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PubMed1999

Reduced gap strains induce changes in bone regeneration during distraction.

A bilateral New Zealand white rabbit model of distraction osteogenesis (DO) was used to investigate the relationship between strain environment and bone regeneration during limb lengthening. In seven (n = 7) rabbits, a stiffener was applied to the fixator on one side to reduce strains within the gap tissue after lengthening was completed. Animals were euthanized six days later and their distraction zones were harvested and analyzed for changes in new bone volume and architecture. Nonlinear finite element analyses (FEA) were performed to predict changes in the gap strain environment. FEA results predicted a nearly uniform sevenfold decrease in average strain measures within the distraction zone. No change in total average new bone volume and significant decreases in both bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) were observed in tibiae in which gap strains were reduced experimentally, compared to contralateral controls. These results suggest that fixator stiffening influenced the architecture but not the amount of newly formed bone. This animal model of distraction might be used to study the mechanisms by which strain fields affect events in bone repair and regeneration, such as cell proliferation, precursor tissue differentiation, and altered growth factor and nutrient delivery to tissues.

Animals↗
PubMed2005

Stereolithographic models for simulation and transfer of vector in vertical distraction of the mandibular ramus: a technical note.

Mandibular distraction osteogenesis is, despite impressive results, compromised as a treatment modality by difficulties with vector control independent of whether intra- or extraoral devices are used. Resistance of the masticatory muscles and the remaining soft tissue envelope toward elongation and incorrect planning and transfer of the vector cause lack of vector control. To ensure predictability in correct placement of intraoral distraction devices and thereby treatment outcome, a combined planning, simulation, and transfer method was developed. The purpose of the simulation and transfer technique is to duplicate the planned and simulated position and orientation of the distraction device during surgery. The preoperative plan is based on frontal and lateral head films, and the planned position and orientation of the distraction apparatus was applied on the stereolithographic model. The model was cut according to the planned osteotomy, and the distraction was simulated on the stereolithographic model. Based on plaster models transferred to the stereolithographic model, an individual guiding splint was fabricated to reproduce the planned and simulated distraction treatment in the patient. The details of the simulation and transfer technique are presented and discussed in two cases.

Adolescent↗
PubMed2001

[A new surgical method: lengthening of jaw bone by means of distraction technique].

Callus distraction, or distraction osteogenesis as the method also is called, is a new surgical technique which makes it possible to create new bone by bone elongation. The method was originally used in orthopedic surgery to extend long bones but has subsequently proved useful for extending the mandible as well as other bones in the facial skeleton. By callus distraction, it is now possible to treat severe jaw anomalies and also to treat bone defects in the jaws without bone transplantation. This article describes the biological background to the method and the basic principles that must be observed for successful results. The treatment of four patients illustrates the method.

Adolescent↗
PubMed2003

A device for determining the position of intraoral distractors for protracting the maxilla.

Distraction osteogenesis of the maxilla is indicated for jaw deformities in patients with extreme dysgnathia. First, extraoral appliances were introduced, and currently intraoral appliances are in vogue. These have significantly reduced the amount of physical and psychological stress placed on the patients. The direction of force vector may be varied according to the individual patient's requirements. This paper presents positioning devices for bilateral intraoral maxillary distraction plates, which have been developed to place maxillary distraction plates parallel to the direction of lengthening.

Adolescent↗
PubMed2006

Favorable morphologic change of preosteoblasts in a three-dimensional matrix with in vitro microdistraction.

BACKGROUND: Distraction osteogenesis has been used to correct hypoplastic and asymmetric bony deformities in the growing patient, yet its underlying cellular mechanisms are poorly understood. Using a new in vitro model, the microdistractor, morphologic properties of preosteoblasts under mechanical strain were studied. METHODS: Mouse calvarial MC3T3 cells were suspended in a polymerized three-dimensional collagen gel and stressed for 14 days as one of three groups (n = 30): (1) distraction (0.5 mm/day); (2) oscillation (1 mm/day for 2 days alternated with 1 mm/day for 2 days); and (3) control (no force). A computer modeling system, KS-300, was used to record cell shape (aspect ratio) and orientation (deviance from axis of stress). RESULTS: In part I of the study, morphologic cellular changes were found to be even throughout different regions of the gel (central versus peripheral, versus different vertical layers), suggesting the force was evenly applied to all cells in the gel. In addition, when linear distraction forces were applied, morphologic change occurred over time, suggesting a morphologic response to the applied stress. In part II of the study, with different forces applied, morphologic changes occurred over time such that linear distraction forces caused cells to elongate and align in a parallel direction to the force, whereas oscillation caused cells to switch from parallel (with distraction) to perpendicular (with compression) orientation relative to the force applied. CONCLUSION: The authors' data suggest that the microdistractor device is an effective in vitro model for studying the cellular response to distraction stresses. It may be used in future studies to optimize clinical methods of distraction.

