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Objective@#To explore the effect of different miniscrew placement heights on the distribution of biological forces produced by clear aligner combined with intramaxillary traction for mandibular molar distalization, to identify the miniscrew location that is conducive to the protection of lower anterior tooth anchorage and to provide a reference that can be used when designing clinical treatments.@*Methods@#Mimics, GeomagicStudio 2017, SolidWorks 2016, and Ansys workbench were used to establish finite element analysis models and perform mechanical analysis under the following six working conditions: working condition 1 was the control group without miniscrews; working conditions 2 to 5 had miniscrew in the buccal bone cortex between the first and second molars of the lower jaw 10 mm, 7 mm, 4 mm, and 1 mm from the top of the alveolar crest, respectively; working condition 6 had the miniscrew in the center of the buccal tongue at the anterior edge of the ascending branch of the lower jaw 5 mm above the occlusal plane.@*Results@#On the sagittal axis, miniscrew anchorage caused distal displacement of all teeth. Compared to the control group, in the miniscrew group, the displacement of the anterior molars exceeded that of the second molars. On the vertical axis, the result in the control group was similar to backward bending; the results in the miniscrew groups resembled the effect of a lever, lowering the lateral incisors and canines and raising the central incisors and first premolars. On the coronal axis, the second premolars and the first molars showed lingual displacement in the control group, and only the premolars and first molars showed lingual displacementin the miniscrew groups. The canines were the teeth that were most strongly affected by the change in miniscrew placement height.@*Conclusion@#The higher the miniscrew position is, the stronger the protective effect on the anterior anchorage. According to the miniscrew placement height, the mandibular arch should be properly narrowed, the central incisors and first premolars should be lowered, and the lateral incisors and canines should be raised when designing clinical treatments.
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OBJECTIVE@#To compare the biomechanical stability of three cross-bridge headless compression screws and locking plates in the fixation of Mason type Ⅲ radial head fractures by finite element method.@*METHODS@#Using reverse modeling technology, the radial CT data and internal fixation data of a healthy 25-year-old male were imported into the relevant software. Three-dimensional finite element model of 3 cross-bridge headless compression screws and locking plates for MasonⅢ radial head fractures were established, and the radial head was loaded with 100 N axial loading. The maximum displacement, maximum Von Mises stress and stress distribution of the two groups were compared.@*RESULTS@#The maximum displacements of the three cross-bridge screws group and locking plate group were 0.069 mm and 0.087 mm respectively, and the Von Mises stress peaks were 18.59 MPa and 31.85 MPa respectively. The stress distribution of the three screws group was more uniform.@*CONCLUSION@#Both internal fixation methods can provide good fixation effect. CoMPared with the locking plate fixation method, the 3 cross-bridge headless compression screws fixation is more stable and the stress distribution is more uniform.
الموضوعات
Male , Humans , Adult , Finite Element Analysis , Radial Head and Neck Fractures , Bone Screws , Biomechanical Phenomena , Radius Fractures/surgery , Fracture Fixation, Internal/methods , Bone Plates , Fractures, Comminutedالملخص
Objective To design a search and rescue UAV that is portable and user-friendly in order to meet the needs of rescue personnel on the battlefield.Methods Three-dimensional design software CATIA was used to complete the structural design of the UAV body.In order to make full use of the internal space of the UAV body,folding wings were adopted to reduce the volume of the UAV.By using ABAQUS,the finite elements of the key parts of the UAV were analyzed before the modal analysis of the whole vehicle was conducted to verify the reliability of the structure.The robot simulation software Webots was used for motion simulation of the UAV.Results Simulation analysis and test verification suggested that the structural design of the UAV was well-grounded.It could be quickly and properly deployed by means of hand launch or barrels,which made it easier for rescuers to use the UAV.Conclusion The design and simulation research of UAVs with portable folding wings for search and rescue is of great significance for the research and development of physical prototypes.This study is expected to stimulate new ideas for the development of rescue equipment in the PLA,and contribute to miniaturization of UAVs.
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BACKGROUND:Lingual movable wing is a new type of lingual orthodontic technique and the different stretching lengths of the wring affect the torque control effect of anterior teeth.However,there is yet no related biomechanical research. OBJECTIVE:To investigate the displacement trend of dentition during adduction of mandibular anterior teeth and the effect of different wing stretching lengths on the biomechanical effect of mandibular anterior teeth. METHODS:The data of the mandible and lower dentition were collected by cone-beam CT and reconstructed using Mimics software to establish a three-dimensional finite element model of mandibular anterior teeth adducted by the lingual movable wing.The ANSYS software was used to analyze the initial displacement of the mandibular anterior teeth under the following conditions:A,2 mm stretching length;B,2.5 mm stretching length;C,3 mm stretching length;and D,3.5 mm stretching length. RESULTS AND CONCLUSION:The trend of initial displacement of lower dentition:The central incisors moved lingually with depression,the lateral incisors and canines moved mildly lingually with mesial lingual torsion,the second premolar was tilted distally with a marked lingual inclination and the first molar showed an overall mesial inclination with mesial crown eversion.Therefore,in the adduction cases of mandibular tooth extraction,attention should be paid to the lingual movement of the second premolar,which could be offset by corresponding techniques in clinic.The trend of anterior tooth displacement in all directions:from condition A to condition D,in the sagittal direction,the difference value in crown-root displacement of central incisors changed from-11.891 μm to-5.757 4 μm,indicating that the central incisor changes from oblique movement to overall movement.The difference value in crown-root displacement of lateral incisors changed from-11.828 1 μm to-6.711 45 μm,and that of canines changed from-7.572 3 μm to-4.695 5 μm,indicating that the oblique movement of the lateral incisors and canines is also changing to an overall movement.In the vertical direction,from condition A to condition D,the reduction of incisors was gradually increased,while that of canines was gradually decreased.These findings indicate that the stretching length of the wing can affect the oblique movement trend of the anterior teeth.As the wing continues to stretch,the torque control of the lower anterior teeth will become better.
