Determining the optimal time for consolidation after distraction osteogenesis

Combining High-Resolution Hard X-ray Tomography and Histology for Stem Cell-Mediated Distraction Osteogenesis

Distraction osteogenesis is a clinically established technique for lengthening, molding and shaping bone by new bone formation. The experimental evaluation of this expensive and time-consuming treatment is of high impact for better understanding of tissue engineering but mainly relies on a limited number of histological slices. These tissue slices contain two-dimensional information comprising only about one percent of the volume of interest. In order to analyze the soft and hard tissues of the entire jaw of a single rat in a multimodal assessment, we combined micro computed tomography (µCT) with histology. The µCT data acquired before and after decalcification were registered to determine the impact of decalcification on local tissue shrinkage. Identification of the location of the H&E-stained specimen within the synchrotron radiation-based µCT data collected after decalcification was achieved via non-rigid slice-to-volume registration. The resulting bi- and tri-variate histograms were divided into clusters related to anatomical features from bone and soft tissues, which allowed for a comparison of the approaches and resulted in the hypothesis that the combination of laboratory-based µCT before decalcification, synchrotron radiation-based µCT after decalcification and histology with hematoxylin-and-eosin staining could be used to discriminate between different types of collagen, key components of new bone formation.

Pediatric Craniofacial Surgery: A Review for the Multidisciplinary Team

Pediatric craniofacial surgery is a specialty that grew dramatically in the 20th century and continues to evolve today. Out of the efforts to correct facial deformities encountered during World War II, the techniques of modern craniofacial surgery developed. An analysis of the relevant literature allowed the authors to explore this historical progression.

Current advances in technology, tissue engineering, and molecular biology have further refined pediatric craniofacial surgery. The development of distraction osteogenesis and the progressive study of craniosynostosis provide remarkable examples of this momentum. The growing study of genetics, biotechnology, the influence of growth factors, and stem cell research provide additional avenues of innovation for the future. The following article is intended to reveal a greater understanding of pediatric craniofacial surgery by examining the past, present, and possible future direction. It is intended both for the surgeon, as well as for the nonsurgical individual specialists vital to the multidisciplinary craniofacial team.

A new way to anchor the external device in mandibular distraction: three case reports with a Pierre Robin sequence

Pierre Robin sequence is a pathology derived from alteration in the first and second branchial arch. Patients have breathing problems due to micrognathia and glossoptosis, causing severe upper airway obstruction. One surgical treatment is distraction osteogenesis. Three patients with Pierre Robin sequence (case 1, 3 months old; cases 2 and 3, 1 month old) with severe upper airway obstruction requiring mechanical ventilator assistance, underwent mandibular distraction osteogenesis prematurely with a new anchoring system, thus avoiding tracheostomy and its consequences. An intraoral approach was used to avoid scarring. A new anchoring device with transfixing Kirschner wire in the proximal (mandibular ramus) and distal segment (chin zone) was used. This diminishes the risk of distractor device displacement, guaranteeing optimal stability. A more anterior installation reduces the risk of damaging tooth buds in the mandibular body and the inferior alveolar nerve. The more anterior the fixation, the more horizontal the distraction vector becomes. The position and stability of the device are crucial. In these three patients the placement of two transfixing Kirschner wires using an intraoral approach showed good results and stability during the period of distraction and consolidation, with optimal results on the upper airway, avoiding tracheostomy.

Regenerate healing outcomes in unilateral mandibular distraction osteogenesis using quantitative histomorphometry

BACKGROUND

The authors' goal was to ascertain regenerate bone-healing metrics using quantitative histomorphometry at a single consolidation period.

METHODS

Rats underwent either mandibular distraction osteogenesis (n = 7) or partially reduced fractures (n = 7); their contralateral mandibles were used as controls (n = 11). External fixators were secured and unilateral osteotomies performed, followed by either mandibular distraction osteogenesis (4 days' latency, then 0.3 mm every 12 hours for 8 days; 5.1 mm) or partially reduced fractures (fixed immediately postoperatively; 2.1 mm); both groups underwent 4 weeks of consolidation. After tissue processing, bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, and osteocyte count per high-power field were analyzed by means of quantitative histomorphometry.

