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PubMed2005

Distraction osteogenesis after irradiation in a rabbit model.

BACKGROUND: The present study was performed to investigate the effects of preoperative irradiation on distraction osteogenesis, as little is known about how preoperative irradiation delays distraction osteogenesis. METHODS: A single dose of irradiation was applied to the right rear legs of rabbits. This was followed by tibial lengthening at a rate of 0.5 mm/day, which was continued for 4 weeks. Bone regeneration was examined radiographically and histologically. RESULTS: In the irradiation group, the radiographs showed little regeneration during the elongation phase. During the maturation phase, the callus appeared slowly, and its formation was spotty. Furthermore, regeneration was not completed until the fourth week of the maturation period. Histological examination at the end of distraction showed a gap in the distraction consisting of loose connective tissue, with part of the fibrous tissue oriented longitudinally. Four weeks after completion of distraction, the major part of the radiolucent region consisted of cartilage. The spotty osteogenesis was identified as enchondral ossification. Immunohistochemical examination of the regeneration area revealed that the blood vessels were extremely localized, and that the level of expression of vascular endothelial growth factor (VEGF) in the osteoblasts was high. Microangiography showed that vascularization at the distracted sites was poor. Distraction osteogenesis was decreased markedly by preoperative irradiation in terms of both rate and process. The results suggested that most of the osteoprogenitor cells were damaged immediately after irradiation. The high level of VEGF in the osteoblasts and the enchondral ossification also suggested a hypoxic state in the distracted region. CONCLUSIONS: Preoperative irradiation interferes with distraction osteogenesis by inducing a state of poor angiogenesis.

Angiography↗

PubMed2003

Distraction osteogenesis for treatment of bone loss in the lower extremity.

Distraction osteogenesis has been widely utilized to treat leg length discrepancy, deformity, nonunion, osteomyelitis, and bone loss. It has been found that most difficult conditions can be resolved with this method. This paper introduces the usefulness of distraction osteogenesis for the treatment of nonunion and bone loss after tumor excision. The procedure was found to be extremely effective for the treatment of nonunion accompanied by bone loss and infected nonunion. In particular, the Ilizarov method offers a simultaneous solution for several problems related to nonunion, such as instability, infection, deformity, bone loss, joint contracture, limb length discrepancy, and skin defects. In addition, distraction osteogenesis is safe, useful, and efficient for the treatment of bone loss even after tumor excision. Joint preservation and reconstruction by means of distraction osteogenesis is the most conservative limb-saving surgery available at present. Furthermore, distraction osteogenesis can provide natural limb regeneration.

Bone Nails↗

PubMed2006

Assessment of cell proliferation during mandibular distraction osteogenesis in the maturing rat.

INTRODUCTION: The cellular mechanisms controlling distraction osteogenesis are not well understood. The purpose of this study was to examine the role of cell proliferation in the regulation of mandibular distraction osteogenesis. METHODS: Unilateral mandibular ramus osteotomies were performed on 125 3-month-old Sprague-Dawley rats. The rats were randomized into 4 distraction rate groups and distracted for 5 days after 3-day latency. Rats (7 or 8 from each rate group) were killed at 4 time points. The rats received 5-bromo-2-deoxyuridine (BrdU) injections (40 mg per kilogram, i.p.) at day 3 (end of latency). RESULTS: Both intramembranous and endochondral ossification was seen in the osteogenesis area. BrdU+ mesenchymal progenitor cells were significantly higher at day 10 (P <.05) and were found most numerously around the sagittal middle portion of the gap (P <.01). The greatest numbers of BrdU+ osteocytes were seen at day 38 (P <.05). Both BrdU+ osteoclasts and chondrocytes peaked at day 24. CONCLUSIONS: Mesenchymal progenitor cells are mostly recruited in the early consolidation period, but they decrease in the middle and late consolidation periods during mandibular distraction osteogenesis. The rapid rate might suppress or sustain the proliferation and differentiation of mesenchymal progenitor cells during mandibular distraction osteogenesis. BrdU+ cells can survive throughout the entire experimental period of 5 weeks.

Animals↗

PubMed2005

Porosity of 3D biomaterial scaffolds and osteogenesis.

