经皮骨移植增强的有限元研究

目的利用腰椎三维有限元模型,探讨松质骨粒(cancellous bone granule,CBG)和聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)增强后对治疗节段和相邻非治疗节段椎体生物力学影响。方法 L1～L2的三维功能脊柱单位的有限元模型由脊柱尸体标本CT扫描后形成。分别模拟骨质疏松模型、CBG和PMMA增强,分析轴向压缩、前屈和后伸3种加载状态下手术前后治疗节段和相邻非治疗节段椎体应力和应变的变化。结果在压缩、前屈和后伸3种加载状态下,松质骨粒增强模型强化区最大的Von Mises应力/应变分别为0.457、0.469、0.499 MPa/0.459%、0.471%、0.501%;PMMA增强模型为0.864、0.824、0.966 MPa/0.029%、0.028%、0.033%;骨质疏松模型相应区域为0.237、0.253、0.258 MPa/0.698%、0.752%、0.759%。与骨质疏松模型比较,治疗节段增强区域的应力/应变明显改变。结论 CBG和PMMA均增强治疗节段的总体强度和刚度水平,有利于椎体功能的重建,但就材料力学相容性和生物相容性而言,CBG的增强优于PMMA增强。     

椎体成形术治疗老年骨质疏松椎体压缩骨折对邻近节段生物力学的影响

目的:应用三维有限元模型探讨椎体成形术治疗老年骨质疏松椎体压缩性骨折对邻近节段生物力学的影响.方法:选取1例老年骨质疏松椎体(T12)压缩性骨折女性患者的术前、球囊扩张后凸成形术(KP)术后CT片,范围为T11～L1(包括病椎、邻近椎体和邻近椎间盘),分别建立术前、术后的三维脊柱功能单元的有限元模型.对T11上终板垂直向下加载300N的力矩和10N·m的旋转力矩,分析在垂直载倚、前屈、后伸、侧屈及旋转的情况下,手术前后病变椎体的变化以及椎体皮质骨、松质骨、相邻椎间蕊、终板的应力改变情况.结果:成功建立术前、术后脊柱功能单元的三维有限元模型,术前T12椎体前、中缘高度分别为13.1mm和10.9mm,术后分别为15.2mm和12.6mm,明显增高(P<0.05).在垂直载荷应力下,邻近椎体上下终板(T11下终板和L1上终板)所受应力无显著变化,但在前屈、后伸、侧屈、轴向旋转时T11/12椎间盘所受压力分别增加0.66、0.88、2.25、0.85MPa;T12/L1椎间盘所受压力分别增加1.56、1.60、0.50、2.35MPa,与术前比较均有显著性差异(P<0.05).结论:球囊扩张后凸成形术有效改善了脊柱功能单位的生物力学性能,并未对邻近椎体产生较大的影响,但可能会加速邻近椎间盘的退变.     

骨水泥不同弥散方式对椎体成形术后生物力学影响的有限元分析

目的:探讨术中骨水泥不同弥散方式在治疗骨质疏松性椎体压缩骨折中的生物力学影响。方法:选取老年骨质疏松性压缩骨折志愿者1例,男性,68岁,身高172 cm,体重60 kg。既往身体健康,行X线片及胸腰部CT检查,诊断为L_1椎体压缩性骨折。从T_(10)-L_5之间使用CT扫描,采用Mimics软件提取CT数据,使用Geomagic wrap及Solidworks建模,建立术前胸腰段骨质疏松性椎体压缩骨折三维有限元模型(T_(12)-L_2),同样地模拟出椎体成形术中骨水泥弥散的形态,根据不同的弥散方式(分为骨水泥与上下终板均不接触、骨水泥仅与上终板接触及骨水泥与上下终板同时接触3种情况),对模型施加直立、直立+前屈、直立+后伸、直立+左侧弯、直立+右旋转5种载荷,同时与术前的无骨水泥腰椎模型进行对比,记录并比较各个模型载荷下的变形和应力分布。结果:建立了胸腰段骨质疏松性椎体压缩骨折的三维有限元模型后发现,在骨水泥与上下终板均不接触、骨水泥仅与上终板接触、骨水泥与上下终板同时接触3种不同的模型下,其变形情况差异不大。在L_1松质骨中,无骨水泥腰椎组的Von Mises应力明显高于骨水泥组。在3组不同的骨水泥注入方式中,骨水泥和上下终板均接触组的Von Mises应力水平最低,仅和上终板接触组其次,未与上下终板接触组最高。在骨水泥应力比较中,骨水泥和上下终板均接触组的Von Mises应力分别为直立12.375 MPa、直立+前屈16.411 MPa、直立+后伸16.801 MPa、直立+左侧弯13.425 MPa、直立+右旋转13.014 MPa,显著高于另外两组,其次为仅与上终板接触组,不与上下终板接触的Von Mises应力最低。结论:骨水泥和上下终板均接触,可有效吸收并传递载荷带来的应力水平,降低松质骨的应力水平,减少手术椎体再骨折的可能。     

