Adaptations to mass perturbations in transtibial amputees: Kinetic or kinematic invariance?

OBJECTIVE: To establish the adaptation strategy transtibial amputees use after mass perturbation of their prosthetic lower leg. DESIGN: We investigated whether the measured adaptations to mass perturbation of the lower leg in transtibial amputees can better be described as (1) a kinetic invariance strategy in which kinetics (joint torques) remain the same while kinematics (joint angles) change or (2) a kinematic invariance strategy in which kinematics remain the same while kinetics change. SETTING: A gait laboratory. PARTICIPANTS: Ten transtibial amputees. INTERVENTIONS: Five different mass conditions. MAIN OUTCOME MEASURES: Measured joint torques and angles during the swing phase in the different mass conditions. RESULTS: Mass perturbation induced more significant changes and larger effect sizes in joint torques than in joint angles. CONCLUSIONS: Transtibial amputees adapt to mass perturbation primarily by maintaining the same kinematic pattern and adjusting their joint torques, that is, they use a kinematic invariance strategy. This implies that manipulating prosthetic inertial properties does not directly influence gait kinematics and that inertial properties should be evaluated in terms of the energetic cost of the swing phase.     

Adaptations to mass perturbations in transtibial amputees: kinetic or kinematic invariance?

Selles RW, Bussmann JB, Klip LM, Speet B, Van Soest AJ, Stam HJ. Adaptations to mass perturbations in transtibial amputees: kinetic or kinematic invariance? Arch Phys Med Rehabil 2004;85:2046-52.

Objective

To establish the adaptation strategy transtibial amputees use after mass perturbation of their prosthetic lower leg.

Design

We investigated whether the measured adaptations to mass perturbation of the lower leg in transtibial amputees can better be described as (1) a kinetic invariance strategy in which kinetics (joint torques) remain the same while kinematics (joint angles) change or (2) a kinematic invariance strategy in which kinematics remain the same while kinetics change.

Setting

A gait laboratory.

Participants

Ten transtibial amputees.

Interventions

Five different mass conditions.

Main outcome measures

Measured joint torques and angles during the swing phase in the different mass conditions.

Results

Mass perturbation induced more significant changes and larger effect sizes in joint torques than in joint angles.

Conclusions

Transtibial amputees adapt to mass perturbation primarily by maintaining the same kinematic pattern and adjusting their joint torques, that is, they use a kinematic invariance strategy. This implies that manipulating prosthetic inertial properties does not directly influence gait kinematics and that inertial properties should be evaluated in terms of the energetic cost of the swing phase.     

The effect of prosthetic mass properties on the gait of transtibial amputees--a mathematical model

PURPOSE: Present models in the literature, predicting that prostheses should not be too lightweight, are not supported by empirical evidence. Recent studies suggest that these models are incorrectly based on the assumption that the swing phase is uninfluenced by muscle activity. The purpose of the present study was to introduce a new mathematical model to predict the effect of mass properties on the gait of transtibial amputees, based on experimental findings that subjects adapt to mass perturbations by maintaining the same joint kinematics. METHOD: Effect of mass perturbations on the lower leg was evaluated in terms of muscular cost and forces between stump and socket, using a linked-segment model of the swing phase. Gait analysis and anthropometric data from 10 transtibial amputees were used as model input. RESULTS: Location of perturbation strongly influenced the muscular cost. Cost generally increased after distally adding mass but decreased after proximally adding mass to the lower leg. Stump-socket interface forces always increased after mass addition. CONCLUSIONS: A new model was introduced, predicting that the weight of distally located components (e.g. foot, ankle, shoe) strongly influence the estimated muscular cost, in contrast to proximal components. A comparison with experimental literature suggests this new model better describes the experimental data than existing models.     

The effect of prosthetic mass properties on the gait of transtibial amputees—a mathematical model

Purpose:?Present models in the literature, predicting that prostheses should not be too lightweight, are not supported by empirical evidence. Recent studies suggest that these models are incorrectly based on the assumption that the swing phase is uninfluenced by muscle activity. The purpose of the present study was to introduce a new mathematical model to predict the effect of mass properties on the gait of transtibial amputees, based on experimental findings that subjects adapt to mass perturbations by maintaining the same joint kinematics.

Method:?Effect of mass perturbations on the lower leg was evaluated in terms of muscular cost and forces between stump and socket, using a linked-segment model of the swing phase. Gait analysis and anthropometric data from 10 transtibial amputees were used as model input.

Results:?Location of perturbation strongly influenced the muscular cost. Cost generally increased after distally adding mass but decreased after proximally adding mass to the lower leg. Stump?–?socket interface forces always increased after mass addition.

