下颌骨三维重建、有限元学分析及在下颌角截骨整形术中的临床应用研究
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摘要
第一部分正常成年女性下颌角多层螺旋CT解剖学研究
目的：
通过对60例成年女性正常下颌角16排螺旋CT容积扫描及后续的三维重建,分析下颌角大体形态学特点、不同部位的骨皮质厚度及下颌神经管解剖学特点,为下颌角截骨整形术提供解剖学基础。
材料与方法：
对60例(120侧)健康成年女性行多层螺旋CT检查,年龄20～43岁,平均27.1岁；身高152-183 cm,平均166.5 cm；体重40～95 kg,平均57.3 kg。所有受检查者均无下颌骨相关外伤手术史。CT扫描方法：采用GE公司Light speed 16多层螺旋CT机,常规横断面扫描,扫描基线相当于听眦线,扫描范围包括完整下颌骨,层厚0.625mm,无间隔容积扫描,管电压120 kV,管电流260 mAs,骨算法重建；原始数据导入ADW4.2工作站进行容积重建(Volume Reconstruction, VR)、多平面重建(Multi Planar Reconstruction, MPR),窗宽2000 Hu,窗位500 Hu。
三维重建包括VR和MPR, MPR可得到标准冠状面、矢状面和任意角度斜矢状面、冠状面图像,通过调整不同的轴线即可获得各种切面的重组图像。VR可以整体观察下颌角大体解剖学特点。
在VR图像上通过咬合平面画一直线,与下颌骨后缘相交处为点A；通过颏孔与下颌骨下缘平行画一平行线,与下颌骨后缘相交处为点B；通过下颌骨升支前缘做下颌骨下缘的垂线,与下颌骨下缘相交处为点C；通过颏孔与下颌骨下缘做一垂线,相交处为点D；AB段规定为下颌骨后缘,BC段规定为下颌角区,CD段规定为下颌骨下缘。在VR图像上定位,每一段分别测量五个点,MPR图像上自动匹配,分别在MPR上测量五个点对应内板、外板及内外板在边缘反折部骨皮质厚度,每一段五个点的平均值作为该段内、外板及边缘骨皮质厚度,本组测量60例120侧下颌骨骨皮质厚度。所得数据采用SPSS10.0统计软件处理,计算平均值、标准差及变异系数,双侧下颌骨骨皮质厚度做配对样本t检验。P值<0.05认为差别具有统计学意义。
MPR重建测量下颌神经管在不同位置距下颌骨外板及下缘的距离,对测得的数据进行统计学分析。
结果：
1.下颌角大体形态学观察
下颌骨下缘与后缘的连接方式可分为单角转折型(11.67%)、双角转折型(8.33%)、角度过渡型(73.33%)和后下突型(6.67%)；下颌角区相对于下颌骨中轴面的位置关系可分为外翻型(11.67%)、中位型(70.00%)和内翻型(18.33%)。
2.下颌角区骨皮质厚度
左侧下颌骨后缘内、外板及边缘骨皮质厚度分别为2.12±0.29mm,2.89±0.35mm,4.40±0.66mm；左侧下颌角内、外板及边缘骨皮质厚度分别为2.13±0.35mm,2.91±0.35mm,5.76±1.22mm；左侧下颌骨下缘内、外板及边缘骨皮质厚度分别为2.18±0.41mm,3.01±0.42mm,4.29±0.68mm。右侧下颌骨后缘内外板及边缘骨质厚度分别为2.14±0.25mm,2.73±0.29mm,4.19±0.60mm；右侧下颌角内、外板及边缘骨皮质厚度分别为2.24±0.24mm,2.76±0.32mm,5.65±1.09mm；右侧下颌骨下缘内、外板及边缘骨皮质厚度分别为2.40±0.39mm,2.98±0.42mm,4.14±0.64mm。双侧下颌骨后缘外板及反折处(PE：t=4.882,P=0.000；PM：t=2.974,P=0.004),下颌角内外板(AI：t=3.394,P=0.001；AE：t=4.217,P=0.000)及下颌骨下缘内板差异具有统计学意义(Ⅱ：t=6.540,P<0.05),其余两侧各段骨皮质厚度差异无统计学意义。
3.下颌神经管测量下颌神经管距离下颌骨外板在第三磨牙层面距离最小(左侧4.20±1.05mm；右侧4.27±1.00mm),在第一二磨牙间距离最大(左侧5.73±1.40mm；右侧5.58±1.38mm)；距离下缘距离与之相反,第三磨牙层面距离最大(左侧8.50±2.09mm；右侧8.82±2.42mm),一二磨牙间距离最小(左侧6.98±0.72mm；右侧6.87±0.91mm)。下颌神经管除了在第三磨牙层面距离下颌骨下缘的距离有统计学意义外(LA：t=10.928, P<0.001),其余各点下颌神经管距外板、下缘无统计学意义。
结论：
1.多层螺旋CT可以在活体三维立体观察下颌骨后缘、下颌角、下缘形态,术前可以详细了解下颌角形态学特点,为手术计划提供重要参考信息,对下颌角截骨整形术有重要的临床意义。
2.多层螺旋CT可以对下颌骨后缘、下颌角、下颌骨下缘的骨皮质厚度进行精确测量,在观察骨性结构的同时还可显示周围软组织情况,对下颌角截骨整形术有重要的临床指导意义,可确保手术精确实施、降低手术难度、减少手术的并发症。
3.多层螺旋CT容积扫描及三维重建,能够很好的显示下颌神经管位置、走行方向及与周围结构的关系,避免下颌角截骨整形术中意外损伤下颌神经管内的血管神经束。
目的：
应用三维有限元分析技术,建立下颌骨三维有限元模型,研究以切除部分下颌骨骨质为手段的下颌角截骨整形术术后下颌骨生物力学的变化情况,得出下颌角截骨整形术截除骨质的安全边际,寻找下面部轮廓塑形效果与生物力学变化的最佳平衡点。
方法：
选择颅颌系统发育正常、Ⅰ类磨牙关系的健康女性青年志愿者,64排螺旋CT颞下颌关节区及下颌骨轴向断层、连续无间隔扫描,利用Mimics 12.0和Ansys12.0软件,根据实验设计要求进行分割、平滑、三维网格划分,并加入材料力学参数设定和模型的边界约束设计,生成不含下牙列和带有肌肉、韧带约束的正常下颌骨三维有限元全模型(对照组)。在此模型基础上分别建立切除下颌缘的模型1和切除部分下颌骨的模型2(实验组),在颏联合处下缘受力面相应节点上加载撞击力响应曲线,应用Ansys12.0软件运算得出实验组与对照组下颌骨应力分布云图及应力分布动态变化图。于下颌骨髁突颈、下颌体、水平支与升支交界处选取3个节点,软件运算得出3个节点的应力-时间载荷响应曲线,并提取各节点上应力传导历程中以1ms为时间间隔单位的应力数据以及最大应力。随后将建立的模型1和模型2分别导入Ansys12.0软件,重复上述求解步骤,求解实验组与对照组应力分布云图、应力分布动态变化图、时间-应力载荷响应曲线以及上述3个节点的应力数据。
结果：
1.建立的带有肌肉和韧带约束的正常下颌骨三维有限元模型及模型1、模型2。
2.下颌骨全模型应力分布情况
颏部受撞击后1.8ms,撞击应力开始向四周扩散,应力传导主要沿外斜线方向传播并且集中于髁突颈部。撞击后12.5ms髁突颈前内侧受力集中部位达到应力的峰值后,下颌骨各处应力呈回落状态,随后下颌骨各部位应力渐消散。在整个过程中,按本研究前期划分的下颌骨后缘、下颌角区、下缘近下颌角区域一直处于应力较小的状态。
3.实验组模型1下颌骨模型应力分布情况
