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1.
膝关节矢状面机构模型   总被引:1,自引:0,他引:1  
建立矢状面上膝关节二维机构模型,求解矢状面髌股关节求解屈膝过程中髌骨与股骨的接触点移动,髌骨倾角、髌韧带倾角变化,髌股关节功能角变化以及髌股接触力和髌韧带作用力的变化等髌股关节运动及动力学参数.依据膝关节主要组成部分的功能及相互间连接关系,以股胫关节交叉四连杆模型为基础,通过对髌股关节的几何描述及力平衡限定,并运用ADAMS软件进行分析计算,计算结果与文献实验结果吻合良好。  相似文献   

2.
本文基于人膝关节正中矢状面的解剖特征和侧位膝关节X线像,借助于数字仪,并应用最小二乘曲线拟合的方法,建立了人膝关节股骨-胫骨和股骨-髂骨在矢状面内各自的啮合曲面方程。  相似文献   

3.
目的通过踝关节三维有限元模型,研究静止站立位后踝骨折后胫距关节面的应力变化及位移趋势,为后踝骨折的治疗提供理论依据。方法以一套正常人体站立位踝关节CT图像为原始数据,应用有限元建模技术,建立带有关节软骨的踝关节三维有限元模型,对模型的有效性进行验证。通过对后踝关节面进行分区、切割,模拟计算后踝不同骨折范围条件下施加正常应力时的关节软骨接触面积、最大接触应力、平均接触应力、最大位移等参数。结果随着骨折范围的增加,胫骨软骨接触面积呈逐渐减小趋势,胫骨软骨的平均接触应力值逐渐增大,胫骨相对位移增加。胫距关节的应力区主要集中在踝穴的外侧及前外侧,当后踝骨折面积超过1/3时,关节负重区面积明显缩小,关节位移趋势增加。结论后踝骨折面积超过1/3时,关节接触面积明显减小,应力变化明显增加,关节位移趋势增加,预后不佳,具有手术复位固定的指征。  相似文献   

4.
<正>○含半月板的活体股胫关节接触特性有限元分析○肱骨外旋运动中盂肱关节面接触分析○基于MRI图像胫股关节有限元模型的建立○腰椎小关节力学机制的有限元分析○小关节角矢状化、椎间盘退变对退变性腰椎滑移作用的有限元研究  相似文献   

5.
背景:以往有研究表明了腰骶矢状面参数与腰椎间盘突出重吸收现象的相关性,但腰骶矢状面参数包括了腰椎前凸角、腰骶关节角、骶骨倾斜角等众多参数,且各参数对椎间盘重吸收的影响具有差异性;另外目前对具体某一节段椎间盘突出重吸收的研究尚少,测量数据也多从数字化X射线摄影或CT中获取,而从MRI中测量的腰骶矢状面参数与L5/S1椎间盘突出后发生重吸收的相关性报道则较少见。目的:观察L5/S1椎间盘突出重吸收后腰椎矢状面参数的相应改变,筛选出椎间盘重吸收过程中变化最显著的腰骶矢状面参数。方法:选择具有完整MRI影像资料的57例腰椎间盘突出症患者,符合腰椎间盘突出症诊断标准,且单纯接受非手术治疗L5/S1突出节段发生重吸收现象。MRI测量冠状面上的最大突出层面的突出面积、腰骶矢状面参数,包括腰椎曲线指数、腰椎前凸角(α)、L5/S1椎间盘角(β)、椎间隙高度、腰骶关节角、骶骨平台角、骶骨倾斜角、下腰椎前凸角,将腰骶矢状面参数在R软...  相似文献   

6.
本文测量82例成人脑颅正中矢状面,绝大多数颅因左右两半不对称,其正中矢状面皆出现旋转和偏移,只有7.31%符合标准。其偏离规律是:当 N—RPO径越大,i—LPO 径也越大,而 N—LPO 径与 i—RPO 径就相对地越小,以 Ni 连线为标志的脑颅正中矢状面,则出现逆时钟方向旋转,并向左侧偏移,相反时,即 N—RPO 径越小,i—LPO 径也越小,而 N—LPO 径与 i—RPO 径也就越大,颅正中矢状面则顺时钟方向旋转或不旋转,同时向右侧偏移或不偏移。其旋转方向,角度以及左右方向偏移距离,可测定 N—LPO,N—RPO,i—LPO,j—RPO,LPO—RPO五条径线长度后,据此作图,即可量出。  相似文献   