Porosity and pore size of biomaterial scaffolds play a critical role in bone formation in vitro and in vivo. This review explores the state of knowledge regarding the relationship between porosity and pore size of biomaterials used for bone regeneration. The effect of these morphological features on osteogenesis in vitro and in vivo, as well as relationships to mechanical properties of the scaffolds, are addressed. In vitro, lower porosity stimulates osteogenesis by suppressing cell proliferation and forcing cell aggregation. In contrast, in vivo, higher porosity and pore size result in greater bone ingrowth, a conclusion that is supported by the absence of reports that show enhanced osteogenic outcomes for scaffolds with low void volumes. However, this trend results in diminished mechanical properties, thereby setting an upper functional limit for pore size and porosity. Thus, a balance must be reached depending on the repair, rate of remodeling and rate of degradation of the scaffold material. Based on early studies, the minimum requirement for pore size is considered to be approximately 100 microm due to cell size, migration requirements and transport. However, pore sizes >300 microm are recommended, due to enhanced new bone formation and the formation of capillaries. Because of vascularization, pore size has been shown to affect the progression of osteogenesis. Small pores favored hypoxic conditions and induced osteochondral formation before osteogenesis, while large pores, that are well-vascularized, lead to direct osteogenesis (without preceding cartilage formation). Gradients in pore sizes are recommended for future studies focused on the formation of multiple tissues and tissue interfaces. New fabrication techniques, such as solid-free form fabrication, can potentially be used to generate scaffolds with morphological and mechanical properties more selectively designed to meet the specificity of bone-repair needs.

Biocompatible Materials↗

PubMed2006

Experimental studies on the effect of osteotomy technique on the bone regeneration in distraction osteogenesis.

The objective of the experiment was to study the effect of osteotomy technique on the course of bone regeneration in distraction osteogenesis in sheep. Thirty five merino sheep were divided into 5 groups of 7 sheep each, depending on the osteotomy technique: subcutaneous corticotomy, open corticotomy, Cattaneo corticotomy, open osteotomy and osteoclasia. Formation of regenerate and its remodeling was assessed, based on roentgenograms and morphological examination (bone sections, histological evaluation, SEM, superficial X-ray analysis). Irrespective from the osteotomy technique applied, in all experimental groups, regenerates filling the distraction gap were obtained. Analysis of bone sections and histological slides indicated the most advanced osteogenesis processes in the osteoclasia group. SEM examination and X-ray microanalysis confirmed not only the presence of mature bone tissue structures in this group, but also showed a mineralization close to that of a healthy bone. Osteogenesis was the slowest in the group of subcutaneous corticotomy. The observed histological picture and analysis of elemental composition indicate a normal course of distraction osteogenesis in this group, but its consecutive phases proceed with a certain delay, compared to the remaining groups. With a good deal of caution, it can be assumed that the delay of osteogenesis in the group of subcutaneous corticotomy in the 14th post-operative week was ca. 3 weeks compared to the osteoclasia group. In all experimental groups, few cartilaginous nodules were observed in regenerates 5 weeks and, in few cases, 9 weeks old. Ossification in such places was indirect, cartilage-based. In the remaining regions direct, membrane-based ossification prevailed. Direct apposition bone lamellae on islands of fibrous bone tissue was observed in regenerates aged 9 and 14 weeks, especially in periosteal regions. The intensity and rate of formation of new bone tissue varied between the experimental groups, based on roentgenological analysis and histological evaluation. Complex morphological studies on the course of regeneration in sheep showed the most advanced remodeling and mineralization of bone tissue in animals subject to osteoclasia.

Animals↗

PubMed2004

Intermittent parathyroid hormone (1-34) enhances mechanical strength and density of new bone after distraction osteogenesis in rats.

