正常髋部与佩戴保护支具髋部的有限元对比分析(英文)

背景:有限元法因其具有不受样本量限制,实验误差小,重复性好等优点而成为防滑倒生物力学研究的重要手段。目的:建立正常骨盆以及佩戴护具骨盆的三维有限元模型,分析滑倒过程中骨盆各部位的应力、应变和位移分布,验证护具的有效性。方法:以中国数字人原始资料应用Abaqus 6.51软件构建正常骨盆以及佩戴护具骨盆的三维有限元模型,固定约束地面刚体,对整个骨盆模型加载2 m/s的速度载荷,程序运算后观测骨盆模型佩戴护具前后的应力、应变及位移随时间的变化规律和分布云图。结果与结论:与未佩戴护具比较,佩戴护具时滑倒过程中骨盆与地面的接触力、骨盆与地面产生最大接触力时松质骨最大压缩应变、大转子以及股骨颈周围应变最大值、大转子和股骨颈附近的最大von-Mises应力值、大转子和股骨颈处的平均应力值等均明显减小。提示髋部保护支具对大转子具有保护作用,能有效降低人体滑倒时转子间骨折的发生率。     

骨盆及髋臼三维有限元模型单元选择及构建生物力学意义

目的：寻求骨盆及髋臼三维有限元模型构建中三维有限元模型单元的选择以及构建，为骨盆、髋臼生物力学研究及手术仿真模拟提供精确模型。方法：在获得的骨盆及髋臼三维CT图像数据矩阵中移动立方体，骨骼内部采用六面体单元，骨骼表面采用Marching Cube算法，建立四面体代替等值面，构建骨盆及髋臼三维有限元模型单元。结果：综合Marching Cube算法和传统方法构建三维有限元模型，所构建模型表面光滑连续，不仅能够分析骨骼表面应力应变分布，同时保留内部应力应变分布的特点。结论：结合传统三维有限元模型构建方法，在模型表面使用四面体单元，模型内部采用六面体单元，构建表面连续平滑的骨盆和髋臼有限元模型，不仅能够反应内部应力应变分布，而且能够模拟分析骨骼表面应力应变分布。     

垂直载荷作用下骨盆的三维有限元分析

背景：目前对骨盆的力学分析还处于极其粗糙阶段，而有限元法因其具有不受样本量限制，实验误差小，重复性好等优点，正日益成为骨盆生物力学研究的重要手段。 目的：建立正常骨盆的三维有限元模型，分析骨盆在垂直载荷作用下的应力／应变和位移分布。 设计、时间及地点：三维有限元分析，单一样本观察。于200703／09在南方医科大学生物力学实验室完成。 材料：健康成年男性志愿者1例进行PET—CT扫描，层厚1FfLrn，得N-维原始图像以DICOM格式输出。 方法：应用Mimics、Freeform、ANSYS等软件进行三维重建，并建立正常骨盆的有限元模型。模拟人体双腿直立位的生理姿势，对模型施加500N轴向载荷。具体方式为约束双侧靛臼，向骶骨椎体上表面垂直加压，压力均匀分布于各个结点。 主要观察指标：计算该加载方式下骨盆的应力、应变及位移的分布情况。 结果：垂直加载500N载荷于骶骨上表面时，应力经两侧骶骨翼、骶髂关节，斜向下方经过坐骨大切迹附近，髂骨中央弓状线，传导至两侧髋臼。骨盆前环即耻骨支和耻骨联合受力较小。应变集中在两侧骶髂关节，绝对值很小，前方的耻骨联合处应变极小，呵忽略不计。位移以骶骨背侧的骶正中嵴处最大。 结论：正常骨盆是一个非常稳定的力学结构。过大的垂直应力容易引起骶骨或骶髂关节受损导致骨盆的垂直稳定性下降；恢复骶骨至髋臼的连续性对应力传导非常重要。     