7.
目的 探讨青少年特发性脊柱侧弯(adolescent idiopathic scoliosis, AIS)矢状位平衡与足底压力之间的相关性。方法 选取40名符合标准的AIS患者。对每位患者在X线片拍摄后进行足底压力测试。矢状位参数测量包括腰椎前凸(lumbar lordosis,LL)、胸椎后凸(thoracic kyphosis,TK)、骶骨倾斜角(sacral slope,SS)、骨盆入射角(pelvic incidence,PI)、骨盆倾斜角(pelvic tilt,PT)、脊柱骶骨角(spine sacral angle,SSA)和C7矢状位垂直距离(C7 sagittal vertical axis,C7 SVA)。足底压力参数测量包括双脚前后足的接触面积和压力占比。分析矢状位参数与足底压力参数之间的相关性。结果 矢状位参数之间,LL与SS、PI、PT、SSA均有相关性;PI与SS、PT、SSA均有相关性;SS与SSA强相关;C7 SVA与SSA有相关性。在主弯侧,LL与后足及整足的接触面积呈负相关,与后足及整足的压力占比呈正相关;TK与前足压力占比呈负相关;PT与前、后足及整足接触面积均呈正相关。其他矢状位参数如SS、PI、SSA及C7 SVA与足底压力无关。在主弯对侧,矢状位参数与足底压力均无相关性。结论 在AIS中,矢状位平衡参数与足底压力分布密切相关,尤其是矢状位参数LL、TK、PT与足底压力指标最相关。  相似文献   

8.
目的:研究髌骨矢状面截骨术对髌骨倾斜病理应力分布的影响。方法:采用手术方法将七具新鲜人尸体膝关节标本的髌骨外侧支持带紧缩,造成髌骨过度外侧倾斜,然后进行四个不同截骨角的髌骨矢状面截骨术。股四头肌腱加载200N。分别于正常状态、髌骨倾斜、截骨5°、10°、15°、20°六种工况下,应用压敏片测量髌股关节接触压力与面积。摄屈膝45°Merchant髌骨轴位片,测量髌骨倾斜角,了解髌骨倾斜程度。结果与结论:髌骨倾斜后,髌骨内侧接触面积与压力均减少,外例接触面积与压力均增加,屈膝30°时最显著。截骨10°以上,明显改善了髌骨倾斜的应力分布,其中截骨15°改善较为理想。本实验结果为临床上髌骨矢状面截骨术中截骨角的选择提供了可靠依据。  相似文献   

9.
目的 建立活动平台膝关节单髁置换(mobile-bearing unicompartmental knee arthroplasty, MB-UKA)术前、术后 膝关节有限元模型,研究 MB-UKA 胫骨假体后倾角对关节接触应力影响。 方法 基于健康受试者计算机断层 (computed tomography,CT)及磁共振(magnetic resonance,MR)影像,构建健康膝关节有限元模型,并验证 MB-UKA 术前、术后模型的有效性。 模拟 MB-UKA 胫骨假体后倾 7°手术,将三维运动捕捉系统及力平台相关参数作为有限 元模型输入条件,分别计算外侧间室胫骨平台软骨和聚乙烯衬垫的最大接触应力。 结果 与现有文献结果进行对 比验证表明,健康膝关节和 MB-UKA 术后膝关节有限元模型计算结果较为合理。 MB-UKA 术后胫股关节接触应力 变化较大,聚乙烯衬垫接触应力远大于对侧间室胫骨平台软骨接触应力。 结论 本文所建 MB-UKA 术前、术后有 限元模型较为合理。 研究结果为 MB-UKA 的评估提供了一个可参考的方法。  相似文献   