Distraction osteogenesis is used both for leg lengthening and for bone transportation in the treatment of fractures and nonunions. The main problem with this method is that the time until full recovery may be up to a year, partly because of the time needed for the new formed bone to consolidate and become strong enough for weight bearing. We have studied whether intermittent parathyroid hormone (PTH(1-34)) could accelerate the consolidation of new formed bone after distraction osteogenesis in rats. Forty-seven, 3-months-old male Sprague-Dawley rats underwent lengthening of the right femur using an external fixator. After a middiaphyseal osteotomy and a 7-day latency period, the callus was distracted during 10 days, with a distraction rate of 0.25 mm twice a day. The consolidation time was either 20 days or 40 days after distraction was completed. A dose of 60 microg of human PTH(1-34)/kg body weight/injection or vehicle was given every second day beginning 30 days before the rats were killed. Both femura of each rat were subjected to mechanical testing and dual-energy X-ray absorptiometry. Blinded histological examination was done for the distracted femura. In the 20 days consolidation experiment, PTH(1-34) increased ultimate load (56%), stiffness (117%), total regenerate callus volume (58%), callus BMC (24%) and histologic bone density (35%) compared to untreated distraction osteogenesis specimens. In the 40 days consolidation experiment, PTH(1-34) increased ultimate load (54%), stiffness (55%), callus BMC (33%) and histologic bone density (23%) compared to untreated distraction osteogenesis specimens. Total regenerate callus volume was unchanged. The contralateral femur also became stronger, stiffer and denser under PTH(1-34) treatment, but to a lesser degree. PTH(1-34) might become useful to shorten the consolidation time after distraction osteogenesis in humans.

Animals↗

PubMed2005

Subdural hematoma as clinical presentation of osteogenesis imperfecta.

Osteogenesis imperfecta is an inherited collagenous disease. The mildest form may present with less severe findings, for example blue sclera, but can also lead to significant handicap such as deafness or multiple bone fractures. We describe an 11-month-old female in whom bilateral chronic subdural hematoma was the leading clinical presentation of osteogenesis imperfecta type I. She was hospitalized due to epileptic seizures caused by these bilateral subdural hematomas without preceding trauma. Osteogenesis imperfecta type I was diagnosed on the basis of clinical and radiologic findings. This case demonstrates that nontraumatic chronic subdural hematoma in patients with osteogenesis imperfecta type I may be caused by impaired bone calcification, vascular fragility, and permanent friction between multiple bone fragments of the skull. Osteogenesis imperfecta type I should be considered as an underlying disease in cases of nontraumatic subdural hematoma. A thorough clinical examination is recommended to exclude subtle characteristics of the disease.

Female↗

PubMed2001

Osteogenesis imperfecta: mode of delivery and neonatal outcome.

OBJECTIVE: To evaluate the pregnancy characteristics, methods of delivery, and neonatal outcomes of fetuses affected by osteogenesis imperfecta. METHODS: We reviewed medical records of 1016 individuals whose cells were sent to the University of Washington Collagen Diagnostic Laboratory between 1987 and 1994 for confirmation of diagnoses of osteogenesis imperfecta. Information and neonatal records were available for 167 of those pregnancies. From those we identified method(s) of prenatal detection, delivery method, and neonatal complications, including survival and acquisition of new fractures, and related them to type of delivery. RESULTS: The cesarean delivery rate was 54%, most of them (53%) for nonvertex presentation and fewer than 15% because of an antenatal diagnoses of osteogenesis imperfecta. There was an unusually high rate of breech presentation at term (37%). In infants with nonlethal forms of osteogenesis imperfecta, 24 of 59 (40%) delivered by cesarean and 17 of 53 (32%) delivered vaginally had new fractures (chi(2) =.89; P =.3). Among 55 infants with the most severe form, 24 of 31 delivered by cesarean and 21 of 24 delivered vaginally died within 2 weeks of birth. CONCLUSION: Cesarean delivery did not decrease fracture rates at birth in infants with nonlethal forms of osteogenesis imperfecta nor did it prolong survival for those with lethal forms. Prenatal diagnosis did not influence mode of delivery in most instances. Most cesarean deliveries were done for usual obstetric indications.

Breech Presentation↗

PubMed2000

Two-year follow-up of distraction osteogenesis: its effect on mandibular ramus height in hemifacial microsomia.

Distraction osteogenesis has been used to lengthen the mandible in patients with hemifacial microsomia. Questions regarding soft tissue and skeletal growth after distraction osteogenesis have not been clearly elucidated in the literature. In this case report, a 2-year follow-up of distraction osteogenesis in a 7 year old boy is documented with lateral and posterior/anterior cephalometric analysis. The analysis was performed preoperatively and at specific postsurgical periods to evaluate the facial soft tissue and skeletal growth patterns. Objective analysis of this growing patient after distraction osteogenesis clearly demonstrates that the anteroposterior elongation of the mandible is relatively stable, whereas the vertical lengthening and soft tissue effects are minimal. Critical evaluation of other patients who have undergone distraction osteogenesis is needed to determine if this was an isolated incident or the expected result in similar patients.