Conclusions:?A new model was introduced, predicting that the weight of distally located components (e.g. foot, ankle, shoe) strongly influence the estimated muscular cost, in contrast to proximal components. A comparison with experimental literature suggests this new model better describes the experimental data than existing models.     

模拟上肢截肢者走跑步态特征研究

目的：探讨上肢截肢者基本运动的步态特征与正常人步态特征的差异，进一步阐明上肢运动在人体基本运动中的作用机制。方法：实验中采用Motion analysis system红外自动跟踪捕捉系统和Kistler Force Plate进行同步运动学和动力学测试。通过对正常人的手臂进行限制约束，对上肢截肢者进行模拟实验。结果：通过对手臂约束前后对比分析发现约束前后部分步态参数存在显著差异。结论：在行走时步态参数差异较小，跑动时差异较显著；补偿运动主要发生在躯干、骨盆、摆动腿；慢走时摆臂有利于增大垂直方向的作用力，快跑时没有手臂的摆动在脚着地时向后的阻力增大。     

Vaulting quantification during level walking of transfemoral amputees

Background

Vaulting is a gait compensatory mechanism used by transfemoral amputees to assist toe clearance during the prosthetic swing phase. It is defined by a plantar flexion of the contralateral ankle during the single-limb support phase. The aim of the study is to propose a method to quantify vaulting of transfemoral amputees.

Methods

17 transfemoral amputees and 28 asymptomatic subjects participated in the data collection. Kinematics and kinetics of the whole body were recorded while subjects were walking on a level surface. Biomechanical gait analysis was focused on a reduced set of parameters linked to the contralateral ankle, the contralateral knee and the trajectory of the center of pressure. The patients were classified in two groups: with or without vaulting using video recordings. Differences between both groups and the control group were analyzed.

Findings

A higher generated ankle power was found during the single support phase of the contralateral limb of transfemoral amputees presenting vaulting. These subjects presented also a higher dissipated knee flexion power before the peak in ankle flexion power. The trajectory of the center of pressure was also modified by the vaulting.

Interpretation

Vaulting for transfemoral amputees is characterized by a propulsive plantar flexion at the contralateral ankle. Quantifying the ankle flexion power during the contralateral single support phase will help in understanding vaulting.     

The initiation of gait in lower limb amputees: some related data

The initiation of gait, from balanced standing position to the toe-off of the stance leg, was analyzed in 8 unilateral above-knee (AK) and 10 unilateral below-knee (BK) males amputees. Thirty-one parameters were measured, including ground-foot forces and the movements and timing of hip, knee, and ankle joints. The significant changes from the normal pattern of initiation of gait found in the AK and BK amputees, as well as significant changes between the two amputees groups themselves, are described. The amputees were divided into two subgroups: those who start walking with their prosthesis and those starting with their normal leg. The two groups were compared statistically for each amputation level and all were compared to a normal subjects group. Differences relating to the choice of the swing leg were found. The findings are reported as part of a future databank.     

核心稳定性训练对脑卒中偏瘫患者步态时空参数和对称性参数的影响

摘要 目的：应用步态分析,观察核心稳定性训练对脑卒中偏瘫患者步态时空参数和对称性参数的影响。 方法：选取脑卒中偏瘫患者60例,按随机数字表法将其分为观察组及对照组,每组30例。两组均进行常规治疗,观察组在此基础上给予核心稳定性训练。分别于治疗前和治疗6周后使用三维步态分析仪器检测并获得两组患者的步态参数。 结果：治疗6周后,两组患者步频、步幅、步速、患侧摆动相和健侧摆动相均较治疗前明显提高（P<0.01）,步宽、步态周期、双支撑相、患侧支撑相、健侧支撑相、步长偏差、健侧患侧支撑相比值和患侧健侧摆动相比值均较治疗前显著减小（P<0.01）。组间比较显示,观察组患者的步频、步幅、步速、步宽、步态周期、双支撑相、健侧支撑相、健侧摆动相、步长偏差、健侧患侧支撑相比值和患侧健侧摆动相比值改善均明显优于对照组（P<0.05或0.01）。 结论：核心稳定性训练能有效改善脑卒中偏瘫患者步态时空参数和对称性参数,提高脑卒中偏瘫患者的步行功能和步态的对称性。     

三维步态分析在截肢患者康复中的应用

采用Vicon三维步态分析系统对健康人和穿戴假肢的下肢截肢患者进行步态分析,表明该系统可提供运动学参数和生物力学参数的变化,由此分析假肢穿戴者与健康人各关节运动的差异。将三维步态分析应用于截肢患者康复方面是切实可行的。     

