CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY
Single Versus Segmental Maxillary Osteotomies and Long-Term Stability in Unilateral Cleft Lip and Palate Related Malocclusion Guy D. Watts, MBBS, PostGradDipSurgAnat, FRACS,* Gregory S. Antonarakis, DDS, MSc, PhD,y Christopher R. Forrest, MD, MSc, FRCSC, FACS,z Bryan D. Tompson, DDS, DOrthod, DPaedo, FRCD(C),x and John H. Phillips, MD, MSc, FRCSCk Purpose:
To investigate the stability of single-piece versus segmental (2-piece) maxillary advancement in patients with unilateral cleft lip and palate (UCLP) treated using conventional Le Fort I orthognathic surgery.
Patients and Methods:
A retrospective study was undertaken in 30 patients with nonsyndromic UCLP treated with the same surgical and orthodontic protocol from 2002 through 2011. Standard lateral cephalometric radiographs were taken preoperatively, immediately postoperatively, and at least 1 year postoperatively. Patients were divided into single-piece and segmental Le Fort I groups based on planned surgical movement. Postoperative movements were compared between groups using repeated measures analysis of variance.
Results:
The mean skeletal horizontal advancement was 7.3 and 7.5 mm in the single-piece and segmental groups, respectively. The skeletal horizontal relapse was 1.3 mm (18%) for the single-piece group and 1.9 mm (25%) for the segmental group. The skeletal surgical extrusion was 2.7 mm for the 2 groups. The skeletal vertical relapse was 0.6 mm (22%) and 1.5 mm (56%) for the single-piece and segmental groups, respectively. The mean dental horizontal postoperative movement was an advancement of 0.4 mm for the single-piece group and a relapse of 0.2 mm (3%) for the segmental group. The mean dental vertical relapse was 0.1 mm (4%) for the single-piece group and 0.3 mm (11%) for the segmental group. There was no statistically significant difference in relapse between the single-piece and segmental groups for all movements (P > .05).
Conclusion:
Skeletal and dental relapse was similar between single-piece and segmental maxillary advancements using conventional Le Fort I orthognathic surgery in patients with UCLP. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:2514-2521, 2014
*Clinical Fellow in Craniofacial Surgery, The Centre for
kAssociate Professor and Craniofacial Surgeon, The Centre for
Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto,
Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto,
Ontario, Canada.
Ontario, Canada.
yClinical Fellow in Craniofacial Orthodontics, Division of
Drs Watts and Antonarakis contributed equally to this work.
Orthodontics, Department of Dentistry, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Address correspondence and reprint requests to Dr Watts: The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario,
zProfessor, Head, and Craniofacial Surgeon, The Centre for
Canada, M5G 1X8; e-mail: [email protected]
Craniofacial Care and Research, Division of Plastic Surgery, The
Received February 9 2014
Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Ó 2014 American Association of Oral and Maxillofacial Surgeons
xAssociate Professor, Head, and Orthodontist, Division of Orthodontics, Department of Dentistry, The Hospital for Sick
Accepted July 10 2014 0278-2391/14/01160-4 http://dx.doi.org/10.1016/j.joms.2014.07.005
Children, University of Toronto, Toronto, Ontario, Canada.
2514
2515
WATTS ET AL
Segmental Le Fort I surgery is an integral tool in the management of occlusal and skeletal imbalances. Although it has been well investigated in the non-cleft literature, few studies have looked at the long-term stability of single versus segmental advancements in the cleft orthognathic surgical population. Moreover, studies investigating stability in cleft populations do not often look at a homogeneous group of patients with the same cleft phenotype managed with unified surgical and orthodontic treatment protocols. Posnick and Dagys1 and Heli€ ovaara et al2 emphasized the importance of a homogenous cleft population in validating and comparing cleft orthognathic surgical studies. Single-piece Le Fort I osteotomies allow control of the maxilla in sagittal, vertical, and rotatory positioning. Segmentation of the maxilla can enhance this control by addressing specific occlusal problems related to the cleft deformity. It can enable opening or closing of the cleft alveolar gap depending on the planned implant reconstruction, facilitate alveolar bone grafting, and close alveolar fistulas. It can widen the maxillary arch, allow differential movement of greater and lesser segments, align the occlusal plane, and maximize intercuspation to improve postoperative stability. The primary objective of the present investigation was to look at and compare long-term stability of skeletal and dental outcomes in single-piece and segmental advancements using conventional Le Fort I orthognathic surgical procedures in patients with nonsyndromic unilateral cleft lip and palate (UCLP).
