[Three-dimensional changes in condylar position in skeletal class Ⅲ patients with mandibular deviation after bilateral sagittal split ramus osteotomy].

Objective: To investigage the three-dimensional changes in condylar position after bilateral sagittal split ramus osteotomy (BSSRO) in skeletal class Ⅲpatients with mandibular deviation using cone-beam CT (CBCT). Methods: Twenty-five skeletal class Ⅲ patients with mandibular deviation were included. The patients (12 males and 13 females, aged 19-25 years, average age 22.4 years) were treated in the Department of Orthodontics, Affiliated Stomatological Hospital, Nanchang University from October 2013 to March 2017. The patients were divided into T1, T2 and T3 groups (T1 group: CBCT taken within 1 week before operation; T2 group: CBCT taken within 1 week after operation; T3 group: CBCT taken 6-8 months after surgery). Three sets of image data of condyles on both sides (deviation side and contralateral side) were obtained. After the DICOM data collection, the software of Mimics 17.0 was used to perform three-dimensional reconstruction and condylar position measurements: the distance from the condylar top (CoT) to the standard horizontal plane (SHP), the middle sagittal plane (MSP) and the sella coronal plane (SCP) (CoT-SHP, CoT-MSP, CoT-SCP); the distance from the condylar center (CoC) to SHP, MSP and SCP (CoC-SHP, CoC-MSP, CoC-SCP); the angle from the condyle cella plane (CCP) to SHP, MSP and SCP (CCP-SHP, CCP-MSP, CCP-SCP); the angle from the condyle sagittal plane (CSP) to SHP, MSP and SCP (CSP-SHP, CSP-MSP, CSP-SCP) and the distance of the anterior, superior, posterior, medial, central and lateral joint space. One-way ANOVA and LSD-t test were used to compare the changes in condylar position at different periods (T1, T2, and T3). Results: Within 1 week before operation on the deviation side, CoT-SHP [(2.5±1.3) mm], CSP-MSP (41.2°±8.4°) and the posterior joint space [(2.0±0.6) mm] were obviously increased (P<0.05), and CoT-SCP [(9.1±3.3) mm], CCP-MSP (78.2°±5.2°) were decreased significantly (P<0.05); on the contralateral side, CoT-MSP [(50.4±3.1) mm], CCP-MSP (80.6°±6.0°), the anterior joint space [(2.2±0.6) mm] and the medial joint space [(2.6±0.6) mm] were obviously increased (P<0.05), and CCP-SCP (11.4°±8.8°) were decreased significantly (P<0.05). Six to eight months after surgery, CoT-SHP [(2.2±1.0) mm] and the posterior joint space [(1.9±0.5) mm] on deviation side and CoT-SCP [(8.4±2.8) mm] on the contralateral side were increased significantly (P<0.05). No significant difference was found in other measurements (P>0.05). Conclusions: The condylar position in skeletal class Ⅲ patients with mandibular deviation was asymmetrical. Within 1 week after the operation of BSSRO, the condyle on the deviation side was moved forward, downward and inward. Meanwhile, the condyle on the contralateral side was moved backward and outward. Six to eight months after surgery, the condylar position on both sides was gradually restored to the pre-operative condylar position.目的： 通过锥形束CT分析骨性Ⅲ类错■伴下颌偏斜患者双侧下颌支矢状劈开截骨术（bilateral sagittal split ramus osteotomy，BSSRO）前后髁突位置的三维变化，探讨BSSRO对髁突位置的影响，以期为临床诊断和治疗提供依据。 方法： 选取2013年10月至2017年3月于南昌大学附属口腔医院正畸科就诊的25例骨性Ⅲ类错■伴下颌偏斜患者，其中男性12例，女性13例，年龄19~25岁，平均22.4岁。BSSRO术前1周、术后1周、术后6~8个月分别进行锥形束CT扫描，获取双侧髁突（偏斜侧与偏斜对侧）的影像资料，采用Mimics17.0软件进行三维重建并测量髁突位置相关测量项目：髁突顶点（condylar top，CoT）分别至标准水平面（standard horizontal plane，SHP）、正中矢状面（middle sagittal plane，MSP）、蝶鞍冠状面（sella coronal plane，SCP）的距离（CoT-SHP、CoT-MSP、CoT-SCP），髁突中心点（condylar center，CoC）分别至SHP、MSP、SCP的距离（CoC-SHP、CoC-MSP、CoC-SCP），髁突冠状面（condyle coronal plane，CCP）分别与SHP、MSP、SCP的夹角（CCP-SHP、CCP-MSP、CCP-SCP），髁突矢状面（condyle sagittal plane，CSP）分别与SHP、MSP、SCP的夹角（CSP-SHP、CSP-MSP、CSP-SCP）以及关节前、上、后、内、中、外各间隙。采用单因素方差分析和LSD-t检验比较每侧髁突不同时间点位置变化的差异。 结果： 相比术前1周，术后1周偏斜侧CoT-SHP[（2.5±1.3）mm]、CSP-MSP（41.2°±8.4°）、关节后间隙[（2.0±0.6）mm]显著增大，CoT-SCP[（9.1±3.3）mm]、CCP-MSP（78.2°±5.2°）显著减小（P<0.05）；偏斜对侧CoT-MSP[（50.4±3.1）mm]、CCP-MSP（80.6°±6.0°）、关节前间隙[（2.2±0.6）mm]、关节内间隙[（2.6±0.6）mm]显著增大，CCP-SCP（11.4°±8.8°）显著减小（P<0.05）。术后6~8个月除偏斜侧CoT-SHP[（2.2±1.0）mm]、关节后间隙[（1.9±0.5）mm]以及偏斜对侧CoT-SCP[（8.4±2.8）mm]显著增大外（P<0.05），其余各测量项目与术前的差异均无统计学意义（P>0.05）。 结论： 骨性Ⅲ类错■伴下颌偏斜患者双侧髁突位置不对称。BSSRO术后1周，偏斜侧髁突发生向前下的移动和向内侧的旋转，而偏斜对侧发生向后外的移动和向外侧的旋转。术后6~8个月双侧髁突有逐渐恢复至术前髁突位置的趋势。.