Cranial Vault Distraction: Its Illusionary Effect and Limitation

BACKGROUND

Distraction osteogenesis has some advantages, such as less hazardous complications, less scarring, and fewer bone defects. However, it has not been fully accepted yet because of a unidirectional expansion along the distraction device. Because cranial expansion is limited by scalp tension and soft-tissue scarring, undercorrection of the cranium and relapse of the vault deformities have occasionally been seen on long-term follow-up. These patients also had so much bone defect that the donor bone was inadequate for immediate revisions, and dissection under the scalp was complicated.

METHODS

The authors used distraction osteogenesis to treat 12 cases of craniosynostosis. Five patients were syndromic (two cases of Pfeiffer's syndrome, two cases of Crouzon's disease, and one case of Apert's syndrome), and seven were nonsyndromic (four cases of brachycephaly, two cases of scaphocephaly, and one case of plagiocephaly).

RESULTS

After only unidirectional expansion without vertical reduction, the shape of the cranium was satisfactorily improved, which might have been an illusion caused by the relative reduction attributed to the elongation by the distraction osteogenesis and, in brachycephaly, alteration of the patient's head position resulting from inclination of the facial plane by forehead advancement. However, in scaphocephaly, the unique deformity in the occipital and frontal regions remained after simple distraction. Distraction osteogenesis should be applied for a narrow cranium because the bone defect and scalp closure could pose problems. Radical reshaping should be used in cases of sufficient donor bone and scalp closure. Although additional surgery is unavoidable for device removal, minor revisions can be performed for revision of the irregularity at that time.

CONCLUSION

Except for prolonged treatment, based on minimally invasive operations, distraction cranioplasty might be applied extensively in cases of craniosynostosis.

[Bone mineral density and biomechanical characters of the augmented alveolar ridge by distraction osteogenesis using Ti-Ni shape memory alloy distractor]

OBJECTIVE

To evaluate the quality of the alveolar ridge augmented by Ti-Ni shape memory alloy (Ti-Ni SMA) distractor.

METHODS

All of the mandibular premolars and the first molars were extracted from 12 adult mongrel canines. One month later, box-shaped osteotomy was carried out in the left mandibles and Ti-Ni SMA distractors were imbedded. The right sides served as blank control. The canines were killed 3 or 6 months later and specimens were taken from corresponding area of the experiment sides and the control. Bone mineral density and biomechanical function were measured.

RESULTS

Bone mineral density, ultimate compressive strength and Young's Modules of the augmented ridge were lower than the blank control three months after distraction. But the indexes increased and showed no significant difference with the control six months after distraction.

CONCLUSIONS

The canines mandibular posterior alveolar ridge could be augmented by distraction osteogenesis using Ti-Ni SMA distractor, and the new bone is strong enough for implant placement.

Effect of pulsed electromagnetic fields on maturation of regenerate bone in a rabbit limb lengthening model

To study the effect of applying pulsed electromagnetic fields (PEMF) during the consolidation phase of limb lengthening, a mid-tibial osteotomy was performed in 18 adult New Zealand White rabbits and an external fixator was applied anteromedially. Animals were randomly assigned to treatment and control groups. After a 7-day latency period, the tibiae were distracted 0.5 mm every 12 h for 10 days. The treatment group received a 20-day course of PEMF for 60 min daily, coinciding with initiation of the consolidation phase. The control group received sham PEMF. Radiographs were performed weekly after distraction. Animals were euthanized 3 weeks after the end of distraction. Radiographic analysis revealed no significant difference in regenerate callus area between treatment and control tibiae immediately after distraction, at 1 week, 2 weeks, or 3 weeks after distraction ( p = 0.71, 0.22, 0.44, and 0.50, respectively). There was also no significant difference in percent callus mineralization ( p = 0.96, 0.69, 0.99, and 0.99, respectively). There was no significant difference between groups with respect to structural stiffness ( p = 0.80) or maximal torque to failure ( p = 0.62). However, there was a significant positive difference in mineral apposition rate between groups during the interval 1-2 weeks post-distraction ( p < 0.05). This difference was no longer evident by the interval 2-3 weeks post-distraction. While PEMF applied during the consolidation phase of limb lengthening did not appear to have a positive effect on bone regenerate, it increased osteoblastic activity in the cortical bone adjacent to the distraction site. Since the same PEMF signal was reported to be beneficial in the rabbit distraction osteogenesis when applied during distraction phase and consolidation phase, application of PEMF in the early phase may be more effective. Further work is necessary to determine optimal timing of the PEMF stimulation during distraction osteogenesis.

