Evaluation of mandibular setback after bilateral sagittal split osteotomy with the hunsuck modification and miniplate fixation.

PURPOSE: This study was conducted to evaluate neurosensory disturbances (NSDs) and jaw movement after bilateral sagittal split osteotomy (BSSO) with the Hunsuck modification and miniplate fixation to correct mandibular prognathism. PATIENTS AND METHODS: A total of 63 patients who underwent Hunsuck-modified BSSO to correct mandibular prognathism were studied. Both 3-month and 6-month postoperative Schuller's temporomandibular joint (TMJ) views tracing the 63 patients were studied to analyze mandibular movement. The patients' NSD and TMJ symptoms were recorded. Data were analyzed using 1-way analysis of variance. RESULTS: The mean TMJ was 9.6% with clicking before surgery. At the evaluation 6 months after surgery, the clicking had reduced to 3.1%. The lip neuorsensory deficit increased to 23.8% at 6 months after surgery. The jaw position measurements before and after surgery showed statistically significant differences in mouth opening and jaw advancement (P < .05). The changes in mandibular lateral movement were not statistically significant (P > .05). CONCLUSIONS: The results of this study show reduced TMJ clicking, the presence of NSDs, and reduced mouth opening after Hunsuck-modified BSSO.     

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.     

Comparative study of skeletal stability between bicortical resorbable and titanium screw fixation after sagittal split ramus osteotomy for mandibular prognathism

IntroductionResorbable screw fixation for orthognathic surgery is widely used in oral and maxillofacial surgery and has several advantages. However, surgeons are concerned about using resorbable screws in orthognathic surgery because of possible postoperative complications such as relapse, screw fracture, and infection. The purpose of this study was to evaluate the skeletal stability of bicortical resorbable screw fixation after sagittal split ramus osteotomies for mandibular prognathism.Materials and methodsThis study included 25 patients who underwent mandibular setback surgery fixed with resorbable screws after sagittal split osteotomy at the Department of Oral and Maxillofacial Surgery at Seoul National University Dental Hospital. Five resorbable screws (Inion CPS^®, Inion Ltd., Finland) were applied bicortically at each osteotomy site via a transbuccal approach. No rigid intermaxillary fixation was applied on the first postoperative day. Passive mouth opening exercises were allowed, using two light, rubber elastics for guidance. The control group was 25 patients fixed with four titanium screws. The follow-up period was 12–22 months (mean 17.8 months). Postoperative skeletal changes on lateral cephalometric radiographs were analyzed and compared between the two groups preoperatively, immediately postoperatively, and 6 months postoperatively.ResultsThe average setback was 6.9 mm and no major intraoperative complications occurred. One patient experienced infection immediately after surgery that was controlled uneventfully. The data did not demonstrate any significant difference in postoperative skeletal stability between the two groups. Differences between the immediate postoperative state and 6 months after surgery were not significant. In earlier cases, especially for patients with severe mandibular prognathism, immediate postoperative elastic traction was needed for stable occlusal guidance.ConclusionsThe results of this study indicate that bicortical resorbable screws offer a clinically stable outcome for the fixation of mandibular sagittal split osteotomies in mandibular prognathism. However the resorbable screws showed less stable results vertically than the titanium screws.     

Skeletal stability following sagittal split osteotomy using monocortical miniplate internal fixation

Skeletal stability was evaluated in 20 patients with mandibular hypoplasia, treated with bilateral sagittal split osteotomies to advance the mandible. Stable internal fixation was obtained using osseous miniplates and monocortical screws. Intermaxillary fixation was released after 5.15 days (range 1 to 11 days). The average B-point advancement was 6.07 mm (range 2.25 to 17.5 mm) and the average Pogonion-point advancement was 5.39 mm (range 1.75 to 14 mm). Mandibular range of motion, TMJ dysfunction and neurosensory deficits were also evaluated. The follow-up period averaged 8.85 months (range 6 to 14 months) and final evaluations were made after completion of orthodontics. Relapse measured at B-point was 10.7% and at Pogonion was 18.7%. Maximal opening decreased an average of 0.47 mm. Symptoms in 8 patients with TMJ dysfunction resolved, while 3 others developed TMJ dysfunction following surgery. Neurosensory deficits were subjectively identified in 9 patients (10 sides) and were objectively measured in 5 patients (5 sides).     

