金属对金属人工髋关节边缘接触效应

目的 研究金属对金属人工髋关节不同行走姿态下的接触力学行为,特别是大幅度运动可能导致的边缘接触效应。方法 建立球面共型接触的髋关节有限元模型,通过改变髋臼相对股骨头的倾斜状态和对股骨头施加恒定竖直方向载荷相结合,等效模拟分析人工髋关节不同行走姿态下的接触状态。结果 髋臼相对股骨头倾角在小于约60°范围内增加时,其对应的最大接触压力呈下降趋势,接触面积有所增大;当倾角超过80°范围时,关节接触区域因靠近髋臼边缘,最大接触压力位置由初始接触点向髋臼倾斜方向移动了约6°~9°的位置,用以满足压力分布合力与外载荷的平衡,接触压力和分布范围有所增加。结论 髋臼相对股骨头较大倾斜状态极易引起不同的边缘接触现象,置换人体髋关节产生的边缘接触问题需要引起临床外科和关节制造上的重视。     

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。     

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.     

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：     

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.     

头颈直径比与假体安装参数对髋关节活动度影响的计算机模拟研究

观察不同头颈直径比股骨假体全髋置换中,髋关节假体安装参数对髋关节活动度的影响,并探讨杯与颈前倾角优化组合。建立全髋关节假体三维可视化计算机模型,计算满足两组不同髋关节活动度下,髋臼外展角每变化5°时相应的髋臼前倾角安装角度,并在以髋臼外展角为横坐标,髋臼前倾角为纵坐标的坐标系上描点、连线画图,并对数据进行分析。实验显示,颈干角135°,髋关节一般标准和严格标准活动度,髋臼杯前倾角(Y)与股骨颈假体前倾角(X)的关系分别为Y1=-0.728X1+40.916,Y2=-0.7384 X2+46.456;允许的最小髋臼外展角(OImin)和头颈直径比(GR)的关系分别为OImin’1=254.27GR 1-3.172,OImin’2=230.58GR 2-2.519。髋关节活动度和髋臼安装角度安全范围随着头颈直径比增大而增大;髋关节活动度要求越高,髋臼安装角度安全范围越小。可允许的最小髋臼外展角随着头颈直径比的增大而变小。髋臼前倾角与股骨颈前倾角呈负相关。     

髋臼发育不良者全髋置换中臼杯置入位置的力学分析

目的　利用三维有限元分析方法,研究髋臼发育不良患者加深磨锉假体置入部位的髋臼骨床、使臼杯假体内移置入对髋臼假体-骨界面间的应力分布情况的影响。  方法　选取髋关节发育不良患者的骨盆为实验对象,螺旋CT做全长连续扫描,然后利用计算机仿真技术对CT图像进行三维重建,建立髋关节发育不良骨盆模型。在计算机环境中对重建模型进行髋臼磨锉,臼杯假体不同程度内移植入的模拟手术,利用有限元分析软件SolidWorks对重建模型进行有限元网格化及力学分析。  结果　臼杯假体的内移使臼杯上缘处获得骨床包容,臼杯接触面积更大,单位面积所受应力相对较少。随内移程度加大,髋臼内壁骨质突破更为明显,使髋臼顶部应力集中及其余部分应力不均愈趋明显。  结论　髋臼加深磨锉臼杯内移植入有助于改善髋关节发育不良病例行髋关节置换臼杯的骨床包容,但随内移程度的加大,髋臼内壁突破,髋臼面的应力集中,髋臼的应力分布情况明显改变,应尽量减少穿破的程度。     

Activity-dependence of the "safe zone" for impingement versus dislocation avoidance

