The Cleft Palate–Craniofacial Journal 52(6) pp. 717–723 November 2015 Ó Copyright 2015 American Cleft Palate–Craniofacial Association

ORIGINAL ARTICLE Is Linear Advancement Related to Relapse in Unilateral Cleft Lip and Palate Orthognathic Surgery? Guy D. Watts,* M.B.B.S., F.R.A.C.S., Gregory S. Antonarakis,* D.D.S., M.Sc., Ph.D., Christopher R. Forrest, M.D., M.Sc., F.R.C.S.C., Bryan D. Tompson, D.D.S., D.Orthod., F.R.C.D.(C)., John H. Phillips, M.D., M.Sc., F.R.C.S.C. Objective: To investigate the stability of major versus minor Le Fort I maxillary advancements in unilateral cleft lip and palate (UCLP) patients. Design: A retrospective longitudinal study was undertaken on 30 nonsyndromic UCLP patients treated with the same protocol at The Hospital for Sick Children, Toronto, Canada. Patients were grouped into major and minor movement groups based on planned surgical advancement. Standard lateral cephalometric radiographs were taken preoperatively (T1), immediately postoperatively (T2), and at least 1 year postoperatively (T3). Skeletal and dental variables were measured using cephalometric analysis. Stability was compared between groups using repeated-measures analysis of variance. Linear regression analysis was used to assess the relationship between advancement and relapse for the entire study population. Results: A mean maxillary advancement of 9.8 mm and 4.9 mm was seen for the major (n ¼ 10) and minor (n ¼ 20) movement groups, respectively. The mean skeletal horizontal relapse was 1.8 mm (18%) for the major advancement group and 1.5 mm (31%) for the minor advancement group. There was no significant difference in skeletal horizontal relapse between the groups (P . .05). The correlation coefficient (r) between linear horizontal advancement and relapse was calculated to be .31 (P . .05). Dental horizontal relapse was not significant for either the major or minor groups, and no significant difference was found between the groups (P . .05). Conclusion: Skeletal and dental relapse was found to be unrelated to the amount of maxillary linear advancement using conventional Le Fort I osteotomies in UCLP. KEY WORDS:

cleft orthognathic surgery, Le Fort I osteotomy, maxillary advancements, relapse, UCLP

Postsurgical relapse rates following orthognathic surgery procedures in cleft lip and palate populations have been well studied over the years (Saltaji et al., 2012). In unilateral cleft lip and palate (UCLP) patients, relapse rates vary between 19% and 32% for horizontal movements and 19% and 52% for vertical movements (Garrison et al., 1987; Posnick and Ewing, 1990; Cheung et al., 1994; Posnick and Dagys, 1994; Heliovaara et al., 2001; Hirano and Suzuki, 2001; Thongdee and Samman, 2005; Daimaruya et al., 2010; Tables 1 and 2). Relapse rates following orthognathic surgery in cleft populations are significantly higher than in noncleft populations, and many contributing factors including palatal scarring, poor vascularity, soft tissue tension, presence of fistulas, and poor dentition have been associated with these increased rates (Hochban et al., 1993). Moreover, studies investigating stability in cleft populations do not often look at a homogeneous group of patients, with the same cleft phenotype (underlying diagnosis) and similar surgical and orthodontic treatment protocols. Both Posnick and Dagys (1994) and Heliovaara et al. (2001) emphasized the importance of a homogenous cleft population in validating and comparing cleft orthognathic surgery studies.

