Hybrid fixation in the bilateral sagittal split osteotomy for lower jaw advancement

Miniplate and screw fixation has been widely used in bilateral sagittal splitosteotomy, but some issues remain unclear concerning its lack of rigidity whencompared to Spiessl''s bicortical technique. This paper demonstrates the hybridfixation technique in a case report. A 34-year-old female patient underwent a doublejaw surgery with counter-clockwise rotation of the mandible fixed using the hybridfixation technique. The patient evolved well in the postoperative period and is stillunder follow up after 14 months, reporting satisfaction with the results and nosignificant deviation from the treatment plan up to now. No damage to tooth roots wasdone, maxillomandibular range of motion was within normality and regression of theinferior alveolar nerve paresthesia was observed bilaterally. The hybrid mandibularfixation is clearly visible in the panoramic and cephalometric control radiographs.It seems that the hybrid fixation can sum the advantages of both monocortical andbicortical techniques in lower jaw advancement, increasing fixation stability withoutsignificant damage to the mandibular articulation and the inferior alveolar nerve. Astatistical investigation seems necessary to prove its efficacy.     

Biomechanical evaluation of hybrid fixation method of sagittal split ramus osteotomy in mandibular advancement

Purpose

In this study, eight different fixation methods applied after sagittal split ramus osteotomy (SSRO) were compared experimentally.

双侧升支矢状劈开截骨后退下颌术后骨的稳定性的研究

目的：探讨双侧升支矢状劈开截骨术（BSSRO）后退下颌骨以钢丝结扎固定两骨段加颌间固定术后骨的稳定性，了解导致复发的有关因素。方法：双侧下颌升支矢状劈开截骨手术后退下颌的患者14例，于手术前1周，手术后1周，术后6个月分别拍摄定位头颅侧位片及许勒位X线片，用于测量下颌移动的距离及确定下颌骨髁状突的位置。结果：双侧下颌升支矢状劈开截骨后退术后，6个月的复发率为27.2%，多元逐步回归分析示下颌后退的距离与复发相关。结论：BSSRO后退下颌骨的距离越大，术后下颌骨向前移位的可能越大。     

Closure of the anterior open bite using mandibular sagittal split osteotomy

Anterior open bite is a common problem in orthognathic practice that confers functional and aesthetic handicaps on affected patients. Its management varies, and it is one of the most challenging disorders to treat. The orthodontic and surgical approach to the treatment of skeletal anterior open bite is still debated, and the results are controversial. The relapse rate is high with all the techniques in current use. The cause of relapse is multifactorial and one of the main factors is the type of osteotomy used. Over the last 30 years preference has moved from mandibular sagittal split osteotomy (MSSO) alone, to maxillary procedures only, or to bimaxillary operations, with maxillary procedures alone being thought to confer the best stability and predictability. The aim of this study was to evaluate the results of correction of anterior open bite with the MSSO immediately after operation, and 1 year postoperatively.     

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。     

下颌骨双侧升支矢状劈开双皮质螺钉内固定的生物力学分析

目的:对下颌骨升支矢状劈开不同方式双皮质固位螺钉内固定进行三维有限元分析,为临床提供理论指导。方法:建立下颌骨升支矢状劈开6种双皮质螺钉固定方式的三维有限元模型;计算不同固定方法在3种咬合情况下颌骨的应力、内固定系统的应力以及骨劈开处的位移,对比这些固定方式的固定效果以及不同咬合情况对固定稳定性的影响。结果:在相同咬合情况下,颌骨的应力、内固定系统的应力以及劈开处的位移的大小情况如下:单纯上缘固定大于倒"L"型固定;直径2.0mm大于直径2.7mm螺钉固定;倒"L"型60°大于倒"L"型90°和120°固定;间距2.0cm大于间距3.0cm固定。相同固定方式情况下,颌骨的应力、内固定系统的应力以及劈开处的位移从大到小排列顺序为:前牙咬合、前磨牙咬合、磨牙咬合。结论:双皮质固位螺钉内固定的排列方式,如:间距、角度、位置和内固定系统的规格均对固定稳定性有不同程度的影响;前牙咬合对固定的不良影响最大,应尽量避免。     