模型1的应力传导和分布与正常下颌骨很相似,但下颌骨各部应力范围、强度明显减小,在云图上表现出较正常下颌骨云图颜色变浅,同种颜色区域变小。在加载撞击载荷11～12.5ms后,下颌骨乙状切迹、喙突以及牙槽脊附近较颜色较正常下颌骨由应力较小的浅蓝色变成代表应力较大的黄色。
4.实验组模型2下颌骨模型应力分布情况
模型2的应力传导和分布与模型1相似,但下颌骨各部应力范围、强度进一步减小,在云图上表现出较正常下颌骨云图颜色变浅,同种颜色区域变小。在加载撞击载荷11-12.5ms后,下颌骨乙状切迹、喙突以及牙槽脊附近较模型1黄色加深,表明该区域应力进一步加大。
5.下颌骨髁突颈、水平支与升支交界处节点、下颌体时间-应力曲线
各模型下颌骨髁突颈、水平支与升支交界处节点、下颌体时间-应力曲线形态大致相同。但峰值大小以及在应力消散前的波形存在差别。在A点峰值变化最大,模型2形成2个较明显的反弹波。B点在应力消散前下颌骨全模型1反弹波不明显,模型2有反弹波出现。C点在应力消散前下颌骨全模型没有反弹波,模型1反弹波不明显,模型2有明显的2个反弹波出现。
6.下颌骨髁突颈A点、水平支与升支交界处B点、下颌体C点应力统计学分析
经方差分析,三组不同位置受力情况方差不齐(a：F=3.174,P<0.05；b：F=29.204,P=0.000；c：F=20.051,P=0.000),用Dennett's法进行不同组间多重比较,结果表明：A点三组间差异均无统计学意义(P>0.05),B点全模型组与模型1、模型2差异具有统计学意义(P<0.05),后两组间差异无统计学意义(P>0.05)；C点全模型组与模型1差别具有统计学意义(P<0.05),与模型2差别无明显统计学意义(P>0.05)。
结论：
1.下颌骨受撞击后,下颌骨的应力主要沿外斜线方向传播并且集中于髁突颈部。
2.切除下颌骨后缘、下颌角、下颌骨下缘骨质能够引起下颌骨乙状切迹、喙突以及牙槽脊附近应力上升。
3.切除骨质越多应力上升越多,使下颌骨较前更易断裂。
第三部分下颌角截骨整形术的临床应用研究
目的：
评价下颌角截骨整形术患者的临床特点、手术方法以及术后效果；观察MSCT在下颌角截骨整形术的临床应用价值。
方法：
自2007年10月至2009年11月,共计完成下颌角截骨整形术119例,所有患者均行术前大体检查和X线检查。本组患者119例,女性115例229侧,男性4例7侧,年龄19～43岁,平均28.3岁；所有患者颌面部发育正常,咬合关系正常,无咬合障碍,无颞下颌关节紊乱综合征(TMJDS)症状和体征,无下颌骨相关外伤手术史。下颌角肥大以骨性肥大为主,表现为下颌角骨质增生突出,下颌角间距增宽。其中25例同期行颧骨缩小整形术,6例同期行假体隆颏术。
本组资料中共计进行术前三维重建及术前模拟21例,其中7例术后一周至三个月进行了术后三维重建。螺旋CT扫描方法及重建方法同第一部分。
运用Mirror system软件,将重建的下颌骨三维图像载入,利用软件的拉伸、平移、切割、旋转、拼接、扩大等功能,依据既往文献报道的下面部骨骼轮廓的美学标准,并参考患者提出的要求以及结合功能、形态的综合因素,模拟出骨处理后的手术效果,最终与术后下颌骨三维重建图像进行比较。
结果：
119例受术者中,随访3个月共93例,术者、受术者均认为下面部轮廓明显改善、效果满意88例,占所有病例73.95%,随访6个月以上的57例,效果满意56例,占所有病例47.06%。
结论：
1.下颌角截骨整形术对矫正下颌角肥大具有良好的效果,术前详细了解患者的骨性结构特点有助于提高手术的成功率和降低并发症的发生。
2.基于螺旋CT重建的三维图像可帮助下颌角截骨整形手术方案的确定、术前模拟训练术者,并评价手术效果。
3.截骨线及骨处理方式方法应根据下颌角的分类及分型确定。
Part one:The anatomic study of normal adult female mandibular angle with multi-slice spiral CT
Objective:Through the normal mandibular angle of 60 cases of adult women undergone 16-slice spiral CT volume scanning and three dimensional reconstruction, to analyze the anatomical characteristics of the mandibular angle in general, the mandibular cortical bone in different place and the anatomic characteristic of neural tube, and to provide anatomical basis for surgery of narrow the mandibular angle.
Methods:60 cases healthy adult female (120 sides) were included in this study. The patients ranged in age from 20 to 43 years (mean age 27.1 years). The patients ranged in height from 152 to 183 centimeter with a mean height of 166.5 centimeter. the patients ranged in weight from 40 to 95 kilogram with a mean weight of 57.3 kilogram. All patients have no history of mandibular trauma or operation. Use of, GE Light speed 16 multi-slice spiral CT machine, conventional cross-sectional scanning was performed, the scanning baseline was vertical to the longitudinal section of the body corresponding to MC line. Scan range including a complete mandible, slice thickness 0.625 mm, no interval volume scan. Tube voltage 120 kV, tube current 260 mAs. Bone algorithm reconstruction was performed. The raw data were imported into ADW4.2 workstation, volume reconstruction (VR), MPR reconstruction were performed, window width 2000 Hounsfield unit, window level 500 Hounsfield unit.
