The use of a LeFort I osteotomy to correct

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1 ORIGINAL ARTICLE LeFort I maxillary advancement: 3-year stability and risk factors for relapse Paul A. Dowling, a Lisen Espeland, b Leiv Sandvik, c Karim A. Mobarak, d and Hans Erik Hogevold e Dublin, Ireland, and Oslo, Norway Introduction: The objectives of this retrospective cephalometric study were to assess the amount, direction, and timing of postoperative changes after LeFort I maxillary advancement, and to identify risk factors for skeletal relapse. Methods: The material was selected from the files at the Department of Orthodontics, University of Oslo, and comprised 43 patients who underwent 1-piece LeFort I advancement as the only surgical procedure from 1990 to All patients were followed for 3 years by using a strict data collection protocol. Lateral cephalograms were obtained before surgery and at 5 times after surgery. Results: A mean relapse of 18% of the surgical advancement occurred. In 14% of the patients, clinically significant skeletal relapse ( 2 mm) was observed. Most (89%) postoperative change occurred during the first 6 months after surgery. Skeletal relapse increased significantly with degree of surgical advancement (P.001) and degree of inferior repositioning of the anterior maxilla (P.004) (linear regression analysis). At the end of follow-up, overjet and overbite were within clinically acceptable ranges for all patients. Conclusions: Maxillary advancement with a 1-piece LeFort I osteotomy is a relatively stable procedure. Identified risk factors for horizontal relapse were degree of surgical advancement and degree of inferior repositioning of anterior maxilla. (Am J Orthod Dentofacial Orthop 2005;128:560-7) The use of a LeFort I osteotomy to correct maxillary deformity was first described by Obwegeser in During the 1970s, the procedure became increasingly popular because it can be used to manage discrepancies in all 3 planes of space. 2,3 This versatility, in addition to few side effects, has made the LeFort I osteotomy the procedure of preference for the treatment of many skeletal Class III patients. Esthetic considerations have also contributed to the increasing use of this approach. 4 Long-term success of the surgical correction of dentofacial deformities depends largely on the stability of surgical movements. Most studies that have attempted to evaluate stability of LeFort I maxillary advancements have involved small samples, which are often mixed or heterogeneous in terms of the surgical a Senior lecturer/consultant, Department of Public and Child Dental Health, Trinity College, Dublin, Ireland. b Professor and Director of Postgraduate Study, Department of Orthodontics, University of Oslo, Oslo, Norway. c Professor of biostatistics, Faculty of Dentistry, University of Oslo, Oslo, Norway. d Clinical professor, Department of Orthodontics, University of Oslo, Oslo, Norway. e Chief surgeon, Department of Maxillofacial Surgery, Ullevaal University Hospital, Oslo, Norway. Reprint requests to: Lisen Espeland, Department of Orthodontics, Institute of Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, N-0317 Oslo, Norway; lisene@odont.uio.no. Submitted, April 2004; revised and accepted, July /$30.00 Copyright 2005 by the American Association of Orthodontists. doi: /j.ajodo procedures performed, and the follow-up period is frequently short. 5-8 Some studies have claimed excellent stability, 8 but others have reported significant postoperative changes. 5 Factors proposed as having an influence on stability include type of fixation, 9,10 amount of repositioning, 11 and use of bone grafts. 12,13 The aim of this study was to evaluate the long-term stability of the 1-piece LeFort I maxillary advancement. The objectives were to examine the amount, direction, and timescale of postoperative changes and to identify potential factors influencing skeletal stability. MATERIAL AND METHODS This study comprised 43 consecutively operated patients (22 male, 21 female) who underwent 1-piece LeFort I maxillary advancement osteotomy to correct a skeletal malocclusion problem. The patients were selected from the files at the Department of Orthodontics, University of Oslo. Surgery was performed at the Ullevaal University Hospital, Oslo, from 1990 to No additional surgical procedures were performed, and another criterion for inclusion was that the maxilla was advanced at least 2 mm. Patients with syndromes or cleft of the lip or palate were excluded from the study. All patients had been followed at the Department of Orthodontics, University of Oslo, over a 3-year period, and all had undergone preoperative and postoperative orthodontic treatment. Surgery was performed after growth had declined to adult levels. This evaluation was based on patient history, longitudinal clinical 560

