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.

Bone quality assessment in patients with healing mandibular fracture sites: a computed tomography investigation.

The objective of this retrospective study was to assess the bone quality of healing mandibular fracture sites by measuring the Hounsfield units (HU) on computed tomographic (CT) images obtained presurgery and postsurgery in patients treated with rigid internal fixation (RIF). The HU values of healing fracture sites were compared to those of corresponding nonfractured (control) sites on the opposing side and cervical vertebrae sites in the same patients. In total, 31 patients with 45 mandibular fractures treated with RIF underwent presurgical and postsurgical CT examinations. The scans performed after surgery (1, 3, 6, 12, or 18 months) were taken only when there was a need for radiographic evaluation due to a complaint of discomfort from the patient or when the surgeon needed to verify the postsurgical outcome, and each patient underwent only a single postsurgical CT. At the presurgical CT examination, the HU values were lower in the fracture sites than in the control sites. At 3 months postsurgery, the HU values in the fracture sites had increased as the mandibular bone healed. At 6 months postsurgery, the HU values in the fracture sites were higher than those of the control sites. At 12 and 18 months postsurgery, the HU values of both sites were similar. The HU values of the cervical vertebrae remained constant with time. These results suggest that, in patients who have been treated with RIF for mandibular bone fracture, HU values measured by CT vary across time, expressing the physiologic bone healing process.

Abordagem cirúrgica em fratura de sínfise e côndilo mandibular bilateral em paciente pediátrico: um relato de caso / Surgical approach for syphysis and bilateral mandibular condyle fracture in a pediatric patient: a case report

As indicações de tratamento das fraturas mandibulares em paciente pediátrico variam em conservador, fixação não rígida e interna rígida. Alterações no crescimento ósseo, disfunções na articulação temporomandibular e assimetrias faciais podem ser decorrentes ao insucesso do tratamento. O objetivo deste trabalho consiste em relatar abordagem cirúrgica em fratura de sínfise e côndilo mandibular bilateral em paciente pediátrico. Paciente gênero feminino, 09 anos de idade, foi encaminhada ao Hospital Geral do Estado - Bahia vítima de queda de nível, cursando com trauma em face. Apresentou queixa principal, referida pela progenitora, de dificuldades em fechar a boca. Ao exame físico, a paciente apresentou mobilidade atípica à manipulação da mandíbula, mordida aberta anterior, equimose sublingual, ausência das unidades dentárias 74 e 75, com abertura bucal regular e suturas em posição em região de mento. Ao exame de imagem de tomografia computadorizada da face, pôde-se notar sinais sugestivos de fratura em região de sínfise e côndilos mandibulares bilateral. Após diagnóstico das fraturas, a paciente foi submetida à cirurgia sob anestesia geral para redução e fixação das mesmas. Realizou-se acessos em ferimento na região mentual e retromandibular bilateral com posterior síntese das fraturas utilizando fixação interna rígida com placas do sistema 2.0mm, associada a odontossíntese na fratura de sínfise. Ao acompanhamento periódico, a eleição do tratamento cirúrgico para fraturas mandibulares em pacientes pediátricos, pode permitir segurança no crescimento ósseo mandibular e facial(AU)

The indications for treatment of mandibular fractures in pediatric patients vary from conservative, non-rigid fixation and rigid internal fixation. Changes in bone growth, temporomandibular joint disorders and facial asymmetries may be due to treatment failure. The objective of this work is to report a surgical approach to bilateral symphysis and mandibular condyle fractures in a pediatric patient. Female patient, 9 years old, was sent to the State General Hospital - Bahia, victim of a fall in level, suffering from trauma to the face. She presented a main complaint, mentioned by her mother, of difficulties in closing her mouth. On physical examination, the patient presented atypical mobility when manipulating the jaw, anterior open bite, sublingual ecchymosis, absence of dental units 74 and 75, with regular mouth opening and sutures in position in the chin region. When examining the computed tomography image of the face, signs suggestive of fracture in the region of the symphysis and bilateral mandibular condyles were noted. After diagnosis of the fractures, the patient underwent surgery under general anesthesia to reduce and fix them. Access was performed on a wound in the mental and bilateral retromandibular region with subsequent synthesis of the fractures using rigid internal fixation with 2.0mm system plates, associated with odontosynthesis in the symphysis fracture. With periodic monitoring, the choice of surgical treatment for mandibular fractures in pediatric patients can allow for safe mandibular and facial bone growth(AU)

