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.     

Cloning, characterization, and chromosomal localization of human superillin (SVIL)

The specific aim of this study was to determine the response of alveolar bone after it was augmented vertically using distraction osteogenesis and subsequently loaded with implant restorations. Four dogs each had four implants placed horizontally into an edentulous mandibular quadrant and, after integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the device was stabilized with light cured resin. Following bone fill confirmation of the distraction gap at 10 weeks, two implants were placed into the ridges, one in distracted bone and one in nondistracted bone. After 4 months for implant integration, freestanding prostheses were fabricated. Crestal bone levels were evaluated throughout the period of function. Animals were sacrificed after 1 year of loading, for histologic evaluation of the bone. The vertical ridge augmentation averaged 8.85 +/- 1.05 mm after 10 weeks of healing following distraction, without change over 1 year of implant loading. Histologic examination showed that bone had formed between the distracted segments, creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone and the lingual and labial nondistracted cortical bone. The presence of the dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis maintained bone and were functional for the length of this study.     

Content and predictors of the ethnic identity of Russian-speaking immigrant adolescents in Finland

Even though osteodistraction has been well established in the extremities, the parameters used in craniofacial distraction have been essentially borrowed from orthopaedic experience. Latency is widely practised but its relevance has not been fully investigated. The purpose of this study was to establish the role of latency in mandibular distraction osteogenesis. Twenty-two growing Wethers sheep were allocated to four experimental groups. Six animals were allocated to each of Groups A, B and C and underwent bilateral mandibular corticotomies and attachment of an external lengthening device. Latent periods of 0, 4 and 7 days respectively were observed prior to beginning distraction. The distraction protocol consisted of a rate of 0.5 mm twice daily for 20 days, followed by a consolidation phase of 20 days after which the sheep were killed. Histology, bone densitometry and 3-point mechanical testing were performed on the harvested mandibles. Group D formed the control group (n = 4). Histologically, the distracted bone exhibited bone formation primarily via intramembranous ossification with scattered islands of cartilage. The regenerated bone had mechanical properties significantly weaker than the undistracted control group (P < 0.05), but between the experimental groups no statistically significant differences were demonstrable either in mechanical strength or DEXA density. These data indicate that a change in latency does not alter the properties of the regenerated bone in mandibular distraction osteogenesis and indeed no latent interval may be necessary at all in craniofacial distraction. This has implications for the duration of device fixation in distraction procedures.     

Internal calvarial bone distraction in rabbits with delayed-onset coronal suture synostosis

Recent studies have identified a subpopulation of craniosynostotic individuals who exhibit progressive or delayed-onset synostosis and mild craniofacial growth abnormalities. These individuals may be good candidates for nonextirpation, distraction osteogenesis therapy. The present study was designed to test this hypothesis by using internal calvarial bone distraction in a rabbit model with familial delayed-onset craniosynostosis. Data were collected from 159 rabbits: 71 normal controls, 72 with delayed-onset coronal suture synostosis, 8 with delayed-onset coronal suture synostosis and coronal suturectomy, and 8 with delayed-onset coronal suture synostosis and distraction. At 10 days of age, all rabbits had amalgam markers placed on both sides of the frontonasal, coronal, and anterior lambdoidal sutures. At 25 days of age, correction was accomplished through either a 5-mm-wide suturectomy or distraction osteogenesis. An internal distraction appliance was fixed to the frontal and parietal bones and percutaneously and intermittently activated at an average of 0.10 mm/day for 42 days (4.11 mm total). Serial radiographs were taken at 10, 25, 42, and 84 days of age. Results revealed that rabbits with delayed-onset synostosis had significantly (p < 0.01) reduced coronal suture growth rates (0.04 mm/day) compared with the other three groups (0.07 mm/day). Rabbits with suturectomy and rabbits with distraction showed similar coronal suture responses. However, from 42 to 84 days of age, rabbits with distraction showed reduced growth at the vault sutures and abnormal growth patterns in cranial vault width, cranial vault shape, and cranial base angulation compared with the other three groups. Results demonstrated that, although the normal coronal suture growth rate was maintained in rabbits with delayed-onset synostosis using intermittent distraction osteogenesis, normal adult craniofacial structure was not achieved. Such anomalous growth was probably a result of altered growth vectors and compressive forces at adjacent sutures during distraction. These findings suggest that distraction osteogenesis without corticotomy may be a treatment alternative in individuals with progressive, delayed-onset synostosis, but that internal appliances that generate low-level, continuous distractive forces should be investigated and developed.     

