The effect of different hybrid rigid internal fixation techniques on the postoperative stability following a mandibular advancement using a bilateral sagittal split ramus osteotomy: A retrospective three-dimensional comparative study.

OBJECTIVE: To three-dimensionally evaluate post-operative mandibular stability following bilateral sagittal split ramus osteotomies between hybrid and non-hybrid rigid internal fixation techniques. MATERIALS AND METHOD: Seventy adults with skeletal class II deformity who underwent bilateral split sagittal osteotomy with mandibular advancement were included. Patients were divided into four groups based on their fixation techniques: hybrid technique (HT) groups I, II, and IV received a 4-hole 2 mm miniplate with either a bicortical screw (BS), additional 2 mm 4-hole miniplate, or two-hole miniplate, while non-HT group III received a 4-hole 2 mm miniplate with four mini-screws (MS). Measurements were taken pre-operatively (T0), immediately postoperatively (T1), and ≥1 year after surgery (T2) using 3D Slicer software. RESULTS: Age, sex, and follow-up period did not correlate significantly with postoperative relapse or stability. Significant differences were observed in the advancement on the right side between groups II, III, and IV and on the left side between groups I, III, and IV. However, the type of surgical intervention showed no significant effect on postoperative relapse and stability. All groups of fixations showed satisfactory stability with irrelevant relapse (< 2 mm or 2°). CONCLUSION: The study demonstrated satisfactory and comparable stability among different fixation groups on patients undergoing mandibular advancement following bilateral split sagittal osteotomy. The results highlighted the importance of considering the degree of advancement when planning orthognathic surgery and managing postoperative outcomes.

Orthognathic Hardware Complications in the Era of Patient-Specific Implants.

BACKGROUND: Patients undergoing orthognathic skeletal correction present with a variety of comorbidities that may affect surgical outcomes. The purpose of this study was to determine how patient risk factors and operative technique contribute to complication rates after orthognathic surgery in the era of patient-specific implants. METHODS: Retrospective cohort analysis was conducted of pediatric patients undergoing Le Fort I osteotomy, bilateral sagittal split osteotomy, and/or genioplasty from 2014 to 2018. Patient risk factors, operative characteristics, and postoperative outcomes were gathered and compared with appropriate statistics. RESULTS: Ninety-four patients met inclusion criteria, with an overall 1-year complication rate of 11.7 percent (11 of 94). Patient-specific mandibular plates are significantly associated with infection (p = 0.009; OR, 8.8), occurrence of any complication (p = 0.003; OR, 8.3), readmission (p < 0.001; OR, 11.1), and reoperation (p < 0.001; OR, 11.4). In patients with syndromes or history of cleft lip/palate, patient-specific mandibular plates are associated with infection (p = 0.006; OR, 10.3), readmission (p < 0.001; OR, 21.6), and reoperation (p < 0.001; OR, 22.9). In multivariate regression controlling for age, sex, syndrome status, and orofacial cleft history, use of patient-specific mandibular plates was associated with infection (p = 0.017; adjusted OR, 12.5), any complication (p = 0.007; adjusted OR, 11.8), readmission (p = 0.001; adjusted OR, 17.9), and reoperation (p = 0.001; adjusted OR, 18.9). CONCLUSIONS: In the era of patient-specific orthognathic surgery, syndromic status and use of patient-specific mandibular plates are associated with increased infection, readmission, and reoperation because of hardware-related complications. The authors' data support increased caution and counseling with use of patient-specific mandibular implants in patients with syndromic status, history of orofacial cleft, and history of previous maxillomandibular surgery given increased risk of hardware-related complications. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Transoral vertical ramus osteotomy fixed with Kirschner pins.