骨盆及髋臼三维有限元模型单元选择及构建生物力学意义

目的:寻求骨盆及髋臼三维有限元模型构建中三维有限元模型单元的选择以及构建,为骨盆、髋臼生物力学研究及手术仿真模拟提供精确模型。方法:在获得的骨盆及髋臼三维CT图像数据矩阵中移动立方体,骨骼内部采用六面体单元,骨骼表面采用MarchingCube算法,建立四面体代替等值面,构建骨盆及髋臼三维有限元模型单元。结果:综合MarchingCube算法和传统方法构建三维有限元模型,所构建模型表面光滑连续,不仅能够分析骨骼表面应力应变分布,同时保留内部应力应变分布的特点。结论:结合传统三维有限元模型构建方法,在模型表面使用四面体单元,模型内部采用六面体单元,构建表面连续平滑的骨盆和髋臼有限元模型,不仅能够反应内部应力应变分布,而且能够模拟分析骨骼表面应力应变分布。     

坐位骨盆的三维有限元分析

背景：由于骨盆具有复杂的结构,目前对于坐位骨盆的生物力学研究较少,有限元法日益成为骨盆生物力学研究的重要手段。目的：以有限元法研究成人正常静态坐位骨盆应力分布。方法：获取正常成年女性全骨盆CT扫描图像,利用CT数据通过Mimics10.0对图像数据进行重建,利用Geomagic,Proe5.0进行实体建模,输入ANSYS。再根据解剖部位建立骨盆主要韧带。对S1椎体上终板施加600N静载荷模拟坐位时骨盆受力环境,计算该加载方式下骨盆的应力、应变及位移的分布情况。结果与结论：垂直加载600N载荷于骶骨上表面时重力由骶骨经骶髂关节向下传递,到达坐骨结节。此时的坐骨结节处承受较大压应力。有限元模型在静载荷下的特征部位应力、应变值基本能够反应骨盆特有的力学结构特性,模型的准确性较高。计算结果与文献中报道的结果相近,建立的人体全骨盆三维有限元模型较客观地反映人体骨盆的解剖结构和力学特性,可作为骨盆生物力学研究的工具及满足临床研究的需要。     

前路钢板置入固定治疗骶髂关节脱位的三维有限元分析

背景：已有文献报道骶髂关节损伤及固定的生物力学研究,但多是在尸体标本或人工骨模型上模拟骶髂关节损伤。目的：利用三维有限元方法对骶髂关节脱位前路钢板内固定的垂直稳定性进行分析。方法：在完整骨盆三维有限元模型的基础上,建立一侧骶髂关节脱位后前路钢板内固定模型。对模型施加500N轴向载荷,经计算得到应力、应变及位移云图,并与完整骨盆的同一工况进行比较分析。结果与结论：在内固定系统处出现了应力集中现象,尤其以靠近骶髂关节的螺钉周围应力最大,远远大于完整骨盆同一工况下的最大应力。应变以健侧骶髂关节最大,内固定侧骶髂关节无应变。位移以损伤侧骶髂关节处最大,约为完整骨盆的2倍。提示前路钢板内固定治疗骶髂关节脱位,骨盆在垂直方向上稳定性较差,且钢板螺钉处出现了应力集中现象。     

有限元方法分析不同截骨平面对组配式半骨盆假体固定效果的影响

建立正常左侧半骨盆三维有限元模型,模拟4个典型的截骨平面.根据不同的截骨位置利用Solidworks 2006软件进行相应尺寸的半骨盆假体绘制.组装后分别模拟4个截骨平面假体重建三维有限元模型.计算4个截骨水平下半骨盆假体系统在单腿负重期应力峰值、最大位移、应力集中部位的应力值,以及4枚横向固定螺钉的应力峰值.4个截骨位置在髋臼上方缺损长度分别为20～56 cm不等,随截骨位置升高,截骨平面与水平成角增加,内固定系统的稳定性逐渐下降,最大位移增加,系统最大应力值逐渐增高.并且在水平截骨及与水平成角截骨情况下4枚横行固定螺钉应力分布特点不同.结果提示,随髋臼上方骨缺损范围增加,截骨位置与水平面成角逐渐加大,假体系统固定效果下降.对于截骨平面与水平面平行的骨缺损半骨盆假体可以获得较好的稳定性.     