Independent risk factors for long-term skeletal relapse after mandibular advancement with bilateral sagittal split osteotomy

The purpose of this retrospective cohort study was to identify the independent risk factors for long-term skeletal relapse following mandibular advancement with bilateral sagittal split osteotomy. Univariate and multivariate linear regression analyses were performed including nine common risk factors for relapse as independent variables and horizontal/vertical long-term (≥2 years) skeletal relapse as dependent variables. Ninety-six patients were analyzed; 66 were female (68.8%) and the average age of the patients was 29.7 ± 10.5 years. Over an average follow-up of 3.8 ± 1.8 years after an initial mandibular advancement of 8.8 ± 2.4 mm, long-term skeletal relapse of 1.6 ± 1.0 mm horizontal and 0.9 ± 0.7 mm vertical was found. Multivariate analysis identified age, preoperative mandibular plane angle (MPA), bimaxillary surgery, counterclockwise mandibular rotation, and the magnitude of mandibular advancement to be significantly associated with horizontal long-term skeletal relapse. Preoperative MPA, counterclockwise mandibular rotation, and the magnitude of mandibular advancement were significantly associated with vertical long-term skeletal relapse. Thus preoperative MPA, the magnitude of mandibular advancement, and counterclockwise mandibular rotation of the mandible were found to be independent risk factors for both horizontal and vertical long-term skeletal relapse. Although long-term skeletal relapse cannot be avoided entirely, understanding the independent risk factors and their contributions will optimize treatment planning and long-term stability.     

In vitro comparison of 1.5 mm vs. 2.0 mm screws for fixation in the sagittal split osteotomy

Purpose

Numerous “in vitro” investigations have been conducted to evaluate the role of screw size and pattern in determining optimal resistance to deformation, often these have been controversial. The aim of this study was to evaluate the effect of screw size and insertion technique on the stability of sagittal split osteotomies.

Materials and methods

This study used twenty polyurethane replicas of human hemimandibles with a prefabricated sagittal split ramus osteotomy (SSRO). The hemimandibles were stabilized with 1.5 mm and 2.0 mm titanium screws inserted in an inverted L configuration. All specimens were tested to determine the strength and stability of the fixation.

Results

In all cases there was failure of the synthetic bone before there was any evidence of screw failure. There were no significant differences in the load necessary to make the construct fail between the 1.5 or 2.0 mm screw sizes.

Conclusion

There was no statistically significant difference between the strengths achieved with screws of 1.5 and 2.0 mm diameters for fixation of SSRO performed in synthetic mandibles. There was no fracture of the 1.5 mm or 2.0 mm diameter screws in any of the tests. 1.5 mm diameter screws in an inverted L pattern have as much stability and mechanical resistance as a 2.0 mm screw, may be safely used for this procedure.     

下颌前突患者下颌支矢状劈开截骨术后髁突运动轨迹的改变

目的:研究双侧下颌支矢状劈开截骨术对下颌前突患者髁突运动轨迹的影响。方法:采用ARCUSdigma下颌三维运动轨迹描记仪,以髁突运动中心为参考点,研究30例正常受试者、14例下颌前突患者手术前后开口、前伸和左右侧向髁突运动的轨迹。用SPSSV11.0统计软件包进行配对t检验和成组t检验。结果:下颌前突患者术前、术后、正常组左侧髁突的运动轨迹与右侧基本相同,左侧髁突与右侧的开口、前伸和侧方运动范围无显著性差异(P>0.05)。术前组与正常组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均小于正常组(P<0.05);术后与正常组髁突运动轨迹接近,术后开口、前伸和侧方运动范围与正常组无统计学差异;术前与术后组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均显著小于术后组(P<0.05)。结论:下颌前突患者手术后,随着术后正畸治疗及咬合自我调整,建立了正常的咬合引导关系,使下颌功能运动趋向正常。     

