下颌角骨折坚强内固定的生物力学分析

目的 比较下颌角骨折后两种不同的内固定方法对其应力分布的影响。方法 采用成人干燥无牙下颌骨,建立由咬肌、颞肌、翼内肌和翼外肌4组肌肉共同加载,由硅橡胶模拟颞下颌关节结构功能状态下的下颌骨机械力学模型。采用电阻应变片的测量方法,分析不同坚强内固定方式,即仅在下颌角上缘张力带固定一个小型接骨板和在下颌角下缘附加固定一个小型接骨板对下颌骨应力分布的影响。结果 两种固定方法下健侧的应力分布与骨折前均无显著性差异（P＞0.05）,但是仅在下颌角上缘固定一个小型接骨板将使患侧下颌骨下缘呈张应力趋势,造成应力轨迹的中断。结论 两种固定方法均可以恢复健侧的应力轨迹,但是要获得骨折区域充分的稳定性,固定两个小型接骨板是必要的     

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.     

Biomechanical evaluation of malleable noncompression miniplates in mandibular angle fractures: an experimental study

The purpose of this experimental study was to test the reliability of a single malleable titanium miniplate using Champy's method of fixing fractures of the mandibular angle. Eighteen sheep hemimandibles were used to evaluate 2 plating techniques. The groups were tested with either a single non-compression titanium miniplate or a single malleable titanium miniplate. A cantilever bending biomechanical test model was used for the samples. Each group was tested with vertical forces using a servohydraulic testing unit. The displacement values in each group at each 10N stage up to 90N were compared using 2-way analysis of variance (ANOVA). The displacement values for the 2 groups differed significantly (p<0.01). The variance analyses showed that the biomechanical behaviour of a single non-compression miniplate was better than that of a single malleable miniplate. The non-compression miniplate fixed by screws had greater resistance to occlusal loads than the malleable plate fixed by screws, and the malleable plate alone was not sufficient to withstand the early postoperative bite force.     

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.     

Biomechanical evaluation of a new design titanium miniplate for the treatment of mandibular angle fractures

The optimal management of mandibular angle fractures remains controversial. The aim of this experimental study was to test the stability and resistance to mechanical force of a new titanium miniplate design. Thirty fresh sheep hemimandibles, sectioned at the angle region, were used to evaluate two plating techniques. One group received fixation via a new design single non-compression titanium miniplate and the second group via a six-hole straight non-compression titanium miniplate. A custom-made biomechanical test model was used for the samples. Each hemimandible was subjected to compressive and tensile forces using an Instron machine. The biomechanical forces (N) that caused 4-mm displacement or fixation loosening were compared. Comparison between the groups showed that fixation with the new design miniplate had more resistance to lateral compression forces than with a six-hole straight miniplate (P < 0.009). Moreover, the new design miniplate fixation displayed more resistance to vertical compression and tensile forces (P > 0.46 and P > 0.61, respectively). The study demonstrated that mandibular fracture fixation with the new design non-compression titanium miniplate offered greater resistance to lateral displacement forces and may also provide increased resistance to vertical compressive and tensile forces than a conventional six-hole straight miniplate.     

口内途径坚强内固定术治疗下颌骨骨折29例报告

目的 :评价口内途径坚强内固定术及术中暂时性小环结扎治疗下颌骨骨折的效果。方法 :对 2 9例 47处下颌骨体部骨折先作两侧磨牙区和切牙区三点式颌间小环结扎 ,骨折线两侧作牙间结扎 ,初步恢复下颌骨的弓形和咬合关系后 ,自下颌前庭沟作切口 ,显露骨折处并复位后进行小型钛板坚强内固定术。术毕拆除颌间结扎 ,恢复下颌运动。分别于术后第 1d和 90d进行临床和X线检查 ,评价其咬合关系、骨折复位及愈合情况。结果 :2 9例47处下颌骨体部骨折均获得良好的复位和骨性愈合 ,咬合关系良好 ,无并发症。结论 :口内途径小型钛板坚强内固定术可对下颌骨体部骨折进行良好的固定 ,获得满意的咬合关系。     

Biomechanical evaluation of magnesium plates for management of mandibular angle fracture

