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1.
Previous finite element studies of the femur have made simplifications to varying extents with regard to the boundary conditions used during analysis. Fixed boundary conditions are generally applied to the distal femur when examining the proximal behaviour at the hip joint, while the same can be said for the proximal femur when examining the distal behaviour at the knee joint. While fixed boundary condition analyses have been validated against in vitro experiments it remains a matter of debate as to whether the numerical and experimental models are indicative of the in vivo situation. This study presents a finite element model in which the femur is treated as a complete musculo-skeletal construct, spanning between the hip and knee joints. Linear and non-linear implementations of a free boundary condition modelling approach are applied to the bone through the explicit inclusion of muscles and ligaments spanning both the hip joint and the knee joint. A non-linear force regulated, muscle strain based activation strategy was found to result in lower observed principal strains in the cortex of the femur, compared to a linear activation strategy. The non-linear implementation of the model in particular, was found to produce hip and knee joint reaction forces consistent with in vivo data from instrumented implants.  相似文献   

2.
The long term success of total joint replacement can be limited by fatigue failure of the acrylic cement and the resulting disruption of the bone-cement interface. The incidence of such problems may be diminished by reduction of the fatigue notch factor in the cement, so that stress concentrations are avoided and the fatigue crack initiation time maximized. This study describes a method for numerical shape optimization whereby the finite element method is used to determine an optimal shape for the femoral stem of a hip prosthesis in order to minimize the fatigue notch factor in the cement layer and at interfaces with the bone and stem.

A two-dimensional model of the proximal end of a femur fitted with a total hip prosthesis was used which was equivalent to a simplified three-dimensional axisymmetric model. Software was developed to calculate the fatigue notch factor in the cement along the cement/stem and cement/bone interfaces and in the proximal bone. The fatigue notch factor in the cement at the cement/stem interface was then minimized using the ANSYS finite element program while constraining the fatigue notch factor at the cement/bone interface at or below its initial level and maintaining levels of stress in the proximal bone to prevent stress shielding. The results were compared with those from other optimization studies.  相似文献   


3.
我们用有限元模型结合Hofftnan失效准则参数化地研究了载荷条件对股骨承载能力的影响。载荷条件包括摔跤姿态角,载荷施加位置及髋关节间的摩擦阻力。参数化研究结果表明:载荷施加位置是影响股骨承载能力的关键因素;当外载荷作用在股骨头部时,有两个股骨承载能力的低谷区,如果外载施加在这两个区域,则股骨颈极易发生骨折;髋关节间的摩擦阻力可严重地影响股骨承载能力,这对骨关节炎患者有很大的内在意义。  相似文献   

4.
Objective: The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods :A biosystem model of the man femoral hip joint by using the GE ( General Electric) lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results:The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion:Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ,which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical resuits.  相似文献   

5.
Ni GX  Choy YS  Lu WW  Ngan AH  Chiu KY  Li ZY  Tang B  Luk KD 《Biomaterials》2006,27(9):1963-1970
Many bioactive bone cements were developed for total hip replacement and found to bond with bone directly. However, the mechanical properties at the bone/bone cement interface under load bearing are not fully understood. In this study, a bioactive bone cement, which consists of strontium-containing hydroxyapatite (Sr-HA) powder and bisphenol-alpha-glycidyl dimethacrylate (Bis-GMA)-based resin, was evaluated in rabbit hip replacement for 6 months, and the mechanical properties of interfaces of cancellous bone/Sr-HA cement and cortical bone/Sr-HA cement were investigated by nanoindentation. The results showed that Young's modulus (17.6+/-4.2 GPa) and hardness (987.6+/-329.2 MPa) at interface between cancellous bone and Sr-HA cement were significantly higher than those at the cancellous bone (12.7+/-1.7 GPa; 632.7+/-108.4 MPa) and Sr-HA cement (5.2+/-0.5 GPa; 265.5+/-39.2 MPa); whereas Young's modulus (6.3+/-2.8 GPa) and hardness (417.4+/-164.5 MPa) at interface between cortical bone and Sr-HA cement were significantly lower than those at cortical bone (12.9+/-2.2 GPa; 887.9+/-162.0 MPa), but significantly higher than Sr-HA cement (3.6+/-0.3 GPa; 239.1+/-30.4 MPa). The results of the mechanical properties of the interfaces were supported by the histological observation and chemical composition. Osseointegration of Sr-HA cement with cancellous bone was observed. An apatite layer with high content of calcium and phosphorus was found between cancellous bone and Sr-HA cement. However, no such apatite layer was observed at the interface between cortical bone and Sr-HA cement. And the contents of calcium and phosphorus of the interface were lower than those of cortical bone. The mechanical properties indicated that these two interfaces were diffused interfaces, and cancellous bone or cortical bone was grown into Sr-HA cement 6 months after the implantation.  相似文献   

