Barry Grayson
NYU School of Medicine, Plastic Surgery, Faculty Member
The role of preoperative planning, the geometric changes, and the long-term effects of mandibular distraction have not been previously reported. This study included 10 patients who underwent unilateral (5 patients) or bilateral (5... more
The role of preoperative planning, the geometric changes, and the long-term effects of mandibular distraction have not been previously reported. This study included 10 patients who underwent unilateral (5 patients) or bilateral (5 patients) mandibular distraction. Preoperative, postdistraction, and yearly radiographs (panoramic, posteroanterior, and lateral cephalograms) were reviewed. Postdistraction follow-up ranged from 12 to 70 months. Postdistraction, the mandibles showed evidence of anticipated growth without relapse. This growth rate was variable and dependent on the genetic program of the native bone. Previously reported improvement in temporomandibular joint morphology was maintained in the long term. The resulting shape of the neomandible was most influenced by the vector of placement of the distraction device. When placed vertically, ramal elongation was observed. When placed horizontally, anterior projection of the mandibular body occurred. When placed obliquely, ramal and body elongation occurred with preservation of the gonial angle. After 2 to 5 years of follow-up, continued growth of the neomandible was observed.
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The purpose of this study was to investigate the relationship between soft-tissue and underlying skeletal structures before and after unilateral mandibular distraction osteogenesis. The sample consisted of 11 patients (three girls and... more
The purpose of this study was to investigate the relationship between soft-tissue and underlying skeletal structures before and after unilateral mandibular distraction osteogenesis. The sample consisted of 11 patients (three girls and eight boys) with an average age of 4.6 years at the time of treatment. All patients had unilateral craniofacial microsomia (four right-sided and seven left-sided unilateral craniofacial microsomia) and all underwent unilateral mandibular distraction osteogenesis. Measurements were performed on frontal medical photographs and posteroanterior cephalograms at predistraction (time 1) and postdistraction (time 2) periods. Left and right ramus heights, skeletal midline deviation, and transverse occlusal plane were measured on the posteroanterior cephalograms and compared with the linear distances between the lip commissures and the orbital plane, the circumference of both sides of the faces, and the angulation of the oral commissure plane as recorded on the ...
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The principle objective of presurgical nasoalveolar molding (NAM) is to reduce the severity of the initial cleft deformity. This enables the surgeon and the patient to enjoy the benefits associated with a repair of a cleft deformity that... more
The principle objective of presurgical nasoalveolar molding (NAM) is to reduce the severity of the initial cleft deformity. This enables the surgeon and the patient to enjoy the benefits associated with a repair of a cleft deformity that is of minimal severity. Retraction of the premaxilla, presurgical elongation of the columella, correction of the nasal cartilage deformity, alignment of the cleft alveolar segments, increase in the surface area of the nasal mucosal lining, up-righting of the columella, and achieving close approximation of the cleft lip segments at rest result from gentle application of forces through the NAM appliance. Preservation of these presurgical changes is achieved through the coordinated and modified surgical technique of the primary cleft repair.
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Extracts of the herb St John's Wort have been shown to reduce alcohol intake in alcohol-preferring rats, but it is not known which of the constituent(s) are responsible for this effect. In this study, the effect of a crude... more
Extracts of the herb St John's Wort have been shown to reduce alcohol intake in alcohol-preferring rats, but it is not known which of the constituent(s) are responsible for this effect. In this study, the effect of a crude methanolic extract of Hypericum perforatum (negligible hyperforin content) on alcohol drinking in C57BL/6J alcohol-preferring mice was compared with that of a hyperforin-rich extract (45% hyperforin) prepared by extracting the herb with supercritical carbon dioxide. The dose of the hyperforin-rich extract required to significantly reduce 10% ethanol intake (5 mg/kg) was 125-fold less than that required for the crude extract (625 mg/kg), and was comparable to the dose of fluoxetine (10 mg/kg) required to produce a similar effect. None of these agents significantly affected water intake. These results suggest that the effects of H. perforatum extracts on alcohol drinking behaviour are due to the hyperforin content of the herb rather than to other, more polar constituents. Hyperforin is an unstable compound and this study also highlights the effect of different methods of extract preparation on hyperforin content.
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The role of preoperative planning, the geometric changes, and the long-term effects of mandibular distraction have not been previously reported. This study included 10 patients who underwent unilateral (5 patients) or bilateral (5... more
The role of preoperative planning, the geometric changes, and the long-term effects of mandibular distraction have not been previously reported. This study included 10 patients who underwent unilateral (5 patients) or bilateral (5 patients) mandibular distraction. Preoperative, postdistraction, and yearly radiographs (panoramic, posteroanterior, and lateral cephalograms) were reviewed. Postdistraction follow-up ranged from 12 to 70 months. Postdistraction, the mandibles showed evidence of anticipated growth without relapse. This growth rate was variable and dependent on the genetic program of the native bone. Previously reported improvement in temporomandibular joint morphology was maintained in the long term. The resulting shape of the neomandible was most influenced by the vector of placement of the distraction device. When placed vertically, ramal elongation was observed. When placed horizontally, anterior projection of the mandibular body occurred. When placed obliquely, ramal and body elongation occurred with preservation of the gonial angle. After 2 to 5 years of follow-up, continued growth of the neomandible was observed.
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Midface hypoplasia, often associated with exorbitism and malocclusion, has been traditionally corrected by using Le Fort advancement osteotomies through wide surgical exposure. These procedures suffer the disadvantages of hemorrhage,... more
Midface hypoplasia, often associated with exorbitism and malocclusion, has been traditionally corrected by using Le Fort advancement osteotomies through wide surgical exposure. These procedures suffer the disadvantages of hemorrhage, unpredictable bone graft resorption, the need for retained hardware, and bone graft donor-site morbidity. We present an investigation of midface distraction in the canine without osteotomies. Five canines were the subjects of this study and were divided into two groups. At the time of placement of the lengthening devices, Group 1 animals were 10 weeks of age and Group 2 animals were 5 years of age. Under general anesthesia, four modified Hoffman bone distractors were mounted on 2-mm half pins placed individually across the nasofrontal and the zygomaticotemporal sutures on each side of the craniofacial skeleton. Distraction of all devices was begun on postoperative day 1 at the rate of 0.5 mm/day for 4 days and then 1.0 mm/day for 28 days, after which interval the devices were removed. The dogs were serially monitored and examined for 3 months. One dog in the first group served as a sham control. The results were assessed by standardized cephalograms, and craniofacial computed tomographic scans with three-dimensional reconstruction performed before device placement as well as after removal of the device. In one Group 1 animal, computed tomographic scanning was performed every 2 to 4 weeks for 3 months. Gross examination of the Group 1 animals demonstrated the development of enophthalmos, dolichocephaly, and a class II malocclusion-overbite.(ABSTRACT TRUNCATED AT 250 WORDS)
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The purpose of this study was to compare clinical outcomes and 1-year postsurgical stability with three different techniques of Le Fort III midface advancement. The records of 212 syndromic craniosynostosis patients were reviewed from the... more
The purpose of this study was to compare clinical outcomes and 1-year postsurgical stability with three different techniques of Le Fort III midface advancement. The records of 212 syndromic craniosynostosis patients were reviewed from the period 1973 to 2006. A total of 60 patients satisfied the inclusion criteria, and the mean age of the sample at surgery was 6.2 years. In group I (1977 to 1987), fixation was performed by interosseous wiring and intermaxillary fixation; in group II (1987 to 1996), fixation was achieved by only rigid plate fixation; and in group III (2000 to 2005), the patients underwent midface distraction with the rigid external distraction device. Cephalometric landmarks were identified and digitized at each of the time intervals (preoperatively, postoperatively, and 1 year postoperatively). The mean advancement measured at point A in group I averaged 9.7 mm; in group II, it was 10.6 mm; and in group 3, it was 16.1 mm. There was no statistically significant difference in the amount of advancement between groups I and II. However, when groups I and II were compared with group III, there was a statistically significant difference (p < 0.05). No statistical significance was noted within and between all three groups at 1-year follow-up. Significantly larger midface advancement was achieved with rigid external distraction (group III) compared with classic Le Fort III midface advancement with wire (group I) or plate (group III) fixation. At 1 year after surgery, the three groups showed relative stability of the advanced midface segment.
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A prospective clinical and cephalometric study was conducted on 12 patients under the age of 12 years undergoing Le Fort III advancement with the following findings: 1. There was a remarkable degree of postoperative skeletal stability of... more
A prospective clinical and cephalometric study was conducted on 12 patients under the age of 12 years undergoing Le Fort III advancement with the following findings: 1. There was a remarkable degree of postoperative skeletal stability of the midfacial segment. 2. Disharmony in jaw relationship (anterior crossbite) observed during the period of longitudinal postoperative study could be attributed to expected mandibular development. 3. In some patients, growth and development of the maxilla in a forward and downward direction were documented after Le Fort III advancement. The authors recommend that a Le Fort III advancement can be safely performed at approximately age 4 without a deleterious effect on midfacial development in the patient with craniofacial dysostosis.
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The desire to apply the scientific method to aesthetic facial surgery is the underpinning of this article, which summarizes the attempts that have been made to apply numeric methods to facial surgery, with particular emphasis on computer... more
The desire to apply the scientific method to aesthetic facial surgery is the underpinning of this article, which summarizes the attempts that have been made to apply numeric methods to facial surgery, with particular emphasis on computer methods.
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Research Interests: Cleft Palate, Adolescent, Cephalometry, Humans, Child, and 10 moreFemale, Skull, Male, Infant, Mandible, Maxilla, Middle Aged, Adult, Cleft Lip, and Facial Bones
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As in traditional combined surgical and orthodontic procedures, the orthodontist has a role in the planning and orthodontic support of patients undergoing distraction osteogenesis. This role includes predistraction assessment of the... more
As in traditional combined surgical and orthodontic procedures, the orthodontist has a role in the planning and orthodontic support of patients undergoing distraction osteogenesis. This role includes predistraction assessment of the craniofacial skeleton and occlusal function in addition to planning both the predistraction and postdistraction orthodontic care. Based on careful clinical evaluation, dental study models, photographic analysis, cephalometric evaluation, and evaluation of three-dimensional computed tomographic scans, the orthodontist, in collaboration with the surgeon, plans distraction device placement and the predicted vectors of distraction. Both surgeon and orthodontist closely monitor the patient during the active distraction phase, using intermaxillary elastic traction, sometimes combined with guide planes, bite plates, and stabilization arches, to mold the newly formed bone (regenerate) while optimizing the developing occlusion. Postdistraction change caused by re...
Research Interests: Bone Regeneration, Bone graft, Distraction Osteogenesis, Humans, Child, and 17 moreMale, Malocclusion, Mandible, Maxilla, Recurrence, Patient Care Team, Three Dimensional, Osteogenesis distraction, Jaw Fixation Techniques, Facial Asymmetry, Soft Tissue, Treatment planning, Function Space, Syndrome, External Fixators, Clinical evaluation, and Biomechanical Phenomena
A three-dimensional, multiplane cephalometric analysis is presented. This analysis permits visualization of skeletal midlines at selected depths of the craniofacial complex. When the midlines and associated anatomic structures are studied... more
A three-dimensional, multiplane cephalometric analysis is presented. This analysis permits visualization of skeletal midlines at selected depths of the craniofacial complex. When the midlines and associated anatomic structures are studied sequentially, the individual midlines may be combined conceptually into a warped midsagittal "plane." This localizes craniofacial asymmetry in the posteroanterior and basilar views. The study of structures in various coronal and transverse planes makes it possible to measure and record the three-dimensional relationships of anatomic structures to one another. A case of hemicraniofacial microsomia in which this analysis was used is presented.
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This article presents a method of cephalometric tracing and analysis using the basilar view cephalogram and discusses its role in diagnosis and treatment planning. Landmarks and structures found in each of three separate basilar planes... more
This article presents a method of cephalometric tracing and analysis using the basilar view cephalogram and discusses its role in diagnosis and treatment planning. Landmarks and structures found in each of three separate basilar planes are defined and instructions for tracings are presented. The analysis is applied to the study of orbital hypertelorism, craniofacial synostosis, and hemicraniofacial microsomia. The multiplane tracing technique is demonstrated to provide a three-dimensional concept of deformities in the craniofacial skeleton. A method to determine an anteroposterior midline construct from structures in the cranial base is described. As is practiced with the lateral cephalogram, presurgical tracings of the basilar film may be manipulated to simulate the skeletal changes anticipated in surgery.
Research Interests: Dentistry, Biomedical Engineering, Face, Cephalometry, Humans, and 6 moreSkull, Mandible, Maxilla, Facial Asymmetry, Facial Bones, and Orbit
The lower border of the mandible in mandibulofacial dysostosis is characteristic of the syndrome. Evaluation of the cephalograms by means of the medial axis analysis and inflectional tangents captures the shape deformity. Morphometric... more
The lower border of the mandible in mandibulofacial dysostosis is characteristic of the syndrome. Evaluation of the cephalograms by means of the medial axis analysis and inflectional tangents captures the shape deformity. Morphometric data from lateral cephalograms on seven patients, ages 3 through 20 years, are reported: a total of 22 observations on three males and four females. These forms were compared to normal mandibular forms from the University of Michigan University School Study. The curvature of the gonial angle in the study population is not distinguishable from the normal curvature. Relative to this apparently normal region, there is a marked downward displacement of the symphysis that results in the curvature typical of the lower mandibular border in this syndrome. These findings are not consistent with earlier reports.
Research Interests: Mathematics, Adolescent, Cephalometry, Humans, Child, and 6 moreFemale, Male, Mandible, American, Adult, and Facial Asymmetry
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This article aims to assess the spectrum of unfavorable events or incidents encountered during mandibular distraction and to evaluate the difference in the incident rates among the following treatment groups: (1) native bone distraction... more
This article aims to assess the spectrum of unfavorable events or incidents encountered during mandibular distraction and to evaluate the difference in the incident rates among the following treatment groups: (1) native bone distraction using an external device, (2) native bone distraction using an internal device, and (3) grafted bone distraction using an external device. This retrospective study examined the records of 141 patients treated by mandibular distraction over a 16-year period. Of the total 141 patients, 56 underwent unilateral mandibular distraction and 85 underwent bilateral mandibular distraction, contributing to a total of 226 sided distraction procedures. The number of procedures performed on native bone using external devices was 149, versus 41 internal devices. There were 36 distractions performed on grafted bone with external devices. Incidents were broadly classified into three groups based on a severity index. A minor incident was one that resolved satisfactori...
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Nasoalveolar molding was developed to improve dentoalveolar, septal, and lower lateral cartilage position before cleft lip repair. Previous studies have documented the long-term maintenance of columella length and nasal dome form and... more
Nasoalveolar molding was developed to improve dentoalveolar, septal, and lower lateral cartilage position before cleft lip repair. Previous studies have documented the long-term maintenance of columella length and nasal dome form and projection. The purpose of the present study was to determine the effect of presurgical nasoalveolar molding on long-term unilateral complete cleft nasal symmetry. A retrospective review of 25 consecutively presenting nonsyndromic complete unilateral cleft lip-cleft palate patients was conducted. Fifteen patients were treated with presurgical nasoalveolar molding for 3 months before surgical correction, and 10 patients were treated by surgical correction alone. The average age at the time of follow-up was 9 years. Four nasal anthropometric distances and two angular relationships were measured to assess nasal symmetry. All six measurements demonstrated a greater degree of nasal symmetry in nasoalveolar molding patients compared with the patients treated ...
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Coronoid process hypertrophy can be associated with a variety of congenital or acquired anomalies. There is, however, no consensus on a quantitative or objective measure to define coronoid hypertrophy. Here, the authors describe a novel... more
Coronoid process hypertrophy can be associated with a variety of congenital or acquired anomalies. There is, however, no consensus on a quantitative or objective measure to define coronoid hypertrophy. Here, the authors describe a novel analytical technique using three-dimensional computed tomographic data to accurately and reproducibly assess coronoid size and diagnose coronoid:condyle disproportion. A total of 24 patients were analyzed using three-dimensional medial axis analysis, eight with of unilateral coronoid hypertrophy, four with of bilateral coronoid hypertrophy, and 12 age-matched normal control patients. Measurement of normal subjects (n = 12) demonstrated a coronoid:condyle volumetric ratio less than or equal to 0.5. Analysis of patients with coronoid hypertrophy demonstrated that a coronoid:condyle volumetric ratio greater than or equal to 1.0 was consistent with marked coronoid:condylar disproportion and a ratio between 0.5 and 1.0 was indicative of modest disproporti...
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Patients with syndromic craniosynostosis and midface hypoplasia are often treated with Le Fort III advancement. The authors present four patients with extraordinarily long-term follow-up (in excess of 20 years). An institutional review... more
Patients with syndromic craniosynostosis and midface hypoplasia are often treated with Le Fort III advancement. The authors present four patients with extraordinarily long-term follow-up (in excess of 20 years). An institutional review board-approved retrospective chart review was performed on all patients with syndromic craniofacial synostosis who underwent Le Fort III advancement. Patients with greater than 20 years of cephalometric and photographic records were identified. Lateral cephalograms were obtained preoperatively, immediately postoperatively, at 1-year follow-up, and at long-term follow-up. Cephalograms were traced, digitized, and averaged. Fifty cephalometric landmarks were identified for serial measurements. Of the four patients identified, one had Apert syndrome and three had Crouzon syndrome. Average age at the time of Le Fort III advancements was 11 years (range, 4 to 20 years). Average length of postoperative follow-up was 25 years (± 5 years). No patient had signi...
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Obtaining an esthetic and functional primary surgical repair in patients with complete cleft lip and palate (CLP) can be challenging because of tissue deficiencies and alveolar ridge displacement. This study aimed to describe... more
Obtaining an esthetic and functional primary surgical repair in patients with complete cleft lip and palate (CLP) can be challenging because of tissue deficiencies and alveolar ridge displacement. This study aimed to describe surgeons' assessments of presurgical deformity and predicted surgical outcomes in patients with complete unilateral and bilateral CLP (UCLP and BCLP, respectively) treated with and without nasoalveolar molding (NAM). Cleft surgeon members of the American Cleft Palate-Craniofacial Association completed online surveys to evaluate 20 presurgical photograph sets (frontal and basal views) of patients with UCLP (n = 10) and BCLP (n = 10) for severity of cleft deformity, quality of predicted surgical outcome, and likelihood of early surgical revision. Five patients in each group (UCLP and BCLP) received NAM, and 5 patients did not receive NAM. Surgeons were masked to patient group. Twenty-four percent (176/731) of surgeons with valid e-mail addresses responded to ...
Research Interests: Cleft Palate, Humans, Female, Male, Clinical Sciences, and 4 moreCleft Lip, Prognosis, Nose, and Orthotic Devices
The authors studied the effect of midface distraction on maxillary skeletal position and clinical appearance in patients with Crouzon, Pfeiffer, and Apert syndromes, and examined the stability of these changes at 1 year after distraction.... more
The authors studied the effect of midface distraction on maxillary skeletal position and clinical appearance in patients with Crouzon, Pfeiffer, and Apert syndromes, and examined the stability of these changes at 1 year after distraction. Fifteen consecutive patients (six male and nine female; average age, 5.9 years) underwent Le Fort III osteotomy with midface advancement using a rigid external distraction device. Six patients had Crouzon, five had Pfeiffer, and four had Apert syndrome. Midface advancement was initiated at the level of the occlusal splint and at the zygomatic/maxillary anchor screws. The device was activated 11 mm on average, at a rate of 1 mm per day. Twenty anatomical landmarks were identified and digitized at three time intervals, and displacement of each landmark was compared with its pretreatment position. By the time of device removal, point A had advanced sagittally along the x axis 15.85 mm and moved downward 1.06 mm along the y axis; the orbitale was moved sagittally along the x axis 12.72 mm and downward 1.99 mm along the y axis. Maximum mean advancement (17.16 mm) was observed at the upper incisal edge. Maxillary and mandibular skeletal discrepancy was significantly decreased, with the ANB angle changing from -5.87 to +13.17 degrees. At 1 year after distraction, point A had advanced an additional 0.81 mm, and the orbitale and upper incisal edge had moved posteriorly 0.07 mm and 1.34 mm, respectively. Significant midface advancement can be achieved and maintained with rigid external distraction of the Le Fort III osteotomy segment (up to 24 mm), with excellent stability of the advanced midfacial skeleton.