Postoperative Complications following Open Reduction and Rigid Internal Fixation of Mandibular Condylar Fracture Using the High Perimandibular Approach.

The high perimandibular approach is a feasible surgical technique for treating mandibular condylar fractures with open reduction and internal fixation, followed by fewer complications. Temporary trismus is the only postoperative complication that may occur. This study evaluated postoperative complications following open reduction and rigid internal fixation (OR-IF) of mandibular condylar fractures using the high perimandibular approach. Twenty consecutive patients undergoing OR-IF were included in this study. They included 11 male and 9 female patients, of an average age of 58.5 years, all of whom responded to a follow-up call at least 12 months after the surgery. All patients were evaluated for range of mouth opening, postoperative complications, and radiological findings. A statistical analysis of the relationship between range of mouth opening and related clinical parameters at 6 months postoperative evaluation was conducted. The fracture of the condylar neck was associated with a limited range of mouth opening and longer operation time. However, longer operation time was not associated with a limited range of mouth opening. The high perimandibular approach with OR-IF in mandibular condylar fractures is a feasible and safe technique; however, prolonged surgery and mandibular condylar neck fractures could affect the postoperative range of mouth opening.

Evaluation of the Properties of 3D-Printed Ti Alloy Plates: In Vivo and In Vitro Comparative Experimental Study.

Titanium (Ti)-based implants play a significant role in rigid internal fixation in maxillofacial surgery. No study has reported that three-dimensional-printed Ti alloy plates (3D-Ti plates) have comprehensively excellent properties similar to standard plates (Matrix-MANDIBLE, SYNTHES, Switzerland) (Synthes-Ti plates). In this work, we manufactured 3D-Ti plates by selective laser melting with Ti6Al4V powder. The surface morphology, mechanical properties, and bone-plate contact rate of the 3D-Ti plates and the Synthes-Ti plates were characterized and compared via electron microscopy, atomic force microscopy, Vickers hardness test, three-point bending test, and software calculation. Human bone marrow stromal cells (HBMSCs) were cultured on the plates to test their biocompatibility. Importantly, the 3D-Ti plates were placed into a mandibular fracture model to assess the effect of medical application for 4 and 24 weeks. The 3D-Ti plates were demonstrated to have similar biocompatibility and stability for rigid internal fixation with the Synthes-Ti plates, lower roughness (106.44 ± 78.35 nm), better mechanical strength (370.78 ± 1.25 HV10), and a higher bone-plate contact rate (96.9%). These promising results indicate the feasibility of using 3D-Ti plates for irregular shapes and complex anatomical structures in a clinical context.

Biomechanical Evaluation of Seven Fixation Methods for Sagittal Split Ramus Osteotomy with Four Advancement Levels by Finite Element Analysis.