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BACKGROUND:The proximal femoral nail antirotation is the preferred treatment for reverse osteoporotic intertrochanteric fractures.Bone cement enhancement can reduce the probability of proximal femoral nail antirotation cut-out and cut-through,but there are no relevant biomechanical studies demonstrating the effect of bone cement content and location on the stress and displacement of the fracture end. OBJECTIVE:To investigate the effects of different contents and locations of bone cement in cement-reinforced proximal femoral nail antirotation on stress,strain,and displacement of reverse osteoporotic femoral intertrochanteric fractures in the elderly by finite element analysis. METHODS:A healthy adult female right femur model was extracted by Mimics software and smoothed in Geometric software.Five types of internal fixation methods of proximal femoral nail antirotation(cementless,cephalic spherical 1 mL,cephalic spherical 2 mL,cephalic spherical 3.4 mL,and cylindrical 5 mL around spiral blade)and femoral intertrochanteric fracture(AO subtype 31-A3.1 type)model were established in Solidworks software.After assembly,the total stress distribution,peak stress and displacement of the five models of implants with the femur were compared in Ansys software. RESULTS AND CONCLUSION:(1)The peak stresses of proximal femoral nail antirotation with head-end spherical 1 mL,head-end spherical 2 mL,head-end spherical 3.4 mL,and cylindrical 5 mL enhanced proximal femoral nail antirotation around the spiral blade respectively were 571.07 MPa(located at the junction of the spiral blade and the main nail),495.45 MPa(located at the junction of the spiral blade and the main nail),467.20 MPa(located at the junction of the main nail and the distal screw connection),642.70 MPa(located at the junction of the main nail and distal screw connection),and 458.58 MPa(located at the junction of the spiral blade and the main nail).(2)The maximum displacements of proximal femoral nail antirotation with head end sphere 1 mL,head end sphere 2 mL,head end sphere 3.4 mL,and with cylindrical 5 mL enhancement around the spiral blade were 9.260 5,7.589 1,7.316 8,6.790 7,and 6.615 7 mm,respectively,all of which were located at the proximal end of the femoral head.(3)These findings revealed that for reverse femoral intertrochanteric fractures treated with proximal femoral nail antirotation,the bone cement enhancement had significant mechanical stability compared with no enhancement,and the enhancement of the spiral blade 5 mL around the perimeter was the best,which is more preferable for aged unstable intertrochanteric fractures.
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BACKGROUND:In the treatment of edentulous maxillary implants supported fixed repair,the selection of upper scaffold structure materials and the design of different distal implant implantation methods have a close influence on the long-term stability of the whole mouth implant repair. OBJECTIVE:To comprehensively explore the influence of three different materials of upper scaffold and two implant fixation designs on the biomechanics of the fixed maxillary implant repair based on the three-dimensional finite element method. METHODS:Based on the conical beam CT data of a healthy adult with normal jaws,the Mimics software was used to separate the maxillary and maxillary dentin three-dimensional solid models,and the Geomagic Studio software was used to construct the three-dimensional finite element model of denture with denture implant and fixed maxillary arch combined with specific model parameters.According to the different designs of distal implants in the maxillary posterior region,two scheme models were established.Scheme 1(Design 1)was designed in accordance with the"All-on-4"design used in clinical practice.Two implants were vertically implanted in the bilateral incisor region of the maxilla,and the other two implants were implanted in the bilateral second premolar region at a 30° angle.In scheme 2(Design 2),two implants were vertically implanted in the lateral incisor region of the maxilla,and two short implants were vertically implanted in the posterior region of the maxilla in the bilateral second premolar region.Three materials(titanium,zirconia and polyether ether ketone)were used to assign values to the upper scaffold structure in the two designs,and six different models were obtained.The biomechanical effects of the implant,surrounding bone tissue and the upper scaffold structure were compared and analyzed in the oblique loading direction. RESULTS AND CONCLUSION:(1)The maximum stress peaks of all models were distributed in the neck region around the posterior implant and the cortical bone under the two edentulous implant fixed restoration schemes,regardless of the material of the upper scaffold.(2)Compared with the alternative design of Design 2,which adopted vertical implantation of short implants,Design 1 showed a more ideal stress distribution on the maxilla.(3)The scaffold model constructed by polyether ether ketone material transferred higher stress to the implant and surrounding bone tissue close to the loading zone of the upper jaw bone,followed by titanium and zirconia.As for the support itself,the peak stress of the upper scaffold of polyether ether ketone was significantly lower than that of the zirconia and titanium scaffolds.Zirconia scaffolds were used among the three upper scaffolds to disperse the stress distribution of implant and bone tissue.(4)The results suggest that both designs can be applied to clinical practice.However,from the perspective of biomechanics,the stress distribution of the implant,surrounding bone tissue and upper scaffold in Design 1 is more rational,which is more conducive to the long-term prognosis of fixed implant repair in patients with edentulous jaws.The upper scaffold material has a certain influence on the stress distribution of the implant-bone interface.
