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.     

Influence of femoral head size on impingement, dislocation and stress distribution in total hip replacement

Dislocation remains a serious complication of total hip replacement. An insufficient range of motion can lead to impingement of the prosthetic neck on the acetabular cup. Together with the initiation of subluxation and dislocation, recurrent impingement can cause material failure in the liner. The objective of this study was to generate a validated finite element (FE) model capable of predicting the dislocation stability of different femoral head sizes with regard to impingement in different implant positions as well as the corresponding stress distribution in the liner. In order to cover posterior and anterior dislocation, two total hip dislocation associated manoeuvres were simulated using a three-dimensional nonlinear finite element model. The dislocation stability of two head sizes was determined numerically and experimentally. After validation, the FE model was used to analyse the dislocation stability of four different head sizes in variable implant positions. Range of motion (ROM) until impingement, the resisting moment that was developed and ROM until dislocation were evaluated. Additionally, stress distribution within the polyethylene liner during impingement and subluxation was determined. For both dislocation modes, a cup position of 45 degrees lateral abduction and 15 degrees up to 30 degrees anteversion resulted in appropriate ROM and dislocation stability. In general, larger head diameters revealed an increase in ROM and higher resisting moments. Stress analysis showed decreased contact pressures at the egress site of the liners with the larger inner diameters during subluxation. The analysis shows that an optimal implant position and a larger head diameter can reduce the risk of dislocation induced by impingement. The finite element model that was developed enables simplification of design variations compared to experimental studies since prototyping and assembling are replaced by prompt numerical simulation.     

Wear analysis of chamfered elongated acetabular cup liners

This study investigated the wear phenomena of chamfered acetabular cup liners. The liners have three parameters at the lengthened rim: the length of the elongation, the depth of the cup and the chamfer angle. Using published wear volume equations for cylindrically elongated liners, this study analysed the volume of the chamfer to obtain the exact theoretical wear volume of the chamfered liner. The criteria described in our previous paper were used to verify the accuracy of the proposed methodology. The results showed that a shallow cup depth (<2 mm) and a chamfer angle of about 30° could significantly reduce the wear volume arising from the elongation. When the chamfer angle was increased further, this effect became progressively less significant. The results suggest that a chamfer angle up to about 30° is appropriate, but the angle should not be larger than required to obtain the minimum femoral range of motion (ROM). The results of this study can also be integrated with the analysis of the kinetics and kinematics of liners. A compromise design incorporating a lower wear volume, sufficient ROM and a lower contact stress should be possible.     

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：     

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。     

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。     

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。     

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。     

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.     

全髋置换术中臼杯置放角度对关节屈伸活动安全性的影响

目的:通过髋臼及臼杯的三维重建及基于此的解剖形态研究,就临床上臼杯假体安装角度对术后髋关节活动安全性改变作一定量分析。方法:通过CT扫描,图像边界处理和定标,利用三维运行软件拟合出髋臼及臼杯三维结构,利用MPR技术重建出髋臼水平及冠状切面,测算出臼杯前倾及外展角,并构建髋关节活动过程中,角度动态变化曲线。结果:骨盆由生理位向前倾斜,随着前倾的增加,臼杯外展角呈增加趋势;臼杯初始置入前倾角较大或外展角较小者,骨盆倾斜角度的变化所引起臼杯前倾角变化的幅度较大。骨盆由生理位向前倾斜,随着骨盆前倾状态的增加,臼杯前倾角呈减少趋势;臼杯初始置入的外展角越大,骨盆倾斜角度的变化所引起臼杯外展角变化的幅度越大。较大的初次臼杯置入前倾角,能减缓骨盆前倾状态增加所致臼杯前倾角减少的幅度。结论:臼杯前倾角及外展角间互相制约,在安全角度范围内作臼杯置入可取得髋臼杯对股骨头良好包容及生理安全活动度间的最佳匹配。     

髋关节表面置换改良杯的生物力学评价

髋关节表面置换术远期的松动率比全髋关节置换术高,且头杯的松动率较臼杯为高。但髋关节表面置换术具备一些全髋关节假体置换术所没有的优点,如:能保留健康的股骨颈,且尚有全髋关节假体置换术的余地。我们设计了新型的三翼头杯和杆栓杯,简称TC和BC。其中心杆使头杯与残存股骨颈一体化,使假体与残存骨质成为完整受力体系,均匀分散杯下应力。实验采用压力应变值和最大破坏扭矩来评价新头杯与传统头杯的力学稳定性。结果显示,TC综合力学性能最佳,有希望为临床提供一个较理想的头杯。     