脊柱胸腰段应力分布与骨折相关性的三维有限元分析

【摘要】 目的：观察脊柱胸腰段骨折与椎体骨性结构及韧带间应力分布的相关性,探索脊柱胸腰段椎体骨折的力学机制。方法：招募8名健康男性青年志愿者,行脊柱全长X线片和CT检查排除脊柱畸形、肿瘤及骨病,对脊柱各椎体及股骨行骨密度测定排除骨质疏松。均行自T11椎体上终板至L2椎体下缘CT薄层扫描,将8名志愿者CT图像参数导入ABAQUS 2016软件中进行标准化,并进行有限元网格化构建。应用MIMICS 17.0、GEOMAGICS 15.0和PRO/ENGINEER 5.0软件处理,建立脊柱胸腰段有限元模型,测量模型相关参数,并验证模型有效性。在T11椎体上终板上加载竖直轴向载荷500N、附加扭矩10N·m模拟垂直压缩、前屈、后伸、左右侧屈、左右旋转7种运动状态,使用ABAQUS软件对有限元模型7种运动状态下的应力分布特点及变化规律进行分析,观察应力分布与脊柱胸腰段骨折的相关性。结果：建立的三维有限元模型共有309583个节点和428760个单元,包括4个椎体、3个椎间盘、前纵韧带、后纵韧带、横突间韧带、棘间韧带等结构。7种运动状态下的数据与文献报道的数据无明显偏差,模型有效。T11~L2椎体椎弓根截面积分别为135mm2、154mm2、105mm2、139.2mm2。应力云图结果显示各运动状态下高应力区存在于椎体的松质骨、椎弓根及其周围骨皮质。在垂直压缩状况下,T12椎体所受应力最大（617.4MPa）,前屈状态下T11所受应力最大（200.7MPa）,后伸、左右侧屈和左右旋转状态下L1椎体所受应力最大（314.2MPa、574.4MPa、626.2MPa、641.3MPa、527.1MPa）,且前屈体位时椎体所能承受的应力最小,左旋转时所能承受的应力最大。垂直压缩状况下T12椎体发生骨折, 前屈状态下T11发生骨折伴韧带损伤,后伸、左右侧屈和左右旋转状态下L1椎体发生骨折伴韧带损伤。骨折发生时,前纵韧带在后伸、左右侧屈状态下存在高应力区,后纵韧带在前屈状态下存在高应力区,横突间韧带和棘间韧带在前屈、左右侧屈、左右旋转状态下存在高应力区。结论：在构建包括重要韧带、椎间盘等软组织结构的脊柱胸腰段三维模型中,椎体松质骨、椎弓根及其周围骨皮质、韧带均存在高应力区,不同状态下所受应力最大椎体不同,发生骨折的椎体和韧带损伤也不同;L1椎弓根截面积最小,最易发生骨折。     