Patients and Methods PATIENT SELECTION
A retrospective chart review was performed of all Le Fort I maxillary advancements in patients with UCLP at the Hospital for Sick Children (Toronto, Canada) from 2002 through 2011 and whose 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 previously underwent distraction osteogenesis; patients in whom initial cleft repair, orthodontics, or any other treatment was completed at another institution; patients who did not have secondary alveolar bone grafting (bone grafting at the time of the transitional dentition); patients who underwent orthognathic surgery with more than 2 maxillary segments; and patients without appropriate lateral cephalometric radiographs. Patients were grouped according to the surgical procedure into single-piece or segmental (2-piece) Le Fort I maxillary advancement groups. All patients underwent Le Fort I advancement with plate fixation. All
segmental osteotomies occurred through the cleft site in the alveolus. The segmental movement involved closure of the cleft alveolar gap or widening of the alveolar arch. All single-piece advancements did not require closure of the cleft alveolar space or widening of the alveolar arch. Fistula closure (if present) and bone grafting were performed simultaneously in segmental surgeries. All patients received bone grafts (27 from the iliac crest and 3 from the maxillary bone). Bone grafts were used at the Le Fort osteotomy site and the alveolar segment site. Cancellous bone was used primarily at the alveolar segment and a combination of cancellous and cortical bone was used at the Le Fort osteotomy site. Fixation of all patients was with 4- 2-mm plates. No separate plates were used across the alveolar segments in segmental surgery. Preoperative and postoperative orthodontic treatment was undertaken in all patients. Occlusal splints were used intraoperatively and left in situ for 6 to 8 weeks with guiding elastics where required. CEPHALOMETRIC ANALYSIS
Standard lateral cephalometric radiographs were taken for each patient immediately before surgery (T1), immediately (#1 week) after surgery (T2), and at a minimum of 12 months after surgery (T3). At 12 months after surgery, the maxilla is considered stable.3-5 One examiner traced all cephalograms with a digitizer connected to a computer using Dentofacial Planner 7.2 (Dentofacial Software, Toronto, Canada).6 The change of maxillary position between time points was assessed using superimposition of the anatomic best fit of the anterior cranial base parallel to the line between the sella and the nasion (SN) based on the sella.2 Preoperative tracings of the preoperative maxilla were superimposed on subsequent radiographs to assist in identification of anatomic landmarks.5 To measure skeletal and dental horizontal and vertical changes in the maxilla over time, an x and y coordinate system was established (Fig 1).1,2,7 The x axis was orientated along the SN and the y axis was orientated perpendicular to this line through the sella.6,8 Horizontal changes were measured as a distance along the x axis to the anatomic point. Vertical changes were measured along the y axis to the anatomic point.7 The skeletal anatomic point used for horizontal and vertical changes was the A point and the dental point was the mesiobuccal cusp of the upper first molar (left and right; Fig 1).9 If the patient was diagnosed with a left-sided UCLP, then the left molar measurement was designated the lesser segment and the right the greater segment and vice versa. Averaging left and right molar measurements produced mean dental movements. Other cephalometric skeletal outcomes measured were the angle formed by the
2516
SINGLE VERSUS SEGMENTAL MAXILLARY OSTEOTOMY
FIGURE 1. The x and y coordinate system used for measuring horizontal and vertical skeletal and dental outcome measurements. Skeletal changes were measured to the A point and dental changes to the mesiobuccal cusp of the first maxillary molar (left and right). A, A point (deepest point on the anterior contour of the maxillary alveolar arch); M1, mesiobuccal cusp first maxillary molar; N, nasion; S, sella. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
sella, nasion, and the A point (SNA), the angle formed by the SN to the palatal plane, and the distance from the condylion to the A point, representing effective midface length (Fig 2). Surgical movement was defined as the change from T1 to T2 and postoperative movement defined as the change from T2 to T3. The term relapse also is used in reference to a postoperative movement (T2 to T3) that occurs in the direction of T1. STATISTICAL ANALYSIS
All statistical analyses were carried out using SAS/ STAT 9.2 (SAS Institute, Cary, NC). 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 single and segmental Le Fort I maxillary advancement groups also were assessed using repeated measures analysis of variance. Statistical significance was set at a P value less than .05. ERROR OF THE METHOD
To assess the error of the method, 15 randomly selected lateral cephalometric radiographs were
retraced and re-digitized. Reliability was assessed using paired t tests10 and no significant differences were observed for any of the measurements (P > .05). Random error was assessed using the Dahlberg formula,11 which showed a maximum error of 0.9 mm and 1.1 .
