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Biomechanics of mandibular distractor orientation: an animal model analysis.

PURPOSE: Previous reports suggest that device orientation may be one of the most important parameters affecting the successful application of osteodistraction. However, only computer models or cadaver mandibles have been used to investigate the biomechanical effects of device orientation during mandibular distraction osteogenesis. Therefore, the purpose of this study was to compare two different device orientations during bilateral mandibular osteodistraction in an animal model. MATERIALS AND METHODS: Fifteen skeletally mature beagle dogs underwent 10 mm of bilateral mandibular lengthening by intraoral distraction osteogenesis. The dogs were divided into two groups based on the orientation of the distraction device relative to the mandible when viewed occlusally: either parallel to the body of the mandible (group I) or parallel to the axis of distraction (group II). The effects of device orientation during osteodistraction were then analyzed clinically, radiographically, and by dental cast measurements. RESULTS: Distractors oriented parallel to the body of the mandible caused an increase in the anterior width of the proximal mandibular segments. This lateral displacement of the proximal segments led to several clinical complications, including screw fixation failure and bone resorption under the fixation plates. These effects were minimized when the device was oriented parallel to the axis of distraction. CONCLUSIONS: Device orientation plays an important role when applying distraction osteogenesis in a clinical setting. Although other intrinsic and extrinsic factors affect the success of osteodistraction, the devices should be oriented parallel to the axis of distraction to minimize adverse biomechanical effects during bilateral mandibular lengthening.

Animals↗

[Class II malocclusion. Time and cost of a combined orthodontic and surgical treatment].

During orthodontic treatment of 29 patients with a Class II malocclusion, the remaining overjet was corrected surgically by intraoral mandibular distraction osteogenesis. The patients were divided in two groups. Group A was treated orthodontically in a two-phase approach, using functional and fixed appliances. Group B was treated in a one-phase approach with only fixed appliances. Before treatment the differences in age, gender and severity of the malocclusion between the groups, were not statistically significant. After distraction-osteogenesis, all orthodontic treatments could be finished successfully. The mean treatment time was for group A 44.2 and for group B 28.6 months. The difference was statistically significant (p < 0.001). The mean orthodontic treatment time after distraction osteogenesis was 9.1 months. The mean cost for the orthodontic treatment was not statistically significant different between the groups.

Adolescent↗

[Micro- and macrodistraction of the jaw. A sure method of adding new bone].

Vertical distraction osteogenesis (VDO) has been developed by our study group to move dentulous and edentulous segments of the alveolar process vertically with a device in microplate-design. Besides these techniques of vertical distraction of the atrophic alveolar crest some further modifications as Micro- and Macro-distraction are available. Micro-distraction can be used in localised small defects of the alveolar crest with microplates and screws of 1.0 mm in diameter. In a pilot study we could treat 6 patients especially after traumatic bone loss of the alveolus. The lengths of the segments were 12.6 mm, the vertical distraction rate was 9.2 mm in average. Macro-distraction we call the distraction of the severely resorbed mandible in order to rebuild the vertical dimension of the weakened mandible. Vertical distraction osteogenesis of 13.6 mm was completed successfully in five patients with large segments of 119 mm lengths in average in a sandwich-technique. With a solid 2.3 basic plate a secure stability of the weakened mandible could be achieved. In contrast to bone transplantation an earlier mineralisation in the vertically distracted area could be seen by radiological examination and biopsy. We could insert dental implants in both pilot groups 3 months after distraction procedure. Main advantages of vertical distraction osteogenesis are: 1. No bone harvesting, 2. decreased resorption, 3. lower morbidity compared with conventional techniques, 4. lower infection rate and 5. feasibility to insert dental implants 3 months after distraction procedure, 6. gain of soft tissue.

Adolescent↗

[The value of methods of bone regeneration evaluation in limb lengthening by the Wagner, Ilizarov methods and by physeal distraction].

