轴向应力促进胫骨骨折愈合的三维有限元力学参数优化研究

目的通过有限元方法建立胫骨骨折愈合仿真模型,利用有限元分析不同频率与大小组合的轴向应力促进骨折愈合过程,以期获得最佳理论参数。方法对一名健康志愿者胫骨进行CT扫描,通过Mimics、Geomagic、Abaqus等有限元软件建立胫骨骨折钢板内固定实体模型;观察胫骨骨折愈合过程中骨痂内部应力、应变及骨折端位移,比较骨折愈合仿真所获得的愈合模式图及骨痂单元数变化。结果通过有限元分析计算了胫骨骨折间隙内骨痂组织的应力、应变及位移,观察分析200 N、1 Hz组合参数分化的成熟骨组织细胞单元数是最多的。结论建立胫骨骨折愈合的三维有限元模型,通过三维有限元分析所获得的200 N、1 Hz为最佳理论参数组合,为临床个体化促进胫骨骨折愈合提供理论依据。     

单枚外固定支架螺钉的三维有限元模型的初步建立及应用

目的建立单枚外固定支架螺钉钻入胫骨干的三维有限元模型。方法运用Pro/E,Geomagic Studio工程软件,Ansys Workbench13建立胫骨三维皮质螺钉装配体的有限元模型,并施加轴向载荷观察结果。结果胫骨干生成1217个体网格,螺钉生成270个体网格,应力云图显示螺钉的最大应力位于螺钉与皮质骨接触处,形变最明显的位置处于螺钉尾部。试验中通过对螺钉加载不同载荷,测量分析,得出螺钉最大应力及螺钉总变形量与轴向载荷呈正相关(线性关系)。结论三维胫骨螺钉装配体有限元为后期的不同材质螺钉,不同负荷螺钉与胫骨皮质应力的定量分析研究提供依据,从而为筛选出适宜的外固定支架螺钉材质实现手拧自攻螺钉创造条件。     

基于MRI图像的计算机膝关节建模新思路

目的研究以有限元分析为目标的使用Mimics软件三维重建膝关节的方法。 方法导入MRI图像到Mimics软件,利用"3D磁性套索"工具建立骨组织模型,利用"动态区域增长"工具建立软组织模型。 结果所得到膝关节三维模型包括了股骨、胫骨、髌骨、股骨软骨、胫骨软骨、前、后交叉韧带,内、外侧副韧带,及内外侧半月板,骨与软骨间、各韧带起止处紧密贴合,形态逼真。 结论在Mimics软件导入MRI图像建出膝关节三维模型更完整,骨组织和软组织间界限清晰,更适合后续有限元网格划分及分析。     

正常人足踝部有限元模型的构建研究

目的 研究足踝部有限元模型的构建方法,为足踝部生物力学提供一个数字化研究平台. 方法 获取一名30岁男性志愿者的右足螺旋CT扫描图像,利用Mimics软件重建出足踝部28块骨骼及外围软组织的三维结构,通过Solidworks处理后导入Ansys的Workebench模块,建立足踝部三维有限元模型.在模型中还通过解剖和文献数据模拟建立各关节软骨、韧带、跖筋膜、小腿骨间膜,然后模拟踝关节正常站立状态下受力,选择相应边界条件进行加载分析. 结果建立了一个包含骨与外围软组织等复合结构的正常人体右足三维有限元模型,相埘客观地反映了人体足踝部的基本解剖结构和力学特性.模拟人体站立状态垂直加载600 N载荷于胫骨下端的上截面,踝关节胫骨下关节面应力主要分布于中部及前外侧,最大应力为3.97 MPa,平均接触应力为1.52 MPa,接触面积为343.6 mm~2. 结论本研究所建立的止常人体足躁部三维有限元模型经验证结果可靠,可进一步用于足踝部损伤的研究.     