Treatment of craniosynostosis by distraction osteogenesis

PURPOSE

Craniosynostosis patients treated with one-stage cranioplasty often have bleeding from the dura mater, fluid collection in the extradural space, and poor wound healing due to skin overstretching. To avoid these complications, we began using distraction osteogenesis. To determine the advantages and disadvantages of the procedure, we retrospectively compared distraction osteogenesis with conventional cranioplasty.

PATIENTS AND RESULTS

We treated 24 patients with fronto-orbital advancement. Fifteen had one-stage cranioplasty; 9 received distraction osteogenesis. The one-stage operation patients averaged 25.5 months of age at surgery, 289 min of operating time, and 154 ml of intraoperative blood loss. For the distraction group, the average age was 16.6 months, average operating time was 196 min, and average blood loss was 76 ml.

CONCLUSIONS

Compared with one-stage cranioplasty patients, distraction osteogenesis patients had significantly less intraoperative bleeding and shorter operating times. The disadvantages of distraction treatment were the need for multiple surgeries, prolonged hospitalization, wound infection, and dislocation of the distraction device.

Expression of osteotropic growth factors and growth hormone receptor in a canine distraction osteogenesis model

Osteotropic growth factors play an important role in bone metabolism. Nevertheless, knowledge about their expression in relation to distraction osteogenesis remains limited. The aim of the present study was to determine the expression of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), and bone morphogenetic protein 2 (BMP-2) in distraction-induced bone regeneration. Expression of these factors was assessed during the consolidation phase, comparing distraction osteogenesis with osteotomy-induced bone formation. Real-time PCR was performed as a semiquantitative measurement of mRNA, and the relative expression levels of these factors were determined. In addition, plasma GH profiles and plasma concentrations of IGF-I, IGF-II, and insulin-like growth factor-binding protein 4 and -6 (IGFBP-4 and -6) were measured to assess their potential systemic role during bone formation. Expression of GHR, IGF-I, and BMP-2 had significantly increased in comparison with the expression of these factors in mature bone. Expression of GHR was significantly higher in distraction-induced bone regenerate than in osteotomy-induced bone. No significant differences were found for the expression of IGF-I and BMP-2 between distraction and osteotomy. Plasma concentrations of GH, IGF-I, IGF-II, IGFBP-4, and IGFBP-6 did not demonstrate any significant differences between treatment groups and controls. Upregulation of GHR expression in distraction osteogenesis may enhance sensitivity to endogenous systemic GH and thus promote consolidation of the regenerated bone. Changes in the systemic osteotropic growth factors GH, IGF-I, IGF-II, IGFBP-4, and IGFBP-6 do not seem to be of importance during distraction osteogenesis.

Colocalization of c-Src (pp60src) and bone morphogenetic protein 2/4 expression during mandibular distraction osteogenesis: in vivo evidence of their role within an integrin-mediated mechanotransduction pathway

