Computerized analysis of resorbable polymer plates and screws for the rigid fixation of mandibular angle fractures.

PURPOSE: This computer-based study used finite element analysis (FEA) to assess whether rigid fixation by resorbable polymer plates and screws can provide the required stiffness and strength for a typical mandibular angle fracture. MATERIALS AND METHODS: Two separate 3-dimensional FEA models of the mandible were generated using 8-noded hexahedral elements. The jaw segments in 1 model were fixed with titanium plates and screws as those in common use today. The jaw segments in the other model were fixed with resorbable polymer plates and screws as used in a developmental product currently in trials. A commercial finite element solver was then applied to this mesh to compute stresses and bone interfragmentary displacements for both titanium fixation and resorbable fixation. Calculated displacements were compared with each other and to established norms for healthy bone regrowth. Calculated stresses were compared with the yield strength of each material. Finally, overall stress patterns in the fractured mandibles were compared with each other. RESULTS: The study results indicate that titanium fixation more rigidly fixes the 2 bone segments in relative position. However, they also show that resorbable polymers provide sufficient stiffness to meet currently established norms for fracture immobility. Furthermore, the analyses show that resorbable polymers are capable of withstanding the stresses generated by the bite loads of postsurgical patients. The results indicate that mandibles, fixed with either titanium or resorbable materials, show nearly identical stress patterns. CONCLUSIONS: The resorbable polymer-based plates and screws tested in this investigation are of adequate strength and stiffness for their successful application to the rigid fixation of mandibular angle fractures.     

Stability of fixation methods in large mandibular advancements after sagittal split ramus osteotomy: an in vitro biomechanical study

Sagittal split ramus osteotomy (SSRO) with large mandibular advancements is a common surgical procedure and could be indicated for patients with sleep apnoea. As a large variety of fixation methods is used for the stabilisation of SSRO, a biomechanical test model was used to analyse which fixation technique was most stable. For this in vitro study, 80 polyurethane hemimandibles with a prefabricated SSRO were used as substrates. Loads in Newtons were recorded at displacements of the mandibular incisive edge at 1 mm, 3 mm and 5 mm. The samples were divided into two groups: mandibular advancements of 10 mm and 15 mm. In both groups, four fixation techniques were used: (A) one four-hole miniplate; (B) two four-hole miniplates; (C) one four-hole miniplate plus one bicortical screw; and (D) three bicortical screws in an inverted-L arrangement. In group 1, three bicortical screws resulted in the best stability, and in group 2, two miniplates resulted in the best stability. The use of two miniplates did not show significant differences between both groups. Other fixation methods showed more stability with 10 mm advancements. This study therefore suggests that in SSRO with advancements exceeding 10 mm, the use of two miniplates is the optimal means of providing rigid fixation.     

Three-dimensional titanium miniplates for fixation of subcondylar mandibular fractures: Comparison of five designs using patient-specific finite element analysis

Purpose

The purpose of the current study is to compare the performance of five designs of three-dimensional titanium miniplates (lambda, strut, delta, rhombic and trapezoid) for fixation of subcondylar mandibular fracture.

不同程度老年人萎缩性无牙颌下颌骨骨折的内固定方式选择及相关生物力学分析

目的:比较3种不同程度萎缩性无牙颌下颌骨骨折的不同内固定方式及其效果。方法:构建不同程度的萎缩性无牙颌下颌骨体部骨折治疗模型,进行三维有限元分析,比较相同应力条件下骨折段位移的改变以及钛板的应力分布情况。结果:下颌骨Ⅲ度萎缩,采用1块2.0 mm 4孔钛板在下颌骨上缘进行固定,其骨折处移位较其余6种工况明显增大;相同萎缩程度的下颌骨,采用重建板固定比采用其他内固定方式骨折断端位移明显减少。Ⅲ度萎缩的下颌骨采用小型钛板固定,钛板所受应力分别接近及超过钛板的屈服极限。结论:对于Ⅰ度萎缩的无牙颌下颌骨骨折病例,下颌骨外侧双板固定以及下颌骨下缘重建板固定均能取得较为满意的固定稳定性,对于Ⅱ及Ⅲ度萎缩的无牙颌下颌骨骨折病例,下颌骨下缘重建板固定可以获得更好的固位稳定性。     

Assessment of biomechanical properties of specially-designed miniplate patterns in a mandibular subcondylar fracture model with finite element analysis and a servohydraulic testing unit

The aim of our study was to compare the biomechanical stability of three different systems used to fix mandibular condylar fractures on synthetic polyurethane mandibles using a servohydraulic testing unit and finite element analysis (FEA). We measured the resistance to displacement loads causing 1.75 and 3.5 mm displacements of the fragments, and the maximum resistance values before failure of the fixation system in 30 condylar necks of 15 polyurethane mandible models. The three subgroups investigated were arranged as a triangular plate (n = 10), a quadrangular plate (n = 10), and a straight miniplate (n = 10). The most successful fixation pattern was achieved with two straight four-hole miniplates. However, the triangular plate can easily be applied as a second option by an endoscopic approach. The rectangular plates showed no success in mandibular condylar fractures.     