腭部种植支抗三维有限元模型的建立

目的：建立含腭部种植体(支抗种植体)的上领骨三维有限元模型，为进一步研究腭部种植体加强磨牙支抗的生物力学特征打下基础。方法：采用螺旋CT断层扫描、计算机图像处理、计算机辅助设计和有限元软件处理。建立含腭部种植体的上领骨三维有限元模型。结果：建立了符合生物力学研究需要的腭部种植支抗的三维有限元模型。结论螺旋CT扫描、图像数字化处理及CAD技术提供了一种准确可靠的建立三维有限元模型的方法。本实验有限元模型的建立为上领骨种植体的生物力学研究提供了一个平台。     

胫骨平台后外侧骨折带状钢板固定的有限元分析

[目的]研究胫骨平台后外侧骨折不同内固定模型在轴向载荷作用下骨块位移、钢板应力的分布规律,探讨符合力学原理的最佳内固定。[方法]应用有限元相关软件建立胫骨平台后外侧骨折有限元模型,包括Ⅰ、Ⅱ和Ⅲ度骨折,并分别用三种钢板固定方式,包括外侧解剖钢板、带状钢板和后侧支撑钢板。设定边界及载荷条件,模拟体重60 kg的慢跑步(1 200 N)情况下胫骨平台后外侧骨折三种固定方式下胫骨平台位移、应力分布及钢板螺钉承受应力情况。[结果]在有限元软件中构建了胫骨平台后外侧骨折钢板固定三维有限元模型;三种固定模型在轴向载荷为1 200 N时,带状钢板与外侧解剖型钢板及后方重建支撑钢板的轴向位移接近;随着载荷增大,三种固定方式下胫骨与螺钉所承受的应力值也随之增大,但各组总体位移与最大应力值均比较接近。[结论]利用有限元相关软件建立的胫骨平台后外侧骨折有限元模型及钢板内固定有限元模型能有效模拟骨折真实情况。使用带状钢板固定后外侧胫骨平台骨折能达到外侧解剖型钢板后方重建钢板固定的生物力学效果。     

活动平台单髁膝关节置换三维有限元模型的建立

[目的]建立活动平台单髁膝关节置换三维有限元模型,并验证其有效性,作为行进一步生物力学分析的基础。[方法]对1名健康成年男性志愿者左膝关节CT和MRI平扫,以Dicom格式保存数据。利用Mimics 17.0行影像学处理及三维重建,得到正常膝关节各结构STL三角网格模型,再利用Rapidform 2006行曲面拟合生成实体模型,经Abaqus 6.10建立正常膝关节有限元模型,设定边界条件及载荷,计算载荷分配、接触应力与接触面积,与文献结果对比进行验证。然后利用Abaqus 6.10在经过验证的正常膝关节模型基础上建立活动平台单髁膝关节置换三维有限元模型,行网格划分及赋值,设定边界条件和载荷,计算胫骨内外侧间室载荷分配及应力,与文献结果对照验证模型的有效性。[结果]在经过验证的正常膝关节模型基础上成功建立了活动平台单髁膝关节置换三维有限元模型,包含了膝关节的主要结构,整个模型共218 043个单元和229 524个节点,于股骨施加1 000 N垂直压缩载荷,计算胫骨内外侧间室载荷分配及应力,与既往文献中研究结果相比较为接近。[结论]本研究所建立活动平台单髁膝关节置换三维有限元模型具有创新性及有效性,可用于进一步生物力学模拟和分析。     

CT扫描资料间接法建立股骨上段三维有限元模型

目的 建立正常人体股骨上段三维有限元模型，作为今后该部位进一步有限元分析的基础。方法 采用活体股骨上段为对象，应用CT扫描技术，图形数字化方法获取股骨上面三维坐标，输入有限元分析软件ANSYS5．6，通过确定材料特性参数和网格化，建立完整的股骨上段三维有限元模型。结果 建立的三维有限元模型几何形状与材料特性还原良好，网格大小可根据研究者的需要在一定范围内自行调整，可以满足有限元分析的需要。结论 采用CT扫描资料建立三维有限元模型切实可靠；间接法建立三维有限元模型比直接法更加简便，高效，可以更精确地模拟复杂几何形态的实体。     

腭部种植支抗三维有限元模型的建立

目的建立含腭部种植体(支抗种植体)的上颌骨三维有限元模型,为进一步研究腭部种植体加强磨牙支抗的生物力学特征打下基础.方法采用螺旋CT断层扫描、计算机图像处理、计算机辅助设计和有限元软件处理,建立含腭部种植体的上颌骨三维有限元模型.结果建立了符合生物力学研究需要的腭部种植支抗的三维有限元模型.结论螺旋CT扫描、图像数字化处理及CAD技术提供了一种准确可靠的建立三维有限元模型的方法,本实验有限元模型的建立为上颌骨种植体的生物力学研究提供了一个平台.     

