金属对金属髋关节动态边缘接触力学行为

目的研究球面共型接触人工髋关节在股骨头动态位移条件下的边缘接触力学行为。方法基于所发展的有限元球面网格数据模型,动态模拟分析金属对金属人工髋关节在给定生理位移工况条件下的接触行为和可能诱发的边缘接触现象。结果数值模拟表明,随着动态位移载荷的增加,关节接触面压力合力的垂直分力和水平分力都有上升趋势;在边缘接触过程中压力合力的垂直分力比非边缘接触情况变化趋势要缓慢,但相应的水平分力增大趋势更显著。此外,边缘接触与非边缘接触对应的接触压力分布形态与接触区域也各不相同。结论金属对金属人工关节髋臼相对股骨头过大的倾斜状态极易引起边缘接触,动态边缘接触情况下,将导致股骨头向髋臼内侧产生相对滑动及附加磨损的可能,这对临床人工髋关节磨损评估与关节制造发展提供了分析依据。     

非球面人工髋关节接触力学

目的由于受制造技术的局限性、可能的设计优化考虑以及临床应用的磨损等因素影响,人工髋关节轴承表面表现为非球面几何特征,可以利用有限元分析方法对非球面人工髋关节的接触力学行为进行研究。方法对球面网格数据模型进行非球关节面重建,研究不同取向椭球面股骨头对球面髋臼几何特征的非球面金属对金属人工髋关节的接触力学表现。结果非球面股骨头接触区域中心位置的平均曲率半径在一定范围内增大时,能有效降低相应关节接触面上的最大接触压力,同时接触面积有所增加;在同样载荷下,髋臼相对股骨头不同倾斜状态对非球面股骨头的接触压力峰值和面积影响较小,但压力分布有所不同。结论良好地控制人工髋关节的非球表面特征,有利于改善人工髋关节最大接触压力幅值大小和接触区域分布。所发展的非球面人工髋关节接触模型及数值模拟过程能够有效地运行,这为非球面关节动态接触及磨损预测问题研究提供了条件。     

金属对金属人工髋关节的磨损预测

目的发展复杂动态载荷与瞬态运动条件下的球面共型接触硬对硬人工髋关节的磨损预测模型,并用于典型的金属对金属人工髋关节在复杂三维生理运动条件下的磨损预测研究。方法建立有限元模型用于接触力学问题求解,采用固定-跟踪法(fixed-tracked method)完成具有三维欧拉运动的人工髋关节双侧界面动态磨损几何再现及相应的接触与磨损问题模拟的数值交换。结果磨损预测表明,磨损导致金属对金属人工髋关节接触界面几何由球面向非球面过渡,接触区域随磨损周期而增大,接触压力变化趋于平缓、最大接触压力逐渐减小。结论本研究所发展的三维复杂动态、具有双侧界面几何磨损变化的人工髋关节磨损预测模型,能够很好地进行金属对金属髋关节磨损数值预测模拟实验,为认识人工髋关节磨损机理提供了新的方法。     

髋臼发育不良性髋关节的三维有限元非线性接触压力分析

目的 从生物力学角度探讨髋臼覆盖程度(CE角)在髋臼发育不良引起的髋关节继发性骨关节炎中的作用。方法 建立正常、髋臼发育不良及髋臼过渡覆盖的髋关节三维有限元模型,应用非线性接触压力分析方法,观察髋臼发育不良性髋关节的关节软骨接触压力及软骨下骨应力分布。结果在所有的模型中,接触压力及应力均发生在股骨头最上部及与其相对应的髋臼顶穹部。在髋臼发育不良的模型中,另有过度不正常的接触压力发生在髋臼的后上缘区域。随着CE角的减小,接触压力和峰应力明显增高,接触面积下降。当CE角大于30°,压力分布类型及接触压力和峰应力改变不明显。结论髋臼覆盖程度降低所导致的生物力学改变在髋关节继发性骨关节炎中起重要作用。     

计算机模拟全髋关节置换术后假体位置对关节活动的影响

目的　通过计算机模拟全髋关节置换术,研究假体位置对关节活动度及稳定性的影响。 方法　以CT数据为基础,利用计算机三维重建及虚拟手术技术建立全髋关节置换术后三维模型,在不同假体位置模拟关节运动并测量关节发生撞击前的最大活动范围。 结果　(1)髋臼外展角增大可导致屈、伸、屈曲90°内旋活动范围增大,对外旋影响小;髋臼及股骨前倾角增大均可导致屈及屈90°内旋活动范围增大,而伸及外旋均减小。(2)为满足日常活动需要,取较大髋臼外展角时,髋臼前倾角宜适当减小;取较小髋臼前倾角时,股骨前倾角宜适当增大,反之亦然;而髋臼外展角与股骨前倾角的相对位置取决于髋臼前倾角。 结论　在全髋关节置换术中,把握好假体的相对位置可改善关节活动范围,增加关节稳定性。此外,本结果对髋关节假体翻修术中假体安放及术后脱位患者日常活动范围具有重要的指导意义。     