Effects of diabetic peripheral neuropathy on gait in vascular trans-tibial amputees

BackgroundPatients with diabetes often develop diabetic peripheral neuropathy, which is a distal symmetric polyneuropathy, so foot function on the non-amputated side is expected to affect gait in vascular trans-tibial amputees. However, there is little information on the kinematics and kinetics of gait or the effects of diabetic peripheral neuropathy in vascular trans-tibial amputees. This study aimed to clarify these effects, including the biomechanics of the ankle on the non-amputated side.MethodsParticipants were 10 vascular trans-tibial amputees with diabetic peripheral neuropathy (group V) and 8 traumatic trans-tibial amputees (group T). Each subject's gait was analyzed at a self-selected speed using a three-dimensional motion analyzer and force plates.FindingsAnkle plantarflexion angle, heel elevation angle, and peak and impulse of anterior ground reaction force were smaller on the non-amputated side during pre-swing in group V than in group T. Center of gravity during pre-swing on the non-amputated side was lower in group V than in group T. Hip extension torque during loading response on the prosthetic side was greater in group V than in group T.InterpretationThese findings suggest that the biomechanical function of the ankle on the non-amputated side during pre-swing is poorer in vascular trans-tibial amputees with DPN than in traumatic trans-tibial amputees; the height of the center of gravity could not be maintained during this phase in vascular trans-tibial amputees with diabetic peripheral neuropathy. The hip joint on the prosthetic side compensated for this diminished function at the ankle during loading response.     

Gait asymmetry of transfemoral amputees using mechanical and microprocessor-controlled prosthetic knees

Background

Amputees walk with an asymmetrical gait, which may lead to future musculoskeletal degenerative changes. The purpose of this study was to compare the gait asymmetry of active transfemoral amputees while using a passive mechanical knee joint or a microprocessor-controlled knee joint.

Methods

Objective 3D gait measurements were obtained in 15 subjects (12 men and 3 women; age 42, range 26–57). Research participants were longtime users of a mechanical prosthesis (mean 20 years, range 3–36 years). Joint symmetry was calculated using a novel method that includes the entire waveform throughout the gait cycle.

Findings

There was no significant difference in hip, knee and ankle kinematics symmetry when using the different knee prostheses. In contrast, the results demonstrated a significant improvement in lower extremity joint kinetics symmetry when using the microprocessor-controlled knee.

Interpretation

Use of the microprocessor-controlled knee joint resulted in improved gait symmetry. These improvements may lead to a reduction in the degenerative musculoskeletal changes often experienced by amputees.     

External loading alters lower extremity kinetics,kinematics, and muscle activity in a distribution-specific manner during the transition from stair descent to level walking

BackgroundExcess body mass is thought to be a major cause of altered biomechanics in obesity, but the effects of body mass distribution in biomechanics during daily living tasks are unknown. The purpose of this study was to determine how increasing body mass centrally and peripherally affects lower extremity kinematics, kinetics, and muscle activation when transitioning from stair descent to level gait.MethodsFifteen normal weight volunteers descended a staircase at a self-selected pace under unloaded, centrally loaded, and peripherally loaded conditions. Spatial-temporal gait characteristics and lower extremity joint kinematics, kinetics, and mean electromyography amplitude were calculated using 3D motion analysis.FindingsBoth central and peripheral loading reduced gait velocity. Peripheral loading increased time spent in stance phase, increased step width, and reduced step length. At the hip joint, peripheral loading reduced peak hip extension and adduction angle. Conversely, central loading reduced peak hip flexor moment. Both central and peripheral loading increased peak knee flexion angle, but only peripheral loading increased peak knee extensor moment. Central and peripheral loading increased mean electromyography amplitude of the medial gastrocnemius, but only peripheral loading increased mean electromyography amplitude of the semitendinosus and the vastus medialis.InterpretationIncreasing mass centrally and peripherally differently affects spatial-temporal gait characteristics and lower extremity joint kinematics, kinetics, and electromyography when transitioning from stair descent to level gait. Body mass distribution may be an important factor for obesity-induced biomechanical alterations and should be considered when developing biomechanical models of obesity.     