膝关节后外侧复合体有限元模拟重建的研究

目的建立一个包括后外侧复合体(posterolateral complex,PLC)的完整膝关节三维有限元模型,并在该模型上进行模拟重建生物力学分析。方法以1名26岁男性志愿者为实验对象,MRI扫描膝关节,获得膝关节冠状位、矢状位和横轴位图像数据。应用Mimics 10.01、Hyperworks 8.0等软件在二维图像数据上提取膝关节各个切片轮廓数据,分别建立骨组织、半月板、关节软骨和韧带的三维模型,在此基础上应用Unigraphics NX 4.0软件的网格划分、材料属性定义、部件连接、接触定义功能建立包括PLC的膝关节三维有限元模型。对模型进行位移测试并用于PLC模拟重建生物力学分析。结果成功制备包括PLC的膝关节三维有限元模型。在134 N前向力作用下,胫骨向前位移为4.83 mm。于膝关节三维有限元模型上进行PLC模拟重建生物力学分析,在10 N.m内翻和外旋力矩作用工况下,模拟重建后膝关节内翻和外旋角度均大于PLC完整时,并且都小于PLC缺失时。结论采用逆向工程学原理可建立包括PLC的膝关节三维有限元模型,且该模型有效,可作为PLC模拟重建生物力学分析的基础模型。     

刮除植骨治疗骨巨细胞瘤的临床研究

目的:通过刮除植骨对骨巨细胞瘤刮除后骨缺损重建的效果分析,了解自体骨或异体骨移植后局部复发率和并发症发生情况。方法:随访手术治疗72例骨巨细胞瘤,男31例,女41例;年龄14～66岁,平均32.4岁。主要发病部位为股骨上端5例,股骨下端21例,胫骨上端17例,肱骨上端7例及桡骨远端9例。外科治疗以X线Cam-panacci分级系统或Enneking外科分期标准为原则,采用囊内刮除植骨(病灶刮除术和肿瘤瘤段切除术),对肿瘤切除,进行临床和放射学随访。结果:72例中有53例获得随访,随访时间8～48个月,平均2年4个月。功能评价按Ennek-ing标准,本组优25例,良21例,一般5例,优良率90.19%。结论:本研究提示骨巨细胞瘤刮除后行骨移植修复骨缺损、重建关节,手术刮除彻底,复发率低,植骨愈合可靠,重建后的关节功能良好,可能与肿瘤充分刮除有关。     

Biomechanical study of pins in cementing of contained proximal tibia defect

Defects from curettage for giant cell tumors of bone frequently have been reconstructed with bone cement with or without reinforcement pins. The biomechanical basis for the addition of reinforcement pins was examined using a model of a contained defect in the proximal tibia. Fifty-four cadaveric proximal tibia in matched pairs were divided into five test groups: intact tibia, medial metaphyseal contained defect, defect reconstructed with cement alone, defect reconstructed with cement and pins inserted within the medullary canal, and defect reconstructed with cement and pins inserted through the cortex. Specimens were tested to failure during one cycle of compressive loading. Defect specimens were significantly weaker and less stiff than intact specimens, establishing the validity of the model-contained defects. For the reconstructions, there was no statistically significant difference in load to failure, stiffness, energy to failure, or displacement for the polymethylmethacrylate treatment alone when compared with matched specimen receiving polymethylmethacrylate and pins treatment. Similarly, there was no statistical difference in biomechanical properties in comparing matched specimens treated with polymethylmethacrylate alone or polymethylmethacrylate/pins (cortex). For contained defects of the proximal tibia that are typical after curettage for giant cell tumor, there appears to be no biomechanical advantage to use of reinforcement pins in the cement.     

Popliteal artery thrombosis from an osteochondroma of the upper end of the tibia. Apropos of a case

A rare case of thrombosis of the popliteal artery due to an exostosis of upper end of tibia is reported. It is rare for exostoses to develop at the upper metaphysial region of the tibia, rare fore vascular complications to develop and particularly rare for these to consist of thromboses. This lesion is a differential diagnosis in young adults with lower limb ischemia. Follow up of these exostoses should be by Doppler, after dynamic arteriography to serve as a reference. Surgical treatment should be adapted to the degree of functional disability and the course of the exostosis or the complications it provokes.     

