Management of malunited mandibular condylar fractures

The non-surgical treatment of mandibular condylar fractures, may occasionally result in articular imbalance and temporomandibular joint dysfunction. This may be attributed to condylar head displacement and resorption, resulting in a shortened vertical ramus and lost posterior vertical facial height. Restoring the vertical ramus height is essential in the treatment of such dysfunction, and may be accomplished by unilateral, or bilateral ramus osteotomies. Four examples of patients treated with mandibular ramus osteotomies to restore vertical ramus height, with subsequent improvement in occlusal balance and function are presented. The use of the sagittal split mandibular osteotomy and the external vertical ramus osteotomy, stabilized with small osseous plates, and monocortical screws, is discussed.     

Mechanical characteristics of the mandible after bilateral sagittal split ramus osteotomy: comparing 2 different fixation techniques.

PURPOSE: Using finite element (FE) computer model simulation, we compared the mechanical characteristics of the mandible after bilateral sagittal split ramus osteotomy (BSSRO) through the use of 2 different techniques to stabilize the osteotomy. MATERIALS AND METHODS: Based on the reconstructed geometry from computed tomography scans of dry adult skull with a mandibular deformity requiring surgical correction, we developed 3-dimensional FE models that simulate BSSRO with 2 different techniques to stabilize the osteotomy. Technique 1 uses 3 bicortical titanium screws. Technique 2 uses a curved titanium plate with 4 monocortical screws. Five different load cases were applied to the mandible after the simulated BSSRO with the mandible being constrained at both temporomandibular joints. To evaluate the efficacy of these 2 stabilization techniques, we compared 1) the resulting deflections at the central incisor, 2) the mechanical stresses developed in the bone in the vicinity of the stabilizing implants, and 3) the mechanical stresses developed within the screw/plating system themselves. RESULTS: Technique 1, using 3 bicortical titanium screws, leads to smaller deflections at the central incisor for all 5 load cases, suggesting higher mechanical stability. Technique 1 also leads to lower mechanical stresses in the bone and in the implanted screws, whereas technique 2 is associated with higher values in each of these quantities. CONCLUSIONS: To stabilize osteotomies after a 3-dimensional simulated BSSRO, 3 bicortical screws forming an inverted-L configuration are shown to offer more effective load transmission in the mandibular construct. This technique, when examined in an FE model, leads to higher stability with lower mechanical stresses in the bone near the bicortical screws.     

双颌手术升支截骨后退术后下颌稳定性及与关节关系的研究

目的　探讨升支矢状劈开截骨术(BSSRO)小钛板坚固内固定与口内入路升支垂直截骨术(BIVRO)下颌后退术后颌稳定性的不同规律,了解导致复发的有关因素特别是髁状突移位在不同手术后复发过程中的意义。方法　升支截骨手术后退下颌的患者共38例,皆为双颌手术,其中下颌BSSRO19例,BIVRO后退术19例。于手术前1周(T1),手术后1周(T2),3个月(T3)及1年(T4)分别拍摄定位头颅侧位片及定位颞下颌关节薛氏位片用于测量下颌移动幅度及关节髁状突的手术后移位。结果　双颌手术下颌升支截骨后退术后,BSSRO坚固内固定组1年时的复发率为25%,而BIVRO组大部分患者1年时下颌发生了与手术目的相同的移动,两组的不稳定主要发生在术后3个月内。结论　手术使髁状突移位术后位置的调整可导致BIVRO术后的下颌继续后移而不稳定,而髁状突近心骨段术中向后旋转术后位置的调整可导致BSSRO术后的下颌骨继续向前而不稳定     

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.     

