agreement with studies by WILMAR7, BELL • SCHEIDEMAN2 and WOLFORD & HILLIARD8. In most patients, the maxilla was rotated downwards (posterior rotation) at the surgical advancement. The amount of rotation did not change during the fixation period. After release of IMF, there was even a small increase of rotation in some patients. This observation differs from the report m a d e by HEDEMARK & FREIHOFER4. Relapse after tipping of the maxilla forwards and downwards has also been reported by BUNDGARD et al. 3. The reason for the small changes during the fixation period in group II in the present study is probably the use o f suspension wires. These wires press the loosened maxilla and the bone grafts superiorly into a distinct vertical position. If the fixation consists ofintraosseous wires only, the relapse tendency is greater during the healing period. The maxilla and the mandible form a block by the intermaxillary fixation. The patient's efforts to open the m o u t h after surgery brings this rather mobile block downwards and backwards. Clinical factors such as how the patient is awakened after anesthesia are probably also important. The conclusion from this
Fixation in L e Fort I osteotomy study is t h a t a rigid vertical fixation is to be advocated.
References 1. Baamrind, S. & Miller, D. M.: Computeraided head film analysis: The University of California San Franscisco method. Am. J. Orthodont. 1980: 78: 41-65. 2. Bell, W. H. & Scheideman, G. B.: Correction of vertical maxillary deficency: stability and soft tissue changes. J. Oral Surg. 1981: 39: 666-670. 3. Bundgaard, M., Melsen, B. & Terp, S.:
Changes during and following total maxillary osteotomy/Le Fort I procedure): a cephalometric study. Europ J. Orthodont. 1986: 8: 21-29. 4. Hedemark, A. & Freihofer, H. P., Jr.: The behaviour of the maxilla in vertical movement after the Fort I osteotomy. J. Max. Fac. Surg. 1978: 6: 244-249. 5. Houston, W. J. B., Jones, E. & James, D. R.: A method of recording change in maxillary position following orthognathic surgery. Europ. J. Orthodont. 1987: 9: 9-14. 6. Persson, G., Hellem, S. & Nord, P. G.: Bone-plates for stabilizing Le Fort I oste-
169
otomies. J. Max. Fac. Surg. 1986: 14: 69-73. 7. Willmar, K.: On Le Fort I osteotomy. Scand J. Plast. Reconstr. Surg. 1974: Suppl. 12. 8. Wolford, L. & Hilliard, F. W.: The surgical-orthodontic correction of vertical dentofacial deformities. J. Oral. Surg. 1981: 39: 883-897. Address: Olle Malmgren Eastmaninstitutet Dalagatan 11 S-113 24 Stockholm Sweden
Changes after correction of maxillary retrusion by Le Fort l
Ulla-Stina Rondahl, Hans Bystedt, Bj6rn Enqvist and Olle Malmgren Department of Orthodontics, Eastman Institutet and Department of Maxillofacial Surgery, Sabbatsbergs Sjukhus, Stockholm, Sweden
osteotomy A comparison of 2 methods of skeletal fixation U.-S. Rondahl, H. Bystedt, B. Enqvist and O. Malmgren: Changes after correction of maxillary retrusion by Le Fort 1 osteotomy. A comparison of two methods of skeletal fixation. Int. J. Oral Maxillofac. Surg. 1988; 17: 165-169. Abstract. 2 methods of skeletal fixation are compared in 24 patients with maxillary retrusion treated with Le Fort I osteotomy only: group I, intraosseous fixation only (10 patients); group II, enhanced fixation, intraosseous and suspension wires (14 patients). Follow-up checks on the patients were carried out using lateral cephalograms. The changes of the maxillary position in relation to the anterior cranial base were analyzed via a technique of superimposition in a computer system without using conventional landmarks. Vertical and horizontal changes and rotations were studied. The method error was small. In the vertical direction, there was a significant difference between the groups. In group I, the vertical relapse during the early postoperative period was 55%, while in group II, it was only 15%, The conclusion is that a rigid vertical fixation is needed.