Abnormalities, Multiple↗

PubMed2003

Cost, operation and hospitalization times in distraction osteogenesis versus sagittal split osteotomy.

INTRODUCTION: Distraction osteogenesis in 'common' surgical orthodontics is mentioned as an alternative for conventional sagittal split osteotomy. After a 'learning curve' in the surgical skills of distraction, the two techniques can be compared concerning time and cost aspects. PATIENTS: Forty-seven patients (male n=28, female n=19, age 11.7-17.9 yr (mean 14.2) with an Angle's class II division 1malocclusion of skeletal mandibular origin were operated on using distraction osteogenesis and were compared with a second group of 21 patients (male n=4, female n=17, age 16-36yr (mean 22.8) who underwent bilateral sagittal split osteotomies in the same period in order to correct the same type of dysgnathia. METHOD: The first group of 47 patients was treated with intraorally placed bone-born distraction devices to correct mandibular deficiency following a standard protocol, with removal of the third molar tooth germs if present. The second group of 21 patients underwent standard sagittal split osteotomies to correct the mandibular deficiency. The costs of hospitalization, distraction devices and operation time were compared. RESULTS: In this study, distraction osteogenesis took on average more operative time (mean 37%), but 1 day less hospitalization than the bilateral sagittal split osteotomies. The surgical cost of distraction osteogenesis was 36% higher than the conventional sagittal split osteotomy. CONCLUSION: In this study, correcting Angle's class II deficiencies by means of distraction osteogenesis was shown not to be a time-saving procedure when compared with sagittal split osteotomy. Surgical costs were significantly higher using distraction, mainly due to the price of the distractors. Changes in hospital policies concerning hospital admission of adults and children and European legislation concerning re-usability of surgical instruments may balance the cost of both procedures.

Adolescent↗

PubMed1999

Evaluation of oral problems in an osteogenesis imperfecta population.

OBJECTIVE: The incidence of craniofacial and dental anomalies in children with the more severe nonlethal forms of osteogenesis imperfecta was evaluated. STUDY DESIGN: The study evaluated 40 children (age range, 1-17.5 years) with types III and IV osteogenesis imperfecta. In each case, the dentition was evaluated for the presence of dentinogenesis imperfecta, attrition, and caries, as well as for radiographic appearance, dental development, and malocclusion. RESULTS: The incidence of dentinogenesis imperfecta was greater than 80% in the primary dentition. Clinically, the color of the dentition was of predictive value in appropriate management of the primary dentition. Tooth discoloration and attrition did not occur to the same extent in the permanent dentition as in the primary dentition in either group. Class III dental malocclusion occurred in 70% to 80% of this osteogenesis imperfecta population, with a high incidence of anterior and posterior cross bites and open bites. A delay in dental development was observed in 21% of patients type III osteogenesis imperfecta, whereas accelerated development was noted in 23% of the patients with type IV. In addition, ectopic eruption occurred in 13 patients. CONCLUSIONS: In addition to dentinogenesis imperfecta, significant oral problems occur in types III and IV osteogenesis imperfecta. Other features that impact the dental management of this population are highlighted.

Adolescent↗

PubMed1981

The relative amounts of the collagen chains alpha 1(I), alpha 2 and alpha 1(III) in the skin of 31 patients with osteogenesis imperfecta.