Results Table 1 presents the baseline characteristics of the patient population. Thirty patients met the inclusion criteria for the study. Eleven patients underwent a single-piece Le Fort I maxillary advancement and 19 patients underwent segmental Le Fort I maxillary advancement. There were 7 male and 4 female patients in the single-piece group (n = 11) and 7 male and 12 female patients in the segmental group (n = 19). The average age of the single-piece group was 18.8 years (16.2 to 22.1 yr) and that of the segmental group was 17.8 years (15.6 to 22.4 yr). The average follow-up of the single-piece group was 1.7 years (1 to 4.7 yr) and that of the segmental group was 1.8 years (1 to 4.2 yr). All osteotomies were performed by 1 of 2 experienced orthognathic surgeons. There was no
2517
WATTS ET AL
FIGURE 2. Auxiliary skeletal outcome measurements. Measurements included the angle formed by the sella, nasion, and A point (SNA, angular); effective midface length (Co-A, linear); and the angle formed by the line between the sella and nasion to the palatal plane (angle between S-N and ANS-PNS). A, A point (deepest point on the anterior contour of the maxillary alveolar arch; ANS, anterior nasal spine; Co, condylion; N, nasion; PNS, posterior nasal spine; S, sella. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
statistically significant difference between the single and segmental groups for skeletal or dental measurements at T1 (P > .05). There was no statistically significant difference in postoperative movement associated with surgeon, gender, bone source (ileum vs maxilla), or 1- and 2-jaw surgery (P > .05). Therefore, the 2 study groups were considered homogenous for further investigation. Table 2 presents the mean skeletal and dental surgical changes (T1 to T2) for the single and segmental groups. The mean horizontal skeletal advancement for the single-piece group was 7.3 mm (1.5 to 10.9 mm) and that for the segmental group was 7.5 mm (1.5 to 14.1 mm). The mean skeletal extrusion was 2.7 mm for the 2 groups; the range for the single-piece group was 0.1 to 6.5 mm and that for the segmental group was 2.3 to 7.6 mm. The mean horizontal dental advancement for the single-piece group was 7.1 mm (0.3 to 9.7 mm) and that for the segmental group was 7.4 mm (1.6 to 14.1 mm). The mean dental extrusion for the single-piece group was 2.4 mm (0.4 to 6.4 mm) and that for the segmental group was 2.8 mm (1.7 to 5.3 mm). No statistically significant differences were found between skeletal and dental measurements for the single and segmental groups for surgical movement.
Dental movements were further analyzed to assess surgical and postoperative movements of the greater and lesser segments. Correlation between left and right molar measurements and a patients’ cleft side allows differentiation of greater and lesser segments. Greater and lesser segment dental surgical movements of the single-piece and segmental groups are presented in Table 3. There was no statistically significant difference for the dental surgical movement of the greater and lesser segments between the single and segmental groups. Table 4 presents the postoperative skeletal and dental movements (T2 to T3) of the single and segmental groups. The skeletal horizontal postoperative movement was 1.3 mm (2.3 to 0.9 mm) for the single piece group, 1.9 mm (3.6 to 0.4 mm) for the segmental group, and 1.6 mm overall. The skeletal vertical postoperative movement was 0.6 mm (2.4 to 2.2) for the single-piece group, 1.5 mm (4.7 to 0.5) for the segmental group, and 1.1 mm overall. There was a statistically significant postoperative movement in the segmental group for all skeletal outcome measurements and no statistically significant postoperative movement noted in the single-piece group. However, there was no statistically significant difference
2518
SINGLE VERSUS SEGMENTAL MAXILLARY OSTEOTOMY
Table 1. BASELINE CHARACTERISTICS OF THE STUDY POPULATION
Age (yr) Mean Range Follow-up (yr) Mean Range Gender Male Female Cleft type UCLP ABG VPI surgery SNA ANB Preoperative midface length (mm) Fistula Surgery Maxilla Maxilla + mandible Bone graft Source Ileum Maxilla
Single (n = 11)
Segmental (n = 19)
Total (N = 30)
18.8 16.2-22.1
17.8 15.6-22.4
18.3 15.6-22.4
1.7 1-4.7
1.8 1-4.2
1.8 1-4.7
7 4
7 12
14 16
11 11 3 75.4 3.6 88.8
19 19 2 74.2 3 87.9
30 30 5 74.8 3.3 88.4
2
4
6
5 6 11
9 10 19
14 16 30
10 1
17 2
27 3
Abbreviations: ABG, alveolar bone grafting; ANB, preoperative angle formed by the A point, nasion, and B point; SNA, preoperative angle formed by the sella, nasion, and A point; UCLP, unilateral cleft lip and palate; VPI, velopharyngeal incompetence. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