Radiographic stereophotogrammetric evaluation of intersegmental stability after mandibular sagittal split osteotomy and rigid fixation

PURPOSE: The purpose of this study was to determine if rigid fixation with bicortical screws and/or miniplates with monocortical screws prevent mobility at the osteotomy site after bilateral mandibular sagittal split osteotomy. PATIENTS AND METHODS: Three metal bone markers were inserted in the proximal and the distal segments of the mandible during the sagittal split operation in 10 patients. These served as measurement points in postoperative follow-up by radiographic stereophotogrammetry. The patients were examined at intervals during the first postoperative year. At each examination, 2 sets of radiographic stereograms were obtained: 1 in rest position and 1 with stress applied to the osteotomy sites. The difference in the position of the proximal segment in relation to the distal segment between the 2 sets of stereograms was recorded. Findings greater than 0.4 degrees and 0.2 mm change indicated true displacement of the bone segments. RESULTS: Immediately after surgery, mobility at of the osteotomy site(s) was found in 8 of 10 patients, and after 1 year it was still present in 4 patients. CONCLUSIONS: Fixation with bicortical screws or miniplates and monocortical screws does not prevent mobility at the osteotomy site after sagittal split osteotomies. This mobility may remain as long as 1 year after surgery. The term "rigid fixation" is thus not a proper term for this kind of fixation.     

The effect of physical rehabilitation on mandibular function after ramus osteotomies

The efficacy of a systematic regimen of rehabilitation of mandibular function after ramus osteotomy was investigated. Forty-eight patients who had had either sagittal split ramus osteotomy to advance the mandible or intraoral vertical ramus osteotomy to retract the mandible were studied; 24 patients received rehabilitation and 24 did not. Pre- and postsurgical maximal mandibular opening, lateral and protrusive mandibular movements, maximum bite force, muscle fatigability, and clinical evaluation of the temporomandibular joints were compared between the two groups. Patients who underwent an intraoral vertical ramus osteotomy did not show a significant decrease in any of the parameters measured whether or not rehabilitation was used. However, patients who underwent sagittal split ramus osteotomies without subsequent rehabilitation had significant decreases (P less than 0.05) in mean mandibular opening and bite force as well as increases (P less than 0.05) in muscular fatigability compared with patients who underwent rehabilitation. These findings indicate the need for routine preoperative evaluation of mandibular and temporomandibular joint function and postsurgical physical rehabilitation after ramus osteotomies.     

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.     

Control of the condylar-proximal mandibular segments after sagittal split osteotomies to advance the mandible

Maintenance of the normal or presurgical anatomic position of the mandibular condyles and contiguous proximal mandibular ramus segments after sagittal split ramus osteotomies is important, not only to enhance the stability of results but also to avoid iatrogenic temporomandibular joint complications. Accordingly, during the past few years, we have attempted to improve the surgical control of condyle and proximal segment position while using the sagittal split ramus osteotomy to advance the mandible. After several modifications, the device reported herein was used and the results evaluated in ten consecutive patients who underwent bilateral sagittal split ramus osteotomies with symmetric advancement of the mandible. This device enables the surgeon to obtain very precise reproduction of the "normal" proximal segment and condyle position at the time of surgery. The use of the device and documentation of its efficiency are presented.     

Sagittal split osteotomy fixed with biodegradable, self-reinforced poly-L-lactide screws. A pilot study in sheep.

Self-reinforced poly-L-lactide (SR-PLLA) screws were used to fix bilateral mandibular sagittal split osteotomies (SSO) in six sheep. No intermaxillary fixation was used postoperatively. The follow-up time was 16 weeks, after which the sheep were killed. Both sides of the mandible were photographed and radiographed. The bending strength of the osteotomy was measured on the left side of the mandible. Histological and microradiographic studies were performed on the right side of the mandible. The results showed that the SR-PLLA screws were strong enough to fix the SSO rigidly. The bending force needed to break the bone was greater than that for the average unoperated mandible. The histological and microradiographic studies showed uneventful healing of the osteotomies in all six sheep. The results indicate that this method should be suitable for rigid fixation of SSO and fractures of the mandible in human beings.     