10.
背景:颈胸交界区脊柱矢状面平衡不仅与全脊柱矢状面平衡相关,还与颈椎矢状面平衡相关。目的:探讨无症状成人颈胸交界区脊柱矢状面参数的相关性。方法:选择2017年1月至2018年12月在河北医科大学第二医院体检中心行健康体检且无颈椎病相关临床症状者120名,年龄23-79岁,根据年龄分为21-40岁组、41-60岁组、61-80岁组,每组40名,均拍摄颈椎侧位DR影像,测量下面影像学参数:C2-C7矢状面轴向垂直距离、头部重心到C7椎体矢状面轴向垂直距离、胸廓入口角、颈倾角、T1倾斜角、颅倾角。结果与结论:①3组间C2-C7矢状面轴向垂直距离、头部重心到C7椎体矢状面轴向垂直距离、胸廓入口角、颈倾角、T1倾斜角、颅倾角比较差异均有显著性意义(P<0.05),并且组间两两比较差异亦有显著性意义(P<0.05);胸廓入口角、颈倾角、T1倾斜角随着年龄的增大而增大;②相关性分析显示胸廓入口角、颈倾角、T1倾斜角与年龄呈正相关(r=0.622,r=0.439,r=0.533,P均<0.001);胸廓入口角与T1倾斜角呈正相关(r=0.569,P<0.001);胸廓入口角、T1倾斜角均与C2-C7矢状面轴向垂直距离呈负相关(r=-0.725,r=-0.352,P均<0.001);③结果表明,无症状成人胸廓入口角、颈倾角、颅倾角、T1倾斜角呈随年龄增大而增大的趋势,且胸廓入口角、颈倾角、T1倾斜角与年龄呈正相关。  相似文献   

11.
The aim of this research was to investigate the optimization of the geometry of an UHMWPE type of knee implant in the sagittal plane with minimum amount of wear. Finite element analysis has been used to analyze our proposed 780 models consisting of different design parameters. Maximum stress occurring in the whole tibial component, on the surface or subsurface of the plate, was considered as a design parameter to evaluate the wear condition. By avoiding the small contact area and high stresses in the tibial part, the maximum safe flexion angles have been determined. Other effective design factors such as implant stability, roll back distance, patella lever arm, and minimum bone resection have also been considered. Taking into account the variable parameters in the geometry of the implant parts, all possible models for the femoral component, which is made from metal, and the tibial component, which is made from UHMWPE, have been built in ANSYS and analyzed in the sagittal plane. By considering the effective mechanisms of wear in polyethylene, the results of the analyses were used to find the optimized geometry of a knee implant. This is the model, which is expected to experience the minimum wear, besides having some other properties of an ideal knee prosthesis.  相似文献   

12.
Esenkaya I  Unay K 《The Knee》2012,19(4):416-421
The patellar tendon length changes and patella infera occurs in medial open wedge osteotomies. We hypothesized that patellar tendon length in the sagittal plane would not change in a proximal medial tibial biplanar retrotubercle open wedge osteotomy. Proximal medial tibial biplanar retrotubercle open wedge osteotomies were conducted on 23 knees of 22 patients; the mean patient age was 59 ± 7 years (range, 53-69 years). The surgical procedure used had some technical distinctions from those used in literature. The mean follow-up was 37 ± 11 months (range, 19-58 months). Preoperative and postoperative Hospital for Special Surgery Scoring System (HSS) scores, radiological tibial slope, Insall-Salvati, Blackburne-Peel, and Caton indices, femoro-tibial anatomical axis angle, the angle between the femoral condyle and tibial plateau, and the angle between the tibial plateau and tibial axis were measured and compared statistically. Postoperative HSS scores were statistically higher than the preoperative HSS scores. The femoro-tibial axis angle, the angle between the femoral condyle and tibial plateau, and the angle between the tibial plateau and tibial axes decreased significantly. No statistical difference was observed between the preoperative and postoperative Insall-Salvati, Blackburne-Peel, or Caton indices. When we performed proximal medial tibial biplanar retrotubercle open wedge osteotomy, clinical and radiological recovery was observed but patellar height did not change.  相似文献   

