Mandibular distraction osteogenesis: a historic perspective and future directions.

Although orthognathic surgery has gained a generalized acceptance for maxillomandibular deformity correction, several limitations are associated with acute advancement of osteotomized bone segments. Furthermore, large skeletal discrepancies, such as those seen in syndromic patients, require such extensive bone movements that the surrounding soft tissues will not adapt to their new position, resulting in relapse or compromised function and esthetics. Recently, a number of experimental and clinical investigations have demonstrated that gradual mechanical traction of bone segments at an osteotomy site created in the craniofacial region can generate new bone parallel to the direction of traction. This phenomenon, known as distraction osteogenesis, opens up new possibilities in the correction of craniofacial deformities by orthodontists and maxillofacial surgeons. Hence, the purpose of this article is to review the historic development and biologic foundation of mandibular distraction osteogenesis, critically evaluate the current mandibular distraction devices with their clinical applications, and predict the future evolution of mandibular osteodistraction techniques.     

LeFort III advancement with and without osteogenesis distraction

The LeFort III osteotomy is the surgical treatment performed in patients with mid-facial retrusions in craniofacial dysostoses such as Crouzon, Apert, Pfeiffer syndromes, etc. The first authors to report the accomplishment of this osteotomy were Gillies and Harrison in 1951, this technique was then resumed and improved by Tessier in 1967, who made five different variants mainly regarding the typology of the osteotomy concerning the lateral wall of the orbit. Recently, distraction techniques have been applied to the upper mid-face which foresees a gradual advancement of the mid-face through the osteogenetic distraction procedure. The purpose of this retrospective clinical outcome study is to evaluate and compare the two different surgical techniques through the experience acquired during the treatment of 15 cases of craniofacial dysostoses from 1990-2005, and through international literature. The standard surgery technique was performed in 5 of these patients, whereas the osteogenetic distraction technique was performed in the remaining 10. All patients were studied preoperatively through the acquisition of photographic images, cephalometric analysis of the skull, and the study on plaster models of the occlusion of the dental arches. The instrumental exams required before surgery are the following: telecranium X-rays in two projections, orthopanoramic X-rays, CT. The results of this study indicate that the osteodistraction technique represents the choice treatment in severe retrusions of the mid-face while the traditional surgical technique remains indicated in adult patients that are in need of moderate advancements.     

Mandibular distraction of the body and ramus

With the ever increasing interest in the field of osteodistraction techniques, the mandible is certainly the most studied anatomical site, both experimentally and clinically. Currently, the methods of mandibular distraction can be classified by position (intra- or extraoral), by the direction of distraction and by the site of application (toothborn, boneborn or hybrid fixation). To guarantee good results from the osteodistraction procedure, it is fundamental to have an accurate preoperative plan considering the correct classification and evaluation of the patient combined with a valid project regarding the direction of the distraction vector. One of the most important aspects to consider is the orientation of the distractor, especially if the defect to be corrected is three-dimensional. Regarding the correct planning of the operation, knowing the secondary effects of the distraction on the soft tissues, muscles and nerves, the temporomandibular joint and velopharyngeal functioning is of fundamental importance. It is worth considering particular situations in which osteodistraction is extremely helpful in maxillofacial surgery, for example in the construction of a neocondyle, in bone replacement during oncologic interventions, in obstructive sleep apnea correction and in hemi-mandibular reconstruction.     

Effects of distraction forces and frequency of distraction on bony regeneration

The rate and frequency of distraction have a decisive influence on the regenerative process. We tested a newly developed hydraulic osteodistractor in 12 pigs, which were assigned to have continuous and intermittent osteodistraction of the mandible after osteotomy. The forces necessary to distract the mandible were recorded during intermittent distraction. These data were then used for continuous distraction of the bone. Continuous osteodistraction resulted in intramembranous regeneration of bone, whereas intermittent osteodistraction caused chondroid ossification in the regeneration of the bone. Continuous osteodistraction caused speedier regeneration, and distraction forces were lower than with intermittent distraction.     

Three-dimensional surgical planning for maxillary and midface distraction osteogenesis

Computerized surgical planning protocols for distraction osteogenesis are still in their rudimentary phase. The authors have developed a system to plan distraction osteogenesis in craniofacial and maxillofacial surgery that uses three-dimensional computed tomography scans and computer simulation in a virtual reality environment. This involves the creation of a three-dimensional bone model of the craniofacial skeleton, which incorporates virtual globes. Virtual osteotomies are performed on the bone model and the movements of the bone segments are simulated. The program generates a recipe for the linear and the angular changes necessary to achieve the desired outcome. The purpose of this article is to present this surgical planning process and discuss its use in maxillary and midface distraction.     

Is early osteodistraction a solution for the ascending ramus compartment in hemifacial microsomia? A literature study.