Dr. Watts is Fellow, Craniofacial Surgery, The Centre for Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Dr. Antonarakis is Fellow, Orthodontics, Division of Orthodontics, Department of Dentistry, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Dr. Forrest is Professor, Chair and Chief of the Division of Plastic and Reconstructive Surgery, and Medical Director of the HSC Centre for Craniofacial Care and Research, Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada, and Craniofacial Surgeon, The Centre for Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Dr. Tompson is Associate Professor and Head of Orthodontics, Division of Orthodontics, Department of Dentistry, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Dr. Phillips is Associate Professor and Craniofacial Surgeon, Division of Orthodontics, Department of Dentistry, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada. Presented at the International 15th biennial congress of the Society of Craniofacial Surgery, Jackson Hole, Wyoming, September 10–14, 2013. *These authors contributed equally to this work. Submitted April 2014; Revised July 2014; Accepted August 2014. Address correspondence to: Dr. Guy D. Watts, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada, M5G 1X8. E-mail [email protected]. DOI: 10.1597/14-061.1 717

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TABLE 1

Horizontal Relapse in Published UCLP Patients* Study

Sample Size (n)

Mean Surgical Advancement (mm)

Relapse (mm)

Percentage Relapse

Hirano and Suzuki (2001) Garrison et al. (1987) Heliovaara et al. (2001) Cheung et al. (1994) Thongdee and Samman (2005) Daimaruya et al. (2010) Posnick and Ewing (1990) Posnick and Dagys (1994)

42 15 40 17 30 7 5 35

? 2.9 3.9 4.2 5.6 5.8 6.4 6.9

? 0.6 0.8 1 1.8 1.6 1.6 1.6

19 21 21 22 32 28 25 23

* Studies are listed in order of mean surgical advancement.

Less well established is the relationship between the amount of surgical advancement and the degree of postoperative relapse. This is an important issue to clarify; if conventional orthognathic surgery produces less stable results in major maxillary advancements, then alternative surgical treatments such as distraction osteogenesis (DOG) should be advocated. Posnick and Ewing (1990) indicated that there was not a strong relationship between the amount of sagittal advancement and surgical relapse. Heliovaara et al. (2001), on the other hand, supported a relationship between the amount of surgical advancement and relapse. Interpretation of correlation coefficients (Table 3) by varying authors has further complicated the association between degree of advancement and relapse (Houston et al., 1989; Posnick and Ewing, 1990; Posnick and Dagys, 1994; Heliovaara et al., 2001; Hirano and Suzuki, 2001; Thongdee and Samman, 2005). However, of the published correlation coefficients, there is a trend toward a significant relationship between these two variables in studies with small overall mean advancements. Larger overall mean advancements show less correlation between the amount of advancement and relapse. To effectively study a relationship between these two variables, it is important to establish a major movement group. A number of surgeons are advocating DOG for cleft populations as opposed to conventional orthognathic surgery. Distraction osteogenesis is advocated for two main reasons: improved stability and larger advancements. At our institution, there has been a limited requirement for DOG both in terms of long-term stability or linear advancement, and most patients who require maxillary advancement are treated with conventional Le Fort I osteotomies following the completion of skeletal growth. The primary objective of the current investigation was to look at and compare long-term stability of major versus TABLE 2

minor horizontal skeletal advancements, using a cutoff point of 10-mm planned surgical advancement, in nonsyndromic UCLP patients treated with conventional Le Fort I orthognathic surgery procedures. The secondary objective was to look at other sagittal and vertical cephalometric variables, comparing patients who had undergone minor versus major maxillary advancements. METHODS Patient Selection A retrospective review of all Le Fort I maxillary advancements in cleft patients treated at our institution was undertaken to identify individuals with a diagnosis of complete UCLP who had their orthognathic surgery procedure completed between 2002 and 2011 and for whom complete diagnostic records were available. The study was approved by the hospital’s institutional review board. Patients were excluded for the following reasons: diagnosis other than complete UCLP; syndromic clefts; patients who had already undergone DOG; patients in whom initial cleft repair, bonegrafting procedures, orthodontics, or any other treatment was completed at another institution; and patients without appropriate or good-quality lateral cephalometric radiographs. Patients were grouped into major and minor surgical movements according to the magnitude of planned horizontal surgical movement. Those with planned movements 10 mm were allocated to the major advancement group, while those with planned movements ,10 mm were allocated to the minor advancement group. The cutoff point of 10 mm was selected based on the present common belief among surgeons

