Osseous healing after a sagittal splitting ramus osteotomy

The purpose of this study was to examine osseous healing in the cleavage between the bone fragments after sagittal splitting ramus osteotomy (SSRO) utilizing computed tomography (CT). The subjects were 13 patients with mandibular prognathism who underwent bilateral SSRO. CT was used to study the rami immediately after surgery, then 6 months, 1 year, and 2 years after surgery. Many concave type (the angle between the cleavage >90°) anterior borders developed into the stairway type (the angle between the cleavage <90°) 6-12 months after surgery. Few borders changed to the smooth type. Almost all of the stairway and concave posterior borders changed to the smooth type in the 6-12 months after surgery. Regarding the posterior borders 1 year after surgery, the cleavage of distal and proximal bone fragments demonstrated stable osseous healing (smooth type) in cases where the length and width between the bone fragments were large. In conclusion, the authors successfully demonstrated detailed osseous healing in the cleavage between the bone fragments after SSRO. Remodelling between bone fragments is a major mechanism of osseous healing after this procedure.     

Stability of bilateral sagittal split ramus osteotomy: rigid fixation versus transosseous wiring.

Although many improvements have been made in orthodontic surgical procedures for mandibular retrognathism, relapse continues to occur. This study was designed to compare the stability of rigid and nonrigid fixation between 2 groups of patients who had undergone mandibular advancement surgery via sagittal split ramus osteotomy. Retrospective cephalometric measurements were made on 54 randomly selected orthognathic surgical patients. The patients, 7 males and 47 females, were divided into 2 groups: 28 patients stabilized by means of rigid fixation and 26 patients fixated with interosseous wires. The age of the patients ranged from 15.3 to 49.7 years. Lateral cephalograms were used to evaluate each patient at 3 distinct intervals: 7.0 +/- 2.0 days before surgery (T1), 34.4 +/- 15.0 days postsurgery (T2), and 458 +/- 202 days after sagittal split osteotomy (T3). Eighteen linear and angular measurements were recorded and differences between the 3 time periods were evaluated. Statistical analyses were performed to assess the differences in the 2 fixation types between and within each group at different time intervals. The following measurements showed statistically significant skeletal relapse over time, for the P value.0028: Co-Go, ANS-Xi-Pm, IMPA, overbite, and overjet. The remaining variables showed no statistically significant relapse. The only measurement that showed a statistically significant group difference between T1 and T2 was DC-Xi-Pm. Results of the study led to the following conclusions: there was statistically significant relapse in mandibular length, lower anterior face height, mandibular arc, lower incisor inclination, overbite, and overjet in each group, regardless of the type of fixation. The potential was greater for relapse in patients stabilized with transosseous wiring. Although multifactorial, relapse in overbite and overjet may be a combination of skeletal and dental changes. (Am J Orthod Dentofacial Orthop 2000;118:397-403).     

Mandibular anatomy as it relates to rigid fixation of the sagittal ramus split osteotomy

Rigid fixation of osteotomy segments is frequently used to reduce relapse and allow for early mobilization of the mandible following the sagittal ramus split osteotomy. This study evaluated cortical bone thickness in the retromolar area of 49 human mandibles to determine if there is an advantage (in terms of cortical thickness) to placement of screws for rigid fixation at the external oblique ridge versus placement at the inferior border. The mandibles were sectioned vertically at three sites in the retromolar area, corresponding to the bone available for rigid fixation of the sagittal osteotomy. Cortical bone thickness was measured at the external oblique ridge and 5 mm above the inferior border. The buccal and lingual cortices were found to be significantly (P less than .001) thicker at the external oblique ridge than at the inferior border. This suggests that there may be an advantage in terms of stability to placement of internal fixation screws at the superior border.     

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.     

Lingual nerve injury as a complication of rigid fixation of the sagittal ramus osteotomy: report of a case

This article describes a previously unreported complication of lingual nerve anesthesia and injury as a result of rigid fixation of the mandibular sagittal split osteotomy. The etiology of this injury is discussed and the surgical management using transoral microneurosurgical techniques is described.     

