Three-dimensional Cephalometric Study Of Hard Tissue Associated With Le Fort Ⅰ Osteotomy In Digital Orthognathic Surgery

With the widespread use of computed tomography(CT)worldwide,the amount of radiation produced by the new generation of multi-slice spiral CT and cone beam CT has been greatly reduced,and its applications have become more and more widespread.With the development of 3D printing technology,digital cranio-maxillofacial surgery design is becoming more and more popular.The three-dimensional cephalometric analysis is essential for computer-assisted surgery planning in craniofacial surgery,especially in orthognathic surgery.Objective:Explore the three-dimensional cephalometric measurement items that can be used in the digital Le Fort I osteotomy design,and perform preoperative three-dimensional virtual surgery design and postoperative surgical effect evaluation.Method:Nineteen patients(5 males and 14 females)who were diagnosed with jaw deformities in the Stomatological Hospital of Jilin University were selected and received orthognathic surgery in our hospital.All of them underwent digital orthognathic design before surgery and were made by 3D printing. Board.Use Frankfurt Plane,Sagittal Plane and Coronal Plane as the coordinate planes,and the intersection point is the origin of the coordinate to establish a three-dimensional cephalometric coordinate system,and use HP,SP,and CP as the reference planes to determine 23 hard tissues related to Le Fort I osteotomy Marking points and 20 measurement items.Use this three-dimensional cephalometric coordinate system to design related orthognathic surgery,and collect three-dimensional cephalometric data before and after surgery.Use IBM SPSS Statistics 23 for relevant data analysis.Results:ICC shows that 86.25% of the measurement items have high repeatability,10%of the measurement items have acceptable repeatability,and only 3.75% of the measurement items have poor repeatability.HP-U3 R,HP-U6 R,CP-U3 R,CP-U6 L,CP-U6 R,SNA,U1-HP,SP-U6 M,OP-SP and other items before and after operation paired sample t test significance p<0.05,difference has statistical significane.The results on Sagittal Plane show: SP-U3 L,SP-U3 R,SP-U6 L,SP-U6 R,HP-U3 R,HP-U6 L,HP-U6 R,CP-U3 R,CP-U6 L,CP-U6 R,U1-HP,SP-U3 M,SP-U6 M,U1-SP,OP-SP paired sample t-test before and after operation was significant p<0.05,and the difference was statistically significant.Independent sample t-test to compare the differences between the sexes showed: SP-U3 L,SP-U6 L,SP-U6 R,HP-U3 L,HP-U3 R,HP-U6 L,HP-U6 R,CP-U3 L,CP-U3 R,CP-U6 L,CP-U6 R,U1-HP and other measurement items have statistically significant differences between men and women(p<0.05).Conclusions:1.This study shows that the three-dimensional coordinate system established by Frankfurt Plane,Sagittal Plane and Coronal Plane,as well as the three-dimensional cephalometric items related to the Le Fort I osteotomy based on the HP,SP,and CP reference planes have a high Repeatability.2.The three-dimensional cephalometric measurement items under the three-dimensional cephalometric measurement system established in this study can be used to assist in the digital Le Fort I type osteotomy three-dimensional virtual surgery design and postoperative surgical effect evaluation.