坐位骨盆的三维有限元分析

背景:由于骨盆具有复杂的结构,目前对于坐位骨盆的生物力学研究较少,有限元法日益成为骨盆生物力学研究的重要手段.目的:以有限元法研究成人正常静态坐位骨盆应力分布.方法:获取正常成年女性全骨盆CT扫描图像,利用CT数据通过Mimics 10.0对图像数据进行重建,利用Geomagic,Proe5.0进行实体建模,输入ANSYS.再根据解剖部位建立骨盆主要韧带.对S1椎体上终板施加600 N静载荷模拟坐位时骨盆受力环境,计算该加载方式下骨盆的应力、应变及位移的分布情况.结果与结论:垂直加载600 N载荷于骶骨上表面时重力由骶骨经骶髂关节向下传递,到达坐骨结节.此时的坐骨结节处承受较大压应力.有限元模型在静载荷下的特征部位应力、应变值基本能够反应骨盆特有的力学结构特性,模型的准确性较高.计算结果与文献中报道的结果相近,建立的人体全骨盆三维有限元模型较客观地反映人体骨盆的解剖结构和力学特性,可作为骨盆生物力学研究的工具及满足临床研究的需要.     

腕保护器抗冲击载荷的有限元分析

背景：人体防滑倒腕部保护支具对手腕部有明显的保护作用。目的：采用有限元分析验证腕保护器防护腕部骨折的有效性。方法：以中国力学可视人原始资料为依据,应用Abaqus6.51软件构建带软组织的正常手腕和佩带腕保护器手腕的三维有限元模型,对整个手腕模型加载2m/s的速度载荷,经程序运算后对比手腕部三维有限元模型佩带腕保护器前后的应力应变分布云图及腕部尺骨远端掌面最大应力值随时间变化规律图。结果与结论：与未佩带腕保护器比较,佩带腕保护器后在跌倒过程中小鱼际和腕关节背面的软组织等效应力、腕部桡尺骨下段的等效应力均明显变小,力学结构最薄弱的桡尺骨远端应力变小尤为最明显,而第2～4掌骨、食指近节、钩骨等力学结构相对坚强的短管状骨和不规则骨所受应力明显增大,提示腕保护器可分散、吸收一部分桡尺骨远端应力,转移至腕、掌、指骨上一部分,对保护腕关节尤其是防止桡尺骨远端骨折有积极的作用。     

骶髂关节脱位钉板内固定与关节拉力螺钉内固定两种置入方法的三维有限元分析

背景:有限元法能对复杂的结构、形态、载荷和材料力学性能进行应力分析比较,模拟的条件更接近正常,结果更加可信,已经是骨科生物力学研究中的重要手段.目的:以有限元分析方法建立骨盆骶髂关节(单侧)脱位模型,比较前路钉板内固定及骶髂关节拉力内固定治疗后的生物力学稳定性.方法:在正常骨盆三维有限元模型的基础上,截断骶髂关节问的骶髂前后韧带(包含骶髂骨间韧带)以及骶结节韧带和骶棘韧带等盆底韧带,造成骶髂关节脱位.分别在前路钉板内固定系统(共2块重建钢板6枚螺钉)及骶髂关节拉力螺钉内固定(2枚拉力螺钉)两种固定方法的模型上,加载后进行非线性有限元分析.计算该加载方式下的骨盆应力、应变及位移的分布情况.结果与结论:建立了高精度骨盆骶髂关节脱位两种内固定的三维有限元模型.通过应力应变云图分析与比较后发现,采用骶髂关节拉力螺钉内固定相对于前路钢板内固定移位的总位移小,应力分布均匀,无明显高度集中现象,固定强度更大,固定后的骨盆更稳定.利用有限元方法分析骨盆骶髂关节脱位两种内固定生物力学稳定性,具有较高真实性、精确度和可重复性,结果与其他生物力学实验结果相一致,能满足临床骨盆损伤研究的需要.     