固定方式对下颌升支矢状截骨术骨愈合影响的实验动物研究

目的：比较不同固定方式对下颌升支矢状截骨术术后骨创愈合情况的影响。方法16只成年犬随机分成4组,各组均行改良的双侧下颌升支矢状截骨术,分别采用4种骨段固定形式：①钢丝结扎固定;②小夹板固定;③双皮质螺钉固定;④夹板及钢丝联合固定。术后6周、12周分别处死每组动物2只,完整取出下颌骨,HE染色,镜下观察骨组织愈合情况。结果：各组均可见颊舌侧皮质骨的骨膜下有新骨形成;各组术后6周和12周时组织学表现基本相同;后两组可见直接骨愈合,愈合时无内骨痂形成,截骨线不易辨认,骨髓腔和截骨区充满新骨。结论：固定模式影响了骨段稳定性和应力分布状态,从而影响了截骨创的骨愈合,良好的固定对减少术后远期骨性复发有积极意义。     

Passive rigid fixation of sagittal split osteotomy

To provide increased stability and to decrease intermaxillary fixation time after sagittal split osteotomy, we have used passive rigid fixation. Our method has not only achieved a diminution of intermaxillary fixation time, but it has also resulted in excellent stability and retention. A total of 72 sagittal split osteotomies were performed on 36 patients from July 1985 through December 1986. Rigid fixation was accomplished with two superior border 2.7 mm bicortical screws.     

A biomechanical evaluation of bilateral sagittal ramus osteotomy fixation techniques.

OBJECTIVES: The purpose of this investigation was to evaluate and compare the biomechanical behavior of various rigid internal fixation plates designed to aid in the condylar positioning of bilateral sagittal ramus osteotomies, to positional screws in an inverted-L pattern, and a control. MATERIALS AND METHODS: Fifty polyurethane synthetic mandible replicas (Synbone, Laudquart, Switzerland) were used in this investigation. Five controls and 5 each of 4 different fixation modalities (3 bicortical positional screws in an inverted-L pattern, monocortical 4-hole straight plates, monocortical 6-hole curved plates, and monocortical adjustable 4-hole slide plates) were subjected to vertical loading at the incisal edge and torsional loading at the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0 to 900 N range were recorded. Yield load, yield displacement, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second-order polynomial best-fit curves were also created for each group to further evaluate mechanical behavior. RESULTS: For incisal edge loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness, and between the control group and straight, curved, and slide plates for yield displacement. Differences were also noted between the inverted-L and straight, strut, and slide plates for yield load; and inverted-L and straight, curved, and slide, as well as straight and slide for yield displacement. For molar loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness. Differences were noted between the slide and straight, curved, and control; as well as between the inverted-L and straight and strut plates for yield displacement. Lastly, differences were noted between the straight and curved plates, and the slide and straight, curved, and inverted-L for stiffness. CONCLUSION: In this in vitro study, differences were noted between the control and all experimental groups in their abilities to resist loads under all of the conditions tested. Differences were also noted among specific experimental groups. Yet when placed in the context of functional parameters, only the bicortical positional screws in an inverted-L pattern met the requirements for both molar loading and incisal edge loading.     

The sagittal ramus osteotomy. Stability of fixation with internal miniplates.

Radiographs of 15 patients who underwent sagittal split mandibular ramus osteotomy with rigid miniplate fixation for mandibular lengthening were studied. Evaluation of postoperative stability of the mandibular lengthening at 6 months to 2 years revealed minimal postoperative changes.     

Mandibular range of motion after bilateral sagittal split ramus osteotomy with wire osteosynthesis or rigid fixation

J Evid Base Dent Pract 2001;1:200-1     

Mandibular range of motion after bilateral sagittal split ramus osteotomy with wire osteosynthesis or rigid fixation

OBJECTIVES: An analysis was conducted to compare mandibular range of motion among Class II patients treated with wire osteosynthesis or rigid internal fixation after surgical mandibular advancement.Study Design: Patients randomly received wire osteosynthesis and 8 weeks of maxillomandibular fixation (n = 49) or rigid internal fixation (n = 78). Mandibular range of motion was measured 2 weeks before surgery and 8 weeks, 6 months, and 1, 2, and 5 years after surgery. RESULTS: Both groups showed decreased mobility in all movement dimensions that progressively recovered to near presurgical levels over the 5-year follow-up period. The difference in range of motion between treatment groups was not statistically significant. Changes in proximal and distal segment position could not explain decreased mobility. CONCLUSIONS: Similar decreases in mandibular mobility occurred with wire and rigid fixation of a bilateral sagittal split ramus osteotomy after surgery. Long-term changes were statistically, but not clinically, significant.     

Osteotomy site healing following mandibular sagittal split osteotomy and rigid fixation with polylactide biodegradable screws.

Follow-up of 47 patients, treated using mandibular bilateral sagittal split osteotomy and self-reinforced poly-L-lactide acid (SR-PLLA) screws for rigid internal fixation, is presented. The focus was on clinical and radiological osteotomy healing. The average follow-up time was 2.1 years (range 0.5-5 years). Clinical recovery and radiological osteotomy healing during follow-up were uneventful. Osteolytic changes were seen around the SR-PLLA screws in 27% of cases. The majority of the screw canals remained as radiolucent shadows without bony filling.     

