Fixation methods in sagittal split ramus osteotomy: a systematic review on in vitro biomechanical assessments

The aim of this systematic review was to assess the stability of rigid internal fixation (RIF) techniques in sagittal split ramus osteotomy (SSRO) based on in vitro biomechanical assessments, with particular interest in large mandibular advancements. In general, RIF methods can be divided into three groups: bicortical screws, miniplates, and a combination of the two. An electronic search of the PubMed, CINAHL, and Embase databases was performed, and studies published between January 2003 and March 2018 were screened for inclusion. Comparative studies with an in vitro experimental design, using biomechanical assessments to measure the stability of RIF methods in SSRO, were included. Of 104 unique studies identified in the initial search, 24 were included. Twenty-two of these 24 studies analyzed an advancement of the mandible of 7 mm or less. The use of a single four-hole or six-hole miniplate was less stable than the use of bicortical screws, hybrid techniques, double miniplates, or grid plates. Two studies analyzed advancements of 10 mm, for which two miniplates placed in parallel and a grid plate showed most stability. Although there was agreement between studies with regard to results, more biomechanical studies are required to quantify the stability of fixation methods in larger mandibular advancements.     

下颌发育过度外科矫治术式的选择

下颌发育过度是临床常见的一种牙颌面畸形,下颌支垂直骨切开术和下颌支矢状骨劈开术是用来矫治这种骨性Ⅲ类错(牙合)的常用术式。本文对这两种手术方法的优缺点进行比较与讨论,从而为下颌前突外科矫正术式的合理选择提供参考。     

Computed tomography morphology of the mandibular ramus at the lingual plane in patients with mandibular hyperplasia

This study investigated the specific morphology of the mandibular ramus at the lingual plane in patients with mandibular hyperplasia using spiral computed tomography. The subjects were 25 patients with mandibular hyperplasia undergoing sagittal split ramus osteotomy and there were 20 patients without dentofacial deformities in the control group. The thickness of the mandible, diameter of the inner mandibular canal, width of the buccal bone marrow space, and the width of the buccal cortex and lingual cortex were measured at the lingual plane, which contained the lowest point of the mandibular foramen. The average thickness of the mandible was 8.5 mm in prognathic patients and 9.6 mm in control patients. The average width of the buccal bone marrow space in mandibular hyperplasia patients was 1.5 mm and 2.5 mm in control patients. The mandibular ramus in patients with mandibular hyperplasia was thinner and the width of the buccal bone marrow space was smaller than in the control patients. The width of the buccal bone marrow space and the thickness of the mandible were significantly positively correlated.     

下颌支矢状劈开术与下颌管位置关系的应用解剖学研究

目的研究下颌管在下颌骨内的重要行径和位置关系。方法选用带软组织50具完整的头颈标本,分别在下颌第三磨牙后缘的垂直线、磨牙后三角尖至下颌角连线呈额状位锯开下颌骨,观察下颌管的解剖。结果下颌管是下颌骨的骨松质内形成较薄的骨密质骨管。下颌管在下颌骨第三磨牙后缘切面的位置靠内侧型占90%,中间型占10%;在连线切面的位置靠内侧型占84%,中间型占16%。结论了解下颌管在下颌骨内的重要毗邻关系,可以减少因下牙槽神经损伤造成口裂以下粘膜和皮肤的感觉障碍。     

Stability of fixation methods in large mandibular advancements after sagittal split ramus osteotomy: an in vitro biomechanical study

Sagittal split ramus osteotomy (SSRO) with large mandibular advancements is a common surgical procedure and could be indicated for patients with sleep apnoea. As a large variety of fixation methods is used for the stabilisation of SSRO, a biomechanical test model was used to analyse which fixation technique was most stable. For this in vitro study, 80 polyurethane hemimandibles with a prefabricated SSRO were used as substrates. Loads in Newtons were recorded at displacements of the mandibular incisive edge at 1 mm, 3 mm and 5 mm. The samples were divided into two groups: mandibular advancements of 10 mm and 15 mm. In both groups, four fixation techniques were used: (A) one four-hole miniplate; (B) two four-hole miniplates; (C) one four-hole miniplate plus one bicortical screw; and (D) three bicortical screws in an inverted-L arrangement. In group 1, three bicortical screws resulted in the best stability, and in group 2, two miniplates resulted in the best stability. The use of two miniplates did not show significant differences between both groups. Other fixation methods showed more stability with 10 mm advancements. This study therefore suggests that in SSRO with advancements exceeding 10 mm, the use of two miniplates is the optimal means of providing rigid fixation.     

