Unilateral Distraction Osteogenesis Research Articles

Morphologic and Aerodynamic Changes of Upper Airway in Pediatric Hemifacial Microsomia Patients Undergoing Distraction Osteogenesis.

Current studies on hemifacial microsomia (HFM) patients undergoing unilateral distraction osteogenesis (DO) mainly confined to description of facial morphology. This study was to investigate the effect of unilateral DO on upper airway in pediatric HFM patients using computational fluid dynamics. The investigators implemented the present retrospective study composed of 20 patients (age 9.5 ± 2.5 years, 11 males, 9 females) with moderate HFM performed unilateral DO on the ramus of mandible. Computational fluid dynamics models of the upper airway were obtained based on the computed tomography data sets which were taken before and 6 months after distraction. Morphologic and aerodynamic parameters were respectively computed and compared at peak inspiration. Paired t-tests were used to compare the differences between the before and after parameters with the significance set at P < 0.05. The authors observed that after DO, oropharynx and nasopharynx were the major expanded regions, average pressure increased in all cross-sections, average velocity decreased significantly except in the superior border of the epiglottis plane, and the airflow resistance significantly reduced in the whole upper airway (P < 0.05). The results indicate that unilateral DO may expand the constricted oropharynx and nasopharynx, obtain a relatively symmetrical airway shape and decrease the airflow resistance which consequently reduce the workload necessary for breathing and facilitate inspiration.

Changes in Soft Tissue Measurements After Mandibular Distraction Osteogenesis.

Mandibular distraction osteogenesis is the process of generating new bone in a gap between 2 bone segments in response to the application of graduated tensile stress across the bone gap. These distraction forces applied to bone also create tension in the surrounding soft tissues resulting in simultaneous expansion of the functional soft tissue matrix. To investigate and evaluate the changes in facial soft tissue following mandibular distraction osteogenesis and their relationship with the changes in bone movements. Mandibular elongation of 13 patients was done by the use of bilateral distraction osteogenesis in 10 patients and unilateral distraction osteogenesis in 3 patients, soft tissue evaluation was done by measuring 4 facial lines (tragus-commissure of mouth, lateral canthus-commissure of mouth, medial canthus-commissure of mouth, and lower lip length). The measurements were done by the use of measurement tape preoperatively and after the consolidation period. Soft tissue changes were observed in all patients. There was highly significant increase in tragus-commissure line in all patients, significant increase in lateral canthus-commissure line in 10 patients, and significant increase in medial canthus-commissure line and lower lip length in 9 patients. The lines' relation with the overjet was highly significant in right side of tragus-commissure line, lateral canthus-commissure line, medial canthus-commissure line, and lower lip length, and significant in left side of tragus-commissure line, lateral canthus-commissure line, and medial canthus-commissure line CONCLUSION:: Distraction osteogenesis has recognizable effect on facial soft tissue profile in addition to its effect on skeletal structure.

Effect of unilateral mandibular distraction osteogenesis on mandibular morphology in rabbits with antigen-induced temporomandibular joint arthritis

Aim was to evaluate effect of unilateral distraction osteogenesis (DO) on mandibular morphology in rabbits with antigen-induced arthritis in the temporomandibular joint (TMJ). Forty 8-week-old rabbits were divided into four groups. In groups A,C, arthritis was induced in the right TMJ. Groups A,B underwent DO. Group D served as control group. Cephalometric analysis of mandibular angle, mandibular ramus height, mandibular collum height, and total posterior mandibular height was done on CT-scans preoperatively (T0), after distraction (T1), and at euthanasia (T2). Two-factor ANOVA evaluated the effect of DO and antigen-induced arthritis. No effect of DO or arthritis was observed on mandibular angle or mandibular collum height. For T0–T1, DO increased mandibular ramus height 12.3% (95% CI 5.2–19.4%) in group B (P=0.001) and total posterior mandibular height 6.2% (95% CI 0.3–12.1%) in group A (P=0.04) and 10.0% (95% CI 4.3–15.7%) in group B (P=0.001). For T1–T2, no significant changes occurred in arthritic rabbits (group A). In conclusion, DO increased total posterior mandibular height in rabbits with arthritis. Postoperatively, no significant effect of DO was observed in rabbits with arthritis. Mandibular DO could be a viable treatment modality in patients with TMJ-arthritis.