13.
《The Knee》2020,27(5):1484-1491
BackgroundLocalized cartilage defects are related to joint pain and reduced function to the development of osteoarthritis. The mechanical properties of the implant for treatment do influence its longevity. Therefore, we aimed to evaluate the effect of material properties' variations of anatomically shaped focal knee implants in the knee joint using numerical finite element analysis.MethodsComputational simulations were performed for different cases including an intact knee, a knee with a focal cartilage defect, and a knee fitted with a focal articular prosthetic having three distinct mechanical properties: cobalt–chromium, pyrolytic carbon, and polyethylene. Femoral cartilage, tibial cartilage, and menisci contact pressures were evaluated under the load. In addition, bone stress was evaluated to investigate the stress shielding effect.ResultsCompared with the intact model, the contact stress of the focal implant model was increased; on the femoral lateral cartilage by 14%, on medial and lateral tibial cartilages by nine percent and 10%, on medial and lateral menisci by 23% and 20%. In contrast, the focal implant model had no effect on the menisci but contact stress on the tibial cartilage increased compared with the intact model. The BioPoly model showed the lowest contact stress on femoral and tibial cartilages. Additionally, the cobalt–chromium model showed the lowest bone stress that improved the load-sharing effect.ConclusionsThe results suggested that implant material properties are an important parameter in the design of a focal implant. The polyethylene model potentially restored the intact knee contact mechanics and it reduced the risk of physiological damage to the articular cartilage.  相似文献   

14.
The ability to quantify in vivo femoro-tibial relations in the knee holds great advantage to further patient care. There is little consensus on the optimal weight-bearing environment and measurement method for MRI assessment of in vivo knee kinematics. This study set out to establish the optimal method of measuring femoro-tibial relations in an upright, weight-bearing environment in normal individuals and those with ACL deficiency. Upright, load bearing, MRI scans of both knees were evaluated by two methods, flexion facet centre (FFC) and femoro-tibial contact point (FTCP), in order to establish femoro-tibial relations in the sagittal plane throughout different angles of knee flexion. A group of healthy volunteers (n = 5) and a group with unilateral ACL insufficiency (n = 8) were studied. Abnormal femoro-tibial relations were found in all ACL-deficient knees (n = 8): the lateral tibial plateau was anteriorly displaced in extension and early flexion and, coupled with smaller changes in the medical compartment, this constitutes internal rotation of the tibia relative to the femur in early flexion. This study found that the FFC measurement technique holds an advantage over the FTCP technique in terms of validity, repeatability and ease of measurements, allowing detection of kinematic changes such as tibial internal rotation in early flexion in ACL-deficient knees in an upright weight-bearing model. We propose that FFC measurement in an upright, weight-bearing position is a reliable and representative tool for the assessment of femoro-tibial movement.  相似文献   

15.
It is well known that the wear factor for ultra-high molecular weight polyethylene (UHMWPE) sliding on metallic or ceramic counterfaces is largely independent of contact stress for modest loading conditions and sliding distances. However, it is now recognized that under more severe stress levels and with sliding distances comparable to those encountered in current replacement synovial joints, subsurface fatigue contributes to the volume of wear debris. Since the fatigue process is influenced by surface stress levels it is becoming increasingly important to limit the contact stress through design in order to minimize the volume of UHMWPE wear debris in implants. The contact pressure in UHMWPE acetabular cups has been predicted using both the simple elasticity analysis and the finite element method. It has been shown that the radial clearance between the femoral head and the socket is the dominant parameter in determining the contact stress. Thus, the radial clearance should be controlled so the contact half width is close to the femoral head radius (a total included angle of contact of 120°) to minimize the contact pressure. There is little benefit to be gained by increasing the contact half width greater than the femoral head radius. This is consistent with the geometrical constraint of the anatomical position and the direction of loading. It has been shown that the radius of the femoral head has the most significant effect on the maximum contact pressure for these closely conforming contacts where the contact half width is close to the femoral head radius. The effect of the elastic modulus and the thickness of UHMWPE is relatively small under these contact conditions. However, an increase of the elastic modulus and a decrease of the layer thickness both result in a decrease of the radial clearance required to minimize the contact stress and this may prove to be impractical. This places a further constraint on the design of the contact. This paper demonstrates that with careful selection of the tribological design parameters, contact stress on acetabular cups can be reduced and this is more easily achieved with larger diameter femoral heads.  相似文献   

