经皮椎体增强术后生物力学有限元模型的建立及应用

目的建立腰2椎体骨质疏松致压缩骨折患者应用骨水泥注入治疗前后生物力学有限元模型,观察对比病椎与相邻椎体治疗前后应力的改变情况。方法随机选取本院1例70岁腰2椎体骨质疏松致压缩骨折经皮实施椎体成形术治疗患者,双侧腰2椎弓根予以少量骨水泥注入,2年后随访其病椎与相邻的椎体均未见新发骨折,并且局部无疼痛。参照治疗前后患者腰椎CT资料,建立三维生物力学有限元模型,并模拟患者腰椎旋转、屈伸及左右侧屈,观察对比病椎与相邻椎体治疗前后应力的改变情况。结果成功建立腰2椎体骨质疏松致压缩骨折予以少量骨水泥注入治疗前后的三维生物力学有限元模型。共计211618个单元生成,其中20914个4节点壳单元、190107个10节点体单元、597个杆单元。骨水泥注入后,腰2椎体的伸、屈及侧屈应力较前增加（P均〈0．05）,椎体旋转时应力治疗前后比较无统计学差异（P〉0．05）;腰1及腰3椎体伸、屈、旋转及侧屈时应力治疗前后无差异（P〉0．05）。结论生物力学有限元模型有助于腰椎骨质疏松致压缩骨折患者骨水泥治疗的预后判定。关键词：腰椎骨折;骨质疏松;骨水泥;生物力学;三维有限元     

经皮椎体成形术治疗骨质疏松性压缩性骨折的有限元力学分析

目的建立胸腰段骨质疏松性椎体压缩性骨折的病理三维有限元模型,分析手术前后病椎及邻近椎体应力变化情况。方法取CT三维重建资料通过软件MIMICS10.0建立椎体的三维实体模型,以三维有限元分析软件ANSYS12.0模拟经皮椎体成形术(PVP)过程在腰1(L1)椎体中置入不同容量骨水泥(2、4、6、8 ml),分析轴向压缩直立、前屈、后伸、侧弯、旋转5种加载状态下手术前后相邻椎体的应力变化。结果小剂量骨水泥注入(2、4 ml),病椎所受应力逐渐增加,而较大治疗量骨水泥注射入(6、8 ml),随着病椎硬度及刚度加强,其所受应力逐渐下降;而临近椎体在骨水泥注入量逐渐增加过程中,所受应力未见明显改变。结论对于老年骨质疏松性压缩性骨折的力学研究,三维有限元力学分析具有良好的应用前景及临床价值;在能够避免大治疗剂量骨水泥注入所带来并发症(如渗漏)前提下,4⁸ ml骨水泥注入量更加有效,且不增加邻近椎体骨折的风险。     

椎间小关节植骨在胸腰椎骨折手术中的应用

目的探讨椎间小关节植骨在治疗胸腰椎骨折中的效果。方法对43例胸腰椎爆裂性骨折患者行手术治疗。术中在完成复位和内固定后,将所切除的自体椎板和棘突骨片行小关节V型截骨及小关节突间植骨术。术后采用CT和X线检查评估脊柱融合情况。结果 43例患者中40例确定为骨性融合,3例未融合。结论小关节部位植骨符合脊柱融合的生物力学原理,操作安全,使用方便,用于胸腰椎骨折效果确切。     

骨质疏松性椎体骨折后不同躯体姿势对椎体局部应力的影响

获取1例健康老年女性胸腰段CT平扫数据,通过Mimics及Geomagic对胸腰段椎体进行三维实体化,并修饰模型,使之符合分析要求,导入有限元软件ANSYS分析,通过改变椎体骨质、椎间盘的物理属性设定,获得健康及退变腰椎在不同躯体姿势的应力分布情况.结果 显示正常骨质、正常间盘、前屈姿势下,椎体上表面最大应力几乎相同,且应力分布趋向于中央;正常骨质及骨质疏松骨质在退变间盘、前屈姿势下,压缩骨折与非压缩骨折相比,其应力分布更趋于前方,而且其最大应力值较非压缩骨折最大应力值增大了近20%.认为骨质疏松性椎体压缩性骨折后,前屈姿势能够造成椎体局部应力的显著增大,可能导致再骨折风险的增加.     