Mandibular distraction combined with orthognathic techniques for the correction of severe adult mandibular hypoplasia.

Mandibular hypoplasia may result from congenital deformities or trauma or infection during the early stage of facial skeleton development. Deficiencies in the growth of the mandible can not only cause various degrees of facial deformity but also affect breathing and occlusal function. Here, we report our experiences with mandibular distraction combined with orthognathic surgical techniques for the treatment of severe adult mandibular hypoplasia. Cephalometric analysis was conducted in all patients for quantitative evaluation. A computer-assisted surgical simulation was prepared before distraction. According to the simulation data, an operative osteotomy guide plate was designed and three-dimensionally printed with photosensitive resin. With the help of the guide plate, the osteotomy line was precisely placed. An internal distractor was then placed through an extraoral incision created under general anesthesia. Distraction began after 7 days of latency at the rate of 1 mm/d. After a 6- to 8-month consolidation period, the distractor was removed. At the same time, genioplasty and/or subapical osteotomy was performed to correct the patient's crossbite and improve the facial contour for bilateral mandibular hypoplasia. For unilateral mandibular hypoplasia, a Le Fort I osteotomy was performed to correct the open bite on the affected side, whereas a mandibular outer cortex excision was performed on the unaffected side to improve lower facial symmetry. The mandible symmetry and chin protrusion were efficiently improved in all 36 patients (mean age, 20.3 y). No facial nerve palsy was reported, nor were there complaints about postoperative facial scarring. The postoperative infection rate was 2.8%. The distance of lengthening was 26.2 (2.8) mm. The increased ramus length on the affected side was 18.9 (9.3) mm. At the end of the consolidation period (T2), the affected mandibular ramus length increased by 46.3% (23.6%) in unilateral distraction osteogenesis; however, it decreased by 18.6% (12.4%) after device removal (T3). For bilateral distraction osteogenesis, condylion-gonion increased by 34.0% (50.0%) in T2 but had no significant change in T3. Complicated mandibular hypoplasia can be well corrected with mandibular distraction combined with orthognathic surgery.

Surgical Correction of Hemifacial Microsomia: Simultaneous Orthognathic and Distraction Osteogenesis Treatment. A Case Report on How This Hybrid Technique Can Correct Severe Facial Asymmetries

Hemifacial microsomia (HFM) is one of the most common congenital craniofacial soft and hard tissue deformities, manifesting as a unilateral underdevelopment of anatomical structures arising from the first and second brachial arches. The most salient feature is the underdevelopment of the mandible, particularly the ramus and condyle. Developmental disturbances at various times can lead to numerous presentations in size and function, which might require different treatment options. Conventional therapy for asymmetric patients with severe forms of HFM has been unilateral distraction osteogenesis. However, there has been noted relapse into facial asymmetry due to contraction of the bony segments and a lack of downward growth. With regard to avoiding such complications, we have elected to utilize both the distraction osteogenesis method and traditional orthognathic surgery, allowing us to better control vector movement of the maxillary and mandibular segments. It is our goal that by demonstrating this technique on such an extreme case of HFM, we can show that both methods can be used simultaneously to successfully correct this deformity, whereas each one individually might not have.

A Comparison of Stromal Cell-Derived Factor-1 Expression During Distraction Osteogenesis and Bone Fracture in the Mandible

Distraction osteogenesis (DO) has been a widely applied technique in orthopedics and craniofacial surgery. However, the exact molecular mechanism by which the mechanical stimulus is translated into biological signals is still poorly understood. In this study, we examined and compared the expression of stromal cell-derived factor-1 (SDF-1) during mandibular distraction osteogenesis and fracture in rats, respectively. Forty-eight male Sprague-Dawley rats were divided into 2 groups and received unilateral distraction osteogenesis and rigid internal fixation, respectively, after the osteotomy on the right mandible. The harvested mandibles were examined radiographically, histologically, and immunohistochemically. We found that the expression of SDF-1 was mainly detected in the osteoblasts and blood vessels, and there were more intensive expression of SDF-1 in DO zones than in bone fracture zones. The quantitative analysis by enzyme-linked immunosorbent assay showed that SDF-1 reached a greater peak and maintained a longer period of up-regulation in DO than in fracture healing (P < 0.05). These results suggest that the distraction procedure markedly promotes the high expression of SDF-1 which facilitates the induction of bone formation during DO.