数字化摄影及图像后处理技术在骨密度测定中的应用

背景：随着直接数字化X射线摄影系统的出现,应用计算机相关知识增加了一些以前普通X射线摄影机不具备的一些后处理程序,为临床骨密度的测定提供了新方法。目的：通过直接数字化X射线摄影系统机拍摄标准骨盆平片,利用其强大后处理功能,通过测量股骨颈、ward三角及股骨大转子的象素密度,找出简单易行测定骨密度的新方法。方法：随机选择105份标准骨盆直接数字化X射线平片,按年龄以60岁为标准,分为实验组（≤60岁）和对照组（〉60岁）。根据标准骨盆平片制定测量股骨颈密度的三点、ward三角一点及股骨大结节三点。对两组女性患者的股骨颈、股骨大转子及股骨颈ward三角象素密度均数分别进行t检验,观察两个年龄段股骨颈、股骨大转子及股骨颈ward三角密度值分布情况。结果与结论：对照组股骨颈象素密度为945.59±174.70,大转子象素密度为712.67±196.89,ward三角象素密度为873.70±195.17;实验组股骨颈象素密度为779.03±125.79,大转子象素密度为526.22±127.93,ward三角象素密度为668.30±131.19。两组间比较差异有显著性意义（P〈0.05）。提示,通过测量直接数字化X射线摄影系统骨盆平片上骨质的象素密度可以作为骨密度测定方法之一,且操作简便,易于临床掌握和运用,不需患者行二次医疗检查。     

Effect of transtrochanteric rotational osteotomy on impingement and contact state of a femoral implant in conversion total hip arthroplasty — Retrospective simulation study

BackgroundThe transtrochanteric rotational osteotomy is a common osteotomy for osteonecrosis of the femoral head, although the results of conversion total hip arthroplasty after the osteotomy are controversial. We evaluated how deformities in the proximal femur after the osteotomy affect hip impingement and the contact state of the stem in total hip arthroplasty.MethodsWe retrospectively reviewed 35 hips (24 men) that had undergone the transtrochanteric rotational osteotomy for osteonecrosis of the femoral head (TRO-group) and compared them with 31 contralateral, unoperated hips (Primary group). The distance between the anterior and posterior greater trochanter at the cutting point of the femur, defined as the greater trochanter width and the contact area of the femoral implant surface with cortical bone were measured by CT-based three-dimensional templating software. We also calculated the hip range of motion in conversion total hip arthroplasty and analyzed the correlations between the greater trochanter width and the range of motion.FindingsThe number of bony-impingement cases was significantly greater, and the range of motion in flexion, internal rotation and external rotation was significantly less in TRO-group. There was a significant negative correlation between the greater trochanter width and range of motion of internal rotation. There were no significant differences between two groups in percentages of femoral-implant contact area.InterpretationsThe femoral implant fixation appears to be satisfactorily fixed in all zones in conversion total hip arthroplasty. However, the greater attention should be paid to minimizing bony impingement, especially on the anterior side, in conversion total hip arthroplasty.     

Apophyseal fracture of the greater trochanter

Apophyseal fractures about the pelvis and proximal femur are well-described; however, these injuries rarely involve the greater trochanter. We report the case of a 15-year-old boy of large build who appeared to have all signs and symptoms of a left slipped capital femoral epiphysis. No specific inciting event had occurred before the hip pain. Radiographs and bone scan of the capital femoral epiphysis appeared normal, and follow-up radiographs confirmed an apophyseal fracture of the greater trochanter. This case represented a rare occurrence, and its interesting manifestation was similar to that of a slipped capital femoral epiphysis.     

Paralysie complète du quadriceps secondaire à un hématome post-traumatique du muscle iliopsoas de diagnostic tardif : à propos d’un cas

Paralysis of the femoral nerve secondary to compression from a hematoma of the iliopsoas muscle in the lesser pelvis is a well-known complication of anticoagulants and certain surgical procedures, but is a rare post-traumatic event. A 16-year-old teenage boy presented with a painful, swollen knee with an active extension deficit of the leg following a fall. Seven weeks before he had also received a blunt trauma to the greater trochanter of the homolateral hip. The diagnosis of a patellar tendon tear was first suggested, but this was eliminated on MRI. A close clinical evaluation showed complete paralysis of the quadriceps with a sensory deficit of the anterior side of the thigh. MRI of the lesser pelvis showed a massive iliopsoas hematoma compressing the femoral nerve. Surgical evacuation was performed 9 weeks after the original trauma. At 6 months of follow-up, recovery of the muscle was complete and the electromyogram was normal.     