3T3 Cells↗
PubMed2006

The efficacy of the bone markers osteocalcin and the carboxyterminal cross-linked telopeptide of type-I collagen in evaluating osteogenesis in a canine crural lengthening model.

The aim of the present study was to determine the efficacy of the bone markers osteocalcin (OC) and carboxyterminal cross-linked telopeptide of type-I collagen (ICTP) in evaluating new bone formation in the dog, using commercially available immunoassay kits. Dogs were randomly divided into three groups and a circular external skeletal fixation system (CESF) was mounted on the tibia. In the first group a distraction osteogenesis procedure of the crus was performed. The second group received an osteotomy without crural lengthening, whereas the third group served as a sham-operated control. Bone formation was assessed using densitometric image analysis of crural radiographs. Despite significant differences in the amount of newly formed bone, this finding was not reflected in the plasma levels of OC and ICTP. In conclusion, OC and ICTP were not efficacious as markers of bone formation and resorption during osteogenesis in this canine model.

Absorptiometry, Photon↗
PubMed2005

Pulsed electromagnetic stimulation of regenerate bone in lengthening procedures.

Distraction osteogenesis for limb lengthening represents the treatment of choice in patients with small stature or limb length discrepancies. Bone lengthening and callus formation requires a long therapy. Pulsed electromagnetic fields (PEMF) are normally used to enhance osteogenesis in patients with non-unions. In this study we investigated whether pulsed electromagnetic fields could be used effectively to encourage callus formation and maturation during limb lengthening procedures. Thirty patients underwent bilateral bone lengthening of the humerus, femur or tibia. At day 10 after surgery, PEMF stimulation was started on one side, for 8 hours/day. Stimulated distraction sites exhibited earlier callus formation and progression, and a higher callus density compared to non-stimulated sites. External fixation could be removed on average one month earlier in PEMF stimulated bones. Our results show that the use of pulsed electromagnetic fields stimulation during limb lengthening allows shortening the time of use of the external fixation.

Body Height↗
PubMed2005

Effect of vascularity on canine distracted tibial callus consolidation.

In the consolidation period of distraction osteogenesis, mineralization occurs before corticalization. We hypothesized that the increased rate of bone mineral density correlates to the density of vascularity in the callus. We unilaterally lengthened the tibia in eight adult beagles. After a waiting period of 7 days, tibiae were lengthened for 30 days. After a consolidation period of an additional 60 days, all animals were euthanized. Just before euthanasia, blood vessels were perfused with 50% w/v barium sulfate solution, and soft radiographs of the distracted callus and the control tibiae were taken. Bone mineral density of the regenerated bones was measured preoperatively by quantitative computed tomography on Days 37, 68, and 98. Increases of the percent bone mineral density (from Day 37 to Day 98 and from Day 68 to Day 98) correlated with the blood vessel volume density ratios on Day 98. Our results suggest that preservation of the higher density of blood vessels in the consolidation period could lead to the better mineralization of the distracted callus.

Angiography↗
PubMed2006

Cleft maxillary distraction versus orthognathic surgery: clinical morbidities and surgical relapse.

