Double-step transport distraction osteogenesis in the reconstruction of unilateral large mandibular defects after tumour resection using internal distraction devices

Creation of Bone and Soft Tissue in Postmaxillectomy Patients Using Curvilinear Transport Distraction Osteogenesis

BACKGROUND

Large surgical defects in the maxilla due to trauma or tumor are usually reconstructed with revascularized-free fibula flaps (RFFF). In the past, the use of curvilinear transport distraction osteogenesis (CTDO) has been shown to be an efficacious way in closing large defects in the maxilla, but it had limitations which have now been overcome by the present development. The present distractor is an improvement upon the previous three prototypes and employs the concept of tetrafocal distraction by means of hybridizing the bone with the tooth in the transport disc segment. This article aims to prove that tetrafocal distraction provides a viable alternative to the RFFF.

MATERIALS AND METHOD

In a prospective cohort study of six postmaxillectomy patients, the method of CTDO was applied and investigated to ascertain the outcome. The regenerate bone was compared with the parent bone, using a new maxillary transport distractor. A linear bicortical fracture was created in the maxilla in a vertical direction (segmentally) to develop a mobile, vascularized transport disk. This transport disk underwent further subdivision to produce the concept of tetrafocal distraction.

RESULTS

After osseointegration of the dental implants, prosthetic rehabilitation of the dentition was successful. The authors report the successful outcome of two of the six cases subjected to CTDO to treat defects ranging from 25 mm (using bifocal distraction) to 80 mm along a curved trajectory (using tetrafocal distraction).

CONCLUSIONS

The production of curvilinear bone and soft tissue along a horizontal plane has been demonstrated. From a clinical perspective, the new alveolar bone achieved the correct width and height to create a physiological vestibule and an esthetic zone for dental implants. In addition, the shape of the palatal vault is also reconstituted. The tetrafocal method of the CTDO is a reliable method of maxillary reconstruction.

Guidelines for the Surgical Management of Oral Cancer: Korean Society of Thyroid-Head and Neck Surgery

Korean Society of Thyroid-Head and Neck Surgery appointed a Task Force to provide guidance on the implementation of a surgical treatment of oral cancer. MEDLINE databases were searched for articles on subjects related to “surgical management of oral cancer” published in English. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. The quality of evidence was rated with use RoBANS (Risk of Bias Assessment Tool for Nonrandomized Studies) and AMSTAR (A Measurement Tool to Assess the Methodological Quality of Systematic Reviews). Evidence-based recommendations for practice were ranked according to the American College of Physicians grading system. Additional directives are provided as expert opinions and Delphi questionnaire when insufficient evidence existed. The Committee developed 68 evidence-based recommendations in 34 categories intended to assist clinicians and patients and counselors, and health policy-makers. Proper surgical treatment selection for oral cancer, which is directed by patient- and subsite-specific factors, remains the greatest predictor of successful treatment outcomes. These guidelines are intended for use in conjunction with the individual patient’s treatment goals.

Repair of segmental bone defects in the maxilla by transport disc distraction osteogenesis: Clinical experience with a new device

The bones of the maxillary complex are vital for normal oro-nasal function and facial cosmetics. Maxillary tumor excision results in large defects that commonly include segments of the alveolar and palatine processes, compromising eating, speech and facial appearance. Unlike the conventional approach to maxillary defect repair by vascularized bone grafting, transport disc distraction osteogenesis (TDDO) stimulates new bone by separating the healing callus, and stimulates growth of surrounding soft tissues as well. Bone formed in this way closely mimics the parent bone in form and internal structure, producing a superior anatomical, functional and cosmetic result. Historically, TDDO has been successfully used to close small horizontal cleft defects in the maxilla, not exceeding 25 mm. Fujioka et al. reported in 2012 that "no bone transporter corresponding to the (large) size of the oro-antral fistula is marketed. The authors report the successful treatment of 4 cases involving alveolar defects of between 25 mm and 80 mm in length.

Experience with mandibular reconstruction using transport-disc-distraction osteogenesis

The goal of transport-disc-distraction osteogenesis (TDDO) is to restore bone continuity by using in-situ bone. It may be useful following trauma, gunshot injuries, or tumor ablation, especially when there may be contraindications at the donor site or for prolonged surgery. To the best of the authors' knowledge, this is the first time TDDO has been used for mandibular reconstruction reporting additional procedures, which include osseointegrated dental implants rehabilitation and orthognathic surgery. A retrospective study is performed analyzing all mandibular reconstruction cases that may be suitable for distraction from January 2006 to December 2011. A thorough description of the documented cases includes details about sex, gender, complications, duration of hospitalization, etiology, size, and location of the defect. Eight cases of mandibular reconstruction were included. Six cases correspond to mandibular ameloblastoma. The remaining two cases were mandibular gunshot comminuted fractures. Range of the defects was from 45 to 60 mm. Length of the transport disc was 15 to 20 mm. Protocolized technique consisted of 5 days of latency period, 19 to 45 days of activation term (average 30 days), and 8 to 12 weeks for consolidation. Mean distraction length achieved was 40.45 mm. We can conclude that TDDO is an alternative to conventional and more invasive procedures, when we face severe segmental mandibular defects reconstruction. It shows the potential to restore a better anatomical bone regeneration, also providing soft tissues and reducing donor-site morbidity. Patients' education and awareness about the proper use of the transport-disc-distraction device is important to optimize functional outcomes.

Biomechanics of the canine mandible during bone transport distraction osteogenesis

This study compared biomechanical patterns between finite element models (FEMs) and a fresh dog mandible tested under molar and incisal physiological loads in order to clarify the effect of the bone transport distraction osteogenesis (BTDO) surgical process. Three FEMs of dog mandibles were built in order to evaluate the effects of BTDO. The first model evaluated the mandibular response under two physiological loads resembling bite processes. In the second model, a 5.0 cm bone defect was bridged with a bone transport reconstruction plate (BTRP). In the third model, new regenerated bony tissue was incorporated within the defect to mimic the surgical process without the presence of the device. Complementarily, a mandible of a male American foxhound dog was mechanically tested in the laboratory both in the presence and absence of a BTRP, and mechanical responses were measured by attaching rosettes to the bone surface of the mandible to validate the FEM predictions. The relationship between real and predicted values indicates that the stress patterns calculated using FEM are a valid predictor of the biomechanics of the BTDO procedures. The present study provides an interesting correlation between the stiffness of the device and the biomechanical response of the mandible affected for bone transport.

Biomechanical analysis of a curvilinear distractor device for correcting mandibular symphyseal defects

PURPOSE

The local mechanical environment is a determinant of successful transport disc distraction osteogenesis. This study assessed the biomechanics of a curvilinear distractor device for correcting mandibular symphyseal defects.

MATERIALS AND METHODS

The finite element method was used to analyze an intact mandible, mandibular distractor bodies with different rail thicknesses (4, 6, 8, and 10 mm), and mandibular distractor bodies with rails and auxiliary lingual brackets.

RESULTS

Rail thickness was positively correlated with maximum von Mises stress in the distractor and negatively correlated with maximum displacement of the mandibular distractor bodies. The maximum von Mises stress occurred at the junction of the rails and fixed arms. It also exceeded the yield strength of the titanium material. Compared with the maximum displacement of the intact mandible, that of the mandibular distractor bodies was visibly increased.

CONCLUSION

An auxiliary lingual bracket can effectively decrease stress in such devices and displacement of mandibular distractor bodies. Rail fixation alone cannot achieve stability for distraction osteogenesis. Using an auxiliary lingual bracket effectively prevents distractor breakage and exposure.