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BACKGROUND:In implant restoration in the aesthetic area,zirconium dioxide is gradually becoming the most commonly used upper restorative material and has achieved better clinical results.Resin-ceramic composite,a new type of dental restorative material,begins to try to be used as an upper restorative material in implant restoration,but there is less research on the application of this material in implant restoration. OBJECTIVE:To compare the biomechanical differences between resin ceramic crowns and zirconia all-ceramic crown implant restorations in three occlusal relationships for restoring maxillary central incisors. METHODS:The cone-beam CT image data of a patient with single-crown implant restoration of maxillary central incisor were selected,and the maxillary bone model was extracted by using Mimics 21.0 software,and the model was imported into Solidworks 2020 software.The crown,adhesive,abutment,central screw,and implant were modeled,and the model of single-crown implant restoration of maxillary central incisor was assembled.After giving the model material property parameters(resin-ceramic composite and zirconia for the upper restoration materials)in ANSYS Workbench 2021 R1 software,three occlusal relationships(edge-to-edge occlusion,normal overjet and deep overbite)were simulated and loaded to analyze the stress distribution of the resin-ceramic crown and zirconia all-ceramic crown implant restoration models. RESULTS AND CONCLUSION:(1)The stress concentration areas in the implant restoration models of the resin-ceramic crown group and the zirconia all-ceramic crown group in different occlusal relationships were distributed in the upper restoration loading point,the abutment-implant connection,the implant neck and the surrounding bone tissue.As the occlusal relationship changed from the edge-to-edge to normal and deep overbite,the peak equivalent forces of the restorative abutment,central screw,implant,and bone tissue in both the resin-ceramic and zirconia all-ceramic crown groups gradually decreased.The highest peak equivalent forces were observed for the upper restorations in deep overbite.The zirconia all-ceramic crown group had the highest peak equivalent force in the adhesive layer in the edge-to-edge relationship,and the resin-ceramic crown group had the highest peak equivalent force in the adhesive layer in the deep overbite.(2)In the edge-to-edge occlusion,the peak equivalent force of the adhesive layer and central screw in the resin-ceramic crown group was slightly smaller than that in the zirconia all-ceramic crown group,and there was no significant difference between the two groups in the peak equivalent force at the upper restoration,restoration abutment,implant,and bone tissue.The peak stresses in the upper restoration,adhesive layer,and central screw of the resin-ceramic crown group were slightly less than those of the zirconia all-ceramic crown group at normal fit,and there were no significant differences between the two groups in the peak equivalent forces at the restoration abutment,implant,and bone tissue.In deep overbite,the peak adhesive,abutment,and central screw stresses were greater in the resin-ceramic crown group than in the zirconia all-ceramic crown group,with no significant differences in the upper restorations,implants,or bone tissue.(3)The results showed that the upper restorative material had no significant effect on the stress distribution of the implant and bone tissue,and had some effects on the stress distribution of the upper restoration,adhesive,restoration abutment,and central screw,but the difference was not significant.The occlusal relationship has a significant influence on the stress distribution in all structures and bone tissue of the implant restoration.The resin-ceramic crowns have a buffering effect on the stresses in the case of edge-to-edge and normal occlusion.
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BACKGROUND:For dislocation of acromioclavicular joint induced by coracoclavicular ligament fracture,single EndoButton Plate reconstruction and double EndoButton Plates reconstruction are common repair methods.Further study on the stress distribution and fracture risk of the two repair methods is of great significance. OBJECTIVE:To study the biomechanical properties of the coracoclavicular ligament,and compare the fixation effect,stress distribution and failure mode of single and double EndoButton Plates reconstruction. METHODS:(1)Finite element simulation analysis:Mimics,Wrap and SolidWorks were used to establish normal coracoclavicular ligament,single EndoButton Plate reconstruction and double EndoButton Plates reconstruction.Ansys software was used to analyze the stress and deformation of the scapula and clavicle of each model under vertical load.(2)Sample experiment:Fifteen intact scapular-clavicle specimens were randomly grouped into five groups,with three specimens in each group.In group A,the acromioclavicular ligament was severed and the coracoclavicular ligament remained intact.In group B,acromioclavicular ligaments and trapeoid ligaments were severed,leaving intact conical ligaments.In group C,acromioclavicular ligaments and conical ligaments were cut off,and the intact traprex ligaments were retained.In group D,acromioclavicular and coracoclavicular ligaments were severed,and coracoclavicular ligaments were repaired by single EndoButton Plate reconstruction.In group E,acromioclavicular and coracoclavicular ligaments were severed,and the coracoclavicular ligaments were repaired by double EndoButton Plates reconstruction.The mechanical experiment was carried out by a mechanical testing machine to analyze the biomechanical status,stress distribution and failure patterns of the scapular-clavicle and clavicle. RESULTS AND CONCLUSION:(1)Finite element simulation analysis:The average stress of coracoclavicular ligament attached specimens was the lowest,and the risk of coracoclavicular fracture was less than that of single and double EndoButton Plates reconstruction.The mean stress of the coracoid process was similar in single and double EndoButton Plates reconstruction,and the fracture risk was similar.(2)Sample experiment:In groups A,B,C,D and E,the stiffness of specimens was(26.4±3.5),(19.8±2.8),(21.3±3.2),(57.7±4.1),and(46.2±2.8)N/mm,respectively;the ultimate loads were(545.5±53.7),(360.1±42.1),(250.9±44.4),(643.5±39.1),and(511.9±31.7)N,respectively;global stiffness in groups D and E was higher than that in group A(P=0.000 06,0.000 3);ultimate load in group D was higher than that in group A(P<0.05);the ultimate load was not significantly different between the group E and group A(P>0.05).Ligament fracture was observed in groups A,B and C and coracoid process fracture was found in groups D and E.(3)These results suggest that from the biomechanical analysis,Single EndoButton Plate reconstruction and double EndoButton Plates reconstruction are effective treatment techniques for coracoclavicular ligament fracture in acromioclavicular joint dislocation,but increase the risk of fracture.The double EndoButton Plates reconstruction dispersed the stress of the steel plate and reduced the contact force between the steel plate and bone,but slightly reduced the ultimate bearing capacity.Single and double EndoButton Plates reconstruction should be selected according to the actual clinical situation.