Three dimensional reconstruction, including volume reconstruction (VR) and multi planar reconstruction (MPR). To get the standard coronal plane, sagittal plane and arbitrary angles sagittal and coronal plane images, by adjusting the different axes can get all the facets of the reorganization of the image.Through volume reconstruction, we can observe the whole general anatomical characteristics of the mandibular angle.
On VR image a straight line was drawn through the occlusal plane with the back edge of the mandible as a point of intersection of A; Through the mental foramen to draw a parallel line with the inferior margin of mandible parallel the back edge of and intersect with the mandible to the intersection point of B; Through the front edge of mandibular ramus mandible to do the vertical of the inferior margin of mandible and the intersection point as a point C; Through the mental foramen to do a vertical with the inferior margin of mandible, intersecting at the point of D. The AB segment defined as posterior margin of mandible, BC segment defined as angle of mandible area and CD segment defined as inferior border of mandible. In the VR image positioning, each section were measured five points. MPR images automatically match, on MPR measured the thickness of the cortical bone at five points correspond to the inner plate, outer plate and edge, respectively. In this group we measured 60 cases of 120 lateral mandibular cortical bone thickness. SPSS10.0 statistical software were used to process the data, calculation of mean, standard deviation and coefficient of variation, bilateral mandibular cortical bone thickness did two independent samples t test. P<0.05 was considered statistically significant difference.
MPR reconstruction of the mandibular nerve canal measured from the mandible in different locations outside the board and the distance between the lower edge of the measured data were analyzed statistically.
Result:
1. The general morphology of mandibular angle The connection mode of the lower edge of mandible and post-edge have four types:single-angle turn-based (11.67%), biangle turn-based (8.33%), angel transition form (73.33%), anterior-posterior project type (6.67%); The position relation of angle of mandible with the axial plane of the mandible have three types:extraversion (11.67%), neutral (70.00%), enstrophe (18.33%).
2. Cortical bone thickness of the mandibular angle area
The exterior, interior and marginal cortical bone thickness of the left posterior border of mandible are 2.12±0.29mm,2.89±0.35mm,4.40±0.66mm; The exterior, interior and marginal cortical bone thickness of the left angle of mandible are 2.13±0.35 mm,2.91±0.35 mm,5.76±1.22 mm; The exterior, interior and marginal cortical bone thickness of the left inferior border of mandible are 2.18±0.41mm,3.01±0.42mm,4.29±0.68mm.The exterior, interior and marginal cortical bone thickness of the right posterior border of mandible are 2.14±0.25 mm,2.73±0.29mm,4.19±0.60mm; The exterior, interior and marginal cortical bone thickness of the right angle of mandible are 2.24±0.24mm,2.76±0.32mm, 5.65±1.09mm; The exterior, interior and marginal cortical bone thickness of the right inferior border of mandible are 2.40±0.39mm,2.98±0.42mm, 4.14±0.64mm. bilateral exterior cortical bone thickness of the posterior border of mandible (PE:t=4.882, P=0.000; PM:t=2.974, P=0.004), exterior cortical bone thickness of the angle of mandible (AI:t=3.394, P=0.001; AE:t=4.217, P=0.000), and interior cortical bone thickness of the inferior border of mandible (Ⅱ:t=6.540, P<0.05) have statistically significant, other part have not statistically significant.
3. The measure of the mandibular neural tube
The distance of the neural tube to the outer edge of the mandibular jaw in the third molar level is the minimum (left 4.20±1.05; right 4.27±1.00); The maximum distance between the first two molars (left 5.73±1.40 mm; right 5.58±1.38 mm); The distance of the neural tube to the lower edge of the mandibular jaw in the third molar level is the maximum (left 8.50±2.09 mm; right 8.82±2.42 mm), the smallest distance is between the First molar and second molar (left 6.98±0.72mm; right 6.87±0.91 mm)
Conclusions:
1. Multi-slice spiral CT can three-dimensional observed the posterior edge of the mandible, mandibular angle, the lower edge of shape in vivo, preoperative evaluation of mandibular angle can be quasi-morphological characteristics of the surgical plan to provide important reference information, for mandibular angle narrowing surgery has important clinical significance.
2. With Multi-slice spiral CT can precisely measure the cortical bone thickness of the back edge of the mandible, mandibular angle, the lower edge of mandibular. In the observation of bone structures at the same time can observe the soft tissue, for narrowing the mandibular angle surgery has important clinical significance. To ensure accurate implementation of the procedure, reducing operative difficulties, reduce surgical complications.
3. Multi-slice spiral CT volume scanning and three-dimensional reconstruction can be a very good display of the mandibular neural tube and its traveling direction and the relationship between the surrounding structures, for mandibular surgery to say have an important clinical significance.
Part two:Three-dimensional finite element analysis of mandible biomechanics
Objective:With the three-dimensional finite element method, a three-dimensional finite element model of mandible was constructed; the biomechanical characteristic variation of mandible after the mandibular angle osteotomy anaplasty by the means of partial resection surgery of mandibular bone was studied; a safety margin for the bone resection surgery of the mandibular angle osteotomy anaplasty was obtained; and an optimal balance point between the remodeling effect of the lower facial contour and the mechanical variation was observed.
Method:A group of healthy young female volunteers with the well-developed craniomandibular system and the class I molar relationship was selected; the temporomandibular joint region and the mandible bone were examined through serial scan and axial tomography of the 64-slice spiral CT; the Mimics12.0 and the Ansys12.0 software were used for segmentation, smoothing processing and three-dimensional mesh generation according to the experimental requirement;with the addition of parameter setting for material mechanics and the boundary constraint design, a three-dimensional finite element model (control group) of a normal mandible with the muscle and ligament constraint for the mandible without the lower teeth was constructed. On the basis of the three-dimensional finite element model (control group), a model 1 with the resection of mandibular margin and a model 2 with the partial resection of mandible were constructed respectively (experimental group); an impact response curve was added at the corresponding point on the stress surface of the lower edge of the symphysis; the mandible stress nephogram and the dynamic stress variation nephogram of the mandible in the control group and the experimental group were calculated through the Ansys12.0 software. Three points were chosen at the mandible condyle, the mandibular body and the junction between the horizontal branch and the mandibular ramus; the stress-time load response curves of the three points were calculated through the software; and the stress data of each point with a 1ms time interval unit during the stress conduction process and the maximal stress of the points were extracted. Afterwards, the model 1 and the model 2 were introduced into the Ansys12.0 software respectively; the above solving steps were repeated; and the stress nephogram, the dynamic stress variation nephogram and the time-stress load response curve for the control group and the experimental group and the stress data of the above three points were calculated.