Craniofacial distraction osteogenesis (DO) is an evolving reconstructive technique with expanding applications for the treatment of bony deficiencies of the facial skeleton. Mechanical force has been known to play a fundamental role in modulating sustained osteogenic response and therefore is believed to function as a critical regulator of DO. We hypothesize that key clustering components of an integrin-mediated signaling pathway, including c-Src (pp60), are necessary for mediating the response to mechanical force. The specific aim of this study is to demonstrate up-regulation of a key focal adhesion molecule, c-Src, selectively in new bone formation subject to the mechanical forces of distraction and to demonstrate a lack of that same up-regulation in new bone formation associated with simple fracture healing. An additional specific aim is to demonstrate colocalization of c-Src expression and bone morphogenetic protein (BMP 2/4) expression during mandibular DO. Using a rat model of mandibular DO, c-Src and BMP 2/4 expression were evaluated in critical size defects, subcritical size defects, and mandibles undergoing gradual distraction. Osseous regeneration was observed in the course of gradual distraction; this process was associated with increased expression of c-Src. Furthermore, the presence of BMP 2/4 closely approximated c-Src expression spatially and temporally, suggesting a link between cytoplasmic focal adhesion activation and the resultant nuclear regulation of osteogenic protein expression. In significant contradistinction, minimal c-Src expression was found in the subcritical-sized defects where the fractures healed secondarily but where no gradual distraction was performed. Instead, the new bone formation inherent in the secondarily healed subcritical-sized defects demonstrated expected BMP 2/4 expression but was devoid of an up-regulation of c-Src. Finally, as expected, minimal expression of both c-Src and BMP was found in fibrous nonunion specimens. C-src expression was observed during gradual distraction; furthermore, minimal c-Src expression was visualized during subacute and critical-size defect fracture healing. C-Src expression also closely approximated BMP expression during DO. These findings that c-Src expression is found primarily only during conditions of cyclic distraction forces strongly implicates that mechanical force during gradual distraction is associated with c-Src expression. These results provide in vivo support for previous in vitro evidence that mechanical force profoundly influences osseous regeneration during distraction osteogenesis by means of a c-Src dependent mechanotransduction pathway, resulting in increased expression of osteogenic proteins, including BMP 2/4.

CT-basierte Distraktion des Unterkiefers mit Gelenkrekonstruktion und Impaktation der Maxilla bei Kiefergelenkankylose

BACKGROUND

The possibilities for computer assisted planning and its surgical conversion with stereolithographic templates are shown for complex maxillofacial surgical interventions.

CASE REPORT

We describe the case of a patient with extreme micrognathia due to an ankylosis of the temporomandibular joint. In addition to the exact determination of the osteotomy lines on the mandibular angle and the segment osteotomy of the maxilla, vectors of the bidirectional osteodistraction were also predictable.

CONCLUSION

In comparison with the conventional procedures, computer assisted planning achieved a much higher degree of precision and safety with reduced complication rates. The CMF module is a component of the SimPlant software which enables the precise planning of osteotomies and osteodistractions.

Osteoclastogenic activity during mandibular distraction osteogenesis

Mandibular distraction osteogenesis is a well-developed clinical modality for the treatment of craniofacial deformities and dental arch discrepancies, in combination with orthodontic treatment. However, in our previous study, orthodontic tooth movement into the distraction gap caused severe root resorption. The present study aimed to clarify the osteoclastogenic activity of cells in the distraction gap. We hypothesized that the gene expression of osteoclastogenic- and osteoclast-supporting molecules in osteoblasts and stromal cells would increase at distraction sites during the consolidation period. An animal model experiment involving rabbits was designed for mandibular distraction osteogenesis and subjected to in situ hybridization analysis. The number of osteoclasts was larger in the distraction gap during the early consolidation period than in normal controls, due to an increase of gene expression for osteoclastogenic cytokines in osteoblasts. It was concluded that osteoclastogenic and osteoclastic activities are stimulated at distraction sites during the early consolidation period.

Relationships between tissue dilatation and differentiation in distraction osteogenesis