RESULTS

Contralateral mandibles had statistically greater bone volume/tissue volume ratio and osteocyte count per high-power field compared with both mandibular distraction osteogenesis and partially reduced fractures by almost 50 percent, whereas osteoid volume/tissue volume ratio was statistically greater in both mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles. No statistical difference in bone volume/tissue volume ratio, osteoid volume/tissue volume ratio, or osteocyte count per high-power field was found between mandibular distraction osteogenesis specimens and partially reduced fractures.

CONCLUSIONS

The authors' findings demonstrate significantly decreased bone quantity and maturity in mandibular distraction osteogenesis specimens and partially reduced fractures compared with contralateral mandibles using the clinically analogous protocols. If these results are extrapolated clinically, treatment strategies may require modification to ensure reliable, predictable, and improved outcomes.

Meta-analysis of mandibular distraction osteogenesis: clinical applications and functional outcomes

BACKGROUND

Mandibular distraction osteogenesis has been used effectively to treat syndromic craniofacial deformities. In recent years, its scope of application has widened to include treatment of airway obstruction in adults and children and nonsyndromic class II mandibular hypoplasia. So far, there has been no evidence-based review of mandibular distraction osteogenesis for mandibular lengthening.

METHODS

Two rounds of searches were performed by two independent assessors. The first-round PubMed search used the keywords "mandible" and "distraction osteogenesis." In the second-round search, the reference lists of the articles were retrieved. For both rounds, abstracts and then full articles were reviewed and selected on the basis of a set of inclusion and exclusion criteria.

RESULTS

The 178 retrieved articles yielded 1185 mandibular distraction osteogenesis patients: 539 received unilateral mandibular distraction osteogenesis and 646 received bilateral mandibular distraction osteogenesis. Mandibular distraction osteogenesis was reported to improve facial asymmetry and retrognathia (50.1 percent), correct the slanted lip commissure (24.7 percent), and improve or level the mandibular occlusal plane (11.1 percent) in unilateral asymmetry cases, whereas bilateral mandibular distraction osteogenesis was shown to be effective in preventing tracheostomies for 91.3 percent of neonates or infants with respiratory distress, and in relieving symptoms of obstructive sleep apnea for 97.0 percent of children and 100 percent of adult patients.

CONCLUSIONS

Mandibular distraction osteogenesis is effective in treating craniofacial deformities, but further clinical trials are required to assess the long-term stability and to compare the treatment with conventional treatment methods, especially in cases of obstructive sleep apnea or class II mandibular hypoplasia.

Les séquelles maxillaires dans les fentes labioalvéolopalatovélaires. Place de la distraction ostéogénique

A high rate of cleft patients present with maxillary hypoplasia. Most of the growth defects concern the anteroposterior axis of the maxilla. Before bone lengthening by distraction osteogenesis, orthognathic surgery was the only alternative treatment for maxillary hypoplasia. Several studies showed the lack of stability after conventional surgery. In this article reviewing the literature concerning all bone lengthening procedures, the authors discuss published data on maxillary distraction osteogenesis by external and internal devices. Indications of distraction in growing children as an interceptive step are discussed.

Effect of thrombin peptide 508 (TP508) on bone healing during distraction osteogenesis in rabbit tibia

Thrombin-related peptide 508 (TP508) accelerates bone regeneration during distraction osteogenesis (DO). We have examined the effect of TP508 on bone regeneration during DO by immunolocalization of Runx2 protein, a marker of osteoblast differentiation, and of osteopontin (OPN) and bone sialoprotein (BSP), two late markers of the osteoblast lineage. Distraction was performed in tibiae of rabbits over a period of 6 days. TP508 (30 or 300 μg) or vehicle was injected into the distraction gap at the beginning and end of the distraction period. Two weeks after active distraction, tissue samples were harvested and processed for immunohistochemical analysis. We also tested the in vitro effect of TP508 on Runx2 mRNA expression in osteoblast-like (MC3T3-E1) cells by polymerase chain reaction analysis. Runx2 and OPN protein were observed in preosteoblasts, osteoblasts, osteocytes of newly formed bone, blood vessel cells and many fibroblast-like cells of the soft connective tissue. Immunostaining for BSP was more restricted to osteoblasts and osteocytes. Significantly more Runx2- and OPN-expressing cells were seen in the group treated with 300 μg TP508 than in the control group injected with saline or with 30 μg TP508. However, TP508 failed to increase Runx2 mRNA levels significantly in MC3T3-E1 cells after 2–3 days of exposure. Our data suggest that TP508 enhances bone regeneration during DO by increasing the proportion of cells of the osteoblastic lineage. Clinically, TP508 may shorten the healing time during DO; this might be of benefit when bone regeneration is slow.

