Graduate Institute of Dental and Craniofacial Science, Chang Gung University, Taoyuan, Taiwan.
Assistant Professor, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Taoyuan, Taiwan; Associate Professor, Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan.
J Oral Maxillofac Surg. 2023 Jun;81(6):734-745. doi: 10.1016/j.joms.2023.03.002. Epub 2023 Mar 15.
Patients with facial asymmetry often seek improved symmetry in lower face contour resulting in transverse movement of the proximal segments. The study aimed to investigate the association between transverse change in the proximal segments and postoperative relapse after the surgical correction of skeletal Class III facial asymmetry.
This retrospective cohort study includes consecutive patients with skeletal Class III asymmetry who underwent 2-jaw orthognathic surgery. The primary predictor variable was ramus plane angle (RPA). The patients were grouped as small (S group, <4°) and large (L group, ≥4°) changes in RPA. The primary outcome was the positional change of B point, menton, and the intergonial width. Cone-beam computed tomography images were obtained before surgery (T0), 1 week after surgery (T1), and debond (T2). Intergroup comparison was conducted with independent t test. Correlations between the variables were estimated by Pearson correlation.
The study sample was composed of 60 subjects with 30 subjects in each study group. In the S group, the mean surgical changes of RPA were inward rotated 0.91° bilaterally. In the L group, the mean surgical changes of RPA were inward rotated 4.80° and 0.32° on the deviated and non-deviated side. After surgery, further minor inward adaptation of both sides was noted (<1 mm), and intergonial distance reduced with these changes in the proximal segments. By comparing the postsurgical stability between S and L group, the overall sagittal and vertical stability had no significant difference between 2 groups. However, the postsurgical transverse menton relapse (ΔMe in T2-T1) was significantly larger in L group (0.81 ± 1.40 mm) than S group (0.04 ± 1.32 mm) by 0.77 mm (P = .014).
Greater surgical changes in the proximal segments had minor clinical effect on transverse stability. Minor transverse overcorrection of 1 mm is recommended in cases with severe facial symmetry with extensive changes in the proximal segments.
面部不对称的患者常寻求改善下面部轮廓的对称性，导致近段的横向移动。本研究旨在探讨近段横向变化与骨骼 III 类面部不对称手术矫正后术后复发的关系。
本回顾性队列研究纳入了接受双颌正颌手术的骨骼 III 类不对称连续患者。主要预测变量为下颌支平面角（RPA）。患者分为 RPA 小（S 组，<4°）和大（L 组，≥4°）变化组。主要结局是 B 点、颏点和下颌支间宽度的位置变化。术前（T0）、术后 1 周（T1）和去托槽（T2）时获取锥形束 CT 图像。采用独立 t 检验进行组间比较。采用 Pearson 相关分析估计变量间的相关性。
研究样本由 60 名患者组成，每组 30 名患者。在 S 组中，双侧 RPA 的平均手术变化为向内旋转 0.91°。在 L 组中，RPA 的平均手术变化在偏侧和非偏侧分别为向内旋转 4.80°和 0.32°。术后，双侧进一步观察到较小的向内适应，近端节段的这些变化导致下颌支间距离缩小。通过比较 S 组和 L 组的术后稳定性，两组的总体矢状面和垂直面稳定性无显著差异。然而，L 组（0.81±1.40mm）的术后横向颏部复发（T2-T1 时的ΔMe）明显大于 S 组（0.04±1.32mm），差异为 0.77mm（P=0.014）。
近段较大的手术变化对横向稳定性的临床影响较小。对于近端节段变化广泛且严重面部对称性的患者，建议进行 1mm 的轻度横向过矫正。