Mechanical factors modulate the morphogenesis and regeneration of mesenchymally derived tissues via processes mediated by the extracellular matrix (ECM). In distraction osteogenesis, large volumes of new bone are created through discrete applications of tensile displacement across an osteotomy gap. Although many studies have characterized the matrix, cellular and molecular biology of distraction osteogenesis, little is known about relationships between these biological phenomena and the local physical cues generated by distraction. Accordingly, the goal of this study was to characterize the local physical environment created within the osteotomy gap during long bone distraction osteogenesis. Using a computational approach, we quantified spatial and temporal profiles of three previously identified mechanical stimuli for tissue differentiation-pressure, tensile strain and fluid flow-as well as another candidate stimulus-tissue dilatation (volumetric strain). Whereas pressure and fluid velocity throughout the regenerate decayed to less than 31% of initial values within 20 min following distraction, tissue dilatation increased with time, reaching steady state values as high as 43% strain. This dilatation created large reductions and large gradients in cell and ECM densities. When combined with previous findings regarding the effects of strain and of cell and ECM densities on cell migration, proliferation and differentiation, these results indicate two mechanisms by which tissue dilatation may be a key stimulus for bone regeneration: (1) stretching of cells and (2) altering cell and ECM densities. These results are used to suggest experiments that can provide a more mechanistic understanding of the role of tissue dilatation in bone regeneration.

[Growth defects of fibular flaps in children]

BACKGROUND

Mandibular reconstruction with fibula free flap is a challenge in pediatric patients because of the size of the bone and absence of growth without epiphyseal transplantation.

CASE REPORT

We report 2 cases of free fibula flap in children for mandibular reconstruction. The 2 patients presented with growth insufficiency of the bone graft after few years of evolution.

DISCUSSION

Growth insufficiency was treated with different surgical procedures which were discussed We review the consequences on growth after fibula free flap and the specific indications to achieve epiphyseal fibular growth in children.

[Distraction osteogenesis in orthodontic surgery of the mandible]

Distraction osteogenesis is a bone creating procedure that can contribute materially to the treatment of Class II dento-skeletal disorders where the mandible is under-sized. Still, the serious commitments this treatment demands and the unpredictability of its occlusal results oblige practitioners to pinpoint precisely the indications for its use. We now believe that distraction osteogenesis can beneficially be employed for: 1--Adults with Class II malocclusions, a small mandible, and a lack of harmony between tooth and jaw size. This bone growing technique makes it possible to treat these patients without the extraction of premolars that would have been necessary in the traditional preparation for orthognathic surgery. 2--Patients whose mandibles are diminished in size in the area of the symphasis. Distraction osteogenesis of this anterior segment is the only way they can be treated without reduction of tooth structure or excessive labial tipping of teeth. 3--Some patients with short, or moderately short rami. We do not, at this time, believe that distraction osteogenesis is indicated for the treatment of any other kind of dento-facial deformity. But, in the future, improvement of surgical techniques and the miniaturization of appliances will doubtless extend its scope.

[Experimental study on distraction osteogenesis for reconstruction of maxillary defects with replacement of transplant disk in goats]

PURPOSE

This study was aimed to set up a new method for reconstruction of maxillary defect with distraction osteogenesis through an animal experiment.

METHODS

11 adult goats were randomly divided into 2 groups (9 in the experimental group and 2 in the control group) in this study. 3 subgroups were set up in the experimental group based on the consolidation period. Other 2 goats were chosen as the control group. Maxillary defect was made firstly through partial maxillectomy for the experimental group. Length of the defects was from 12 to 14mm with an average of 12.7mm. A transport disc was then made through anterior Le Fort I osteotomy and it would be shifted backward for the closure of the defect. Only maxillary defect was made for the control group. Distraction was activated after a latency of 7 days at a rate of 0.4mm twice a day for 15-18 days.

RESULTS

Bone defects in the maxilla were well repaired when the transport disc was distracted back to its original position. Radiology and histology demonstrated good new bone formation in the distraction gap.

CONCLUSIONS

Transport distraction osteogenesis would be a reasonable method for reconstruction of maxillary defect.

Systemic regulation of angiogenesis and matrix degradation in bone regeneration--distraction osteogenesis compared to rigid fracture healing