Biomechanical comparison of plating techniques for fractures of the mandibular condyle

We compared the biomechanical behaviour of various rigid internal fixation techniques for treatment of fractures of the mandibular condylar process. Fifteen sheep hemimandibles were used to evaluate three bicortical plating techniques. A custom-made 3-point biomechanical test model was used for the samples. Each group was tested with compression forces by an Instron Lloyd LRX machine. The resistance to forces (N) that caused displacements of 1.75 and 3.50mm were compared using the Instron software programme and displacement graphics. There were no significant differences among the three groups for displacements of 1.75 and 3.50mm. Our study showed that the titanium miniadaptation plates, minicompression plates, and the absorbable miniplates did not differ significantly in their biomechanical behaviour.     

Fixation methods in sagittal split ramus osteotomy: a systematic review on in vitro biomechanical assessments

The aim of this systematic review was to assess the stability of rigid internal fixation (RIF) techniques in sagittal split ramus osteotomy (SSRO) based on in vitro biomechanical assessments, with particular interest in large mandibular advancements. In general, RIF methods can be divided into three groups: bicortical screws, miniplates, and a combination of the two. An electronic search of the PubMed, CINAHL, and Embase databases was performed, and studies published between January 2003 and March 2018 were screened for inclusion. Comparative studies with an in vitro experimental design, using biomechanical assessments to measure the stability of RIF methods in SSRO, were included. Of 104 unique studies identified in the initial search, 24 were included. Twenty-two of these 24 studies analyzed an advancement of the mandible of 7 mm or less. The use of a single four-hole or six-hole miniplate was less stable than the use of bicortical screws, hybrid techniques, double miniplates, or grid plates. Two studies analyzed advancements of 10 mm, for which two miniplates placed in parallel and a grid plate showed most stability. Although there was agreement between studies with regard to results, more biomechanical studies are required to quantify the stability of fixation methods in larger mandibular advancements.     

An in-vitro evaluation of a novel design of miniplate for fixation of fracture segments in the transition zone of parasymphysis-body region of mandible using finite element analysis

The mandibular parasymphysis and body regions are highly dynamic areas. They are constantly subjected to both occlusal and muscular forces. Fractures at this transition zone of the parasymphysis and body region thus represent a special pattern that creates a dilemma for the surgeons — whether to use one miniplate fixation or two miniplates as per Champy's guidelines. Mental nerve paresthesia is a very common complication due to dissection and stretching of the mental nerve in this region. Hence, an in-vitro research study of a novel twin fork design of miniplate is performed, which evaluates the biomechanical behavior using computerized finite element analysis. A comparison is carried out with the conventional design. The results show that the twin fork miniplate produces the lowest stresses — 23.821 MPa — and the least total structural deformation after applying the maximum occlusal bite force. This study concludes that the newly designed miniplate is superior in terms of stability because it shows the least structural deformation, and produces the lowest equivalent stresses on application of maximal occlusal forces. An additional advantage is the preservation of the mental nerve during the plating procedure because the broad end of the Y shape allows atraumatic positioning of the miniplate and hence the fixation of fractured segments.     

下颌骨双侧升支矢状劈开坚强内固定的生物力学研究

目的:研究下颌骨升支矢状劈开小型钛板和双皮质固位螺钉内同定生物力学特性,为临床提供理论上的指导。方法:用螺旋CT断层扫描技术及ANSYS有限元软件在计算机上建立下颌骨升支矢状劈开小型钛板及3种双皮质同位螺钉内固定的三维有限元模型;计算4种固定方法在三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、劈开处的位移从大到小排列顺序为:2mm双皮质同位螺钉直线形内固定、小型钛板内固定、2mm双皮质同位螺钉倒"L"形内固定、2.7mm双皮质固位螺钉倒"L"形内固定。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:下颌骨双侧升支矢状劈开双皮质固位螺钉倒"L"形内固定的固定稳定性要强于小型钛板内固定;直线形内固定固定稳定性相对较差。前牙咬合对同定的不良影响很大,应尽量避免。     

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.     