髋关节成形术后髋臼与股骨假体对髋臼运动范围的定向影响

背景　全髋关节矫形后 ,位置固定不适引起假体冲击 ,从而限制髋关节的活动范围。在这项研究中 ,计算机模型模拟研究髋臼与股骨头的位置状况 ,不同的头颈比率对假体冲击和肢体运动范围的影响。方法　计算机模拟三维的一般性半球形髋臼假体 :颈直径 12 .2 5 mm,头部大小从 2 2～ 32 m m不等 ,髋臼外展 35°～5 5°,前倾 0°～ 30°,测出髋关节的最大活动范围。稳定的髋关节最大弯曲度 :内收 10°,内旋 10°,外旋 10°。所以假体定向定位对于日常生活有重要影响。结果　小于 45°髋臼外展角度会降低髋关节弯曲和外展 ,而大角度会影响内收和旋转…     

大直径金属/金属股骨头人工全髋关节置换治疗股骨头缺血坏死**☆

背景：与以往大直径股骨头的高磨损率和高髋臼松动率相比,新一代大直径金属对金属全髋关节有着更长的使用寿命和低磨损,低脱位率等优点。 目的：评价应用大直径金属/金属股骨头人工全髋关节置换术治疗股骨头缺血坏死的临床疗效。 方法：回顾性分析26例股骨头缺血坏死患者实施单侧大直径金属/金属股骨头人工全髋关节置换资料。 结果与结论：所有患者均获得随访,在随访期内影像学显示假体位置良好,无假体松动,脱位等并发症。Harris评分由置换前49.5分改善为置换后92.5分,优良率为96%,总体满意率为96%。置换前后及随访时未发生假体松动、脱位、感染等不良反应。说明大直径金属/金属股骨头全髋关节置换治疗股骨头缺血坏死可获得较好的疗效,短期内无明显肾功能变化。     

材料匹配与人工髋关节接触性能分析

目的 研究当前临床常用的不同材料匹配的典型人工髋关节接触力学性能。方法 建立球基共型接触人工髋关节的有限元模型;通过施加恒定竖直方向载荷,等效模拟关节正常行走情况下的接触力学,分析材料匹配球面的接触性能及评估相应的磨损预测。结果 获得具有诸如金属对金属（MOM）、金属对陶瓷(MOC)、陶瓷对陶瓷(COC)、陶瓷对聚合物(COP)、金属对聚合物(MOP)5种材料组配条件下的人工髋关节接触性能数值分析;结果显示其接触应力由大到小排列分别为COC、MOC、MOM、COP和MOP;而接触面积由大到小排列分别为MOP、COP、MOM、MOC和COC。结论 高弹性模量和低泊松比的材料匹配的人工髋关节变形量较小,但会导致局部应力较大;将低弹性模量和高泊松比的柔性材料聚乙烯作为髋臼,则不会出现较大的接触应力集中,但变形量较大,且出现边缘受力情况。另一方面,MOM和MOC材料匹配的人工髋关节具有较低的接触磨损性能,对临床上人工髋关节选材提供参考价值。     

Cam型髋关节撞击综合征关节软骨接触力学的有限元分析

目的 通过有限元方法探讨不同严重程度的Cam型髋关节撞击综合征(femoroacetabular impingement,FAI)关节软骨接触力学的变化。方法 建立正常髋关节及不同α角的 Cam型FAI髋关节三维有限元模型,计算行走、坐下、起立等日常活动下的关节软骨接触压力和应力。结果 完整步态周期加载过程中,不同α角的Cam型FAI软骨接触压力分布与正常髋关节接近,无高接触压力和Von Mises应力集中区域;坐下、起立加载过程中,Cam型FAI软骨接触压力均大于正常髋关节,且随α角的增加而增大,其接触区域主要位于髋臼缘前上方,局部出现过高压力和Von Mises应力集中。结论 Cam型FAI软骨接触力学变化的关键影响因素是运动方式,关节软骨过高的接触压力和Von Mises应力,可能是其引起软骨退变并最终导致骨性关节炎的力学原因。     

髋臼杯的安放角度对假体稳定性的影响

目的：了解髋关节置换手术中髋臼杯安放角度的研究进展,为临床应用提供进一步参考。方法：搜集并分析近年来国内外对于在人工髋关节置换手术中髋臼杯应如何安放的大量文献,总结该手术方案目前的研究现状。结果：髋臼杯外展40°-45°时可获得最佳的活动范围,前倾角在10°-20°比较合理。结论：人工髋关节置换术中,髋臼假体外展角和前倾角的精确安放对关节的稳定性十分重要;在其安全角度范围内植入假体可获得对股骨头良好的包容性及最佳匹配,并保障了关节假体的稳定性。     