脊柱保护器对腰椎保护的有限元分析

[目的]应用三维有限元方法研究垂直加载状态下脊柱保护器对腰椎的保护作用。[方法]构建腰椎有限元模型和脊柱保护器有限元模型,将上述模型进行材料参数赋值。根据设定条件对研究对象进行垂直载荷的力学仿真试验,运算获得腰椎有限元模型的目标单元应力、应变。[结果]腰椎受垂直载荷条件下从接触瞬间到应力峰值过程中应力、应变随时间变化逐渐增大,两组比较L5椎体皮质骨承受等效应力最大,试验组为170 MPa,对照组为192 MPa。L2椎体松质骨承受等效应力最大,试验组为5.01 MPa,对照组为5.79 MPa。且L2椎体出现最大压缩主应变,试验组为2.66%,对照组为5.63%。统计分析,对照组与试验组的腰椎各节段皮质骨与松质骨应力均值比较,P0.05,差异有统计学意义。腰椎除第三节段压缩主应变P值为18.3,其余节段P0.05,差异有统计学意义。[结论]脊柱保护器可以明显减少垂直坠地时腰椎椎体所受的应力,分担载荷,对腰椎具有保护作用。     

L5新型自稳定人工椎体生物力学性能的有限元分析

目的:采用有限元分析评估L5椎体次全切术后置入新型自稳定人工椎体的力学性能以及对周围组织的影响,为腰骶段脊柱结核等疾病的治疗提供新的选择。方法:提取1名健康志愿者腰骶段CT薄层扫描数据进行三维重建,构建腰骶段(L3-S1)脊柱生理组有限元模型并进行有效性验证。将L5椎体及邻近椎间盘切除后,分别置入新型自稳定人工椎体和钛笼联合侧前方钉棒固定,构建新型假体组和钛笼组有限元模型。对所有模型的S1椎体下表面进行全部自由度约束,在L3椎体上表面给予400N的轴向载荷模拟生理压缩,然后再在L3椎体上表面施加8Nm的弯矩载荷,模拟腰椎前屈、背伸、左右侧弯及左右扭转六种运动,统计分析在不同运动方向上三组模型L4～S1的活动度及L4下终板和S1上终板的最大Von mise应力。结果:新型假体组和钛笼组L4～S1在前屈、背伸、侧弯、扭转方向上的活动度分别为0.38°～0.56°与0.53°～1.41°,较生理组(4.48°～10.12°)同部位活动动度明显减小。新型假体组和钛笼组L4下终板与S1上终板在前屈、背伸、左右侧弯、左右扭转方向上的最大Von Mises应力较生理组均明显增大,新型假体组在上述方向上终板的最大Von Mises应力较钛笼组明显减小。结论:自稳定人工椎体可以较好地重建手术部位的即刻稳定性,有效降低手术部位邻近终板的局部应力,理论上可以降低术后假体的下沉率,但其长期稳定性、抗疲劳性等力学性能尚需进一步研究。     

经皮椎体成形术后矢状面有限元分析

[目的]探讨经皮椎体成形术后脊柱矢状面参数变化。[方法]选取1例68岁脊柱矢状面形态为Roussouly分型Ⅱ型的L_1椎体骨质疏松性骨折的男性志愿者,全脊柱CT扫描,数据经处理建立胸腰椎和骨盆的三维模型,分别建立正常对照、轻度后凸和中度后凸的三维有限元模型,测量计算脊柱在肌力正常和肌力减小工况下各椎体的应力变化。[结果] SVA值轻度后凸模型为54.27 mm,中度后凸模型为81.37 mm。T_(5～9)各椎体的Mises应力均依次为:对照模型轻度后凸模型中度后凸模型(P0.05)。肌力正常组,三种模型椎体Von Mises应力自T_(5～9)依次显著增大(P0.05);肌力减小组中,T_7的Von Mises应力显著大于T_5、T_6、T_8、T_9椎体(P0.05)。肌力减小组中T_7的Von Mises应力显著大于肌力正常组(P0.05)。L_1椎体的Mises应力显著大于L_(2-5)椎体的Mises应力(P0.05),并且中度后凸模型显著大于轻度后凸模型和对照模型(P0.05)。肌力正常组的L_(2～5)椎体的Mises显著小于肌力减小组(P0.05)。[结论]PKP术后残存的后凸畸形会导致脊柱矢状面偏移增加,引发非相邻椎体的应力集中。     