Hypomobility after maxillary and mandibular osteotomies

A retrospective recall study of forty patients was made to examine mandibular function after orthognathic surgery. Maximum maxillomandibular opening, protrusion, and lateral excursions were measured and compared with similar mandibular movements in a control group of patients of comparable age. Six months to 42 months after maxillary and mandibular osteotomies, the majority of patients demonstrated decreased maxillomandibular opening compared to the control group 54.8 mm (SD 4.7). The decrease was most dramatic in patients previously treated with sagittal split ramus osteotomies. The mean maxillomandibular opening after Le Fort I osteotomy to reposition the maxilla superiorly was 48.7 mm (SD 5.7); after bilateral intraoral vertical ramus osteotomies to retract the mandible it was 48.6 mm (SD 5.7); and after bilateral sagittal split ramus osteotomies to advance the mandible it was 35.1 mm (SD 6.7). The presence of mandibular hypomobility after orthognathic surgery and maxillomandibular immobilization may be due to pre-existing or surgically induced muscle or temporomandibular joint dysfunction. Our findings indicate the need for routine clinical assessment of mandibular function preoperatively and for a systematic regimen of muscular and occlusal rehabilitation postsurgically to normalize muscle function, condylar movement, and range of mandibular motion.     

口内路径下颌骨升枝矢状劈开截骨术治疗下颌前突畸形

下颌骨升枝矢状劈开术是目前世界上使用最普遍的矫正下颌骨畸形的手术方法之一。作者采用口内入路下颌骨畸形的手术方法之一。作者采用口内入路下颌骨升枝矢状劈开截骨术治疗下颌骨前突１８２例，其中真性下颌前突１４３例，假性下颌前突３９例。年龄在１５～５８岁之间，平均２４岁。随访６个月～９年。除９例术后畸形复发需再次矫正以外均获满意效果。本文介绍了口内入路下颌骨升枝矢状截骨术的手术过程及注意事项，并着重讨论了其优缺点，可能出现的并发症及处理方法     

Three-dimensional finite element analysis used to compare methods of fixation after sagittal split ramus osteotomy: setback surgery-posterior loading

We used three-dimensional finite element analysis to compare the biomechanical stability of bilateral sagittal split ramus osteotomies fixed by lag screws with linear and triangular configuration, and double or single six-hole miniplates with monocortical screws after set-back operation. The three-dimensional finite element model contained 122,717 elements and 25,048 nodes. Posterior occlusal loads were simulated on the distal segments. MSC Marc software was used to calculate the stress fields on both the segments and the fixing appliances. We conclude that either triangular lag screw configuration or double miniplates led to better stability and lower mechanical stresses near the osteotomy than the linear lag screws or single oblique miniplates.     

Inferior alveolar nerve function after sagittal split osteotomy of the mandible: correlation with degree of intraoperative nerve encounter and other variables in 496 operations

A total of 1034 patients who had undergone orthognathic surgery were examined after 2 years; 818 had been treated with varying types of mandibular osteotomy such as vertical ramus osteotomy, sagittal split ramus osteotomy, and genioplasty. Neurosensory function in the mental nerve region was assessed by evaluating light touch perception.The incidence of neurosensory deficiency was 216/548 (39%) after sagittal split ramus osteotomy, 26/140 (19%) after extraoral vertical ramus osteotomy, 9/78 (12%) after genioplasty and 60/650 (9%) after intraoral vertical ramus osteotomy. Additional genioplasty increased both the incidence and severity of neurosensory disturbance after intraoral vertical ramus osteotomy but did not significantly influence the neurosensory function after sagittal split ramus osteotomy.The incidences of neurosensory disturbance after mandibular osteotomies in this report correspond well with those previously reported, but the incidence of almost 40% after sagittal split ramus osteotomy must be considered a disquieting drawback of the procedure.     

Stability of skeletal class III malocclusion after combined maxillary and mandibular procedures: rigid internal fixation versus wire osteosynthesis of the mandible.