Presently, the basis for optimal cup positioning to minimize the likelihood of dislocation rests upon subjective clinical impressions. To help elucidate optimal cup positioning more objectively, and to clarify the distinction between impingement avoidance and dislocation avoidance, kinematic and kinetic inputs for seven dislocation-prone activities were applied to finite element models of a contemporary 22-mm modular total hip reconstruction. Twenty-five cup placement positions (combinations of 30, 40, 50, 60, and 70 degrees of abduction with 0, 10, 20, 30, and 40 degrees of anteversion) were chosen to include the conventional 'safe zone' of 30-50 degrees of tilt and 5-25 degrees of anteversion. Activities studied were: rising from a low seat (toilet) and from a normal height chair, leg-crossing while seated, tying a shoe from a seated position, bending at the hip from an erect stance to retrieve an object on the floor (stooping), a standing pivot maneuver, and rolling over in bed. Neck-on-cup impingement occurred during one or more of the dislocation-prone activities at all 25 cup positions. Of the 175 combinations of cup position and kinetic challenge, dislocation and impingement events both occurred for 51 situations, while impingement occurred in 45 instances without dislocation, and dislocation occurred in 10 instances without impingement. Neither dislocation nor impingement was observed in the 69 other combinations of cup position and loading challenge. Kappa statistics showed dislocation and impingement, as outcome measures of activity-dependent challenges, exhibit little more than chance agreement. Therefore, the use of impingement range of motion (ROM) as a predictor of a given cup position's vulnerability to dislocation should be viewed cautiously.     

髋臼及股骨上端畸形致人工髋关节置换术后脱位原因及对策

目的：分析髋臼及股骨上端畸形致人工髋关节置换(THR)术后脱位的原因，探讨防治对策。方法：本组行全髋置换术172例后发生脱位5例(2．9％)，其中后脱位4例，前脱位1例。发生时间最早在术毕搬动时，最迟在术后第20天。脱位原因分析，4例存在先天性髋臼发育不良，前倾角过小，术中未能调整；1例为股骨上端畸形，假体头臼对合不良。结果：复位后牵引6周1例、髋人字石膏固定6周1例，手术调整前倾角2例、调整股骨假体柄1例，均未发生再脱位。结论：为避免发生脱位，术前CT平扫了解髋臼前倾角和股骨头包容程度，做好特殊假体准备；术中加大加深髋臼以增加臼杯的包容度，并调整股骨头、颈角度来配合对应关系。术中人工髋试活动稳定性良好是减少术后脱位保证。     

髋关节假体置换中股骨头直径及髋臼前倾角的作用

背景：后脱位在人工髋关节置换后并发症中发生率仅次于假体松动,严重影响髋关节的稳定性。目前在临床研究中股骨头直径及髋臼前倾角对髋关节稳定性的影响尚存争议。 目的：探讨股骨头直径和髋臼前倾角在人工髋关节置换后对髋关节稳定性的影响。 方法：在尸体骨上测量全髋关节置换后影响髋关节后向不稳定的股骨头直径和髋臼前倾角。前倾角在计算机导航引导下安装在0°-20°,其中每个间隔为5°。分别应用直径为28,32,36 mm的股骨头进行实验,观察髋关节屈曲90°内收0°以及屈曲90°内收30°时引起脱位的内旋角度。 结果与结论：当髋臼臼杯前倾角从0°增加到15°时,导致髋关节脱位的髋关节内旋角度随股骨头直径增加而增加(P < 0.05)。当髋臼臼杯前倾角度从15°增加到20°时,导致髋关节脱位的髋关节内旋角度随股骨头直径增加而增加的趋势不明显。在髋关节屈曲90°内收0°时,当髋臼臼杯前倾由15°增加到20°,股骨头直径36 mm组相对于28 mm和32 mm组有更高的稳定性(P< 0.01);当髋臼前倾角度大于10°时,股骨头直径32 mm组与28 mm组相比具有更好的稳定性(P < 0.05);当髋臼前倾角小于10°时,此种区别不是很明显。当髋关节屈曲90°内收30°,股骨头直径36 mm组相对于28 mm和32 mm组有更高的稳定性(P < 0.01);当髋臼前倾角度大于10°时,股骨头直径32 mm组与28 mm组相比具有更好的稳定性(P < 0.05);当髋臼前倾角小于10°时,此种区别不是很明显。结果提示髋臼前倾角的增加可减少髋关节后脱位的发生,但是当髋臼前倾角不是很好选择时,应用大直径的股骨头可增加髋关节的稳定性。     

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。     

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。     

A mathematical method for precisely calculating the radiographic angles of the cup after total hip arthroplasty