颈椎后路单开门微型钛板固定的有限元分析

[目的]应用有限元方法研究颈椎后路单开门不同微型钛板固定对颈椎稳定的影响。[方法]选择符合条件的颈椎后路单开门治疗的脊髓型颈椎病患者,利用Mimics、Geomagic Studio、Creo 4.0、Hypermesh构建颈椎后路单开门微型钛板固定的有限元模型,在Abaaus 6.1中设定材料力学参数、边界条件及载荷,测量颈椎在屈曲和后伸状态下的活动度和Von Mises应力。[结果]前屈、后伸状态下,连续固定模型与正常模型各节段的活动度均显著小于间断固定模型(P0.05)。屈曲状态下,间断固定模型中固定椎板C_3、C_5、C_7的Von Mises应力显著高于正常模型及连续固定模型(P0.05),而非固定椎板C_4、C_6的Von Mises应力显著低于前两模型(P0.05)。屈曲和后伸状态下,间断固定模型C_3、C_5、C_7节段钛板的Von Mises应力均显著高于连续固定模型(P0.05)。[结论]颈椎后路单开门连续微型椎板固定的稳定性优于间断固定。     

有限元分析法对椎体成形术的力学评价

目的 利用有限元方法分析椎体成形术应力变化的影响,以指导临床实践.方法 在已建立的腰段骨质疏松性椎体压缩性骨折三维有限元模型(L1/L2,L2为骨折模型)上,模拟经皮穿刺椎体成形术(PVP)过程.在L2椎体中置入骨水泥,轴向加载500 N状态下记录手术前后病椎椎体终板、骨小梁、骨水泥及邻近椎体终板的应力变化.结果 手术前后,病椎终板的应力发生明显减少,而松质骨的应力没有明显的变化,单侧注入骨水泥与双侧注入骨水泥病椎终板的应力也不同,但相差并不大.邻近椎体终板手术前后无明显改变.结论 椎体形成术,由于注入骨水泥后,病椎的应力发生了转移,终板的应力明显减少,松质骨的应力没有明显变化,而单侧注入骨水泥与双侧注入骨水泥对病椎终板的应力影响不大,手术前后对邻近椎体的应力影响不大.     

人工颈椎间盘置换术对邻近节段生物力学影响的三维有限元分析

[目的]建立人工颈椎间盘置换术前、术后(C4～7)的三维有限元模型,分析颈椎间盘置换术的特点,并探讨术后对邻近节段生物力学的影响.[方法]选取1名行人工颈椎间盘置换的男性病人的术前、术后CT片,范围为C4～7,(包括椎体、邻近椎体和邻近椎间盘)分别建立术前、术后的三维脊柱功能单元的有限元模型.对模型加载2 N*m的力矩和10 N*m的转矩,分析其在垂直载荷、前屈、后伸、侧屈及旋转的情况下,手术前后的椎体的变化以及椎体皮质骨、松质骨、椎间盘、终板的应力改变,以及活动度的变化.[结果]手术后轴向负荷力线后移,人工间盘邻近椎体上下终板所受应力,以及邻近椎间盘所受应力有所增加,但所受压力、张力不明显.节段活动度的变化减小不明显.[结论]人工颈椎间盘置换术有效的改善了脊柱功能单位的生物力学性能,但需谨慎选择人工椎间盘的大小,并且最大限度保留终板骨性组织,以避免出现术后假体下沉、移位、脱出、节段后凸等不良影响.     

