Mandibular distraction osteogenesis: types, applications, and indications

Three-dimensional preoperative design of distraction osteogenesis for hemifacial microsomia

The purpose of this research was to simulate mandibular movement calculated from three-dimensional computed tomography (CT) data to determine the linear distractor position to correct mandibular deformities in a series of patients with hemifacial microsomia (HFM). Preoperative CT scans from 6 HFM patients were obtained and imported into a CT-based software program (Mimics) to produce three-dimensional images and data. After measurement of the mandibular deficiency in 3 dimensions (horizontal and vertical), the angle between the distraction device and the ramus was determined by a geometric calculation, and then the surgery was performed on the three-dimensional model constructed using the rapid prototyping technique. This planning method was finally used in the treatment of 6 HFM patients. The HFM was corrected, and a symmetrical facial contour obtained without any complications in these 6 patients. The results matched the expectation before surgery that the distractor elongation would range from 18 to 22 mm. The distraction tracing model fitted the actual postdistraction tracing to within 2 mm. The preoperative design and three-dimensional modeling technique are considered to be helpful in enhancing the predictability and improving the outcome of the treatment of distraction osteogenesis.

Rapid prototyping-assisted maxillofacial reconstruction

Rapid prototyping (RP) technologies have found many uses in dentistry, and especially oral and maxillofacial surgery, due to its ability to promote product development while at the same time reducing cost and depositing a part of any degree of complexity theoretically. This paper provides an overview of RP technologies for maxillofacial reconstruction covering both fundamentals and applications of the technologies. Key fundamentals of RP technologies involving the history, characteristics, and principles are reviewed. A number of RP applications to the main fields of oral and maxillofacial surgery, including restoration of maxillofacial deformities and defects, reduction of functional bone tissues, correction of dento-maxillofacial deformities, and fabrication of maxillofacial prostheses, are discussed. The most remarkable challenges for development of RP-assisted maxillofacial surgery and promising solutions are also elaborated.

Closure of the alveolar cleft by bone segment transport using an intraoral tooth-borne custom-made distraction device

PURPOSE

The fact that bone transportation generates not only bone but also surrounding soft tissues makes it an ideal technique for tissue regeneration. This study evaluates bone segment transport using an intraoral tooth-borne distraction device for alveolar cleft closure.

MATERIALS AND METHODS

Patients with an alveolar cleft were enrolled in the study. They were treated at the Al-Azhar University Hospital, Cairo, Egypt, between 2004 and 2007. Anterior transportation of the posterior dentoalveolar segment was performed by use of an intraoral tooth-borne custom-made distractor. Clinical evaluations included the following: preoperative and postoperative intraoral photographs, vitality testing of the teeth in the transport segment, cast analysis, and measurement of tooth mobility. Radiographic evaluations included occlusal films, orthopantomography, and computed tomography and 3D computed tomography for volumetric and densitometric evaluations of the distracted bone.

RESULTS

After distraction was completed, the transported segments were positioned 1 to 4 mm superior to the occlusal plane. The radiographic evaluation showed residual triangular bone deficits that were closed through gingivoperiosteoplasty or bone grafting. Once the transported segments came in contact with the alveolar bone of the normal side, the intervening fibrous tissue at the docking site was removed, and docking-site surgery was then performed. The results obtained from both clinical examinations and radiographic imaging showed complete closure of the alveolar clefts.

CONCLUSIONS

Maxillary alveolar bone transport offers an alternative technique in the latest treatment of the alveolar cleft.

Anterior segmental distraction of the hypoplastic maxilla by a tooth borne device: a study on the movement of the segment

The aim of this study is to determine the relative movement of the teeth and bone after premaxillary distraction with a tooth-borne device constructed in the authors' centre. To evaluate the effects of this device on the anterior segment and teeth, the space formed between the anterior and posterior segments of the maxilla was measured on computerized tomography images from 10 patients. The average differences were 3.5mm at the apex level, 5.5 mm at alveolar ridge level and 7.4 mm at crown level on the right side. On the left side, the average differences were 3.2, 5.2 and 7.1 mm, respectively. There were statistically significant differences between all these measurements (p<0.05), but the difference between right and left sides was not statistically significant (p>0.05). The ratio between the movements at apex and crown levels was 46%. These results showed that the tooth-borne distractor was able to distract the anterior segment of the maxilla but it also caused anchorage loss of the maxillary incisors.

Experimental application of a biomaterial in bifocal transport osteogenesis for craniofacial reconstruction

PURPOSE

Bifocal transport osteogenesis is an alternative technique of callus distraction, in which movement of a transport segment results in the formation of new bone in order to close a continuity defect. The aim of this experimental pilot study was to replace a bone graft by a biomaterial as a transport segment.