We established a mathematical method to precisely calculate the radiographic anteversion (RA) and radiographic inclination (RI) angles of the acetabular cup based on anterior–posterior (AP) pelvic radiographs after total hip arthroplasty. Using Mathematica software, a mathematical model for an oblique cone was established to simulate how AP pelvic radiographs are obtained and to address the relationship between the two-dimensional and three-dimensional geometry of the opening circle of the cup. In this model, the vertex was the X-ray beam source, and the generatrix was the ellipse in radiographs projected from the opening circle of the acetabular cup. Using this model, we established a series of mathematical formulas to reveal the differences between the true RA and RI cup angles and the measurements results achieved using traditional methods and AP pelvic radiographs and to precisely calculate the RA and RI cup angles based on post-operative AP pelvic radiographs. Statistical analysis indicated that traditional methods should be used with caution if traditional measurements methods are used to calculate the RA and RI cup angles with AP pelvic radiograph. The entire calculation process could be performed by an orthopedic surgeon with mathematical knowledge of basic matrix and vector equations.     

Dynamic behavior of tripolar hip endoprostheses under physiological conditions and their effect on stability

Tripolar systems have been implanted to reduce the risk of recurrent dislocation. However, there is little known about the dynamic behavior of tripolar hip endoprostheses under daily life conditions and achieved joint stability. Hence, the objective of this biomechanical study was to examine the in vivo dynamics and dislocation behavior of two types of tripolar systems compared to a standard total hip replacement (THR) with the same outer head diameter.Several load cases of daily life activities were applied to an eccentric and a concentric tripolar system by an industrial robot. During testing, the motion of the intermediate component was measured using a stereo camera system. Additionally, their behavior under different dislocation scenarios was investigated in comparison to a standard THR.For the eccentric tripolar system, the intermediate component demonstrated the shifting into moderate valgus-positions, regardless of the type of movement. This implant showed the highest resisting torque against dislocation in combination with a large range of motion. In contrast, the concentric tripolar system tended to remain in varus-positions and was primarily moved after stem contact. According to the results, eccentric tripolar systems can work well under in vivo conditions and increase hip joint stability in comparison to standard THRs.     

计算机导航中髋臼杯角度设定的可行方法及其精确性验证

目的:分析计算机导航对人工髋关节臼杯置入角度设定的可行性方法并评估其精确性.方法:将CT扫描资料进行计算机三维影像重建,并进行虚拟像与真实骨盆间匹配对应,在虚拟空间中,确立骨盆冠状、矢状、水平及前倾平面,并以此为基准进行计算机导航辅助下多角度设定的臼杯置入,由角度测量仪对臼杯置入角度的精确性进行测量验证.结果:导航辅助臼杯外展角置入,设定值与真实值间差异(0.46±1,53)°;对于臼杯前倾角,差异(0.79±1.37)°.两次独立操作所得结果作配对t检验,臼杯外展及前倾角均无显著性差异(t外展=1.15,t前倾=1.14,P>0.05).结论:研制的基于CT影像资料的计算机导航可有效的设定臼杯假体置入角度,精确地引导臼杯置入.     

SuperPATH微创与常规入路行全髋关节置换术的早期疗效比较

目的比较SuperPATH入路与常规入路行人工全髋关节置换术的早期疗效。方法回顾性分析比较2015年11月~2016年10月初次全髋关节置换术治疗的60例的临床资料,SuperPATH入路组、常规入路组各30例。比较两组手术时间、切口长度、术中出血量、输血量;臼杯外展角、前倾角、术后24 h疼痛视觉模拟VAS评分、术后6月Haris评分。结果与常规组相比,SuperPATH组切口较短、术后24 h VAS评分较低、术中出血量、输血量较少。两组的置换时间、髋臼角测量、术后6个月Harris评分差异均无统计学意义(0.05)。结论 SuperPATH微创人工全髋关节置换术切口小、疼痛轻、出血少,可快速康复。但SuperPATH入路存在安装假体难度相对较大,易致假体位置不佳等不足。     

Material optimization of femoral component of total hip prosthesis using fiber reinforced polymeric composites

In this report an integrated approach to the three-dimensional material optimization of femoral components of hip prostheses is described. The effectiveness of using reinforced fiber composites for the material optimization of hip implants has been demonstrated and general guidelines on some material design aspects of total hip replacement (THR), in terms of fiber volume fraction and fiber orientation angles, are provided. A modular program was developed to interface the optimization routine with the finite element code. In this study two cases of cemented and non-cemented THR were investigated. In both cases perfectly bonded interfaces were assumed. Two objective functions were defined based on interface failure criteria and bone adaptive remodeling to avoid interface disruption and to reduce the risk of bone loss. The overall results demonstrated the effectiveness of the technique, which can provide meaningful insights into the fiber-reinforced composite material design of orthopaedic implants.     