骨质疏松性椎体压缩骨折椎体强化术后不同椎体高度对相邻椎体应力影响的有限元分析

目的运用有限元分析骨质疏松性椎体压缩骨折椎体强化手术后,不同椎体高度对相邻椎体应力的影响。方法运用四例T12椎体经皮椎体后凸成形术(percutaneous kyphoplasty,PKP)患者术后CT影像资料,构建Genant半定量方法分级后,T_(12)椎体高度为0～3级,T_(11)～L_1节段三维有限元模型各一例。运用有限元分析方法,模拟施加垂直、屈曲、左侧屈、右侧屈四个不同状态的载荷后,观察椎体强化术后不同椎体高度相邻椎体的应力。结果 T_(12)椎体强化术后呈现T_(12)椎体高度丢失越严重,T_(11)椎体承受载荷越大的趋势,各种状态最大载荷均出现在T_(12)椎体高度为3级时,各级椎体高度之间载荷大小差异没有统计学意义(P0.05)。L_1椎体垂直和右侧屈状态压力呈现T12椎体高度丢失越严重,椎体承受载荷越大的趋势,而且T_(12)椎体高度为3级时垂直和右侧屈承受最大载荷,各级之间载荷大小差异没有统计学意义(P0.05)。总体呈现为骨折椎体高度丢失越多,相邻椎体应力越大的趋势。结论为了减少相邻椎体的应力,在进行椎体强化手术过程中应当尽可能恢复骨折椎体的椎体高度     

A probabilistic finite element analysis of the stresses in the augmented vertebral body after vertebroplasty

Fractured vertebral bodies are often stabilized by vertebroplasty. Several parameters, including fracture type, cement filling shape, cement volume, elastic moduli of cement, cancellous bone and fractured region, may all affect the stresses in the augmented vertebral body and in bone cement. The aim of this study was to determine numerically the effects of these input parameters on the stresses caused. In a probabilistic finite element study, an osteoligamentous model of the lumbar spine was employed. Seven input parameters were simultaneously and randomly varied within appropriate limits for >110 combinations thereof. The maximum von Mises stresses in cancellous and cortical bone of the treated vertebral body L3 and in bone cement were calculated. The loading cases standing, flexion, extension, lateral bending, axial rotation and walking were simulated. In a subsequent sensitivity analysis, the coefficients of correlation and determination of the input parameters on the von Mises stresses were calculated. The loading case has a strong influence on the maximum von Mises stress. In cancellous bone, the median value of the maximum von Mises stresses for the different input parameter combinations varied between 1.5 (standing) and 4.5 MPa (flexion). The ranges of the stresses are large for all loading cases studied. Depending on the loading case, up to 69% of the maximum stress variation could be explained by the seven input parameters. The fracture shape and the elastic modulus of the fractured region have the highest influence. In cortical bone, the median values of the maximum von Mises stresses varied between 31.1 (standing) and 61.8 MPa (flexion). The seven input parameters could explain up to 80% of the stress variation here. It is the fracture shape, which has always the highest influence on the stress variation. In bone cement, the median value of the maximum von Mises stresses varied between 3.8 (standing) and 12.7 MPa (flexion). Up to 75% of the maximum stress variation in cement could be explained by the seven input parameters. Fracture shape, and the elastic moduli of bone cement and of the fracture region are those input parameters with the highest influence on the stress variation. In the model with no fracture, the maximum von Mises stresses are generally low. The present probabilistic and sensitivity study clearly showed that in vertebroplasty the maximum stresses in the augmented vertebral body and in bone cement depend mainly on the loading case and fracture shape. Elastic moduli of cement, fracture region and cancellous bone as well as cement volume have sometimes a moderate effect while number and symmetry of cement plugs have virtually no effect on the maximum stresses.     

Biomechanical effect of vertebropiasty on the adjacent intervertebral levels using a three-dimensional finite element analysis

Objective: To investigate the biomechanical effect of different volume, distribution and leakage to adjacent disc of bone cement on the adjacent vertebral body by three-dimensional osteoporosis finite element model of lumbar. Methods: L4 -L5 motion segment data of the cadaver of an old man who bad no abnormal findings on roentgenograms were obtained from computed tomography (CT) scans. Three-dimensional model of L4-L5 was established with Mimics software, and finite element model of L4-L5 functional spinal unit (FSU) was established by Ansys 7. 0 software. The effect of different loading conditions and distribution of bone cement after vertebroplasty on the adjacent vertebral body was investigated. Results: This study presented a validated finite element model of L4-L5 FSU with a simulated vertebroplasty augmentation to predict stresses and strains of adjacent untreated vertebral bodies. The findings from this FSU study suggested the endplate and disc stress of the adjacent vertebral body was not influenced by filling volume of bone cement but unipedicle injection and leakage to the disc of bone cement could concentrate the stress of adjacent endplate. Conclusions: Asymmetric distributions and leakage of cement into intervertebral disc can improve the stress of endplate in adjacent vertebral body. These results suggest that optimal biomechanical configuration should have symmetric placement and avoid leakage of cement in operation.     