Vertical Relapse in Published UCLP Patients* Study

Sample Size (n)

Mean Vertical Movement (mm)

Relapse (mm)

Percentage Relapse

Posnick and Dagys (1994) Daimaruya et al. (2010) Cheung et al. (1994) Thongdee and Samman (2005) Heliovaara et al. (2001)

35 7 30 30 40

2.1 3.3 4.2 4.4 4.5

0.4 1.7 1 2.3 1

19 52 24 51 22

* Studies are listed in order of mean vertical movement.

Watts et al., LINEAR ADVANCEMENT AND RELAPSE IN UCLP ORTHOGNATHIC SURGERY

TABLE 3

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Published Correlation Coefficients Between Horizontal Advancement and Relapse in Cleft Lip and Palate Patients* Study

Heliovaara et al. (2001) Thongdee and Samman (2005) Posnick and Ewing (1990) Hirano and Suzuki (2001) Posnick and Dagys (1994) Houston et al. (1989)

Sample n n n n n n

¼ ¼ ¼ ¼ ¼ ¼

30; 30; 30; 71; 30; 30;

Mean Advancement (mm)

Correlation Coefficient (r)

Relationship (P , .05)

3.9 5.6 6.7 6.9 6.9 9

.36 .58 .33 .38 .31 .33

Yes Yes No Yes No No

UCLP Mixed UCLP Mixed UCLP Mixed

* Studies are listed in order of mean surgical advancement. UCLP indicates unilateral cleft lip and palate; mixed, population of unilateral and bilateral cleft lip and palate patients. Relationship indicates the authors’ comments with regard to an association between linear advancement and relapse, based on statistical significance (P , .05).

that movements of the magnitude of 10 mm can be achieved only by DOG. All patients underwent maxillary advancement with standard Le Fort I osteotomies with plate fixation (4 3 2.0 mm). The primary focus for the surgical technique was achievement of passive positioning of the maxilla intraoperatively. Overcorrection was not planned; however, the maxilla was advanced 2 mm beyond the required advancement and held under gentle, maintained traction. Prior to plating, the advanced maxilla sits passively into an oclussal splint. This technique assists in releasing the viscoelastic properties in the tissues and is considered a contributing factor in long-term stability. Preoperative and postoperative orthodontic treatment was undertaken in all patients. Occlusal splints were used intraoperatively and left in situ for 8 weeks postoperatively. No patients had intermaxillary fixation at the time of the operation, and all patients were bone grafted.

distance along the x-axis from a perpendicular line dropped from the SN plane to the anatomical point. Vertical changes were measured along the y-axis as the length of the line perpendicular to the SN plane to the anatomical point (Garrison et al., 1987). The skeletal anatomical point used for horizontal and vertical change was the A point, and the dental point was the mesiobuccal cusp of the maxillary first molar (left and right; Fig. 1; Macmillan and Tideman, 1994). Auxiliary cephalometric skeletal outcomes included sella-nasionA point (SNA), sella-nasion to palatal plane angle (SNPP), and condylion-A point representing the effective midface length (Fig. 1). Surgical movement was defined as the change between T1 and T2, and postoperative movement was defined as the change between T2 and T3. A positive sagittal movement correlated with maxillary advancement, and