Limb lengthening is a long-lasting process, and during new bone formation different complications may occur. Due to this, early diagnosis of disturbances of new bone formation leading to such complications is of importance. The goal of this study is to analyze already used methods of regenerate evaluation. Material consists of retrospective data of 237 patients, who underwent limb lengthening between 1983 and 2002 by one of three methods: Wagner method, Ilizarow method and physeal distraction. During femoral lengthening by Wagner method appropriate shape of regenerate according to Hamanishi was observed in 9 cases (29.0%), and during tibia lengthening--only in 1 case (6.7%). During femoral lengthening by physeal distraction appropriate shape of regenerate (A or B according to Hamanishi) was observed in 24 cases (77.4%), and during tibia lengthening--in 11 cases (78.6%). During femoral lengthening by Ilizarow method appropriate shape of regenerate was observed in 51 cases (72.9%), and during tibia lengthening--in 46 cases (66.7%). Only in Wagner method a correlation between abnormal regenerate shape and bone consolidation complications was noted. Methods of evaluation of bone regeneration during distraction osteogenesis give only descriptive assessment. So far parameters applied for evaluation of distraction osteogenesis in Ilizarow method and physeal distraction do not allow for detailed assessment of bone regeneration process.

Adolescent↗

Distraction rate and latency: factors in the outcome of pediatric mandibular distraction.

BACKGROUND: Distraction osteogenesis was initially devised as a way to lengthen the lower extremity. All the basic tenets of the technique were developed based on this use. This includes both the supposed need for a latency period before distraction begins (3 to 5 days) and the ideal rate of distraction (1 mm/day). There is no evidence that these values apply to craniofacial distraction osteogenesis, particularly in children. Indeed, with the markedly improved blood supply in the face when compared with the lower extremity and the use of the technique in children versus adults, one might assume that a shorter latency period and a more rapid rate of distraction are possible. METHODS: This study is a retrospective review of 22 pediatric patients with mandibular hypoplasia undergoing mandibular distraction osteogenesis. All patients were operated on by a team consisting of an oral surgeon and a plastic surgeon. All the distraction devices used were external. All patients had a latency period, before activation, of less than 24 hours and a distraction rate of 2 mm/day. RESULTS: Two patients developed cellulitis at the pin sites, one patient developed premature healing, one patient developed a nonunion that required further surgery. This was the only patient in the series who had distraction of a previous bone graft. No patient undergoing distraction of native mandible developed a nonunion. CONCLUSIONS: Eliminating the latency period and rapidly distracting the mandible in pediatric cases has an acceptably low complication rate. This benefits the patient in terms of an overall reduction in the amount of time that the child needs to remain in the distraction device. The patient spends less time with the distraction device, thus reducing the potential morbidity and increased cost of the treatment. Potential explanations for why this variation in distraction technique is successful include the improved blood supply in the face of children and the failure of external devices to translate all the distracted movements to the bone interface. Some of this force is translated into both bending of the pins and migration of the pins through bone. Although a latency period might be necessary in the distraction of the lower extremities, the application of this concept to the craniofacial skeleton in children is erroneous.

Age Factors↗

Internal mandibular distraction to relieve airway obstruction in infants and young children with micrognathia.

Micrognathia may cause upper airway obstruction requiring complex medical interventions and sometimes tracheostomy. The role of distraction techniques to lengthen the mandible is yet to be clarified. The aim of this paper is to present a series of five cases in which mandibular lengthening by osteotomy and internal distraction was used to relieve airway obstruction. Five patients whose ages ranged from 4-39 months (mean, 15 months) were managed at our center with internal distraction osteogenesis to relieve airway obstruction. Three patients had a tracheostomy, and two patients had refractory airway obstruction prior to distraction. Following osteotomy and insertion of internal distraction devices, the mandible was distracted a mean of 17 mm (range, 15-25 mm). The distraction devices were removed at the end of a consolidation period ranging from 3-10 weeks. Two of 3 patients with a tracheostomy were decannulated, while the third patient with tracheostomy is awaiting choanal atresia repair before being decannulated. The two patients who were not managed with a tracheostomy but who had persistent upper airway obstruction have not required further airway intervention after mandibular distraction. In conclusion, mandibular lengthening by distraction osteogenesis can relieve airway obstruction in infants and small children. This is a promising new technique that may avoid the need for tracheostomy in some infants with micrognathia, and facilitate early decannulation in those who have a tracheostomy.

Airway Obstruction↗

Effect of distraction rate and consolidation period on bone density following mandibular osteodistraction in rats.