2 American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 5 Dowling et al 561 Table I. Preoperative (T1) craniofacial and dental characteristics in 43 patients treated with surgical advancement of maxilla Mean SD Minimum Maximum SNA ( ) SNB ( ) ANB ( ) A to NP (mm) Pg to NP (mm) ML/NSL ( ) NL/NSL ( ) Overjet (mm) Overbite (mm) NP, Nasion perpendicular; NSL, nasion-sella line; ML, mandibular line (plane); NL, nasal line (maxillary plane). observations, and, in some cases, hand-wrist radiographs. Standardized cephalograms were collected according to a strict data-collection protocol. Ages at surgery varied from 16.2 to 53.0 years with a mean of 27.3 years. Table I summarizes some cephalometric variables describing preoperative craniofacial and dental morphology. A standard 1-piece LeFort I osteotomy was performed in all patients; 5 senior maxillofacial surgeons were involved. Before the surgical cuts, reference marks were made on the lateral aspects of the maxilla. After mobilization, the maxilla was moved to its planned position, by using the reference marks and the patient s occlusion as guides. Before maxillary fixation, the mandibular and maxillary arches were wired together. Fixation was achieved by using 2 L-shaped miniplates on each side of the maxilla. The plating system (Leibinger CMF Modular Wurzburg Stryker, Freiburg, Germany) consisted of 1.0-mm plates, and 4 screws (diameter, 2.0 mm) were used for each plate, 2 above and 2 below the surgical cut. After fixation, the interarch wiring was released, and the occlusion and the position of the condyles were checked. No patient received a bone graft, and no postoperative maxillomandibular fixation was used. If indicated, light elastics were applied after surgery to facilitate occlusal adjustments. In 6 patients, interocclusal splints were used to ensure optimal results; these were removable and kept in place for a short time postoperatively to provide a more stable position for each patient. Cephalograms were taken with the teeth in occlusion and the lips in a relaxed position. The same cephalostat was used for all radiographs. Magnification was 5.6%, which was not adjusted. The cephalograms were taken within a week before surgery (T1), within a week after surgery (T2), and at 4 different follow-up Fig 1. Skeletal and dental landmarks used in cephalometric analysis.. Fig 2. Diagram indicating mean surgical repositioning and mean relapse at 3 years at selected skeletal landmarks among 43 patients treated with surgical advancement of maxilla. Arrows indicate change as result of surgery, and arrowheads indicate change during 3-year follow-up period reviews: 2 months (T3), 6 months (T4), 1 year (T5), and 3 years (T6). The 2-month cephalogram was missing for 5 patients, the 6-month for 1 patient and the 1-year for 2 patients. All cephalograms were hand traced on acetate paper by the same examiner (P.A.D.). The tracings were scanned and digitized with the Quick Ceph Image 2000 software package (Quick Ceph Systems, San Diego,

3 562 Dowling et al American Journal of Orthodontics and Dentofacial Orthopedics November 2005 Table II. Error of method assessed from duplicate tracings of 25 radiographs Variable Dahlberg s calculation Houston s coefficient of reliability (%) Systematic error: t test (P value) Skeletal Horizontal (mm) A B * Pg * Vertical (mm) ANS PNS Me Angular ( ) SNA SNB ANB * NL/NSL ML/NSL * Dental Horizontal (mm) Is Ii * Vertical (mm) Is * Ii Incisor occlusion (mm) Overjet Overbite *Significant at 10% level (P.1). Calif). A custom analysis was used, and landmarks were digitized in sequence. A line through sella, rotated 7 from the nasion-sella line, was used as the horizontal reference line (x-axis). 