1. The relative amounts of type III and type I collagen, determined as the ratio of their constituent alpha 1(III) and alpha 1(I) chains, have been measured by interrupted electrophoresis of pepsin extracts of skin collagen from 31 patients with osteogenesis imperfecta of varying severity, and from six clinically unaffected family members. In 18 patients the ratio of the alpha 1(I) to alpha 2 chains of type I collagen has also been measured. 2. In the 15 patients with osteogenesis imperfecta classified as mild or the 18 with type I disease the ratio alpha 1(III)/alpha 1(I) was significantly increased (P less than 0.001) and the ratio alpha 1(I)/alpha 2 significantly decreased (P less than 0.005) compared with age-matched control subjects. 3. In three infants with lethal (type II) osteogenesis imperfecta the ratio alpha 1(III)/alpha 1(I) was normal, contrasting with the high ratio observed by others in fibroblast cultures from some apparently similar patients. 4. The ratio of alpha 1(I)/alpha 2 and of alpha 1(III)/alpha 2(I) was increased in both clinically normal parents of a child with severe disease, and in the mother of two children with osteogenesis imperfecta (one lethal and one severe) the ratio alpha 1(III)/alpha 1(I) was increased. 5. In the remaining patients with severe bone deformity (types III and IV) the relative amounts of the different collagen chains varied. 6. These data support previous suggestions that mild or type I osteogenesis imperfecta results from a generalized inability to form sufficient type I collagen, the predominant collagen of adult bone, and imply that in many cases this may result from defective production of the alpha 1(I) chain rather than of the alpha 2 chain. Some patients with severe disease demonstrate a similar defect; but in the remainder other abnormalities of collagen or connective tissue maturation are presumably involved.

Adolescent↗

PubMed2001

Cranial distraction osteogenesis in sheep using a totally implantable hydraulic mechanism: early results.

Conventional distraction osteogenesis has been performed by using either percutaneous pins attached to a thread and screw mechanism, or a thread and screw mechanism that is implanted but still requires turning by a percutaneous instrument or device. In these situations there is always the risk of infection passing to the bone via the percutaneous connection. We have developed a totally implantable hydraulic mechanism, which is activated in much the same way as injection into the port of a tissue expander. Preliminary in vitro testing has suggested that our mechanism can produce sufficient force at appropriate rates of distraction to have a promising role in distraction osteogenesis. We examined the effect of osseous distraction on the cranial vault. Expansion of the cranial vault by distraction osteogenesis is not widespread in clinical practice, in part because of the risk of infective complications of the extra-dural space. We were, therefore, presented with an ideal opportunity both to test the new distraction device and to examine the effect of distraction osteogenesis on the cranial vault. A sheep animal model was used in a pilot study to test the plausibility and examine the physiology of cranial-vault distraction osteogenesis using a totally implantable hydraulic device. Two sheep had a device implanted in the temporal fossa so as to push the craniotomised cranial cap upwards. Distraction was performed for 13 days beginning 1 week after craniotomy. After 9 weeks of consolidation, 5.5 mm and 7.4 mm of new woven bone of normal cranial thickness were demonstrated.

Animals↗

PubMed2003

Collagen content and growth factor immunoexpression in uterine lower segment of type IA osteogenesis imperfecta: Relationship with recurrent uterine rupture in pregnancy.

OBJECTIVE: The purpose of this study was to evaluate collagen content and platelet-derived growth factor, vascular endothelial growth factor, and connective tissue growth factor expression in the myometrium of the uterine lower segment from a patient with type IA osteogenesis imperfecta with recurrent uterine rupture and to evaluate the existence of a relationship between the rare recurrent uterine rupture and the tissue disorders of type IA osteogenesis imperfecta. STUDY DESIGN: Collagen content and platelet-derived growth factor, vascular endothelial growth factor, and connective tissue growth factor expression in the uterine lower segment were assessed in the patient with type IA osteogenesis imperfecta and in eight otherwise healthy ("control") patients. RESULTS: Type IA osteogenesis imperfecta contained less total collagen amount, with no difference in type III collagen expression and showed increased levels of platelet-derived growth factor and vascular endothelial growth factor in myometrial smooth muscle cells. No difference was observed in connective tissue growth factor expression. CONCLUSION: These findings confirm the diminished collagen amount in myometrium from osteogenesis imperfecta and show the presence of additional pathogenetic mechanisms. A relationship is hypothesized between the underlying myometrial biochemical modifications and the recurrent uterine rupture.

Adult↗

PubMed1997

A CT scan technique for quantitative volumetric assessment of the mandible after distraction osteogenesis.