Result:
1. A three-dimensional finite element model of the normal mandible with muscle and ligament constraint, a model 1 and a model 2 were constructed.
2. The stress distribution on the whole model of the mandible
The impact stress began to spread around 1.8ms after the mentum impact and the stress mainly conducted along the external oblique direction and concentrated at the mandible condyle. After the stress on the concentration part of the anterior，internal side of the mandible condyle reached the summit of the stress 12.5ms after the impact, the stress on the mandible was in a downward status and disappeared gradually. In the whole process, the posterior edge of the mandible, the mandibular angle area and the lower edge which was close to the mandibular angle area mentioned in the former part of the study were always in a less stress state.
3. The stress distribution of the mandible model 1 of the experimental group
The stress conduction and distribution of the model were similar to the normal mandible; however, the scope and the intensity of the stress on the mandible were reduced apparently. Compared with the nephogram of the normal mandible, the color intensity of the nephogram of model 1 was weakened and the similar color area became smaller. After 11～12.5ms the addition of the impact load, the color of the surrounding area of the sigmoid incisure of mandible, coracoid process and alveolar ridge turned from less stress blue into more stress yellow when compared with the normal mandible.
4. The stress distribution of the mandible model 2 of the experimental group
The stress conduction and distribution of the model were similar to the mandible model 1; however, the scope and the intensity of the stress on the mandible were reduced furtherly. Compared with the nephogram of the normal mandible, the color intensity of the nephogram of model 1 was weakened and the similar color area became smaller. After 11～12.5ms the addition of the impact load, the yellow color intensity of the surrounding area of the moid notch of the mandible, coracoid process and alveolar ridge became stronger when compared with the mandible model 1. The result shows that the stress in this area was increased furtherly.
5. The time-stress curves of the mandible condyle, the point at the junction between the horizontal branch and the mandibular ramus and the mandibular body
The curve morphology of the mandible condyle, the point at the junction between the horizontal branch and the mandibular ramus and the mandibular body of each model are almost identical. However, there is difference in the summit value and the waveform before the disappearance of the stress. The maximal variation of the summit value appears at A point; two apparent rebound waves exist in mandible model 2. The rebound wave of the mandible model 1 before the disappearance of the stress at B point is not obvious; however, there is rebound wave in mandible model 2. There is no rebound wave in the mandible model before the disappearance of the stress at C point; however, the rebound wave of the mandible model 1 is not obvious; there are two apparent rebound waves in mandible model 2.
6. Statistical analysis for the stress at A point of the mandible condyle, B point at the junction between the horizontal branch and the mandibular ramus and C point of the mandibular body
With the anova analysis, the variance of the stress at different sites of the three groups are irregular (a:F=3.174, P< 0.05; b:F=29.204, P=0.000; c:F=20.051, P=0.000); the multiple comparison among different groups is conducted through using the Dennetts method. The result shows that there is no statistical difference among three groups at A point(P> 0.05); there is statistical difference between the normal mandible group and the model 1 and the model 2 at B point (P< 0.05); there is no statistical difference between the model 1 and the model 2 at B point (P> 0.05); there is statistical difference between the normal mandible group and the model 1 at C point (P< 0.05); and there is no statistical difference between the normal mandible group and the model 2 at C point (P> 0.05).
Conclusion:
1. After the impact of the mandible, the stress was mainly conducted along the external oblique direction and concentrated at the mandible condyle.
2. The resection of the posterior edge of the mandible,the mandibular angle and the lower edge of the mandible can cause the elevation of the stress in the surrounding area of the sigmoid incisure of mandible, coracoid process and alveolar ridge.
3. The more bone was excised, the more stress was increased and the more fragile the mandible became.
Part three:The clinical experience of Mandibular angle osteotomy plastic surgery and the clinical applied research of Multi-slice computed tomography on Mandibular angle osteotomy plastic surgery
Objective:Evaluation the clinical features of patients with mandibular angle osteotomy plastic surgery and the results of operation, meanwhile to observe the clinicalapplication value of multi-slice computed tomography.
Methods:Since October 2007 to November 2009, Total completion 119 cases of the mandibular angle osteotomy plastic surgery, all patients underwent preoperative general examination and X-ray examination. In this group there have 119 cases, among of which there have 115 female (229 sides),4 cases men (7 sides).19 to 43 years of age and with a mean age 28.3 years. All patients maxillofacial region growth normally, occluding relation normal and have no occlusion barrier, have no sings and symptoms of temporomandibular joint disturbance syndrome, have no history of mandibular operation and trauma. The hypertrophy of mandibular angle to the main bone hypertrophy, Showed as prominent mandibular angle bone hyperplasia and Mandibular angle spacing widened. Among of which there have 25 cases undergone zygoma diminutionplasty,6 cases undergone prosthesis chin augmentation.
In this group there have 21 cases have preoperative three-dimensional reconstruction and preoperative simulation, among of which there have 7 cases undergone postoperative three-dimensional reconstruction from 1 week to 12 weeks after the operation. Spiral CT scanning method and reconstruction method just like part one.
To make use of Mirror system software, loading the three dimensional picture of mandible, use the stretching, panning, cutting, rotation, stitching and expanding functions of the software, based on the standards of the ministry of bone in past reported literature the following outline of the aesthetic, and made reference to the request of the patients, as well as with combined features, form a combination of factors and then simulate the effect of surgical treatment of the bone, after that make a comparison with postoperation three-dimensional reconstruction.
Result:
In patients with large mandibular angle with zygomatic distance of 131.2mm; the preoperation distance between mandibular angle is 116.5mm and postoperation distance is 101.8mm, Than preoperation shrunk 14.7mm. Preoperative lateral angle of the mandibular angle is 114.1°, and postoperation is 126.2°.
There have 93 patients being followed up about 3 months in 119 patient's undergone operation, there have 88 cases the surgeon and patients consider significant improvement in facial contour and have satisfactory result, accounted for 73.95% of all cases.57 cases followed up about for 6 months and among of which 56 patients get satisfactory result, accounted for 47.06% of all cases.
Conclusions:
1. The mandibular angle osteotomy plastic surgery of the mandibular angle has a good effect, Learn more about preoperative patient characteristics of bone structure help increase the success rate of surgery and reduce the incidence of complications.
2. Spiral CT in the preoperative mandibular angle osteotomy and plastic surgery can help determine the surgical plan, simulate the operation and evaluate the results of operations.