Interaction analysis of risk factors for long-term skeletal relapse following mandibular advancement with bilateral sagittal split osteotomy

The aim of this study was to identify interaction effects among risk factors for long-term skeletal relapse. The study sample consisted of 96 patients who underwent mandibular advancement with bilateral sagittal split osteotomy. Ten predictor variables were analyzed for an interaction effect: sex, age, preoperative temporomandibular joint symptoms, mandibular plane angle (MPA), single or double jaw surgery, clockwise or counterclockwise mandibular rotation, magnitude of mandibular advancement, concomitant genioplasty, type of fixation, and follow-up duration. Modeling interactions between pairs of covariates were applied to detect a significant interaction among these risk factors on horizontal and vertical long-term skeletal relapse, respectively. Stratification analyses and two-way full factorial interaction analyses were performed to demonstrate how the interaction influenced the associations between covariates and relapse. The interactions between sex and mandibular rotation (P = 0.006) and between MPA and mandibular rotation (P = 0.002) were statistically significant for horizontal long-term skeletal relapse. No significant interaction was identified for vertical relapse. This study showed that female patients and those with an MPA ≥30° undergoing counterclockwise mandibular rotation are predisposed to greater horizontal long-term skeletal relapse. Therefore, the judicious use of counterclockwise rotation is recommended in order to minimize the relapse, especially in female patients and those with a high MPA.     

Penetration of inferior alveolar nerve canal increased by bicortical fixation after bilateral sagittal split osteotomy in mandibular prognathism

The purpose of this three-dimensional cone beam computed tomography (CBCT) study was to identify the difference between monocortical fixation (MCF) and bicortical fixation (BCF) in mandibular canal penetration after bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism, where interosseous fixation was done by BCF or MCF. CBCT was performed 1 week postoperatively and Dolphin 3D software was used to assess direct penetration of the mandibular canal by either type of screw. The primary outcome variable was the presence or absence of mandibular canal penetration and was categorized as a binary coded variable. The BCF and MCF groups were compared by χ² test, and the odds ratio for canal penetration was estimated. Multiple logistic regression was performed to identify factors related to canal penetration. A total of 118 patients were included. The MCF group had only 6% canal penetrations (3/50 patients) and the BCF group had 58.8% canal penetrations (40/68 patients). The regression model showed that BCF was the only factor causing mandibular canal penetration, with an adjusted odds ratio of 52.5. Awareness of the increased risk of canal penetration with BCF and potential nerve injury might influence case selection.     

与下颌升支矢状劈开截骨相关的下颌管解剖研究

目的 研究下颌管在下颌骨内的走行和位置关系，为下颌升支矢状劈开截骨手术提供指导。方法 选用30具完整的干燥下颌骨标本，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3mm呈冠状锯开下颌骨，观察测量下颌管的解剖位置。结果 下颌管是下颌骨睁骨松质内较薄的骨密质骨管。下颌管在下颌第二磨牙后缘切面的位置靠内侧型占87％，中间型占13％；在连线切面的住置内侧型占92％，中间型占8％；在下颌孔下3mm平面内侧型占98％，外侧型占2％。越接近下颌孔，烦侧骨皮质越厚。结论 了解下颌管在下颌骨内的位置及比邻关系，可避免下颌升支矢状劈开截骨中下齿槽神经血管束的损伤。     

下颌骨矢状劈开后退术对颞下颌关节的影响

目的:评价下颌骨矢状劈开后退术对颞下颌关节(TMJ)的影响.方法:研究我院50 例术前有颞下颌关节病(TMD),且行下颌骨矢状劈开后退术的患者,从关节压痛、弹响、张口度、张口型等方面量化评估术前、术后颞下颌关节症状变化情况.结果:从关节压痛、弹响、张口度、张口型等各方面评估均显示术后颞下颌关节症状评分均显著低于术前(P<0.05).结论:对于术前有颞下颌关节病的患者,行下颌骨矢状劈开后退术可以有效改善颞下颌关节症状.     