Use of a ‘low and short’ medial cut limits sagittal ramus osteotomy interferences

The traditional ‘high and short’ medial cut of the sagittal ramus osteotomy (Hunsuck modification) is a frequent cause of lingual plate interferences in patients undergoing mandibular yaw or cant corrections. We describe how the modified ‘low and short’ medial cut of the sagittal ramus osteotomy reduces lingual plate interferences with improved passive alignment of the osteotomy segments.     

下颌升支截骨手术相关下颌管解剖标志的多层CT测量研究

目的:应用多层CT影像测量下颌骨与升支矢状劈开截骨手术相关下颌管骨性解剖标志,为避免手术中损伤下齿槽神经血管提供指导。方法:选择60名正常成人下颌骨多层CT扫描图像,应用efilm1.94图像处理软件分别在第二磨牙远中的垂直线,磨牙后三角尖至下颌角连线及下颌孔下5 mm处取下颌骨断面,测量下颌管的解剖位置。结果:下颌管在下颌第二磨牙远中断面距颊侧骨面的距离为6.26±4.34 mm;在磨牙后三角尖至下颌角连线断面距颊侧骨面的距离为5.18±2.12 mm;在下颌孔下5 mm断面距颊侧骨面的距离为4.44±2.38 mm。结论:参照测量获得的解剖数据在术中能降低下齿槽神经血管损伤的发生率。     

Surgical morbidities of sagittal split ramus osteotomy versus intraoral vertical ramus osteotomy for the correction of mandibular prognathism: a randomized clinical trial

The sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) are two common orthognathic procedures for the treatment of mandibular prognathism. This randomized clinical trial compared the surgical morbidities between SSRO and IVRO for patients with mandibular prognathism over the first 2 years postoperative. Ninety-eight patients (40 male, 58 female) with a mean age of 24.4 ± 3.5 years underwent bilateral SSRO (98 sides) or IVRO (98 sides) as part or all of their orthognathic surgery. IVRO presented less short-term and long-term surgical morbidity in general. The SSRO group had a greater incidence of inferior alveolar nerve deficit at all follow-up time points (P <  0.01). There was more TMJ pain at 6 weeks (P =  0.047) and 3 months (P =  0.001) postoperative in the SSRO group. The SSRO group also presented more minor complications, which were related to titanium plate exposure and infection. There were no major complications for either technique in this study. Despite the need for intermaxillary fixation, IVRO appears to be associated with less surgical morbidity than SSRO when performed as a mandibular setback procedure to treat mandibular prognathism.     

In vitro study of a modified sagittal split osteotomy fixation technique of the mandible: a mechanical test

This study was performed to evaluate the compressive mechanical strength of rigid internal fixation (RIF) using 1.5-mm L-shaped plates fixed with monocortical screws in sagittal split osteotomy (SSO). Thirty synthetic hemimandibles, which had all undergone a 5-mm advancement, were divided into three groups: three 12-mm bicortical titanium screws were placed in an inverted L pattern in group A; one straight 2.0-mm system spaced titanium plate fixed with four 5-mm monocortical screws was used in group B; two 1.5-mm system L-shaped titanium plates, each fixed with four 5-mm monocortical screws, were used in group C. The models were subjected to compressive and progressive mechanical tests with forces applied in the area between the second premolar and first molar to verify resistance in Newtons (N). A displacement speed of 1 mm/min was applied, with a maximum 10 mm displacement of the distal segment or until disruption of the fixation. The deformity and/or eventual rupture of the plates were evaluated, and consequently their technical stability was determined. The results showed that the modified fixation technique tested in this study on synthetic mandibles resulted in adequate stability and superior mechanical behaviour compared to simulated osteosynthesis with the use of a straight 2.0-mm titanium plate.     