Effect of fixation method on intergonial width stability after mandibular setback via bilateral sagittal split osteotomy

Q4: Horizontal changes occur following bilateral sagittal split osteotomy (BSSO) in skeletal class III patients. The aim of this study was to assess the ostoperative changes in intergonial (IG) width and compare them between the positional screw and miniplate fixation methods in BSSO. This study evaluated patients who had mandibular prognathism and underwent BSSO for mandibular setback. Internal fixation was performed bilaterally, either with positional screws in the lateral ramus or with a miniplate. Postero-anterior cephalograms were obtained preoperatively (T1), at 1 month postoperative (T2), and at 6 months postoperative (T3). The IG widths and the alterations in IG width postoperative (T2 − T1, T3 − T2) were measured. No correlations were observed between the amount of setback and changes at T2  − T1 or T3 − T2. The IG width values decreased after mandibular setback and internal fixation with both methods. Statistical analyses showed a significant difference between T3 and T1 in the miniplate group (P = 0.045). No significant difference in the postoperative change in IG width (T2 − T1 and T3 − T2) was found between the two fixation groups. The magnitude of this change was smaller for positional screws when compared to miniplates for fixation. The amount of mandibular setback showed no correlation with postoperative changes in IG width..     

3D vector analysis of mandibular condyle stability in mandibular setback surgery with bicortical bioabsorbable screw fixation

IntroductionBioabsorbable screws became widely used for stable fixation in orthognathic surgery as biomechanical technology advanced. Recently, 3D image analyses begin to be used to evaluate surgical changes. The purpose of this study was to evaluate, using 3D vector analysis, the stability of bicortical bioabsorbable screw fixation in mandibular setback using a sagittal split ramus osteotomy.Spatial change of the mandibular condyle was determined by 3D coordinates containing directional information.Materials and methodsBicortical screw fixation was performed using either a bioabsorbable screw (25 patients) or a titanium screw (5 patients) in orthognathic surgery. Pre- and post-operative CT images (6 months after surgery) were superimposed digitally. A 3D coordinate (X, Y, Z) and vectors were employed to quantify spatial changes of the condyle and analysed statistically.ResultsMeasuring on 3D image showed stable error about 0.16 mm. There were no significant differences in the total spatial changes of the condyle between titanium and bioabsorbable screws with the exception of the lateral–medial direction of the condylar centre (P = 0.042). The directional vector components were stable, regardless of mandibular setback.ConclusionIn 3D vector analysis, bioabsorbable screw fixation in SSRO with distal segment osteotomy shows clinically acceptable postoperative condylar position stability.     

Complications of bicortical screw fixation observed in 482 mandibular sagittal osteotomies

Bicortical screw fixation after bilateral sagittal split osteotomy (BSSO) of the mandible is commonly used in orthognathic surgery and allows many advantages compared with osteosynthesis wires and maxillomandibular fixation. Complications include early loosening, hardware exposition, skeletal instability or early relapses, persistent nerve impairments, infection, and scar formation. This article is based on a retrospective analysis of complications of bicortical screw fixation observed in 241 consecutive patients with dento-skeletal Class III, corresponding to 482 sides, during the immediate postoperative period and at 1, 3, 6, and 12 months' follow-up. In the immediate postoperative period, poor stability of fixation caused by screw loosening was observed in 3 of 482 (0.62%) sides; at the 1-month follow-up, infections were encountered in 12 (2.48%) sides at mandibular angles. Additional complications were not seen in the series. Stability of fixation was found in the 482 sides at 12 months. However, complications directly related to bicortical screws were observed in 15 sides or 3.11%. Age and gender of patients were not correlated with the incidence of complications. Assiduous follow-up during the early postoperative period and 1 and 2 months after surgery is recommended in patients with bicortical screw fixation after BSSO to verify adequate oral hygiene and provide early observation of the onset of any infections, skeletal instabilities, or relapses.     

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。     

In vitro comparison of screw versus plate fixation in the sagittal split osteotomy.

This study evaluated the transverse strength (rigidity) of three groups of sagittal split osteotomies performed in vitro in fresh sheep mandibles. Fixation was accomplished utilizing two different position screw techniques and a monocortical plate technique. Osteotomies fixed with three 2.0-mm screws in an inverted-L pattern and those fixed with one monocortical miniplate were significantly more rigid than those fixed with two 2.7-mm screws placed in a linear pattern. No significant difference in rigidity was noted between the inverted-L group and the miniplate group.     