Distraction osteogenesis has become an accepted method of treatment for patients requiring reconstruction of hypoplastic mandibles. We present a quantitative analysis of volumetric changes after distraction osteogenesis in a series of 10 patients. Group I (n = 5 patients, 3 unilateral craniofacial microsomia, 1 Goldenhaar syndrome, and 1 bilateral craniofacial microsomia) underwent unilateral distraction of the mandible. Group II (n = 5 patients, 1 Nager syndrome, 1 bilateral craniofacial microsomia, 1 developmental micrognathia, and 2 Treacher Collins syndrome) underwent bilateral distraction of the mandible. Predistraction and postdistraction axial and three-dimensional computed tomographic (CT) scans were digitized and transferred to a computer for analysis with image-processing software to determine the changes in volume of the mandible and bony regenerate. The CT-derived volume method was validated by scanning three dry cadaver mandible specimens and comparing the volume data with those derived from a water-displacement method. The difference between the two methods was less than 5 percent. The mean distracted length, as recorded from the calibrated device, was 22.6 mm in the 10 patients. In the unilateral distraction group, the mean increase in hemimandibular bone volume was 2.8 cc, with a mean percentage increase of 27 percent in the distracted hemimandible. In the bilaterally distracted patients, the mean increase in total mandibular volume was 7.9 cc, with a mean percentage increase in bone volume of 25 percent. This study represents the first attempt to quantify the increase in bone volume resulting from distraction osteogenesis. Quantitative volumetric analysis of CT scans is an accurate method to measure the amount of bone regenerate in patients undergoing distraction osteogenesis of the mandible or the extremities. The concept and utility of quantifying the volumetric changes in bone following distraction osteogenesis may become more important as multiplanar devices are developed and used in other areas of the craniofacial skeleton.

Adolescent↗

PubMed1999

Rat mandibular distraction osteogenesis: II. Molecular analysis of transforming growth factor beta-1 and osteocalcin gene expression.

Distraction osteogenesis is a powerful technique capable of generating viable osseous tissue by the gradual separation of osteotomized bone edges. Although the histologic and ultrastructural changes associated with this process have been extensively delineated, the molecular events governing these changes remain essentially unknown. We have devised a rat model of mandibular distraction osteogenesis that facilitates molecular analysis of this process. Such information has significant clinical implications because it may enable targeted therapeutic manipulations designed to accelerate osseous regeneration. In this study, we have evaluated the expression of transforming growth factor beta-1, a major regulator of osteogenesis during endochondral bone formation and development, and osteocalcin, an abundant noncollagenous extracellular matrix protein implicated in the regulation of mineralization and bone turnover. The right hemimandible of 36 adult male rats was osteotomized, and a customized distraction device was applied. Animals were allowed to recover and, after a 3-day latency period, were distracted at a rate of 0.25 mm twice daily for 6 days followed by a 2- or 4-week consolidation period. Distraction regenerate was harvested after the latency period, days 2, 4, or 6 of distraction, and after 2 or 4 weeks of consolidation and processed for Northern analysis (n = 4 at each time point) and immunohistochemical localization of TGF-beta1 (n = 2 at each time point). Six sham-operated animals (i.e., skin incision without osteotomy) were also killed (immediately postoperatively), and the mandibles were harvested and prepared in a similar fashion. Equal loading and transfer of RNA for Northern analysis was ensured by stripping and probing membranes with a probe against GAPDH (a housekeeping gene). Our results demonstrate that the spatial and temporal patterns of TGF-beta1 mRNA expression and protein production coincide with osteoblast migration, differentiation, and extracellular matrix synthesis. In addition, we demonstrate that TGF-beta1 production may be an important regulator of vasculogenesis during mandibular distraction osteogenesis. Finally, we have shown that osteocalcin gene expression coincides temporally with mineralization during rat mandibular distraction osteogenesis.

Animals↗

PubMed2002

Distraction osteogenesis of costochondral bone grafts in the mandible.