Transoral vertical ramus osteotomy (VRO) has been condemned because the condyle has the potential to sag, and because it needs lengthy maxillomandibular fixation. We have therefore introduced a simple method of fixation, and examined its effectiveness and complications. After the osteotomy, the proximal and distal segments are trimmed to adapt to each other. Four Kirschner (K) pins 0.9mm in diameter are inserted percutaneously from the proximal to the distal segment while the condyle is positioned in the glenoid fossa. This is followed by a brief period of maxillomandibular fixation. We have reviewed the records of 95 patients who had unilateral or bilateral vertical ramus osteotomy fixed with K pins, after which the mean (SD) period of fixation was 19 (11) days. Fixation failed in two patients because excursion of the jaw was either too heavy or too early. The fixations were redone. All other fixations remained stable, including the 20 dual-jaw procedures in which VRO preceded maxillary osteotomy. The mean (SD) maximal mouth opening at final follow-up was 44 (7) mm, and in only one patient was it less than 30mm. Numbness of the lip or chin developed in seven patients, five of whom had other anterior mandibular procedures. Four patients had discomfort on palpation of the site of the pins, and one required removal. The new method was effective, and resulted in few complications within its limitations.

Surgical guide and CAD/CAM prebent titanium plate for sagittal split ramus osteotomy in the correction of mandibular prognathism.

This study was designed to introduce and evaluate the clinical use of a surgical guide and a CAD/CAM prebent titanium plate for sagittal split ramus osteotomy (SSRO) in the correction of mandibular prognathism. We studied 14 patients who had been diagnosed, and treated by bilateral SSRO with the guide, during the period July 2015-January 2016. Surface deviations of distal segments from simulation until the end of the operation were measured on a coloured map. Deviations of position and orientation of the condyle and proximal segment from before to after operation, and those from simulation until the end of the operation, were measured with a 3-dimensional vector. All patients were followed up for at least a year. The coloured map showed that the mean (SD) distances were 0.40 (0.25)mm between the simulated and postoperative distal segments. The 3-dimensional vector showed that the mean values of mediolateral, anteroposterior, and superior-inferior translations of the condyles were less than 1mm (p<0.02) from before the operation until the end, and from simulation to the end of the operation, and the mean value of pitching for proximal segments was less than 1° (p<0.02) from simulation to the end of the operation. At the one year follow-up, the occlusions were stable. Based on accurate diagnosis and simulation, this guide takes the distal segment precisely to its planned position, and the condyle and proximal segment are well-controlled. This is a useful tool, which is comparatively easy to make and operate.

Three-dimensional Finite Element Analysis of Bone Fixation in Bilateral Sagittal Split Ramus Osteotomy Using Individual Models.

The purpose of this study was to investigate factors involved in stress on locking mini-plate/screws used in orthognathic surgery based on patient-specific 3-dimensional finite element analysis. Data were obtained from 10 patients undergoing mandibular advancement by bilateral sagittal split ramus osteotomy. All underwent osteosynthesis with 2.0-mm titanium locking mini-plate/screws. A 3-dimensional finite element model of the mandible was created for each patient and each model subjected to the same loading conditions, which produced different stress values on locking mini-plate/screws. When the contact area of the proximal and distal bone segments was narrower and bone mineral density (BMD) lower, the von Mises stress values on the plate/screws were higher (contact area, p<0.01; BMD, p<0.05). The present results suggest that bone contact area and BMD should be considered as plate stress factors.

A New Hybrid Technique for Performing a Safer Bilateral Sagittal Split Osteotomy: Combining Reciprocating Saw and Piezoelectric Devices.

The sagittal split osteotomy (SSO) is an indispensable tool in the correction of dentofacial abnormalities. In elective orthognathic surgery, it is important that surgeons inform patients about the risk of complications related to inferior alveolar nerve damage and unfavorable split. The purpose of this article is to describe a novel, hybrid technique to SSO by combining a reciprocating saw and piezoelectric devices with several advantages over traditional "pure" methods (osteotomies performed by reciprocating saw or piezoelectric devices only) in terms of precision, rapidity, easier splitting, and decreased complications related to inferior alveolar nerve damage and bad split with reduced overall morbidity. The level of evidence was Level IV, therapeutic study.

Does fixation method affects temporomandibular joints after mandibular advancement?