Le Fort I osteotomy with anterior and inferior replacement of the maxilla in patients with maxillary retrusion has been reported as unstable in the vertical direction, by WILMAR7, HEDEMARK & FREIHOFER4 and WOLFORD t~ HILLIARD8. Rotation of the maxilla downwardsbackwards has also been found to be unstable by BELL & SCI-~tDEMAN2 and HEDEMARK & FREIHOFER4. In order to minimize the relapse, PERSSON et al. 6 used bone plates, WOLFORD & HILLIARD8 a Steinman pin between the zygomatic butress and the wafer, whilst BELL • SCHEIDEMAN2 used careful application of bone grafts and suspension wires. A problem in recording changes following maxillary surgery is that conventional cephalometric landmarks are affected by the surgical procedure. HOUSTON et al. 5 have recently proposed a superimposition technique to minimize this problem. Cooperation between the disciplines of oral surgery and orthodontics is required to establish good occlusion and optimal aestethics. Before surgery, the orthodontist makes the alignment of teeth over basal bone and coordinates the dental arches to achieve the best possible functional relationship
after surgery. The aim of this study was (1) to find a method for recording changes of the maxilla without using conventional landmarks, (2) to analyze the effect of Le Fort I osteotomy in patients treated by surgeons and orthodontists a n d (3) to compare two methods of fixation regarding postoperative stability: (i) intraosseous fixation only; (ii) enhanced fixation.
Material and methods Patients This study concerns 24 patients (12 female, 12 male) aged from 15-47 years (Table 1). They were all treated with Le Fort I osteotomy as the only surgical procedure at the Clinic of Maxillofacial Surgery, Sabbatsbergs Hospital, Stockholm, between 1977-1985. All patients were diagnosed as having maxillary retrusion, which means a maxillo-mandibular disharmony aestethically manifested in the maxilla and an Angle class III malocclusion with an anterior crossbite. Furthermore, 3 patients had a cleft-lip-palate deformity (CLP) and 2 had a skeletal open bite (Fig. 1).
Surgical technique A horizontal osteotomy was made from the maxillary tuberosity to the piriform aperture.
Key words: Le Fort I osteotomy; orthogenathic surgery; rigid fixation. Accepted for publication 24 November 1987
The maxilla was separated from the base of the nasal septum, the lateral nasal walls and the pterygoid process. After downfracture, the maxilla was moved forwards and downwards. Cancellous bone grafts as thin bone chips were taken from the lilac crest and were closely packed in the space between the osteotomy margins.
Fixation methods The patients were divided into 2 groups, according to the type of fixation: group I (n = 10), intraosseous fixation only; group II (n = 14), enhanced fixation. Both groups received intermaxillary fixation (IMF). The intraosseous fixation was made with ligatures seated in the region of the piriform aperture and below the zygomatic process (Fig. 2). The enhanced fixation was made with intraosseous fixation and suspension wires over the piriform aperture in 6 patients, around the
Table 1. Age range at surgery, 12 female, 12 male Age (years)
No. of patients
15-20 20-25 25-30 35-40 40
12 5 2 4 1
total
24
166
R o n d a h l et al.
Fig. 1. A 20-year-old female patient with a maxillary retrusion and an Angle CI III malocclusion with an anterior crossbite. She was treated with a fixed orthodontic appliance and a Le Fort I osteotomy. The maxilla was moved 9 m m forwards, 2 m m downwards and rotated 2 °. (A), (B) and (C), before treatment. (D), (E) and (F), 2 years after treatment.