16.
BackgroundMotion axial system may affect contact stress of hinge knee prosthesis. However, it is unclear which axial system provides the better biomechanical effect. Therefore, the aim of this study was to compare the contact stress and stress distribution on the tibial insert and the bushing of hinge knee prostheses with a biaxial (BA) system and a spherical center axial (SA) system during a gait cycle.MethodsThree-dimensional finite-element (FE) models of the prostheses with different motion systems were included. The comparisons between experimental tests and FE analyses were performed to verify the models. Dynamic implicit FE analyses were performed to investigate the peak contact stresses and stress distributions on the tibial insert and the bushing.ResultsThe peak contact stresses on the tibial insert and the bushing of the BA prosthesis were higher than those of the SA prosthesis during most gait cycles. The contact time on the bushing is short in the SA prosthesis. The stress distributions on the superior surface of the tibial insert in the BA prosthesis were at the posterior side, but of the SA prosthesis were not fixed.ConclusionThe SA prosthesis has a lower peak contact stress on tibial insert and bushing than the BA prosthesis; in addition, the SA prosthesis has a ‘self-adjustment’ mechanism which could disperse high stress on the tibial insert to decrease the risk of wear and damage. The comparison could help designers and surgeons to better understand the future design of rotating hinge knee prostheses which should be able to achieve multiaxial motion and complete weight bearing by the tibial condylar to transmit the axial force better.  相似文献   

17.
目的:利用有限元的方法分析各种腹腔镜抓钳的形貌,为腹腔镜抓钳的设计提供依据。方法:分析抓取肝脏组织时,抓钳倒圆半径、齿数、钳头面积、雕镂面积对组织-器械接触面最大等效应力的影响,并通过正交试验分析以上因素的主次要地位。结果:随着组织-器械接触面有效接触面积的增加,产生的最大等效应力及其变化率逐渐变小。4种因素的主次要地位依次为:钳头面积>齿数>倒圆半径>雕镂面积。结论:应根据需要选择最优的抓钳,防止产生过大的等效应力,损伤组织,并且应以钳头面积为主,另外3种因素为辅进行腹腔镜抓钳设计。  相似文献   

18.
BackgroundThe most common modes of failure reported in unicompartmental knee arthroplasty (UKA) in its first two decades were wear on the polyethylene (PE) insert, component loosening, and progressive osteoarthritis in the other compartment. The rates of implant failure due to poor component positioning in patients who have undergone UKA have been reported. However, the effect of the posterior tibial slope on the biomechanical behavior of mobile-bearing Oxford medial UKA remains unknown.MethodsWe applied finite element (FE) analysis to evaluate the effects of the posterior tibial slope in mobile-bearing UKA on the contact stresses in the superior and inferior surfaces of PE inserts and articular cartilage as well as the forces exerted on the anterior cruciate ligament (ACL). Seven FE models for posterior tibial slopes of −1°, 1°, 3°, 5°, 7°, 9°, and 11° were developed and analyzed under normal-level walking conditions based on this approach.ResultsThe maximum contact stresses on both the superior and inferior surfaces of the PE insert decreased as the posterior tibial slope increased. However, the maximum contact stress on the lateral articular cartilage and the force exerted on the ACL increased as the posterior tibial slope increased.ConclusionsIncreasing the tibial slope led to a reduction in the contact stress on the PE insert. However, a high contact stress on the other compartment and increased ACL force can cause progressive osteoarthritis in the other compartment and failure of the ACL.  相似文献   

19.
BackgroundAsymmetric tibial insert design is expected to restore normal knee kinematics better than symmetric design. A tri-condylar implant has asymmetric and symmetric tibial inserts with a ball-and-socket joint to replace the post-cam mechanism. The purpose of this study was to compare the knee kinematics of the two designs and to measure tibiofemoral contact stresses, including that of the ball-and-socket joint.MethodsUsing a computer simulation, the anteroposterior position and axial rotation of the femoral component were simulated during a weight-bearing deep knee bend for six validated models. Contact forces were simultaneously simulated in the medial, lateral, and ball-and-socket compartments. The relative position and the magnitude and direction of each contact force were applied to aforce/displacement control knee simulator. The contact stresses were measured individually using a pressure sensor.ResultsThe asymmetric tibial insert demonstrated a more posterior position of the femoral component in the lateral compartment during the entire range of motion and greater external rotation of the femoral component, compared to the symmetrical tibial insert. The mean peak contact stress of the medial and lateral compartments was < 9 Mpa, with no significant differences between the two designs except at 0°. The contact stress of the ball-and-socket joint was < 5 MPa.ConclusionsAsymmetry of the tibial insert shows significant kinematic difference and has little influence on the peak contact stress, which is considerably lower than the yield strength of polyethylene. The asymmetric tibial insert can lead to clinical benefits owing to its kinematic and kinetic properties.  相似文献   

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