以胸椎压缩性骨折为主要表现的SAPHO综合征一例

1病例介绍患者,女,24岁,因“上背部疼痛8月”于2017-08-28入院。患者8个月前因弯腰提重物引起胸背部疼痛,于当地医院行胸椎磁共振成像(MRI)示胸椎第6椎体(T 6)压缩性骨折并椎管狭窄、胸髓受压,诊断为“胸椎压缩性骨折”。嘱患者卧床休息2个月,期间疼痛稍有缓解。近1周疼痛加重,1 d前不能自行活动,遂来我院就诊。查体:脊柱胸腰段疼痛,被迫处于固定体位,胸椎第5/6椎体、腰段椎体棘突、棘间及椎旁明显压痛、轻叩击痛,右胸锁关节肿胀、轻压痛;双小腿前侧可见散在银屑病样皮损,淡红色斑片状,被覆白屑,薄膜现象,点状出血(见图1),双足底陈旧性脓疱性皮损瘢痕(见图1),余未见明显异常。     

基于CT精细扫描构建人体胸腰段脊柱三维有限元模型的方法及意义

目的探讨基于CT精细扫描构建人体胸腰段脊柱三维有限元模型的方法及临床意义。方法将以各向同性分辨率0．625mm薄层扫描所得的层厚0．65mm人体胸腰段连续断层210层Dicom格式CT图像,直接读入Mimics后界定骨组织阈值、提取各层面轮廓线、图像边缘分割、选择性编辑及补洞处理,去除冗余数据,三维化处理后获得胸腰段三维几何面网格模型,将其保存为后缀名．1is的Ansys文件,直接导入Ansys有限元分析软件进行体网格划分,再将体网格转入Mimics,根据CT值赋值,再次导入Ansys添加韧带、关节约束后生成三维有限元模型。结果快捷建立了外形逼真、计算精确的人体胸腰段脊柱三维有限元模型。结论应用精细CT扫描技术,图像Dicom标准,Mimics软件能直接与Ansys软件进行对接,并能根据CT值直接赋值使胸腰段脊柱三维有限元模型的建立更加快捷、精确。     

伤椎椎弓根固定技术治疗多节段胸腰椎骨折的探讨

手术治疗多节段胸腰椎骨折或合并脱位,因椎体周围的前纵韧带、椎间盘、后纵韧带、椎旁肌肉、棘突间韧带撕裂,是一种不稳定性骨折,故常需手术开放复位、固定、融合。2004年3月-2006年10月,我们采用经后路包括骨折椎体的椎弓根固定技术进行复位同时行后外侧植骨融合的手术方法治疗这一类型骨折,至今已13例,效果满意。现报告如下。     

双节段颈椎椎间融合内固定对邻近下位关节突关节生物力学的影响

目的观察双节段颈椎椎间盘摘除前路椎间融合内固定对邻近下位节段关节突关节生物力学的影响。方法11具新鲜完整的成人下颈段标本,分别制成C4~5、C5~6椎间盘完整、椎间融合两个模型组,将压力传感器置入C6~7关节突关节内,在模型上分级施加载荷,测量轴向、侧弯、前屈和后伸加载载荷下C6~7关节突关节内的压力。结果在轴向、侧弯、前屈和后伸加载下,邻近下位节段关节突关节内的压力随着施加载荷的增大而增大。C4~5、C5~6椎间融合组与椎间盘完整组相比,邻近下位节段关节突关节内的压力高（P均〈0.05）。结论颈椎双节段椎间盘摘除融合内固定后邻近下位关节突关节压力增加,可能是多节段颈椎融合术后邻近节段发生退变或退变加速的原因之一。     