The contact mechanics and occurrence of edge loading in modular metal-on-polyethylene total hip replacement during daily activities

The occurrence of edge loading in hip joint replacement has been associated with many factors such as prosthetic design, component malposition and activities of daily living. The present study aimed to quantify the occurrence of edge loading/contact at the articulating surface and to evaluate the effect of cup angles and edge loading on the contact mechanics of a modular metal-on-polyethylene (MoP) total hip replacement (THR) during different daily activities. A three-dimensional finite element model was developed based on a modular MoP bearing system. Different cup inclination and anteversion angles were modelled and six daily activities were considered. The results showed that edge loading was predicted during normal walking, ascending and descending stairs activities under steep cup inclination conditions (≥55°) while no edge loading was observed during standing up, sitting down and knee bending activities. The duration of edge loading increased with increased cup inclination angles and was affected by the cup anteversion angles. Edge loading caused elevated contact pressure at the articulating surface and substantially increased equivalent plastic strain of the polyethylene liner. The present study suggested that correct positioning the component to avoid edge loading that may occur during daily activities is important for MoP THR in clinical practice.     

The effect of cup inclination and wear on the contact mechanics and cement fixation for ultra high molecular weight polyethylene total hip replacements

The present study aimed to investigate individual and combined influences of the cup inclination and wear on the contact mechanics and fixation of a Charnley hip replacement using finite element method. The effects of cup inclination and penetration on the contact mechanics of articulating bearings as well as the stress within the cement and at the bone-cement interface were examined. The maximum contact pressure and the von Mises stress on the cup were reduced by ~30% and ~20% respectively when even a small penetration occurred. However, no large differences were found between different cup penetration depths with regards to either the contact pressure or the von Mises stress. The von Mises stress at the bone-cement interface was predicted almost unaltered with an increased cup inclination angle to 55° for a cup penetration to 4mm. These predictions suggest that the contact mechanics and the cement stress are insensitive to the cup inclination and wear under these normal conditions investigated, therefore explaining the robustness of the Charnley hip implant. An increase in the cup inclination angle to 65°, coupled with a maximum penetration of 4mm, resulted in a large increase in the maximum von Mises stress at the bone-cement interface.     

The effect of motion patterns on edge-loading of metal-on-metal hip resurfacing

The occurrence of pseudotumours (soft tissue masses relating to the hip joint) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) has been associated with high serum metal ion levels and consequently higher than normal bearing wear. We investigated the relationship between serum metal ion levels and contact stress on the acetabular component of MoMHRA patients for two functional activities; gait and stair descent. Four subjects with MoMHRA, who had their serum metal ion levels measured, underwent motion analysis followed by CT scanning. Their motion capture data was combined with published hip contact forces and finite element models representing 14% (peak force) and 60% (end of stance) of the gait cycle and 52% (peak force) of stair descent activity were created. The inclination angle of the acetabular component was increased by 10° in 1° intervals and the contact stresses were determined at each interval for each subject.When the inclination angle was altered in such a way as to cause the hip contact force to pass through the edge of the acetabular component edge-loading occurred. Edge-loading increased the contact stress by at least 50%; the maximum increase was 108%. Patients with low serum metal ion levels showed no increase in contact stress at peak force during gait or stair descent. Patients with high serum metal ion levels exhibited edge-loading with an increase to the inclination angle of their acetabular components. The increase in inclination angle that induced edge-loading for these subjects was less than the inter-subject variability in the angle of published hip contact forces. The results of this study suggest that high serum metal ion levels are the result of inclination angle influenced edge-loading but that edge-loading cannot be attributed to inclination angle alone and that an individual's activity patterns can reduce or even override the influence of a steep acetabular component and prevent edge-loading.     

Contact mechanics studies of an ellipsoidal contact bearing surface of metal-on-metal hip prostheses under micro-lateralization

The morphology of the contact bearing surfaces plays an important role in the contact mechanics and potential wear of metal-on-metal (MOM) hip prostheses. An ellipsoidal bearing surface was proposed for MOM hip implants and the corresponding contact mechanics were studied by using the finite element method (FEM) under both standard and micro-lateralization conditions. When under micro-lateralization, the maximum contact pressure decreased from 927.3 MPa to 203.0 MPa, with increased ellipticity ratio medial-laterally. And the contact region was found to shift from the rim of the cup to the inner region compared to the spherical design. Under standard conditions, an increasing trend of the maximum contact pressure for the acetabular component was predicted as the major radius of the ellipsoidal bearing surface was increased. Nevertheless, the maximum contact pressure reached an asymptotic value when the ellipticity ratio was increased to 1.04. Therefore it is critical to optimize the ellipticity ratio in order to reduce the contact pressure under micro-lateralization condition and yet not to cause a markedly increased contact pressure under normal condition. Additionally, the maximum contact pressure in the ellipsoidal bearing surface remained relatively constant with the increased micro-lateralization. It is concluded that an ellipsoidal bearing surface morphology may be a promising alternative by offering better contact mechanisms when micro-lateralization should occur and attributing to minimized wear.     