3. The osteotomy line and the way of the bone process should dicided by the typing and classification of the mandibular angle.
目的：
通过对60例成年女性正常下颌角16排螺旋CT容积扫描及后续的三维重建,分析下颌角大体形态学特点、不同部位的骨皮质厚度及下颌神经管解剖学特点,为下颌角截骨整形术提供解剖学基础。
材料与方法：
对60例(120侧)健康成年女性行多层螺旋CT检查,年龄20～43岁,平均27.1岁；身高152-183 cm,平均166.5 cm；体重40～95 kg,平均57.3 kg。所有受检查者均无下颌骨相关外伤手术史。CT扫描方法：采用GE公司Light speed 16多层螺旋CT机,常规横断面扫描,扫描基线相当于听眦线,扫描范围包括完整下颌骨,层厚0.625mm,无间隔容积扫描,管电压120 kV,管电流260 mAs,骨算法重建；原始数据导入ADW4.2工作站进行容积重建(Volume Reconstruction, VR)、多平面重建(Multi Planar Reconstruction, MPR),窗宽2000 Hu,窗位500 Hu。
三维重建包括VR和MPR, MPR可得到标准冠状面、矢状面和任意角度斜矢状面、冠状面图像,通过调整不同的轴线即可获得各种切面的重组图像。VR可以整体观察下颌角大体解剖学特点。
在VR图像上通过咬合平面画一直线,与下颌骨后缘相交处为点A；通过颏孔与下颌骨下缘平行画一平行线,与下颌骨后缘相交处为点B；通过下颌骨升支前缘做下颌骨下缘的垂线,与下颌骨下缘相交处为点C；通过颏孔与下颌骨下缘做一垂线,相交处为点D；AB段规定为下颌骨后缘,BC段规定为下颌角区,CD段规定为下颌骨下缘。在VR图像上定位,每一段分别测量五个点,MPR图像上自动匹配,分别在MPR上测量五个点对应内板、外板及内外板在边缘反折部骨皮质厚度,每一段五个点的平均值作为该段内、外板及边缘骨皮质厚度,本组测量60例120侧下颌骨骨皮质厚度。所得数据采用SPSS10.0统计软件处理,计算平均值、标准差及变异系数,双侧下颌骨骨皮质厚度做配对样本t检验。P值<0.05认为差别具有统计学意义。
MPR重建测量下颌神经管在不同位置距下颌骨外板及下缘的距离,对测得的数据进行统计学分析。
结果：
1.下颌角大体形态学观察
下颌骨下缘与后缘的连接方式可分为单角转折型(11.67%)、双角转折型(8.33%)、角度过渡型(73.33%)和后下突型(6.67%)；下颌角区相对于下颌骨中轴面的位置关系可分为外翻型(11.67%)、中位型(70.00%)和内翻型(18.33%)。
2.下颌角区骨皮质厚度
左侧下颌骨后缘内、外板及边缘骨皮质厚度分别为2.12±0.29mm,2.89±0.35mm,4.40±0.66mm；左侧下颌角内、外板及边缘骨皮质厚度分别为2.13±0.35mm,2.91±0.35mm,5.76±1.22mm；左侧下颌骨下缘内、外板及边缘骨皮质厚度分别为2.18±0.41mm,3.01±0.42mm,4.29±0.68mm。右侧下颌骨后缘内外板及边缘骨质厚度分别为2.14±0.25mm,2.73±0.29mm,4.19±0.60mm；右侧下颌角内、外板及边缘骨皮质厚度分别为2.24±0.24mm,2.76±0.32mm,5.65±1.09mm；右侧下颌骨下缘内、外板及边缘骨皮质厚度分别为2.40±0.39mm,2.98±0.42mm,4.14±0.64mm。双侧下颌骨后缘外板及反折处(PE：t=4.882,P=0.000；PM：t=2.974,P=0.004),下颌角内外板(AI：t=3.394,P=0.001；AE：t=4.217,P=0.000)及下颌骨下缘内板差异具有统计学意义(Ⅱ：t=6.540,P<0.05),其余两侧各段骨皮质厚度差异无统计学意义。
3.下颌神经管测量下颌神经管距离下颌骨外板在第三磨牙层面距离最小(左侧4.20±1.05mm；右侧4.27±1.00mm),在第一二磨牙间距离最大(左侧5.73±1.40mm；右侧5.58±1.38mm)；距离下缘距离与之相反,第三磨牙层面距离最大(左侧8.50±2.09mm；右侧8.82±2.42mm),一二磨牙间距离最小(左侧6.98±0.72mm；右侧6.87±0.91mm)。下颌神经管除了在第三磨牙层面距离下颌骨下缘的距离有统计学意义外(LA：t=10.928, P<0.001),其余各点下颌神经管距外板、下缘无统计学意义。
结论：
1.多层螺旋CT可以在活体三维立体观察下颌骨后缘、下颌角、下缘形态,术前可以详细了解下颌角形态学特点,为手术计划提供重要参考信息,对下颌角截骨整形术有重要的临床意义。
2.多层螺旋CT可以对下颌骨后缘、下颌角、下颌骨下缘的骨皮质厚度进行精确测量,在观察骨性结构的同时还可显示周围软组织情况,对下颌角截骨整形术有重要的临床指导意义,可确保手术精确实施、降低手术难度、减少手术的并发症。
3.多层螺旋CT容积扫描及三维重建,能够很好的显示下颌神经管位置、走行方向及与周围结构的关系,避免下颌角截骨整形术中意外损伤下颌神经管内的血管神经束。
目的：
应用三维有限元分析技术,建立下颌骨三维有限元模型,研究以切除部分下颌骨骨质为手段的下颌角截骨整形术术后下颌骨生物力学的变化情况,得出下颌角截骨整形术截除骨质的安全边际,寻找下面部轮廓塑形效果与生物力学变化的最佳平衡点。
方法：
选择颅颌系统发育正常、Ⅰ类磨牙关系的健康女性青年志愿者,64排螺旋CT颞下颌关节区及下颌骨轴向断层、连续无间隔扫描,利用Mimics 12.0和Ansys12.0软件,根据实验设计要求进行分割、平滑、三维网格划分,并加入材料力学参数设定和模型的边界约束设计,生成不含下牙列和带有肌肉、韧带约束的正常下颌骨三维有限元全模型(对照组)。在此模型基础上分别建立切除下颌缘的模型1和切除部分下颌骨的模型2(实验组),在颏联合处下缘受力面相应节点上加载撞击力响应曲线,应用Ansys12.0软件运算得出实验组与对照组下颌骨应力分布云图及应力分布动态变化图。于下颌骨髁突颈、下颌体、水平支与升支交界处选取3个节点,软件运算得出3个节点的应力-时间载荷响应曲线,并提取各节点上应力传导历程中以1ms为时间间隔单位的应力数据以及最大应力。随后将建立的模型1和模型2分别导入Ansys12.0软件,重复上述求解步骤,求解实验组与对照组应力分布云图、应力分布动态变化图、时间-应力载荷响应曲线以及上述3个节点的应力数据。
结果：
1.建立的带有肌肉和韧带约束的正常下颌骨三维有限元模型及模型1、模型2。
2.下颌骨全模型应力分布情况
颏部受撞击后1.8ms,撞击应力开始向四周扩散,应力传导主要沿外斜线方向传播并且集中于髁突颈部。撞击后12.5ms髁突颈前内侧受力集中部位达到应力的峰值后,下颌骨各处应力呈回落状态,随后下颌骨各部位应力渐消散。在整个过程中,按本研究前期划分的下颌骨后缘、下颌角区、下缘近下颌角区域一直处于应力较小的状态。
3.实验组模型1下颌骨模型应力分布情况