Feasibility of carbon-fiber-reinforced polymer fixation plates for treatment of atrophic mandibular fracture: A finite element method

The objective of this study was to conduct a computer assessment of the biomechanical stability of locking fixation plates of different thicknesses, made of titanium alloy and carbon-fiber- reinforced polyetheretherkotone (CFR-PEEK) in Class III atrophic mandibular fractures. Class III atrophic mandibular models were constructed using three-dimensional finite element models. After simulation of fracture on the left side, plates with different thicknesses (1.0, 1.5, 2.0, and 2.5 mm) were adapted to the models and three locking screws on each side of the fracture were used for fixation. Titanium alloy and CFR-PEEK material properties were assessed for all plate models. Von Mises stress values decreased gradually with an increase in plate profile thickness. Von Mises stress values for screws and plates were lower in models using CFR-PEEK plates. An increase in plate profile enhanced the load-sharing performance of the fixation systems, with rigid titanium alloy plates sharing the load among the screws more evenly. 1.0 mm, 1.5 mm, and 2.0 mm CFR-PEEK plates produced strain values of 2–10%, which promote proper healing via formation of callus in the fracture line. In terms of investigated biomechanical parameters, and with a Young's modulus similar to that of cortical bone, CFR-PEEK materials appear to be suitable for the treatment of atrophic mandibular fractures.     

下颌角稳定型骨折坚强内固定后对髁突影响的有限元分析

目的:分析下颌角稳定型骨折坚强内固定以后对髁突应力分布的影响,探讨下颌角骨折引起颞下颌关节紊乱病的生物力学机制。方法:采用螺旋CT技术、计算机图形图像处理功能、有限元处理分析软件Ansys建立下颌骨正常有限元模型及下颌角骨折有限元模型并模拟坚强内固定,定量对比分析髁突应力分布状况。结果:患侧髁突表面应力分布发生了明显改变,尤以髁突前斜面和嵴顶部最为显著;健侧髁突表面应力分布未发生明显改变。结论:下颌角稳定型骨折在外斜线行坚强内固定后髁突表面应力分布发生了异常改变,破坏了颞下颌关节的生物力学环境,可能是下颌骨损伤后颞下颌关节紊乱病的致病原因之一。     

上部结构材料对无牙下颌种植固定修复影响的三维有限元分析

目的:通过三维有限元方法探讨上部结构材料对无牙下颌种植固定修复生物力学的影响,为无牙颌修复治疗提供参考。方法:构建无牙下颌种植固定修复三维有限元模型,用6种牙科材料（纯钛、钴铬合金、金合金、氧化锆、聚醚醚酮及碳纤维增强聚醚醚酮）分别对种植上部结构进行赋值,得到6种模型,模拟斜向加载,对种植体、周围骨组织及上部结构进行应...     

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).

Segmental stability of resorbable P(L/DL)LA-TMC osteosynthesis versus titanium miniplates in orthognatic surgery

After two decades of the use of resorbable miniplates, new polymer compositions for resorbable osteosynthesis are still being developed to make the handling and outcome of operations even more predictable and give higher stability to the repositioned segments. This study investigates a new resorbable osteosynthesis system in orthognathic patients.50 patients were treated with P(L/DL)LA-TMC resorbable osteosynthesis and compared to a group of 50 patients treated with titanium miniplates. Segmental stability and relapse were measured comparing preoperative, postoperative and follow-up lateral cephalograms.Throughout this study, resorbables appeared to be as stable as titanium miniplates except in maxillary elongation and mandibular setback. Here, the titanium miniplates showed significantly higher stability than resorbable plates.P(L/DL)LA-TMC osteosynthesis seem to have less strength against compressive forces after maxillary elongation and they are less resistant to the forces the tongue exerts, pressing against the mandible after setback. It can therefore be concluded that the resorbable osteosynthesis can be used in the same situations as titanium miniplates except in maxillary elongation and mandibular setback.     

Analysis of complications in fractures of the mandibular angle--a study with finite element computation and evaluation of data of 277 patients.

AIM: The purpose of this study was to compute the load on different osteosynthesis plates in a simplified model using finite element analysis, and to find out whether miniplates were sufficiently stable for application at the mandibular angle. PATIENTS: Data from 277 patients with 293 fractures of the mandibular angle have been evaluated. METHODS: A computation model using finite elements was established in order to compute mechanical stress occurring in osteosynthesis plates used for fixation of fractures of the mandibular angle. In the second part of this study, the data from all in-patients treated for fracture of the mandibular angle were evaluated retrospectively. Age and sex of the patients, cause of fracture, state of dentition, type of therapy as well as complications were noted. RESULTS: In those tests, both the 1.0 mm miniplate and the 2.3 mm module plate were sufficiently stable. The rate of major complications (requiring revisional surgery with general anaesthesia) amounted to approximately 17% in comminuted fractures, or in non-compliant patients in which primary stability with a single miniplate did not appear sufficient, so that other osteosynthesis methods were used in addition. This rate was considerably higher than that in simple mandibular fractures. Simple fractures of the mandibular angle were just treated with one miniplate following Champy's guidelines strictly. In these fractures the rate of major complications was only 2.3%. CONCLUSION: In comminuted fractures and in non-compliant patients, the use of a stronger osteosynthesis material should be considered while in all other cases application of a single 1.0 mm miniplate was regarded as sufficient for fixation using open reduction.     

