Variations of relative anteversion of the femoral neck during walking

Summary Based on the geometric model developed by Netter [11], we determined the different positions of the femoral neck during monopodal support in walking in relation to a fixed frontal plane of reference (relative anteversion). This relative anteversion ranges on average from 24° of retroversion at the beginning of support to 15° of anterversion at the end if loading. We then studied the relations possibly existing between relative anteversion and acetabular orientation on the one hand, and the orientation of the resultant of the articular stresses on the other (both being variables during monopodal support in walking). The results showed that relative anteversion is well correlated with variations of position of the acetabulum since, at most, the deviation between the respective axes did not exceed the anatomic deviation due to absolute anteversion of the femoral neck and acetabulum. Lastly, analysis of the relations obtained with the orientation of the resultant of the articular stresses allowed a better comprehension of the functional distribution of forces.

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Variations de l'antéversion relative du col fémoral au cours de la marche

Résumé Nous inspirant de la modélisation géométrique développée par R. Netter dans sa thèse, nous avons déterminé les différentes positions du col fémoral au cours de l'appui monopodal de la marche par rapport à un plan frontal fixe de référence (antéversion relative). Cette «antéversion relative» s'échelonne en moyenne de 24° de rétroversion en début d'appui à 15° d'antéversion en fin d'appui. Nous avons alors étudié les relations pouvant exister entre l'antéversion relative et l'orientation de l'acétabulum, d'une part, et, d'autre part, l'orientation de la résultante des sollicitations articulaires (toutes deux variables au cours de l'appui monopodal de la marche). Les résultats nous ont montré que l'antéversion relative est bien corrélée aux variations de position de l'acétabulum puisque, au maximum, l'écart entre leurs axes respectifs ne dépasse pas l'écart anatomique du à l'antéversion absolue du col et de l'acétabulum. Enfin, l'analyse des rapports existant avec l'orientation de la résultante des sollicitations articulaires nous permet de mieux entrevoir la répartition fonctionnelle des contraintes.

     

Variations of relative anteversion of the femoral neck during walking

Based on the geometric model developed by Netter [11], we determined the different positions of the femoral neck during monopodal support in walking in relation to a fixed frontal plane of reference (relative anteversion). This “relative anteversion” ranges on average from 24° of retroversion at the beginning of support to 15° of anterversion at the end if loading. We then studied the relations possibly existing between relative anteversion and acetabular orientation on the one hand, and the orientation of the resultant of the articular stresses on the other (both being variables during monopodal support in walking). The results showed that relative anteversion is well correlated with variations of position of the acetabulum since, at most, the deviation between the respective axes did not exceed the anatomic deviation due to absolute anteversion of the femoral neck and acetabulum. Lastly, analysis of the relations obtained with the orientation of the resultant of the articular stresses allowed a better comprehension of the functional distribution of forces.     

Angular momentum synergies during walking

We studied the coordination of body segments during treadmill walking. Specifically, we used the uncontrolled manifold hypothesis framework to quantify the segmental angular momenta (SAM) synergies that stabilize (i.e., reduce the across trials variability) the whole body angular momentum (WBAM). Seven male subjects were asked to walk over a treadmill at their comfortable walking speed. A 17-segment model, fitted to the subject’s anthropometry, was used to reconstruct their kinematics and to compute the SAM and WBAM in three dimensions. A principal component analysis was used to represent the 17 SAM by the magnitudes of the first five principal components. An index of synergy (ΔV) was used to quantify the co-variations of these principal components with respect to their effect on the WBAM. Positive values of ΔV were observed in the sagittal plane during the swing phase. They reflected the synergies among the SAM that stabilized (i.e., made reproducible from stride to stride) the WBAM. Negative values of ΔV were observed in both frontal and sagittal plane during the double support phase. They were interpreted as “anti-synergies”, i.e., a particular organization of the SAM used to adjust the WBAM. Based on these results, we demonstrated that the WBAM is a variable whose value is regulated by the CNS during walking activities, and that the nature of the WBAM control changed between swing phase and double support phase. These results can be linked with humanoid gait controls presently employed in robotics.     