AIM: In hemifacial microsomia, osteodistraction before skeletal maturation claims to induce both bone- and soft-tissue generation in such a way that conventional bone grafting and soft-tissue grafts are not necessary. Early osteodistraction in facial microsomia would have a positive effect on the 'functional matrix', and allow symmetrical vertical and sagittal expansion of the midface and mandible. The aim of this literature survey was to find evidence for this hypothesis by analysing long-term follow-up reports on distraction histiogenesis in the ascending ramus. MATERIAL: Only eight published studies were found, of which only two had more than ten patients, two were case reports, and three were from the same institution. RESULT: Invariably, the results pointed towards over-correction, repeated osteodistraction procedures, soft-tissue stretching (but no lateral augmentation), and to soft-tissue complications. The studies did not allow a conclusion to be made as whether increased vertical gain in the ascending ramus was unstable because of decreased growth on the affected side, inborn or iatrogenic, or due to resorption of the bone generated by distraction. To date, there is no evidence that osteodistraction produces better results and has lower morbidity than conventional growth centre transplantation and separate soft-tissue augmentation. CONCLUSION: Recommendations for prospective studies are: sharp differentiation between the four Pruzansky-Kaban mandibular types, multi-centre study of a surgical protocol to increase the sample number using a standard three-dimensional evaluation protocol, and differentiation between decreased growth and collapse of the newly generated bone.     

Temporo-mandibulary joint state after distraction osteogenesis use in cases of different genesis facial skeleton deformities elimination

Distraction osteogenesis is one of the most often used methods for the treatment of craniofacial deformities. One of the clinical effects of the distraction is the tissue growth induction process in the conditions of its influence upon condylar process of mandible. Besides it distraction mandible osteosynthesis and active functional therapy stimulates neoarthrosis development in cases of temporo-mandibulary joint ankylosis. According to our opinion distraction osteogenesis as the technique for facial skeleton deformities elimination is indicated in cases of surgical treatment of joint ankylosis, deforming arthrosis for mandible size recovery and patients' functional rehabilitation.     

The role of distraction osteogenesis in the management of craniofacial syndromes

In patients with craniofacial syndromes, the skeletal discrepancy is often severe, and the ability to achieve the desired movement by immediate surgical repositioning is difficult because of restrictions of the soft-tissue envelope. The technique of distraction osteogenesis has provided an additional option for managing congenital and acquired craniofacial deformities. The use of distraction osteogenesis is, however, still within its infancy as a treatment modality. It is unlikely that the procedure will obviate the need for definitive orthognathic surgery at skeletal maturity in most patients with craniofacial anomalies. The role of distraction osteogenesis in craniofacial surgery will continue to evolve rapidly with increasing experience and technological advancement. Because distraction osteogenesis in the facial skeleton is a relatively new approach, analysis of the contemporary literature is imperative, and future long-term studies on the effects and outcome of distraction are essential.     

Resorbable distraction of the mandible: technical evolution and clinical experience

The author has used various designs of single-stage resorbable distractors to lengthen the mandible in 100 patients aged 7 days to 16 years (mean, 4.24 y; 49 girls, 51 boys) with predictable results and minimal morbidity since 2002. The range of distraction was 15 to 30 mm (mean, 25.4 mm). Indications for surgery included mandibular hypoplasia associated with Pierre Robin sequence, craniofacial microsomia, Treacher Collins, and Nagers syndrome. The history of the development of resorbable polymers for use in craniofacial surgery and the evolution of distraction osteogenesis are reviewed. The melding of these 2 innovative technologies has led to the development of a new class of single-stage resorbable devices. These devices are quite different from the titanium distraction devices that have been used in clinical practice for more than 15 years. Through continued clinical application, the surgical methodology for resorbable distraction has been refined and simplified, although still-evolving continued experience with resorbable distraction has greatly decreased operative time and improved results.     

Multidimensional osteodistraction for correction of implant malposition in edentulous segments

This study examined multidimensional osteodistraction as a treatment method for correction of implant malposition and as an alternative to augmentation procedures. The prosthetically unfavourable implant positions were due to growth-related implant malposition (in the context of treatment of young patients with oligodontia) or primary bone-driven implant insertions. The radiographical and clinical findings obtained with this osteodistraction technique are presented and discussed. A tooth-supported osteodistractor for multidimensional distraction with custom-fabricated distraction abutments was used for treatment of 8 patients with a total of 9 maxillary and mandibular edentulous segments including single-tooth gaps. All patients underwent an osteotomy at a minimum distance of 1 mm from the implant surface. Following primary wound healing, distraction was carried out by 1 mm in vertical direction and 0.5 mm in the demanded transverse direction daily until the prosthetically optimized position was achieved. During and after the 12-week retention phase, the patients were evaluated clinically and radiographically. Multidimensional osteodistraction was carried out successfully in all 8 patients. The distraction distances were 3 to 11 mm in vertical direction and a maximum of 5 mm in buccolingual/buccopalatal direction. The malpositioned implants were brought into a prosthetically optimized position in all cases. The results of this study show that this multidimensional osteodistraction technique allows both augmentation of edentulous segments with a clearly compromised implant host site and correction of unfavourable implant positions.     