6.
目的:研究人工髋关节置换前后股骨及假体的应力分布以及假体设计参数对应力的影响。方法:建立股骨和假体有限元模型,分析在步行峰值关节载荷和主要肌肉载荷作用下,完整股骨和置换后股骨及假体的应力水平。结果:完整股骨中上部内侧受压应力,外侧受张应力,中下部外侧受压应力,内侧受张应力,股骨应力峰值位于中下部;置换后股骨受力总体模式不变,近端应力遮挡显著。随颈干角增加,假体及股骨应力水平降低;柄长对假体应力影响不大,股骨上的应力随柄长增大略有增加。结论:假体设计时可适当增大颈干角,在骨组织条件允许的情况下可适当增加假体柄长,以减轻术后的应力遮挡效应。  相似文献   

7.
Information regarding the stresses and strains in the canine femur during various activities is important for veterinary orthopaedic surgeons, engineers designing implants for dogs, and researchers of human orthopaedics who use dogs as models. Nevertheless, such information is currently unavailable. The objective of this study is to determine the stress and strain distribution in the canine femur during mid-stance, for two loading scenarios. Three-dimensional finite element models of the canine femur were created. Two loading cases were considered: the hip joint reaction force alone, and the hip joint reaction force with all muscle forces acting on the femur. Force directions and magnitudes were obtained from the literature. Analyses were performed with NASTRAN for Windows software. When all muscle forces were considered, stresses and strains were significantly reduced, peak compressive stresses were found to occur in the medial diaphysis, and peak tensile stresses occurred in the lateral diaphysis. While the canine femur seems to be loaded primarily in bending when only the hip joint reaction force is considered, the bending moment is significantly decreased when all muscle forces are considered as well. Further in vivo and in vitro experiments are needed to validate the results of the calculations described in this paper. It is expected that future studies will be carried out, in which the stress and strain distributions in femora with different types of implants and stems will be compared to those in the normal femur.  相似文献   

8.
我们用有限元模型结合Hoffman失效准则参数化地研究了载荷条件对股骨承载能力的影响。载荷条件包括摔跤姿态角,载荷施加位置及髋关节间的摩擦阻力。参数化研究结果表明载荷施加位置是影响股骨承载能力的关键因素;当外载荷作用在股骨头部时,有两个股骨承载能力的低谷区,如果外载施加在这两个区域,则股骨颈极易发生骨折;髋关节间的摩擦阻力可严重地影响股骨承载能力,这对骨关节炎患者有很大的内在意义。  相似文献   

9.
A finite element analysis of the stresses in a three-dimensional model of the proximal human tibia containing the tibial components (insert, tray, and stem) of a cemented total knee joint replacement was conducted. 12 cases of this model, covering three variables (composition of applied loading, interface conditions, and assignment of elastic properties to the cortical and cancellous bones) were analyzed. It was found that the stresses in various parts of the model were markedly lower when (a) the applied load comprised a compressive joint reaction force (F), of 2 kN, only (quadriceps inactive) versus F+ a patellar ligament force of 1.46 kN (P), representing the situation when the quadriceps are active; and (b) the interfaces were considered fully bonded compared to when they represented as having surface-to-surface Coulomb frictional contact (coefficient of friction = 0.2). However, the nature of the elastic properties that were assigned to the bones (isotropic versus anisotropic) had only a marginal influence on the stresses.  相似文献   

10.
Abstract

A three-dimensional hip model was created from the MRI scans of one human subject based on constructing the entire pelvis and femur. The ball and socket joint was modelled between the hip’s acetabulum and the femoral head to analyse the multiaxial loads applied in the hip joint. The three key ligaments that reinforce the external surface of the hip to help to stabilise the joint were also modelled which are the iliofemoral, the pubofemoral and ischiofemoral ligaments. Each of these ligaments wraps around the joint connection to form a seal over the synovial membrane, a line of attachment around the head of the femur. This model was tested for different loading and boundary conditions to analyse their sensitivities on the cortical and cancellous tissues of the human hip bones. The outcomes of a one-legged stance finite element analysis revealed that the maximum of 0.056?mm displacement occurred. The stress distribution varied across the model which the majority occurring in the cortical femur and dissipating through the cartilage. The maximum stress value occurring in the joint was 110.1?MPa, which appeared at the free end of the proximal femur. This developed finite element model was validated against the literature data to be used as an asset for further research in investigating new methods of total hip arthroplasty, to minimise the recurrence of dislocations and discomfort in the hip joint, as well as increasing the range of movement available to a patient after surgery.  相似文献   