BACKGROUND: This is the first randomized controlled study aiming to compare the postoperative clinical morbidities in cleft lip and palate patients treated with distraction osteogenesis versus conventional orthognathic surgery. METHODS: Twenty-nine cleft lip and palate patients with moderate maxillary hypoplasia requiring a maxillary Le Fort I advancement of 4 to 10 mm were randomized into two groups for either internal maxillary distractors or immediate fragment transposition using miniplates and screw fixation. Clinical morbidities were recorded using standardized questionnaires. Skeletal and dental relapses were assessed using lateral cephalometric landmarks. RESULTS: In the distraction group, two of 15 patients developed infection around the distractors and one patient had an occlusal relapse. Among the 14 patients who received conventional orthognathic surgery, the complications included intraoperative hemorrhage (n = 1), plate exposure leading to sinusitis (n = 1), and occlusal relapse (n = 1). In the skeletal relapses of the osteotomy group, a statistically significant vertical relapse of the A point was noted during the second to twelfth weeks when compared with the distraction group. A statistically significant horizontal relapse of the A and P points during the eighth to twelfth weeks was noted when the osteotomy group was compared with the distraction group. CONCLUSIONS: There were no major differences in the clinical morbidities between the osteotomy and distraction groups. Distraction provided better skeletal stability, whereas there was a significant amount of skeletal relapse in the first 12 weeks after conventional cleft maxillary osteotomy.

Adolescent↗
PubMed2000

Experimental study of reconstruction of the temporomandibular joint using a bone transport technique.

PURPOSE: This study investigated the applicability of transport distraction osteogenesis with an internal appliance for reconstruction of the temporomandibular joint (TMJ). MATERIALS AND METHODS: Fifteen millimeters of the ascending ramus, including the condyle and intra-articular disc, was extirpated in 42 white rabbits (3.0 kg weight). After an L-osteotomy was performed from the anterior border of the coronoid process to the posterior border of the mandible, an internal distraction appliance was applied. The transport segment was advanced 0.9 mm/day for 14 days after a 14-day healing period. During a 24-week period after the completion of the lengthening, the rabbits were killed at various intervals. RESULTS: Eight weeks after the completion of the lengthening, the distraction gap between the transport segment and the preexisting mandible was indistinguishable in the radiographs. New bone and a large amount of cartilage were observed microscopically in the distraction gap. New bone was also observed at the leading edge of the transport segment. This bone seemed to form from the surrounding periosteum. At 8 weeks after the completion of lengthening, the mature cortical bone was reconstructed. A collagenous-like structure formed a cap over the leading edge of the transport segment. This cap may substitute for an articular disc. The new bone remodeled and resembled the condyle. CONCLUSION: The bone transport technique is promising for the reconstruction of TMJ.

Analysis of Variance↗
PubMed2001

[Treatment of knee dislocation after callus distraction of the femur--a case report].

We report on the therapy of a complete ventrocranial luxation of the knee joint with leg shortening of 20 cm, which had appeared after diaphyseal distraction osteogenesis in the left thigh at the age of 7 years. The patient presented herself in our clinic at the age of 14 years. After application of an llizarov external fixator,first the luxation was gradually repositioned and afterwards arthrodesis of the knee joint was carried out. After consolidation of the arthrodesis, we removed the external fixator and carried out a unilateral, diaphyseal callus distraction in the left femur. The consolidation of the distraction callus of 12 cm was completed after 9 months and the fixator was removed. At the age of 18 years, 2 years after the treatment was completed, the patient was free of pain and able to walk safely. The remaining shortening of the left leg amounted to 2.5 cm and was balanced in the shoe proportionately.

Adolescent↗
PubMed2006

Clinical study of horizontal alveolar distraction with modified micro bone screws and subsequent implant placement.

The aim of this study was to evaluate the clinical relevance of horizontal distraction osteogenesis (DO) with bone micro screws for reconstructing knife-edge alveolar crests before implant placement. Horizontal DO was performed in upper and lower alveolar crests of seven patients with resorption class IV according to Cawood and Howell. After osteotomy and a 1-week latency period, micro bone screws were reset daily for horizontal expansions by 0.5 mm. Dental implants were placed in the distracted area following a consolidation period of 12 weeks. Computer tomography was performed before DO and implant placement. Morphometric analysis showed a mean gain of 34.01 mm(2) (95% confidence interval [CI]: 10.55-57.48) in bone area and of 3.06 mm (95% CI: 1.81-4.31) in horizontal width, i.e. the horizontal dimension of the alveolus was approximately doubled within the first 5 mm of height. All 12 implants placed into the distracted area fulfilled the success criteria of stable osseointegration after 1 year of functional loading according to Albrektsson and colleagues. Despite the limited number of patients treated, data from the clinical study of horizontal DO with bone micro screws suggest that the generation of sufficient hard tissue in previously knife-edge alveolar crests for subsequent implant placement was possible.