The influence of energy storage and return foot stiffness on walking mechanics and muscle activity in below-knee amputees

Background

Below-knee amputees commonly experience asymmetrical gait patterns and develop comorbidities in their intact and residual legs. Carbon fiber prosthetic feet have been developed to minimize these asymmetries by utilizing elastic energy storage and return to provide body support, forward propulsion and leg swing initiation. However, how prosthetic foot stiffness influences walking characteristics is not well-understood. The purpose of this study was to identify the influence of foot stiffness on kinematics, kinetics, muscle activity, prosthetic energy storage and return, and mechanical efficiency during amputee walking.

Methods

A comprehensive biomechanical analysis was performed on 12 unilateral below-knee amputees. Subjects walked overground at 1.2 m/s with three prosthetic feet of varying keel and heel stiffness levels, which were created using additive manufacturing.

Findings

As stiffness decreased, peak residual and intact leg ankle angles and residual leg knee flexion angle increased. The residual and intact leg braking ground reaction forces and knee extensor moments, residual leg vastus and gluteus medius activity, and intact leg vastus and rectus femoris activity also increased. The second vertical ground reaction force peak and hamstring activity in the residual leg and first vertical ground reaction force peak in the intact leg decreased. In addition, prosthetic energy storage and return increased and mechanical efficiency decreased as stiffness decreased.

Interpretation

Decreasing foot stiffness can increase prosthesis range of motion, mid-stance energy storage and late-stance energy return, but the net contributions to forward propulsion and swing initiation may be limited as additional muscle activity to provide body support becomes necessary.     

单侧小腿截肢患者穿假肢后的步态运动学参数研究

目的 采用计算机辅助康复环境(CAREN)步态评估系统分析单侧小腿截肢患者穿假肢后的步态运动学参数,并分析其产生差异的原因。 方法 选取单侧小腿中段截肢但均装配假肢的受试者9例设为假肢组,同期选择健全受试者11例设为标准组,通过CAREN步态评估系统对2组受试者的步态运动学参数进行收集、处理、分析,并根据分析报告阐明产生差异原因。 结果 假肢组步态时相性指数为(0.88±0.04),其假肢侧的步长、支撑期百分比、髋关节支撑期最大伸展角度、膝关节支撑期最大屈曲角度、踝关节足跟着地背屈角度、踝关节支撑期最大背屈角度、踝关节支撑期最大跖屈角度与健侧比较,差异均有统计学意义(P<0.05）。假肢组假肢侧的步行速度、步态周期、跨步长、支撑期百分比、髋关节足跟落地屈髋角度、髋关节支撑期最大伸展角度、髋关节支撑期最大屈曲角度、膝关节足跟着地屈膝角度、踝关节足跟着地背屈角度、踝关节支撑期最大跖屈角度、踝关节支撑期最大背屈角度与标准组双侧均值比较,差异均有统计学意义(P<0.05）。 结论 单侧小腿截肢者穿戴假肢后步态时相对称性为（0.88±0.04）,假肢侧踝关节运动学参数显著弱于自身健侧,其时空与运动学参数也显著弱于健全人。     

Identifying the time of occurrence of a hamstring strain injury during treadmill running: a case study

BACKGROUND: While hamstring strain injuries are common during sprinting, the mechanisms of injury are not well understood. In this study, we analyzed the running kinematics of an athlete obtained at the time of an acute hamstring strain injury. The purpose was to identify the period of the gait cycle during which the hamstring was likely injured, as well as to characterize the biomechanical conditions associated with the injury. METHODS: A male professional skier injured his right biceps femoris long head while running at 5.36 m/s on a treadmill with a 15% incline. Whole body kinematics were recorded at the time of injury. A linear periodic prediction model was used to determine when individual marker trajectories deviated from a cyclic periodic pattern, indicating the mechanical response to injury. A three-dimensional musculoskeletal model was used to compute joint angles and hamstring musculotendon lengths during the injurious running trial. These data were used with estimates of neuromuscular latencies and electromechanical delays to identify the most likely time period of injury. FINDINGS: Based upon the earliest indications in marker trajectories, a 130 ms period during the late swing phase of the gait cycle was identified as the period of injury. During this period, the biceps femoris reached a peak musculotendon length that was estimated to be 12% beyond the length seen in an upright posture and exceeded the normalized peak length of the medial hamstrings. INTERPRETATION: This case provides quantitative data suggesting that the biceps femoris muscle is susceptible to an lengthening contraction injury during the late swing phase of the running gait cycle.     

Control of interjoint coordination during the swing phase of normal gait at different speeds

Background  

It has been suggested that the control of unconstrained movements is simplified via the imposition of a kinetic constraint that produces dynamic torques at each moving joint such that they are a linear function of a single motor command. The linear relationship between dynamic torques at each joint has been demonstrated for multijoint upper limb movements. The purpose of the current study was to test the applicability of such a control scheme to the unconstrained portion of the gait cycle – the swing phase.     