The high cost of large animal protocols has limited the study of distraction osteogenesis (DO) in the craniofacial region. This study was designed to characterise a rat model for DO with regard to distraction rate and consolidation period. Unilateral mandibular distraction was performed on 129 male Sprague-Dawley rats using an osteotomy from the sigmoid notch to the inferior border of mandible. After a 3-day latency, 12 groups of 8-9 rats underwent distraction for 5 days at four different rates (0, 0.2, 0.4, 0.6mm per day), with three different post-osteotomy sacrifice times (10, 24, and 38 days) and four final predicted distraction lengths (0, 1, 2, and 3mm). Another four groups of rats (N=8 per group) were sacrificed 6 days post-osteotomy, resulting in distraction for 3 days with a predicted distraction length of 0, 0.6, 1.2, 1.8mm. Changes in mandibular morphology were measured from radiographs of disarticluated hemimandibles. The bone density of the regenerate and control sites was measured using microdensitometry calibrated with an epoxy stepwedge. Distraction linearly increased mandibular length, distraction gap width and the area of the distraction gap (P<0.00005). Mandibular length increased by 0.394 mm per distraction rate. Gap width and area increased by 0.67 and 5.8mm(2) per distraction rate, respectively. The increase in length represents only 39.4% of what was predicted, suggesting that compensatory alteration in condylar or mandibular morphology may have occurred. This speculation was further supported by the finding that mandibular length, measured without the condylar landmark, was 53.8% of predicted. During DO and early consolidation, the measures of bone density in the regenerates decreased compared to control for all groups. Thereafter, bone density in the regenerates generally increased in all groups until day 24 (P<0.01), obtaining levels that were comparable to the unoperated side. At both rostral and caudal sites adjacent to the osteotomies, measures of bone density were enhanced over control in all groups, with the rostral site also showing significant increases over time in the sham and the highest distraction groups (P<0.008 and P<0.014). We conclude that this rat model for mandibular distraction osteogenesis provides bone density changes that are consistent with those reported using larger animal protocols.

Analysis of Variance↗

[Electron radioautographic study of osteogenesis during distraction osteosynthesis].

Electron microscopic radioautography was used to study the osteogenesis during the replacement of bone tissue defects by graded distraction osteosynthesis in 12 patients with open fractures of the tibia. In the early stages of reparative tissue formation, the cells that intensely synthesized DNA and DNA were located exceptionally in the vascular walls or near them. The authors assume that vascular cells, most probably pericytes, are a basic source of the origin of the reparative tissue, turning firstly to fibroblast-like cells and then to osteoblasts.

Autoradiography↗

New technique for airway correction in neonates with severe Pierre Robin sequence.

To avoid tracheostomy in 11 neonates with severe Pierre Robin sequence, we used a technique of progressive elongation of the mandible (distraction osteogenesis) to correct tongue ptosis, increase pharyngeal airway, and correct micrognathia. All 11 patients were extubated within 3 to 6 days after beginning distraction. At 1 month 54.5% were oral feeders and at 1 year, 100%. Sleep studies were obtained on 7 patients and were normal 1 week to 1 month after operation. Growth was observed to be above the 50th percentile in all patients with no comorbidities. A 5-year clinical follow-up showed the operated mandible to maintain a normal shape and produce an undisturbed tooth eruption sequence. We conclude that distraction osteogenesis to increase the length of the short mandible is an effective alternative to tracheostomy in carefully selected patients.

Airway Obstruction↗

[Ultrastructural and Ca/P changes of the regenerated bone after mandibular distraction in goats].

OBJECTIVE: The aim of this study was to examine the ultra structural and the changes of Ca/P elements of the new bone resulting from mandibular distraction osteogenesis. METHODS: Bilateral mandibular osteotomies were performed in six goats. The mandibles in all animals were lengthened 10 mm using a custom made distracter. Each 2 goats were sacrificed respectively at 2, 4 and 8 weeks after completion of distraction. The distracted callus were harvested and processed for SEM evaluation and Ca/P ratio analysis. RESULTS: The newly generated bone in distraction gap was confirmed by SEM examination, and the contents of Ca, P were found to be elevated with the maturity of distracted callus. CONCLUSION: This study suggested that newly formed bone by mandibular distraction osteogenesis in goats could be remodeled to normal bone.

Animals↗

[Application of Ilizarov method in maxillofacial treatment].

Distraction osteogenesis is becoming the treatment of choice for the surgical correction of hypoplasias of the maxillofacial skeleton. The mandible can be elongated by intraoral or extraoral devices. The intraoral devices are smaller, do not leave an external scar and do not cause social inconvenience to the patient. The main disadvantages are less control of vector and the need for a second operation for removal. The most important factors of mandibular distraction are planning of distraction, location of the osteotomy, control of vector of lengthening and type of distraction device. In the maxilla, our experience with three types of maxillary distraction is discussed: 1) the rigid extraoral distraction, 2) the surgically assisted protraction and 3) the intraoral method. In the last years, distraction osteogenesis was applied in the treatment of obstructive sleep apnea. The method has several advantages over other methods, mainly in treatment of young children in order to improve airway and to decannulate tracheostomy. Alveolar distraction osteogenesis poses a new challenge in reconstructing atrophic alveolar bone with no need to harvest bone graft or to use bone substitutes. The advantages and problematic issues of alveolar distraction such as vector control of distraction are described. The intraoral method should always be considered first. However, in severely hypoplastic patients, when three-dimensional correction is necessary, the extraoral device has an advantage over the intraoral device. In the future, the issues to consider will be improvement of osteotomies by endoscopy, development of smaller multidirectional devices, improvement of bone quality by cytokines and growth factors in order to shorten the time of device bearing by the patients.