in postoperative movement when comparing the single and segmental groups. The mean horizontal dental postoperative movement was 0.4 mm (1.6 to 3.5 mm) for the single-piece group, 0.2 mm (3.5 to 4.1 mm) for the segmental group, and 0.1 mm overall. The mean vertical dental postoperative movement was 0.1 mm (1.9 to 1.4) for the single-piece group, 0.3 mm (2.9 to 1.2 mm) for the segmental group, and 0.1 mm overall. There was no statistically significant difference between the single and segmental groups for these dental outcome measurements. Considering the method error, there was essentially no dental postoperative movement in a horizontal or vertical direction. In the greater and lesser segmental analysis, there was no statistically significant postoperative movement of the greater or lesser segments for the singlepiece or segmental group (Table 5). There was no statistically significant difference in postoperative movement between the greater and lesser segments with intragroup and intergroup comparisons.
There were no major postoperative complications in patients in either study group. There were no documented postoperative infections or nonunions. One patient in the single-piece group had worsening of hypernasality postoperatively and required a revision pharyngoplasty.
Discussion Most of the cleft orthognathic surgical literature consists of mixed populations of patients with cleft of varying phenotypes. The present study presents a homogenous population of patients treated with a unified orthodontic and orthognathic treatment protocol with a study size similar to published stability studies. The authors acknowledge the retrospective nature of the investigation and the confounding factors associated with stability studies using cephalometric landmarks in patients with cleft. The present results indicate that skeletal relapse remains an ongoing factor in traditional cleft orthognathic surgery in single and segmental advancements. However, the authors found no statistical difference in skeletal postoperative movement between single and segmental advancements. They acknowledge a larger horizontal range of movement for the segmental group; however, there was no statistically significant difference in the amount of linear advancement between the groups. A larger study population might show a statistical difference in long-term stability between these groups. Vertical stability remains a more significant problem than horizontal stability in the cleft orthognathic population. The present horizontal and vertical stability rates are comparable to current published values for these 2 groups.12 In addition, there was no significant difference in dental postoperative movement between the greater and lesser segments of the cleft maxilla after orthognathic surgery. To the authors’ knowledge, this is the first time this has been reported in the literature. Dental outcomes indicate that postoperative orthodontics could compensate for skeletal postoperative movement in the single and segmental groups. There are few dedicated studies in the literature comparing single-piece with segmental (2-piece) advancements. Segmentation of the maxilla in orthognathic surgical patients with unilateral cleft is possible in several clinical scenarios. If secondary alveolar bone grafting (at the time of the transitional dentition) is not completed, then the greater and lesser segments are not unified. The cleft canine, if present, erupts within the lesser segment with decreased alveolar bone stock and there is distal tipping of the root of the canine to remain within the alveolus. Extraction of the bicuspid can create space for the canine, but the lesser segment tends to collapse in a palatal direction
2519
WATTS ET AL
Table 2. SURGICAL MOVEMENTS (IMMEDIATELY PREOPERATIVELY TO #1 WEEK POSTOPERATIVELY)
Single
SE
Range
P Value
Segmental
SE
Range
P Value
Comparison P Value
7.3 2.7 6 6.9 0.6
0.7 0.6 0.6 0.9 1.0
1.5 to 10.9 0.1 to 6.5 2.2 to 9.4 0 to 9.75 5.6 to 9.2
Single Versus Segmental Maxillary Osteotomies and Long-Term Stability in Unilateral Cleft Lip and Palate Related Malocclusion Guy D. Watts, MBBS, PostGradDipSurgAnat, FRACS,* Gregory S. Antonarakis, DDS, MSc, PhD,y Christopher R. Forrest, MD, MSc, FRCSC, FACS,z Bryan D. Tompson, DDS, DOrthod, DPaedo, FRCD(C),x and John H. Phillips, MD, MSc, FRCSCk Purpose:
To investigate the stability of single-piece versus segmental (2-piece) maxillary advancement in patients with unilateral cleft lip and palate (UCLP) treated using conventional Le Fort I orthognathic surgery.