Distraction osteogenesis for lengthening of the hard palate: Part I. A possible new treatment concept for velopharyngeal incompetence. Experimental study in dogs

Many procedures have been described to correct velopharyngeal incompetence. Significant complications can occur, and the results may not be satisfactory. If the short soft palate has satisfactory muscle function and if it could be moved toward the posterior pharyngeal wall by distraction osteogenesis of the hard palate, an entirely new concept of treatment for velopharyngeal incompetence would be available. The object of the present study was to explore the possibility of osteogenesis occurring in the hard palate in dogs after gradual distraction (callus distraction). Six adult, mix-bred dogs were anesthetized, and the palatal mucosa was elevated. A midpalatal transverse osteotomy and two lateral osteotomies were performed. Tantalum bone markers for cephalometric analysis were placed, and an individually fabricated, orthodontic-like distraction device with an expansion screw in the sagittal direction was inserted. The device was stabilized on the premolars and fixed to the palatal bone with titanium miniscrews. Gradual distraction began after a latency period of 10 to 18 days. The rate of the distraction varied from 0.25 to 0.75 mm per day. The device was left in place for 6 to 8 weeks after expansion to allow for bony consolidation. Assessment was by direct examination, cephalograms, computed tomography, and histology with bone labeling. Impressions of the jaws were taken preoperatively and after device removal to examine plaster cast changes in the dental occlusion. Cephalometric and computed tomographic scan analysis demonstrated a distraction of up to 8 mm. All gaps were filled with de novo osteogenesis. Comparison of the plaster casts revealed no change in the occlusion. At 1 month after distraction, the computed tomographic scan showed the first signs of ossification of the experimental gap from the anterior and posterior bone ends. After 4.5 months ossification was almost complete with a small translucent zone in the middle of the experimental gap. After 7 months ossification was complete.     

Effect of methotrexate on distraction osteogenesis

To assess the potential of using distraction osteogenesis to reconstruct bone deficient limbs after limb salvage for musculoskeletal sarcomas, the authors examined the effect of methotrexate on distraction osteogenesis in a rabbit tibial lengthening model. Eighteen rabbits underwent tibial corticotomy and application of a ring external fixator. Rabbits were assigned randomly to one of two groups in which either methotrexate (n = 12) or placebo (n = 6) was administered during a 21-day distraction period. Serum methotrexate levels and complete blood cell counts were monitored during distraction, and radiographs of the tibia were obtained weekly. Half of the animals from each group were sacrificed at the end of distraction, and the remaining animals were sacrificed after 6 weeks of neutral fixation when bone normally bridges the gap. Using methotrexate at serum concentrations similar to those used clinically for the treatment of human osteosarcomas, the authors were unable to show significant radiographic, histologic, or chemical differences in the effect of this antineoplastic drug on distraction osteogenesis in the rabbit model.     

Basement membrane of blood vessels during distraction osteogenesis

A canine model of distraction osteogenesis has recently been developed that permitted the evaluation of bone formation and its vascularization during bifocal callotasis. In this model, the authors examined the composition of the blood vessels during distraction osteogenesis of the mandible for laminin and for Type IV collagen, both constituents of the vascular basement membrane. At the fibrous distraction site, at the juncture of the free cortical surface and the regenerated bone, and at the abutting cortical surfaces at the distal margin of the defect, laminin and Type IV collagen were present in all vessels.     