模型1的应力传导和分布与正常下颌骨很相似,但下颌骨各部应力范围、强度明显减小,在云图上表现出较正常下颌骨云图颜色变浅,同种颜色区域变小。在加载撞击载荷11～12.5ms后,下颌骨乙状切迹、喙突以及牙槽脊附近较颜色较正常下颌骨由应力较小的浅蓝色变成代表应力较大的黄色。
4.实验组模型2下颌骨模型应力分布情况
模型2的应力传导和分布与模型1相似,但下颌骨各部应力范围、强度进一步减小,在云图上表现出较正常下颌骨云图颜色变浅,同种颜色区域变小。在加载撞击载荷11-12.5ms后,下颌骨乙状切迹、喙突以及牙槽脊附近较模型1黄色加深,表明该区域应力进一步加大。
5.下颌骨髁突颈、水平支与升支交界处节点、下颌体时间-应力曲线
各模型下颌骨髁突颈、水平支与升支交界处节点、下颌体时间-应力曲线形态大致相同。但峰值大小以及在应力消散前的波形存在差别。在A点峰值变化最大,模型2形成2个较明显的反弹波。B点在应力消散前下颌骨全模型1反弹波不明显,模型2有反弹波出现。C点在应力消散前下颌骨全模型没有反弹波,模型1反弹波不明显,模型2有明显的2个反弹波出现。
6.下颌骨髁突颈A点、水平支与升支交界处B点、下颌体C点应力统计学分析
经方差分析,三组不同位置受力情况方差不齐(a：F=3.174,P<0.05；b：F=29.204,P=0.000；c：F=20.051,P=0.000),用Dennett's法进行不同组间多重比较,结果表明：A点三组间差异均无统计学意义(P>0.05),B点全模型组与模型1、模型2差异具有统计学意义(P<0.05),后两组间差异无统计学意义(P>0.05)；C点全模型组与模型1差别具有统计学意义(P<0.05),与模型2差别无明显统计学意义(P>0.05)。
结论：
1.下颌骨受撞击后,下颌骨的应力主要沿外斜线方向传播并且集中于髁突颈部。
2.切除下颌骨后缘、下颌角、下颌骨下缘骨质能够引起下颌骨乙状切迹、喙突以及牙槽脊附近应力上升。
3.切除骨质越多应力上升越多,使下颌骨较前更易断裂。
第三部分下颌角截骨整形术的临床应用研究
目的：
评价下颌角截骨整形术患者的临床特点、手术方法以及术后效果；观察MSCT在下颌角截骨整形术的临床应用价值。
方法：
自2007年10月至2009年11月,共计完成下颌角截骨整形术119例,所有患者均行术前大体检查和X线检查。本组患者119例,女性115例229侧,男性4例7侧,年龄19～43岁,平均28.3岁；所有患者颌面部发育正常,咬合关系正常,无咬合障碍,无颞下颌关节紊乱综合征(TMJDS)症状和体征,无下颌骨相关外伤手术史。下颌角肥大以骨性肥大为主,表现为下颌角骨质增生突出,下颌角间距增宽。其中25例同期行颧骨缩小整形术,6例同期行假体隆颏术。
本组资料中共计进行术前三维重建及术前模拟21例,其中7例术后一周至三个月进行了术后三维重建。螺旋CT扫描方法及重建方法同第一部分。
运用Mirror system软件,将重建的下颌骨三维图像载入,利用软件的拉伸、平移、切割、旋转、拼接、扩大等功能,依据既往文献报道的下面部骨骼轮廓的美学标准,并参考患者提出的要求以及结合功能、形态的综合因素,模拟出骨处理后的手术效果,最终与术后下颌骨三维重建图像进行比较。
结果：
119例受术者中,随访3个月共93例,术者、受术者均认为下面部轮廓明显改善、效果满意88例,占所有病例73.95%,随访6个月以上的57例,效果满意56例,占所有病例47.06%。
结论：
1.下颌角截骨整形术对矫正下颌角肥大具有良好的效果,术前详细了解患者的骨性结构特点有助于提高手术的成功率和降低并发症的发生。
2.基于螺旋CT重建的三维图像可帮助下颌角截骨整形手术方案的确定、术前模拟训练术者,并评价手术效果。
3.截骨线及骨处理方式方法应根据下颌角的分类及分型确定。
Part one:The anatomic study of normal adult female mandibular angle with multi-slice spiral CT
Objective:Through the normal mandibular angle of 60 cases of adult women undergone 16-slice spiral CT volume scanning and three dimensional reconstruction, to analyze the anatomical characteristics of the mandibular angle in general, the mandibular cortical bone in different place and the anatomic characteristic of neural tube, and to provide anatomical basis for surgery of narrow the mandibular angle.
Methods:60 cases healthy adult female (120 sides) were included in this study. The patients ranged in age from 20 to 43 years (mean age 27.1 years). The patients ranged in height from 152 to 183 centimeter with a mean height of 166.5 centimeter. the patients ranged in weight from 40 to 95 kilogram with a mean weight of 57.3 kilogram. All patients have no history of mandibular trauma or operation. Use of, GE Light speed 16 multi-slice spiral CT machine, conventional cross-sectional scanning was performed, the scanning baseline was vertical to the longitudinal section of the body corresponding to MC line. Scan range including a complete mandible, slice thickness 0.625 mm, no interval volume scan. Tube voltage 120 kV, tube current 260 mAs. Bone algorithm reconstruction was performed. The raw data were imported into ADW4.2 workstation, volume reconstruction (VR), MPR reconstruction were performed, window width 2000 Hounsfield unit, window level 500 Hounsfield unit.