Patients and Methods:
A retrospective study was undertaken in 30 patients with nonsyndromic UCLP treated with the same surgical and orthodontic protocol from 2002 through 2011. Standard lateral cephalometric radiographs were taken preoperatively, immediately postoperatively, and at least 1 year postoperatively. Patients were divided into single-piece and segmental Le Fort I groups based on planned surgical movement. Postoperative movements were compared between groups using repeated measures analysis of variance.
Results:
The mean skeletal horizontal advancement was 7.3 and 7.5 mm in the single-piece and segmental groups, respectively. The skeletal horizontal relapse was 1.3 mm (18%) for the single-piece group and 1.9 mm (25%) for the segmental group. The skeletal surgical extrusion was 2.7 mm for the 2 groups. The skeletal vertical relapse was 0.6 mm (22%) and 1.5 mm (56%) for the single-piece and segmental groups, respectively. The mean dental horizontal postoperative movement was an advancement of 0.4 mm for the single-piece group and a relapse of 0.2 mm (3%) for the segmental group. The mean dental vertical relapse was 0.1 mm (4%) for the single-piece group and 0.3 mm (11%) for the segmental group. There was no statistically significant difference in relapse between the single-piece and segmental groups for all movements (P > .05).
Conclusion:
Skeletal and dental relapse was similar between single-piece and segmental maxillary advancements using conventional Le Fort I orthognathic surgery in patients with UCLP. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:2514-2521, 2014
*Clinical Fellow in Craniofacial Surgery, The Centre for
kAssociate Professor and Craniofacial Surgeon, The Centre for
Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto,
Craniofacial Care and Research, Division of Plastic Surgery, The Hospital for Sick Children, University of Toronto, Toronto,
Ontario, Canada.
Ontario, Canada.
yClinical Fellow in Craniofacial Orthodontics, Division of
Drs Watts and Antonarakis contributed equally to this work.
Orthodontics, Department of Dentistry, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Address correspondence and reprint requests to Dr Watts: The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario,
zProfessor, Head, and Craniofacial Surgeon, The Centre for
Canada, M5G 1X8; e-mail: [email protected]
Craniofacial Care and Research, Division of Plastic Surgery, The
Received February 9 2014
Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Ó 2014 American Association of Oral and Maxillofacial Surgeons
xAssociate Professor, Head, and Orthodontist, Division of Orthodontics, Department of Dentistry, The Hospital for Sick
Accepted July 10 2014 0278-2391/14/01160-4 http://dx.doi.org/10.1016/j.joms.2014.07.005
Children, University of Toronto, Toronto, Ontario, Canada.
2514
2515
WATTS ET AL
Segmental Le Fort I surgery is an integral tool in the management of occlusal and skeletal imbalances. Although it has been well investigated in the non-cleft literature, few studies have looked at the long-term stability of single versus segmental advancements in the cleft orthognathic surgical population. Moreover, studies investigating stability in cleft populations do not often look at a homogeneous group of patients with the same cleft phenotype managed with unified surgical and orthodontic treatment protocols. Posnick and Dagys1 and Heli€ ovaara et al2 emphasized the importance of a homogenous cleft population in validating and comparing cleft orthognathic surgical studies. Single-piece Le Fort I osteotomies allow control of the maxilla in sagittal, vertical, and rotatory positioning. Segmentation of the maxilla can enhance this control by addressing specific occlusal problems related to the cleft deformity. It can enable opening or closing of the cleft alveolar gap depending on the planned implant reconstruction, facilitate alveolar bone grafting, and close alveolar fistulas. It can widen the maxillary arch, allow differential movement of greater and lesser segments, align the occlusal plane, and maximize intercuspation to improve postoperative stability. The primary objective of the present investigation was to look at and compare long-term stability of skeletal and dental outcomes in single-piece and segmental advancements using conventional Le Fort I orthognathic surgical procedures in patients with nonsyndromic unilateral cleft lip and palate (UCLP).