Recombinant growth hormone accelerates bone regenerate consolidation in distraction osteogenesis

The purpose of the present study was to prove whether homologous GH has a stimulating effect on bone healing. Therefore, left tibiae of 30 micropigs were osteomized and distracted over an external fixator at the rate of 2 mm/day on each of 10 consecutive days. Animals were killed after a healing period of another 10 days. The treatment group received 100 microg of recombinant porcine growth hormone (rpGH) per kilogram of body weight per day. Serial torsional nondestructive biomechanical tests were performed in vivo using a newly developed measurement device. After killing, destructive torsional strength testing of the sites of distraction was performed. To determine the endocrine response to the administration of rpGH, serum levels of insulin-like growth factor-I (IGF-I) were determined. Nondestructive in vivo testing showed that torsional stiffness of the regenerate was significantly higher in the treatment group than in the control group. Final regenerate torsional failure load was 131% higher and ultimate torsional stiffness was 231% higher in the treatment group than in the control group. The mean serum level of IGF-I increased to 440% of preoperative basal level in the treatment group and remained unchanged in the control group. Our data indicate that systemic administration of recombinant homologous growth hormone greatly accelerates ossification of bone regenerate in distraction osteogenesis.     

"Primary" orthostatic tremor. 10 clinical electrophysiologic observations

Distraction osteogenesis has been shown to be an effective method of lengthening and augmenting endochondral bone. It has also been applied effectively in the reconstruction of the membranous bones of the craniofacial skeleton. With the accumulation of clinical experience in mandibular distraction, the differences between endochondral and membranous bone distraction have become apparent, especially in the limitations of uniplanar distraction for the three-dimensional reconstruction of the deficient mandible. Distraction of the mandible in a single plane cannot satisfy fully the functional and structural requirements of the patient with malocclusion as well as deficiency of the skeletal and soft tissue. This study reports the development and clinical use of a multiplanar mandibular distraction device with the ability to achieve linear distraction (Z-plane or sagittal), angular distraction (Y-plane or vertical), and transverse distraction (X-plane or coronal). The device contains two independent gear arrangements attached to two arms that extend from the central unit. Therefore, the trajectory of the regenerated bone may be changed during the distraction process. The device also allows manipulation of the various planes of movement independent of each other. Furthermore, the rotational points for the multiplanar distraction devices are located at a single point; therefore only a single osteotomy and two pin sites are required. The multiplanar distraction device allows the surgeon to customize and contour the dimensions of the distraction process by controlling the trajectory of the translation of the regenerated bone.     

AP-1 and NF-kappaB regulation in rheumatoid arthritis and murine collagen-induced arthritis

Mandibular distraction was performed on 14 children, between September 1991 and December 1997. Their average age was 6.9 years, ranging from 1.5 to 13.5 years. All patients had severe hypoplastic mandibles with retromandibulism. Seven of the children (50%) had respiratory distress due to obstruction of the upper airway before distraction. This resolved in every case. Five patients underwent unilateral and nine bilateral distraction. A total of 23 distractors were used, 15 were applied extraorally and 8 endorally. The average latency time after operation was 2.8 days, but for the past 2 years, distraction was started beginning with the operation. The distraction was increased twice daily for an average of 5.5 weeks, by 0.4 or 0.5 mm each time, depending on the distractor. Computed tomography and ultrasound were used to follow the ossification process in the distraction gap and to measure the lengthening achieved. Subsequent retention time averaged 2.4 weeks. The mandibles were elongated by up to 18 mm (average 9.3 mm) and the respiratory distress symptoms resolved in all patients. Several minor complications which are reported occurred. Six patients were followed up for periods between 3 and 7 years. During this time further growth of the distracted mandibles was recorded.     