Influence of design parameters on cup-stem orientations for impingement free RoM in hip implants

This study was conducted to study the influence of design parameters namely; the head/neck ratio (R), neck-shaft angle (NSA), oscillation angle (OsA) and stem offset (Sθ) on cup-stem orientations namely; the cup inclination (CI), cup anteversion (CA) and stem antetorsion (SA). R is often linked to influence NSA, OsA and impingement. An effort has been made to analyze range of motion (RoM) with NSA greater than 135° and R lower than 2.3 that may produce impingement. This study attempted to answer the following assumptions whether (a) implants with higher H-N ratio can achieve higher oscillations and higher stem antetorsion, (b) stems with higher neck shaft angle can achieve higher cup anteversion with lower stem offset and stem antetorsion, (c) stem with higher offsets can achieve lower cup anteversion with higher stem antetorsion, and (d) lower cup anteversion can be achieved when stem antetorsion is higher. A theoretical and a simulated method were implemented to anaylze RoM until impingement between cup and neck occurred. Cup abduction and anterior opening were held constant for this study. Multivariate prediction models were developed to predict optimal cup-stem orientations for the chosen design parameters of 12 hip implants. Optimal design parameters to achieve an impingement free RoM were as follows: NSA=139.25°, R=3.08, OsA=119.83°, Sθ=34.45mm, CA(predicted)=16.26°, CI(predicted)=42.77° and SA(predicted)=30.37°, respectively. Multivariate models may be further developed for use in surgery planning to achieve optimal component placement.     

Asymmetric knee loading at heel contact during walking in patients with unilateral knee replacement

Increased load on the knee joint by excessive levels of impact forces during initial contact has been suggested to lead to knee osteoarthritis (OA). Asymmetric loading after knee replacement may also relate to the development of OA in the contralateral limb, therefore this study investigated the heel strike transient vertical force and subsequent lower extremity kinematic, kinetic and spatio-temporal parameters during level walking between the operated and the contralateral limbs in patients 12 months following unilateral knee replacement. A six camera motion analysis system with a force plate was used to investigate the differences between limbs in the heel strike transient vertical GRF and its relative timing, and hip, knee and ankle angles and moments at initial contact, as well as spatio-temporal parameters during the stance phase of walking in 19 subjects with unilateral knee replacement. Paired t tests showed a significant difference in the contralateral limb relative to the operated limb in the heel strike transient magnitude (p=0.03), hip moment (p=0.01), knee moment (p=0.02) and ankle moment (p=0.03). No significant differences were found for the joint angles at heel contact or the spatio-temporal parameters (p>0.05). The heel strike transient magnitude was lower for the operated limb with no differences in the spatio-temporal parameters or the joint angles at initial contact between the limbs. Differences in the hip, knee and ankle moments were also found indicating an asymmetric loading of the impact force at initial contact on the lower extremity. The current findings may indicate an asymmetric loading on the knee joint and therefore may be clinically relevant in patients undergoing unilateral knee replacement.     

全髋关节置换术中采用屈髋45°法判断联合前倾角的临床研究

目的：探讨全髋关节置换术（ THA ）中判断假体联合前倾角的一种新方法。方法：自2010年6月～2011年6月,对126例髋关节疾病行非骨水泥型THA治疗,并应用屈髋45°时股骨头试模边缘和髋臼内衬试模边缘的关系来判断假体的联合前倾角是否在安全区,并以此来调整髋臼杯假体的前倾角。结果：术中发现用屈髋45°定位法,假体的联合前倾角全部符合Dorr的安全区标准,髋关节活动度全部能达到D＇Lima标准。结论：THA术中先安装髋臼杯假体和股骨假体试模,利用屈髋45°时股骨头试模的边缘与髋臼杯内衬试模边缘平行的方法来调整髋臼杯试模的前倾角,测试髋关节活动度,最后再依次安装假体的方法,可以使患者的髋关节达到理想的活动范围和低脱位率。