Yan Shunchao, Qiao Chongxu, Miao Junyan, Shi Zai, Xu Jingyi, Yan Kaili, Qu Yuming, Wu Guoping
Department of Plastic Surgery, The Affiliated Friendship Plastic Surgery Hospital of Nanjing Medical University, Nanjing, Jiangsu province, 210029, China.
Department of Plastic Surgery, The Affiliated Friendship Plastic Surgery Hospital of Nanjing Medical University, Nanjing, Jiangsu province, 210029, China.
J Craniomaxillofac Surg. 2025 Sep;53(9):1563-1570. doi: 10.1016/j.jcms.2025.06.010. Epub 2025 Jul 2.
The remodeling process of asymmetrically prognathic mandibles following bilateral sagittal split ramus osteotomy (BSSRO) remains incompletely understood. This study investigates the sequential changes in mandibular symmetry after BSSRO. A retrospective analysis was conducted on 60 consecutive patients with asymmetric prognathism who underwent BSSRO between January 2018 to December 2023. CBCT scans were obtained at three different time points: preoperatively (T0, within 2 weeks before surgery), immediately postoperatively (T1, within 2 days) and long-term postoperatively (T2, at least 6 months later). Mandibular symmetry was quantified using root mean square error (RMSE), derived from spatial discrepancies between the right-deviated mandibles and its mirrored counterpart. Additionally, positional discrepancies of 12 landmark points and volumetric differences of 6 mandibular segments were assessed using paired t-test. At T0, the mean RMSE was 2.729, which significantly decreased to 2.163 immediately after BSSRO (p < 0.0001), and further to 1.916 at T2 (p < 0.001). During T0-T1, significant corrections were observed in X-directional discrepancies in CoG-C, MF and CoG-B. However, BSSRO increased Y-directional discrepancies in Go and Cd, as well as Z-directional discrepancies in CoG-R, while volumetric asymmetry expanded in three mandibular segments (C: p = 0.002; B: p = 0.003; R: p < 0.001). During T1-T2, significant reductions occurred in X- and Z-directional discrepancies of Go and Z-directional discrepancies of CoG-R, with resolution of volumetric asymmetry in the mandibular body (p = 0.001) and ramus (p < 0.001). Mandibular symmetry improvement after BSSRO occurs in two distinct stages. The first stage is primarily due to surgical repositioning of the deviated distal segment, while the second stage involves orthodontic treatment and bony remodeling of the morphologically asymmetric proximal segments.
双侧矢状劈开下颌支截骨术（BSSRO）后不对称前突下颌骨的重塑过程仍未完全明确。本研究调查了BSSRO后下颌骨对称性的连续变化。对2018年1月至2023年12月期间连续60例行BSSRO的不对称前突患者进行了回顾性分析。在三个不同时间点获取CBCT扫描：术前（T0，手术前2周内）、术后即刻（T1，术后2天内）和术后长期（T2，至少6个月后）。使用均方根误差（RMSE）对下颌骨对称性进行量化，RMSE源自右偏下颌骨与其镜像对应物之间的空间差异。此外，使用配对t检验评估12个地标点的位置差异和6个下颌骨节段的体积差异。在T0时，平均RMSE为2.729，BSSRO后立即显著降至2.163（p < 0.0001），在T2时进一步降至1.916（p < 0.001）。在T0 - T1期间，观察到CoG - C、MF和CoG - B在X方向差异上有显著矫正。然而，BSSRO增加了Go和Cd在Y方向的差异，以及CoG - R在Z方向的差异，同时三个下颌骨节段的体积不对称性扩大（C：p = 0.002；B：p = 0.003；R：p < 0.001）。在T1 - T2期间，Go在X和Z方向的差异以及CoG - R在Z方向的差异显著减小，下颌体（p = 0.001）和下颌支（p < 0.001）的体积不对称性得到解决。BSSRO后下颌骨对称性改善分为两个不同阶段。第一阶段主要是由于偏斜远心段的手术重新定位，而第二阶段涉及正畸治疗和形态不对称近心段的骨重塑。