The effect of load carriage on movement kinematics and respiratory parameters in children during walking

The objective of this study was to investigate the influence of different backpack weights on trunk kinematics and respiratory parameters during walking in 10-year-old children. Fifteen boys with a mean age of 10.31 (0.26) years were selected from a primary school to participate in four walking trials on a treadmill: one with a backpack of 0% of body mass, and three whilst carrying backpacks that weighed 10%, 15%, and 20% of the child's body mass. The walking speed was set at 1.1 m s^-1 for 20 min duration. The walking movement was recorded on video and analysed in two dimensions. The breathing frequency, tidal volume, and respiratory muscles activity were measured with a cardiopulmonary system (Oxycon Champion, Jaeger) and a respiratory inductance plethysmograph (TR-601T, Nihon Kohden, Japan). A repeated ANOVA and Pearson correlation analysis were used to examine any significant differences in the measured parameters when comparing the different loads. The results showed a significant positive linear relationship between load weight, trunk inclination angle, and breathing frequency (P<0.01). Walking for 20 min, carrying a load that weighed 20% of body mass induced a significantly increased trunk inclination angle. A significant increase in ventilation during walking with a backpack of 15% and 20% of bodymass was associated with a more rapid breathing frequency. Walking with a backpack of 10% body mass did not significantly change trunk posture or respiratory parameters. However, the results suggested that walking with a backpack of greater than 10% body mass induced significant changes in trunk posture and respiratory parameters in 10-year-old children.     

A simulation model that predicts handling forces required to reposition surgical lights

Introduction: High handling forces of surgical lighting systems limit their usability. To make improvements to the mechanical design of the system the behaviour of the system should be understood. Therefore, this study presents a model that predicts handling forces of surgical lighting systems. Methods: Geometry and joint friction torques of a real lighting system were measured and implemented in a validated force model. Mean, standard deviation within the spatial region, minimum force and maximum force were computed for three different regions of the working area. Results: The mean (standard deviation within the spatial region) forces were 129 (106) N in the centre region, and 61 (14) N and 60 (17) N in more off-centre regions. Conclusion: The simulation results showed high handling forces in the central region, explaining the observed repositioning patterns of the surgical light during surgery. The model can also be used to compare different lighting systems, or to evaluate the effect of design changes.     

股骨头表面置换后股骨近段的生物力学研究

目的探讨股骨头表面置换术对股骨近段生物力学性能的影响。方法集8具青年正常新鲜髋关节标本,建立静止单腿站立位股骨头受力模型,WD-5生物力学测试机测试1000N载荷下股骨头表面置换前后的载荷-应变关系、近段股骨应力分布、刚度和扭转力学性能。结果载荷为1000N时,置换前后的平均应变、最大平均应力、最大平均位移、刚度等指标的测试结果,经统计学处理均无显著性差异(P>0.05)。表面置换前后最大扭矩值相差19%,有显著差异(P<0.05)。结论表面置换能有效维持近段股骨的正常应力传递,从而能有效保留近段股骨的骨量,为日后翻修提供良好条件。表面置换是适用于年轻患者的过渡性手术。     

隐形矫正器作用下牙颌组织的生物力学实验分析

目的研究分析牙颌组织在隐形矫治器作用下的生物力学特性,以及隐形矫正器的作用力系和作用效果。方法建立包括牙齿、牙周膜和牙槽骨在内的上颌三维有限元模型。根据正畸过程中牙齿的典型移动情况,设计多个矫正方案模拟。在此基础上分析在隐形矫治器作用下的牙颌组织的应力和应变情况。同时与传统固定矫治器的相关分析结果进行对比。结果隐形矫正器与传统的固定矫治器作用下牙颌组织的应力应变分布相近,且应力变化趋势相似。结论通过合理设计隐形矫治器,可以实现畸形的矫正及满足矫正过程中患者对美观的要求。     

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.     

基于HHT人步行状态髋关节角度信号的分析方法

目的 提出一种基于希尔伯特-黄变换（Hilbert-Huang transform,HHT）分析人步行状态髋关节角度信号的方法 ,并验证其可行性。方法 首先,利用加速度传感器与陀螺仪组成的髋关节角度测量平台,测量健康人步行状态髋关节角度。其次,对此信号进行集合经验模态分解（ensemble empirical mode decomposition, EEMD）,得到各本征模态函数（intrinsic mode functions, IMF）,再对不同尺度的模态函数进行分析与组合。最后,对原信号进行Hilbert谱分析。结果 得到反映运动模式的特征信号以及髋关节旋转轨迹所表示的步态特征。Hilbert谱显示出主运动模式内的波内频率调制现象与步频特征。结论 此方法 适用于步态疾病患者的康复与治疗,可以有效地将髋关节角度信号不同频率尺度的特征信号进行分解,实现中心修正与滤波,达到自适应分析患者步态信号的目的 。     