Three dimensional reconstruction, including volume reconstruction (VR) and multi planar reconstruction (MPR). To get the standard coronal plane, sagittal plane and arbitrary angles sagittal and coronal plane images, by adjusting the different axes can get all the facets of the reorganization of the image.Through volume reconstruction, we can observe the whole general anatomical characteristics of the mandibular angle.
On VR image a straight line was drawn through the occlusal plane with the back edge of the mandible as a point of intersection of A; Through the mental foramen to draw a parallel line with the inferior margin of mandible parallel the back edge of and intersect with the mandible to the intersection point of B; Through the front edge of mandibular ramus mandible to do the vertical of the inferior margin of mandible and the intersection point as a point C; Through the mental foramen to do a vertical with the inferior margin of mandible, intersecting at the point of D. The AB segment defined as posterior margin of mandible, BC segment defined as angle of mandible area and CD segment defined as inferior border of mandible. In the VR image positioning, each section were measured five points. MPR images automatically match, on MPR measured the thickness of the cortical bone at five points correspond to the inner plate, outer plate and edge, respectively. In this group we measured 60 cases of 120 lateral mandibular cortical bone thickness. SPSS10.0 statistical software were used to process the data, calculation of mean, standard deviation and coefficient of variation, bilateral mandibular cortical bone thickness did two independent samples t test. P<0.05 was considered statistically significant difference.
MPR reconstruction of the mandibular nerve canal measured from the mandible in different locations outside the board and the distance between the lower edge of the measured data were analyzed statistically.
Result:
1. The general morphology of mandibular angle The connection mode of the lower edge of mandible and post-edge have four types:single-angle turn-based (11.67%), biangle turn-based (8.33%), angel transition form (73.33%), anterior-posterior project type (6.67%); The position relation of angle of mandible with the axial plane of the mandible have three types:extraversion (11.67%), neutral (70.00%), enstrophe (18.33%).
2. Cortical bone thickness of the mandibular angle area
The exterior, interior and marginal cortical bone thickness of the left posterior border of mandible are 2.12±0.29mm,2.89±0.35mm,4.40±0.66mm; The exterior, interior and marginal cortical bone thickness of the left angle of mandible are 2.13±0.35 mm,2.91±0.35 mm,5.76±1.22 mm; The exterior, interior and marginal cortical bone thickness of the left inferior border of mandible are 2.18±0.41mm,3.01±0.42mm,4.29±0.68mm.The exterior, interior and marginal cortical bone thickness of the right posterior border of mandible are 2.14±0.25 mm,2.73±0.29mm,4.19±0.60mm; The exterior, interior and marginal cortical bone thickness of the right angle of mandible are 2.24±0.24mm,2.76±0.32mm, 5.65±1.09mm; The exterior, interior and marginal cortical bone thickness of the right inferior border of mandible are 2.40±0.39mm,2.98±0.42mm, 4.14±0.64mm. bilateral exterior cortical bone thickness of the posterior border of mandible (PE:t=4.882, P=0.000; PM:t=2.974, P=0.004), exterior cortical bone thickness of the angle of mandible (AI:t=3.394, P=0.001; AE:t=4.217, P=0.000), and interior cortical bone thickness of the inferior border of mandible (Ⅱ:t=6.540, P<0.05) have statistically significant, other part have not statistically significant.
3. The measure of the mandibular neural tube
The distance of the neural tube to the outer edge of the mandibular jaw in the third molar level is the minimum (left 4.20±1.05; right 4.27±1.00); The maximum distance between the first two molars (left 5.73±1.40 mm; right 5.58±1.38 mm); The distance of the neural tube to the lower edge of the mandibular jaw in the third molar level is the maximum (left 8.50±2.09 mm; right 8.82±2.42 mm), the smallest distance is between the First molar and second molar (left 6.98±0.72mm; right 6.87±0.91 mm)
Conclusions:
1. Multi-slice spiral CT can three-dimensional observed the posterior edge of the mandible, mandibular angle, the lower edge of shape in vivo, preoperative evaluation of mandibular angle can be quasi-morphological characteristics of the surgical plan to provide important reference information, for mandibular angle narrowing surgery has important clinical significance.
2. With Multi-slice spiral CT can precisely measure the cortical bone thickness of the back edge of the mandible, mandibular angle, the lower edge of mandibular. In the observation of bone structures at the same time can observe the soft tissue, for narrowing the mandibular angle surgery has important clinical significance. To ensure accurate implementation of the procedure, reducing operative difficulties, reduce surgical complications.
3. Multi-slice spiral CT volume scanning and three-dimensional reconstruction can be a very good display of the mandibular neural tube and its traveling direction and the relationship between the surrounding structures, for mandibular surgery to say have an important clinical significance.
Part two:Three-dimensional finite element analysis of mandible biomechanics
Objective:With the three-dimensional finite element method, a three-dimensional finite element model of mandible was constructed; the biomechanical characteristic variation of mandible after the mandibular angle osteotomy anaplasty by the means of partial resection surgery of mandibular bone was studied; a safety margin for the bone resection surgery of the mandibular angle osteotomy anaplasty was obtained; and an optimal balance point between the remodeling effect of the lower facial contour and the mechanical variation was observed.
Method:A group of healthy young female volunteers with the well-developed craniomandibular system and the class I molar relationship was selected; the temporomandibular joint region and the mandible bone were examined through serial scan and axial tomography of the 64-slice spiral CT; the Mimics12.0 and the Ansys12.0 software were used for segmentation, smoothing processing and three-dimensional mesh generation according to the experimental requirement;with the addition of parameter setting for material mechanics and the boundary constraint design, a three-dimensional finite element model (control group) of a normal mandible with the muscle and ligament constraint for the mandible without the lower teeth was constructed. On the basis of the three-dimensional finite element model (control group), a model 1 with the resection of mandibular margin and a model 2 with the partial resection of mandible were constructed respectively (experimental group); an impact response curve was added at the corresponding point on the stress surface of the lower edge of the symphysis; the mandible stress nephogram and the dynamic stress variation nephogram of the mandible in the control group and the experimental group were calculated through the Ansys12.0 software. Three points were chosen at the mandible condyle, the mandibular body and the junction between the horizontal branch and the mandibular ramus; the stress-time load response curves of the three points were calculated through the software; and the stress data of each point with a 1ms time interval unit during the stress conduction process and the maximal stress of the points were extracted. Afterwards, the model 1 and the model 2 were introduced into the Ansys12.0 software respectively; the above solving steps were repeated; and the stress nephogram, the dynamic stress variation nephogram and the time-stress load response curve for the control group and the experimental group and the stress data of the above three points were calculated.