PURPOSE: Sagittal split ramus osteotomy (SSRO) is a standard procedure in which miniplates and screws are used to achieve stabilization. Although the titanium plate and screw fixation system is stable, resorbable fixation systems are also used. There is currently no consensus on the ideal fixation technique for SSRO procedures and its effect on the condyle. We aimed to evaluate the stress distribution on temporomandibular joints (TMJ). METHODS: A 3D finite element model of a hemimandible was designed and 5 mm advancement was simulated on a computer model. Four different fixation techniques were applied: inverted-L shaped bicortical screws, L-shaped bicortical screws, miniplate with monocortical screws, and miniplate with monocortical screws and bicortical screw. Computer models were prepared twice for resorbable and titanium material. Load of 600N and muscle forces were applied. In the finite element analysis, computer models simulated and analyzed stress distribution of bone, fixation materials and condyle. RESULTS: Bicortical screws increase the total stress on TMJ, and the stress is located more on the posterior part than the anterior. Miniplates decrease the stress, and the forces are located more on the anterior aspect of the TMJ. CONCLUSION: According to our analysis, the use of bicortical screws increases the stress amount on the condyle. For the patients with a tendency toward temporomandibular disorders, using miniplate fixation techniques may decrease the forces around the condyle. These findings should be useful for oral surgeons when deciding on the most appropriate fixation technique in patients with a tendency toward temporomandibular joint disorders.

Computer-assisted teaching of bilateral sagittal split osteotomy: Learning curve for condylar positioning.

Bilateral sagittal split osteotomy (BSSO) is a widely-performed procedure in orthognathic surgery for the correction of dentofacial deformity. Condylar positioning is a critical step during BSSO to maximize functional and morphological results. The unsuitable positioning of condyles represents one of the causative mechanisms that may induce temporomandibular joint noxious effects after BSSO. Repositioning devices can assist surgeons in maintaining the preoperative condylar position; however, empirical repositioning methods based on experience gained are still commonly used. Trainee learning curves are difficult to assess. The aim of this study was to evaluate the relevance of computer-assisted surgery in the acquisition of condylar positioning skills. Forty-eight patients underwent BSSO performed by six maxillofacial trainees (four junior residents and two senior experienced residents). A condyle positioning system (CPS) was used by a senior surgeon to record a condylar position score during the procedure. Firstly, scores were recorded when the trainee manually positioned the condyle without access to the CPS score (phase 1) and then when the trainee positioned the condyle and performed osteosynthesis with visual access to the CPS score (phase 2). Six parameters describing condylar three-dimensional motions were assessed: translational motion from top to bottom (TB), back to front (BF), and left to right (LR), axial rotation (AR), sagittal rotation (SR), frontal rotation (FR), and a total score (TS). There were no significant differences between junior and senior residents in condyle positioning without access to the CPS. Condyles were significantly better positioned during phase 2 with access to the CPS (p<0.001). Over time, use of the CPS (phase 2) produced significantly quicker improvements in scores (p = 0.042). For those teaching surgeries to trainees, computer-assisted devices can potentially result in more rapid learning curves than traditional "observations-imitation" models. Use of a CPS by trainees facilitated condylar repositioning that resulted in an accurate occlusal result and avoidance of adverse effects on the temporomandibular joint.

Comparative study of biomechanical stability of resorbable and titanium fixation systems after sagittal split ramus osteotomy with a novel designed in-vitro testing unit.

INTRODUCTION: Sagittal split ramus osteotomy (SSRO) is one of the most popular surgical procedures for correction of mandibular deformities. Several clinical and biomechanical studies exist in the literature which, comparing the stability of different osteosynthesis materials and techniques, were performed using two or three-point biomechanical test models. The aim of this study was to compare the stability of biodegradable and titanium materials for SSRO on one-piece polyurethane mandible samples which were fixed in a novel designed 6-point testing unit. MATERIALS AND METHODS: 16 polyurethane one piece replicas of human mandibles were used and bilateral SSRO were performed by the manufacturer according to Dal Pont modification. Mandibles were fixed with titanium and PLLA/PGA fixation materials. Displacement amounts were measured under loading forces using a non-contact extensometer, and strain values at the screws were recorded by strain gauges. RESULTS: Bicortical titanium screws (Group 2) showed significantly lower displacement values, while bicortical PLLA/PGA screws (group 4) showed significantly higher displacement values at 40-360 N forces. (p < 0.05). The highest strain value was measured on screws that were inserted upright in a proximal segment near the osteotomy line. CONCLUSION: To achieve more realistic results in biomechanical studies, test models should imitate jaw movements and test environments should be as similar as possible to physiological conditions. Newly designed six-point testing units will contribute to future biomechanical studies.