PURPOSE: The aim of this study was to evaluate skeletal stability after double-jaw surgery for correction of skeletal Class III malocclusion to assess whether there were any differences between wire and rigid fixation of the mandible. PATIENTS AND METHODS: Thirty-seven Class III patients had Le Fort I osteotomy stabilized with plate and screws for maxillary advancement. Bilateral sagittal split osteotomy for mandibular setback was stabilized with wire osteosynthesis and maxillomandibular fixation for 6 weeks in 20 patients (group 1) and with rigid internal fixation in 17 patients (group 2). Lateral cephalograms were taken before surgery, immediately after surgery, 8 weeks after surgery, and 1 year after surgery. RESULTS: Before surgery, both groups were balanced with respect to linear and angular measurements of craniofacial morphology. One year after surgery, maxillary sagittal stability was excellent in both groups, and bilateral sagittal split osteotomy accounted for most of the total horizontal relapse observed. In group 1, significant correlations were found between maxillary advancement and relapse at the posterior maxilla and between mandibular setback and postoperative counterclockwise rotation of the ramus and mandibular relapse. In group 2, significant correlations were found between mandibular setback and intraoperative clockwise rotation of the ramus and between mandibular setback and postoperative counterclockwise rotation of the ramus and mandibular relapse. No significant differences in postoperative skeletal and dental stability between groups were observed except for maxillary posterior vertical position. CONCLUSIONS: Surgical correction of Class III malocclusion after combined maxillary and mandibular procedures appears to be a fairly stable procedure independent of the type of fixation used to stabilize the mandible.     

Transoral 2.0-mm miniplate fixation of mandibular fractures plus 2 weeks' maxillomandibular fixation: a prospective study.

PURPOSE: We conducted a study to assess the efficacy of intraoral treatment of mandibular fractures using a 2.0-mm miniplate and 2 weeks of maxillomandibular fixation (MMF). PATIENTS AND METHODS: Forty-four mandible fractures in 31 patients with a mean of 15 days of MMF were included in this study. A 2.0-mm miniplate was adapted along Champy's lines of ideal osteosynthesis and secured with four 8.0-mm monocortical screws. All patients were followed for at least 8 weeks after surgery. The incidences of bone or soft tissue infections, wound dehiscence, nonunion, malunion, malocclusion, plate fractures, and iatrogenic neurosensory deficits were prospectively evaluated. RESULTS: Primary bone healing was achieved in 100% of cases. No soft or hard tissue infection, malocclusion, malunion, nonunion, dental injuries, plate fracture, or iatrogenic nerve injuries were observed. Two (4.52%) minor complications-intraoral wound dehiscences-were noted. CONCLUSIONS: The use of a single 2.0-mm miniplate adapted along Champy's line of ideal osteosynthesis and stabilized with 4 monocortical screws plus 2 weeks of MMF was a viable treatment modality for mandibular fractures.     

Comparison of different fixation methods following sagittal split ramus osteotomies using three-dimensional finite elements analysis. Part 1: advancement surgery-posterior loading

The purpose of this study was to evaluate the mechanical behavior of different fixation methods used in bilateral sagittal split ramus osteotomy (BSSRO). Part 1 comprises of the results of the analysis for mandibular advancement, four different fixation configurations of six hole fragmentation mini plates with monocortical screws and lag screws and posterior loading conditions in the molar and premolar region. The finite element analysis method (FEA) appears suitable for simulating complex mechanical stress situations in the maxillofacial region. The mechanical behavior of selected lag screws with linear or triangular configuration and double parallel or single oblique six hole mini plates with monocortical screws were compared by FEA after 5 mm BSSRO advancement procedure. Four separate three-dimensional finite element models of the mandible were created to simulate the BSSRO and corresponding fixation methods. These models consisted of 122,717 elements and 25,048 nodes. The mechanical parameters of the materials studied were adopted from the literature or were based on manufacturer's information. 500 N posterior occlusal loads were simulated on the distal segments. The commercial finite element solver MSC Marc software was utilized to calculate the stress fields on both the segments and fixative appliances. It was concluded that the use of 2.0mm lag screws placed in a triangular configuration following the BSSRO advancement surgery provides sufficient stability with any rotational movement and less stress fields at the osteotomy site, when compared with the other rigid fixation methods used in the current study.     