The biomechanical effects of kyphoplasty on treated and adjacent nontreated vertebral bodies

It remains unclear whether adjacent vertebral body fractures are related to the natural progression of osteoporosis or if adjacent fractures are a consequence of augmentation with bone cement. Experimental or computational studies have not completely addressed the biomechanical effects of kyphoplasty on adjacent levels immediately following augmentation. This study presents a validated two-functional spinal unit (FSU) T12-L2 finite element model with a simulated kyphoplasty augmentation in L1 to predict stresses and strains within the bone cement and bone of the treated and adjacent nontreated vertebral bodies. The findings from this multiple-FSU study and a recent retrospective clinical study suggest that changes in stresses and strains in levels adjacent to a kyphoplasty-treated level are minimal. Furthermore, the stress and strain levels found in the treated levels are less than injury tolerance limits of cancellous and cortical bone. Therefore, subsequent adjacent level fractures may be related to the underlying etiology (weakening of the bone) rather than the surgical intervention.     

Do we have to pursue complete reduction after PVA in osteoporotic vertebral compression fractures: a finite element analysis

BackgroundConsensus regarding the optimal amount of bone cement and vertebral height in the treatment of osteoporotic vertebral compression fractures (OVCFs) is lacking. Our purpose was to explore the optimal amount of bone cement and vertebral height in OVCF after percutaneous vertebral augmentation (PVA).MethodsA three-dimensional finite element model of the L1-L3 segments was constructed from CT scans of aging osteoporosis patients. Four different postoperative vertebral height models were simulated according to Genant semiquantitative grades 0, 1, 2, and 3. The volume of bone cement filling ranged from 3 ml to 6 ml. These models evaluated the von Mises stress of injured vertebral bodies, adjacent vertebral bodies and intervertebral discs under flexion, extension, left flexion, and right flexion after PVA.ResultsWhen the bone cement content was held constant, as the height of the vertebral body decreased, the stress of the L2 vertebral body decreased during left flexion and right flexion, but the stress of the L2 vertebral body increased and decreased during flexion and extension. As the height of the vertebral body decreased, the stress of the L1-L2 intervertebral disc increased. There was no significant change in the stress of other adjacent vertebrae or intervertebral discs. When the Genant grade was 0, 1, or 2 (3 ml and 4 ml), the stress of the overall vertebral body was closest to normal.ConclusionsWhen the height of the vertebral body is restored to the same height, a bone cement filling volume of 3 ml to 6 ml is suitable and will not produce a significant change in the stress of the vertebral body or adjacent vertebral body. As vertebral body height was lost, it may promote the degeneration of the intervertebral disc above the injury vertebrae after PVA. It is appropriate for the height of the vertebral body to return to Genant grade 0 or Genant grade 1 after surgery. When the height of the vertebral body has Genant grade 2 status, it was best to use 3 ml to 4 ml of bone cement filling. Therefore, when treating OVCFs, clinicians do not need to pursue complete reduction of the vertebral body. It is also important to verify the biomechanics results in clinical studies.     