11.
Intense interest in knee joint mechanics has resulted in the development of numerous models to predict forces acting at the knee. However, few models have accounted for the unique geometric characteristics of the knee joint's articular surfaces when predicting the mechanical response of the joint. The purpose of this study was to simulate accurately the complex geometric characteristics of the tibiofemoral joint for input into a finite element model representing the knee joint of athletic females. The right knee of an athletic female with no history of knee joint trauma was imaged using a 0.5 T magnetic resonance imaging (MRI) unit. Twelve cross-sectional slices of the knee were scanned in each of three orthogonal planes (coronal, sagittal and axial) at slice intervals of 6 mm, 7 m, and 8 mm respectively. A scan plan (two coronal images and an axial image) was also generated to enable calculation of the orthogonal scans with respect to one another. Select anatomical reference points representing cancellous and compact bone, major ligament attachment areas, and articular cartilage of the distal femur and proximal tibia were digitized from the processed shadowgraphs. The processed digitized data were input into a computer graphics program which was the pre- and post-processing software for the finite element analysis package. Contours of the cancellous and compact bone of the tibial and femoral condyles were generated using beta and cubic spline curves. Bezier quadratic and cubic polynomials were used to reconstruct the tibial and femoral shafts. Accuracy of the model was verified by comparing the shape and proportionality of the simulated tibia and femur with the MRI images from which the model was generated and with anatomical literature. Comparisons demonstrated that subtle variations in the complex geometry of the tibiofemoral joint could be accurately simulated using data obtained from MRI scans of an intact knee. Refinements of the imaging and digitizing procedures were proposed to provide even greater accuracy in modelling the anatomy of the tibiofemoral joint.  相似文献   

12.
髋部骨折是老年人主要的致伤和致死原因之一,随着我国人口的老龄化进展,其发生率也逐渐增加,给家庭和社会带来沉重的经济负担。髋部骨折的主要治疗方法包括骨折内固定术和髋关节置换术。综述股骨近端解剖结构特点与载荷传递机制的关系、股骨近端皮质骨和松质骨的力学分布以及国内外对于髋部骨折风险预测的生物力学研究方法的最新进展,从生物力学角度理解髋部骨折,提高老年人髋部骨折风险预测的准确性,促进股骨近端骨折治疗方法和内植物的正确选择和应用。  相似文献   

13.
Osteoporotic hip fracture is associated with high mortality and morbidity and often results in a loss of mobility and independence. Osteoporosis is diagnosed by measuring Bone Mineral Density (BMD), a measure of the amount of mineral in a bone. Although BMD continues to serve well it does not fully account for bone strength and only partially accounts for the risk of hip fracture. The shape and structure of the proximal femur also help to determine how forces act in the hip in a fall and their measurement can aid the prediction of hip fracture.This review examines the link between simple geometrical measures of the proximal femur and hip fracture, or bone strength. It will explore how they relate to each other and to anthropometric factors such as sex, height, weight and age. Limitations in these measures will be identified and new methods of analysis reviewed that encompass many different aspects of the shape of the femur. These new methods show great promise for improving the prediction of fracture risk in the future.  相似文献   

14.
An anatomical hip model has been developed to simulate the impact load on the hip of a falling person wearing a hip protector. The hip consists of an artificial pelvis made of aluminium, linked by a ball-and-socket joint to an anatomically shaped steel femur (thigh bone). The femur is embedded in silicone material with a hip-shaped surface to allow realistic positioning of the protectors with accessory underwear. Additionally, the silicone simulates the damping and load-dispersal effect of soft tissue. A triaxial load sensor is integrated in the neck of the femur to measure the axial and cross-sectional force components in response to external impact forces on the hip. The performance of the hip model was investigated in drop tests and validated against biomechanical data. In a first series of measurements, the shock absorption of 10 different hip protectors, including both energy-absorbing and energy-shunting systems, was analysed. To determine the importance of hip protector placement, each protector was tested in the correct anatomical alignment over the hip and anteriorly displaced by 3 cm. Considerable differences were found between individual hip protectors in their effectiveness to reduce impact forces on the femur. Position of the hip protector also influenced the forces applied to the femur.  相似文献   