Distraction osteogenesis for lengthening of the hard palate: Part II. Histological study of the hard and soft palate after distraction

To correct velopharyngeal incompetence, a new treatment concept was proposed in Distraction Osteogenesis for Lengthening of the Hard Palate: Part I (using lengthening of the hard and soft palate by distraction osteogenesis). Cephalometry and computed tomography showed successful elongation of the posterior hard palate with gradual calcification. Here the sequential use of fluorochrome markers (oxytetracycline, xylenol orange, DCAF [2,4-bis-N-N'-dicarboxymethyl aminomethyl fluorescein], and alizarin complexone) during the distraction and retention period is reported together with the histologic investigations using light and laser scan microscopy without prior demineralization. The experimental gap showed de novo osteogenesis in all dogs. The new bone was always in continuity with the original anterior and posterior palatal bone margins. It either bridged the experimental gap fully or left a small central zone of fibrous tissue, in which eventual ossification occurred. Several distinct zones could be distinguished: A small central zone was found with parallel strains of collagen fibers, oriented longitudinally in the direction of the distraction. Next to this zone a layer of undifferentiated mesenchymal precursor cells was seen in direct contact to newly formed bone. The next zone was coarse woven bone, showing a transition to mature lamellar bone through remodeling. No evidence of endochondral bone formation was found, i.e., all dogs showed exclusively intramembranous bone formation. The soft tissues showed no signs of alteration: in particular, there was no necrosis or scar formation. The soft tissues were not thinned but appeared to have followed the longitudinal displacement. In conclusion, gradual distraction osteogenesis of the hard palate could be a possible method for lengthening the palate to treat velopharyngeal incompetence.     

CAD/CAM (computer-aided design/computer-aided manufacturing) titanium implants for cranial and craniofacial defect reconstruction

The reconstruction of craniofacial bone defects with intraoperatively modeled prosthesis restricts the choice of material and its biocompatibility and the prediction of the esthetic result. A prolonged duration of the surgical procedure and an increased stress on the patient are consequences. In contrast, modern industrial CAD/CAM-systems allow the prefabrication of titanium prosthesis: An individual computer-based 3D model of the bony defect is generated after acquisition, transfer and evaluation of helical CT data. Basing on these data the individual prosthesis-shape is designed using freeform surfaces geometries and fabricated by a numerically controlled milling machine. The conical margins of this prosthesis-geometry are generated by the borders of the defect with a minimal gap of 0.25 mm, and the surface contours by considering the non-affected neighbouring contours with a constant thickness of 1.5 mm. Individual osteosynthesis-microplates for fixation are integrated in design and manufacturing if screw-holes cannot be integrated in the thin margins of the implants. The radiological and clinical results of 17 patients after reconstruction of craniofacial bone defects with CAD/CAM titanium implants were good. Complications were not observed.     

Distraction osteogenesis and its application to the midface and bony orbit in craniosynostosis syndromes

The purpose of this study was to demonstrate the potential advantages of applying distraction osteogenesis techniques to the correction of orbital and midfacial hypoplasia in craniosynostosis syndromes. Fifteen children with various craniosynostosis syndromes underwent Le Fort III advancement assisted by gradual distraction utilizing a pair of internal distraction devices custom-fabricated for each child. The surgical procedure consisted of a Le Fort III osteotomy, implantation of internal devices with initiation of distraction intraoperatively, and an accelerated rate of midfacial advancement over the next 3 to 5 days. Activation of the distraction hardware was accomplished by a percutaneous pin, which was removed at the end of the distraction protocol, allowing the internal devices to fixate the fragment for a minimum of 6 months during the period of consolidation. With follow-up ranging between 3 to 38 months, the average orbital and midfacial advancement was 19.7 mm (range, 12.0-30.0 mm). Proptosis was lessened and facial proportions significantly improved in all patients. Serious complications were not encountered. The modified distraction protocol utilized in this group of patients was aimed at addressing the unique requirements of pediatric craniofacial surgery, and resulted in almost twice the amount of correction previously reported for traditional rigid fixation techniques.     

UDP-GlcNAc:Galbeta1-->3GalNAc (GlcNAc to GalNAc) beta1-->6N-acetylglucosaminyltransferase holds a key role on the control of CD15s expression in human pre-B lymphoid cell lines

Distraction osteogenesis has become an important technique to treat craniofacial skeletal dysplasia. In this study, the technique of maxillary distraction with a rigid external distraction device is presented. Cephalometric results in the first 14 consecutive patients are analyzed. The study sample consisted of 14 patients with various cleft types and maxillary hypoplasia treated with the rigid external distraction technique. Analysis of the predistraction and postdistraction cephalometric radiographs revealed significant skeletal maxillary advancement. All patients had correction of the maxillary hypoplasia with positive skeletal convexity and dental overjet after maxillary distraction. The morbidity for the procedure was minimal. Surgical and orthodontic procedures are thoroughly described.     