人工腰椎间盘置换术后腰椎小关节应力分布变化分析

目的 探讨人工腰椎间盘（AID）置换术（ADR）对腰椎节段小关节应力的影响。方法新鲜成人腰椎尸体标本1具,利用有限元软件Ansys,建立L4／L5正常节段三维有限元模型、髓核摘除术后模型及AID置换的腰椎节段有限元模型（根据AID放置位置分为前置、中置和后置模型）。在L4椎体上终板施加400N的轴向压缩载荷,分别向模型施加前屈、后伸、右旋转力矩,力矩大小均为6Nm。分析各状态下腰椎小关节的应力分布情况。结果五个模型在前屈和右旋转时,小关节均产生较大应力,尤其是旋转时,后伸时小关节应力均较小;与正常腰椎节段相比,髓核摘除术后腰椎节段在前屈、后伸、旋转时小关节的应力均增加。与髓核摘除术相比较,AID前置在前屈时小关节应力减小,而在后伸和右旋转时应力增加;AID中置和后置前屈时小关节应力增加,而在后伸和右旋转时小关节应力均减小。结论AID具有一定抗旋转载荷性能,术中将其放置于椎间隙中央或中央偏后可降低术后小关节应力。     

AF椎弓根螺钉内固定系统用于胸腰段脊柱骨折39例疗效观察

目的探讨AF椎弓根螺钉内固定系统（简称AF系统）用于胸腰段脊柱骨折的疗效及机制。方法对39例胸腰段脊柱骨折患者采用AF系统行复位固定术,观察畸形纠正情况、神经功能恢复情况和并发症发生情况。结果术后椎体前后凸高度均明显增加,椎体后倾Cobb’s角明显减小,侧凸角度明显减小,神经功能Frankel分级均明显降低,P均〈0．01。未出现明显并发症。结论AF系统用于胸腰段脊柱骨折效果确切,手术切口短,操作简单,椎体复位效果好,固定牢固,可减少椎管减压及植骨。     

Efficacy of risedronate in men with primary and secondary osteoporosis: results of a 1-year study

Osteoporosis is prevalent in men with an estimated one in eight men older than 50 years suffering from osteoporotic fracture, and a higher mortality rate after fracture among men compared with women. There are few approved therapies for osteoporosis in men. This observational study assesses the efficacy and safety of risedronate in the treatment of men with primary and secondary osteoporosis. A single-center, open label, randomized, prospective 1-year study was conducted in men with primary or secondary osteoporosis. Patients were randomized to risedronate (risedronate 5 mg/day plus calcium 1,000 mg/day and vitamin D 800 IU/day) or control groups (alfacalcidol 1 μg/day plus calcium 500 mg/day or vitamin D 1,000 IU/day plus calcium 800 mg/day). Bone mineral density (BMD) measurements, X-rays of the spine, a medical history and physical exam, and patient self-assessments of back pain were performed at baseline and 12 months. Blinded semi-quantitative fracture assessment was conducted by a radiologist. A total of 316 men with osteoporosis were enrolled in the trial (risedronate, n=158; control, n=158). At 1 year lumbar spine BMD increased by 4.7% in the risedronate group versus an increase of 1.0% in the control group (P<0.001). Significant increases in BMD at the total hip and femoral neck were also observed with risedronate compared with the control group. The incidence of new vertebral fracture in the risedronate group was reduced by 60% versus the control group (P=0.028). Daily treatment with risedronate for 12 months significantly increased BMD at the lumbar spine, femoral neck and total hip and significantly reduced the incidence of new vertebral fractures. This is the first prospective, randomized, controlled trial to demonstrate a significant reduction in vertebral fractures in 1 year in men with primary or secondary osteoporosis.     