Stability after sagittal split ramus osteotomy without post-operative maxillomandibular fixation in the treatment of prognathic patients with asymmetric mandibles

This study was designed to examine the post-operative stability in prognathic patients with mandibular asymmetry, who underwent sagittal split ramus osteotomy (SSRO) of the mandible and titanium screw fixation without post-operative maxillomandibular fixation (MMF). Twenty prognathic patients were examined. An appliance for repositioning the proximal segment was applied during surgery in all patients. Ten patients with symmetric mandibles underwent post-operative MMF with stainless steel wire and intermaxillary rubber traction after removal of MMF (Group I), and the other 10 patients with asymmetric mandibles received only intermaxillary rubber traction post-operatively (Group II). Posteroanterior cephalograms were obtained pre-operatively; 2–3 days post-operatively; and 3, 6, and 12 months after surgery. Changes in the positions of the gonion points (Go) and upper and lower incisors (U-1 and L-1) were examined. In both groups, the Go tended to shift laterally, as a consequence of the operation. Although the tendencies of the post-operative changes in (Go) points of Groups I and II were different, statistical analyses revealed no differences between the two groups. At the late stage of follow-up, the absolute value of the change in L-1 tended to be larger in Group II than in Group I, but without statistical significance. This study suggests that post-operative change in prognathic patients with asymmetric mandibles treated without post-operative MMF is comparable to that in patients with symmetric mandibles treated with post-operative MMF. Therefore, post-operative MMF might be avoided, even in prognathic patients with asymmetric mandibles.     

下颌管定位与下颌支矢状骨劈开术后感觉神经障碍相关性的临床观察

目的 用CT扫描来确定下颌前突患者下颌支部下颌管的定位,并评价下颌管与颊侧骨皮质之间骨髓腔宽度与术后感觉神经障碍(NSD)之间的关系。方法 把通过下颌管最先形成的平面作为基础平面1,紧邻下颌第二磨牙远中与平面1相垂直作为平面5,二者角分线为平面3,平面1和3,3和5的角分线分别为平面2和4,共5个平面,在每一平面测量颊侧骨髓腔的宽度。以问卷的形式描述术后下牙槽神经分布区域的感觉改变。测量结果 采用SPSS13.0软件包进行统计学分析。用卡方检验评价骨髓腔宽度和术后NSD之间的关系。结果 颊侧骨髓腔宽度左右两侧无显著性差异(t=-0.871,P=0.384),其宽度的总体变化没有规律,在3、4层面距离最小,各层之间差异有显著性(F=2.795,P=0.017)。颊侧骨髓腔缺如(接触和融合型),在3和4层面出现几率较高。颊侧骨髓腔宽度为0的27侧100%发生术后NSD。未接触组63侧有14.3%发生术后NSD,两组间差异有显著性(χ2=25.941,P<0.05)。结论 颊侧骨髓腔的宽度是术后NSD的风险因子,当下颌管和颊侧骨皮质之间的骨髓腔宽度是0.9mm或更小时,NSD更容易发生,当颊侧骨髓腔缺失时,从外侧骨皮质中分离下牙槽神经十分困难。     

Position of the mandibular canal before and after bilateral sagittal split ramus osteotomy: a cone beam computed tomographic study

The aim of this study was to evaluate the position of the mandibular canal (MC) before and after bilateral sagittal split ramus osteotomy (BSSRO) using cone-beam computed tomography (CT), and to compare the position of the MC in Class II and Class III patients in the preoperative period. Patients were divided into two groups: Class II (n = 38) and Class III (n = 41). Measurements of the superior, inferior, buccal, and lingual distances of the MC in relation to the cortical bone were taken at three levels in the proximal segment of the mandible. Results were analysed using the Kruskal–Wallis test (p < 0.05). In the Class II group the superior distance of the MC at levels 2 and 3, and the inferior distance at level 3 significantly decreased after BSSRO. In the Class III group, no significant differences were found at any level, and the inferior distances at all levels were smaller preoperatively than those in the Class II group. In the Class II group the position of the MC altered in relation to superior and inferior cortical bone after BSSRO. However, the position of the MC remained stable in the Class III group. Our results also suggest a deeper cut in inferior cortical bone in Class III patients.     

下颌矢状劈开截骨术相关下颌管空间定位的三维CT研究

目的：应用三维CT影像测量下颌管解剖位置与骨皮质和磨牙的关系,为避免下颌矢状劈开截骨术中损伤下齿槽神经血管提供指导。方法：选择50名正常成人下颌骨三维CT扫描图像,应用AW4．4图像处理软件分别在第二前磨牙,第一、第二磨牙正中,下颌磨牙后区处测量下颌管的解剖位置。结果：通过获得的CT数据研究中国人下颌神经管的解剖位置与骨皮质和磨牙的联系,在第二磨牙区域下颌管距离颊侧骨皮质最远（平均7．82mm,最小4．9mm）。结论：在第二磨牙区域下颌体最厚,对于下颌矢状劈开截骨术的颊侧垂直切口须在下颌第二磨牙区域,这个区域骨质最厚并且下颌管距离颊侧骨皮质最远。对于下颌矢状劈开截骨术颊侧垂直切口的安全深度是4．9mm。     