Facial Bones↗

Mandibular growth after distraction in patients under 48 months of age.

Distraction osteogenesis is an effective technique for reconstruction of the congenitally deficient mandible. However, the age at which it is best performed remains under discussion. Distraction performed at an early age, while possibly allowing the face to develop with a more normal functional matrix, may entail a higher rate of complications. Additionally, it is possible that subsequent asymmetric growth of the mandible may necessitate serial distraction. To address this issue, the clinical records and cephalometric radiographs of all patients less than 48 months of age undergoing mandibular distraction at New York University Medical Center between August of 1989 and August of 1997 were examined. There was a total of 14 patients ranging in age from 19 months to 43 months. Nine patients had a diagnosis of unilateral craniofacial microsomia, three had Treacher Collins syndrome, one had Nager syndrome, and one had bilateral developmental micrognathia. The average amount of distraction was 27 mm (range, 23 to 39 mm) in unilateral cases and 24 mm in bilateral cases (range, 15 to 31 mm). The period of clinical follow-up averaged 32.6 months (range, 12 to 92 months). All patients showed significant improvement in craniofacial appearance, and in four patients, long-term tracheostomy tubes were removed. There were two major complications. In one patient with craniofacial microsomia, there was a relapse in the early postretention phase related to the presence of a dentigerous cyst. This required removal of the cyst and repeat distraction. In the patient with Nager syndrome, a coronoid ankylosis developed requiring surgical release. There were no other major complications. The scars required revision in only two of the patients. Cephalometric analysis of the patients in the study revealed a differential in the rate of growth between the affected and the unaffected side in all cases of craniofacial microsomia. The affected side always grew at a slower rate than the contralateral side after the distraction process was complete. This led to a progressive asymmetry of the rami, clinically expressed by some degree of facial asymmetry and an occlusal cant. For this reason, secondary distraction was required in one patient and is planned in a second. Initial overcorrection of the patient would seem to minimize the likelihood that secondary distraction will be necessary. Distraction osteogenesis for reconstruction of the mandible in this subset of young patients was a safe and effective technique for improving the craniofacial skeletal form and appearance, with minimal associated morbidity. Longer follow-up is necessary to assess the full impact of growth in these cases.

Child, Preschool↗

Cavitary osteomyelitis treated by fragmentary cortical bone transportation.

Fragmentary cortical bone transportation can be used to fill large gaps in chronic cavitary osteomyelitis when standard techniques have failed. A low-energy corticotomy can create a loose fragment of cortex with periosteal attachments and surface blood supply still intact. This "vital" fragment can be gradually pulled across a defect within a bone to restore the integrity of the bone segment by distraction osteogenesis. The biologic principles for successful distraction osteogenesis by this innovative technique are illustrated in a 41-year-old man with chronic cavitary (150 cc) (four years) osteomyelitis refractory to multiple debridements, Papineau grafting, gentamicin beads, and tricalcium phosphate.

Adult↗

[Maxillary distraction and implantology].

Vertical alveolar distraction can be a useful surgical technique in preprosthetic reconstructive surgery, especially after failed autogenous onlay bone grafting. The main advantage of this technique is to allow expansion of both the bone and soft tissue. Through a case of vertical alveolar reconstruction by distraction osteogenesis and implant rehabilitation in a patient who had undergone two previously unsuccessful interposition bone graft procedures, this report illustrate the advantages of alveolar ridge augmentation by distraction osteogenesis.

Aged↗

Skeletal volume enhancement: implants and osteotomies.