Effects of design parameters of total hip components on the impingement angle and determination of the preferred liner skirt shape with an adequate oscillation angle

The oscillation angle (OsA), which is the sum of the impingement angles on the two sides when the prosthetic neck sways from the neutral axis of the acetabular cup to the liner rim, is one of the most important factors that can affect the range of motion of an artificial hip joint. The aim of this study was to determine the influence of total hip component design on the impingement angle. Our findings show that an increase in cup depth of the liner restricts the motion of the neck and results in a reduced impingement angle, while an increase in chamfer angle increases the impingement angle until it reaches a critical value when a further increase no longer results in an increase in impingement angle. The impingement angle is not only dependent on the head/neck ratio, but also on the head size itself. For most arbitrarily chosen cup depths and chamfer angles, the neck only impacts at one point on the liner. This study proposes a suitable combination of cup depth and chamfer angle and a preferred impact mode, which, if impingement does occur, enables the neck to impinge on the liner rim over a large area. Cup–neck combinations that have an adequate OsA with maximum femoral head coverage are presented.     

头颈比不同人工髋关节臼杯安置角度的安全范围

背景：由于假体安置角度不当时常导致臼柄撞击而使人工髋关节活动范围受限,不能满足正常的日常生活需要。目前人工全髋关节置换的臼杯安置角度一直存在争议,且对不同头颈比的人工髋关节置换中臼杯安置没有针对性指导。 目的：探讨不同头颈比人工髋关节臼杯安置角度的安全范围。 方法：参照人工髋关节内旋和外旋活动范围计算公式、人工髋关节内收和外展活动范围计算公式、人工髋关节前曲和后伸活动范围计算公式、髋臼外展角和前倾角动态变化的数学表达式,根据Widmer人工髋关节正常活动范围标准得不等式组：①外旋活动范围至少40°,内旋活动范围至少80°。②外展活动范围至少50°,内收活动范围至少50°。③前屈活动至少130°,后伸活动至少40°。解上述3组不等式得出不同头颈比人工髋关节臼杯安置角度安全范围。 结果与结论：不同头颈比的人工髋关节臼杯安置角度的安全范围不同。为满足正常髋关节活动范围人工髋关节头颈比应大于22/12,人工髋关节活动范围随头颈比增大逐渐增大,随头颈比增大臼杯安置外展角和前倾角度安全范围逐渐增大,具体头颈比臼杯外展角安全范围的上下极值随前倾角增大在一定的范围内逐渐增大,且极差亦逐渐增大。外展角安全范围的上极值随前倾角增大逐渐减小,而下极值逐渐增大对称波动于45°上下且逐渐趋向于45°,最大前倾时外展角均为45°。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

Predictors of patellar alignment during weight bearing: An examination of patellar height and trochlear geometry

BackgroundPatellar malalignment is thought to be an etiological factor with respect to the development of patellofemoral pain. Although previous studies have suggested that the geometry of the femoral trochlea and the height of the patella play an important role in determining patellar alignment, no investigation has systematically examined these relationships during weight bearing. The aim of this study was to determine whether patellar height and/or trochlear geometry predicts patellar alignment (lateral patellar displacement and lateral patellar tilt) during weight bearing.MethodsMR images of the patellofemoral joint were acquired from 36 participants during weight bearing (25% of body weight) at 4 knee flexion angles (0°, 20°, 40° and 60°). Using the axial images, patellar alignment (lateral displacement and tilt) and femoral trochlear geometry (sulcus angle and inclination of the lateral femoral trochlea) were measured. Patellar height (Insall–Salvati ratio) was measured on reconstructed sagittal plane images.ResultsStepwise regression analysis revealed that at 0° of knee flexion, the height of the patella was the best predictor of lateral patellar tilt while the lateral trochlea inclination angle was the best predictor of lateral patellar displacement. Lateral trochlear inclination was the best predictor of patellar lateral displacement and tilt at 20°, 40° and 60° of knee flexion.ConclusionSimilar to a previous study performed under non-weight bearing condition, our findings suggest that lateral trochlear inclination is an important determinant of patellar alignment in weight bearing.Level of EvidenceLevel III