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BACKGROUND:Due to the treatment of cervical spondylosis,the Zero-P system of the anterior cervical interbody fusion system will have problems such as screw loosening and fracture after operation,so a novel Low-P system has been developed. OBJECTIVE:To compare the effects of the novel Low-P and Zero-P anterior cervical intervertebral fusion systems on the biomechanical properties of adjacent segments of the cervical spine and to perform stress analysis on the internal fixation system,so as to provide a theoretical reference for clinical treatment. METHODS:A complete model of the C1-C7 segment of the cervical spine was established.Based on the effectiveness of the model,a finite element model of Low-P(type Z Low-P and type H Low-P)and Zero-P system implanted in C4-C5 segments was established.The stress distribution of implanted devices and adjacent vertebral nucleus pulposus,fibrous rings and end plates was analyzed under the conditions of forward flexion,posterior extension,lateral bending and rotation. RESULTS AND CONCLUSION:(1)After implantation of Low-P and Zero-P internal fixation devices,the range of motion of the type H Low-P system was large;the maximum stress value of type Z Low-P system was small;the maximum stress of Zero-P on the nucleus pulposus of adjacent segments was large;the maximum stress of end plate was small.(2)The influence of three internal fixation systems on adjacent segment fiber rings was close.(3)The screw stress of the Zero-P internal fixation system was much greater than that of the Low-P system.(4)It is indicated that compared with Zero-P type internal fixation system,the novel Low-P system reduces the stress value of steel plate and screw,which can reduce screw loosening and internal fixation system failure.The Low-P system has less stress on the nucleus pulposus of adjacent discs and reduces disc degeneration in adjacent segments.This paper provides a theoretical basis for the clinical study of a Low-P type internal fixation system.
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BACKGROUND:Among the pathogenic factors of cervical spondylosis,herniation of the intervertebral disc,dislocation of the facet joint and the stenosis of the intervertebral foramen are important factors leading to symptoms in patients.Moreover,inappropriate manipulation may aggravate the possibility of cervical disc rupture,leading to exacerbation of symptoms in patients. OBJECTIVE:To compare the effect between sagittal cervical manipulation and traditional cervical rotation manipulation on the area of the intervertebral disc,facet joint and intervertebral foramen at the operative segment by the finite element analysis. METHODS:The neck CT data of a male volunteer with a normal neck were selected and imported into Mimics 17.0 three-dimensional reconstruction software.Geo-magic Studio 12.0,Solidworks 2017 and Ansys Workbench 17.0 software were used for the construction of the finite element model of cervical vertebrae(C3-6)including intervertebral disc and articular cartilage.The lower end plate of the C5 vertebral body was fixed.A uniformly distributed vertical downward 50 N load was applied on the upper surface of the upper vertebral body(C3).The stress,deformation and deformation direction of the C4-5 intervertebral disc,joint capsule stress,the displacement of facet joints and the area of bilateral intervertebral foramen were compared between sagittal cervical manipulation and traditional rotation reduction. RESULTS AND CONCLUSION:(1)When using the rotation technique,the maximum normal equivalent stress(von Mises stress)of the C4-5 disc was 8.06 MPa;the total deformation was 1.05 mm,and the fiber ring expanded to the left and outside.When using the sagittal tip lifting technique,the maximum normal equivalent stress(von Mises stress)of the C4-5 disc was 2.60 MPa;the total deformation was 0.90 mm,and the fiber ring expanded to the left and back.Compared with the rotation technique,the pressure of the cervical manipulation technique on the disc was less(about 32.3%of the rotation technique),and the deformation degree of the disc was also light(about 85.7%of the rotation technique).(2)When the rotation technique was used,the maximum stresses of the left and right articular capsule ligaments were 0.37 MPa and 1.69 MPa,respectively.The overall displacement of the facet joint was 2.21 mm.The area of the right intervertebral foramen decreased by about 3.8%and the area of the left intervertebral foramen increased by about 0.9%.When the sagittal end lifting manipulation was performed,the maximum stresses of the left and right articular capsule ligaments were 0.27 MPa and 1.70 MPa,respectively;the overall displacement of the facet joint was 1.63 mm;the area of the right intervertebral foramen increased by about 2.6%,and the area of the left intervertebral foramen decreased by about 0.9%.Compared with rotation manipulation,sagittal end lifting manipulation had fewer changes in the displacement of facet joint,joint capsule stress and intervertebral foramen area,so it was safer to operate.(3)In conclusion,compared with cervical rotation manipulation,sagittal end lifting manipulation has fewer changes in facet joint displacement,intervertebral disc stress/deformation degree,joint capsule stress,and foraminal area.In clinical practice,more appropriate manipulation should be selected based on biomechanical results after an accurate assessment of patients'conditions.