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。     

Bad split during bilateral sagittal split osteotomy of the mandible with separators: a retrospective study of 427 patients

An unfavourable fracture, known as a bad split, is a common operative complication in bilateral sagittal split osteotomy (BSSO). The reported incidence ranges from 0.5 to 5.5%/site. Since 1994 we have used sagittal splitters and separators instead of chisels for BSSO in our clinic in an attempt to prevent postoperative hypoaesthesia. Theoretically an increased percentage of bad splits could be expected with this technique. In this retrospective study we aimed to find out the incidence of bad splits associated with BSSO done with splitters and separators. We also assessed the risk factors for bad splits. The study group comprised 427 consecutive patients among whom the incidence of bad splits was 2.0%/site, which is well within the reported range. The only predictive factor for a bad split was the removal of third molars at the same time as BSSO. There was no significant association between bad splits and age, sex, class of occlusion, or the experience of the surgeon. We think that doing a BSSO with splitters and separators instead of chisels does not increase the risk of a bad split, and is therefore safe with predictable results.     

Stability of mandibular advancement procedures: bilateral sagittal split osteotomy versus distraction osteogenesis

The aim of this study was to compare the postoperative stability of the mandible after a bilateral lengthening procedure, either by bilateral sagittal split osteotomy (BSSO) or distraction osteogenesis (DOG). All patients who underwent mandibular advancement surgery between March 2001 and June 2004 were evaluated; 26 patients in the BSSO group and 27 patients in the DOG group were included. The decision to use the intraoral distraction or BSSO for mandibular advancement primarily depended on the patient's choice. In both groups, standardized cephalometric radiographs were taken preoperatively, postoperatively (BSSO group) or directly post-distraction (DOG group) and during the last study measurement in May 2005. The cephalometric analysis was performed using the following measurements: Sella/Nasion-Mandibular point B and Sella/Nasion-Mandibular Plane. Point B was used to estimate relapse. This study showed no significant difference in relapse between the BSSO and the DOG group measured 10-49 months after advancement of the mandible (p>0.05). There is no postoperative difference in the stability between BSSO and DOG after mandibular advancement after 1 year.     

Unusual cause of iatrogenic anterior open bite after bilateral sagittal split mandibular advancement osteotomy

We describe a case of anterior open bite after bilateral sagittal split mandibular advancement osteotomy. The discrepancy in height between the proximal and distal segments at the osteotomy sites damaged the soft tissue and caused bony interferences. Removal of the maxillary third molars and bilateral removal of bony interferences of the distal segments using a bur led to full resolution and a good orthognathic outcome on follow-up.     

Long-term stability of mandibular advancement with bilateral sagittal split osteotomy

Introduction

Aim of this study was 1) to evaluate long-term dental/skeletal stability in patients with mandibular retrognathia corrected by BSSO, and 2) to examine factors associated with relapse.

Removal of bicortical screws and other osteosynthesis material that caused symptoms after bilateral sagittal split osteotomy: a retrospective study of 251 patients,and review of published papers

Rigid fixation with either bicortical screws or miniplates is the current standard way to stabilise the mandibular segments after bilateral sagittal split osteotomy (BSSO). Both techniques are widely used and the superiority of one or other method is still debatable. One complication of rigid fixation is the need to remove the osteosynthesis material because of associated complaints. The main aim of this retrospective study was to analyse how often we needed to remove bicortical screws because they caused symptoms after BSSO in our clinic. Review of other published papers also enabled us to investigate the reported rates of removal of screws and miniplates at other centres. The mean (SD) duration of follow-up of 251 patients (502 sites) was 432 (172) days, and the number of bicortical screws removed in our clinic was 14/486 sites (3%). Other methods of fixation were used at 16 sites. We found no significant association between removal of bicortical screws and age, sex, presence of third molars, or bad splits. Published rates of removal of bicortical screws and miniplates are 3.1%–7.2% and 6.6%–22.2% per site, respectively. These findings show that fixation with bicortical screws after BSSO is associated with a low rate of removal of osteosynthesis material. Reported incidences imply a lower rate of removal for screws than for miniplates.     

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。