Stability of the mandible after bilateral sagittal split osteotomy: Comparison between positioning screws and plate

Relapse is one of the complications of orthognathic surgery. In this study, we compared the stability of mandibular bilateral sagittal split osteotomy by using two different methods of fixation. In Group 1, eight patients with prognathic mandible underwent BSSO and set back average of 6.0 mm. The method of fixation was positioning screws. In Group 2, eight patients with prognathic mandible underwent BSSO and set back average of 6.0 mm. The method of fixation was plate and monocortical screws. In Group 3, eight patients with retrognathic mandible underwent BSSO and advancement average of 6.0 mm. The method of fixation was positioning screws. In Group 4, eight patients with retrognathic mandible underwent BSSO and advancement average of 6.0 mm. The method of fixation was plate and monocortical screws. The results showed in terms of advancement that there was no significant difference between the groups after one year. However, in terms of set back, this study showed significant difference.     

Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: a study in sheep mandibles

Among the osteotomies performed in orthognathic surgery, the sagittal osteotomy of the mandibular ramus (SOMR) is the most common, allowing a great range of movements and stable internal fixation (SIF), therefore eliminating the need of maxillomandibular block in the postoperative period. Objectives: The purpose of this study was to evaluate the biomechanical resistance of three national systems used for SIF in SOMR in sheep mandibles. Material and methods: The study was performed in 30 sheep hemi-mandibles randomly divided into 3 experimental groups, each containing 10 hemi-mandibles. The samples were measured to avoid discrepancies and then subjected to SOMR with 5-mm advancement. In group I, 2.0x12 mm screws were used for fixation, inserted in an inverted "L" pattern (inverted "L" group). In group II, fixation was performed with two 2.0x12 mm screws, positioned in a linear pattern and a 4-hole straight miniplate and four 2.0x6.0 mm monocortical screws (hybrid group). In group III, fixation was performed with two 4-hole straight miniplates and eight 2.0x6.0 mm monocortical screws (mini plate group). All materials used for SIF were supplied by Osteosin - SIN. The hemimandibles were subjected to vertical linear load test by Kratos K2000MP mechanical testing unit for loading registration and displacement. Results: All groups showed similar resistance during mechanical test for loading and displacement, with no statistically significant differences between groups according to analysis of variance. Conclusion: These results indicate that the three techniques of fixation are equally effective for clinical fixation of SOMR.     

The mandibular foramen: an anatomic study and its relevance to the sagittal ramus osteotomy

The sagittal split ramus osteotomy is the most commonly used procedure to reposition the mandible surgically. Because it is more technically difficult and associated with a higher incidence of complications compared with other mandibular osteotomies, thorough knowledge of the anatomy of the mandibular ramus is a prerequisite. Anatomic measurements related to the mandibular foramen were obtained from 57 formalin-preserved non-Asian hemimandibles. As shown in previous reports, great variability was noted in the position of the mandibular foramen. However, these studies utilized Asian mandibles with a clear discrepancy in key anatomic measurements in comparison with the authors' data. This brings into question the validity of these earlier studies when applying their data to non-Asian groups. The "fade-out" point of the internal oblique ridge was found not to be a reliable anatomic reference for placement of the horizontal osteotomy along the medial ramus. Thus, familiarity with the described relationships of the mandibular foramen will assist in performing properly a sagittal split of the ramus and will reduce the chance for an unfavorable split.     

下颌支矢状劈开术不同固定方式对下牙槽神经功能的影响

目的 研究下颌支矢状劈开术（SSRO）常用两种内固定方式对下齿槽神经（IAN）功能的影响。方法 成年恒河猴12只，均行双侧SSRO后退术。左侧行双皮质骨螺钉固定，右侧行单皮质螺钉与夹板固定。于术前、术后即刻及术后2、4、8、12周时对两侧IAN行感觉神经动作电位（SNAP）检查。结果 SSRO术后即刻SNAP检测示IAN潜伏期延长，波幅减小，较术前有显著差异（P〈0.01），但两侧之间无显著差剐。术后2周起，IAN功能逐渐恢复。至术后12周时右侧IAN的潜伏期基本恢复至术前水平，左侧IAN潜伏期较术前延长15．4％（P〈0．05）；右侧的波幅恢复也要优于左侧（P〈0．05）。结论 SSRO术中使用双皮质螺钉固定舜口单皮质螺钉夹板固定对IAN功能均有影响，但随着时间的延长，IAN功能均有恢复。单皮质骨螺钉与夹板固定相对于双皮质骨螺钉固定对1AN的功能影响要小。