Background: Mandibular sagittal split ramus osteotomy (SSRO) is a routine surgery to correct mandibular deformities, such as mandibular retrusion, protrusion, deficiency, and asymmetry. However, nonunion/malunion of the fragments and relapse caused by fixation failure after SSRO are major concerns. Rigid fixation to maintain postosteotomy segmental stabilization is critical for success. Additionally, understanding the biomechanical characteristics of different fixation methods in SSRO with large advancements is extremely important for clinical guidance. Therefore, the aim of the present study was to evaluate the biomechanical characteristics of different SSRO methods by finite element analysis. Methods: SSRO finite element models with 5-, 10-, 15-, and 20-mm advancements were developed. Seven fixation methods, namely, two types of bicortical screws, single miniplate, dual miniplates, grid plate, dual L-shaped plates, and hybrid fixation, were positioned into the SSRO models. Molar and incisal biomechanical loads were applied to all models to simulate bite forces. We then investigated the immediate postoperative stability from four aspects, namely, the stability of the distal osteotomy segment, osteotomy regional stability, stress distribution on the mandible, and implant stress performance. Results: The stability of the distal osteotomy segment and osteotomy region decreased when the advancement increased. All seven fixation methods displayed favorable biomechanical stability under minor advancement (5 mm). With large advancements, bicortical screws, dual miniplates, and grid plates provided better stability. The von Mises stress was concentrated around the screws close to the osteotomy region for the proximal segment for all fixation methods, and the von Mises stress on implants increased with larger advancements. With small advancements, five fixation methods endured tolerable maximum stresses of <880 MPa. A single miniplate and dual L-shaped plates generally suffered high stresses using larger advancements. The biomechanical characteristics were similar under molar and incisal loads. Conclusions: The current study investigated the biomechanical properties of seven fixation devices after SSRO under molar and incisal loads. Generally, bicortical screws, grid plates, and dual miniplates provided better biomechanical stability using finite element analysis.

The Osteosynthesis of the Mandibular Head, Does the Way the Screws Are Positioned Matter?

Currently, an increasing number of medical centers are treating mandibular head fractures surgically. Dedicated screws for compression osteosynthesis have been developed. However, due to the very limited size of the fractured bones and the considerable technical difficulties accompanying the execution of the fixation, there is little room for correction of the positioning and reinsertion of the screws. Therefore, knowing the optimal position of the fixation material is crucial for therapeutic success. The aim of this study is the evaluation of fixation screw position on the mandibular ramus height obtained in the treatment of the condylar head fracture. A total of 57 patients were included in this study. The loss of mandibular ramus height on computed tomography twelve months after mandibular head osteosynthesis was evaluated in relation to the initial distance of the screws from the fracture line, the angle of insertion of the screw into the bone, and the size of the protrusion to the inner side of the condyle. The relationship of the proximity of the screw to the fracture line, angulation, and the size of the protrusion with the loss of ramus height was confirmed. Conclusions: the optimal location for the superior screw is approx. 4 mm below the fracture line (with any angulation), inferior screw is approx. 8 mm (with any angulation), and anterior screw position is approx. 4-5 mm distant from fracture line with the best angulation of 130 degrees to the lateral mandible ramus surface in the coronal plane.

Bone Union Quality after Fracture Fixation of Mandibular Head with Compression Magnesium Screws.

For some years now, fixation devices created with resorbable magnesium alloys for the mandibular head have been clinically available and are beginning to be used. It is thus valuable to evaluate the quality of unions in these cases. The aim of this study was radiological comparison of magnesium versus titanium open reduction and rigid fixations in the mandible condylar head. Thirty-one patients were treated for fractures of the mandibular head with magnesium WE43 alloy headless compression screws (diameter 2.3 mm) and, as a reference group, 29 patients were included with similar construction titanium screws (diameter 1.8 mm). The 12-month results of the treatment were evaluated by the texture analysis of CT. Near similar treatment results were found with magnesium screws in traditional titanium fixation. Magnesium screws result in a higher density of the bone structure in the mandibular head. Conclusions: The quantitative evaluation of bone union after surgical treatment of mandibular head fracture with magnesium compression headless screws indicates that stable consolidation was achieved. Undoubtedly, the resorption process of the screws was found to be incomplete after 12 months, evidenced by a marked densification of the bone structure at the fracture site.

Clinical Evaluation of Magnesium Alloy Osteosynthesis in the Mandibular Head.