Adult↗
PubMed2002

Molding of the regenerate in mandibular distraction: Part 1: Laboratory study.

Distraction osteogenesis has evolved as a mainstream surgical technique for lengthening and augmentation of the hypoplastic mandible. As clinical experience accumulated, there developed the need to "mold" the bony regenerate to avoid the development of postdistraction malocclusion and to achieve the desired craniofacial form. Although the potential to mold the regenerate has important clinical implications, the safety and efficacy of such an acute manipulation of the bony regenerate form have not yet been investigated in the laboratory. The purpose of this study was to determine if the distraction regenerate could be molded and result in a bony union. Four adult female dogs underwent bilateral mandibular distraction with an external multiplanar device (Stryker, Osteonics). After a latency period of 5 days, the mandibles underwent linear (anteroposterior) and angular (superoinferior) distraction to produce an anterior open bite of approximately 30 degrees. At the conclusion of the distraction procedure, the distraction sites were molded to close the open bite. In two dogs, the maneuver was performed over 3 days by changing the angulation of the devices (gradual molding), and in the other two dogs, molding was achieved with a single movement (acute molding). In the latter, the distraction devices were adjusted and reapplied to allow for anatomical fixation during the consolidation period of 49 days. According to the research protocol, the mandibles were assessed serially by cephalograms and computed tomography (CT) scans. All dogs survived the study without complications. The bony regenerate was easily molded in both groups to close the surgically created open bite. After molding, all the regenerates showed CT scan evidence of solid bone (consolidation), which was classified as "extended" on the Hamanishi scale. After the dogs were killed and soft tissue was removed, the regenerate seemed to be robust on gross examination without any evidence of fibrous nonunion. In addition, histological study of the regenerate confirmed the bony union. The study demonstrates that the mandible can be successfully molded into a desired anatomical position immediately after distraction without producing a fibrous union. Furthermore, it has been demonstrated that the bony regenerate is sufficiently malleable before consolidation to undergo either acute or gradual angular molding without disturbing osteogenic potential. The ability to mold the regenerate without the fear of creating a fibrous union or destroying bony potential provides the surgeon the capability to optimize the dental occlusion and mandibular form as part of the distraction treatment process.

Animals↗
PubMed2003

Segment distraction to reduce a wide alveolar cleft before alveolar bone grafting.

OBJECTIVE: To demonstrate a method for reduction of wide alveolar clefts prior to bone grafting. This method aims to facilitate bone grafting and achieve adequate soft tissue coverage of the graft with attached gingiva. CASE REPORT: Treatment of a patient with bilateral cleft lip and palate with a severe alveolar defect on the left side is illustrated. Distraction osteogenesis was used to mesialize the left segment so that the alveolar cleft was reduced to a minimum. After a 10-week retention period, bone grafting of the reduced alveolar defect was successfully performed. After consolidation of the bone graft, the alveolar cleft was found to have an osseous closure with adequate soft tissue coverage. CONCLUSION: In patients with a wide alveolar cleft, soft tissue coverage with keratinized mucosa can be more readily assured by reducing the alveolar cleft by callus distraction to mesialize the lateral segment prior to bone grafting.

Alveolar Process↗
PubMed2002

A custom mandibular distraction device for the rat.