The aim of this study was to evaluate the efficacy of magnesium plates for the management of fractures of the mandibular angle. Fresh sheep hemimandibles were divided into 7 groups and a biomechanical cantilever bending test was used for the groups: Group 1 included fractured hemimandibles fixed at the angle with a single 1mm magnesium miniplate; Group 2 had fixation with a 1mm double magnesium miniplate; Group 3 used a 2mm thick single magnesium miniplate; Group 4 used double 2mm magnesium plates; Group 5 each had a single 1mm thick titanium plate; Group 6 used 1mm thick double titanium plates; and Group 7 comprised intact hemimandibles. Each group was tested using universal testing machine yield loads; yield displacements and stiffness were compared using one way analysis of variance (ANOVA) Group 1 (1mm single magnesium plate) and Group 2 (1mm double magnesium plates) showed lower stability than other groups, while the 2mm magnesium plate showed stability similar to the corresponding 1mm titanium plate. Pure magnesium has good mechanical properties and when it is designed properly it can be used for the management of mandibular fracture.     

下颌骨骨折生物接骨内固定的三维有限元分析

目的:用计算机对生物可吸收板在下颌骨骨折内固定中进行三维有限元的分析,来估计生物可吸收板在典型的角部和体部骨折时能否提供所需的强度和力度。方法:在ANSYS6.0软件中建立下颌骨角部和体部骨折的内固定三维有限元模型,施加载荷后,分别计算角部、体部骨折钛板单、双板及生物可吸收板单、双板固定时,骨折段位移、骨断层的应力,固定板的应力。结果:角部和体部骨折钛板单、双板固定,生物可吸收板双板固定时骨折段位移、骨断层的应力,固定板的应力均在安全范围内;角部骨折生物可吸收板单板固定时骨折段位移超出安全范围;体部骨折生物可吸收板单板固定时固定板的应力超出安全范围。结论:生物可吸收板双板固定在下颌骨角部和体部骨折早期时可以提供骨折愈合的条件。     

Resorbable plates for the fixation of mandibular fractures: a prospective study.

PURPOSE: The hypothesis for this prospective evaluation is that resorbable plates are equal to the performance of titanium 2-mm plates, regarding healing of the fracture with bone union and restoration of function. To prove this hypothesis, specific end points will be compared with literature norms for titanium 2-mm miniplate rigid fixation. The primary end point variable for this analysis is the union of the fracture and return to normal function. Secondary end point variables included the incidence of complications such as infection, malunion with malocclusion, soft tissue dehiscence, the need for revision surgery, specific technical challenges, operative time, and the learning curve for the surgeon. PATIENTS AND METHODS: This prospective study consisted of a sequential enrollment of 50 fractures that met the inclusion criteria of having a fracture of the mandibular body, symphysis, angle, or ramus, and required an open reduction and internal fixation for stabilization and repair. The resorbable plates and screws used consisted of an amorphous injection molded copolymer of L-lactide/D-lactide/trimethylene carbonate (Inion CPS system, Tampere, Finland). Data were collated and compared with literature norms for titanium plates and also compared with nonrigid fixation data from a prospective study performed on a similar population in the same institution. RESULTS: Clinical and radiographic evaluation indicated union of all fractures at the eighth follow-up visit. Three sites (6%) noted to have clinical signs of infection were treated immediately upon presentation, with fracture union by 8 weeks. There was no need for revision surgery in this series of patients; 12 screw heads fractured during screw placement and were immediately replaced without significant fracture sequelae. CONCLUSION: Based on this limited series of patients, the hypothesis formulated for this study was validated.     

口内切口与牵引钉暂时颌间刚性牵引固定治疗下颌骨骨折45例分析

目的:评价术中利用颌间牵引螺丝暂时牵引,经口内切口进行整复并坚强内固定治疗45例下颌骨骨折的效果。方法:对45例54处下颌体及下颌角区线性骨折,先分别在上、下颌中切牙之间、尖牙与第一前磨牙之间、第一与第二磨牙之间的根向植入颌间牵引螺丝,骨折复位后,进行颌间结扎固定,恢复咬合关系及下颌骨的弓型。自下颌前庭沟、翼下颌皱襞切开黏骨膜,显露骨折处并复位后,在张力线上用小型钛板进行坚强内固定术。术毕拆除颌间结扎,7d后将颌间牵引螺丝拆除。分别于术后第1天和第90天进行临床和X线检查,评价其咬合关系、骨折复位及愈合情况。结果:45例54处下颌骨骨折均获得良好的复位和骨性愈合,咬合关系良好,无明显并发症。结论:经口内途径行小型钛板坚强内固定术,结合颌间牵引螺丝暂时刚性牵引结扎,对下颌体及下颌角骨折的整复固定和功能恢复效果良好。     

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。     

Resorbable mesh as a containment system in reconstruction of the atrophic mandible fracture.