The effect of dynamic hip motion on the micromotion of press-fit acetabular cups in six degrees of freedom

The hip joint is subjected to cyclic loading and motion during activities of daily living and this can induce micromotions at the bone-implant interface of cementless total hip replacements. Initial stability has been identified as a crucial factor to achieve osseointegration and long-term survival. Whilst fixation of femoral stems achieves good clinical results, the fixation of acetabular components remains a challenge. In vitro methods assessing cup stability keep the hip joint in a fixed position, overlooking the effect of hip motion. The effect of hip motion on cup micromotion using a hip motion simulator replicating hip flexion-extension and a six degrees of freedom measurement system was investigated. The results show an increase in cup micromotion under dynamic hip motion compared to Static Flexion. This highlights the need to incorporate hip motion and measure all degrees of freedom when assessing cup micromotion. In addition, comparison of two press-fit acetabular cups with different surface coatings suggested similar stability between the two cups. This new method provides a basis for a more representative protocol for future pre-clinical evaluation of different cup designs.     

不同透视角度下股骨颈前倾角测量值的变化

目的：研究不同透视角度下股骨颈前倾角测量值的变化,为临床一次摄片测量股骨颈前倾角提供理论依据。方法：将２０条股骨,左右各半,先使股骨与Ｘ光片垂直且位于Ｘ线管球正中摄片,测量前倾角标准值。再使股骨外展,与Ｘ线成３０°、４５°、６０°、７５°时摄片,测量在Ｘ光片上股骨颈纵轴投影与经过两髁间连线投影的夹角。同时用张怀韬方法重复测量。结果：两组股骨外展３０°、４５°时测量值相近,均小于股骨颈前倾角标准值,随着外展角度的增大,前倾角测量值逐渐增大,７５°时测量值与股骨颈前倾角标准值相差最小。并根据三角函数推导得出结果一致。结论：当股骨干外展７５°时,股骨颈前倾角测量值与实际值相近。     

女性穿着运动文胸与未着文胸状态下步态特征的差异性

目的比较女性穿着运动文胸和未着文胸行走时步态特征和步行稳定性的差异,为运动文胸的设计和评价提供依据。方法使用Qualisys红外光点运动捕捉系统采集12名C罩杯乳房大小女性分别穿着运动文胸及未着文胸状态下在跑步机上行走(6 km/h)的运动学参数。结果相比未着文胸状态,穿着运动文胸时上躯干角最大值及最小值显著减小,躯干屈曲角和躯干扭转角的幅度较小;10个步态周期的髋关节屈曲角幅度的标准差显著小于裸胸状态,乳房不同支撑状态对步频无显著影响。结论不同乳房支撑状态显著影响上躯干角度、躯干扭转角与躯干屈曲角。裸胸状态行走时躯干运动幅度增大,行走稳定性下降。不同乳房支撑状态下行走步频存在个体差异。     

无症状青年人群股骨颈α角CT测量多个平面之间的比较

目的　比较无症状青年人群中多个平面CT测量股骨颈α角的差异，并对凸轮型股髋撞击综合征（FAI）形态改变的发生率进行评估。  方法　回顾性分析2009年5月至2013年11月120例无髋关节病症患者（20～40岁）的腹部或盆腔CT扫描资料。α角的测量采用平行于股骨颈长轴的斜轴位平面以及以股骨颈中心作为旋转轴的4个方向辐射状层面,两者差异的比较采用方差分析，α角大于55°提示凸轮型FAI形态异常。  结果　斜轴位平面α角均值为(39.5±6.51) º，共有12人（占10%，12/120）、14个关节α角大于55 º，10人为单侧、2人为双侧；在12点、1点、2点及3点方向各平面的α角均值分别为(42.8±7.3) º,(48.8±7.6)º,(47.3±7.2)º,(40.2±6.7)º，在所有辐射状平面中共有106个关节α角大于55 º，其中在1:00方向有54个关节α角增大，占受试者的35%（42 /120）（30人为单侧，12人为双侧）；斜轴位平面与12点、1点、2点方向平面测量的α角之间的差异有统计学意义（P<0.05）。  结论　在辐射状平面测量α角可能更准确；无症状青年人群中，其类似凸轮型FAI的形态改变有较高的发生率。     