Titanium alloys are used in skeletal surgery. However, once bone union is complete, such fixation material becomes unnecessary or even harmful. Resorbable magnesium materials have been available for several years (WE43 alloy). The aim of this study was to clinically compare magnesium versus titanium open reduction and rigid fixations in mandible condylar heads. Ten patients were treated for fractures of the mandibular head with magnesium headless compression screws (2.3 mm in diameter), and 11 patients were included as a reference group with titanium screws (1.8 mm in diameter) with similar construction. The fixation characteristics (delay, time, and number of screws), distant anatomical results (mandibular ramus height loss, monthly loss rate, and relative loss of reconstructed ramus height), basic functional data (mandibular movements, facial nerve function, and cutaneous perception) and the influence of the effects of the injury (fracture type, fragmentation, occlusion, additional fractures, and associated diseases) on the outcome were evaluated. The long-term results of treatment were evaluated after 18 months. Treatment results similar to those of traditional titanium fixation were found with magnesium screws. Conclusions: Resorbable metal screws can be a favored option for osteosynthesis because surgical reentry can be avoided. These materials provide proper and stable treatment results.

Does the type of sagittal split ramus osteotomy influence fixation strength? Evaluation of the mechanical behavior of two types of fixation used in three types of sagittal split ramus osteotomy.

PURPOSE: This study compared the mechanical behavior of two fixation techniques used in three sections representing the sagittal split ramus osteotomy (SSRO) in polyurethane replicas that were divided into groups, according to type of section, and sub-groups according to type of fixation, simulating 11-mm advancement and 6º clockwise mandibular rotation. METHODS: Loads were applied in two regions, aiming at progressive application and consequent strength value, measured in kilogram-force in displacements of 1, 3, 5, and 7 mm, from the load application tip. Shapiro-Wilk test was performed, followed by two-way analysis of variance (ANOVA-2 way), and Bonferroni's multiple comparison. RESULTS: The results showed no statistically significant difference in the type of section and type of fixation used when load was applied to the inter-incisor region. However, when load was applied to the first molar region, statistically significant difference was observed in 1-mm displacement, in which section described by Epker with two modifications showed greater strength, regardless of type of fixation used (p = 0.007). CONCLUSION: In the application of load in the inter-incisor region, there was no statistical difference between the type of osteotomy and the type of fixation used. When applying loads to molars, there was a difference for the type of osteotomy, where the Epker osteotomy with 2 modifications presented greater resistance, regardless of the type of fixation used.

Skeletal and Soft-Tissue Stability Following Advancement Genioplasty: A Comparative Analysis between Wire and Miniplate Osteosynthesis.

BACKGROUND: Genioplasty has nowadays become a routine procedure in the correction of dentofacial deformities. The present study aimed to evaluate and compare the osseous and soft-tissue stability after advancement genioplasties, stabilized using wire and plate osteosynthesis. METHODOLOGY: The study was conducted on ten patients who underwent advanced genioplasty. The patients were divided equally into two groups. In the Group I patients, plates and in Group II, wires were used for stabilization. Lateral cephalograms preoperative and 6 months postoperative were analyzed using Park et al. method of cephalometric analysis. RESULTS: All the ten patients experienced a reliable improvement in esthetics. Although statistically not significant, Group II wire patients have slightly more relapse in the horizontal direction than Group I. The mean ratio of sagittal changes of osseous soft tissue for Group I was 1:0.88 and for Group II wires was 1:0.80. CONCLUSION: The choice of method of fixation following genioplasty would entirely be based on the merits of the individual cases. The marginal edge of advantage seen in miniplate osteosynthesis when compared to wire osteosynthesis is seen in cases that require larger chin advancements.

Evaluation of the effect of mandibular length and height on the sagittal split ramus osteotomy rigid internal fixation techniques: A finite element analysis.