In the last several years, the rat model has been used as a reliable means of studying distraction osteogenesis (DO). This model has several benefits, including lower cost, the availability of molecular reagents for the rat, and the ability to perform a large number of operations in a short time. We have recently developed an external device that is custom-made for the rat mandible and secured at the mandibular ramus. The device consists of a Leone (Florence, Italy) jackscrew distraction assembly (0.2 mm per one-quarter turn), 2 Luhr L-shaped 0.8-mm five-hole microplates, and four 0.8-mm x 3-mm microscrews (Stryker-Leibinger Corp., Kalamazoo, MI) for fixation. Additionally, there is a methylmethacrylate block that is placed on the lingual surface of the angle of the mandible to support the posterior screws. Sterile surgical technique was used, and the same two surgeons performed all operations. To date, we have operated on 153 Sprague-Dawley rats. The procedure has been well tolerated by the animals. We had 17 postoperative deaths (11% mortality), largely as a result of anesthetic complications. There were no wound infections or dehiscence. A mandible fracture was noted in 6 rats (4%), which occurred at the time of device placement. There were no device dislodgments. Postmortem examination showed the device to be well positioned in all rats, with good callous formation at the distraction site. The rats surpassed their preoperative weight after an average of 9.2 days. These results compare favorably with those of other models currently in use. We have developed a device that is currently being used in the study of DO in the rat mandible. Our device is small in size, does not require wide undermining for its placement, and has had a low incidence of device dislodgment or infection. This model has shown great reproducibility and thus should be effective in its application for the histologic and biochemical investigation of DO in the rat.

Animals↗
PubMed1999

Viscoelastic characterization of mesenchymal gap tissue and consequences for tension accumulation during distraction.

Nonlinear viscoelastic analysis was used to characterize the time-dependent behavior of mesenchymal gap tissue generated during distraction osteogenesis. Six (n = 6) lengthened tibiae were harvested from New Zealand white rabbits at 18 days. This gap tissue was subjected to a series of step displacement tests of increasing magnitude, and force relaxation behavior was monitored. Isochrones in stress-strain space were fit to odd cubic functions of strain. An analytic expression, linear in both e and e3, was developed to predict stress accumulation within the gap tissue as a function of time during distraction. Stress relaxation functions were described well by two-term Prony series. The two time constants determined from mechanical testing results were consistent, suggesting the presence of two fundamental physiologic relaxation processes. Gap tissue stresses were predicted to rise considerably during early stages of lengthening when distraction magnitudes exceeded the clinical norm of 0.25 mm. These differences in tension accumulation were less pronounced by the time lengthening was completed. Specifically, these results may in part explain clinical observations of decreased bone regeneration and altered tissue proliferation and differentiation at higher distraction rates. More generally, this work provides a framework for the rigorous characterization of the viscoelastic properties of biologic tissues ordinarily exposed to step strains.

Animals↗
PubMed2004

Outcome of treatment of Class II malocclusion by intraoral mandibular distraction.

Our aim was to find out long-term results of treatment in patients treated orthodontically and by mandibular distraction osteogenesis. Data on duration of treatment, costs, and results of 26 patients (13 girls and 13 boys) with a mean age of 15 years were analysed. The preoperative cephalograms were compared with those taken at the last follow-up visit. There was a significant reduction in duration of treatment when patients were treated without a first phase that included functional appliances. The differences in costs of orthodontic treatment were not significant. The costs of the operation for distraction were significantly higher compared to BSSO, mainly because of the costs of the distraction devices. Comparison of the cephalograms showed a significant increase in SNB angle, Wits value, ANB angle, overjet, and overbite. The Y-axis, MP/S, and SpP/MP angle increased. Orthodontic treatment and distraction of the mandible was a successful, but more expensive, treatment.

Adolescent↗
PubMed2005

Mandibular distraction: evolution of treatment protocols in hemifacial microsomy.

Osteodistraction is currently used in those disorders presenting with osseus tissue deficit, excellent results having been obtained in the craniofacial complex. The factors contributing to the success of this procedure are a thin layer of subcutaneous tissue, minimum movement of the cutis, good vascularization of the soft tissues, and the good healing that ensues. The good plastic effects on the soft tissues and the possibility of constantly modulating the strength and monitoring the results have led to distraction osteogenesis gaining increasing consensus in the treatment of congenital and acquired deformities and in some selected cases, for the treatment of osseous deficits caused by trauma, postsurgical outcomes, or even severe alveolar deficits. Furthermore, in the last few years, this surgical technique has been successfully used in the treatment of pediatric deformities such as hemifacial microsomia, some severe class II skeletal deformities, and some syndromic cases, such as the treatment of temporomandibular ankylosis outcomes. In our opinion, guidelines in the indications for distraction are mandatory to select the procedure best suited to the pathologic situation of each individual patient.

Adolescent↗