Costochondral grafting for reconstruction of the Pruzansky type III mandible has given variable results. Lengthening of the rib graft by means of distraction had been advocated when subsequent growth of the grafted mandible is inadequate. This retrospective study reviews a series of patients with mandibular costochondral grafts who underwent subsequent distraction osteogenesis of the graft. A retrospective review identified two patient groups: group 1 consisted of individuals (n = 9) who underwent costochondral rib grafting of the mandible followed by distraction osteogenesis several months later at a rate of 1 mm/day. Group 2 consisted of patients with Pruzansky type II mandibles who had distraction osteogenesis without prior rib grafting (n = 9). The biomechanical parameters, orthodontic treatment regimens, and complications were examined versus patient age and quality of the rib graft. Distraction osteogenesis was successfully performed in six of the rib graft patients (group 1) and in all of the group 2 individuals. On the basis of the Haminishi scale, the computed tomographic scan appearance of the regenerate was classified as "standard or external" in six of the group 1 patients and as either "agenetic" or "pillar" (fibrous union) in the remaining three patients. In group 1, the average device was expanded 23 mm (range, 20 to 30 mm). Group 2 mandibular distraction results were all classified as either standard or external, and there was an average device expansion of 22.4 mm (range, 16 to 30 mm). The length of consolidation averaged 12.6 weeks in group 1, compared with 8.5 weeks in the traditional mandibular distraction patients (group 2). The mean shift of the dental midline to the contralateral side was 2.5 mm in group 1 versus 4.0 mm in group 2. Complex multiplanar and transport distractions were successfully performed on grafts of adequate bony volume. All four patients in group 1 with tracheostomies were successfully decannulated after consolidation. Rib graft distraction complications included pin tract infections in two patients, hardware failure with premature pin pullout in one patient, and evidence of fibrous nonunions in three young patients with single, diminutive rib grafts. In group 2, there were no distraction failures. Distraction osteogenesis can be successfully performed on costochondral rib grafts of the mandible; however, the complication rate is higher than in non-rib-graft patients. Performing the technique on older, more cooperative individuals seems to reduce this risk. In addition, placement of a double rib graft or an iliac bone graft of sufficient volume to create a neomandible with greater bone stock is an absolute requirement to decrease the risk of fibrous nonunion and provide a bone base of sufficient size for retention of the distraction device and manipulation of the regenerate.

Bone Transplantation↗

PubMed2002

Effect of distraction osteogenesis of the mandible on upper airway volume and resistance in children with micrognathia.

Children with craniofacial anomalies often have compromise of the upper airway, a condition with potential for morbidity and mortality. In children with microretrognathia, the diminutive size and retruded position of the mandible reduces the size of the oropharynx, thereby predisposing to glossoptosis and airway obstruction. Although several authors have reported successful use of mandibular distraction osteogenesis to alleviate this type of upper airway obstruction, the physiologic relationship between changes in mandibular shape, size, and position and upper airway dynamics remains undefined. The purpose of this study was to develop methodologies to quantitatively evaluate upper airway dynamics in children with micrognathia both before and after mandibular distraction osteogenesis. The patient population consisted of four children with micrognathia who had successfully undergone upper airway stabilization by bilateral mandibular distraction osteogenesis. The data used were digitally archived computed tomographic scan data from high-resolution, thin-slice head computed tomographic scans obtained before and after mandibular distraction. Upper airway evaluation was performed in two ways: static and dynamic. Static analysis consisted of computer quantification of predistraction and postdistraction mandibular and upper airway volumes using Analyze imaging software. Dynamic analysis consisted of fabrication of rigid stereolithographic hollow cast models of the upper airway produced from computed tomographic scan data. Models were used for characterization of upper airway resistance and flow patterns as related to respiration. After distraction osteogenesis, mandibular total volume increased 32, 32, 18, and 25 percent (mean, 27 percent) and upper airway volume increased by 20, 31, 23, and 71 percent (mean, 37 percent). A significant decrease in flow resistance, both inspiratory and expiratory, was observed in the patient with the greatest upper airway volume increase (71 percent) after distraction. After distraction, the inspiratory resistance was diminished by 51 percent and the expiratory resistance diminished by 85 percent. However, the three patients with more modest upper airway volume increases of 20 to 31 percent demonstrated no statistically significant change in flow resistance after distraction. Results of this study support the conclusion that distraction osteogenesis of the micrognathic mandible increases the volume of the upper airway, roughly paralleling the increase in mandibular volume. In the biomechanical airway model studied, upper airway volume expansion has been shown to be able to decrease the flow resistance over the length of the airway, presumably secondary to an increase in the average cross-sectional area. The artificial rigidity of the stereolithographic "airway" compared with the elasticity of the human upper airway may account for the insensitivity of this model to smaller but clinically significant airway changes.

Airway Resistance↗