Simulated and Experimental Investigation of Mechanical Properties for Improving Isotropic Fracture Strength of 3D-Printed Capsules

Three-dimensional (3D) printer-based self-healing capsules, embedded in cement composites, were proposed to heal cracks, as they allow for various structural designs of capsules, repeatable fabrication, and strength analysis. Out of many 3D printing methods, such as fusion deposition modeling (FDM), powder layer fusion, and PolyJet printing, FDM was used to design, analyze, and produce new self-healing capsules, which are widely used due to their high-speed, low-cost, and precise manufacturing. However, the PLA extruded in the FDM had low adhesion energy between stacked layers, which caused a degradation of the performance of the self-healing capsule, because it had different strengths depending on the angle between the stacked layers and the applied load within the concrete structure. Therefore, in this paper, specimens were produced, in accordance with ASTM specifications, using the FDM PLA method, and mechanical properties were obtained through tensile, shear, and compression tests. Additionally, the isotropic fracture characteristics of the four types of capsules were analyzed through finite element method analysis. Subsequently, the 3D-printed capsules were produced, and the fracture strength was analyzed in the x, y and z directions of the applied load through a compression test. As a result, the newly proposed capsule design was verified to have an isotropic fracture strength value of 1400% in all directions compared to conventional spherical thin film capsules     

绝经后妇女脊椎压缩性骨折与骨密度的关系

目的探讨绝经后妇女脊椎压缩性骨折与骨密度（BMD）的关系。方法为病例一对照研究，入选250例有脊椎压缩性骨折的绝经后妇女，另有250名无脊椎压缩性骨折的绝经后妇女作为对照组。两组均有胸腰椎正侧位X线摄片，并应用双能X线吸收仪检测腰椎1～4和左股骨近端各部位BMD。结果脊椎压缩性骨折组身高、体重、腰椎2～4和股骨近端各部位BMD值均显著低于对照组（均P〈0．01）。腰椎2～4BMD是发生脊柱骨折的预报因子（r=-0．416，P〈0．01）。身高和全髋部BMD与骨折次数和骨折椎体数目呈负相关（均P〈0．01）。按股骨颈和全髋部BMD值，骨折组骨质疏松检出率各为50．8％和50．4％；另外剔除在腰椎2～4发生椎体骨折53例，按腰椎2～4BMD检出骨质疏松占64．5％。同时，腰椎2～4、股骨颈或全髋部BMD值低于-2．5s者发生脊柱压缩性骨折的风险分别是BMD正常者的4．76、2．36和3．52倍。结论腰椎呈低骨量是发生脊椎压缩性骨折的重要危险因素。身高的下降和全髋部低BMD值是骨折发生次数和受累椎体数目的危险因子；对绝经后妇女在重视BMD测量的同时，应重视脊柱X线正侧位检查。     

三叉形股骨膨胀式空心加压螺钉强化股骨颈骨折扭转刚度的研究

目的评价三叉形股骨膨胀式空心加压螺钉对股骨颈骨折扭转刚度的影响。方法选用新鲜猪股骨标本12个制成标准股骨颈基底部骨折模型,随机分为对照组和实验组。对照组给予A0空心加压螺钉固定,实验组给予自制膨胀式空心加压螺钉固定。置两组标本于扭转力学试验机上,测定2Nm力矩作用下各组的扭转刚度。结果在2Nm扭矩作用下,实验组扭转刚度为（0．62±0．05）Nm／度,对照组为（0．51±0．09）Nm／度,P〈0．05。结论三叉形股骨膨胀式空心加压螺钉应用于股骨颈骨折内固定时其扭转刚度明显优于传统AO空心加压螺钉。     

Fracture Behaviour of Real Coarse Aggregate Distributed Concrete under Uniaxial Compressive Load Based on Cohesive Zone Model

Two-dimensional meso-scale finite element models with real aggregates are developed using images obtained by digital image processing to simulate crack propagation processes in concrete under uniaxial compression loading. The finite element model is regarded as a three-phase composite material composed of aggregate, mortar matrix and interface transition zone (ITZ). Cohesive elements with traction–separation laws are used to simulate complex nonlinear fracture. During the experiment, digital image correlation (DIC) was used to obtain the deformation and cracks of the specimens at different loading stages. The concept of strain ratio is proposed to describe the effectiveness of simulation. Results show that the numerical strain ratio curve and stress–strain curves are both in good agreement with experimental data. The consistency between the cracks obtained by simulation and those obtained by DIC shows the good performance of cohesive elements as well as the effectiveness of simulation. In summary, the model is able to provide accurate predictions of the whole fracture process in concrete under uniaxial compression loading.     