模拟全髋关节置换后股骨假体的稳定性

背景：国内外关于髋关节置换后股骨的压缩力学实验研究较多,因此研究髋关节置换后股骨的扭矩、扭转角、载荷-位移关系非常重要。对比分析传统型假体和解剖型假体的压缩、扭转力学特性,对于髋关节置换及人工假体的稳定性研究具有重要意义。 目的：通过模拟髋关节置换后股骨的轴向压缩和扭转实验,对比分析传统型和解剖型人工假体的稳定性,为临床提供生物力学参数。 方法：取股骨左右侧标本共12个,其中左侧6个标本保留股骨颈作为解剖型钛合金人工关节假体组,右侧6个标本去除股骨颈作为传统型钴铬钼人工关节假体组。分别将两组标本置于电子万能试验机工作台上,以     5 mm/min的实验速度对标本施加压应力,读取20,40,60,80,100 N时所对应的位移值。之后取两组标本,将标本两端置于扭转试验机夹头内,以1 (°)/s的实验速度对标本施加扭矩,读取5,10,15,20 N•m扭矩时所对应的扭转角值。 结果与结论：在100 N外力作用下,传统型假体位移为(2.03±0.06) mm,解剖型假体位移为(1.83±0.05) mm;在20 N•m扭矩作用下,传统型假体扭转角为(21.7±0.7)°,解剖型假体扭转角为(13.2±0.4)°。解剖型假体在100 N作用下的位移和在20 N•m扭矩作用下的扭转角均小于传统型假体组,差异有显著性意义(P < 0.05)。提示解剖型假体和传统型假体具有不同的压缩和扭转力学特性,解剖型假体置入股骨后具有较好的稳定性。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     

Finite element contact analysis of the hip joint

The hip joint plays an important role in the musculoskeletal system; however, current knowledge of the mechanics of the hip joint, especially with regard to the distribution of stress, remains limited. In experimental research, difficulties arise during reproduction of physiological conditions of daily activities and practicable measurement of locations inside the hip joint without violating the physiological environment. On the other hand, numerical approaches, such as finite element analysis, have become useful tools in the field of biomechanics. In finite element contact analysis of the hip joint, due to discretization of contact surfaces, computational instability might occur when the contact nodes move near the edges of the contact elements. In this study, to overcome this problem, a contact smoothing approach was introduced by applying Gregory patches. Contact analysis of the hip joint was then performed for three representative daily activities; i.e., walking, rising up from a chair and knee bending. The effectiveness of the adopted smoothing approach was verified by comparing the results with those obtained experimentally. The distribution and history of contact stress, which have heretofore been scarcely reported, were also obtained and the implications associated with osteoarthritis were discussed.     

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。     

Assessment of spatio-temporal parameters during unconstrained walking

This paper presents an analysis of spatio-temporal gait parameters during overground walking based upon a method that needs only lower trunk accelerations. Twenty-six healthy young subjects and 15 healthy elderly subjects participated in an experiment where overground walking was studied at different speeds. Accelerations of the lower trunk were measured by a tri-axial accelerometer connected to a portable data logger carried on the body. An analysis of trunk acceleration data produced temporal gait parameters (duration of subsequent stride cycles and left/right steps) and convincing estimations of spatial parameters (step length and walking speed). Typical differences in spatio-temporal gait parameters between young and elderly subjects could be demonstrated, i.e. a limited range of walking speeds, smaller step lengths, and a somewhat higher variability of temporal parameters in elderly subjects. It is concluded from these results that essential spatio-temporal gait parameters can be determined during overground walking using only one tri-axial accelerometer. The method is easy-to-use and does not interfere with regular walking patterns. Both the accelerometer and the data logger can be miniaturised to one small instrument that can be carried on the trunk during hours of walking. Thus, the method can easily be incorporated in current activity monitors so that 24-h monitoring of postures and activities can be combined with assessment of gait characteristics during these monitoring periods. In addition, the presented method can be a basis for more sophisticated gait analyses during overground walking, e.g. an analysis of kinematic signals or muscle activity within subsequent stride cycles.     

臀肌挛缩症患者三维步态特征分析

目的：探讨臀肌挛缩症患者步态的功能量化指标为该疾病的诊断提供参考与依据。方法：2011年8月-2011年11月,选取臀肌挛缩症患者16例作为研究组,同期选取健康自愿者16例作为对照组,应用三维步态系统对两组进行三维步态对比分析。结果：①步态周期时间参数：研究组在常速、快速行走时步态周期较对照组明显延长（P〈0．01）,步幅、步速较对照组均明显减小（P〈0．01）。②下肢关节角度特征：与对照组比较,研究组在常速、快速行走时髋关节摆动期最大屈曲角度及研究组快速行走时髋关节屈伸角度变化范围均减小（P〈0．05）;研究组常速、快速行走时膝关节冠状面角度变化范围均增大（P〈0．05）,而膝关节支撑相最大屈曲角度和膝关节屈伸角度范围均减小（P〈0．01）;研究组常速行走时重心左、右位移增大（P〈0．05）,快速行走时重心上、下位移减小（P〈0．05）。结论：应用三维步态分析系统对臀肌挛缩症患者进行功能量化评价,可以更为准确地观察臀肌挛缩症患者步态的生物力学变化,为患者的诊断提供了参考和依据。     

Lower-limb vertical groundreaction forces during crutch walking

‘Physics in medical ultrasoun’ organised under the auspices of the Hospital Physicists Association and the British Medical Ultrasound Society was held on 13-14th April 1981 in Durham.     