Assessment of distraction regenerate using quantitative bone scintigraphy

In this study, we examined whether quantitative bone scintigraphy can be used to assess new bone formation following distraction osteogenesis (DO). A vertical osteotomy was performed on the right hemimandible of male Sprague-Dawley rats, and a custom-made distraction device was applied. Following the gradual distraction, rats were divided into 2 subgroups, the second and fourth week. Cephalograms were taken and scintigraphic and histomorphometric analysis was performed at the second and fourth week. Scintigraphic findings showed good correlation with histomorphometric results. Results were compared with sham-operated (skin and muscle incision and placement of pin but no osteotomy) and acute distraction (5-mm acute distraction) groups. Scintigraphic mean uptake ratios were significantly higher in the gradual distraction group compared with the sham-operated and acute distraction groups. Quantitative bone scintigraphy is a promising method for the assessment of DO and consolidation. It could offer objective qualitative and quantitative data for the noninvasive evaluation of bony regenerate.

Distraction Osteogenesis in Adolescents with Maxillary Arch Deficiency and Dental Crowding: A 3-Year Follow-Up

BACKGROUND

In this study, the authors evaluated the long-term results after using anterior segmental osteotomy and distraction osteogenesis for the correction of sagittal maxillary deficiency associated with dental crowding.

METHODS

Six young adolescents (four boys and two girls) underwent surgery and distraction at a mean age of 11.2 years (range, 10 to 12 years) and were followed up for 3 years. A tooth-borne distraction device was used for interdental distraction. The evaluation consisted of hard- and soft-tissue profile analysis and dental arch measurements before, immediately after, and 3 years after distraction.

RESULTS

The results showed that the facial profile, the occlusion, and the dental crowding could be successfully corrected and that the results were stable after 3 years' follow-up. The mean facial convexity angle was changed from 1 to 8 degrees. The average advancement at point A was 4 mm and the SNA increased by an average of 4 degrees. Lengthening of the dental arch by an average of 4 mm created approximately 8 mm of new space, sufficient to resolve the dental crowding in all patients, thus avoiding an extraction of healthy teeth.

CONCLUSION

The results of this study demonstrated that anterior segmental maxillary osteotomy combined with distraction osteogenesis offers an alternative for the treatment of adolescents suffering from sagittal maxillary deficiency with dental crowding.

Evaluation of delayed-image bone scintigraphy to assess bone formation after distraction osteogenesis in dogs

OBJECTIVE

To quantitatively assess distraction-induced bone formation in a crural lengthening model in dogs by use of delayed-image bone scintigraphy.

ANIMALS

12 mature Labrador Retrievers.

PROCEDURE

Dogs were randomly allocated to 1 of 3 groups. A circular external skeletal fixation system was mounted on the right crus of each dog. Osteotomy of the distal portion of the tibia and fibula was performed in groups 1 and 2 and was followed by a lengthening procedure of 10 mm in the first group only. The third group served as sham-operated controls. Delayed-image bone scintigraphy with technetium-99m hydroxy methylene diphosphonate was performed 2, 4, and 6 weeks after surgery. Delayed-image-to-region-of-interest, delayed-image-to-crural, and delayed-image-to-femoral scintigraphic activity ratios were calculated. New bone formation was quantified by use of densitometric image analysis, and values for the scintigraphic ratios were compared.

RESULTS

In the distraction and osteotomy groups, delayed-image-to-region-of-interest and delayed-image-to-crural ratios increased significantly. Although densitometric image analysis revealed increased bone formation after distraction, the region-of-interest ratios and crural ratios were similar in both groups. All dogs had increased delayed-image-to-femoral ratios.

CONCLUSIONS AND CLINICAL RELEVANCE

Delayed-image bone scintigraphy ratios were not effective at differentiating between the amounts of distraction-induced bone and osteotomy-induced bone. Metabolic bone activity in the adjacent femur was increased as a consequence of circular external skeletal fixator placement. Delayed-image bone scintigraphy was not adequately sensitive to quantitatively monitor bone formation but may be useful as an early predictor of bone healing.