New Approach for the Surgico-Orthodontic Treatment of Hemifacial Microsomia

One of the important clinical findings in hemifacial microsomia (HFM) is facial asymmetry (FA) with unilateral underdevelopment and malformation of the mandible and/or maxilla. Unilateral distraction osteogenesis (UDOG) of the mandible has been used for correction of FA in HFM patients. However, return to the original FA status often occurs because of contraction of the distracted bony segment of the mandible and insufficient compensatory downward growth and skeletal midline correction of the maxilla on the affected side. Although bimaxillary UDOG procedure in the maxilla with Le Fort I osteotomy and the mandible with ramus osteotomy was suggested as an alternative treatment modality, it has some disadvantages including elongation of the face, inaccuracy of vector control, and less predictable results. Occlusal plane canting, skeletal midline deviation of the maxilla, and unilateral mandibular hypoplasia might be simultaneously corrected by fixation of the maxilla into a proper position after Le Fort I osteotomy and UDOG of the mandible. Three-dimensional virtual simulation using three-dimensional computed tomography data could help to accurately predict surgical outcomes. In addition, transarch elastic traction from the orthodontic mini-implants on the unaffected side of the mandible to the maxillary posterior teeth on the affected side can produce a plastic molding of the regenerated bone in the distraction area of the mandible and induce compensatory dentoalveolar downward development of the maxillary posterior teeth. Therefore, the purpose of this article was to introduce a new approach for the surgico-orthodontic treatment consisting of simultaneous maxillary fixation and unilateral mandibular distraction with transarch elastic traction in HFM patients.

Mandibular Distraction Osteogenesis in 23 Patients With Juvenile Idiopathic Arthritis

Statement of the Problem: Juvenile idiopathic arthritis (JIA) is a chronic inflammatory disease occurring before the age of 16. The temporomandibular joint is frequently involved and this can result in growth impairment of the mandible with an asymmetric growth in cases of unilateral involvement. In severe cases, conventional orthognathic surgery has a risk of relapse, and in an attempt to avoid this we have used distraction osteogenesis (DO) in a group of JIA patients. Only few publications have described the use of DO in JIA patients. Materials and Methods: Twenty-three patients with JIA underwent unilateral distraction osteogenesis. There were 14 females and 9 males. Mean age was 16 years (range 11-34 years). All patients were treated according to a standardized protocol with preoperative orthodontic planning, cephalometric analysis with calculation of distraction vector, and transfer of the vector to the surgical procedure. An occlusal splint was used full-time during distraction. Data from five examinations of symptoms and function were included in this study: T1: before distraction osteogenesis, T2: after removal of distraction device, T3: 6 months after DO, T4: 12 months after DO, and T5: the latest follow-up visit. Radiographic evaluation was performed by comparing the normal and the affected side on frontal and lateral cephalograms and orthopantomograms. Methods of Data Analysis: Data describing the functional status was analyzed by descriptive statistics. The results from the cephalometric analysis before and after treatment were compared by paired t-test by use of SPSS 18.0 for Windows. Results of Investigation: Subjective: TMJ function was good both before and after distraction osteogenesis and nearly all the patients reported normal chewing and opening capacity. Pain related to TMJ arthritis was reduced after treatment (5 patients before, none after) in contrast to muscle pain and muscular headache which were more frequent at long-term follow-up. Objective: The mandibular asymmetry was corrected. The lip function was improved and the respiratory pattern was normalized for most of the patients. A tongue dysfunction was present in eight patients before treatment and in two patients at follow-up. The dental occlusion was normalized for all but 2 patients, who still had a distal molar relationship. The mandibular range of motion before treatment was 47.6 mm with laterotrusion and protrusion within the normal range. In the early post-distraction period the mobility was significantly reduced but throughout the follow-up period it increased to normal range and close to the preoperative values. Cephalometric analysis demonstrated skeletal stability of the treatment result. Conclusion: The use of DO in patients with previous JIA in the TMJ resulted in a good skeletal and occlusal stability. It appears that good function of the joints is preserved at long-term follow-up. The affected joint should be guarded by use of occlusal splint during and after the distraction process.