正走和倒走的膝关节生物力学特征比较

目的 比较正走和倒走两种不同行走模式时膝关节的生物力学特征。方法 采用三维运动捕捉系统Vicon T40和测力台AMTI OR6-7采集并比较13名健康青年男性志愿者正走和倒走时的时间、空间、运动学和动力学参数。结果 与正走相比,倒走时的步速、步频和步幅均显著减小,跨步周期和支撑相所占百分比显著增加;在矢状面上,倒走时膝关节活动度、最大屈伸力矩较正走小;在冠状面上,倒走时膝关节内翻外展活动范围也较正走小,内翻力矩峰值在支撑早期较正走小,但在支撑晚期较正走大;地面反作用力在支撑早期较正走大,但在支撑晚期较正走小。结论 倒走和正走膝关节生物力学特征差异明显。与正走相比倒走在支撑相早期能减轻膝关节内侧间室的负荷,而倒走在支撑相晚期对膝关节负荷的影响则尚须进一步研究。     

Uncontrolled manifold analysis of segmental angle variability during walking: preadolescents with and without Down syndrome

The uncontrolled manifold (UCM) approach allows us to address issues concerning the nature of variability. In this study we applied the UCM analysis to gait and to a population known for exhibiting high levels of performance variability, Down syndrome (DS). We wanted to determine if preadolescents (ages between 8 and 10) with DS partition goal-equivalent variability (UCM_‖) and non-goal equivalent variability differently than peers with typical development (TD) and whether treadmill practice would result in utilizing greater amounts of functional, task-specific variability to accomplish the task goal. We also wanted to determine how variance is structured with respect to two important performance variables: center of mass (COM) and head trajectory at one specific event (i.e., heel contact) for both groups during gait. Preadolescents with and without DS walked on a treadmill below, at, and above their preferred overground speed. We tested both groups before and after four visits of treadmill practice. We found that children with DS partition more UCM_‖ variance than children with TD across all speeds and both pre and post practice. The results also suggest that more segmental configuration variance was structured such that less motion of COM than head position was exhibited at heel contact. Overall, we believe children with DS are employing a different control strategy to compensate for their inherent limitations by exploiting that variability that corresponds to successfully performing the task.     

Grip forces exerted against stationary held objects during gravity changes

 In the present study, grip forces exerted against a stationary held object were recorded during parabolic flights. Such flight maneuvers induce changes of gravity with two periods of hypergravity, associated with a doubling of normal terrestrial gravity, and a 20 s period of microgravity. Accordingly, the object’s weight changed from being twice as heavy as normally experienced and weightless. Grip-force recordings demonstrated that force control was seriously disturbed only during the first experience of hyper- and microgravity, with the grip forces being exceedingly high and yielding irregular fluctuations. Thereafter, however, grip force traces were smooth, the force level was scaled to the object’s weight under normal and high-G conditions, and the grip force changed in parallel with the weight during the transitions between hyper- and microgravity. In addition, during weightlessness, when virtually no force was necessary to stabilize the object, a low force was established, which obviously represented a reasonable safety margin for preventing possible perturbations. Thus, all relevant aspects of grip-force control observed under normal gravity conditions were preserved during gravity changes induced by parabolic flights. Hence, grip-force control mechanisms were able to cope with hyper- and microgravity, either by incorporating relevant receptor signals, such as those originating from cutaneous mechanoreceptors, or by adequately including perceived gravity signals into control programs. However, the adaptation to the uncommon gravity conditions was not complete following the first experience; finer tuning of the control system to both hyper- and microgravity continued over the measurement interval, presumably with a longer observation period being necessary before a stable performance can be reached. Received: 23 April 1998 / Accepted: 20 December 1998     

全髋关节置换假体位置的确定方法及生物力学特性

BACKGROUND: During total hip arthroplasty, it is difficult to accurately determine the exact orientation of the pelvis. Pelvic position is prone to change during treatment. After prosthesis implantation, angle deviation easily occurs. The surgeon is difficult to accurately determine the position and orientation of the prosthesis.