PURPOSE: The purpose of this article is to introduce the use of a resorbable material (L-lactide, Co DL-lactide) to help contain the bone graft used during the reconstruction of the edentulous atrophic mandibular fracture. TECHNIQUE: After the mandibular fracture was reduced and fixated with a large reconstruction plate, the resorbable mesh was contoured with scissors and a hot water bath. The mesh was secured into position with 1.5-mm tacks to the inferior border or buccal cortical plate of the mandible. The material was then filled with particulate bone graft harvested from the medial aspect of the anterior iliac crest. RESULTS: Two patients had augmentation of the superior aspect of the mandible and one patient had augmentation of the inferior aspect of the mandible. All patients were augmented at least 10 to 12 millimeters. The mean follow-up was 25 months. All went on to heal to complete bony union. CONCLUSION: This material can be used as a containment system when bone grafting the edentulous atrophic mandible fracture.     

Mandibulotomy fixation: a laboratory analysis.

PURPOSE: Mandibulotomy is an access osteotomy technique associated with significant complications. Critical evaluation of available fixation systems is required to aid in the selection of the most stable fixation method. This study was designed to provide data on the stability of traditionally used plating configurations and a low-profile 2.0-mm locking plate (mandibular locking plate, Synthes MLP; Synthes Maxillofacial, Paoli, PA). MATERIALS AND METHODS: An in vitro red oak model was used to evaluate the stability provided by the study fixation devices. Five groups were studied as follows: group 1, two 4-hole 2.0-mm nonlocking miniplates; group 2, two 4-hole 2.0-mm mandibular locking plates; group 3, one 6-hole 2.0-mm mandibular locking plate; group 4, one 6-hole 2.4-mm nonlocking rigid plate; and group 5, control (uncut red oak blocks). Each specimen was tested with vertical loads applied over the osteotomy site. The force-versus-displacement behavior was recorded for each specimen and analyzed statistically. RESULTS: Plate type and configuration affected the resistance to vertical peak load (kilogram/force [kgf]) and the fixation stiffness (kgf/mm). The greatest peak load (58.92 kgf) and stiffness (7.07 kgf/mm) was found with group 2 specimens. The differences in system stiffness were statistically significant (P <.05), as were the peak loads for groups 1, 2, and 3. The control group (nonosteotomized red oak) had markedly higher values of peak load and stiffness (484 kg and 83 kg/mm, respectively). Group 2 specimens exhibited increased resistance to flexion. CONCLUSIONS: Two 2.0-mm locking plates provided the greatest resistance to vertical load.     

Locking versus non-locking plating system in the treatment of mandibular fractures: A randomized comparative study

To evaluate fracture stability and complications such as infections, need for hardware removal, malunion, and nonunion when using 2.0-mm locking plating system in fixation of mandible fractures and to compare these to those associated with the 2.0-mm non-locking plating system.A prospective clinical study was conducted in a cohort of mandible fracture patients who were randomly assigned to two groups. Patients in the non-locking group were treated with 2.0-mm non-locking plating system, and those in locking group were treated with 2.0-mm locking plating system. Fracture stability, need for maxillomandibular fixation (MMF) and postoperative complications were assessed and compared.A total of 60 patients (30 in each group) were recruited. Significant differences were found between the two groups with respect to postoperative fracture stability (P = 0.001) and need for MMF (P = 0.005). Multivariate analysis revealed that type of fixation was not the only dependent variable which affected fracture stability. There were no significant differences in postoperative complications between the two groups.The 2.0-mm locking plating system provides greater stability and early functional restoration than the 2.0-mm non-locking plating system, with similar rates of postoperative complications. Thus, it can be used as a reliable and effective treatment modality for treating mandibular fractures.     