Maxillofacial intraoral distraction osteogenesis followed by elastic traction in cleft maxillary deformity

We present a case of severe maxillary hypoplasia in a 16 years old cleft patient treated by distraction osteogenesis maxillary advancement. Initial evaluation showed vertical and antero-posterior maxillary deficiencies, and a Class III malocclusion. Two intraoral distractors (Zurich Pediatric Maxillary Distractor, KLS Martin, Tuttlingen, Germany) were placed in a high Le Fort I osteotomy. An initial advancement of 11 mm was obtained, but the resulting occlusion was unsatisfactory (end-to-end occlusion). The consolidation period was reduced to 3 weeks to allow the mechanical manipulation of the newly formed bone with Class III elastics. An additional advancement of 3 mm, caused by elastic orthodontic traction produced both normal skeletal relationship and satisfactory occlusion. This observation shows that it is possible to carry on a skeletal maxillary displacement by interdental elastics before the complete fusion of the callus. After 12 months of postoperative follow-up no osseous relapse could be detected and the occlusal result was stable.

Maxillary distraction resulting in facial advancement at Le Fort III level in cleft lip and palate patients: a report of two cases

An 18-year-old female and a 14-year-old male who had previously received surgery for primary repair of a nonsyndromic cleft lip and palate (including alveolar defect bone grafting) unintentionally developed facial advancement at the Le Fort III level after surgical correction of their maxillary hypoplasia. The Le Fort I osteotomy, originally performed for their maxillary dentoalveolar hypoplasia, was an incomplete osteotomy. It was performed without down-fracture, leaving the pterygomaxillary and septal junctions intact. The gradual advancement of the maxilla during distraction osteogenesis was planned to correct the hypoplastic maxilla, and also prevent subsequent hypernasality; however, during the distraction procedure by means of a rigid external device both patients developed an unintentional facial advancement at the Le Fort III level.

Predicting duration of Ilizarov frame treatment for tibial lengthening

AIM

To predict duration of treatment for tibial lengthening, as a function of target length increase.

METHOD

Review of case notes and radiographs of patients undergoing Ilizarov method of tibial distraction osteogenesis.

RESULTS

In the 27 cases suitable for analysis, the median age was 29.9 years (13.3 to 72.6 years), and the median distraction was 3.5 cm (1.0 to 7.2 cm). A positive linear relationship (r = 0.7) was demonstrated between the distraction length (x, in cm) and the frame duration (y, in days), according to the equation y = 54x + 94. A negative hyperbolic relationship was also demonstrated between rate of bone healing and distraction length (r = 0.6), with distractions over 3.0 cm healing significantly faster than shorter ones (P < 0.03).

Cephalometric analysis of the consolidation phase following bilateral pediatric mandibular distraction

OBJECTIVE

The goal of the consolidation phase of mandible distraction is to maintain the improvement in maxillomandibular form and relationship while the generated tissue ossifies. During this period, external deforming forces can act on the healing generated bone. The purpose of this study was to describe the potential cephalometric changes that occur following pediatric bilateral mandibular distraction using external devices.

DESIGN

Retrospective lateral superimposition cephalometric analyses.

PARTICIPANTS

Thirty-five cases of pediatric mandible distraction were reviewed. Seven of these cases were included in the study after exclusion criteria were applied. These cases represented a group with severe congenital dysmorphology and a mean device activation of 26.5 mm.

MAIN OUTCOME MEASURES

Changes in pogonion position, symphyseal plane rotation, mandible length, and mandible length relative to maxillary length during the 18 to 36 days of activation, the eight weeks of consolidation, and the 1-year period following removal of the distraction device were measured.

RESULTS

All patients demonstrated variable changes in position of the mandible during the consolidation phase. The most common were retrusion of pogonion, a decrease in mandible length, and a clockwise rotation of the symphyseal plane. In some cases the changes that occurred during consolidation were greater than those that occurred on 1-year follow-up.

CONCLUSIONS

The consolidation phase of distraction osteogenesis is a dynamic phase and should not be assumed to be static. Multicenter use of this cephalometric technique would help to identify potential risk factors associated with postactivation changes.