Patients and Methods PATIENT SELECTION
A retrospective chart review was performed of all Le Fort I maxillary advancements in patients with UCLP at the Hospital for Sick Children (Toronto, Canada) from 2002 through 2011 and whose 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 previously underwent distraction osteogenesis; patients in whom initial cleft repair, orthodontics, or any other treatment was completed at another institution; patients who did not have secondary alveolar bone grafting (bone grafting at the time of the transitional dentition); patients who underwent orthognathic surgery with more than 2 maxillary segments; and patients without appropriate lateral cephalometric radiographs. Patients were grouped according to the surgical procedure into single-piece or segmental (2-piece) Le Fort I maxillary advancement groups. All patients underwent Le Fort I advancement with plate fixation. All
segmental osteotomies occurred through the cleft site in the alveolus. The segmental movement involved closure of the cleft alveolar gap or widening of the alveolar arch. All single-piece advancements did not require closure of the cleft alveolar space or widening of the alveolar arch. Fistula closure (if present) and bone grafting were performed simultaneously in segmental surgeries. All patients received bone grafts (27 from the iliac crest and 3 from the maxillary bone). Bone grafts were used at the Le Fort osteotomy site and the alveolar segment site. Cancellous bone was used primarily at the alveolar segment and a combination of cancellous and cortical bone was used at the Le Fort osteotomy site. Fixation of all patients was with 4- 2-mm plates. No separate plates were used across the alveolar segments in segmental surgery. Preoperative and postoperative orthodontic treatment was undertaken in all patients. Occlusal splints were used intraoperatively and left in situ for 6 to 8 weeks with guiding elastics where required. CEPHALOMETRIC ANALYSIS
Standard lateral cephalometric radiographs were taken for each patient immediately before surgery (T1), immediately (#1 week) after surgery (T2), and at a minimum of 12 months after surgery (T3). At 12 months after surgery, the maxilla is considered stable.3-5 One examiner traced all cephalograms with a digitizer connected to a computer using Dentofacial Planner 7.2 (Dentofacial Software, Toronto, Canada).6 The change of maxillary position between time points was assessed using superimposition of the anatomic best fit of the anterior cranial base parallel to the line between the sella and the nasion (SN) based on the sella.2 Preoperative tracings of the preoperative maxilla were superimposed on subsequent radiographs to assist in identification of anatomic landmarks.5 To measure skeletal and dental horizontal and vertical changes in the maxilla over time, an x and y coordinate system was established (Fig 1).1,2,7 The x axis was orientated along the SN and the y axis was orientated perpendicular to this line through the sella.6,8 Horizontal changes were measured as a distance along the x axis to the anatomic point. Vertical changes were measured along the y axis to the anatomic point.7 The skeletal anatomic point used for horizontal and vertical changes was the A point and the dental point was the mesiobuccal cusp of the upper first molar (left and right; Fig 1).9 If the patient was diagnosed with a left-sided UCLP, then the left molar measurement was designated the lesser segment and the right the greater segment and vice versa. Averaging left and right molar measurements produced mean dental movements. Other cephalometric skeletal outcomes measured were the angle formed by the
2516
SINGLE VERSUS SEGMENTAL MAXILLARY OSTEOTOMY
FIGURE 1. The x and y coordinate system used for measuring horizontal and vertical skeletal and dental outcome measurements. Skeletal changes were measured to the A point and dental changes to the mesiobuccal cusp of the first maxillary molar (left and right). A, A point (deepest point on the anterior contour of the maxillary alveolar arch); M1, mesiobuccal cusp first maxillary molar; N, nasion; S, sella. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
sella, nasion, and the A point (SNA), the angle formed by the SN to the palatal plane, and the distance from the condylion to the A point, representing effective midface length (Fig 2). Surgical movement was defined as the change from T1 to T2 and postoperative movement defined as the change from T2 to T3. The term relapse also is used in reference to a postoperative movement (T2 to T3) that occurs in the direction of T1. STATISTICAL ANALYSIS
All statistical analyses were carried out using SAS/ STAT 9.2 (SAS Institute, Cary, NC). 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 single and segmental Le Fort I maxillary advancement groups also were assessed using repeated measures analysis of variance. Statistical significance was set at a P value less than .05. ERROR OF THE METHOD
To assess the error of the method, 15 randomly selected lateral cephalometric radiographs were
retraced and re-digitized. Reliability was assessed using paired t tests10 and no significant differences were observed for any of the measurements (P > .05). Random error was assessed using the Dahlberg formula,11 which showed a maximum error of 0.9 mm and 1.1 .