MATERIAL AND METHODS

Critical size defects of the calvaria in four adult sheep were treated with transport segments consisting either of an autogenous free bone graft of the calvaria (n=2) or of the biomaterial (deproteinized bovine cancellous bone; n=2). Latency period was 5 days; the rate of distraction was 1mm per day and was planned for 40 days. The consolidation period was 28 days. Specimens were investigated by conventional radiography, CT-scans and histologically, including immunofluorescence.

RESULTS

In both groups, transport osteogenesis resulted in a "de novo" formation of bone, indicating that this biomaterial may contribute successfully to bone formation in bifocal transport osteogenesis. However, volume and thickness of the newly formed bone at the defect site were smaller when using the biomaterial than when using autogenous bone grafts.

CONCLUSION

The application of a biomaterial as transport segments in bifocal transport osteogenesis in cranial critical size defects resulted in the formation of new bone thus excluding bone graft donor site morbidity.

Condyle as the point of rotation for 3-D planning of distraction osteogenesis for hemifacial microsomia

AIM

The purpose of this study is to present an exact simulation method for mandibular rotational movement in distraction osteogenesis for hemifacial microsomia.

METHODS

Three-dimensional (3-D) surgery simulation software programmes (V-Works and V-Surgery; Cybermed, Seoul, Korea) were used, based on 3-D CT data in addition to the conventional data, which included facial photography, panoramic radiograph, cephalogram, and dental models. After measuring the mandibular deficiency (horizontal and vertical) from a 3-D model reconstructed using the software, the angulation of the distraction device to the mandibular border (posterior or inferior) was determined. The rotation axis in the V-Works simulation was defined as the line perpendicular to the plane made by condylion and the distraction vector location on the mandible. The mandible moves along the plane around this rotational axis during distraction. After the 3-D simulation with the software programme, mock surgery on a rapid prototyping model was performed. This planning method was applied to models of two hemifacial microsomia patients.

RESULTS

With this protocol, it was possible to simulate the rotational movement of the mandible on the axis passing through the condylar head of the unaffected side.

CONCLUSION

The sequential planning procedure presented in this paper is considered to be helpful in performing effective preoperative simulation of distraction osteogenesis for hemifacial microsomia.

Ortho- and heterotopic bone grafts in bifocal transport osteogenesis for craniofacial reconstruction--an experimental study in sheep

Bifocal transport osteogenesis (BTO) is a promising technique for the reconstruction of extended osseous craniofacial defects. Aim of this study was to determine the potential of this technique related to various donor sites of the transport segment. In 10 adult sheep critical size defects of the calvaria were treated by gradual movement of a transport segment consisting either of autogenous regional free calvarial bone grafts (n=5) or autogenous illiac free bone grafts (n=5). Latency period was 5 days; the rate of distraction was 1mm per day and extended approximately 40 days. The consolidation period was 28 days. After harvesting, specimens were investigated by conventional radiography, CT-scans, histologically and by fluorescence. In both groups transport osteogenesis resulted in a complete closure of the critical size defect. Membranous bone formation and remodeling occurred during the entire period of distraction and consolidation. The volumes and thickness of newly formed bone at the defect site were increased significantly when calvarial bone grafts were used (P<0.05). Iliac bone grafts became progrediently smaller during distraction, while the volume of calvarial grafts remained relatively constant (P<0.05). In conclusion, transport segments consisting of calvarial and iliac bone resulted in a reliable closure of craniofacial critical size defects in adult organisms; the application of calvarial bone grafts resulted in an increased extend of bone formation.

Craniofacial reconstruction by transport distraction osteogenesis: corticotomy versus osteotomy--an experimental study

Transport osteogenesis is a modified technique of callus distraction appropriate for the reconstruction of extended osseous defects of long or flat bones. The aim of this study was to determine the regenerative potential of this technique related to the degree of mobilization of the transport segment. In 10 adult sheep, critically sized defects of the calvaria were treated by gradual movement of a transport segment consisting of calvarial bone. The transport segments were either corticotomized (n = 5) or osteotomized (n = 5). The latency period was 5 days; the rate of distraction was 1 mm/d, extended for approximately 40 days. The consolidation period was 28 days. Specimens were investigated by conventional radiography, computed tomography scans, immunofluorescence, and histological examination. In both groups, transport osteogenesis resulted in a complete closure of the defect. The volume and thickness of newly formed bone at the defect site did not differ significantly between the groups, nor did the extent of vascularization. Bone formation and remodeling occurred during the entire period of distraction and consolidation. Osteotomized transport segments became smaller during distraction, whereas the volume of corticotomized segments remained relatively constant. In conclusion, transport osteogenesis resulted in reliable closure of extended skull defects in adult organisms; corticotomy and osteotomy of the transport segment led to a similar extent of bone formation.