Cephalometric Analysis Standard lateral cephalometric radiographs were taken for each patient immediately preoperatively (T1), immediately (within 1 week) postoperatively (T2), and at a minimum of 12 months postoperatively (T3). At 12 months postsurgery, the maxilla is considered stable (Houston et al., 1989; Posnick and Ewing, 1990; Ayliffe et al., 1995). One examiner traced and digitized the lateral cephalometric radiographs using Dentofacial Planner 7.2 (Bothur et al., 1998). The change in maxillary position between time points was assessed using superimposition of anatomic best fit at the anterior cranial base parallel to the sella-nasion (SN) plane based on sella (Heliovaara et al., 2001). Preoperative tracings of the preoperative maxilla were superimposed on subsequent radiographs to assist in identification of anatomical landmarks (Posnick and Ewing, 1990). To measure skeletal and dental horizontal and vertical changes in the maxilla over time, an x and y coordinate system was established (Fig. 1; Garrison et al., 1987; Posnick and Dagys, 1994; Heliovaara et al., 2001). The x-axis was orientated along the SN plane, and the y-axis was orientated perpendicular to this line through sella (Luyk and Ward-Booth, 1985; Bothur et al., 1998). Horizontal changes were measured as a

FIGURE 1 The x and y coordinate system and auxilliary outcomes used for skeletal and dental change. The x and y coordinate system established for horizontal and vertical skeletal and dental outcome measurements. Skeletal changes were measured to A point and dental changes to the mesiobuccal cusp of the first maxillary molar. S indicates sella; N, nasion; A, A point (deepest point on the anterior contour of the maxillary alveolar arch); M1, mesiobuccal cusp first maxillary molar. Auxiliary skeletal measures included sella-nasion-A point (SNA, angular), effective midface length (Co-A, linear), and sella-nasion to palatal plane (angle between S-N and ANS-PNS). Co indicates condylion; ANS, anterior nasal spine; PNS, posterior nasal spine.

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TABLE 4

Surgical Movements (T1 to T2)*

Skeletal Horizontal (mm) Vertical (mm) SNA (8) Midface length (mm) SN-PP (8) Dental Horizontal (mm) Vertical (mm)

Major

SE

Range

P Value

Minor

SE

Range

P Value

Comparison P Value

9.8 2.3 8.4 8.6 1.7

0.5 0.6 0.5 0.9 1.1

8 to 14.1 2.3 to 6.8 7.2 to 10.2 2.5 to 13.2 7.5 to 9.2

,.001 .005 ,.001 ,.001 .123

4.9 3.1 4.0 5.7 2.0

0.3 0.4 2 0.6 0.8

1.5 to 7.2 0.1 to 7.6 2.2 to 7.4 0 to 8.2 7.8 to 3.7

,.001 ,.001 ,.001 ,.001 .008

,.001 .095 ,.001 .019 .731

9.0 2.9

0.8 0.6

5.6 to 14.1 0 to 5.3

,.001 ,.001

5.5 2.5

0.5 0.4

0.3 to 7.9 1.7 to 6.4

,.001 ,.001

.002 .646

* Skeletal and dental sagittal and vertical surgical changes. The dental movements represent the average of the left and right molar measurements.

a positive vertical movement correlated with extrusion. Relapse was defined as a postoperative movement opposite to the surgical movement. Statistical Analysis All statistical analyses were carried out using SAS/ STAT software version 9.2. Descriptive statistics were calculated for surgical movements and for relapse. Differences between time points were assessed using repeated-measures analysis of variance. Differences between the major and minor groups were also assessed using repeated-measures analysis of variance. Linear regression analysis was also used to assess the presence of a correlation between amount of horizontal surgical advancement and stability within the whole patient sample. Statistical significance was set at the P , .05 level. Error of the Method To assess the error of the method, 15 randomly selected lateral cephalometric radiographs were retraced and redigitized. Reliability was assessed using paired t tests (Houston, 1983), and no significant differences were demonstrated for any of the measurements (P . .05). Random error was assessed using Dahlberg’s formula (Dahlberg, 1940), which demonstrated a maximum error of 0.9 mm and 1.18.