Results Table 1 presents the baseline characteristics of the patient population. Thirty patients met the inclusion criteria for the study. Eleven patients underwent a single-piece Le Fort I maxillary advancement and 19 patients underwent segmental Le Fort I maxillary advancement. There were 7 male and 4 female patients in the single-piece group (n = 11) and 7 male and 12 female patients in the segmental group (n = 19). The average age of the single-piece group was 18.8 years (16.2 to 22.1 yr) and that of the segmental group was 17.8 years (15.6 to 22.4 yr). The average follow-up of the single-piece group was 1.7 years (1 to 4.7 yr) and that of the segmental group was 1.8 years (1 to 4.2 yr). All osteotomies were performed by 1 of 2 experienced orthognathic surgeons. There was no
2517
WATTS ET AL
FIGURE 2. Auxiliary skeletal outcome measurements. Measurements included the angle formed by the sella, nasion, and A point (SNA, angular); effective midface length (Co-A, linear); and the angle formed by the line between the sella and nasion to the palatal plane (angle between S-N and ANS-PNS). A, A point (deepest point on the anterior contour of the maxillary alveolar arch; ANS, anterior nasal spine; Co, condylion; N, nasion; PNS, posterior nasal spine; S, sella. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
statistically significant difference between the single and segmental groups for skeletal or dental measurements at T1 (P > .05). There was no statistically significant difference in postoperative movement associated with surgeon, gender, bone source (ileum vs maxilla), or 1- and 2-jaw surgery (P > .05). Therefore, the 2 study groups were considered homogenous for further investigation. Table 2 presents the mean skeletal and dental surgical changes (T1 to T2) for the single and segmental groups. The mean horizontal skeletal advancement for the single-piece group was 7.3 mm (1.5 to 10.9 mm) and that for the segmental group was 7.5 mm (1.5 to 14.1 mm). The mean skeletal extrusion was 2.7 mm for the 2 groups; the range for the single-piece group was 0.1 to 6.5 mm and that for the segmental group was 2.3 to 7.6 mm. The mean horizontal dental advancement for the single-piece group was 7.1 mm (0.3 to 9.7 mm) and that for the segmental group was 7.4 mm (1.6 to 14.1 mm). The mean dental extrusion for the single-piece group was 2.4 mm (0.4 to 6.4 mm) and that for the segmental group was 2.8 mm (1.7 to 5.3 mm). No statistically significant differences were found between skeletal and dental measurements for the single and segmental groups for surgical movement.
Dental movements were further analyzed to assess surgical and postoperative movements of the greater and lesser segments. Correlation between left and right molar measurements and a patients’ cleft side allows differentiation of greater and lesser segments. Greater and lesser segment dental surgical movements of the single-piece and segmental groups are presented in Table 3. There was no statistically significant difference for the dental surgical movement of the greater and lesser segments between the single and segmental groups. Table 4 presents the postoperative skeletal and dental movements (T2 to T3) of the single and segmental groups. The skeletal horizontal postoperative movement was 1.3 mm (2.3 to 0.9 mm) for the single piece group, 1.9 mm (3.6 to 0.4 mm) for the segmental group, and 1.6 mm overall. The skeletal vertical postoperative movement was 0.6 mm (2.4 to 2.2) for the single-piece group, 1.5 mm (4.7 to 0.5) for the segmental group, and 1.1 mm overall. There was a statistically significant postoperative movement in the segmental group for all skeletal outcome measurements and no statistically significant postoperative movement noted in the single-piece group. However, there was no statistically significant difference
2518
SINGLE VERSUS SEGMENTAL MAXILLARY OSTEOTOMY
Table 1. BASELINE CHARACTERISTICS OF THE STUDY POPULATION
Age (yr) Mean Range Follow-up (yr) Mean Range Gender Male Female Cleft type UCLP ABG VPI surgery SNA ANB Preoperative midface length (mm) Fistula Surgery Maxilla Maxilla + mandible Bone graft Source Ileum Maxilla
Single (n = 11)
Segmental (n = 19)
Total (N = 30)
18.8 16.2-22.1
17.8 15.6-22.4
18.3 15.6-22.4
1.7 1-4.7
1.8 1-4.2
1.8 1-4.7
7 4
7 12
14 16
11 11 3 75.4 3.6 88.8
19 19 2 74.2 3 87.9
30 30 5 74.8 3.3 88.4
2
4
6
5 6 11
9 10 19
14 16 30
10 1
17 2
27 3
Abbreviations: ABG, alveolar bone grafting; ANB, preoperative angle formed by the A point, nasion, and B point; SNA, preoperative angle formed by the sella, nasion, and A point; UCLP, unilateral cleft lip and palate; VPI, velopharyngeal incompetence. Watts et al. Single Versus Segmental Maxillary Osteotomy. J Oral Maxillofac Surg 2014.
