The effects of added prosthetic mass on physiologic responses and stride frequency during multiple speeds of walking in persons with transtibial amputation

OBJECTIVES: To determine the effect of 3 prosthetic mass conditions on selected physiologic responses during multiple speed treadmill walking in persons with transtibial amputation. DESIGN: A repeated-measures design for 3 prosthetic mass conditions and 5 walking speeds. SETTING: University research laboratory. PARTICIPANTS: Eight ambulatory men with unilateral traumatic transtibial amputation. INTERVENTIONS: The 3 prosthetic mass conditions were 60%, 80%, and 100% of the estimated intact limb below-knee mass. The multiple-speed treadmill walking test (4min at each speed: 54, 67, 80, 94, 107m/min) was performed on an instrumented treadmill according to randomly assigned mass conditions. MAIN OUTCOME MEASURES: Oxygen consumption, gait efficiency, relative exercise intensity (percentage of age-predicted maximal heart rate), and stride frequency. RESULTS: Prosthetic mass did not significantly alter oxygen consumption or gait efficiency (P>.05). From the 60% to the 100% prosthetic mass conditions, relative exercise intensity significantly increased and stride frequency significantly decreased (P<.05). CONCLUSIONS: A heavier prosthesis (up to 100% of estimated intact limb below-knee mass) did not significantly increase the energy costs of walking for the 5 speeds examined. Further study of gait symmetry with the use of a heavier prosthesis is warranted.     

A comparative study of conventional and energy-storing prosthetic feet in high-functioning transfemoral amputees

OBJECTIVE: To compare the results of gait analysis, timed walking tests, and socket comfort for transfemoral amputees wearing initially a Multiflex conventional prosthetic foot and then a Vari-Flex energy-storing prosthetic foot. DESIGN: Experimental crossover trial. SETTING: A regional prosthetic and amputee rehabilitation tertiary referral center in a teaching hospital. PARTICIPANTS: Six established unilateral transfemoral prosthetic users. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait analysis, a timed walking test, and a Prosthetic Socket Fit Comfort Score for each amputee wearing the Multiflex foot and then repeated wearing the Vari-Flex foot. RESULTS: Wearing the Vari-Flex foot, our subjects walked faster in the gait lab (1.38 +/- 0.13 m/s, P < .001) and took more equal step lengths at fast speed (1.063 +/- 0.05, P < .05). They also had greater peak ankle dorsiflexion at push-off on the prosthetic side (18.3 degrees +/-4.73 degrees, P<.001) and 3 times as much power from the prosthetic ankle at push-off (1.13 +/- 0.22 W/kg, P < .001). There were no significant changes in temporal symmetry or loading of the prosthetic limb, in the timed walking test with each foot, or in the comfort score. CONCLUSIONS: A transfemoral amputee who wears an energy-storing foot can have a more symmetric gait with regard to some measures of spatial symmetry, kinetics, and kinematics than one who wears a conventional foot. However, in this study important aspects such as more symmetric loading and comfort did not differ significantly between the 2 foot types.     

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.     

Trans-tibial amputee gait adaptations as a result of prosthetic inertial manipulation

Purpose : To establish through gait analysis how changing the mass at the distal end of an in-house, custom-made trans-tibial dynamic elastic response prosthetic limb altered selected gait variables. Including; walking velocity, cadence, single support and hip power for a single amputee. Method : A before-after single-subject research design was used with two interventions. A 3-dimensional gait analysis was conducted to analyse the effect on selected gait variables. The mass and moment of inertia of the prosthesis were altered by inserting wedges of different materials. Results : