Cranio-facial distraction osteogenesis: a review of the literature. Part II: Experimental studies

In this study the literature dealing with experimental cranio-facial distraction osteogenesis (DO) was reviewed. A PUBMED search (National Library of Medicine [NCBI] revised 1 April 2001) from 1966 through December 2000 was conducted. Key words used in the search were: distraction, lengthening, mandible, mandibular, maxilla, maxillary, midface, midfacial, monobloc, cranial, cranio-facial, maxillofacial. This search revealed a total of 120 experiment-orientated articles that were all analyzed in detail in this study. The purpose of the experimental study, animal model, animal growth status, type of distraction, type of surgery, distraction rate and rhythm, latency and contention period, amount of lengthening, relapse, complications and nature of the distraction device were analyzed. This review revealed that a total of 1207 animals were used in seven different animal models for research on cranio-facial DO: 54 using dogs (45.0%), 25 using rabbits (20.8%), 18 using sheep (15.0%), 11 using minipig (9.2%), seven using monkeys (5.8%), four using rats (3.3%) and one using a cat model (0.8%). Based on the results of this study, an attempt was made to provide biological DO parameters and guidelines for future research on experimental cranio-facial DO related to the appropriate animal model.     

Trans-sinusal maxillary distraction for correction of midfacial hypoplasia: long-term clinical results

Maxillary distraction osteogenesis is indicated in severe angle class III malocclusions, and severe maxillary hypoplasia among some cleft patients and other craniofacial deformities. Twenty patients, aged 8-48 years (mean 17.8+/-10.5 SD) with maxillary and midfacial hypoplasia were treated. The follow-up period was 13-65 months (mean 35+/-16.3 SD). A trans-sinusal maxillary distractor was placed intraorally at each side of the maxilla. The distraction vector was predicted using specialist software, and was transferred to the patients using stereolithographic models and individual templates. A (high) Le Fort I type osteotomy was performed. The amount of activation varied from 8 to 17.5 mm (mean 13.1+/-2.9 SD). Soft and hard tissue formation resulted in complete healing across the distraction gaps. The distractors are almost completely submerged, and can be left in place as long as necessary to avoid relapse. Wit's appraisal was used to measure the stability of the long-term distraction results. Results up to 5 years after distraction showed considerable maxillary advancement with long-term stability. Ongoing growth of the facial skeleton must be considered when distraction osteogenesis is chosen in growing patients.     

Long-term skeletal stability after maxillary advancement with distraction osteogenesis in cleft lip and palate patients: A systematic review

Objective:To systematically review the long-term skeletal stability after maxillary advancement with distraction osteogenesis (DO) in cleft lip and palate (CLP) patients.Materials and Methods:Electronic databases, grey literature, and reference list searches were conducted. The inclusion criteria were stability of maxillary advancement with distraction osteogenesis assessed at the posttreatment follow-up ≥ 1 year in CLP patients. Full articles were retrieved from abstracts or titles that appear to meet the inclusion criteria or lacked sufficient detail for immediate exclusion. Once full articles were collected, they were again reviewed considering more detailed inclusion criteria for a final selection decision. A methodologic quality assessment tool was utilized.Results:Thirty abstracts/titles met the initial search criteria, and 13 articles were finally selected. Overall, methodologic quality scores were high in only one randomized clinical trial. After maxillary advancement with DO in CLP patients, the long-term horizontal relapse in A-point was less than 15% in eight studies and between 20% and 25% in four studies. The study that was judged as a high-quality study reported 8.2% horizontal relapse in A-point. The relapse rate was higher in DO with external distracter device than DO with internal distracter device.Conclusions:Current evidence suggests maxillary advancement with DO has good stability in CLP patients with moderate and severe maxillary hypoplasia.     

Klippel-feil: A syndrome in the occipital-cervical spine field and its dentofacial manifestations

Klippel-Feil syndrome (KFS) is defined by congenital cervical vertebral spine fusion and is seen with a wide spectrum of dental manifestations and craniofacial profiles. Previous studies on lateral cephalograms have documented an association between fusion of the cervical vertebrae and deviations in the craniofacial profile in non-syndromic patients with severe malocclusion. To our knowledge, no previous studies have described the craniofacial profile including the cranial base of KFS patients on lateral cephalograms. Therefore KFS and its craniofacial and dental manifestations were described according to existing literature and additionally the craniofacial profile and cranial base was analysed on lateral cephalograms of two patients with KFS. According to the literature the dental manifestations of KFS-patients included oligodontia, overjet, cross bite, open bite and deep bite. The craniofacial profile was clinically described as reduced lower facial height, midfacial hypoplasia, and mandibular prognathia. The analyses of the two lateral cephalograms showed increased mandibular inclination, increased vertical jaw-relationship, increased jaw angle and maxillary retrognathia. The cranial base was normal in both cases. The sagittal jaw relationship and mandibular prognathia varied between the two cases. The literature review and the analyses of the two lateral cephalograms have shown that deviations in the occipital and cervical spine field as KFS were associated with deviations in the teeth and craniofacial profile.     

Experimental model of distraction osteogenesis in edentulous rats

Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin. Study protocol: latency: 6 days, distraction: ? turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.     

Longitudinal dento-skeletal changes in UCLP patients following maxillary distraction osteogenesis using RED system

Longitudinal dento-skeletal changes in unilateral cleft lip and palate (UCLP) patients following maxillary distraction osteogenesis using the rigid external distraction device (RED) were analyzed. Twelve Japanese non-syndromic UCLP patients who underwent maxillary distraction at the mean age of 16.4 years were used as subjects. Serial sets of lateral cephalograms, taken at 4 stages: 1) before osteotomy, 2) immediately after distraction, 3) 6 months and 4) 12 months post-osteotomy, were analyzed. Statistical analyses, including a paired t test, Pearson correlation analysis and stepwise linear regression analysis, were performed to distill characteristic dento-skeletal changes. In accordance with maxillary advancement, significant amounts of up-forward movement of the nasal bone, mandibular rotation and maxillary dental changes were observed. Maxillary dental changes were significantly related to the amount of mandibular rotation and force system of maxillary traction. Significant dento-skeletal relapse was found to occur during the 0-to-6-month follow-up period, but not in the 6-to-12-month follow-up period. Maxillary relapse was significantly related to the amount of maxillary advancement and severity of pre-surgical maxillary hypoplasia, while mandibular relapse was significantly related to maxillary dento-skeletal relapse. Successful clinical application of this procedure therefore requires consideration of both the surrounding dento-skeletal changes and the traction force system.     

Dual segmental distraction osteogenesis of the midface in a patient with Apert syndrome.

OBJECTIVE: To present orthodontic treatment combined with dual segmental distraction osteogenesis in a patient with Apert syndrome. PATIENT: A 15-year-old boy exhibited severe midfacial hypoplasia with retruded and hypoplastic maxilla and anterior open bite. The patient was treated with a rigid external distraction II system for distraction osteogenesis, a preadjusted edgewise appliance, and a modified maxillary protraction headgear. The concave profile with midfacial hypoplasia was improved. A tight occlusal relationship between maxillary and mandibular teeth was achieved. Postoperative treatment results have been stable for 1 year.     

Long-term stability of LeFort III distraction osteogenesis with a rigid external distraction device in a patient with Crouzon syndrome

A 6-year-old boy, diagnosed with Crouzon syndrome, had moderate exorbitism, a concave profile, an anterior crossbite of -4.0 mm, and a skeletal Class III jaw-base relationship caused by midfacial hypoplasia. At age 8 years 9 months, a LeFort III osteotomy was performed, and distraction osteogenesis was immediately started with the rigid external distractor system. The midface was advanced approximately 10.0 mm for 6 days, including overcorrection. After the distraction, a reverse headgear was used for 6 years to prevent relapse and to accelerate expected growth. At age 16 years 5 months, after extraction of the maxillary first premolars and mandibular third molars, 0.022-in preadjusted edgewise brackets were placed to treat the edge-to-edge incisor relationship and minor crowding. After 13 months of treatment, the facial profile was significantly improved, and an acceptable occlusion was achieved. During the 9-year observation period after the distraction, acceptable facial growth occurred, and no relapse of the maxillary advancement was observed. However, syndrome-specific growth and methodologically induced relapse should be considered when planning a LeFort III distraction in children for the treatment of Crouzon syndrome.     

Mandibular reconstruction in the growing patient with unilateral craniofacial microsomia: a systematic review

The purpose of this systematic review is to provide an overview of the surgical correction of the mandible in unilateral craniofacial microsomia (UCM) performed in the growing patient, and its long-term outcome and stability. The following databases were searched: PubMed, Embase, Cochrane, and Web of Science. Articles reporting prospective and retrospective studies of patients not older than 16 years (N ≥ 4) who had undergone surgical correction of a craniofacial microsomia spectrum condition using grafts, osteotomies, distraction, or combinations of these, were reviewed. The period of follow-up was selected to be ≥1 year. After inclusion, the articles were evaluated on short- and long-term outcomes, relapse, and any increase in asymmetry following treatment. Thirty of 1611 articles were included in the qualitative synthesis. Analysis of the surgical mandibular correction of UCM showed that the outcome is not so much treatment-dependent, but patient-dependent, i.e. deformity gradation-dependent. The type I–IIa Pruzansky–Kaban patient had the best results with regard to minimal relapse and/or minimal increase in asymmetry. Single-stage correction of the asymmetry should be postponed until the permanent dentition stage. It can be concluded that in the treatment of the severely hypoplastic mandible, the patient will benefit from a multi-stage treatment protocol if indicated for functional or psychological problems.     

Maxillary anterior segmental advancement by using distraction osteogenesis: a case report

After the first clinical application of distraction osteogenesis (DO) to correct mandibular deformity was reported in 1992, various applications such as maxillary or midface advancement, temporomandibular joint reconstruction, alveolar augmentation, and mandibular widening have been described in the oral and maxillofacial region. Block et al and Altuna et al first examined anterior segmental DO experimentally in the maxilla and reported successful results. After these studies, DO has been used clinically for the total advancement of the maxilla or midface. But no clinical application of DO for maxillary anterior segmental advancement was found by a review of the literature in English. In this article, we present a case with a skeletal Class III abnormality resulting from a maxillary deficiency, which was treated by using anterior segmental DO.     

Long term stability of mandibular advancement procedures: bilateral sagittal split osteotomy versus distraction osteogenesis

The aim of this study was to compare the postoperative stability of the mandible after a bilateral lengthening procedure, either by bilateral sagittal split osteotomy (BSSO) or distraction osteogenesis (DO). All patients who underwent mandibular advancement surgery between March 2001 and June 2004 were evaluated. There were 17 patients in the BSSO group and 18 patients in the DO group. The decision to use intra-oral distraction or BSSO for mandibular advancement primarily depended on the choice of the patient and their parents. In both groups, standardized cephalometric radiographs were taken preoperatively, postoperatively (BSSO group) or directly post-distraction (DO group) and during the last study measurement in May 2008. Cephalometric analysis was performed using the following measurements: sella/nasion-mandibular point B and sella/nasion-mandibular plane. Point B was used to estimate relapse. This study showed no significant difference in relapse between the BSSO and the DO groups measured 46-95 months after advancement of the mandible (P>.05). It can be concluded from this study that there is no postoperative difference in the stability between BSSO and DO after mandibular advancement after 4 years.     

Distraction osteogenesis: the effects of orthodontic tooth movement on distracted mandibular bone

The application of distraction osteogenesis in craniomaxillofacial surgery has created new treatment methods for patients with craniofacial skeletal dysplasias. Most of the applications in the craniofacial skeleton have been for the correction of severe congenital or acquired conditions. As more understanding is gained with these new approaches, refinements in techniques will enhance treatment planning and outcome. This will expand the application of distraction osteogenesis to more common, less severe types of skeletal dysplasias. One of the important areas in mandibular distraction osteogenesis is the management of the dental gap created when distraction is applied within the tooth-bearing segment of the mandibular body. In this study, the authors investigated the effects of orthodontic tooth movement into new bone created through the process of distraction osteogenesis. Orthodontic tooth movement through newly formed mandibular bone in the canine model was performed and, through histologic studies, was found to create compact bone along the path of the moving tooth. This compact bone replaced the more unstructured woven bone that was originally created by the process of mandibular distraction osteogenesis. These findings indicate that orthodontic tooth movement can be performed in distracted bone and can have significant influence on the stability and long-term structural preservation of the bone created by distraction osteogenesis within the tooth-bearing segment of the mandible.     

Monobloc and facial bipartition distraction with internal devices.

Distraction osteogenesis (DO) permits gradual lengthening of the craniofacial skeleton. With the advent of new internal devices, monobloc (M) and facial bipartition (FB) DO are feasible. The rationale behind M and FB distraction is (1) gradual advancement of the M segment is not associated with a substantial retrofrontal dead space; (2) because 5 to 7 days elapse prior to distraction, the nasofrontal opening, in theory, is allowed to remucosalize; (3) gradual expansion of the soft tissues takes advantage of skin creep, potentially limiting relapse; (4) the procedure appears to be less invasive with decreased blood loss and operative time, enabling its use in infants; (5) overdistraction may eliminate or reduce the frequency of subsequent procedures; and (6) the procedure may be combined with FB and skull vault remodeling to provide excellent results in more complex craniofacial dysostosis problems. Five children underwent M advancement (N = 3) and M with FB (N = 2) at 9 months to 5 years of age to correct functional abnormalities such as corneal exposure, increased intracranial pressure, and apnea, as well as severe craniofacial disfigurement. Each patient underwent from 22 to 30 mm of distraction with the Modular Internal Distraction (MID) system, developed by the first author (SRC). There was one infection late in the series along the DO cable track. There were no cases of epidural abscess. In conclusion, MDO, with and without FB, appears to be a safe and effective technique for transcranial frontofacial advancement. The morbidity of the procedure appears to be less than that of conventional M advancement.     

Histological examination of regenerated bone through craniofacial bone distraction in clinical studies

The process of bone formation by distraction osteogenesis of the craniofacial bone has been studied in animals. To our knowledge there are no published findings in which histological examination of craniofacial distraction in humans has been reported. Specimens were obtained from 10 patients who underwent craniofacial distraction: 2 patients who underwent mandibular distraction, 7 patients who underwent midface distraction, and 1 patient who underwent nasal bone distraction. These specimens were examined histologically. The results revealed that 8 of 10 patients exhibited new bone formation. No cartilaginous callus formation was observed in any of the specimens, which strongly suggests that new bone was produced by intramembranous ossification during human craniofacial bone distraction.     

Rigid external distraction osteogenesis for a patient with maxillary hypoplasia and oligodontia.

OBJECTIVE: In this report, the orthodontic treatment combined with rigid external distraction osteogenesis in a 5.5-year-old girl with midfacial hypoplasia and oligodontia is described. PATIENT: The child presented with a reduced maxilla, protruding lower lip, skeletal Class III jaw relationship with a low mandibular plane angle, a short and flattened nose, anterior crossbite, and aplasia of 16 permanent teeth. The patient was treated with rigid external maxillary distraction osteogenesis, maxillary protraction headgear, and Class III elastics. Following treatment, the maxilla was displaced in a forward direction with new bone formation at the tuberosities and the mandible rotated backward in relation to the anterior cranial base. The anterior crossbite was corrected, and the skeletal jaw relationship changed from a Class III to a Class I skeletal pattern. The soft tissue facial profile showed that the nasal projection had been increased, the nasolabial angle increased, and the lower lip protrusion was reduced. Postoperative treatment results were acceptable. CONCLUSION: This report documents that early maxillary advancement with rigid external osteogenesis offers a promising treatment alternative for a very young patient with maxillary hypoplasia and oligodontia.     

Geometric morphometric assessment of treatment effects of maxillary protraction combined with chin cup appliance on the maxillofacial complex

The aim of this study was to investigate the treatment effects on the maxillofacial complex by maxillary protraction combined with chin cup therapy among growing children. An effective geometric morphometric assessment of cephalometric radiographs, using Procrustes analysis and thin-plate spline analysis, was applied to evaluate shape change in the craniofacial and midfacial configurations of a treated sample of 20 children with skeletal Class III malocclusion. This was compared with matched untreated skeletal Class III controls. Marked treatment induced change involved the maxilla and the mandible. Major deformation consisted of forward advancement of the maxillary complex with negligible rotation of the palatal plane and a forward direction of growth of the mandibular condyle associated with a restriction in sagittal advancement of the chin. Considerable dentoalveolar components contributed to the correction of anterior crossbite. Further detailed study of skeletofacial remodelling in response to maxillary protraction in other skeletal components, including the cranial base and the mandibular complex that contribute to Class III skeletal discrepancies, is warranted.     

Mandibular distraction osteogenesis: a rabbit model using a novel experimental design.

PURPOSE: Distraction osteogenesis (DO) is a surgical procedure that targets bone regeneration and elongation, currently used in the treatment of many craniofacial deformities. The quest for optimization of DO clinical parameters has led to the development of a variety of animal models. Our study aims to establish a rabbit animal model of mandibular DO, in which the control osteotomy and distraction device are placed on the opposite hemimandible from the one being distracted, within the same animal host. Furthermore, we propose to histologically characterize the different stages or distraction and consolidation in the same animal model. MATERIALS AND METHODS: Twenty-five rabbits underwent mandibular osteotomies and bilateral placement of distraction devices. After a latency of 3 days, the distraction device was activated on one side of each animal at a rate of 0.5 mm/12 hours for 7 days, while the other side remained inactive (control). This was followed by a consolidation period of 14 days. Five animals per time-point were killed on days 3, 7, 10, 17, and 24. RESULTS: Gross tissue analysis showed a 7-mm callus formation at the distracted side and a well-healed osteotomy in the non-distracted side. Clinically, a unilateral Class III malocclusion occurred in the distracted side. Histology at each time-point shows new bone formation and orientation of the bony spicules along the axis of the mechanical strain. CONCLUSIONS: We have established and characterized an animal model of mandibular DO that outlines valid biologic controls and provides thorough monitoring of the DO process.     

Correction of facial asymmetry with multiplanar mandible distraction: a one-year follow-up study.

OBJECTIVE: To assess the effectiveness of multiplanar mandibular distraction by evaluating the treatment effect and 1-year stability, measuring changes on the affected and nonaffected sides, and evaluating correction of the occlusal plane and oral commissure cant. PATIENTS AND METHOD: Eleven patients aged 5 to 9.4 years (mean 6.7 years ) who underwent unilateral multiplanar mandibular distraction were included, 10 with hemifacial microsomia and one temporomandibular joint ankylosis. Intermaxillary elastics were applied to intraoral dental devices during and after distraction until bony consolidation and occlusal interdigitation were achieved. Radiographs were taken and measured before distraction, after vertical distraction, after completion of distraction, and 1 year after treatment. Frontal facial photographs were obtained to analyze the changes in the position of the oral commissure. RESULTS: The facial profile was improved by sagittal mandibular advancement. Although the facial height increased 6.6 mm during vertical distraction, with a net gain of 5.8 mm in follow-up, the mandibular plane angle was maintained. The affected mandibular length increased 8.3 mm after distraction and remained unchanged after 1 year. Ramus height increased 12.7 mm after distraction and relapsed 3.8 mm at follow-up (30%). The affected body length demonstrated postoperative growth of 3.1 mm. Correction of the chin deviation was 9.8 mm after distraction and relapsed 1.6 mm (16.3%) after 1 year. Canting of the occlusal plane and oral commissure was corrected and remained stable. CONCLUSION: Multiplanar mandibular distraction is an effective treatment for correcting facial asymmetry in young children. The 1-year follow-up revealed that the new sagittal jaw relation and mandibular body length were stable, and the achieved occlusal interdigitation was well maintained. However, the ramus height and chin deviation demonstrated some relapse.     

Management of the severe cleft and syndromic midface hypoplasia

Distraction Osteogenesis (DO) has become a treatment alternative to treat severe craniofacial skeletal dysplasias. A rigid external distraction (RED) device has been successfully used to advance the maxilla as well as the maxillary, orbital and forehead complex (monobloc) in children as young as two years, adolescents and adults. This approach has provided predictable and stable results. It can be applied by itself or as an adjunct to traditional orthognathic and craniofacial surgical procedures. The technical aspects, including planning, surgical and orthodontic procedures, required to properly apply the technique are presented. For this severe group of patients the technique has been found to be simpler and safer than traditional surgical methods. Maxillary and midfacial advancement through distraction has been found to be extremely stable in the patients in whom the technique was used. The reasons for stability are discussed as well as the observed morphologic changes in the facial soft tissues, velopharyngeal mechanism and airway. However, challenges remain to be solved to improve all distraction techniques and the need for collaboration between researchers and clinicians is emphasized to maximize the benefits of this already promising and rewarding approach.     

Recommendations for optimal distraction protocols for various animal models on the basis of a systematic review of the literature

The principles of orthopaedic distraction osteogenesis (DO) have been successfully applied to the craniofacial skeleton, but the latency time, rate and rhythm of distraction, and length of the consolidation period that are optimal for long-bone distraction may be suboptimal for craniofacial DO. The aim of this study was to provide recommendations for optimal distraction parameters in animal experimental research on craniofacial DO. The data used were from studies, added to the PubMed database between 1 January 1973 and 1 January 2007, on the outcome of DO resulting from variations in a single distraction parameter while standardizing the other distraction parameters. Although experimental animal group sizes were rather small, especially in those studies that used large animals, and both skeletally mature and immature animals were used, the (in most cases quantitative) data provided useful information on the optimal parameters in craniofacial DO. A latency period may not be necessary at all. Distraction should be performed at a rate of 1mm/day (this may be halved when small animals such as rats are used) preferably with a continuous rhythm, followed by a consolidation period of 6-8 weeks. These recommendations can be used as basic guidelines for further animal experimental studies on craniofacial DO.