Evaluation of the mechanical environment during distraction osteogenesis

Physical forces have been hypothesized to direct the process of bone regeneration during distraction osteogenesis. However, despite significant clinical experience, relatively little is known about how the mechanics of distraction influence bone formation. This study investigated net fixator forces and strains in the distraction callus during bilateral lengthening of tibiae in New Zealand White rabbits. Distractions yielded a classic viscoelastic response with a sharp increase in fixator force, followed immediately by significant relaxation. Tension acting on mesenchymal gap tissue caused by distraction was estimated to reach more than 30 N by the time full lengthening was achieved. Average maximum cyclic strains within the distraction zone during ambulation were estimated to be 14% to 15% and supported by the results of fluoroscopic imaging. Paradigms for fracture healing have hypothesized that such strains are incompatible with new bone formation. The documented clinical success of distraction osteogenesis at stimulating large volumes of new bone suggests that other mechanisms that warrant additional investigation may be at work during distraction.     

Monobloc craniomaxillofacial distraction osteogenesis in a newborn with severe craniofacial synostosis: a preliminary report

Severe craniofacial synostosis can be a devastating problem for a newborn infant. Reasons for early surgical intervention include cranial stenosis, hydrocephalus, inadequate globe and corneal protection, compromised airway patency, and feeding problems. In this preliminary report, we describe the management of severe craniofacial synostosis in a newborn infant by means of cranial and midfacial distraction osteogenesis.     

Maxillary distraction osteogenesis in Pfeiffer's syndrome: urgent ocular protection by gradual midfacial skeletal advancement

Distraction osteogenesis is increasingly recognised as a potentially useful technique to achieve the co-ordinated augmentation of craniofacial skeletal and soft tissue. A case is presented where bilateral maxillary distraction was successfully used to advance the midface in the treatment of recurrent ocular dislocation, in a 10-month-old boy with Pfeiffer's syndrome.     

Distraction effects on muscle. Leg lengthening studied in rabbits

We investigated changes in the anterior tibial muscle during lengthening of the lower leg in rabbits. In 37 rabbits, an osteotomy of the right middle tibia was performed and was fixed by a unilateral external fixator. The rabbits were randomized into 6 groups. In groups 1, 2, and 3 the tibiae were distracted 0.5 mm/day. In groups 1 and 2, the rabbits were killed after 14 and 28 days of distraction, respectively, and in group 3 after 28 days of distraction, followed by 14 days of rest. Groups 1a, 2a, and 3a served as controls. They were treated similarly as groups 1, 2, and 3, but no distraction was performed. Proliferating cell nuclei were labeled with 5-bromo-2-deoxyuridine and were identified by immunohistochemical staining. The weight of the muscle was measured. During bone lengthening the muscle showed signs of growth, as indicated by increasing weight and number of proliferating cell nuclei. This was observed only during lengthening and it ceased when the lengthening was stopped.     

Induced osteogenesis for repair and construction in the craniofacial region

Solid and powdered forms of undemineralized and demineralized bone grafts were implanted in rat cranial defects. Demineralized calvarial discs healed the defects as well as did the fresh discs, as judged by histology and 45Ca incorporation. Gross and histologic evaluations demonstrated predictable endochondrial osteogenesis by demineralized bone powder (DBP). Undemineralized grafts, in contrast, showed poor and unpredictable bony healing. Construction of facial bones was achieved by implantation of demineralized bone powder within the soft tissues. The phenomenon of induced osteogenesis by demineralized implants was not species specific. These studies of osseous transformation provide insight into the mechanism of, and possible answers to, the problems of osseous transplantation.