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。     

Skeletal stability and condylar position related to fixation method following mandibular setback with bilateral sagittal split ramus osteotomy

PurposeTo investigate postoperative intersegmental displacement and relapse following bilateral sagittal split ramus osteotomy (BSSRO) by comparing three different fixation methods: group A (sliding plate), group B (miniplate) and group C (bicortical screws).Materials and methodsThe present retrospective study included 55 patients with mandibular prognathism who were treated with BSSRO. To evaluate skeletal changes, cone-beam computed tomography was taken before surgery (T0), three days after surgery (T1), and 6 months after surgery (T2). Differences among the three groups were assessed using a one-way analysis of variance, where P < 0.05 was accepted as statistically significant.ResultsThere were no significant differences among the three groups in demographic data and the amount of mandibular setback. In skeletal changes and condylar axis changes, there were no statistically significant differences among the three groups. However, there were statistically significant postoperative skeletal changes in group C (bicortical screws) at all landmarks. The mean horizontal relapse rate was 1.9% in group A (sliding plate); 4.8% in group B (miniplate); and 15.4% in group C (bicortical screws).ConclusionThe sliding plate system has good adaptability to the proximal segment after mandibular setback with BSSRO, and behaves according to semi-rigid fixation principles.     

Transverse stability of the proximal segment after bilateral sagittal split ramus osteotomy for mandibular setback surgery

This study aimed to evaluate the correlation between the transverse displacement of the proximal segment after bilateral sagittal osteotomy for mandibular setback and the amount and design of the mandibular setback. Patients who underwent either bilateral sagittal split ramus osteotomy (BSSRO) alone or two-jaw surgery were selected, and cephalographic postero-anterior (PA) measurements were taken pre-operatively (T1), immediately post-operatively (T2), and at follow-up (T3). The inter-gonal (IG) and inter-ramal (IR) width increased immediately after surgery, but decreased to the initial value during follow-up (P = 0.002; IR, P = 0.046). Only the immediate IG changes after surgery correlated with the amount of mandibular setback (P = 0.009). The IG changes were significant in the symmetric group, but not in the asymmetric group. There was no difference in the IG and IR changes between the symmetric group and the asymmetric group. The immediate IG change in two-jaw patients with symmetric setback showed correlation with the setback amount. The gonial width of the deviated group showed more significant changes than that of the non-deviated group. There was no difference in the unilateral gonial width between the deviated and the non-deviated group, but the difference was significant for the unilateral ramal angle between the two groups. These correlations will be helpful in predicting post-surgical results for patients.     

In vitro biomechanical evaluation of sagittal split osteotomy fixation with a specifically designed miniplate

Recent studies have evaluated many methods of internal fixation for sagittal split ramus osteotomy (SSRO), aiming to increase stability of the bone segments while minimizing condylar displacement. The purpose of this study was to evaluate, through biomechanical testing, the stability of the fixation comparing a specially designed bone plate to other two commonly used methods. Thirty hemimandibles were separated into three equal groups. All specimens received SSRO. In Group I the osteotomies were fixed with three 15 mm bicortical positional screws in an inverted-L pattern with an insertion angle of 90°. In Group II, fixation was carried out with a four-hole straight plate and four 6 mm monocortical screws. In Group III, fixation was performed with an adjustable sagittal plate and eight 6 mm monocortical screws. Hemimandibles were submitted to vertical compressive loads, by a mechanical testing unit. Averages and standard deviations were submitted to analysis of variance using the Tukey test with a 5% level of significance. Bicortical screws presented the greatest values of loading resistance. The adjustable miniplate demonstrated 60% lower resistance compared to bicortical screws. Group II presented on average 40% less resistant to the axial loading.     

Resorbable PLLA-PGA screw fixation of mandibular sagittal split osteotomies.

The purpose of this study was to evaluate the intraoperative placement and clinical effectiveness of resorbable copolymeric screws for mandibular sagittal split ramus osteotomies. Thirty-seven patients who underwent bilateral sagittal split osteotomies of the mandible were fixated with three 2.5-mm copolymeric poly-L-lactic-polyglycolic (PLLA-PGA) screws on each side. No postoperative maxillomandibular fixation was applied. Twenty-five patients experienced mandibular advancement and 12 patients had setbacks. The average advancement was 6.5 mm (range, 3-17 mm) and the average set-back was 5.2 mm (range, 3-8 mm). Intraoperative placement was uncomplicated and no screws were stripped during placement. No problems in immediate postoperative stability were encountered and relapse was not evident in any patient. Follow-up ranged from 3 to 17 months. The screw holes remained evident radiographically after 1 year. Two and one-half-millimeter copolymeric PLLA-PGA resorbable screws for mandibular ramus osteotomies appear to offer clinical results comparable with metallic screw fixation.     

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.