in postoperative movement when comparing the single and segmental groups. The mean horizontal dental postoperative movement was 0.4 mm (1.6 to 3.5 mm) for the single-piece group, 0.2 mm (3.5 to 4.1 mm) for the segmental group, and 0.1 mm overall. The mean vertical dental postoperative movement was 0.1 mm (1.9 to 1.4) for the single-piece group, 0.3 mm (2.9 to 1.2 mm) for the segmental group, and 0.1 mm overall. There was no statistically significant difference between the single and segmental groups for these dental outcome measurements. Considering the method error, there was essentially no dental postoperative movement in a horizontal or vertical direction. In the greater and lesser segmental analysis, there was no statistically significant postoperative movement of the greater or lesser segments for the singlepiece or segmental group (Table 5). There was no statistically significant difference in postoperative movement between the greater and lesser segments with intragroup and intergroup comparisons.
There were no major postoperative complications in patients in either study group. There were no documented postoperative infections or nonunions. One patient in the single-piece group had worsening of hypernasality postoperatively and required a revision pharyngoplasty.
Discussion Most of the cleft orthognathic surgical literature consists of mixed populations of patients with cleft of varying phenotypes. The present study presents a homogenous population of patients treated with a unified orthodontic and orthognathic treatment protocol with a study size similar to published stability studies. The authors acknowledge the retrospective nature of the investigation and the confounding factors associated with stability studies using cephalometric landmarks in patients with cleft. The present results indicate that skeletal relapse remains an ongoing factor in traditional cleft orthognathic surgery in single and segmental advancements. However, the authors found no statistical difference in skeletal postoperative movement between single and segmental advancements. They acknowledge a larger horizontal range of movement for the segmental group; however, there was no statistically significant difference in the amount of linear advancement between the groups. A larger study population might show a statistical difference in long-term stability between these groups. Vertical stability remains a more significant problem than horizontal stability in the cleft orthognathic population. The present horizontal and vertical stability rates are comparable to current published values for these 2 groups.12 In addition, there was no significant difference in dental postoperative movement between the greater and lesser segments of the cleft maxilla after orthognathic surgery. To the authors’ knowledge, this is the first time this has been reported in the literature. Dental outcomes indicate that postoperative orthodontics could compensate for skeletal postoperative movement in the single and segmental groups. There are few dedicated studies in the literature comparing single-piece with segmental (2-piece) advancements. Segmentation of the maxilla in orthognathic surgical patients with unilateral cleft is possible in several clinical scenarios. If secondary alveolar bone grafting (at the time of the transitional dentition) is not completed, then the greater and lesser segments are not unified. The cleft canine, if present, erupts within the lesser segment with decreased alveolar bone stock and there is distal tipping of the root of the canine to remain within the alveolus. Extraction of the bicuspid can create space for the canine, but the lesser segment tends to collapse in a palatal direction
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WATTS ET AL
Table 2. SURGICAL MOVEMENTS (IMMEDIATELY PREOPERATIVELY TO #1 WEEK POSTOPERATIVELY)
Single
SE
Range
P Value
Segmental
SE
Range
P Value
Comparison P Value
7.3 2.7 6 6.9 0.6
0.7 0.6 0.6 0.9 1.0
1.5 to 10.9 0.1 to 6.5 2.2 to 9.4 0 to 9.75 5.6 to 9.2