PURPOSE OF REVIEW: Facial plastic surgeons are concerned with improving or restoring function and form. Most surgeons perform primarily soft tissue procedures, which alone are often sufficient. However, deficiencies in the underlying craniomaxillofacial skeleton must also be addressed. Facial skeletal augmentation remains an essential aspect of cosmetic and reconstructive surgery. This article reviews the basic alloplastic biomaterials available for facial volume enhancement, discusses the zygomatic sandwich osteotomy for malar augmentation, and describes recent applications of distraction osteogenesis in the craniomaxillofacial region. An update in tissue engineering and computer modeling is also provided. RECENT FINDINGS: High-porosity expanded polytetrafluoroethylene has been developed to provide a softer feel with less shrinkage and migration because of better biointegration and cellular ingrowth. Long-term results with porous polyethylene have demonstrated superior biocompatibility and minimal complications. Hydroxyapatite cement has been associated with an immunoguided delayed inflammatory reaction that leads to thinning of the overlying skin and exposure of the implant.Applications of distraction osteogenesis are rapidly expanding and include deformities of the mandible, midface, and cranium. There has been a trend toward the use of internal hardware, and internal devices are being developed to deliver a greater degree of vector control. Biodegradable devices have been developed to eliminate the second surgical procedure necessary for hardware removal. In the future, successful tissue engineering could eliminate many of the drawbacks associated with implants and osteotomies. The ability to stimulate stem cells to generate autogenous bone has been demonstrated in the laboratory. A novel application of computer technology that integrates laser surface scanning and digitizing with computer-aided design and manufacturing to produce facial prostheses has been described. SUMMARY: An abundance of alternatives exist for skeletal volume enhancement including alloplastic implants, standard osteotomies, and distraction osteogenesis. The surgeon must evaluate the pros and cons of each technique in the context of each individual patient to determine the most appropriate option. Technologic advances in biomaterials, distraction hardware, computer modeling, and tissue engineering will continue to supply the surgeon's repertoire with improved methods to augment and restore the craniomaxillofacial skeleton.

Absorbable Implants↗

Advancement of the anterior maxilla by distraction (case report).

INTRODUCTION: Several techniques of distraction osteogenesis have been applied for the correction of compromised midface in patients with clefts of the lip, alveolus and palate. PURPOSE: This article presents a technique of callus distraction applied in a specific case of hypoplasia of a cleft maxilla with the sagittal advancement of the maxilla thus not affecting velopharyngeal function. CONCLUSION: The decision to apply distraction osteogenesis for advancement of the anterior maxillary segment in cleft patients offers many advantages.

Adult↗

[Bidirectional and unidirectional distraction of defects of the alveolar process comparative clinical study].

AIM: The purpose of the retrospective study was to compare bidirectional distraction osteogenesis with the currently used unidirectional method of alveolar ridge distraction with regard to bone height attained and complications. PATIENTS AND METHODS: Overall 21 patients were treated by distraction osteogenesis for localized defects of the alveolar ridge. Vertical augmentation of the mandible and maxilla was performed using 10 unidirectional (group A) and 12 bidirectional (group B) devices. The effect of therapy was evaluated by height of bone gain and observed complications. RESULTS: The average gain of vertical bone height was approximately 6 mm. No statistically significant differences occurred between the two treatment groups (p=0.09). For the entire study two complications were observed: beside breakage of a distractor device (unidirectional distraction) an infection during the retention time (bidirectional distraction) developed. CONCLUSIONS: It could be shown that osteodistraction is a potentially valuable therapy for the correction of alveolar defects. We observed complications in both groups. No statistical differences were noted in regard to gained bone height and complications between the two groups.

Adult↗

Mandibular distraction lengthening in the severely hypoplastic mandible: a problematic case with tongue aplasia.

Distraction lengthening is a technique that was initially developed for correction of lower limb length discrepancies. It has recently been adapted to maxillofacial problems and has gained increasing popularity in this application. This report illustrates the principles involved in mandibular distraction lengthening and offers possible solutions to potentially limiting clinical problems. First, conventional technique dictates that a distinct periosteal sleeve is necessary for distraction osteogenesis to occur. However, in this case, distraction was performed through an area of scar tissue in which the native periosteum was destroyed. The ability to extend the use of the technique of distraction successfully to suboptimal clinical situations may broaden the indications for its use. Second, fixator instability is a potentially common problem in these cases because of the forces involved in distraction osteogenesis and the duration of the process. However, mechanical rigidity is essential consolidation (typically requiring twice as long as the distraction phase). Fixator instability can be successfully salvaged during the mineralization phase of bony healing through the use of an onlay corticocancellous bone "plate," which resorbs as the distraction gap gains strength. This report highlights one of the main advantages of the distraction process: the expansion of the soft-tissue matrix of the face.

Airway Obstruction↗