Result:
1. A three-dimensional finite element model of the normal mandible with muscle and ligament constraint, a model 1 and a model 2 were constructed.
2. The stress distribution on the whole model of the mandible
The impact stress began to spread around 1.8ms after the mentum impact and the stress mainly conducted along the external oblique direction and concentrated at the mandible condyle. After the stress on the concentration part of the anterior，internal side of the mandible condyle reached the summit of the stress 12.5ms after the impact, the stress on the mandible was in a downward status and disappeared gradually. In the whole process, the posterior edge of the mandible, the mandibular angle area and the lower edge which was close to the mandibular angle area mentioned in the former part of the study were always in a less stress state.
3. The stress distribution of the mandible model 1 of the experimental group
The stress conduction and distribution of the model were similar to the normal mandible; however, the scope and the intensity of the stress on the mandible were reduced apparently. Compared with the nephogram of the normal mandible, the color intensity of the nephogram of model 1 was weakened and the similar color area became smaller. After 11～12.5ms the addition of the impact load, the color of the surrounding area of the sigmoid incisure of mandible, coracoid process and alveolar ridge turned from less stress blue into more stress yellow when compared with the normal mandible.
4. The stress distribution of the mandible model 2 of the experimental group
The stress conduction and distribution of the model were similar to the mandible model 1; however, the scope and the intensity of the stress on the mandible were reduced furtherly. Compared with the nephogram of the normal mandible, the color intensity of the nephogram of model 1 was weakened and the similar color area became smaller. After 11～12.5ms the addition of the impact load, the yellow color intensity of the surrounding area of the moid notch of the mandible, coracoid process and alveolar ridge became stronger when compared with the mandible model 1. The result shows that the stress in this area was increased furtherly.
5. The time-stress curves of the mandible condyle, the point at the junction between the horizontal branch and the mandibular ramus and the mandibular body
The curve morphology of the mandible condyle, the point at the junction between the horizontal branch and the mandibular ramus and the mandibular body of each model are almost identical. However, there is difference in the summit value and the waveform before the disappearance of the stress. The maximal variation of the summit value appears at A point; two apparent rebound waves exist in mandible model 2. The rebound wave of the mandible model 1 before the disappearance of the stress at B point is not obvious; however, there is rebound wave in mandible model 2. There is no rebound wave in the mandible model before the disappearance of the stress at C point; however, the rebound wave of the mandible model 1 is not obvious; there are two apparent rebound waves in mandible model 2.
6. Statistical analysis for the stress at A point of the mandible condyle, B point at the junction between the horizontal branch and the mandibular ramus and C point of the mandibular body
With the anova analysis, the variance of the stress at different sites of the three groups are irregular (a:F=3.174, P< 0.05; b:F=29.204, P=0.000; c:F=20.051, P=0.000); the multiple comparison among different groups is conducted through using the Dennetts method. The result shows that there is no statistical difference among three groups at A point(P> 0.05); there is statistical difference between the normal mandible group and the model 1 and the model 2 at B point (P< 0.05); there is no statistical difference between the model 1 and the model 2 at B point (P> 0.05); there is statistical difference between the normal mandible group and the model 1 at C point (P< 0.05); and there is no statistical difference between the normal mandible group and the model 2 at C point (P> 0.05).
Conclusion:
1. After the impact of the mandible, the stress was mainly conducted along the external oblique direction and concentrated at the mandible condyle.
2. The resection of the posterior edge of the mandible,the mandibular angle and the lower edge of the mandible can cause the elevation of the stress in the surrounding area of the sigmoid incisure of mandible, coracoid process and alveolar ridge.
3. The more bone was excised, the more stress was increased and the more fragile the mandible became.
Part three:The clinical experience of Mandibular angle osteotomy plastic surgery and the clinical applied research of Multi-slice computed tomography on Mandibular angle osteotomy plastic surgery
Objective:Evaluation the clinical features of patients with mandibular angle osteotomy plastic surgery and the results of operation, meanwhile to observe the clinicalapplication value of multi-slice computed tomography.
Methods:Since October 2007 to November 2009, Total completion 119 cases of the mandibular angle osteotomy plastic surgery, all patients underwent preoperative general examination and X-ray examination. In this group there have 119 cases, among of which there have 115 female (229 sides),4 cases men (7 sides).19 to 43 years of age and with a mean age 28.3 years. All patients maxillofacial region growth normally, occluding relation normal and have no occlusion barrier, have no sings and symptoms of temporomandibular joint disturbance syndrome, have no history of mandibular operation and trauma. The hypertrophy of mandibular angle to the main bone hypertrophy, Showed as prominent mandibular angle bone hyperplasia and Mandibular angle spacing widened. Among of which there have 25 cases undergone zygoma diminutionplasty,6 cases undergone prosthesis chin augmentation.
In this group there have 21 cases have preoperative three-dimensional reconstruction and preoperative simulation, among of which there have 7 cases undergone postoperative three-dimensional reconstruction from 1 week to 12 weeks after the operation. Spiral CT scanning method and reconstruction method just like part one.
To make use of Mirror system software, loading the three dimensional picture of mandible, use the stretching, panning, cutting, rotation, stitching and expanding functions of the software, based on the standards of the ministry of bone in past reported literature the following outline of the aesthetic, and made reference to the request of the patients, as well as with combined features, form a combination of factors and then simulate the effect of surgical treatment of the bone, after that make a comparison with postoperation three-dimensional reconstruction.
Result:
In patients with large mandibular angle with zygomatic distance of 131.2mm; the preoperation distance between mandibular angle is 116.5mm and postoperation distance is 101.8mm, Than preoperation shrunk 14.7mm. Preoperative lateral angle of the mandibular angle is 114.1°, and postoperation is 126.2°.
There have 93 patients being followed up about 3 months in 119 patient's undergone operation, there have 88 cases the surgeon and patients consider significant improvement in facial contour and have satisfactory result, accounted for 73.95% of all cases.57 cases followed up about for 6 months and among of which 56 patients get satisfactory result, accounted for 47.06% of all cases.
Conclusions:
1. The mandibular angle osteotomy plastic surgery of the mandibular angle has a good effect, Learn more about preoperative patient characteristics of bone structure help increase the success rate of surgery and reduce the incidence of complications.
2. Spiral CT in the preoperative mandibular angle osteotomy and plastic surgery can help determine the surgical plan, simulate the operation and evaluate the results of operations.
3. The osteotomy line and the way of the bone process should dicided by the typing and classification of the mandibular angle.
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