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The purpose of this study was to characterize soft-tissue profile changes following Le Fort III (midface) distraction in growing patients with syndromic craniosynostosis. The cohort consisted of 20 syndromic patients who underwent Le Fort... more
The purpose of this study was to characterize soft-tissue profile changes following Le Fort III (midface) distraction in growing patients with syndromic craniosynostosis. The cohort consisted of 20 syndromic patients who underwent Le Fort III osteotomy with midface advancement using a rigid external distraction device. The mean age at surgery was 5.7 years (range, 3 to 12.5 years). Lateral cephalograms were obtained preoperatively (time 1), after distraction device removal (time 2), and 1 year after distraction (time 3). Ten skeletal hard-tissue and 11 soft-tissue profile landmarks were identified and digitized at time points 1, 2, and 3. The x and y displacement of each landmark was studied to determine the ratios for soft- to hard-tissue change. The horizontal ratio of soft- to hard-tissue change for nasal dorsum to orbitale was 0.73:1 and the soft-tissue tip of nose to the anterior nasal spine was 0.86:1. The horizontal ratio of soft-tissue A point to hard-tissue A point was 0.88:1. The horizontal ratio of the upper lip position to the labial surface of maxillary incisor was 0.88:1. The ratio for nasal tip elevation to the anterior nasal spine advancement was 0.27:1. The result of this study supported the hypothesis that there exists a linear relationship between soft- and hard-tissue changes in the horizontal direction for the midface landmarks following Le Fort III distraction. However, there was a nonlinear relationship between soft- and hard-tissue changes in the vertical direction. Therapeutic, IV.
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The classic Le Fort III procedure was recommended in syndromic craniosynostotic children to reduce exorbitism, improve airway function, and decrease dysmorphism. This study reports on a cohort of syndromic craniosynostosis patients who... more
The classic Le Fort III procedure was recommended in syndromic craniosynostotic children to reduce exorbitism, improve airway function, and decrease dysmorphism. This study reports on a cohort of syndromic craniosynostosis patients who have undergone early primary subcranial (classic Tessier) Le Fort III advancement and who have been followed longitudinally through skeletal maturity and beyond. In this study, the Le Fort III advancements all occurred between the ages of 3 to 5 years, with a mean age of 4.6 years. Subsequently, these early Le Fort III patients were followed throughout development with longitudinal dental, medical, radiographic, and photographic evaluations conducted through skeletal maturity and beyond. For study inclusion, the patients had to have preoperative medical photographs and cephalometric studies at 6 months and 1, 5, and 10 years postoperatively after the primary Le Fort III advancement as well as cephalometric documentation 6 months and 1 year after the secondary midface advancement after skeletal maturity. After early or primary Le Fort III advancement, there was no evidence of relapse and only minimal anterior or horizontal postoperative growth of the midface. However, there was also a return of occlusal disharmony from "anticipated" mandibular growth, approaching a maximum at skeletal maturity. The dysmorphic concave facial profile and malocclusion, and airway and ocular considerations, provided the impetus for secondary midface surgery after skeletal maturity was attained. The data demonstrate that early Le Fort III advancement performed before the age of mixed dentition does not obviate the need for a secondary advancement after skeletal maturity is reached. Therapeutic, IV.
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The application of distraction osteogenesis is an effective treatment for mandibular deficiencies. A priori, a horizontal vector of distraction was hypothesized to produce horizontal movement of the mandible and a vertical vector of... more
The application of distraction osteogenesis is an effective treatment for mandibular deficiencies. A priori, a horizontal vector of distraction was hypothesized to produce horizontal movement of the mandible and a vertical vector of distraction to produce primarily downward vertical elongation of the ramus. This study was designed to test this hypothesis. A retrospective clinical and radiographic review was conducted of all patients who underwent bilateral, uniplanar distraction with an external device at the New York University Medical Center between October of 1990 and February of 2004 (n = 185). A subset of 15 patients was identified who satisfied inclusion criteria and had adequate predistraction and postdistraction lateral cephalograms. Cephalometric tracings were made and multiple landmarks were assessed before and after distraction. A strong correlation was noted between the vector of distraction and rotation of the symphyseal plane, movement of the mandibular symphysis, and change in interocclusal angle. A horizontal vector of distraction resulted in minimal counterclockwise rotation of the symphyseal plane, greater downward vertical translation of the mandibular symphysis, and minimal closure of an anterior open bite. In contrast, a vertical vector resulted in greater counterclockwise rotation of the symphyseal plane, greater horizontal projection of the mandibular symphysis, and greater closure of an anterior open bite. Mathematical formulas were derived to correlate the distraction vector and mandibular movements. Successful distraction is dependent on accurate prediction of outcomes. This study demonstrates that the vector of distraction predictably affects the mandibular response during bilateral distraction osteogenesis but contradicts the a priori hypothesis.