A Comparative Study On The Assessment Of Mandibular Position In General Anesthesia And Awake Supine Position Based On CT Images

Purpose: The purpose of this study is to use the preoperative-intraoperative imaging data of patients to perform three-dimensional reconstruction through Materialize Pro Plan CMF3.0.1 software,to reflect the position changes of the mandible relative to the maxilla and skull base in adults under general anesthesia(supine position),and to enrich the data in different states.The research on the position of the mandible provides some guidance for the positioning of the mandible and condyle in the clinic.Methods: The clinical data of adult patients with complete preoperative and intraoperative craniomaxillofacial CT were collected from October 2020 to January2023 who visited the Department of Maxillofacial Surgery at the 940 th Hospital of the People’s Liberation Army Joint Security Force,and the patients had complete preoperative and intraoperative craniomaxillofacial CT data,14 patients(10 males and4 females)were selected,aged 19-52 years,with an average of 29.4 years.Study 1:Each patient’s preoperative and intraoperative spiral CT was taken in a uniform standard position,and 3D reconstruction was performed using Materialise Pro Plan CMF3.0.1software,with the skull base and maxilla as the reference for overlap,to compare and observe the preoperative-intraoperative mandibular position changes,and then anatomical marker points were selected for matching with the skull base and maxilla as the reference for offset in millimeters After the threshold was set,the displacement changes of the mandible were shown in different colors on the overlapping model with different offset amounts.Study 2: The anatomical marker points were selected in the mandible using the overlapping 3D model,and the 3D coordinate system of the 3D model was generated in the software system to calculate the movement of each anatomical marker point of the mandible in the X(left and right),Y(anterior and posterior)and Z(superior and inferior)directions of the spatial coordinate system during the preoperative-intraoperative period,and the anatomical positioning of each anatomical marker point before and after the state of general anesthesia was calculated based on the obtained preoperative-intraoperative displacement distance(unit: mm)The data obtained were statistically analyzed using SPSS21.0 software,and the results were expressed as mean ± standard deviation(X ± S)for data conforming to normal distribution and statistically analyzed using one-sample t-test;for data not conforming to normal distribution,median,25% quantile and 75% quantile were expressed using one-sample Wilcoxon signed rank test Statistical analysis was performed.Statistical results P < 0.01 indicate statistically significant differences.Results:1.14 patients showed different degrees of displacement of the mandible intraoperatively,basically all of them showed clockwise rotation,and the maximum range of movement of the chin and the posterior margin of the mandibular ascending branch exceeded 10 mm,and the degree of displacement of the mandibular body part was about 4-8 mm;7 of them showed deflection of the mandible in the internal and external directions.2.The points representing the proximal bone segment(Comed,Conlat,Cor,Sim,Lin,Go),the condylar ectopolar point Conlat had a horizontal displacement of 0.3±1.6(to the left),a sagittal displacement of 0.1±1.6(backward),and a vertical displacement of-0.1±1.2(downward);the condylar endopolar point Conmed had a horizontal displacement of 0.8±1.6(to the left),a sagittal displacement of 0.4±1.7(backward),and a vertical displacement was-0.4±2.7(downward),suggesting a small change in displacement of the poles inside and outside the condyle in the left-right,updown,and anterior-posterior directions.Cor.X,Y,Z(0.5±1.3,0.41±1.8,-1.9±1.5);Sim.X,Y,Z(0.7±0.9,0.8±1.7,-0.7±1.3);Lin.X,Y,Z(0.6± 1.1,2.1±2.1,-0.7±1.7);Go.X,Y,Z(1.1±1.2,3.4±3.5,0.8±2.3).The points representing the distal bone segment(B,Me,Pog,Gn,Mf)also showed displacement to the left,downward,and backward,and the degree of displacement in each direction was significantly greater than that of the points of the proximal bone segment,where the Go point of the proximal bone segment was 0.8±2.3(upward)in the vertical direction,unlike the displacement direction of the remaining proximal bone segment markers,suggesting a clockwise rotation of the mandible on the axis of the inner and outer poles of the condyle.The displacement of the condylar internal and external poles in the left-right,anteriorposterior,and superior-inferior directions was not significantly different under intraoperative anesthesia,and the points of the distal bone segment(B,Me,Pog,Gn,and Mf)had significant differences in the anterior-posterior,superior-inferior,and superior-inferior directions.Conclusions: 1.This study analyzed the displacement of the mandible relative to the skull base and maxilla in the preoperative and intraoperative general anesthesia state(supine position)based on the three-dimensional reconstruction of the craniomaxillofacial region by preoperative and intraoperative spiral CT,and the measurements were highly accurate and reproducible,which enriched the clinical method for evaluating the relative position of bone tissues.2.Under intraoperative general anesthesia(supine position),the changes in the mandible caused by the change of body position showed that the mandible as a whole was displaced in the posterior,inferior and left directions,and there was no significant difference in the displacement of the condylar position in each direction,and the mandible made a small clockwise jaw opening movement during intraoperative general anesthesia,and the condyle only made a small rotation without sliding.This study investigated the changes in the position of the mandible and condyle under general anesthesia(supine position)to enrich the study on the position of the mandible and provide some guidance for the positioning of the mandible and condyle in the clinic.