Miniplate osteosynthesis of fractures of the edentulous mandible

This study was performed to analyze treatment of fractures of the edentulous mandible and to discuss this method in relation to the mandibular height at the fracture site. Fifteen fracture sites in 11 patients with an edentulous mandible were retrospectively examined. These fractures were located: nine fractures in the mandibular body, three in the paramedian region, and three in the mandibular angle. Fractures in a mandible measuring more than 10 mm in the vertical height were treated with one miniplate. Fractures in an extremely atrophic mandible with 10 mm or less were treated using one or two miniplates, also using a modified Champy plate with 1.3 mm in thickness. A mandibular fracture with a height of 5 mm was treated with a combination of a microplate on the buccal side and a miniplate on the inferior border of the mandible with additional direct circumferential wiring. Oblique or splitting fractures were treated with direct circumferential wiring or a Herbert screw, at one fracture site each, respectively. Complications, including infection, fibrous union, nonunion and trismus, were not seen. In one patient, hypesthesia of the lower lip was, however, persistent 1 month after surgery. Miniplate osteosynthesis is the less invasive treatment, and it is suitable for fractures of the atrophic edentulous mandible, except for comminuted or defect fractures. To obtain stable fixation in severely atrophic mandibles, we need to consider the use of two miniplates or a combination with microplates.     

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.     

A comparative biomechanical evaluation of mandibular condyle fracture plating techniques.

OBJECTIVES: The aim of this study was to comparatively evaluate the resistance of 3 plating rigid internal fixation techniques for mandibular condylar process fractures. MATERIALS AND METHODS: Synthetic hemi-mandible replicas made in polyurethane were used to evaluate a control, and 3 mandibular condyle plating techniques using 2-mm system plates and screws. The plating techniques were fixation with a 4-hole plate and 4 6-mm screws, fixation with a 4-hole plate and 4 8-mm screws and fixation with 2 4-hole plates with 4 6-mm screws each. Each group was subjected to linear loading in medial to lateral and anterior to posterior directions by an Instron 4411 servohydraulic mechanical testing unit (Instron Corp, Norwood, MA). Load peak value and peak displacement were measured. Means and standard derivations were derived and compared for statistical significance using an analyses variance (P < .05) and compared by Tukey test. RESULTS: Statistically significant differences were noted between fixation groups for the different mechanical measures evaluated under the different directions of linear loading. The 2-plate fixation system presented better behavior, followed by 1 plate with 4 8-mm screws and 1 plate with 4 6-mm screws. The fixation systems used were more resistant to antero-posterior load and the use of 8-mm screws improved the resistance of the fixation when compared with 6-mm screws only in the antero-posterior test. CONCLUSION: Under the conditions tested the 2-plate fixation system provided the most favorable mechanical behavior. We can suggest that lengthy screws, with bicortical engagement, can increase the stability at fixation of mandibular condylar process fractures.     

下颌骨颏部骨折小型接骨板固定的应变分析

目的探讨下颌骨颏部正中骨折内固定后功能状态下接骨板的应变情况。方法使用聚氨酯合成的下颌骨,建立由咬肌、颞肌、翼内肌、翼外肌和二腹肌5组肌肉共同加载的下颌骨机械力学模型。采用电阻应变片法分析前牙咬合（INC）,左侧磨牙咬合（L-MOL）,双侧后牙咬合（ICP）3种咬合状态下接骨板的应变。结果3种咬合状态下接骨板的外表面均表现为受压,且上缘接骨板的应变小于下缘接骨板。另外,加载时舌侧骨折线出现裂隙。结论下颌骨在功能状态下,颏部上下缘均受到张应力。颏部正中骨折,应该按照Champy的张力带理论固定2个接骨板。     

Comparative evaluation of ten different condylar base fracture osteosynthesis techniques

The aim of this study on the mandibles of minipigs was to compare the biomechanical stability of different methods of osteosynthesis that are used in the operative treatment of fractures of the base of the condyle. Ten different systems of osteosynthesis were used to fix 164 fractures, which were tested by a two-point bending test after repositioning and fixing. This stress test was applied in four directions: lateral to medial, anterior to distal, distal to anterior, and medial to lateral. The Eckelt lag screw, one or two 2.0 mm miniplates, one miniplate with bar (KLS Martin), minicompression plates (Medicon), zygoma compression plates (Medartis), condylus fracture plates (Medartis), square 4-hole plates (KLS Martin), and either one or two resorbable 4-hole miniplates (Resorb-X, Martin) were used for osteosynthesis. A total of 164 tests were done using a universal test machine that measured forces until the osteosynthesis failed. Advantages in mechanical load capacity were also measured for the Eckelt lag screw when force was applied from medial to lateral. Fixation with one resorbable miniplate was not functionally stable. Irrespective of the direction of force applied, two miniplates were the most stable technique. There were pronounced differences depending on the direction of force applied. The results suggest that treatment with a single resorbable miniplate is not functionally stable.