Numerical Study on Crack Propagation in Brittle Jointed Rock Mass Influenced by Fracture Water Pressure

The initiation, propagation, coalescence and failure mode of brittle jointed rock mass influenced by fissure water pressure have always been studied as a hot issue in the society of rock mechanics and engineering. In order to analyze the damage evolution process of jointed rock mass under fracture water pressure, a novel numerical model on the basis of secondary development in fast Lagrangian analysis of continua (FLAC3D) is proposed to simulate the fracture development of jointed rock mass under fracture water pressure. To validate the feasibility of this numerical model, the failure process of a numerical specimen under uniaxial compression containing pre-existing fissures is simulated and compared with the results obtained from the lab experiments, and they are found to be in good agreement. Meanwhile, the propagation of cracks, variations of stress and strain, peak strength and crack initiation principles are further analyzed. It is concluded that the fissure water has a significant reducing effect on the strength and stability of the jointed rock mass.     

Numerical simulation and biomechanical analysis of locking screw caps on clavicle locking plates

Background:The risk of displaced and comminuted midshaft clavicle fractures is increased in high-energy traumas such as sport injuries and traffic accidents. Open reduction and plate fixation have been widely used for midshaft clavicle fractures. Among various plates for clavicle shaft fractures, superior locking compression plates (LCPs) have been mostly used. In plate fixation, nonunion caused by implant failure is the most difficult complication. The most common reasons for metal plate failure are excessive stress and stress concentration caused by cantilever bending. These causes were easily addressed using a locking screw cap (LSC).Methods:The clavicle 3-dimensional image was made from a computed tomography scan, and the clavicle midshaft fracture model was generated with a 10-mm interval. The fracture model was fixed with a superior LCP, and finite element analysis was conducted between the presence (with LSC model) and absence (without LSC model) of an LSC on the site of the fracture. The stresses of screw holes in models with and without LSCs were measured under 3 forces: 100 N cantilever bending force, 100 N axial compression force, and 1 N·m axial torsion force. After the finite element analysis, a validation test was conducted on the cantilever bending force known as the greatest force applied to superior locking plates.Results:The mean greatest stress under the cantilever bending force was significantly greater than other loading forces. The highest stress site was the screw hole edge on the fracture site in both models under the cantilever bending and axial compression forces. Under the axial torsional force, the maximum stress point was the lateral first screw hole edge. The ultimate plate stress of the with LSC model is completely lower than that of the without LSC model. According to the validation test, the stiffness, ultimate load, and yield load of the with LSC model were higher than those of the without LSC model.Conclusions:Therefore, inserting an LSC into an empty screw hole in the fracture area reduces the maximum stress on an LCP and improves biomechanical stability.     

枢椎三维有限元模型的建立

目的建立并验证枢椎三维有限元模型,以期应用于临床相关的生物力学实验研究。方法对健康成年男性颈部进行CT扫描,层厚0.6 mm,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进行验证模型。结果所建模型外观清晰逼真,几何相似性好。所建的枢椎有限元模型能够通过验证,与体外生物力学实验结果基本吻合,可进一步行各种上颈椎有限元力学分析。结论枢椎有限元三维模型的建立为临床提供了一种便捷而精确的方法,为下一步生物力学分析提供了条件。     

A case of post-pregnancy osteoporosis combined with ankylosing spondylitis

Post-pregnancy osteoporosis is not a common disease and is hard to diagnosis because their specific situation is post-partum and lactation. It commonly occurs on lumbar spine within a few months after the birth of a patient’s first child and it could lead to be fracture after minor trauma. Although its etiology is not clear, it would not be of sufficient magnitude to cause fractures unless the woman already had a substantial decrease in bone mass. Also, it is rare to be combined with ankylosing spondylitis. Ankylosing spondylitis has a higher risk of osteoporosis and vertebral fracture which increased with the duration of disease. We report a case of post-pregnancy osteoporosis with multiple spinal compression fracture in association of ankylosing spondylitis.