成人大骨节病与骨关节炎患者髋关节影像学表现的对比研究

目的：研究成人大骨节病髋关节病变的影像学特点,并与骨关节炎患者进行对比。方法：对四川省壤塘县112例（224髋）确诊为成人大骨节病的患者进行髋关节摄片,观察髋关节髋臼侧、股骨侧有无影像学改变,测量髋关节Sharp角、CE角、髋臼指数、头转子间距离、头颈指数和颈干角,并将测量结果与我院40例（80髋）原发性骨关节炎患者进行对比分析。结果：224髋中有22髋（9．8％）出现髋部异常改变,主要表现为髋臼软骨下骨硬化或囊变、股骨头形态不规则伴密度异常、颈干角变小。112例患者Sharp角平均37．92°、CE角平均30．26°、髋臼指数平均43．86、头转子间距离平均1．69cm、头颈指数平均1．80、颈干角平均121．8°。与骨关节炎患者相比,大骨节病组患者颈干角较小,其组间差异有统计学意义（P〈0．05）,但均在正常范围内;其余测量指标两组比较均无统计学差异。结论：成人大骨节病部分患者髋关节在影像学方面具有异常改变,主要表现为髋臼软骨下骨硬化或囊变、股骨头形态不规则伴密度异常、颈干角变小。上述影像学改变与骨关节炎患者相比无明显特异性。     

全髋关节置换术后髋臼假体外倾角的临床研究

目的　了解广医一院人工全髋关节置换术后髋臼假体外倾角的情况及外倾角大小与聚乙烯磨损的关系。 方法　选取2011年5月前广医一院骨外科THA术后126例145髋患者骨盆前后位X线片,其中男47例,女79例,年龄23~85岁,末次随访时平均年龄60.1岁。采用DR拍摄骨盆前后位照片,测量髋臼外倾角,统计外倾角≥50°及≥55°的发生率。对单侧全髋关节置换患者测量股骨头中心位移,评估髋臼外倾角与聚乙烯磨损的相关性,使用时间超过5年的内衬的线性磨损值与使用时间少于5年的内衬比较有无差异。 结果　126例145髋中61个髋的外倾角大于等于50°,百分率为42.1%（34.1%　~50.1%）,大于等于55°者32个,百分率为22.1%(15.3%~28.9%)。外倾角<50°组聚乙烯线性磨损比外倾角≥50°组轻,差异有统计学意义,P<0.001,对107个髋的髋臼外倾角与聚乙烯线性磨损值做散点图及简单线性回归分析,二次多项式曲线拟合效果较好,拟合优度（R Square）为0.697,聚乙烯线性磨损值与髋臼外倾角同向相关,回归方程为■=4.431-0.21x+0.003x2。 结论　人工全髋关节置换术后髋臼外倾角与聚乙烯线性磨损相关,手术中需要采取有效措施防止髋臼假体外倾角过大。     

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。     

保留髋臼杯骨水泥聚乙烯内衬置换的髋臼侧翻修

BACKGROUND: Although cementation of polyethylene liner into a well-fixed metal shell during the revision surgery has several advantages compared to total acetabular revision, there are some disputes about its clinical outcomes, especially regarding the re-revision rate and the prosthetic survivorship. OBJECTIVE: To evaluate the clinical outcomes and safety of cementation of polyethylene liner into a well-fixed acetabular cup in the revision after total hip arthroplasty with retained stable cup. METHODS: Between March 2012 and November 2014, nine patients underwent revision after total hip arthroplasty with cementation of polyethylene liner into a well-fixed acetabular cup. There were 1 male and 8 females, aged 43.7 years on average. The time was 9.4 years on average from the primary total hip arthroplasty to revision. Harris Hip Score and prosthesis X-ray films were compared after revision. The effects and safety of cementation of polyethylene liner into a well-fixed acetabular cup were further evaluated.  RESULTS AND CONCLUSION: Nine patients were followed up for 8-37 months. The Harris hip scores before revision was (49.54±18.28) points previously, and (84.82±10.59) points during final follow-up (t=6.377, P < 0.05). One patient had re-revision surgery because of recurrent dislocation. There were not complications in other patients, resulting in failure rate of 11%. These results indicated that polyethylene liner cementation technique is safe and effective when the well-positioned and well-fixed acetabular cup retained.