Aim of this study was the investigation of systemic biochemical regulation mechanisms of bone regeneration by angiogenic and matrix-degrading enzymes during distraction osteogenesis compared to rigid osteotomy bone healing. Serum samples of 10 otherwise healthy patients with callus distraction for lower limb-lengthening and 10 osteotomy patients undergoing elective axis correction have been collected prospectively in a standardized time schedule before and up to 6 months after the procedure. At the end of the individual investigation period, concentrations of metalloproteinases (MMP-9, -13), tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2) and the angiogenic factors angiogenin and VEGF have been detected by use of commercially available enzyme immunoassays. Results have been compared to our preliminary study on proMMP-1-3. In distraction osteogenesis, significantly elevated serum concentrations compared to baseline could be detected postoperatively for proMMP-1, MMP-9, TIMP-1, angiogenin and VEGF but not for proMMP-2, proMMP-3 or TIMP-2. In patients with rigid osteotomy healing, MMP-9, TIMP-1, TIMP-2, angiogenin and VEGF were significantly increased respectively. Comparison of both patient collectives revealed significantly higher increases of serum proMMP-1, VEGF and TIMP-1 in distraction patients during the lengthening period and significantly higher serum concentrations of TIMP-2 in late fracture healing period in osteotomy patients. Serum levels of MMP-13 were below the lowest standards, and therefore quantitative analysis was not possible. Bone regeneration in distraction osteogenesis and rigid osteotomy healing is accompanied by systemic increase of matrix-degrading and angiogenic factors in a certain time course and quantity. This might reflect biochemical regulation of local bone healing in the circulation. ProMMP-1, VEGF and TIMP-1 seem to be key regulatory factors during distraction osteogenesis.

[Study of the expression of integrin alphaV beta3 in mandibular distraction osteogenesis]

OBJECTIVE

To investigate the expression and distribution pattern of Integrin alphaV beta3 (ItgalphaV beta3) in course of distraction 44 adults New Zealand white osteogenesis and to quest for the function of ItgalphaV beta3 in distraction osteogenesis (DO).

METHODS

rabbits were selected and divided randomly into 3 groups: DO, bone fracture and normal group. There were 20, 20 and 4 rabbits in each group separately. Animal models were established and animals were killed at different time points. Sections were stained by IHC method. Distribution and expression pattern of ItgalphaV beta3 were observed by semi-quantitative technique, and the results were managed with statistic methods.

RESULTS

The expression of ItgalphaV beta3 was found both in the DO and bone fracture groups. The positive staining was seen mainly in vascular endothelial cells on cytomembrane and in cytoplasm. The staining intensity of group of DO was higher than that of the bone fracture group.

CONCLUSION

ItgalphaV beta3 plays an important role in promoting the process of DO.

Radiographic Evaluation of Alveolar Distraction Osteogenesis: Analysis of 60 Cases

PURPOSE

The aim of this study was to evaluate radiographically the effectiveness of alveolar distraction osteogenesis (ADO) technique for vertical reconstruction of atrophy alveolar ridges in partially edentulous patients.

MATERIALS AND METHODS

A total of 60 vertical distraction osteogenesis procedures were performed in 55 patients. Two panoramic radiographies were performed in all patients, one the day before the beginning of distraction, and one after consolidation period, 12 weeks postoperatively. The radiographic analysis consisted of obtaining the amount of the vertical bone gain (VBG) in each radiography. For this, we obtained initially the magnification factor (MF) of each panoramic radiography by dividing the real size (RS) of the activation rod among the image size (IS) of the activation rod. After this, to obtain the VGB, we measured initially the length of the distracton preactivation (LD1), which consisted of the distance between the superior portion of the basal plate and the superior portion of the transport plate, multiplying by the MF. Then, we measured the length of the distraction postactivation (LD2), using the same method described before, in radiographies performed 12 weeks postoperatively. The VBG was obtained using the following formula: VBG = LD2 - LD1. The results were applied to descriptive statistical analysis. Complications were also investigated during all of the treatments.

RESULTS

The mean alveolar distraction achieved in 60 cases was 6.27 mm (range, 0 to 10.83 mm). According to the region treated, 51.6% were in the posterior mandible (mean VBG, 4.60 mm), 36.66% were in the anterior maxilla (mean VBG, 7.46 mm), 8.33% were in the anterior mandible (mean VBG, 6.73 mm), and 3.33% were in the posterior maxilla (mean VBG, 6.32 mm). The overall rate of complications that compromised the success of the technique was 8.44%. The increased radiopacity of the distracted region could be observed in the 12-week period after surgery.