PURPOSE: A major concern after mandibular advancement with sagittal split ramus osteotomy surgery is postoperative stability and relapse. Currently, there is no consensus on the ideal fixation technique, or how prognosis is affected by mandibular height and length. The aim of the present study was to assess stress distribution on the fixation units and the bone after sagittal split ramus osteotomy and determine the contributions of different mandibular body heights and lengths. MATERIALS AND METHODS: Sagittal split ramus osteotomy and mandibular advancement were simulated in different height/length models prior to fixation using a miniplate, hybrid, or inverted L system using finite element analysis. The greatest and least amount of stress was generated using the miniplate, and inverted L system, respectively. RESULTS: The highest tension and compression in the bone was measured in the miniplate system. While the inverted L system generated less stress in the fixation units than the hybrid system, the hybrid system caused less stress in the bone and lower displacement values compared to other systems. An increase in length, and a decrease in height, both promoted stress, however, the difference was greatest in the former. CONCLUSION: Based on our results, when sagittal split ramus osteotomy is planned for a rather long or thin mandible, using the hybrid system for fixation is recommended.

Effects of maxillomandibular fixation and rigid internal fixation on pulmonary function in patients with mandibular fractures.

Closed reduction and maxillomandibular fixation (MMF) is associated with airway obstruction. The ventilatory effect of open reduction and rigid internal fixation (ORIF) as an alternative treatment has not been determined. The aim of this study was to compare the effects of MMF and ORIF on pulmonary function (PF) in patients with mandibular fractures. Using a computer-generated simple randomization protocol, 40 eligible participants were allocated to MMF and ORIF treatment groups. PF tests were done preoperatively and at 24hours, 1, 6, and 7 weeks postoperative in all participants in both groups, using a portable office spirometer (Spirobank G). Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, and peak expiratory flow rate (PEFR) were determined. At 6 weeks postoperative, PF tests were performed after the release of MMF. PF tests in the MMF and ORIF groups were similar preoperatively. At 24hours postoperative, FEV1/FVC was significantly lower in the MMF group than in the ORIF group (p<0.001). Values of FEV1 (p=0.022), FEV1/FVC (p=0.001) and PEFR (p<0.001) were significantly lower in the MMF group than in the ORIF group at 1 week postoperative. While MMF negatively impacted on PF, ORIF had no adverse effect on PF.

Safety and feasibility of a new 3D printing template designed for bilateral anterior cervical transpedicular screws placements / 中国组织工程研究

BACKGROUND: Anterior cervical transpedicular screws placement technique provides nice mechanical stability and is of very promising application prospects. However, the technology is difficult to operate and has a high risk, and has not been widely used. OBJECTIVE: To design a new three-dimensional (3D) printing template for bilateral anterior cervical transpedicular screws placements and assess its feasibility and safety in anterior cervical pedicle screw placement. METHODS: Six cadaveric cervical specimens, including three males and three females, were used in this experiment. Data of thin layer CT scanning of the specimens were saved in DICOM format and then imported into Mimics 17.0 software. Following 3D reconstructions of the cervical spine, guiding holes for C3-C7 bilateral anterior cervical transpedicular screws trajectories were designed; pedestals for the guiding holes were then designed via reversely thickening the bony structure of the anterior and 1/2 superior-anterior surface of vertebral body, and 1/2 anterior joint surface of bilateral processus uncinatus. Practical objects of the templates were obtained via 3D printing and were then used for guiding bilateral anterior cervical transpedicular screws replacements from C3 to C7. CT scanning was conducted again and the accuracy of anterior cervical transpedicular screws replacements was evaluated from sectional CT images. The difference of deviational angles on axial plane (α1, α2) and sagittal plane (β1, β2) between real and simulated trajectories were compared in Mimics 17.0 software. RESULTS AND CONCLUSION: (1) A total of 60 anterior cervical transpedicular screws were successfully inserted; 57 screws were completely located in pedicles and were judged as grade 0, representing an accuracy of 95.0%. The other three anterior cervical transpedicular screws perforated from pedicles, including grade 1 perforation in two screws (3.3%) and grade 2 perforation in one screw (1.7%). (2) By comparing real and simulated trajectories, the medical and lateral deviational angles were (0.867±0.787)° and (0.783±0.792)°, respectively (P > 0.05); the cephalad and caudal deviational angles were (1.362±1.380)° and (1.314±1.300)°, respectively (P > 0.05). (3) With the help of the 3D printing template designed in this study, bilateral anterior cervical transpedicular screws replacements could be smoothly carried out at high inserting safety.

