Zachariah Thomas, Bharathi Rajkumar, Ramanathan Manikandhan, Parameswaran Anantanarayanan
Department of Oral and Maxillofacial Surgery, Meenakshi Ammal Dental College and General Hospital, Meenakshi Academy of Higher Education and Research (Deemed To Be University), Alapakkam Main Road, Maduravoyal, Chennai, Tamil Nadu 600095 India.
J Maxillofac Oral Surg. 2021 Sep;20(3):432-438. doi: 10.1007/s12663-021-01564-7. Epub 2021 Apr 19.
Condylar displacement after bilateral sagittal-split osteotomy (BSSO) occur in the sagittal plane as clockwise/counter-clockwise rotation of the ramus, in the coronal plane as medial/lateral inclination, or in the axial plane as medial/lateral condylar torquing. The purpose of this prospective CT study was to evaluate the role of plate fixation in minimizing condylar torquing or rotational changes in the axial plane.
This prospective study was carried out on 26 patients, 13 of whom underwent advancement BSSO and 13 setback BSSO, without maxillary LeFort I osteotomies. All mandibular movements were symmetrical. Fixation of the osteotomized segments was achieved with a single 4-hole plate and monocortical screws. In case of mandibular setbacks, a straight plate was used, whereas an inset-bent plate was used for advancements. Computed tomography scans were obtained preoperatively and postoperatively to measure condylar rotation or torqueing in the axial plane. An increase in condylar angle on axial slices was considered as lateral condylar torquing, whereas a decrease was considered as medial condylar torquing.
A mean medial condylar torquing of 0.2° was noted postoperatively in case of setbacks ( > 0.05 not significant). This suggested minimal condylar torquing, indicating that the proximal and distal segments maintained contact at the anterior vertical osteotomy fixed with a straight plate. In case of advancements, a mean lateral condylar torquing of 2.2° was noted postoperatively ( < 0.005, highly significant). This suggested that the proximal segment flare at the anterior vertical osteotomy site was maintained by inset-bent plate fixation.
The gaps between the proximal and distal segments created by mandibular advancement and setback should be maintained. An attempt to close these gaps, especially in mandibular advancement, will result in an unfavourable axial condylar torque. Consequently, the areas of bony contact between the proximal and distal osteotomy sites created by mandibular advancement and setback should be maintained as well.
双侧矢状劈开截骨术（BSSO）后髁突移位发生在矢状面，表现为升支的顺时针/逆时针旋转；发生在冠状面，表现为内侧/外侧倾斜；发生在轴面，表现为内侧/外侧髁突扭转。这项前瞻性CT研究的目的是评估钢板固定在最小化髁突扭转或轴面旋转变化中的作用。
本前瞻性研究对26例患者进行，其中13例行前徙BSSO，13例行后退BSSO，均未行上颌LeFort I截骨术。所有下颌运动均对称。截骨段用一块4孔钢板和单皮质螺钉固定。下颌后退时，使用直板；前徙时，使用内嵌弯曲钢板。术前和术后进行计算机断层扫描，以测量轴面的髁突旋转或扭转。轴位片上髁突角增加被视为外侧髁突扭转，减少被视为内侧髁突扭转。
后退病例术后平均内侧髁突扭转0.2°（>0.05，无统计学意义）。这表明髁突扭转最小，表明近端和远端节段在直板固定的前垂直截骨处保持接触。前徙病例术后平均外侧髁突扭转2.2°（<0.005，高度显著）。这表明内嵌弯曲钢板固定维持了前垂直截骨部位近端节段的张开。
应维持下颌前徙和后退所造成的近端和远端节段之间的间隙。试图闭合这些间隙，尤其是在下颌前徙时，将导致不利的轴向髁突扭矩。因此，下颌前徙和后退所造成的近端和远端截骨部位之间的骨接触区域也应维持。