15.
16.
A composite material implant prosthesis for hip replacement has been developed. The design of the prosthesis substructure was based on investigation of the stress and strain fields that were developed in the human femur at the proximal end when a prosthesis stem had been inserted into it. The prosthesis stem structure was of unidirectional fibrous composite material core (graphite fibres in polysulfone matrix), wrapped with four layers of the same material but orientated at different angles. The orthotropic moduli of the outer layer are very close to the moduli of a human cortical bone in the vertical and circumferential directions. The moduli increased gradually from the outer layer to the inner core. A three-dimensional finite element model of the prosthesis and the bone has been constructed and loaded with the range of forces that might appear upon operation. The behaviour of the composite prosthesis and the femur was then compared with the intact femur and three other types of prosthesis materials, namely stainless steel, titanium, an isoelastic material and a hypothetical one with moduli identical to the cortical bone. The titanium has modulus of elasticity that is only half of the stainless steel. It was found that the composite prosthesis gave the best performance for most of the categories that were examined.  相似文献   

17.
A universal static hip joint simulation apparatus was designed to simulate both 3-D joint and 3-D muscle forces for each of the three load-bearing phases of normal gait. The adjustability provided by the apparatus allowed for the consideration of femoral orientation, hip joint contact force, and primary active muscle loads for each simulated activity. Use of this apparatus enables the biomechanical response of the femur to be more fully and accurately determined under a full range of everyday activities. Results demonstrate that the proximal femur experiences significantly higher levels of strain during the activities of toe off and heel strike than during midstance. This evaluation underscores the importance of considering each phase of gait when investigating the biomechanical response of the femur, which should be especially relevant in the design and evaluation of femoral components for hip joint arthroplasty. Future studies are planned for femoral strain evaluation following simulated hip joint replacement. By providing a more complete strain profile evaluation of the femur as a function of implant design, the use of this apparatus should contribute to the development of new femoral component designs for improved patient care.  相似文献   

18.
基于CT断层图像重建股骨头缺血性坏死髋关节的三维结构   总被引:1,自引:0,他引:1  
目的探索通过虚拟现实技术寻求快速准确重建股骨头缺血性坏死髋关节三维结构的方法。方法基于髋关节的64排螺旋CT连续断层二维图像,M im ics软件分别重建髋臼、近端股骨、股骨颈及股骨头病变组织的三维可视化结构。结果 M im ics医学图像处理软件对髋关节CT扫描的D icom格式数据进行三维重建图像结构清晰,可真实再现髋臼和股骨近端的结构,并且能够对病变组织部位予以定位,对病变组织体积进行计算。结论 M im ics软件根据CT扫描所得的D icom原始数据能准确重建股骨头缺血性坏死髋关节的三维立体结构,为股骨头缺血性坏死髋关节骨质的评估及治疗方案的选择提供了客观的依据。  相似文献   

19.
Finite element (FE) analysis has been widely used to study the behaviour of bone or implants in many clinical applications. One of the main factors in analyses is the realistic behaviour of the bone model, because the behaviour of the bone is strongly dependent on a realistic bone material property assignment. The objective of this study was to compare isotropic and orthotropic inhomogeneous material models used for FE analyses of the "global" proximal femur and "small" specimens of the bone (cancellous and cortical). Our hypothesis was that realistic material property assignment (orthotropy) is very important for the FE analyses of small bone specimens, whereas in global FE analyses of the proximal femur, this assignment can be omitted, if the inhomogeneous material model was used. The three-dimensional geometry of the "global" proximal femur was reconstructed using CT scans of a cadaveric femur. This model was implemented into an FE simulation tool and various bone material properties, dependant on bone density, were assigned to each element in the models. The "small" specimens of cortical and cancellous bone were created in the same way as the model of the proximal femur. The results obtained from FE analyses support our above described hypothesis.  相似文献   

20.
目的 探讨 3 种不同建模方式对髋关节有限元模型生物力学特性的影响,研究出更符合实际的髋关节的材料属性赋值方法。 方法 对髋关节模型进行三维重建,分别采用皮-松质骨赋值法、均一赋值法和灰度赋值法完成材料参数赋值,设定相同的边界条件和载荷,模拟单腿站立位状态下髋关节受力情况,对比 3 组模型的髋关节应力和形变情况。 结果 3 种不同建模方式下髋关节应力均集中于股骨颈内侧,皮-松质骨赋值法、均一赋值法、灰度值赋值法模型 von Mises 应力峰值分别为 11. 04、3. 91、4. 25 MPa。 皮-松质骨赋值法模型最大形变位于股骨大粗隆上部,髋臼与股骨头处最大形变值为 0. 27 mm。 均一赋值法模型及灰度值赋值法模型最大形变位于髋臼与股骨头处,最大形变值分别为 0. 11、0. 12 mm。 结论 根据髋关节 CT 数据灰度值进行梯度赋值,使得髋关节模型材料属性分布更接近骨骼真实的材料属性。  相似文献   

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