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.

Análise biomecânica de diferentes tipos de fixação em osteotomia sagital do ramo após diferentes avanços e alterações do plano mandibular: um estudo com elementos finitos / Biomechanical analysis of different types of fixation in sagittal ramus osteotomy after different advances and changes in the mandibular plane: a study with finite elements

O objetivo deste trabalho foi avaliar, por meio de um estudo com análise em elementos finitos, as tensões de superfície presentes na cortical óssea mandibular e no material de síntese, assim como avaliar a resistência da fixação ao deslocamento após a osteotomia sagital do ramo mandibular (OSRM) quando da realização de diferentes avanços mandibulares com e sem alteração do plano mandibular. Foram obtidos modelos virtuais tridimensionais de uma mandíbula e planejados avanços de 6 e 12mm com avanço linear, assim como associados ao giro horário e anti-horário do plano mandibular. Cada conjunto foi, então, fixado com uma ou duas placas monocorticais do sistema 2.0 dispostas horizontalmente com 4 parafusos em cada placa. Ao todo, foram construídos 12 modelos que foram então submetidos a uma carga vertical linear na região de incisivos centrais em incrementos de 50N até o limite máximo de 500N. Os resultados demonstraram que os avanços de 12mm estão associados a maiores tensões nas corticais ósseas e no material se síntese. Também foi possível concluir que os modelos fixados com duas placas apresentaram valores menores de tensão no material de síntese em comparação aos modelos fixados com uma placa. A mudança do plano mandibular no sentido anti-horário nos avanços de 6 mm, fixados com 1 ou 2 placas, aumentou a tensão no material de síntese, o que não ocorreu nos avanços de 12 mm. Esses resultados podem auxiliar os cirurgiões na tomada de decisão clínica diária (AU).

The aim of the present paper was to evaluate, via a finite element analysis, the tensions on the cortical bone and the plating system, as to evaluate mandibular resistance after the sagittal split ramus osteotomy with different mandibular advancements and mandibular plane movements. 3D mandibular models were obtained and a 6mm and 12mm advancement was planned associated with linear, clockwise or counter clockwise rotation of the mandibular plane angle. Each model was then fixed with one or two plates of the 2.0mm system and held with 4 monocortical screws at each side. A total of 12 models were built and they were subjected to a vertical load in the incisors region ranging from 50N to 500N in 50N increments. Results have shown that the 12mm advancement was associated with a higher tension in the cortical bone and plate surface. It was also concluded that the models fixed with 2 plates presented lower values of tension on the plates in comparison with the models fixed with a single plate. Counter clockwise rotation of the mandibular plane angle in the 6mm advancement, fixed with 1 or 2 plates, brought more tension to the plates, which did not occur in the 12mm advancements. These results may aid surgeons with decision making on a daily basis (AU).

Application of three-point rigid internal fixation technique in reduction malarplasty / 中华医学美学美容杂志

Objective To evaluate the effect of three-point rigid internal fixation technique in reduction malarplasty for prominent malar complex.Methods From January of 2014 to January of 2017,45 patients with prominent malar complex were treated with double L shape osteotomy combined bony Z plasty and three-point rigid internal fixation for prominent malar complex.The preoperative and postoperative photographs were taken to monitor the contour improvement,the adverse effects were recorded,and 3D CT was used to assess the bone union situation at 6 months after operation.Results All the wounds got primary intention healing and no severe complication occured in perioperative period.3D CT showed good bone recovery 6 months after operation.Postoperative appearance of all cases showed that the width of middle face was efficiently reduced.All patients expressed high levels of satisfaction.Conclusions Reduction malarplasty with three-point rigid internal fixation for prominent malar complex is an effective and safe method for the treatment of prominent malar complex.