Analysis of the Biomechanical Properties of the Mandible after Unilateral Distraction Osteogenesis

The purpose of this study was to establish biomechanical outcomes measures to evaluate how mandibular distraction osteogenesis affects the overall quality of bone healing. Strength and functional integrity of the regenerate were determined quantitatively after unilateral mandibular distraction osteogenesis in comparison with the contralateral mandible and a partially reduced fracture. The authors hypothesized that the breaking load, yield, and stiffness of mandibular distraction osteogenesis would be significantly reduced in comparison with both the contralateral mandible and a partially reduced fracture. Sprague-Dawley rats underwent mandibular distraction osteogenesis (n = 8) or a partially reduced fracture (n = 6). Distraction was performed using 4 days' latency and then 0.3 mm every 12 hours for 8 days (5.1 mm). Partially reduced fractures had gaps fixed postoperatively at 2.1 mm. Both groups underwent 4 weeks of consolidation. The contralateral mandibles were used as controls (n = 14). Mandibles were tension tested at 0.5 mm/second to failure, and then breaking load, yield, and stiffness were determined. Mandibular distraction osteogenesis had significantly lower breaking load, yield, and stiffness than contralateral mandible, by 40, 30, and 60 percent, respectively. Breaking load was reduced in partially reduced mandibular fractures by 40 percent when compared with distraction osteogenesis. Using a standard Ilizarov protocol, the biomechanical properties of breaking load, yield, and stiffness in mandibular distraction osteogenesis were significantly lower than those in contralateral mandibles. Surprisingly, the breaking load of mandibular distraction osteogenesis was significantly greater than that of partially reduced mandibular fracture. These verifiable metrics of regenerate integrity can be used to discern optimal outcomes of mandibular distraction osteogenesis, potentially enhancing the clinical applications of this powerful technique.

Rabbit as a distraction model—pitfalls

The principles of distraction osteogenesis have been successfully applied to the craniofacial skeleton of different animals. The rabbit, in particular, has been evaluated as a model by enumerable authors. To our knowledge, however, none of the studies either report the causes of premature euthanization or the pitfalls leading to the untimely death of the animal. We here describe our experience with 30 rabbits used as a model for mandibular distraction osteogenesis and suggest precautions to take in order to avoid unforeseen problems. Thirty skeletally mature New Zealand white rabbits were used. Fifteen animals had bilateral distraction devices placed on the anterior mandible, and another 15 underwent unilateral distraction osteogenesis. In both groups, 12 animals were euthanized prematurely due to complications that included excessive weight loss (malnutrition), anesthesia/animal-related problems, and distraction device failure. The remaining 18 animals tolerated the operative procedure well. Indisputably, rabbit is an excellent choice for craniofacial experiments, but because of its complex anatomy and physiology, an unexpected outcome frequently occurs. We believe that the following suggestions in relation to the pre-operative selection of a suitable animal model, operative technique, and management of eating problems may help the researcher to choose an appropriate animal and avoid complications leading to early death.

Cephalometric evaluation of the craniofacial complex in patients treated with an intraoral distraction osteogenesis device: A long-term study

Distraction osteogenesis has gained popularity because of the hypothesized concurrent soft-tissue expansion, which is believed to reduce postoperative relapse. Although many articles describe the immediate success of mandibular distraction, little research has been done on its long-term stability. Our goal was to examine the long-term craniofacial changes after distraction. Four hemifacial microsomic patients treated with unilateral mandibular distraction were recalled. Changes in maxillary width and height, occlusal height, ramus height, mandibular length, and chin position were quantified by using the posteroanterior and 45 degrees lateral oblique cephalographs. Predistraction and postdistraction measurements were taken over a 5-year period. The data were analyzed by using paired t tests and ANOVA. Maxillary height, ramus height, mandibular length, and chin point deviation all experienced moderate improvement after distraction. Although the growth patterns between the control side and the treated side were comparable until 2 years after removal of the device, the normal side outgrew the affected side thereafter until 5 years after distraction. Because of the greater inherent growth potential of the unaffected side, more overcorrection than originally believed is needed to offset the persistent asymmetry in growing hemifacial microsomia patients who undergo unilateral distraction osteogenesis.