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BACKGROUND:Endoscopic treatment of lumbar disc herniation has obvious advantages over traditional open surgery.Endoscopic surgery involves the implantation of a working cannula,which requires only partial bone removal,and there are no studies on the effects of two types of intraoperative foraminoplasty and laminoplasty on the mechanical properties of the local structure of the lumbar spine. OBJECTIVE:To compare the effect of foraminoplasty and laminoplasty on the biomechanical properties of disc and isthmus of the responsible segment. METHODS:The lumbosacral CT images of a healthy male volunteer were taken,and a finite element model M0 of the L3 to sacral vertebrae was established,on which the primary and secondary foraminoplasty models M1 and M2 of the L5/S1 and the laminoplasty model M3 were built.The same load was applied to compare the intervertebral motion range,disc Von Mises stress and equivalent stress characteristics of L5 vertebral isthmus with each model. RESULTS AND CONCLUSION:(1)Compared with M0,M1 and M2 motion range in L5/S1 segment did not change significantly in all directions;M2 overall motion range increased by 8.60%in flexion;M3 increased by 8.23%and 8.26%in L5/S1 right bending and right torsion,and 5.39%and 5.67%in overall motion range in flexion and right bending,with no significant changes in motion range in the rest of working conditions.(2)Compared with M0,M1 showed no significant change in the extremes of Von Mises stress at L5/S1 disc;M2 increased 11.06%,12.50%,18.32%,and 15.48%in flexion,extension,left torsion,and right torsion;M3 increased 12.22%,19.54%,10.05%,and 9.97%in flexion,extension,left torsion,and right torsion,and the rest working conditions and L4/5 disc maximum Von Mises stress did not change significantly.(3)Compared to M0,the maximum Von Mises stress in the left isthmus of L5 of M1 increased by 12.43%in left bending,18.38%,13.29%,13.62%,and 40.00%in the right isthmus in extension,right bending,left torsion,and right torsion.The maximum Von Mises stress in the left isthmus of L5 of M2 increased by 38.87%,42.63%,16.95%,and 19.35%,and that in the right isthmus increased by 12.58%,33.70%,12.92%,and 17.42%in flexion,extension,left bending,and left torsion.The maximum Von Mises stress in the left isthmus of L5 of M3 increased 67.07%,78.14%,32.33%,62.94%,and 89.99%in flexion,extension,left and right bending,and right torsion.(4)The results suggest that foraminoplasty and laminoplasty have a small effect on spinal motion range;there is a mild increase in the extreme values of disc Von Mises stress in the segments operated by interbody laminoplasty and secondary foraminoplasty;there is no significant change in the extreme values of disc Von Mises stress in adjacent segments,and there is a significant increase in the Von Mises stress in the ipsilateral isthmus operated by the interbody laminoplasty model.
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BACKGROUND:Ankylosing spondylitis is a chronic inflammatory disease with chronic rheumatic immunity.Soft tissue ossification and fusion and spinal stiffness can cause biomechanical changes. OBJECTIVE:To reconstruct the lumbar-sacral intervertebral disc in ankylosing spondylitis patients with lumbar kyphosis by finite element analysis,and to study the range of motion of each segment of T11-S1 and the biomechanical characteristics of annulus fibrosus and nucleus pulposus. METHODS:The imaging data were obtained from an ankylosing spondylitis patient with lumbar kyphosis.The original CT image data of continuously scanned spine were imported into Mimics 21.0 in DICOM format,and T11-S1 was reconstructed respectively.The established model was imported into 3-Matic software in the format of"Stl"to reconstruct the intervertebral disc,and the fibrous intervertebral disc model was obtained.The improved model was further imported into Hypermesh software,and the vertebra,nucleus pulposus,annulus fibrosus and ligament were mesh-divided.After the material properties were given,the model was imported into ABAQUS software to observe the range of motion of each vertebral body in seven different working conditions of T11-S1,and analyze the biomechanical characteristics of each segment of annulus fibrosus and nucleus pulposus. RESULTS AND CONCLUSION:(1)The range of motion of L1 vertebrae was higher than that of other vertebrae under six different working conditions:extension,forward flexion,rotation(left and right),and lateral flexion(left and right).The maximum range of motion was 2.18° during L1 vertebral flexion,and the minimum range of motion was 0.12° during L5 vertebral extension.(2)The annular fiber flexion at L2-L3 segments was greater than the extension(P<0.05),and the annular fiber flexion at L3-L4 and L4-L5 segments was less than the extension(P<0.05).The left rotation of L1-L2 annular fibers was greater than the right rotation(P<0.05).The left flexion of the annulus was greater than the right flexion in L1-L2,L2-L3,L3-L4,L4-L5 and L5-S1 segments(P<0.05).(3)The nucleus pulposus stresses of T11-L12,L1-L2,L2-L3,L3-L4 and L4-L5 segments in forward flexion were greater than in extension(P<0.05).The left rotation of T12-L1 and L3-L4 segments was smaller than the right rotation(P<0.05),and that of T11-T12,L1-L2,and L2-L3 segments was larger than the right rotation(P<0.05).The left flexion was larger than the right flexion in the T11-S1 segment.(4)It is concluded that in ankylosing spondylitis patients with lumbar kyphosis,the minimum range of motion of the vertebral body is located at the L5 vertebral body in extension.To prevent fractures,it is recommended to avoid exercise in the extension position.During the onset of lumbar kyphosis in patients with ankylosing spondylitis,the maximum stress of the annulus fibrosus and nucleus pulposus is located in the L1-L2 segment,which is fixed and will not alter with the change of body position.The late surgical treatment and correction of deformity should focus on releasing the pressure of the annulus fibrosus and nucleus pulposus in this segment to avoid the rupture of the annulus fibrosus and the injury of the nucleus pulposus.