zygomatic arch in 4 patients and around the infraorbital crest in 2 patients. In 2 patients, the enhanced fixation consisted of C h a m p y ® bone plates. The enhanced fixation and I M F was maintained for 5 6 weeks (Fig. 3). The method of analysis
Follow-up checks of the patients were made with lateral cephalograms. Lateral headfilms were taken before surgery, 3-5 days after surgery, after release of intermaxillary fixation (IMF) and 12-24 m o n t h s after surgery. The X-ray method was standardized with a linear
magnification of 10%. The changes of the maxillary position in relation to the anterior cranial base were analyzed with a computer system. Horizontal and vertical changes and rotations were studied. The anterior cranial base and the maxilla were superimposed in pairs ofheadfilms (before surgery after surgery; after surgery at release of IMF, etc.). The technique for superimposition was developed according to principles given by BAUMRIND & MIntER ~ and further developed by HOUSTON et aU. In the first film of each pair, 4 reference points ("fidusial points") were marked directly on the film. In marking
the fidusial points, a clear plastic template with 4 holes, making a 100 m m square, was used. The 4 points were then transferred to the 2nd film of the pair by superimposing on the anterior cranial base and copied to a tracing film. In the next step, the maxilla was used for superimposition and the 4 fidusial points were marked again on the same tracing. There were then 8 reference points making 2 squares on the tracing. These 8 reference points were digitized. The m e a n of the Ist 4 and the 2nd 4 reference points in the xand y-dimensions was calculated. The difference between these 2 means was the change
Fixation in Le Fort I osteotomy
167
B Fig. 2. Fixation method used in patients; group I (N= 10); intermaxillary fixation with a wafer, intraosseous fixation only. of the position of the maxilla. The rotation was calculated as the change of the midline through the respective squares (Fig. 4). The method error of the superimposing technique has been studied by repeated registrations. 3 different methods for superimposing of the maxilla have been investigated. (1) Superimposition on the hard palate and the central incisors. (2) Superimposition on a posterior and an anterior intraosseous wire. (3) Superimposition on the hard palate and an anterior intraosseous wire. The accuracy of each of these 3 methods was decided by superimposing 5 pairs of randomly chosen lateral headfilms. The superimpositions were made by one person (USR) on 2 occasions and separated by at least 1 week. The error of the measurement was calculated with the formula cS=l/Xd2/2N , where d is the difference between the 2 registrations and N is the number of repeated registrations. The least difference between the 2 occasions was found using method (3). This method was analysed once more in a series of independent repeated superimpositions of 10 pairs of head films. The method error was less than 0.4 mm in the vertical and horizontal direction and less than 0.9 ° for rotation. This method was used in the continued study. Results
Intraosseous fixation only (group I, n = 10) and enhanced fixation (group II, n = 14) (Table 2) A t surgery, the maxilla was m o v e d alm o s t the same distance in b o t h groups. T h e a n t e r i o r m o v e m e n t was 5.6 m m in g r o u p I a n d 5.9 m m in g r o u p II a n d the
C
D
Fig. 3. Fixation methods used in patients; group II ( N - 1 4 ) ; intermaxillary IIA~ d wlth a wafer. Suspension wires (A) over the piriform aperture, (B) around the infraorbital crest and (C) around the zygomatic arch. Intraosseous fixation with bone plates (D). "
inferior m o v e m e n t was 2.0 m m a n d 1.2 m m , respectively. The maxilla was rotated d o w n w a r d s b a c k w a r d s 3.2 ° in g r o u p I a n d 2.9 ° in g r o u p II.
During the period immediately after surgery until release o f I M F 5 weeks later, a l m o s t n o h o r i z o n t a l change was seen in either group. In the vertical dimension, there was a significant difference between the groups. In g r o u p I, the vertical c h a n g e was 1.1 m m a n d in g r o u p II 0.2 mm.
During the period from release o f I M F until 12-24 months later, there was a m e a n h o r i z o n t a l relapse o f 1.0 m m posterior in g r o u p I a n d 0.6 m m in g r o u p
II. N o relapse of the vertical changes a n d r o t a t i o n s was observed. Discussion
The p a t i e n t s included in this study constitute a u n i f o r m g r o u p with similar diagnosis (maxillary retrusion) treated with the same surgical technique in the maxilla only, preceded by o r t h o d o n t i c treatment. F o r describing the change of maxillary position, the usual cephalometric points, pterygomaxillare (ptm) a n d a n t e r i o r nasal spine (sp), are n o t ideal as they are situated in the osteo t o m y area. D e n t a l points are likewise
168
R o n d a h l et al.
..-'...-
l
]
@®
(
(9
Q
,.--Q
A
,'-.',®
B
Fig. 4. Superimposition technique used for evaluation of changes in maxillary position in
pairs of lateral head films. (A) In the first film of each pair, 4 reference points were marked directly on the film. The 4 reference points were then transferred to the second film of the pair by superimposing on the anterior cranial base and then copied to a tracing film. (B) Superimposition on the maxilla. The 4 reference points were marked again on the same tracing film. The 8 reference points were used to calculate the change of position of the maxilla.