Biomechanical effect of vertebroplasty on the adjacent intervertebral levels using a three.dimensional finite element analysis

Objective： To investigate the biomechanical effect of different volume, distribution and leakage to adjacent disc of bone cement on the adjacent vertebral body by threedimensional osteoporosis finite element model of lumbar. Methods ： L4-L5 motion segment data of the cadaver of an old man who had no abnormal findings on roentgenogrmns were obtained from computed tomography （CT） scans. Three-dimensional model of L4-L5 established with Mimics software, and finite element model of L4-L5 functional spinal unit （FSU） was established by Ansys 7. 0 software. The effect of different loading conditions and distribution of bone cement after vertebroplasty on the adjacent vertebral body was investigated. Results： This study presented a validated finite element model of L4-L5 FSU with a simulated vertebroplasty augmentation to predict stresses and strains of adjacent untreated vertebral bodies. The findings from this FSU study suggested the endplate and disc stress of the adjacent vertebral body was not influenced by filling volume of bone cement but unipedicle injection and leakage to the disc of bone cement could concentrate the stress of adjacent endplate. Conclusions： Asymmetric distributions and leakage of cement into intervertebral disc can improve the stress of endplate in adjacent vertebral body. These results suggest that optimal biomechaulcal configuration should have symmetric placement and avoid leakage of cement in operation.     

基于CT影像动态膝关节有限元模型的构建及仿真力学分析

目的:基于CT影像资料构建动态性膝关节有限元模型,并进行模型的有效性验证和初步的有限元分析,为膝关节的生物力学研究提供仿真模型和基础数据。方法:选取1名健康男性膝关节CT资料,借助Mimics 19.0和Hypermesh 12.0等软件,从膝关节的三维模型构建入手,经几何重建、逆向工程、网格划分、材料定性等步骤,建立高仿真的有限元模型。通过确定边界条件和扭矩加载产生动态性的屈膝模型,并进行模型的有效性验证。予有限元模型施加近似屈膝活动时所承受的载荷(500 N),研究分析不同屈膝角度下胫股关节和髌股关节的生物力学变化。结果:基于CT影像并结合解剖特性建立了膝关节有限元模型,模型包括骨、韧带、软骨、半月板和髌骨支持带等三维单元,在确立边界条件后施加不同扭矩产生了不同屈膝状态下的有限元模型。根据等同工况(屈膝30°,股四头肌腱受200N牵张)加载显示髌骨的应力峰值为2.209 MPa,平均Mises应力为1.132 MPa;股骨滑车的应力峰值为1.405 MPa,平均Mises应力0.936 MPa,与既往研究比较差异性在1%～13.5%,证明模型的有效性。动态性的模型加载发现:胫股关节的Mises应力随屈膝角度增加而下降;而髌股关节的Mises应力与屈膝角度正相关,不同屈膝角度下各软骨应力面的Mises应力对比,差异均有统计学意义(P0.05)。结论:研究建立的有限元模型结构更趋完整,可有效模拟动态性膝关节的生物力学特性,为膝关节进一步的仿真力学研究提供了支撑。     

枢椎有限元模型建立及齿突骨折的有限元分析

目的 建立并验证枢椎三维有限元模型,并应用该模型探讨齿突垂直和水平方向不同角度载荷下的损伤机制和骨折类型.方法 对健康成年男性颈部进行CT扫描,层厚0.6mm,无间隔.将DICOM图像数据导入Mimics软件中,生成网格化的枢椎表面三维图像,再经ANSYS ICEM CFD处理,生成包括皮质骨和松质骨的实体模型.模拟体外生物力学试验验证模型.模型验证后,通过对齿突前部垂直和水平方向上施加不同角度的载荷,分析各种条件下齿突的应力分布并探讨相应的骨折类型.结果 (1)模型验证结果与体外生物力学试验的数据基本一致,后伸载荷下产生Ⅲ型齿突骨折,最大应力为123 Mpa;倾斜45°载荷下产生Ⅱ型齿突骨折,最大应力为121 Mpa,与皮质骨的屈服应力(138 Mpa)分别相差11%和12%.(2)齿突前部垂直和水平方向不同角度外力加载的应力分布图显示,应力集中区域可发生转变,预示骨折类型可能由Ⅲ型转变为Ⅱ型,且最大应力值逐渐增大.皮质骨承受主要应力.结论 我们建立的枢椎有限元模型经过验证可以很好地模拟枢椎的生物力学特性,其中包括皮质骨和松质骨结构.两种力学加载模式的应力分布图显示随着作用力角度的变化,会出现齿突骨折类型的转变,预示外力作用的方向是决定齿突骨折类型的关键因素.