The Study On Exact Reconstruction Of Mandibular Defections With Vascularized Fibula Flap

The mandible constructs the lower 1/3 of the facial structures and plays an influential role in maintaining a natural facial appearance.With the aid of attached muscles and ligaments,complex movements are carried out to achieve substantial functions including swallowing,mastication,respiration,and speech.Mandibular lesions such as benign and malignant tumors,infections,and trauma in the maxillofacial region can often cause mandibular segmental defect(MSD),that is,continuous interruption of the mandible.This will not only cause facial deformation,but also substantially affects the patient's mastication,swallowing,and speech functions,causing psychological burden and mental stress.Mandibular reconstruction maximumly recovers the patient's facial appearance and functions,and can extensively improve the patient's life quality,physical and mental health,assisting them to return to the society.However,this sets a high standard for facial reconstruction surgeons.In current clinical practices,vascularized fibular flap technique is most commonly used to reconstruct mandibular defects.To increase the accuracy of the reconstruction,surgeons often use digital technology including intraoperative navigation and CAD/CAM guide template to modify the straight-lined fibula into the biological curved shape of the mandible.We modified the conventional CAD/CAM guide template to function in both guiding osteotomy and positioning Ti-plate.This experiment consists of two parts:one is a retrospective study on the clinical effects of application of cutting and placing composite template,another is to evaluate the feasibility of the mixed reality technique in mandibular reconstruction with vascularized fibular flap.1.The research on accuracy of mandibular cutting and placing composite template in mandible reconstruction with vascularized fibula flap.Objective:To evaluate the accuracy of mandibular cutting and placing composite template in mandible reconstruction with vascularized fibula flap.Methods:There are 10 patients(7 male to 3 female)with mandible segment defects caused by various reasons,who have received mandibular reconstruction with free vascularized fibular flap from October 2014 to January 2018 at our department were studied retrospectively.Disease classification included 2 mandibular ameloblastomas,2 mandibular myxomas,2 mandibular gingival carcinomas,1 carcinoma of floor of mouth,1 mandibular clear cell carcinoma,1 mandibular ossifying fibroma and 1 secondary-stage reconstructions after tumor resection.Before surgery,all the patients received CTA of bilateral lower extremities and CBCT or thin-layer CT scanning of upper and lower jaw.Using software such as Proplan CMF 3.0 we simulated the excision and the design of reconstruction according to the nature of tumor and the involvement of mandible.The surgical model was made by rapid proto-typing technology.Whilst,we designed and manufacture the mandibular cutting and placing templates to guide the tumor resection,fibular osteotomy and fibular emplacement for patients intraoperatively.All of the patients received Cone Beam CT(CBCT)1 week after surgery.And the data were imported into Geomagic software to analyze the error.Results:All the operative processes went smoothly and whole flaps survived.During the follow-up of 6 months,one patient died of local recurrence and metastasis,the others showed good prognoses.Postoperative CT and 3D error analysis revealed that osteotomy lines and reconstruction contour matched well with preoperative planning.Compared with preoperative positions,the average shift on the total mandible was 1.350mm±0.228mm(largest,6.799mm).Average shift on remaining mandible was 1.37±0.502 mm(largest,1.886 mm).Average shift in the reconstructed mandible was 0.957±0.300 mm,largest being 2.441 mm.Conclusion:According to the fitting result,the accuracy of the mandibular cutting and placing template equals to the navigation technique and conventional template.It could guide positioning Ti-plate.the can improve the accuracy of surgery and obtain good surgical outcomes.We think that it's a simple and useful method.2.The feasibility of the application of mixed reality in mandible reconstruction with vascularized fibula flapPurpose:To study the feasibility of the application of mixed reality in mandible reconstruction with vascularized fibula flap.Method:There are 7 fibulas and 1 mandible bone,which were all received CT examination.Using software such as Proplan CMF 3.0 we made a model of mandibular segmental defects which involves ipsilateral mandible angle and canine.The defect conforms to the classification raised by James Brown.Then we simulated the design of reconstruction by these 7 fibulas.The surgical plans were transferred to HoloLens.We used HoloLens to finish fibular osteotomy and fibular emplacement.After we fixed fibular segments by Ti-template,all of them received CT examination.And the data were imported into Geomagic software to analyze the error.Result:We validate the error of the reconstructive model by Geomagic.We found that 3 groups obtained satisfactory results,the deviation is 0.658±0.075mm,the other 4 groups got large deviations about the contact angle of two fibula segments.Then we import these 4 groups data into Proplan CMF 3.0 to measure these lengths and angles.The average error of length is 2.16±0.62mm.For the reconstructive angle of mandible,the deviation of 2nd and 7th group are 3.6° and 3.9°.The mandibular body of 1st and 5th rotated,so they don't match well.Conclusion:Nowadays,mixed reality provides a possible hands-free approach as get rid of conventional guide template and screen.But HoloLens meet the demand of spatial accurate localization.It can't guarantee the exact mandibular reconstruction with vascularized fibular flap.It needs to be improved.