not suitable, as t o o t h movements are c o m m o n during the period of observation. Therefore, bone-structures outside the osteotomy area and steel liga-
tures were used for the superimposition. The method error was small. H o w ever, HOUSTON et al. 5 point out that one cannot be confident at the 5% level that
Table 2. Changes after Le Fort I osteotomy in 24 patients
Group I intraosseous wires only N=10 At surgery horizontal vertical rotation
x SD x SD x SD
Group II enhanced fixation; intraosseous and suspension wires N=14
5.6 2.6 -- 2.0 1.9 3.2 4.2
5.9 2.4 - 1.2 2.4 2.9 3.0
3-5 days postoperatively to release of IMF horizontal x 0.1 SD 1.0 vertical x l. 1 SD 1.2 rotation x --0.2 SD 1.0
- 0.1 0.8 0.2* 0.6 -0.1 1.0
From release of IMF to check up after 12-24 months horizontal x - i .0 SD 1.7 vertical x - 0.2 SD 1.0 rotation x 0.8 SD 1.6
-0.6 0.9 - 0.4 0.8 - 0.0 1.9
* P < 0.05.~
Horizontal changes measured in mm. A positive value indicates an anterior change, a negative a posterior change. Vertical changes measured in mm. A positive value indicates a superior change, a negative an inferior change. Changes in rotation measured in degrees. A positive value indicates a posterior rotation, a negative an anterior rotation.
changes in the individual reflect real changes, unless the differences are greater than twice the m e t h o d error for that measurement. This means that changes in the horizontal and vertical dimension in the present study less than 0.8 m m and rotations less than 1.8 ° should be interpreted with caution. The follow-up period was 12-24 months. During the fixation period, no horizontal changes were seen. A horizontal relapse was recorded between release o f I M F and the check-up after 12-24 months, which is in agreement with earlier observations by WILMAR7. During the fixation period, the vertical change in group I, with intraosseous fixation only, was 55% of the inferior replacement. A similar a m o u n t o f relapse is reported by WILMAR7, HEDEMARK & FREIHOFER4 and WOLrORD & HILLIARD8. BELL 8~ SCHEIDEMAN2 measured a vertical relapse of 30%. PERSSON et al. 6 reported a relapse of 20% when bone plates were used. The vertical change seen in group II, patients with enhanced fixation, was only 15% of the inferior replacement, which is less than earlier reported. During the period from release of I M F to the check-up 12-24 months later, no further vertical change was seen in either group, which is in agreement with studies by WILMAR7, BELL • SCHEIDEMAN2 and WOLFORD & HILLIARD8. In most patients, the maxilla was rotated downwards (posterior rotation) at the surgical advancement. The amount of rotation did not change during the fixation period. After release of IMF, there was even a small increase of rotation in some patients. This observation differs from the report m a d e by HEDEMARK & FREIHOFER4. Relapse after tipping of the maxilla forwards and downwards has also been reported by BUNDGARD et al. 3. The reason for the small changes during the fixation period in group II in the present study is probably the use o f suspension wires. These wires press the loosened maxilla and the bone grafts superiorly into a distinct vertical position. If the fixation consists ofintraosseous wires only, the relapse tendency is greater during the healing period. The maxilla and the mandible form a block by the intermaxillary fixation. The patient's efforts to open the m o u t h after surgery brings this rather mobile block downwards and backwards. Clinical factors such as how the patient is awakened after anesthesia are probably also important. The conclusion from this
Fixation in L e Fort I osteotomy study is t h a t a rigid vertical fixation is to be advocated.
References 1. Baamrind, S. & Miller, D. M.: Computeraided head film analysis: The University of California San Franscisco method. Am. J. Orthodont. 1980: 78: 41-65. 2. Bell, W. H. & Scheideman, G. B.: Correction of vertical maxillary deficency: stability and soft tissue changes. J. Oral Surg. 1981: 39: 666-670. 3. Bundgaard, M., Melsen, B. & Terp, S.:
Changes during and following total maxillary osteotomy/Le Fort I procedure): a cephalometric study. Europ J. Orthodont. 1986: 8: 21-29. 4. Hedemark, A. & Freihofer, H. P., Jr.: The behaviour of the maxilla in vertical movement after the Fort I osteotomy. J. Max. Fac. Surg. 1978: 6: 244-249. 5. Houston, W. J. B., Jones, E. & James, D. R.: A method of recording change in maxillary position following orthognathic surgery. Europ. J. Orthodont. 1987: 9: 9-14. 6. Persson, G., Hellem, S. & Nord, P. G.: Bone-plates for stabilizing Le Fort I oste-
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