Comparison of osseous healing after sagittal split ramus osteotomy and intraoral vertical ramus osteotomy

The sagittal split ramus osteotomy (SSRO) is generally associated with greater postoperative stability than the intraoral vertical ramus osteotomy (IVRO); however, it entails a risk of inferior alveolar nerve damage. In contrast, IVRO has the disadvantages of slow postoperative osseous healing and projection of the antegonial notch, but inferior alveolar nerve damage is believed to be less likely. The purposes of this study were to compare the osseous healing processes associated with SSRO and IVRO and to investigate changes in mandibular width after IVRO in 29 patients undergoing mandibular setback. On computed tomography images, osseous healing was similar in patients undergoing SSRO and IVRO at 1 year after surgery. Projection of the antegonial notch occurred after IVRO, but returned to the preoperative state within 1 year. The results of the study indicate that IVRO is equivalent to SSRO with regard to both bone healing and morphological recovery of the mandible.     

下颌骨矢状劈开后退术对咽腔间隙及舌骨位置的影响

目的 :CBCT测量分析下颌后退手术治疗下颌前突畸形,对舌骨位置和气道间隙变化的影响。方法 :选取单纯下颌前突畸形患者50例为研究对象,均接受经口内下颌骨升支矢状劈开截骨术,于正颌手术前1周、术后2周、术后6个月拍摄锥形束CT,测量治疗前后咽腔最窄处的矢状径、冠状径、截面积,同时舌骨点的三维位置,分析咽腔间隙大小及及舌骨体位置变化。测量数值配对t检验。结果:所有患者术后咽腔间隙均呈现缩窄趋势。舌骨发生了后下移位,其中术后2周向后、向下平均移动距离分别为2.64、1.56 mm,术后6月向后、向下移位分别为0.97、0.99 mm。术后2周咽腔的矢状径、冠状径及咽腔间隙分别为11.71 mm、3.05 mm、320.67 mm~2,术后6月时分别为14.64 mm、3.23 mm、414.85 mm~2。即随时间推移,舌骨位置及咽腔间隙有恢复正常范围的趋势。结论:双侧下颌骨升支矢状劈开截骨后退术后,舌骨向后下移位,咽腔气道缩小,有可能导致睡眠呼吸暂停综合征的发生,临床需予以重视。     

双侧下颌升支矢状劈开截骨后退术对下颌骨宽度及形态的影响

目的通过对下颌前突患者行双侧下颌升支矢状劈开截骨后退术前后头颅正侧位定位片硬组织结构变化的洲量分析,评价手术对患者下颌骨宽度及形态的影响。方法选择1997年至2001年在我中心行双侧下颌升支矢状劈开术的下颌前突患者18例,男性9例,女性9例,平均年龄22．22岁,所有患者手术前、术后一周、术后一年拍摄静止位头颅正侧位定位片,在正位片上测量下颌骨宽度(Go-Go),并从头颅正侧位定位片上测量与下颌骨宽度变化有关的参数数值。结果①下颌骨宽度由107．30mm±5．84mm(术前)增加至109．24mm±5．72mm(术后一周)、109．31mm±5．66mm(术后一年),其中有4例宽度减小,1例保持不变。13例增加,②下颌骨宽度术前、术后一用、术后一年的方差分析结果表明差别有显著性。③分析表明下颌骨宽度变化与各参数变化之间没有线性相关。结论①下颌骨宽度在双侧下颌升支矢状劈开截骨术后较术前有轻微增大,但对容貌没有大的影响。②下颌骨宽度变化机制可能与颞下颌关节功能改变有关。     

下颌升支矢状劈开术后正畸快速建立咬合关系的研究

目的:探讨快速建立下颌升支矢状劈开术后患者咬合关系的方法。方法:37例术前未做正畸治疗的下颌前突患者,下颌升支矢状劈开术后第2日即开始用固定矫治器快速正畸,利用带钩方丝托槽行颌间牵引建立咬合。结果:3～7个月内患者基本上建立正常的咬合关系,恢复咬合功能。结论:!下颌前突患者行下颌升支矢状劈开术后立即开始正畸治疗可以快速建立咬合关系。