14,15 This line approximates the Frankfort horizontal plane. The y-axis was perpendicular to the x-axis and passed through sella (Fig 1). A template of the outline of the maxilla, constructed by using the preoperative radiograph for each patient based on the outline of the bony palatal structures, was used for superimposing on subsequent radiographs to identify the location of maxillary landmarks. 16,17 This method of anatomic best fit was used to account for changes that might have resulted from surgical alteration of certain maxillary structures or postoperative bony remodeling. 8,18 These changes most commonly occur during LeFort I osteotomies at the anterior nasal spine (ANS). 9 Superimposition of sequential radiographs was carried out by using cranial-base structures including the cribriform plate and the anterior wall of sella turcica. 19 A surgical splint was present at T2 for 6 patients and also at T3 for 1 patient. To account for this, an autorotation of the mandible was performed with Quick Ceph Image 2000 around the midcondylar point until the dentition occluded. For analysis of method error, 25 radiographs, chosen at random, were traced and digitized by the same investigator (P.A.D.) on 2 separate occasions at least 2 weeks apart. Statistical analyses were performed with SPSS for Windows (SPSS, Chicago, Ill). Dahlberg s calculation and the coefficient of reliability proposed by Houston 20 were used to determine error between duplicate measurements. Systematic error was assessed by using paired t tests, with a 10% level of significance. A paired t test was used to analyze changes over time for cephalometric variables. Association between variables was analyzed by calculating Spearman correlation coefficients, and multivariate linear regression analysis was used to identify factors with possible influence on postoperative change in the anteroposterior position of maxilla. RESULTS The results from the method analysis are shown in Table II. For 6 of the 17 variables, the difference between duplicate measurements was significant at the 10% level: B-point to y-axis, pogonion to x-axis, ANB angle, ML/ NSL, mandibular incisor to x-axis, and maxillary incisor to y-axis. Mean changes in the cephalometric variables during the various time intervals are given in Table III. Figure 2 summarizes mean surgical repositioning and mean postoperative changes for selected skeletal variables at 3 years. The surgical advancements measured at A-point ranged from 2.2 to 10.0 mm with a mean value of 4.9 mm. In 27 patients (62.9%), the maxilla was advanced 4 mm or more, whereas, in 16 (37.2%), the surgical change was 2 to 4 mm. In the vertical plane, the surgical movement of the anterior maxilla measured at ANS ranged from 5.4

4 American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 5 Dowling et al 563 Table III. Mean changes and 1 standard deviation (SD, in parenthesis) in skeletal and dental variables during various time intervals T1 to T2 n 43 T2 to T3 n 38 T3 to T4 n 37 T4 to T5 n 40 T5 to T6 n 41 T2 to T6 n 43 Skeletal Horizontal (mm) (Negative value indicates posterior movement) A 4.9 (1.8) 0.4* (1.0) 0.4 (1.1) 0.2 (0.9) 0.0 (0.9) 0.9 (1.1) B 1.2* (3.4) 0.1 (1.3) 0.3 (1.3) 0.0 (1.2) 0.3 (1.6) 0.1 (2.4) Pg 1.4* (4.2) 0.2 (1.5) 0.4 (1.5) 0.1 (1.3) 0.4 (1.8) 0.2 (2.9) Vertical (mm) (Negative value indicates superior movement) ANS 1.1* (2.4) 0.3 (1.5) 0.4 (1.7) 0.3 (1.4) 0.2 (1.1) 0.8* (2.2) PNS 1.8 (3.3) 0.3* (0.9) 0.6* (0.8) 0.1 (1.1) 0.2 (0.9) 0.4* (1.4) Me 1.2* (3.4) 0.3 (1.0) 0.0 (0.9) 0.1 (0.8) 0.7 (0.9) 0.1 (2.1) Angular ( ) (Negative value indicates decrease) SNA 4.5 (1.8) 0.4* (1.0) 0.4 (1.1) 0.2 (0.9) 0.0 (0.9) 0.9 (1.1) SNB 0.5* (1.7) 0.0 (0.8) 0.2 (0.7) 0.0 (0.6) 0.1 (0.8) 0.0 (1.2) ANB 4.0 (2.3) 0.4* (1.0) 0.5 (1.0) 0.2 (0.8) 0.2 (0.7) 1.0 (1.3) NL/NSL 3.1 (3.4) 0.0 (1.7) 1.1 (1.9) 0.3 (2.1) 0.0 (1.3) 1.3 (2.1) ML/NSL 1.0* (2.8) 0.1 (1.1) 0.3 (1.0) 0.1 (0.9) 0.3* (0.9) 0.2 (1.8) Dental Horizontal (mm) (Negative value indicates posterior movement) Is 3.4 (2.9) 0.1 (1.0) 0.3 (1.2) 0.1 (0.9) 0.1 (0.9) 0.0 (1.5) Ii 0.7 (2.6) 0.2 (1.2) 0.0 (1.1) 0.1 (1.1) 0.3 (1.2) 0.6 (1.6) Vertical (mm) (Negative value indicates superior movement) Is 1.1* (2.7) 0.2 (1.3) 0.2 (1.0) 0.0 (0.8) 0.2 (0.8) 0.3 (2.0) Ii 1.6 (4.1) 0.7 (1.3) 0.2 (1.1) 0.1 (1.1) 0.6 (1.1) 0.4 (2.4) Incisor occlusion (Negative value indicates decrease) Overjet (mm) 2.7 (4.1) 0.0 (1.1) 0.3* (0.9) 0.0 (0.6) 0.2 (0.7) 0.6 (1.2) Overbite (mm) 2.7 (2.5) 0.5* (1.2) 0.0 (0.9) 0.1 (1.0) 0.3 (0.8) 0.2 (1.4) T1, within 1 week before surgery; T2, within 1 week after surgery; T3, 2 months after surgery; T4, 6 months after surgery; T5, 1 year after surgery; T6, 3 years after surgery. *.01 P.05;.001 P.01; P.001. mm in an inferior direction to 5.5 mm in a superior direction (mean, 1.1 mm inferiorly). The posterior maxilla measured at posterior nasal spine was repositioned 4.4 mm inferiorly to 6.8 mm superiorly (mean, 1.8 mm superiorly). A small but significant change in the position of the mandible (B-point, pogonion, menton) was observed as a secondary effect of surgery (P.05 for each variable) (Table III). Overjet and overbite both increased by an average of 2.7 mm (P.001). During the 3-year follow-up period (T2-T6), the mean horizontal change measured at A-point was 0.9 mm in a posterior direction (P.001), which represented 18.4% of the surgical movement. This change varied between patients and ranged from 1.9 mm in a further anterior direction to 3.2 mm in a posterior direction. Six patients (14%) had a change of more than 2 mm (Fig 3). Average relapse after 6 months was 0.8 mm as opposed to 0.9 mm after 3 years. Thus, 89% of the total postoperative change occurred during the first 6 months (Fig 4). The mean vertical postoperative change (T2-T6) of anterior maxilla measured at ANS was 0.8 mm in a superior direction (P.026). The posterior maxilla measured at PNS exhibited a mean inferior change of 0.4 mm (P.064). Overjet and overbite showed minimal changes during the postoperative period. Three years after surgery, mean overjet was 3.1 mm (SD 0.9), and mean overbite was 1.4 mm (SD 1.2). Risk factors for postoperative relapse The following 24 variables were analyzed as possible predictors for postoperative horizontal relapse of maxilla: Demographic characteristics: sex, age at operation Presurgery morphology (T1): SNA, SNB, ANB, A to NP, Pg to NP, NL/NSL, ML/NSL, overjet, overbite Surgical change (T1-T2): SNA, SNB, ANB, NL/NSL, ML/NSL, horizontal position of A, horizontal position of B, vertical position of ANS, vertical position of PNS, overjet, overbite Postsurgery morphology (T2): overjet, overbite

5 564 Dowling et al American Journal of Orthodontics and Dentofacial Orthopedics November 2005 Fig 3. Distribution of patients according to magnitude and direction of postoperative horizontal change at A-point. Fig 4. Mean horizontal change at A-point as function of time. Zero point on horizontal axis represents amount of surgical advancement measured within 1 week after surgery. Only 7 of these variables were significantly associated with horizontal relapse at A-point (Spearman correlation method, P.10) (Table IV). Because of strong intercorrelations, 4 variables were excluded from the multivariate regression analysis. Thus, only 3 variables were included in the regression model: overbite presurgery, surgical change in horizontal position of A-point, and surgical change in vertical position of ANS. In the regression model, all 3 variables were significantly related to horizontal relapse, and surgical advancement was more strongly related to the dependent variable than the other variables (Table V). This model explained 38% of the variation in horizontal relapse. To illustrate how 2 variables were related to horizontal relapse of maxilla, Table VI was constructed. Subgroups were established according to surgical advancement and surgical vertical change of anterior maxilla. The cutoff points defining the subgroups were chosen as the integer closest to the median value. The table indicates that the combination of surgical ad-