Evaluation of Intersegmental Displacement After Mandibular Setback Split Ramus Osteotomy Using Modified L-Shaped Monocortical Plate: Cone-Beam Computed Tomography Superimposition.

PURPOSE: The purpose of the current study is to compare intersegmental displacements after mandibular setback sagittal split ramus osteotomy (SSRO) using 4 types of osteosynthesis methods. PATIENTS AND METHODS: This is a retrospective study of 53 subjects who presented underwent bilateral setback SSRO at Pusan National University Hospital from January 2009 to December 2013. The subjects were divided into 4 groups according to the osteosynthesis method applied: group A-modified L-type monocortical plate; B-conventional miniplate; group C-bicortical screws; group D-metal and absorbable screws. To obtain the intersegmental displacement, the mean of the differences of the 3-dimensional from T0 (2 days after surgery) to T1 (6 months after surgery) was calculated for the right and left condylar heads (condylion, Cd) and the right and left coronoid processes (Cps) using 3-dimensional imaging software (Ondemand 3D; Cybermed Co, Seoul, Korea). RESULTS: For the condylion in the x, y, z coordinate system, in group A, there were significant differences in the y-axis for the right and left Cd; in group B, significant differences in the y-axis for the right Cd and in the y- and z-axes for the left Cd; in group C, no significant differences in the axis for the Cd; and in group D, there were significant differences in the y- and z-axes for the right Cd and in the x- and y-axes for the left Cd. For the Cps, the results are not much different from the condylion movement in all group. CONCLUSION: In the current study, group C manifested the greatest displacement for the healing period. Group A did not show the significant difference to group B. In view of these results, modified L-shaped monocortical plate can be applied for osteosynthesis effectively.

Does Fixation Method Affect Stability of Sagittal Split Osteotomy and Condylar Position?

PURPOSE: Fixation methods are important for condylar position and stability in sagittal split osteotomy (SSO) procedures. The aim of the present study was to compare the changes in the condylar position and stability after SSO for mandibular setback in plate fixation with monocortical screws and bicortical screws. PATIENTS AND METHODS: In the present retrospective cohort study, patients who had undergone mandibular setback were studied in 2 groups. In group 1, fixation was performed using a miniplate with 4 monocortical screws. In group 2, fixation was performed using 3 bicortical screws. Cone beam computed tomography scans were taken before and immediately after the SSOs and 1 year later. The condylar position was evaluated linearly (mediolateral movement in the coronal view) and angularly (condylar axis with Frankfort plane in the coronal view). The stability of the mandible was determined at the B point horizontally and vertically. RESULTS: A total of 50 patients were studied in 2 equal groups; however, 2 patients were lost to follow-up in group 2. A significant difference in the mediolateral changes of the condyle before and after osteotomy was detected between the 2 groups (P = .003). No difference was found between the 2 groups in the angular changes of the condyle before and after SSO in the coronal view (P = .45). Analysis of the data did not reveal any differences for vertical relapse at the B point (P = .47) or horizontal relapse between the 2 groups (P = .21). CONCLUSIONS: According to our results, bicortical screw fixation might be associated with more condylar displacement. However, we could not find significant differences in surgical stability between miniplate fixation with monocortical screws and bicortical screw fixation after 1 year of follow-up.

Systematic three-dimensional analysis of wafer-based maxillary repositioning procedures in orthognathic surgery.

