An Evaluative Research Of The Temporomandibular Joint Function In The Early Stage After The Digital Surgical Guide Assisted Mandibular Tumor Resection And Defect Reconstruction

Objective:To evaluate the structure and function of the temporomandibular joint in the early stage after digital surgical guide assisted mandibular tumor resection and defect reconstruction,and compared with that of rapid prototyping model assisted operation.Methods:20 patients who underwent computer-assisted surgery of mandibular tumors resection and simultaneous segmental defect reconstruction in our department from January 2015 to October 2020 were involved in this study.All patients were grouped according to the computer-assisted technology used for surgery.Those who using virtual surgical planning and surgical guide technology were assigned to the guide group(n=9),and those who using rapid prototyping technology to print 3D models for preoperative reference were assigned to the control group(n=11).Intraoperative operating time was recorded and compared between thetest and control groups;The temporomandibular joint cavity gap,the position of the condyle in the articular fossa,the intersection angle of the condyle long axis extension line,the position deviation at the epipolar point of the condyle and the apex of the condyle were measured by threedimensional CT scan of the mandible in both groups;The trend of changes in the angle between the posterior band of the temporomandibular joint disc and the apex of the condyle and in the mandibular function of patients in the guide plate group were analyzed by the temporomandibular joint questionnaire and temporomandibular joint magnetic resonance before and 2 weeks,1 month,and 6 months after surgery.The measured data were statistically processed using SPSS 22.0 software,and differences were considered statistically significant at p < 0.05.Results :(1)The operating time was significantly lower(p < 0.05)in the guide group than in the control group.(2)The changes in the joint space between the healthy side and the affected side of the patients in the guide group before and after surgery were not statistically significant(p > 0.05);The changes in the sagittal and coronal supra-articular spaces of the affected joint before and after surgery were statistically significant in the control group(p <0.05),while the changes on the healthy side were not significant(p > 0.05).None of the preoperative measurements in the guide and control groups were statistically different(p > 0.05);The changes in the position of the condylar process in the articular fossa and the changes in the intersection angle of the long axis of the condylar process were not statistically different between the two groups after surgery(p > 0.05);However,the deviation values at the apex of the condyle on the affected side were statistically significant(p < 0.05).(3)In the guide group,no statistically significant changes in the angle between the disc and the condylar apex in the open and closed positions were observed during the preoperative and postoperative follow-ups(p > 0.05);2 weeks after surgery,2 patients had symptoms of joint popping and 1 patient had discomfort of pressure pain in the joint area;6 months after surgery,all patients had no symptoms of joint disorders except for one patient who had pressure pain in the joint area;The mandibular motor functions such as mouth opening,lateral and anterior extension motility decreased to different degrees after surgery,and these functions were found to recover gradually during the follow-up,and these functions had returned to near preoperative levels at 6 months postoperatively.Conclusion:(1)Compared with the RP model-assisted technology,the digital guide technology shortens the operation time and better maintains the stability of the condylar process in three dimensions,provides an important structural basis for the preservation and restoration of postoperative mandibular function.(2)After the mandibular reconstruction assisted by digital guide technology,the mandibular mobility(mouth opening,lateralization,and anterior extension)decreased significantly in the short term and could be gradually recovered in the later stage,and was close to the preoperative level by 6 months after the operation.The affected joint disc tended to shift slightly forward after surgery,but the changes were not statistically different and were not accompanied by significant clinical symptoms.In the postoperative period,the position of the articular disc can gradually approach the preoperative level,maintaining a stable disc-condyle relationship,which is very beneficial to the recovery of mandibular function.