Treatment planning and biomechanics of distraction osteogenesis from an orthodontic perspective

As in traditional combined surgical and orthodontic procedures, the orthodontisthas 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 relapse is minimal. Growth after mandibular distraction is variable and appears to be dependent on the genetic program of the native bone and the surrounding soft tissue matrix. A significant advantage of distraction osteogenesis is the gradual lengthening of the soft tissues and surrounding functional spaces. Distraction osteogenesis can be applied at an earlier age than traditional orthognathic surgery because the technique is relatively simple and bone grafts are not required for augmentation of the hypoplastic craniofacial skeleton. In this new technique, the surgeon and the orthodontist have become collaborators in a process that gradually alters the magnitude and direction of craniofacial growth.     

Evaluation of the consolidation period during osteodistraction using computed tomography.

The use of distraction osteogenesis offers an alternative approach to the correction of craniofacial deformities. However, little is known with respect to the appropriate length of the consolidation period for the newly formed bone. The objective of this study was to evaluate, by quantitative computed tomography, the regenerate bone produced during osteodistraction of the dog mandible at three different consolidation times. Twelve skeletally mature male beagle dogs were equally separated into three experimental groups. Each dog underwent 10 mm of bilateral distraction osteogenesis to lengthen the mandible. After the distraction period, the bone was allowed to consolidate for 4, 6, or 8 weeks, at which time the animals were sacrificed and the mandibles harvested for computed tomographic imaging. The results demonstrate a significantly lower mean bone density of the regenerate in the 4 week group when compared with either the 6 or 8 week groups (P < .01). There was no significant difference, however, in mean bone density between the 6 and 8 week groups.     

Vertical alveolar bone distraction at molar region using lag screw principle.

PURPOSE: Recently, alveolar bone distraction has been widely used and several devices have been developed for this purpose. However, there are some disadvantages in each device, especially for distraction of posterior alveolar ridge. The purpose of this study was to develop a new device for vertical alveolar bone distraction at the molar region and to show the results of its clinical application. MATERIALS AND METHODS: The mechanism of device is based on lag screw principle and the device consists of the following 4 components; distraction screw, hole implant fixture, supporting plate, and temporary short implant and/or neighboring natural teeth. The distraction screw suspended at the supporting plate is inserted into the internal thread of the hole implant fixture placed at alveolar transport segment. If the distraction screw turns at the supporting plate, the hole implant fixture with transport segment moves to the supporting plate without vertical movement of the screw at the supporting plate like a lag screw. After an animal experiment using 4 beagle dogs, the device was clinically applied in 4 patients before implant insertion. RESULTS: The distraction of the alveolar bone could be successfully performed in all patients without any complications. The direction of distraction with this device could be adjustable, and the alveolar bone could be distracted not only vertically but also horizontally. Moreover, the surgical technique is simple with no need for a second surgery, and there is no occlusal disturbance from the device. CONCLUSIONS: The new device for alveolar bone distraction using lag screw principle can be used effectively in the molar region.     

Distraction osteogenesis of the maxilla and midface using a subcutaneous device: report of four cases

The use of distraction osteogenesis in the hypoplastic maxilla and midface is still controversial. Since the beginning of 1998, 25 patients have been treated with osteodistraction techniques for various reasons. Among them were four patients who were treated by high LeFort I osteotomies and insertion of a newly developed subcutaneous distraction device in the malar region. Distraction osteogenesis was successful in all four cases resulting in a mean sagittal bone gain of 12.0 mm (range 7-14) at the level of distractor fixation. All patients were kept under orthodontic supervision during osteodistraction. The final occlusal relation was satisfactory. Cephalometric measurements after distraction showed an anterior rotational movement of the midface region. As the question of relapse and further growth is still not clear, Delaire masks are used to stabilize the surgical result after removal of the distractor. The importance of long-term follow-up is stressed.     

Craniofacial bone tissue engineering

Repair and reconstruction of the craniofacial skeleton represents a significant biomedical burden, with thousands of procedures per-formed annually secondary to injuries and congenital malformations. Given the multitude of current approaches, the need for more effective strategies to repair these bone deficits is apparent. This article explores two major modalities for craniofacial bone tissue engineering: distraction osteogenesis and cellular based therapies. Current understanding of the guiding principles for each of these modalities is elaborated on along with the knowledge gained from clinical and investigative studies. By laying this foundation, future directions for craniofacial distraction and cell-based bone engineering have emerged with great promise for the advancement of clinical practice.     