下颌支矢状劈开术不同固定方式对下牙槽神经结构的影响

目的：对比观察下颌支矢状劈开术（sagittal split ramus osteotomy，SSRO）2种内固定方式术后不同时期下牙槽神经（inferior alveolar nenre，IAN）结构的改变，为临床SSRO手术选择内固定方式提供实验依据。方法：选用成年恒河猴12只．全麻下行SSRO后退双侧下颌骨，左、右侧分别行双皮质螺钉固定及单皮质微型夹板固定。术后4、12周时各随机处死6只恒河猴，制作双侧IAN半薄和超薄切片，光镜和透射电镜下观察其结构变化。另选取2只成年恒河猴作为正常对照。应用SPSS11．5统计软件包进行方差分析，组间比较采用q检验。结果：术后4周，所有动物的IAN均出现轻中度Wallerian变性（P=0．000），但同时发现神经轴突再生。在2种固定方式中，术后4周双皮质固定组IAN的病理改变较单皮质固定组重（P=0．02），且单皮质固定组显示出更早和更快的神经再生现象。结论：SSRO结合坚强内固定术对IAN的结构形态均有一定影响，但单皮质固定较双皮质固定对IAN的影响较小，受损神经的恢复再生速度更快。     

Masticatory function and neurosensory disturbance after mandibular correction by bilateral sagittal split ramus osteotomy: a comparison between miniplate and bicortical screw rigid internal fixation

Bilateral sagittal split osteotomy is commonly used to treat mandibular prognathism. Several fixation methods for bony segments have been described. The present study compared masticatory function and neurosensory recovery patterns after mandibular correction between two methods of rigid fixation, bicortical screw (n = 38) and monocortical miniplate (n = 32). Patients who had undergone bilateral sagittal split osteotomy for Class III malocclusion were reviewed, and masticatory function and neurosensory recovery were studied with the appropriate indicators at 1, 3, 6 and 12 months postoperatively. Minimal differences were seen between groups at 1-year postoperatively, and although patients treated with miniplate fixation tended to recover faster, with regard to masticatory function and neurosensory disturbance, than those treated with screw fixation, no significant differences were identified. As the two methods seem to provide equal comfort and reliability, the choice should be made by the individual surgeon.     

MRI changes in the temporomandibular joint following mandibular setback surgery using sagittal split ramus osteotomy with rigid fixation

Objectives: This study examined the changes in temporomandibular joint dysfunction (TMD) symptoms and investigated the variations in the disc position, disc and condylar morphology following sagittal split ramus osteotomy (SSRO) with rigid fixation in patients with mandibular prognathism. Furthermore, the authors examined the correlation between mandibular setback and TMD symptoms.

Methods: The study included 24 Japanese patients with jaw deformities who were treated using bilateral SSRO and Le Fort I osteotomy. The clinical and magnetic resonance imaging findings in the temporomandibular joint were evaluated preoperatively and at three and six months postoperatively.

Results: The preoperative TMD symptoms were significantly associated with the prevalence of TMD symptoms at six months postoperatively. Anterior disc displacement improved in four joints with slight displacement and with no morphological change. There were no postoperative changes in condylar morphology. There was no significant correlation between mandibular setback and the postoperative TMD symptoms.

Conclusion: Postoperative TMD symptoms may be influenced mainly by preoperative TMD symptoms rather than mandibular setback using SSRO with rigid fixation. Therefore, patients with TMD symptoms require physical examination and MRI for appropriate diagnosis preoperatively.     

Changes in the inferior alveolar nerve following sagittal split ramus osteotomy in monkeys: a comparison of monocortical and bicortical fixation

We aimed to observe the changes in the inferior alveolar nerve (IAN) after bilateral sagittal split ramus osteotomy (SSRO) using monocortical or bicortical screw fixation. Bilateral SSRO for setback of the mandible was done in 12 monkeys, and monocortical or bicortical fixation was applied on opposing sides of each mandible. Sensory nerve action potentials were tested before and immediately after operation, and at 2, 4, 8, and 12 weeks. Six animals selected randomly were killed at 4 and 12 weeks after the operation. Specimens of nerve were harvested and processed for histological examination and electron microscopic analysis. Obvious prolongation of latency and diminution of amplitude in the IAN were found postoperatively. At 4 weeks after operation, Wallerian degeneration was apparent, and there were signs of axonal regeneration in the nerves. The IAN had more abnormalities of evoked potentials and pathological changes after bicortical than after monocortical fixation. Although considerable recovery was found after both forms of fixation at 12 weeks, the function of the nerve after plate fixation was better than after screw fixation. Our results suggest that the nerve damage during SSRO could be temporary and reversible, and monocortical fixation may result in restoration of the nerve function sooner than bicortical fixation.