orthognathic surgeons. There was no statistically significant difference between major and minor groups for skeletal or dental measures at time point T1 (P . .05). There was no statistically significant difference in postoperative relapse associated with surgeon, sex, single or segmental maxilla, or one and two jaw surgeries (P . .05). The two study groups were therefore considered homogenous for further investigation. Table 4 demonstrates the mean skeletal and dental surgical changes (T1 to T2) for the major and minor groups. The mean surgical horizontal advancement for the major group was 9.8 mm (range, 8 to 14.1 mm) and for the minor group was 4.9 mm (range, 1.5 to 7.2 mm; Fig. 2). The mean vertical surgical movement was 2.3 mm (range, 2.3 to 6.8 mm) for the major group and 3.1 mm (range, 0.1 to 7.6 mm) for the minor group. The mean surgical horizontal dental movement for the major group was 9 mm (range, 5.6 to 14.1 mm) and for the minor group was 5.5 mm (range, 0.3 to 7.9 mm). The mean surgical vertical dental movement for the major group was 2.9 mm (range, 0 to 5.3 mm) and for the minor group was 2.5 mm range, (1.7 to 6.4 mm). The major and the minor groups demonstrated a statistically significant difference in surgical movements for all sagittal outcome measures. Table 5 demonstrates the postoperative skeletal and dental movements (T2 to T3) of the major and minor

RESULTS Thirty patients met the inclusion criteria for the study. Of the 30 patients, 10 had undergone major maxillary advancements, while the other 20 had undergone minor maxillary advancements. The average age of the major group was 18.7 years (range, 15.7 to 22.1 years) and for the minor group 18 years (range, 15.6 to 22.4 years). The mean follow-up for the major group was 1.6 years (range, 1 to 4.7 years) and 1.9 years (range, 1 to 3.9 years) for the minor. There was a mix of one (n ¼ 13) and two jaw surgeries (n ¼ 17). The Le Fort segments were bone grafted in all patients. All osteotomies were performed by one of two experienced

FIGURE 2 Surgical advancements. Plot diagram showing the measured cephalometric surgical advancement for each of the included patients. All patients above the marked line had a planned surgical advancement of 10 mm.

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TABLE 5

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Postoperative Movements (T2 to T3)* Major

SE

Range

P Value

Minor

SE

Skeletal Horizontal (mm) Vertical (mm) SNA (8) Midface length (mm) SN-PP (8)

1.8 0.5 1.8 2 1.7

0.5 0.6 0.5 0.9 1.1

3.6 2.4 5.1 5.3 3.1

0.9 2.2 0 0 6.4

.001 .402 .001 .031 .096

1.5 1.7 1.7 2.1 1

0.3 0.4 0.3 0.6 0.8

3.1 4.7 3.8 5.6 6.5

Dental Horizontal (mm) Vertical (mm)

0.3 0.1

0.8 0.6

1.9 to 1.8 2.9 to 1.4

.686 .892

0.4 0.4

0.5 0.4

to to to to to

Range

P Value

Comparison P Value

0.4 0.5 0.4 0.5 7.9

,.001 .003 ,.001 .001 .201

.569 .133 .845 .797 .529

3.5 to 4.1 1.9 to 1.1

.546 .367

.498 .681

to to to to to

* Skeletal and dental sagittal and vertical postoperative movement. A negative linear movement represents relapse.