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BACKGROUND:The incidence of high lumbar disc herniation in elderly patients with osteoporosis is increasing.The changes in lumbar overall mechanical strength and biomechanical properties of adjacent vertebrae after conventional posterior approach decompression and interbody fusion have not been clarified.Finite element analysis has great value in the field of biomechanics because of its advantages of non-invasiveness,high repeatability and accuracy. OBJECTIVE:To explore the establishment of a finite element model of senile osteoporotic L3/4 lamina decompression using finite element analysis and intervertebral fusion spine,and to evaluate the biomechanical status of the internal fixation complex of bones under bending motion in elderly patients with osteoporosis. METHODS:Mimics 21.0 was used to extract the DICOM data of the spine CT to establish the 3D bony structure of the lumbar spine(T12-L5),which was imported into Geomagic wrap 2017.The L3/4 full lamina decompression model was established after redrawing the mesh,deleting the nails,cutting the model,filling the cavity,detecting and editing the contour line,constructing curved surfaces and grids,fitting curved surfaces and other operations.Solidworks 2017 was used to construct pedicle screws,connecting rods,and intervertebral fusion cages,which were assembled into the L3/4 full lamina decompression model.Intervertebral discs and articular process cartilage and other structures were established through operations such as stretching,isometric surfaces,moving and copying entities.ANSYS Workbench 17.0 was utilized for material assignment,simulating spinal ligaments,meshing,applying force and limiting boundary conditions.A complete osteoporotic L3/4 laminar decompression and intervertebral fusion spine finite element model was established.The stress,strain and displacement cloud diagram of the L3/4 lamina decompression and intervertebral fusion full lumbar spine finite element model were observed under simulated bending conditions. RESULTS AND CONCLUSION:(1)In terms of the stress cloud diagram:The T12-L1 vertebra had the highest average stress value;L2 dropped by 24%;L3 dropped by 55%,and L4-5 dropped by about 80%.The stress concentration in the L4/5 articular process area was the highest,followed by L2/3,and lighter in L1/2 and T12/L1.The stress concentration at the junction of the screw and the connecting rod was obvious,followed by the screw at the entrance and exit of the pedicle.(2)In terms of strain and displacement cloud map:The strain degree of L4/5 and L2/3 articular process was the highest;the strain degree of T12/L1 and L1/2 was the second,and the L3/4 segmental fusion cage,pedicle screw and connecting rod had no any visible deformation.The intervertebral discs of all segments showed great deformation.(3)It is concluded that the cooperative operation of multiple software can successfully construct a finite element model of the spine with L3/4 lamina decompression and intervertebral fusion in elderly patients with osteoporosis.Elderly patients after lumbar spine surgery can tolerate forward flexion,confirming that L3/4 laminar decompression and intervertebral fusion can maintain the shape of the spine and ensure the stability of the spine,but it is necessary to be alert to the occurrence of thoracolumbar stress fractures and adjacent spondylopathy.
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BACKGROUND:After the internal fixation of cannulated screws in femoral neck fractures,because the affected limb is often unable to bear weight in the short term and the implants with high stiffness have a stress shielding effect on the fracture end,it is easy to cause osteoporosis of the affected limb and changes in the biomechanical distribution of the proximal femur,the incidence of osteonecrosis of the femoral head is high after surgery.At present,few studies have been conducted on the biomechanical effects of osteoporosis at the proximal end of the femur occurring after femoral neck fracture surgery on femoral neck fracture treated with cannulated screws. OBJECTIVE:Using finite element analysis,to investigate the biomechanical effects of osteoporosis occurring after femoral neck fracture surgery on femoral neck fracture treated with cannulated screws and explore the role of biomechanical factors in osteonecrosis of the femoral head. METHODS:Based on the obtained CT scan data of the femur in a patient with a femoral neck fracture,a proximal femoral model for internal fixation for femoral neck fracture was established by Mimics 19.0,3-Matic,UG 11.0,Hypermesh 14.0,and Abaqus software.One finite element model of the proximal femur without osteoporosis and three finite element models of the proximal femur with osteoporosis were analyzed using Abaqus software.The stress,contact pressure,displacement peak and cloud map under different components of the four models were measured and analyzed,and the internal stress changes and distribution of the femoral head were compared and analyzed. RESULTS AND CONCLUSION:The stresses and contact pressures of the femoral head and lower anterior cannulated screws varied more with the degree of osteoporosis.The peak displacement of the four models increased slowly with the degree of osteoporosis.By one-way analysis of variance,there was no significant effect of the degree of osteoporosis on the peak stress,contact pressure,and displacement of the different components.The internal stress distribution of the femoral head changed with the degree of osteoporosis.Changes in the biomechanical environment of the proximal femur have an important impact on osteonecrosis of the femoral head.
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BACKGROUND:Intramedullary nail has achieved a good clinical result in the treatment of femoral shaft fractures,but some patients still have aseptic nonunion due to mechanical instability.The femur is the longest and largest bone in the human body,but there are few studies on whether the fracture of the femur has different biomechanical results in different areas and the influence of different inserting methods on the stability of fracture fragments in different areas. OBJECTIVE:To analyze the biomechanical characteristics of anterograde and retrograde intramedullary nails in the treatment of different areas of femoral shaft fractures,and to evaluate the best way of insertion to reduce the incidence of nonunion. METHODS:CT data of a healthy volunteer were selected to import into the software of Mimics 19.0 and Geomagic studio 2017 to extract and optimize the three-dimensional model of the right femur.The anterograde and retrograde intramedullary nail models were built with Solidworks 2017 software and assembled with femoral shaft fracture models at different fracture areas according to standard surgical techniques.The models were imported into Abaqus 2017 software in STEP format to set material attribute parameters,boundary conditions,load and submit calculation,and the results were viewed in the visualization module.Among them,the antegrade and retrograde intramedullary nails of the upper femoral shaft fracture were A1 and A2 models,B1 and B2 models in the middle segment,and C1 and C2 models in the lower segment. RESULTS AND CONCLUSION:(1)In models A1,B1 and C2,the overall stress distribution of the femur was more uniform,and the placement,the displacement and angle of the fracture site,and inversion angle of the proximal femoral bone fragment were smaller.(2)For the upper and middle femoral shaft fractures,the anterograde intramedullary nail has a better biomechanical effect.For lower femoral shaft fractures,a retrograde intramedullary nail is preferable.