CONCLUSIONS

The ADO technique was demonstrated to be an effective tool to treat vertical defects of the alveolar ridge with a success rate of 91.66%. Our radiographic analysis seems to be an important tool in verifying the technique as well as planning implant placement after ADO.

Selective soft tissue release preserves growth plate architecture during limb lengthening

Although distraction osteogenesis has proven successful in children, concerns remain regarding potential growth inhibition of the lengthened limb. Twenty-one 8-week-old New Zealand White rabbits underwent a unilateral 40% tibial lengthening with the contralateral tibia as control. The animals were divided into Achilles tendon release and non-release groups. Radiographs and histomorphometric analysis of the proximal tibial growth plate was performed 5 and 10 weeks after distraction. The corrected length of tibias without tenotomy was significantly shorter than the contralateral controls, whereas those with tenotomy were statistically equivalent to the contralateral control tibias. Histologically, the operated limbs without tenotomy showed a significant decrease in thickness and loss of cellular architecture of the proximal tibial growth plate compared with the tenotomy groups, which were of near-normal appearance. A concomitant tendo Achilles lengthening performed with 40% tibial lengthening preserves proximal tibial growth plate architecture in this model.

Callus mineralization following distraction osteogenesis of the mandible monitored by scanning acoustic microscopy (SAM)

BACKGROUND

Scanning acoustic microscopy uses ultrasound to analyse histomorphology of tissues with microscopic resolution and delivers data about physical properties of the specimen.

MATERIAL AND METHODS

Bony consolidation was monitored by scanning acoustic microscopy in 12 embedded specimens of dog mandibles after distraction osteogenesis. Increasing mineralization was detected by measurements of acoustic impedance (Z).

RESULTS

There was a strong correlation between acoustic impedance and time of consolidation. Measurements of the speed of sound (v) provided specific information about non-mineralized zones of the distracted area. Distribution of density in the distracted area could be reconstructed by using the measurements of acoustic impedance and speed of sound.

CONCLUSION

The method seems suitable for studying bone remodelling qualitatively and quantitatively.

Determination of ankle external fixation stiffness by expedited interactive finite element analysis

Interactive finite element analysis holds the potential to quickly and accurately determine the mechanical stiffness of alternative external fixator frame configurations. Using as an example Ilizarov distraction of the ankle, a finite element model and graphical user interface were developed that provided rapid, construct-specific information on fixation rigidity. After input of specific construct variables, the finite element software determined the resulting tibial displacement for a given configuration in typically 15s. The formulation was employed to investigate constructs used to treat end-stage arthritis, both in a parametric series and for five specific clinical distraction cases. Parametric testing of 15 individual variables revealed that tibial half-pins were much more effective than transfixion wires in limiting axial tibial displacement. Factors most strongly contributing to stiffening the construct included placing the tibia closer to the fixator rings, and mounting the pins to the rings at the nearest circumferential location to the bone. Benchtop mechanical validation results differed inappreciably from the finite element computations.

Treatment protocol for unilateral cleft lip and palate patients: questioned by two case reports

BACKGROUND

The types and severity of clefts as well as palatal development and growth in children with repaired cleft lip and palate deformities can vary greatly. Independent of the technique used surgery produces scar tissue, which restricts palatal growth so that by the second decade many patients have an underdeveloped maxilla. Experience has shown that the maxillary retrognathism found in many cleft patients is not amenable to nonsurgical correction. Few long-term studies have evaluated the procedures, sequencing and timing of the treatment methods found to give the best results. This lack of reliable information means there is a serious gap in our ability to assess the value of different treatment modalities.

AIMS AND METHODS

From the viewpoint of orthodontics, this article describes the treatment protocol used by the cleft lip and palate team at the University Hospitals of the KU Leuven. The present treatment protocol is illustrated and questioned by two cases. The roles of prediction of facial growth and distraction osteogenesis are discussed.

