Three-Dimensional Evaluation Of Postoperative Maxillary Stability For Orthognathic Surgery In Patients With Maxillary Vertical Dysplasia

Objective:To establish a three-dimensional measurement method applicable for the patients with vertical maxillary hypoplasia based on three-dimensional CT,and to make evaluation on the stability of upper maxillary bones of patients with maxillary hypoplasia after LeFort I osteotomy as well as the influence factors.Method:1.According to the enroll criteria,60 patients of upper maxilla vertical hypoplasia were selected and their full skull spiral CT data separately 2 weeks before orthognathic surgery(T0),4 days after orthognathic surgery(T1),3 months after orthognathic surgery(T2)were collected.ProPlan CMF was adopted to reconstruct and measure the patient's full skull CT data at different time points,and 9 indicators(ANS-CP,GPL-CP,GPR-CP,ANS-SP,GPL-SP,GPR-SP,ANS-HP,GPL-HP,GPR-HP)reflecting the upper maxilla characteristics were recorded.Then,SPSS22.0 statistical software was used to conduct paired T test for all upper maxilla data during the follow-up time slot in order to evaluate the short-term three-dimensional stability after orthognathic surgery.2.Patients' skull CT data at T0,T1,T2 and T3 were selected and 3-Matic software was adopted to establish the three-dimensional measurement method for upper maxilla and verify the fixed-point repeatability;in total 9 measurements(ANS-X,GPL-X,GPR-X,ANS-Y,GPL-Y,GPR-Y,ANS-Z,GPL-Z,GPR-Z)describing the spatial location of upper maxilla were recorded and analyzed;SPSS22.0 statistical software was used to make t test and multi-factor regressive analysis upon the measurements separately at period of T0,T1 and T2,so as to identify the significant influence factors on its stability.The significant influence factors were collected and ROC analysis was carried out forevaluating the short-term three-dimensional stability of maxilla after orthognathic surgery as well as risk factors.Results:Through three-dimensional CT measurement analysis,the result shows that,60 patients with vertical upper maxilla hypoplasia had obvious recurrence in 6 months after orthognathic surgery;from the moment after surgery to 6 months after surgery,the upper maxilla phenomenon occurred again,with the anterior maxillary segment 1.11 mm upward;while upper maxilla bones did not have recurrence in sagittal and horizontal directions;The recurrence in vertical direction is proved to be significantly related to the descending distance during orthognathic surgery and whether the posterior part of maxilla was descending or not during orthognathic surgery.Besides,when the descending distance during surgery is above 2.78 mm,there will be obvious recurrence in vertical direction.Conclusions:1.The upper maxilla of patients with maxillary hypoplasia after orthognathic surgery has a certain chance for recurrence in vertical direction.2.The vertical stability of upper maxilla after surgery has correlation to the moving distance and moving method in vertical direction during orthognathic surgery.3.The three-dimensional measurement method used in this test can relatively reflect the recurrence tendency of maxilla for patients with maxillary hypoplasia in terms of spatial position after orthognathic surgery effectively.When compared to the traditional three-dimensional measurement method,it can be more comprehensive and also provide reference to researches on the upper maxilla stability after orthognathic surgery.