6 American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 5 Dowling et al 565 Table IV. Correlation between horizontal relapse at A-point (T2 to T6) and independent variables Spearman correlation P value Presurgical morphology SNB Overbite Surgical change SNA ANB NL/NSL Horizontal change at A Vertical change at ANS Table V. Horizontal relapse at A-point (T2 to T6) in relation to potential predictors Potential predictors Surgical advancement of maxilla measured at A: 1 mm increase Surgical vertical repositioning of anterior maxilla measured at ANS: 1 mm increase (more inferior) Presurgical overbite: 1 mm decrease Mean relapse (posterior movement) 95% confidence interval P value To improve readability, the signs ( / ) have been changed compared with signs in Tables III and IV. vancement of 4 mm or more and surgical change in vertical position of ANS of 2 mm or more in an inferior direction resulted in a horizontal relapse of 1.6 mm, as opposed to 0.2 mm when the surgical advancement was less than 4 mm and the surgical vertical change at ANS was in a superior direction or less than 2 mm in an inferior direction. DISCUSSION In patients requiring maxillary advancement, the repositioning of the maxilla must be considered in at least 2 planes of space and sometimes 3. The main focus of this study was to analyze the stability of anterior repositioning. The vertical repositioning varied because the patients had various malocclusions. Homogeneity of patients studied and surgical technique are fundamental for critical analysis of the multifactorial nature of postoperative change. 21 Our sample represented a homogenous group in terms of surgical repositioning. No additional procedures were carried out on any patient, lessening the risk of confounding the interpretation. In addition, adherence to a strict protocol for collection of follow-up radiographs allowed for a detailed analysis of the timescale of postoperative changes. When these patients underwent surgery, rigid internal fixation had been established as the routine method of fixation. Most earlier studies suggest that the use of rigid internal fixation improves the stability of maxillary procedures, 9,10,22 although some have not demonstrated significant differences between rigid and nonrigid methods in relapse of the anterior component of the surgical movement. 4,23 The number of patients included in the study was considered adequate. In retrospect, a power analysis was applied, focusing on the efficacy variable ie, the total postoperative horizontal relapse of the maxilla. In our study of 43 subjects, the estimated standard deviation of this variable was 1.1 mm. Assuming that the true standard deviation equals 1.1 mm and that a 2-sided 1-sample t test is used to analyze the observations with a 5% significance level, it can be shown that, if the true score of the variable is at least 0.5 mm, a study with 43 subjects will have at least 81% test power to detect an average score that is significantly different from zero. Thus, because 0.5 mm is relatively small compared with average total horizontal relapse of the maxilla (4.9 mm in our study), the test power of the study appears to be sufficiently high. Possible confounders in this study include the fact that surgery was performed by more than 1 surgeon. The 5 senior surgeons had been part of a team for several years and had established a standard surgical technique. Previous studies on maxillary surgery that considered this variable could not demonstrate an influence. 6,24 Some bias in mandibular measurements might be related to the presence of a splint in a few postsurgical radiographs, and inaccuracies might have been introduced as a result of using the center of the condyle when simulating rotation of the mandible. No specific information about duration of postsurgical orthodontic treatment was available. Thus, it was not possible to make any inferences about the possible role of active orthodontic appliances, such as intermaxillary elastics, on skeletal changes. Maxillary advancement in this study was generally stable. Only 6 of the 43 patients (14%) had more than 2 mm postoperative change horizontally; this is in the range that can be considered clinically significant. 25 This compares well with the study by Proffit et al 4 in which 20% of the patients had relapses greater than 2 mm a year postoperatively. Their study compared rigid and wire/maxillomandibular fixation methods, and no