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BACKGROUND:The more vertical the femoral neck fracture line,the more shear force the femoral neck fracture may bear,so it may be prone to internal fixation failure,nonunion,or necrosis of the femoral head.At present,there is controversy as to which hollow nail fixation mode is ideal. OBJECTIVE:To evaluate different configurations and numbers of cannulated screw configurations to learn more about the biomechanical differences in vertical fractures of the femoral neck using finite element analysis. METHODS:Femoral CT data were collected from a 24-year-old healthy male volunteer and imported into Mimics software to build a three-dimensional geometric model of the femur.Model refinement and surface fitting processing were carried out in Geomagic software and imported into SolidWorks software to establish a vertical fracture model of the femoral neck.Six cannulated screw models were established,including three triangle configuration,three inverted triangle configuration,three double-plane double-support configuration(F scheme),three transverse configuration,four diamond configuration and four Alpha configuration.The peak stress,strain and displacement of internal fixation and femoral fracture models under different loads(350,700,1 400,and 2 100 N)were compared among different configurations. RESULTS AND CONCLUSION:(1)Under four kinds of loads,screw stress conditions were as follows:biplanar double-supported configuration(F scheme)>transverse configuration>inverted triangle configuration>positive triangular configuration>Alpha configuration>rhombus configuration.The peak value of Von mises stress was concentrated in the screw close to the fracture line.(2)Under four kinds of loads,the screw displacement was Alpha configuration>inverted triangle configuration>positive triangular configuration>biplanar double-supported configuration(F scheme)>rhombus configuration>transverse configuration,and the peak displacement was mainly concentrated on the hollow screw head.(3)Under four kinds of loads,the stress conditions of the proximal femoral bone block were biplanar double-supported configuration(F scheme)>transverse configuration>inverted triangle configuration>Alpha configuration>positive triangular configuration>rhombus configuration,and the stress peak mainly concentrated in the lower neck of femur.(4)Under 350 N load,the displacement of the proximal femur bone block was transverse configuration>biplanar double-supported configuration(F scheme)>positive triangular configuration>Alpha configuration>inverted triangle configuration>rhombus configuration.In the other three loads,the peak displacement of the inverted triangle configuration was smaller than that of the rhombus configuration.The peak displacement was mainly concentrated in the head.(5)The rhombus configuration was the most dispersed in the stress distribution of the proximal femoral bone.The rhombus configuration was the smallest in the peak displacement of the femur.The stress,displacement and peak displacement of the fracture end of each internal fixed model increased gradually with the increase of load.(6)The biomechanical performance of the four diamond-shaped models in the internal fixation of vertical femoral neck fractures is better than that of other groups of models.The four rhomboid models have stable fixation,small displacement value of fracture end and dispersed stress,which can help resist shear force and prevent varus collapse and create a good mechanical environment for fracture healing.
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BACKGROUND:The treatment of distal tibial fractures with soft tissue injury has always been challenging,and the new retrograde tibial nailing is a new choice.Up to now,there were few reports on the biomechanical properties between the new retrograde tibial nailing,anterograde intramedullary nailing and supercutaneous locking plate. OBJECTIVE:To explore the biomechanical stability of new retrograde tibial nailing,antegrade intramedullary nailing and supercutaneous locking plate in the treatment of distal tibial fractures with soft tissue injury using finite element analysis so as to offer a scientific foundation for clinical application. METHODS:The finite element model of transverse distal tibia fracture was established by relevant software utilizing the CT data of the tibia from a 42-year-old healthy male.Retrograde tibial nailing,antegrade intramedullary nailing and supercutaneous locking plate finite element models were assembled under the principle of fracture fixation.Finally,meshing,applying loads,and data processing were accomplished with the ANSYS 2019 software.Moreover,the stress distribution and displacement of the tibia and internal fixation of each model were compared. RESULTS AND CONCLUSION:(1)The displacement of fracture end in the three groups increased with the increase of load.In all mode loads,the average displacement of the fracture end was the least in the retrograde tibial nailing group,followed by the supercutaneous locking plate group,and the highest in the antegrade intramedullary nailing group.At 800 N vertical load,the displacement difference of the fracture end was statistically significant(P<0.05).There was no statistical significance in other load modes.(2)Under different loads,the tibial stress in the three groups was the highest in the middle of the tibia,and gradually decreased to the proximal and distal ends.The stress distribution of the tibial shaft was the highest in the retrograde tibial nailing group,followed by the supercutaneous locking plate group,and the least in the antegrade intramedullary nailing group.(3)Under different loads,the stress of the tibial stress raiser in the three groups was significantly higher in the supercutaneous locking plate group than in the other two groups,with statistical significance(P<0.05).(4)Under different loads,the stress of the fixators in the three groups was the largest in the supercutaneous locking plate group,followed by the retrograde tibial nailing group,and the minimum in the antegrade intramedullary nailing group.There were significant differences in the stress of fixator stress raiser among the three groups under different loading modes(P<0.05).(5)It is indicated that all three fixation methods have the good anti-rotation ability and axial stability.Retrograde tibial nail shows better biomechanical stability.