groups. The mean postoperative skeletal horizontal movement was 1.8 mm (range, 3.6 to 0.9 mm) for the major group, 1.5 mm (range, 3.1 to 0.4 mm) for the minor group, and 1.7 mm overall. The mean postoperative skeletal vertical movement was 0.5 mm (range,2.4 to 2.2 mm) for the major group,1.7 mm (range,4.7 to 0.5 mm) for the minor group, and 1.1 mm overall. There was a statistically significant relapse in both the major and minor group but no statistically significant difference between the groups. The mean postoperative horizontal dental movement for the major group was 0.3 mm (range, 1.9 to 1.8 mm), the minor group had a further advancement of 0.4 mm (range, 3.5 to 4.1 mm), and there was overall 0.1 mm advancement. The mean postoperative vertical dental movement for the major group was 0.1 mm (range, 1.9 to 1.1 mm) and for the minor group was 0.4 mm (range, 2.9 to 1.2 mm), with an overall movement of 0.3 mm. Taking into consideration the method error, there was essentially no dental relapse in a horizontal or vertical direction. There was no statistically significant difference in relapse between the major and minor groups for the dental outcome measures. The correlation coefficient (r) between linear horizontal advancement and relapse was calculated to be .31 and did not demonstrate statistical significance (P . .05). DISCUSSION The present study suggests that relapse in the sagittal dimension, following Le Fort I maxillary advancement in nonsyndromic UCLP patients, is independent of the amount of advancement. Although relapse occurs following both major and minor advancements, there is no statistically significant difference in relapse between these two groups. Moreover, the correlation coefficient between linear advancement and relapse, and its lack of statistical significance, suggests that a linear relationship between the magnitude of horizontal maxillary advancement and relapse is unlikely. The relapse rates obtained fall within the published range from previous studies (Tables 1 and 2). The present study is unique as it represents the largest mean overall advancement for a UCLP stability study, namely, 7.4 mm. It also establishes two populations; a

major advancement group with a mean horizontal advancement of 9.8 mm (n ¼ 10) and a minor group with a mean horizontal advancement of 4.9 mm (n¼ 20). Similar to previously published studies, the measured cephalometric horizontal advancement was not always identical to the planned surgical advancement, which explains why the major advancement group did not contain only patients with a true advancement of 10 mm or more. Kumar et al. (2006) studied a severe deficiency group undergoing conventional orthognathic treatment. Their classification implied a required surgical movement of 10 mm, similar to the design of the present study; however, their actual mean cephalometric measured surgical movement was 7.2 mm (n¼ 11). Houston et al. (1989) published a series with a mean advancement of 9 mm (n ¼ 30), while Poole et al. (1986) published a series with 9.7 mm advancement (n ¼ 7), but these studies involved populations with a phenotypic mix of cleft patients and not solely patients with UCLP. Establishing a true and homogeneous major advancement group in the present study was the key to adequately investigating a relationship between the magnitude of surgical movement and relapse. Although there was a statistically significant relapse in sagittal movements in both major and minor advancement groups, this translates to linear and angular ranges of 1.5 to 1.8 mm (horizontal) and 1.78 to 1.88 (SNA), respectively. Clinically, these relapses were not significant, as postoperative orthodontic treatment was able to compensate for these skeletal changes. This is reflected in the dental cephalometric outcomes. In our study, the skeletal horizontal relapse in the minor advancement group was 1.5 mm versus 1.8 mm in the major advancement group. Thus, in absolute terms, there was a larger relapse, although insignificant, in the major advancement group. However, when one considers the percentage of relapse, the minor advancement group showed a 31% relapse versus an 18% relapse for the major advancement group. From a percentage perspective, the minor advancement group therefore showed more relapse than the major advancement group, albeit insignificant. The horizontal relapse rate of 31% for the minor advancement group is on the upper end of the published horizontal relapse rates for UCLP stability studies (Table