Role of 1.5 mm microplates in treatment of symphyseal fracture of mandible: A stress analysis based comparative study.

AIMS AND OBJECTIVES: To perform comparative finite element analysis (FEA)for 2.0 mm standard miniplate and 1.5 mm microplate in isolated symphyseal mandibular fractures. MATERIAL AND METHOD: Two FE models of mandible were developed and symphyseal fracture was created in both of them. Each fractured model was reduced and fixed using two mini plates and two microplates, respectively according Champ's principle. Stresses thus developed in the plates after application of masticatory load were observed in the models. RESULTS: Results of the study indicated there was no significant difference in the stresses developed in either of the bone plating system. CONCLUSION: 1.5 mm Microplates can be used in place of 2.0 mm miniplates in isolated symphyseal fractures of the mandible.

Biomechanical evaluation of different osteosynthesis methods after mandibular sagittal split osteotomy in major advancements.

The aim of this study was to assess the biomechanical stability of six different osteosynthesis methods after sagittal split osteotomy. Sixty polyurethane hemimandibles were divided into two groups, with six subgroups in each. After 10-mm advancement of the distal segment (group 1) and 10-mm advancement combined with 20° counterclockwise rotation (group 2), the bone segments were fixed using 2.0-mm plates/screws as follows: subgroup A, one conventional straight plate; subgroup B, two conventional straight plates; subgroup C, one conventional sagittal plate; subgroup D, one locking straight plate; subgroup E, two locking straight plates; subgroup F, one locking sagittal plate. The hemimandibles were tested for compressive strength by three-point biomechanical test, until there was 3mm of displacement between the segments. The fixations showed better performance in group 1 than in group 2 in all cases, with statistical significance for subgroups A, C, and D. In both groups, the use of two straight miniplates showed the most resistance, followed by the sagittal miniplates. However, in counterclockwise rotations, no statistically significant difference was found between two conventional straight plates and the sagittal locking plate. This study shows that the use of two plates is the form of fixation with the minimum displacement. If the clinician opts to use one plate, a sagittal plate is the best alternative.

Application of Segmental Design Principles in the Small Incision Approach Rigid Internal Fixation for the Treatment of Maxillofacial Fractures / 医学研究杂志

Objective To explore the application effects of segmental design principles in the small incision approach rigid internal fixation for the treatment of maxillofacial fractures.Methods With a retrospective study,from September 2012 to April 2016,172 patients with maxillofacial fractures were selected as the research object in our hospital.All the patients were divided into the observation group of 100 patients and control group of patients according to the different treatment methods.Two groups were treated with mall incision approach rigid internal fixation.The observation group were given the preoperative design based on the segmental design principles.The other operation process were similar with the control group.Results All patients were completed the operation,the fracture were healed by Ⅰ stage.The postoperative 3months of total effective rates of the observation group and the control group were 98.0％ and 83.3％.The total effective rate of the observation group was significantly higher than that of the control group (P ＜ 0.05).The postoperative 3months of infection,nerve injury,salivary fistula,screw loosening and complication rate in the observation group was 3.0％,so that was 20.8％ in the control group,the observation group was significantly lower than the control group (P ＜ 0.05).The postoperative 3months of occlusal relationship and normal rates of the observation group were 99.0％ and 98.0％,respectively.The control group was 93.1％and 90.3％,respectively.There were between the two groups statistically significance difference(P ＜ 0.05).Conclusion The segmental design principles in the small incision approach rigid internal fixation for the treatment of maxillofacial fractures can improve the therapeutic effect,reduce the incidence of postoperative complications,improve the occlusal relationship with normal mouth opening rate.It is an ideal method for the treatment of maxillofacial fracture.