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BACKGROUND:At present,wrist protection products designed in and outside China have not solved the contradiction between protecting the wrist joint from injury and maintaining the flexible movement of the wrist joint. OBJECTIVE:To investigate the biomechanical mechanism of dorsiflexion injury of the wrist joint in elderly people after falls,and to provide a biomechanical basis for the prevention and treatment of wrist injury in elderly people after falls. METHODS:A 65-year-old man was selected to obtain the original data by uninterrupted CT scan of the middle and lower 2/3 of his left forearm up to the end of the finger.A finite element model of wrist dorsiflexion was established using ANSYS 12.0 finite element software.The palm surface of the model was constrained,and the model at a velocity load of 2 m/s in the direction of vertical downward was given to simulate the injury state of the palm when the elderly fall.The stress distribution of the soft tissues and bones of the wrist joint and the change of the stress with time were observed after the load was applied. RESULTS AND CONCLUSION:(1)A realistic and effective finite element model of the dorsal extension position of the wrist joint of the elderly was established.The soft tissue stresses were mainly concentrated in the small fissure of the palm and the dorsal side of the wrist after loading.The skeletal stresses were mainly concentrated in the lower end of the ulnar radius dorsally.The stresses in the lower end of the radius were the greatest.The palmar stresses were mainly concentrated in the middle and lower 1/3 of the radius and the hook bone.The stress distribution of the ulnar radius was asymmetric,and the stresses in the radius were more concentrated.(2)The results of the study are consistent with the clinical situation of a fallen wrist injury in elderly people,and can be used to explain the mechanism of wrist dorsiflexion injury,which can provide the biomechanical basis for the design of wrist protection devices that can be used to prevent wrist injury induced by falling and the treatment of wrist injury in elderly people.
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BACKGROUND:Three-point mechanics is an effective method for ankle foot orthosis correction and prevention of various foot diseases.At present,the clinical application research on 3D printing ankle foot orthosis has been widespread;however,there are relatively few reports on numerical simulation and finite element analysis involving three-point mechanical correction.There is a lack of relevant biomechanical experimental verification. OBJECTIVE:Three-point force was loaded to analyze the composite model of ankle foot orthosis and foot by finite element method,observing the effect of foot correction with ankle foot orthosis under three-point force intervention,verifying the effectiveness of three-point force and the reliability of ankle foot orthosis. METHODS:A three-dimensional foot and ankle model of a healthy volunteer was constructed based on the medical image processing software Mimics.Rodin 4D and Geomagic reverse engineering software were used to optimize the models and design personalized ankle foot orthosis models.Solidworks software was utilized to turn the ankle model inside for 10° to simulate the foot varus disease.Static loading was carried out on the foot force application area by ANSYS software combined with the three-point mechanics principle.The deformation and stress changes of the foot and ankle tissues were analyzed when the human foot pain threshold was met.The display dynamics was used to further verify the effectiveness of the three-point force applied by the ankle foot orthosis. RESULTS AND CONCLUSION:(1)The personalized ankle foot orthosis designed in this paper had the effect of preventing and fixing foot and ankle varus.The ankle varus was 1.81 mm after being loaded with 1 N·m of varus when not wearing ankle foot orthosis,while it was only 0.44 mm after wearing ankle foot orthosis,the deformation rate was reduced by 75.7%,and the effect of preventing varus was significantly enhanced.(2)When only coronal correction was performed,the low calcaneal force would aggravate the varus angle of the front foot.After adjusting the correction force on the inside of the heel and above the medial malleolus,the varus angle of the front foot and the calcaneus position were improved;however,the medial phalangeal region of the foot still had different degrees of adduction and displacement,which would aggravate the adduction deformity of the patient's front foot.(3)The correction effect of the coronal plane and horizontal plane was better than that of the single coronal plane.There was no adduction and displacement of the medial phalanges of the front foot and the varus angle of the front foot decreased under the force(25,10,10,20 N)of the medial heel,the medial shaft of the first metatarsal,below the lateral malleolus and above the medial malleolus,and the valgus along the X-axis was corrected by 1.395 mm,the calcaneus valgus was corrected by 1.227 mm.The calcaneus varus angle was corrected from 10.21° to 7.25°,and the varus angle was improved by 28.9%.(4)The lateral plantar metatarsal load decreased,the medial plantar metatarsal load increased under the action of a two-plane three-point force,and the plantar bone stress was significantly improved after correction.Thus,the reliability of the three-point force principle was further verified.This study provides an important theoretical support for the implementation of ankle foot orthosis in the treatment of varus in clinical practice.
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BACKGROUND:Less is reported on the influence of cortical bone thickness on displacement and equivalent stress. OBJECTIVE:To analyze the influence of cortical bone thickness on the maximum displacement and equivalent stress at the implant-bone interface through a three-dimensional finite element method,thereby providing some suggestions for oral implantation. METHODS:In this experiment,we selected the cone-shaped CT image data of a patient who was scheduled for mandibular first molar implant restoration.First,we established a mandibular model in Mimics13 software,and then imported it into Solid works 2022 software.According to the related product information,we drew the cone-shaped implant(4.1 mm×10 mm)and the upper prosthesis model.Cortical bone models were obtained according to different cortical bone thicknesses(2.5,2.0,1.5,1.0 mm)and named D1,D2,D3,and D4,respectively.All the models were imported into ANSYS Workbench 2021 software and cross-combined.Finally,we applied vertical and oblique loads to the four groups of models,and analyzed the stress of the models in each group. RESULTS AND CONCLUSION:The peak equivalent stress is lowest in the cancellous bone and highest in the upper prosthesis,that is,at the abutment-implant junction.The peak stress increases with the decrease of cortical bone thickness.The peak stress of the abutment increases with the decrease of cortical bone thickness,and a similar explanation can also be applied to the other implant restoration components.The peak stress in bone tissue and implants increases with the increase of cortical bone thickness.In models D1,D2,D3,the peak stress in implants is higher than that in bone tissue,but the results are reversed in D4.