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1). We do not feel, however, that this was a significant factor in our results, as this percentage translates to 1.5 mm relapse (Table 5). High relapse rates in small movements are well documented in the literature, and many of the largest relapse rates are seen in the smallest movements (Ayliffe et al., 1995). Cheung et al. (1994) found that with movements of 5 mm, relapse rates varied from 0% to 150%, while with movements .5 mm, relapse rates varied from 0% to 58%. In assessing vertical relapse, the overall mean vertical relapse rate of 41% was within the range of published literature (Table 2). The larger mean extrusion of the minor group (3.1 mm) may have been a contributing factor to the slightly higher mean horizontal relapse of the minor group. There was, however, no significant difference noted in vertical relapse between the two groups (Table 5). The influence of skeletal relapse is twofold, resulting in suboptimal esthetic outcomes of skeletal harmony (class III skeletal relationship) and relapse of occlusal outcomes (class III dental relationship). In our study, conventional orthognathic surgery resulted in a horizontal dental postoperative relapse of 0.3 mm in the major advancement group and a postoperative forward movement of 0.4 mm in the minor advancement group. Considering the method error, there was essentially no relapse in occlusion in either group. Postoperative orthodontics and good intercuspidation are keys to such outcomes (Hochban et al., 1993). Clinical experience tells us that dental compensations are possible for 2 mm of linear relapse and 28 of angular relapse (Proffit et al., 2007). Thus, in our study, although there was some skeletal relapse, good occlusal relationships were maintained. Distraction osteogenesis is gradually finding its niche in orthognathic surgery. Proponents of this technique maintain that with traditional orthognathic surgical procedures, large movements lack stability. It is claimed that DOG provides an advantage both in regard to the amount of surgical advancement as well as long-term stability. Many authors have published different ranges of achievable maxillary advancement with conventional Le Fort I orthognathic surgery. Cheung et al. (2006) indicated that most surgeons accept that greater than 10 mm is beyond the present limit of cleft orthognathic surgery and can be achieved only by DOG. A number of surgeons, however, are using DOG as first-line treatment for cleft maxillary advancements and routinely in advancement less than 10 mm (Chua et al., 2010; Daimaruya et al., 2010). The range of major orthognathic advancements in our study was 8 to 14.1 mm. The data indicates that there is no significant difference in long-term stability between major and minor advancements. In our clinical practice, if a pure maxillary horizontal advancement is required, we will plan singlejaw surgery for 0 to 18 mm of advancement. For movements of 18 mm, one senior surgeon uses a staged advancement. The first-stage procedure advances the maxilla as far as possible, followed by a second

stage 3 to 6 months later to complete the advancement (with or without a mandibular procedure). The second senior author will use DOG for advancements greater than 18 mm. Large advancements are achievable, where even in the earliest descriptions of Le Fort I osteotomies, movements of greater than 20 mm are described (Converse and Shapiro, 1952). Currently, there are limited long-term studies looking at the stability of DOG in patients with clefts and no dedicated studies looking specifically at UCLP populations. Published rates of postoperative horizontal relapse of DOG in mixed cleft populations vary between 2% and 24% (with advancements ranging from 6.6 to 16.5 mm) depending on whether internal or external distraction devices are used (Kumar et al., 2006; Baek et al., 2007; Chua et al., 2010). A number of authors have demonstrated results with ongoing advancement of the maxilla post-DOG to an unpredictable degree (Cheung et al., 2006). Vertical relapse with DOG demonstrates a very broad picture in the postoperative period. Baek et al. (2007) demonstrated a relapse rate in a vertical direction postextrusion of 12%. Cheung et al. (2006) indicated a further extrusion of 25% of the initial extrusion, and Chua et al. (2010) demonstrated a further extrusion of 210% of the mean vertical extrusion at year 5 post-DOG. If the definition of stability is for the maxilla to remain in its operated position, then the current evidence for DOG remains limited. Current literature therefore demonstrates a potential for postoperative relapse with both conventional orthognathic surgery and DOG. In our experience, there are very limited indications for DOG in the UCLP population, and only a limited number of patients are judged to benefit from DOG for reasons other than magnitude of advancement or stability. Moreover, in previous cases of DOG treated at our institution, a high proportion required a subsequent conventional orthognathic surgical procedure to achieve final optimal occlusion. The bony regenerate produced by DOG also made repeat osteotomies more challenging compared with nondistracted bone. In our experience, conventional orthognathic surgery is easier, more precise, more predictable, and better tolerated by the patients than DOG. CONCLUSION The results of the present study demonstrate that in a homogeneous nonsyndromic UCLP population, where major (average 9.8 mm) surgical advancements of the maxilla were compared with minor (average 4.9 mm) surgical advancements, no significant differences were present with regard to relapse. Large advancements are thus routinely achievable and predictable with conventional orthognathic surgery procedures. The major determining factor in skeletal stability is not related to the amount of linear advancement.

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