Mineralization dynamics of regenerate bone during mandibular osteodistraction.

Distraction osteogenesis offers an alternative approach for the correction of craniofacial deformities, yet little substantive data is available regarding mineralization of the forming regenerate. The purpose of this study was to evaluate, by plain film radiography and digital subtraction radiography, the mineralization dynamics of regenerate bone during osteodistraction. Thirteen skeletally mature male beagle dogs underwent 10 mm of bilateral mandibular distraction osteogenesis, at which time the bone was allowed to consolidate for either 4, 6, or 8 weeks. The tissues were then evaluated clinically and radiographically. The results demonstrate that several different types of regenerate are evident during mineralization of the distraction gap. A classification system is presented based on the length, width, and density of the mineralizing regenerate, as well as the presence or absence of an interzone. It appears that important factors for determining regenerate stability are the presence or absence of an interzone, as well as the width of the regenerate relative to the host bone segments. Finally, in cases where an interzone is present, subtraction radiography may provide a means of evaluating the level of mineralization within the interzone as well as the dynamics of mineralization over the course of distraction and consolidation.     

Vertical mandibular bone augmentation by the osteodistraction of the transplanted fibula free flap: A case series with long-term follow-up

Vertical augmentation of the mandible to prepare dental implant therapy is still a challenge, especially with large mandible defects. Reconstruction with fibula free flap is a regularly applied approach in such cases, but it does not always yield optimal results: the resulting crestal height might differ significantly from the crestal height of the patient's intact bone, which makes esthetic and functional rehabilitation difficult. Osteodistraction of the integrated flap is a known but rarely discussed approach where the already integrated flap undergoes additional distraction. Through the four cases reported here, we would like to demonstrate that the osteodistraction of the transplanted fibula free flap is a useful and efficient method of secondary augmentation for cases where the flap itself fails to produce the desired crestal height, and no other method is applicable. The cases show that the method allows outcomes that are highly satisfactory, both in the functional and esthetic sense.     

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.     

Dentofacial rehabilitation by osteodistraction, augmentation and implantation despite osteogenesis imperfecta

Osteogenesis imperfecta-- a heritable systemic disorder characterized by enhanced bone fragility-- is frequently associated with a Class III malocclusion and distinct dental disorders. This patient, suffering from a late form of osteogenesis imperfecta, displayed early loss of teeth and severe maxillary hypoplasia. Bone grafting of the alveolar ridge was assumed not to guarantee a neutral basal relation before dental implantation. Due to the risk of atypical fractures conventional orthognathic surgery was excluded in the atrophic maxilla. In contrast to a conventional Le Fort I osteotomy, osteodistraction of the maxilla can be performed omitting the precarious down-fracture procedure. Despite a lack of reports on this technique in patients with osteogenesis imperfecta, dysgnathia was corrected by osteodistraction of the upper jaw. The loss of teeth was treated by augmentation of the alveolar crest using autogenous bone from the iliac crest followed by placement of dental implants. Stable normocclusion of the implant-supported overdentures was achieved without any detectable relapse over 4 years. For the first time it has been demonstrated that advanced surgical techniques like osteodistraction, alveolar crest augmentation and dental implantation can successfully be combined for dentofacial rehabilitation even in patients suffering from osteogenesis imperfecta.     

A novel osteogenic distraction device for the transversal correction of temporozygomatic hypoplasia

BackgroundHemifacial microsomia (HFM) is a congenital disorder characterized by craniofacial malformation of one or both sides of the lower face. Since these anomalies are associated with soft-tissue deficiencies, corrective surgery is often difficult. Bone grafts have typically been used for augmentation, but distraction osteogenesis now offers an alternative for many craniofacial deficiencies, but there are few if any appropriate distraction devices and surgical procedures for the augmentation of craniofacial transversal dimensions.MethodsThe aim of this study was to evaluate a technique for guided augmentation of craniofacial transversal dimensions through distraction osteogenesis. We tested the efficacy of a prototype distractor, developed in collaboration with Medartis, using cadavers and demonstrated its application for the correction of the transverse dimension of the temporozygomatic region in a patient with Goldenhar syndrome.ResultsCT scans showed a 4-mm transverse augmentation of the bony surface after 9 days and a 10-mm increase after 30 days. Upon removal of the distractor (60 days after the first surgery) CT indicated good bony fusion and a stable result in the transverse plane. Six months after removal of the distractor, 3D computed tomography confirmed the success of the transverse augmentation, as it appeared to be stable and reliable.ConclusionsDistraction osteogenesis, using our device, can be used to correct the transverse dimension of the temporozygomatic region in HFM patients. It should also be considered for the correction of residual postsurgical skeletal deficiency due to surgical relapse or deficient growth, and unsatisfactory skeletal contour.