PURPOSE: Little is known about the three-dimensional (3D) transfer accuracy in maxillary repositioning procedures based on conventionally manufactured dental-mounted wafers. The purpose of the present study was a systematic 3D analysis for wafer-based maxillary positioning in orthognathic surgery. MATERIALS AND METHODS: A total of 92 patients underwent Le Fort I in addition to mandibular bilateral sagittal split osteotomies (BSSO). Alignment of the pre- and postsurgical CBCT data sets allowed measuring maxillary position changes in axial, sagittal and transversal directions. RESULTS: The highest achieved absolute transfer inaccuracies were 1.37 mm, ±0.84 in the sagittal direction, followed by 1.15 mm, ±0.69 in the axial, as well as 1.05 mm, ±0.79 in the transversal direction. The largest relative deviations could be found for repositions in the transversal plane (109.4%, ±4.5), followed by the axial (66.2%, ±51.5) and sagittal plane (49.3%, ±2.2). Significant transfer accuracy differences of repositioning procedures in the sagittal direction, mainly advancement procedures, could be detected if performed with (1.75 mm, ±0.90) or without (1.18 mm, ±0.78) additional rotational correction component. No significant differences were found between unidirectional and multidirectional maxillary correction procedures. CONCLUSION: The present study for the first time delivers systematic 3D accuracy data of wafer-based maxillary positioning procedures, attesting to its feasibility but also further encouraging the search for improvement strategies.

Stability of biodegradable metal (Mg-Ca-Zn alloy) screws compared with absorbable polymer and titanium screws for sagittal split ramus osteotomy of the mandible using the finite element analysis model.

Mg-Ca-Zn alloy has been suggested for the application of fixation materials during maxillofacial surgery. We investigated the stability of Mg-Ca-Zn alloy for clinical application during orthognathic surgery. The finite element model for the fixation of sagittal split ramus osteotomy was constructed. In the bicortical screw fixation of the mandible setback condition, the stress distributions of Mg-Ca-Za alloy, polylactic acid polymer, and titanium were evaluated using the virtual model with occlusal loading of 132 N. The deformations of the three different materials of fixation screw were observed according to masticatory force ranging from 132 to 1,000 N. When comparing the stress distribution placed on cortical bone between the polymer and magnesium alloy groups, the magnesium alloy screws could bear more stress, thereby decreasing the stress, which might be distributed to other biologic components, such as the condyle and cortical ramus of the mandible. Deformations of the screws according to functional load were minimal, and the deformation remained <0.21 mm at the initial functional load of the mandible after surgery, regardless of materials used. The biodegradable magnesium alloy screw can bear more stress and decrease the detrimental effect on the stability of sagittal split ramus osteotomy setback surgery.

Modified Medial Ramus Retractor to Facilitate Horizontal Osteotomy During Sagittal Split Ramus Osteotomy Procedure.

Introducing a horizontal osteotomy is the first and a critical step in sagittal split ramus osteotomy procedure. Identification of the lingula and medial displacement of the vital structures entering the inferior alveolar foramen are of paramount importance in ensuring a risk-free placement of the medial cut with bur or a saw. Quite often, identification of lingula and retrolingular fossa can be an arduous task owing to the thickness of the internal oblique ridge. Hence, placement of horizontal osteotomy depends on the experience of the operator.Here, the authors describe a simple, low profile instrument that aids in the identification of the lingula as well as provide a posterior stop for horizontal osteotomy during the sagittal split ramus osteotomy procedure.

Comparison between piezoelectric surgery and conventional saw in sagittal split osteotomies: a systematic review.

A systematic review of the advantages and disadvantages of piezoelectric surgery in comparison with conventional saws for sagittal split osteotomy (SSO) was performed. Relevant studies published in the last 10 years were identified through a search of the PubMed/MEDLINE, Science Direct, and Embase databases and assessed against predetermined eligibility criteria. The initial search resulted in 1736 articles. After applying the inclusion and exclusion criteria, 12 articles remained. A total of 799 patients with an average age of 27.5 years underwent SSO performed using a saw or ultrasonic device. Results showed that it took longer to perform the osteotomies using an ultrasonic device than using a conventional saw. At ≥6 months of follow-up, neurosensory disturbance was seen in 4.7% of patients who underwent piezoelectric surgery versus 61.6% of patients who underwent surgery in which a conventional saw was used. It was found that the use of piezoelectric surgery in SSO leads to the best outcome regarding neurosensory disturbance when compared to conventional saws (P=0.04) at ≥6 months of follow-up. Further studies are required for the evaluation of the other clinical parameters assessed.