六连杆假肢膝关节优化设计

目的：假肢膝关节的设计对于膝上截肢者的安全与步态关系重大。为了改善膝上假肢穿戴者的步态,设计了六连杆假肢膝关节。方法：采用最优化设计使摆动相步态尽可能逼近正常步态;在结构设计上利用瞬停节特性使膝关节在支撑期有自锁功能并具有很强的抗干扰能力。结果：计算机仿真为踝关节运动轨迹均方误差不超过１．９６％。结论：该膝关节假肢在支撑期保持稳定性的同时,在摆动期内膝、踝关节运动轨迹,以及大小腿的角度变化关系相对于正常人具有很好的逼近效果,能够有效改善患者步态。     

Asymétries chronométriques, cinétiques et cinématiques de l''initiation de la marche chez un sujet hémiplégique

OBJECTIVE: To investigate the temporal, kinetic and kinematic asymmetry of gait initiation in one subject with hemiplegia with an equinus varus foot. MATERIAL AND METHODS: A kinetic analysis with two AMTI force plates and a kinematic analysis with an ELITE optoelectronic system of gait initiation were performed in one subject with hemiplegia. RESULTS: The duration of the gait initiation phases was asymmetrical. The monopodal phase was shorter when the affected lower limb was supporting than when the healthy one was supporting. The propulsion resulted from the force exerted on the healthy lower limb. The distribution of body weight on the lower limbs was asymmetrical. Body weight support was more important on the healthy side than on the affected side. Maximal extension of the ankle on the hemiplegic side occurred during the swing phase. Ground clearance was increased by elevating the knee higher on the affected side than on the healthy side during the swing phase. Initial contact with the floor was performed with the foot flat on the affected side. CONCLUSION: This preliminary study has shown that gait initiation in one subject with hemiplegia was asymmetrical in kinetics and kinematics. The results concerning kinematics have not been reported previously for gait initiation in subjects with hemiplegia. The study of gait initiation should allow for better understanding postural and movement control strategies developed by patients with hemiplegia.     

The effect of voluntary toe-walking on body propulsion

OBJECTIVE: We studied the kinetics of toe-walking by comparing the linear power flow from the leg to the upper-body. Our hypothesis was that toe-walking has no inherent biomechanical disadvantage with regard to upper-body propulsion and support. DESIGN: We studied healthy subjects capable of both heel-toe gait and voluntary toe-walking so that the two forms of gait could be directly compared. BACKGROUND: Ankle joint power at terminal stance is significantly reduced in toe-walking, which has been presumed to imply impaired propulsion and support. However, linear power analysis may be more appropriate for assessing this aspect of gait. METHODS: We compared the normal heel-toe gait of 10 healthy young adult subjects to their voluntary toe-walking gait using gait laboratory kinematic and kinetic data. Inverse dynamic analysis was performed to determine the net joint moments and joint linear powers. The contribution of each joint moment to the total hip linear power was also determined. RESULTS: Hip linear power for toe-walking was similar to that of heel-toe gait with no significant differences in the linear power peaks. The stance phase contributions of the knee and ankle moments were significantly altered in toe-walking only in early stance. CONCLUSIONS: Toe-walking does not inherently impair propulsion and support. RELEVANCE: Linear power analysis is a useful adjunct to clinical gait analysis, complementing joint power analysis. Understanding the inherent kinetics of toe-walking will enhance our analysis of pathological toe-walking and improve treatment design.     

Robotic gait trainer in water: development of an underwater gait-training orthosis

Purpose. To develop a robotic gait trainer that can be used in water (RGTW) and achieve repetitive physiological gait patterns to improve the movement dysfunctions.

Method. The RGTW is a hip-knee-ankle-foot orthosis with pneumatic actuators; the control software was developed on the basis of the angular motions of the hip and knee joint of a healthy subject as he walked in water. Three-dimensional motions and electromyographic (EMG) activities were recorded in nine healthy subjects to evaluate the efficacy of using the RGTW while walking on a treadmill in water.

Results. The device could preserve the angular displacement patterns of the hip and knee and foot trajectories under all experimental conditions. The tibialis anterior EMG activities in the late swing phase and the biceps femoris throughout the stance phase were reduced whose joint torques were assisted by the RGTW while walking on a treadmill in water.

Conclusion. Using the RGTW could expect not only the effect of the hydrotherapy but also the standard treadmill gait training, in particular, and may be particularly effective for treating individuals with hip joint movement dysfunction.