An in vitro evaluation of miniplate fixation techniques for fractures of the atrophic edentulous mandible

This study was undertaken to evaluate the biomechanical stability of various miniplate fixation techniques in varying degrees of atrophy and to determine optimal fixation techniques for fractures of the atrophic edentulous mandible. A total of 78 bovine ribs were randomly divided into 13 groups of six each; one non-atrophic group and twelve atrophic groups. Each one of the 13 sets of six ribs was formed based on the vertical dimension (40, 20, 15 or 10 mm) and osteotomized. The segments so produced were then reduced and fixed using various miniplate fixation techniques. The stability of various miniplate fixations in ribs showing varying degrees of atrophy (10, 15 and 20 mm) was compared with that of one miniplate fixation in non-atrophic ribs (40 mm), used as a standard. Atrophic groups utilizing single miniplate were significantly less stable than the non-atrophic group, whereas atrophic groups fitted with double miniplates, such as two 4-hole or two 6-hole miniplates, were significantly more stable than the non-atrophic group. The two miniplate fixation technique is recommended for the provision of adequate fracture site stability when open reduction is indicated in cases of atrophic edentulous mandibular fractures.     

A new biomechanical model for evaluation of fixation systems of maxillofacial fractures

The aim of this study was to develop a new type of biomechanical model for biomechanical researches of maxillofacial fractures and then evaluate it. Twenty synthetic polyurethane maxillary and mandibular models were used to simulate the mandible and maxilla. Springs were used to represent the forces of masseter, medial pterygoid, temporalis, and lateral pterygoid muscles acting on the models. Four masticatory conditions, namely clenching in the intercuspal position (ICP), incisal clenching (INC), left unilateral molar clenching (L-MOL, contralateral side of fracture) and right unilateral molar clenching (R-MOL, fracture side) were simulated. The strain on a miniplates placed across a simulated fracture was measured using strain gauges attached to the plate surface. During INC and L-MOL, the strain on the miniplates confirmed the findings of Champy. The upper miniplate was subjected to tension force and the lower miniplate to compression. When the bite point moved to the fracture, the tension–compression zone reversed, with the upper miniplate relatively compressed and the lower miniplate tension. During ICP, the tension–compression zone changed again, with both miniplates tension. In conclusion, we have successfully developed a model which is much closer to physiological conditions than models used previously. It is reliable and useful for biomechanical tests of mandibular fractures. Models including soft tissue need developing to further understand fracture healing biomechanics.     

双侧下颌支矢状劈开坚固内固定的三维有限元分析

目的:研究双侧下颌支矢状劈开术应用自身增强型可吸收内固定系统和小型钛板坚固内固定的生物力学特性,为临床应用提供理论指导。方法:采用螺旋CT断层扫描技术及Ansys有限元软件,在计算机上建立下颌支矢状劈开术可吸收板和钛板坚固内固定的三维有限元模型;计算4种固定方法在3种咬合状态内固定系统的应力以及骨劈开处的位移,比较固定效果以及不同咬合状态下对固定稳定性的影响。结果:在相同咬合状态下,骨劈开处的最大位移基本相似。内固定系统的最大应力值为钛板大于可吸收板,双板大于单板,双板中上板大于下板。相同固定方式下,内固定系统的最大应力值及骨劈开处的最大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:双板固定时的应力遮挡作用大于单板固定。坚固内固定板材料对应力遮挡有影响,钛板的应力遮挡作用大于可吸收板。单板固定时位置应偏上缘,前牙咬合对内固定系统的不良影响较大,应尽量避免。     

坚固内固定术治疗下颌骨骨折的临床疗效研究

目的 :评价小型钛板坚固内固定术对下颌骨骨折的临床疗效。方法 :对 10 6例下颌骨骨折用小型钛板做坚固内固定术 ,术后作即刻及随访临床综合效果评价 ,包括骨折复位准确性、固定稳定性、骨折愈合、伤口愈合、咬合关系等。结果 :10 6例术后感染 3例 ,缝线局部裂开 5例 ,咬合关系有 3例不正常 ,有 4例发生局部咬合关系不良 ,2例发生偏向咬合。其余均Ⅰ期愈合 ,咬合关系正常 ,术后张口度 >36mm。结论 :小型钛板做下颌骨坚固内固定是一种现代而符合生理的治疗方法 ,较传统治疗有明显的优点