The use of patient-specific implants in orthognathic surgery: A series of 30 mandible sagittal split osteotomy patients.

PURPOSE: Virtual surgery combined with patient-specific saw and drill guides and osteosynthesis materials are rapidly spreading from reconstructive surgery to orthognathic surgery. Most commercial partners are already providing computer-aided design and computer-aided manufacture (CAD/CAM) wafers and patient-specific saw guides. Clear benefits have been demonstrated for custom-made drill guides combined with individually designed three-dimensional (3D) printed patient-specific implants (PSI) as a reposition and fixation system in Le Fort I osteotomy. MATERIALS AND METHODS: We treated 30 patients who underwent bilateral sagittal split osteotomy (BSSO) due to class II dento-skeletal deformities with the additional use of drill guides combined with PSI as a fixation and positioning system. RESULTS: The PSIs fitted bilaterally with total precision in 11 of the 30 patients. In 17 patients, the PSIs were used with some modifications. In 2 of 30 patients, the PSIs could not be used as a fixation due to misfit. CONCLUSION: Due to unpredictable fitting, the use of PSIs with drill guides alone in BSSO without wafers cannot be recommended. Further studies are needed to evaluate the interfering parts, which seem to be related to condylar positioning and bony interferences at the osteotomy sites.

Computer assisted positioning of the proximal segment after sagittal split osteotomy of the mandible: Preclinical investigation of a novel electromagnetic navigation system.

INTRODUCTION: Modifications of the temporomandibular joint position after mandible osteotomy are reluctantly accepted in orthognathic surgery. To tackle this problem, we developed a new navigation system using miniaturized electromagnetic sensors. Our imageless navigation approach is therefore optimized to avoid complications of previously proposed optical approaches such as the interference with established surgical procedures and the line of sight problem. MATERIAL AND METHODS: High oblique sagittal split osteotomies were performed on 6 plastic skull mandibles in a laboratory under conditions comparable to the operating theatre. The subsequent condyle reposition was guided by an intuitive user interface and performed by electromagnetic navigation. To prove the suitability and accuracy of this novel approach for condyle navigation, the positions of 3 titanium marker screws placed on each of the proximal segments were compared using pre- and postoperative Cone Beam Computed Tomography (CBCT) imaging. RESULTS: Guided by the electromagnetic navigation system, positioning of the condyles was highly accurate in all dimensions. Translational discrepancies up to 0,65 mm and rotations up to 0,38° in mean could be measured postoperatively. There were no statistically significant differences between navigation results and CBCT measurements. CONCLUSION: The intuitive user interface provides a simple way to precisely restore the initial position and orientation of the proximal mandibular segments. Our electromagnetic navigation system therefore yields a promising approach for orthognathic surgery applications.

Three-Dimensional Analysis of Long-Term Stability After Bilateral Sagittal Split Ramus Osteotomy Fixed With a Single Miniplate With 4 Monocortical Screws and 1 Bicortical Screw: A Retrospective 2-Center Study.

PURPOSE: This study evaluated the long-term stability of bilateral sagittal split ramus osteotomy fixed with a single miniplate with 4 monocortical screws and 1 bicortical screw (hybrid technique [HT]) using 3-dimensional (3D) analysis and an objective measuring tool, cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Sixty-four patients who underwent bimaxillary surgery with mandibular advancement fixed with the HT were selected from 2 different institutions and enrolled in this retrospective study. All patients underwent CBCT preoperatively, 1 month after surgery, and 12 months after surgery. To estimate the long-term stability of the HT, volumetric comparisons were performed using the following measurements: distance between the gonion and the B point in the sagittal plane; distance between the right and left gonion transversally; and the angle of the line connecting the mandibular notch and the gonion and the line connecting the gonion and the B point vertically. RESULTS: Statistical analysis showed no relevant relapse (<1 mm or <1°) when using the HT. However, a positive correlation between the amount of advancement and the amount of postoperative relapse was observed. CONCLUSION: The HT produces stable postoperative 3D results after 12 months.