股骨颈保留型人工全髋关节置换后的应力分析

背景：股骨颈保留型（Col um Femoris Preserving,C.F.P）假体为意大利骨科医生Pipino与德国LINK公司联合设计开发。该假体手术操作手册中推荐截骨平面是否适合国人股骨结构特点以及所采用截骨方式是否会引起假体以及股骨应力发生变化,目前尚未见研究报告。目的：通过临床病例回顾和三维有限元模型分析股骨颈保留型人工全髋关节置换的临床疗效以及应力分布变化。方法：①回顾分析36例股骨颈保留型全髋关节置换及36例普通生物型全髋关节置换患者临床资料,通过Harris评分、目测类比评分、置换前后偏心距变化、IDES-Engh放射学及并发症等指标评价疗效。②建立两种不同截骨平面股骨颈保留型全髋关节置换有限元分析模型,分析股骨转子间窝上1.5 cm及头颈交界处为截骨平面带来的偏心距差异、股骨以及假体应力分布变化。结果与结论：①头颈交界处为截骨平面的股骨颈保留型全髋关节置换,短期随访临床疗效优良,与普通生物型无明显差别。②有限元分析显示：头颈交界为截骨平面与转子间窝上1.5 cm为截骨平面比较,偏心距增大,假体及股骨所受应力增大,但应力分布相同。     

Formation of impacted fractures of the femoral neck: an experimental study

Nine femoral-neck specimens were exposed to a fracturing force applied to the femoral head, perpendicular to the axis of the femur, simulating a fall onto the greater trochanter. The mechanical strength and fracture type were investigated in a universal testing machine. In all nine specimens, the superior (cranial) cortex of the femoral neck fractured first, followed by some compression and fracture of the inferior cortex, whereby impacted fractures had been formed. After application of additional force, dislocated fractures occurred. This method may be of value in experimental studies of impacted fractures of the femoral neck. RELEVANCE: This study describes an experimental procedure for formation of impacted femoral neck fractures. Hopefully this technique may be employed in further examining the nature and biomechanics of impacted hip fractures. The ultimate aim would seem to be a classification with regard to which fractures require surgery and which may be treated conservatively.     

Should extramedullary fixations for hip fractures be removed after bone union?

Background

Osteosynthesis implants, which remain in the patient after fracture union to save additional surgery, may affect the strain distribution within the bone. A reduction of strain within the bone is known to result in localized bone loss (“stress shielding”) and increased fracture risk. The purpose of this study was to examine whether extramedullary fixations for femoral neck fractures have to be removed after fracture union to prevent reductions in cortex strains.

Methods

In a biomechanical experiment, six pairs of human cadaver femora (mean age 56 years, range 48 to 64) were supplied with five strain gauges per bone. The bones were equally supplied with a compression hip screw or a femoral neck plate. Before surgery, after surgery and after removal of the implants, axial compression tests were conducted to measure surface strains during loading.

Findings

The compression hip screw reduced the amount of strain at the superior neck by 88% (P = 0.015) and at the lesser trochanter by 51% (P = 0.038). The femoral neck plate reduced the amount of strain at the superior neck by 89% (P = 0.001), and increased the amount of strain at the inferior neck by 58% (P = 0.02) and at the lesser trochanter by 63% (P = 0.005). After implant removal, there was no significant difference in strain compared to pre-fracture levels, except for the compression hip screw with 21% less strain (P = 0.047) at the superior neck.

Interpretation

Removal of osteosynthesis implants after bone union reverts bone strains to pre-fracture levels, and might prevent further bone loss induced by stress shielding.