A Biomechanical Evaluation to Optimize the Configuration of a Hinged External Fixator for the Primary Treatment of Severely Displaced Intraarticular Calcaneus Fractures with Soft Tissue Damage

The purpose of this investigation was to develop an optimized hinged external fixator for the primary treatment of dislocated, intra-articular calcaneus fractures with associated soft tissue damage. To this end, a calcaneus model was made out of a polyurethane block, and a steel cylinder served as the ankle joint and was connected to a synthetic model of the tibia via a metal clamp. A saw cut served as the fracture in the model. A Steinmann nail and Schanz screw were placed in defined positions in the model and connected medially and laterally with longitudinal support rods. The fixator allowed a total of 20 degrees of plantar- and dorsiflexion, with rotation in the virtual axis of the upper ankle joint. Changes in the model fracture were measured during cyclical strain, and at different screw positions in the model tibia and calcaneus. Miniature force sensors located on the longitudinal support rods, and a plantar tension spring, were used to measure pressure and tension. Reproducible values were determined and, with the optimal configuration, shifting within the osteotomy was minimal. In the experimental configuration, optimal tibial screw placement was 70 mm proximal to the rotation axis of the upper ankle joint, and optimal placement of the Steinmann nail was in the posterior surface of the calcaneus. These findings indicated that the hinged fixator allows 20 degrees of ankle movement without alteration of the rotation axis, and suggest that this type of external fixator can be used in all types of calcaneal fracture regardless of the soft tissue damage. ACFAS Level of Clinical Evidence: 5c.     

Technical pitfall while reducing the mismatch between LCP PLT and upper end Tibia in proximal Tibia fractures

Minimal invasive technique along with the widespread use of the new pre contoured locking plates (LCP PLT, LISS PLT) has given rise many alignment related problems in fractures of proximal tibia. A significant implant related problem with the use of pre contoured locking plate in proximal tibia fractures is the hardware irritation of the subcutaneous tissue by upper end of plate. This is caused by the large profile of the implant which sits off the bone at the proximal end. A general recommendation made by some is to try and reduce the bone and plate together with the help of pelvic reduction clamps. We have identified this as a source of error in our practice which has a potential to introduce malalignment in tibia, most often discovered post operatively. Here we will describe with relevant cases, the pitfall in the recommended technique and steps to be taken to avoid this error.     

中切牙全瓷冠不同颈部肩台形态的三维有限元分析

目的：应用三维有限元法分析不同颈缘形态,在承受不同方向力时颈缘瓷体的应力变化,探讨前牙全瓷冠最佳颈缘形态。方法：有限元模型模拟前牙全瓷冠牙体不同颈缘形态设计即直角肩台型和凹面肩台型,模拟口内实际受力情况加载不同方向的力（1OON）观察牙体颈缘部位的Von Misos应力,进行对比分析,以获得前牙全瓷冠最佳的颈缘形态。结果：颈缘直角肩台型设计等效应力比凹面型肩台设计者小。结论：颈缘设计直角肩台型优于凹面型设计。     

Fracture-avulsion of the anterior tibial tuberosity in adolescents

A rare case of a 14-year-old girl with an avulsion-fracture of the tibial tuberosity is reported (type III-A). This lesion is described mainly in boys. The authors explain the classification of the different types of avulsion fracture according to the epiphyseal development of the upper end of the tibia and the stage of maturation at the time of trauma.     

Changes in bone mineral content following tibia shaft fractures

The bone mineral content of the upper ends of the tibia and the fibula was measured in 27 patients with tibia shaft fracture. The bone mineral decreased rapidly after fracture, the loss continuing for about 5 months. Later, towards the end of the first year after the injury, there was a slow restoration of mineral but no return to initial values in most instances. Although the average maximum loss was approximately 45%, only 25% of the initial bone mineral was missing after one year.     

Tips and tricks of limb salvage: Proximal tibia

Due to its anatomical location, the upper end of the tibia poses unique problems while attempting limb salvage and appropriate reconstruction. This article attempts to highlight a few of the key steps, pearls and pitfalls while attempting this challenging procedure.