7 566 Dowling et al American Journal of Orthodontics and Dentofacial Orthopedics November 2005 Table VI. Horizontal relapse at A-point (T2 to T6) according to magnitude of surgical advancement at A-point and surgical vertical repositioning of anterior maxilla measured at ANS (mean value and 1 SD) Surgical advancement (mm) measured at A Surgical vertical repositioning of anterior maxilla (mm) measured at ANS 4 mm advancement (n 16) 4 mm advancement (n 27) 2 mm inferior or superior movement 0.2 (0.6) 0.9 (0.7) (n 23) (n 10) (n 13) 2 mm inferior movement 0.9 (1.2) 1.6 (1.3) (n 20) (n 6) (n 14) To improve readability, signs ( / ) have been changed compared with signs in Tables III and IV. statistical significance was reported between the 2 groups. Almost half of the patients in both groups had autologous or homologous bone grafts. Comparison with most previous studies that examined postoperative stability of maxillary advancement procedures is difficult due to small sample sizes and heterogeneous groups that often included additional surgical procedures and bone grafting. In addition, different methods of fixation, differing methodologies, and variable periods of follow-up hinder comparisons. In our study, 89% of the horizontal relapse occurred during the first 6 months postoperatively; this was similar to other studies. 4,26,27 Accordingly, leaving orthodontic appliances in place for a few months after surgery is indicated to allow adjustment of the occlusion in response to any skeletal relapse. Although it has been shown that dissatisfaction with the outcome of surgical orthodontic treatment is related to prolonged postsurgical orthodontics, 28 the mean duration of this phase of treatment has previously been shown to be approximately 6 months. 29,30 In our sample, a positive overjet was observed at all follow-up stages, indicating that skeletal relapse was compensated for by dentoalveolar mechanisms. Because postsurgical change is likely to be a complex multifactorial phenomenon, regression analysis was used to identify the contribution of individual factors. The results showed that relapse was primarily influenced by magnitude of advancement. This contradicts the findings of Bothur et al, 23 but agrees with a study by Gurstein et al, 11 who reported that the magnitude of advancement influenced relapse especially in patients who did not receive a bone graft. From our findings, it could be argued that overcorrection should be considered in large advancements to counteract an anticipated relapse. On the other hand, because of individual variability, overcorrection can cause problems in stable patients. 31 Regression analysis suggested that large advancements combined with inferior repositioning of the anterior maxilla were susceptible to relapse. This might be explained by increased soft tissue stretching, 25 resulting in drift of the screws during bone healing. In addition, a reduced area of bone contact at the lateral aspects of the maxilla might compromise union of the bones. 13 No bone grafts were used in our patients. Bone grafts can act as a physical barrier and accelerate bone healing, 12 and thus might be considered in patients with large advancements combined with inferior repositioning of the anterior maxilla. From findings demonstrating increased stability for grafted patients, it has previously been suggested that bone grafting should be used when the advancement is greater than 6 mm. 5 Porous block hydroxyapatite has also been shown to be an effective alternative to bone for this purpose. 32 CONCLUSIONS Maxillary advancement with a 1-piece LeFort I osteotomy is a relatively stable procedure. On average, 18% of the horizontal maxillary repositioning was lost, and most of the change (89%) occurred during the first 6 months postoperatively. Relapse increased significantly with degree of surgical advancement and degree of inferior repositioning of anterior maxilla. REFERENCES 1. Obwegeser HL. Surgical correction of small or retrodisplaced maxillae. The dish-face deformity. Plast Reconstr Surg 1969; 43: Bell WH. Le Fort I osteotomy for correction of maxillary deformities. J Oral Surg 1975;33: Willmar K. On Le Fort I osteotomy; a follow-up study of 106 operated patients with maxillo-facial deformity. Scand J Plast Reconstr Surg. 1974;12(suppl 12): Proffit WR, Phillips C, Prewitt JW, Turvey TA. Stability after surgical-orthodontic correction of skeletal Class III malocclusion. 2. Maxillary advancement. Int J Adult Orthod Orthognath Surg 1991;6: Araujo A, Schendel SA, Wolford LM, Epker BN. Total maxillary advancement with and without bone grafting. J Oral Surg 1978;36:

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