Distraction osteogensis: a surgical option for restoring missing tissue in the anterior esthetic zone

Common causes of alveolar defects include bone resorption due to loss of teeth, infection, or trauma. There is often insufficient height or width of residual bone, and ridge augmentation may be required prior to implant placement. These defects range from small alveolar deficiencies to more complex, extensive bony defects. Various techniques are available for reconstructing alveolar ridges. Without augmentation, dental implants may have to be placed in anatomically unfavorable positions or have adverse angulations. These position/angulation compromises can lead to esthetic dissatisfaction, mechanical overload, and possibly implant loss. Both bone grafting and distraction osteogenesis are predictable methods for restoring missing tissue.

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.

Growth factor expression following clinical mandibular distraction osteogenesis in humans and its comparison with existing animal studies

AIM

Lengthening the mandible by distraction osteogenesis (DO) is nowadays a well recognized technique in maxillofacial surgery. In this study growth factor expression profiles were examined in biopsies taken from six patients undergoing mandibular DO and compared with findings from a sheep model for mandibular DO.

STUDY DESIGN

In all patients (and sheep), the ascending ramus was distracted 10-15 mm at a rate of 1mm/day using an intraoral device. Biopsies were taken from the centre of the distraction zone 21 days after completion of distraction. Using standard immunohistochemical techniques, samples were stained for platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-beta), basic fibroblast growth factor (bFGF) and bone morphogenetic proteins-2, -4 and -7 (BMP-2, -4, -7), matrix metalloproteinases-1 and -3 (MMP-1, -3), the vascular endothelial growth factor (VEGF), a marker for endothelial cells (CD-31) and type IV collagen (Col IV).

RESULTS

Positive staining for PDGF, bFGF, TGF-beta, BMP-2, -4, and -7 was noted in cells and matrix components. There was intense staining for MMP-1. Strong staining for CD-31 and COL IV was observed adjacent to vessels. VEGF staining was less specific. Similar findings were noted in the sheep model.

CONCLUSION

Growth factor expression in the human distraction site is similar to that in the sheep model.

[Treatment of gigantocellular tumor of the tibia metaphysis by means of the Ilizarov method--a case study]

The authors show a 36-year old female patient with a gigantocellular tumor of the distal metaphysis of the left tibia (stage III by Campanacci). A 7.6 cm long distal articular defect of the tibia has been formed by radical segmentary resection. The defect was compensated by the extension of the rest of the tibia; whereas the support function of the limb was provided through tibio-talar arthrodesis. 5.5 years after the surgery, there are no signs of local relapses; the patient walks without any orthopedic aids and works at the same job as prior to the operation.

[The treatment of "critical ischemia" of the limbs in endarteritis obliterans by thickening of the tibial bone]

The autors report their experience in the treatment of the "critical ischemia" in 8 patients with arterial occlusion of the lower limbs in endarteritis obliterans. All patients were treated by thickening of the tibia using the Ilizarov apparatus for distraction osteosynthesis. In all cases the operative treatment ensured lowering of the amputation level, forming of the functional stump and long-lasting remission of the illness.

Evaluation of recombinant human bone morphogenetic protein-2 in mandibular distraction osteogenesis in rabbits: Effect of dosage and number of doses on formation of bone

We evaluated the dose- and time-dependent response of recombinant human bone morphogenetic protein-2 (rhBMP-2) to the formation of bone in mandibular distraction osteogenesis. Twenty-one adult white New Zealand rabbits (3.0-3.8 kg) were used to establish the mandibular distraction model, 18 of which completed the experiment. Eight rabbits were given rhBMP-2 360 microg and eight 1080 microg; two were given no rhBMP-2. The fluids were injected into the regenerating bone at three different time sequences (days 5, 8, and 11 of active distraction; days 5 and 11 of active distraction; and day 11 of active distraction alone). After four weeks of consolidation, the specimens were harvested and examined radiographically by micro-computed tomography (micro-CT), and histologically. The formation and remodelling of bone in distraction osteogenesis was significantly increased by the addition of rhBMP-2, and the increase was dose-dependent. There was no significant difference between different dosage regimens. A single injection of rhBMP-2 at the end of the distraction phase was as effective as multiple injections.