Comparison of Skeletal and Soft-Tissue Changes following Unilateral Mandibular Distraction Osteogenesis

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 medical photographs, respectively. To reduce magnification error, ratios of affected to less affected sides of the mandibles and soft-tissue facial structures were selected and studied. A similar relationship was observed between soft-tissue and skeletal components. However, there was no 1:1 relationship between the changes in ramus height and improvement in parallelism of lip commissures to the orbital plane. A significant improvement in soft- and hard-tissue anatomy has been observed following unilateral distraction osteogenesis of the mandible. The relationship between the soft-tissue and skeletal correction was different for all patients because of the large range in severity of the craniofacial malformation. Greater skeletal deficiency requires more correction to achieve symmetry of both hard and soft tissue.

Does functional appliance treatment truly improve stability of mandibular vertical distraction osteogenesis in hemifacial microsomia?

After mandibular unilateral distraction osteogenesis (DO) a gradual reappearance of the vertical asymmetry during growth is observed. A pre- and post-surgical functional-orthodontic treatment was added to our distraction protocol in the attempt to increase long-term stability. In order to evaluate the actual efficacy of such a combined treatment, two samples of children affected by hemifacial microsomia were compared long-term. Ten children were treated by a combined orthodontic-distraction treatment, seven by distraction only. Only the vertical changes in the mandible and maxilla in the panoramic and postero-anterior cephalometric X-rays were measured. All of the patients showed a gradual return of the asymmetry with growth. Occlusal plane correction and, to a much lesser extent, mandibular vertical ramus height correction were better maintained over 5 years post-DO in the orthopaedic group. Although orthopaedic treatment allows for a more stable occlusal plane and for a slower return of the mandibular vertical asymmetry, it has mainly a dento-alveolar effect. Therefore, the decision of applying an orthopaedic treatment associated with distraction, should be taken by surgeon and orthodontist together, considering both the advantages and the disadvantages of this treatment.

Correlation of immunohistochemical characteristics of the craniomandibular joint with the degree of mandibular lengthening in rabbits

Purpose This study examined immunohistochemical changes in the craniomandibular joints of rabbits after distraction osteogenesis following mandibular corticotomy. Materials and methods The experimental animals (n = 8) were divided into 3 groups that underwent 2, 3.5, and 5 mm of unilateral distraction osteogenesis (groups 1, 2, and 3, respectively). After corticotomy of the left mandibular body and a 7-day healing period, a second operation was performed to expose the device. Distraction was then performed at the rate of 0.5 mm/d. A 14-day consolidation period was allowed after the distraction was complete. Changes in cartilage, osteoblast activity, and osteoclast activity were then examined. Results The differentiation and proliferation of cartilage increased in groups 1 and 2, were highest in group 2, and decreased in group 3. Group 2 also showed the greatest increase in the width of the hypertrophic chondrocyte layer. Relative to the control group, osteoclast activity was only somewhat higher in groups 1 and 2 but was significantly higher in group 3. Osteoblast activity was significantly higher in groups 1 and 2 than in the control group. However, the osteoblast activity in group 3 was slightly lower than that in group 2. At the time of unilateral mandibular distraction, no degenerative changes of the temporomandibular joint were observed in groups 1 or 2, but bone resorption was observed in group 3. Conclusions The unilateral mandibular distraction of 2 or 3.5 mm was acceptable in that no degenerative changes of the temporomandibular joint were observed on either the distraction or the nondistraction sides. Five millimeters of distraction might be beyond physiologic limits.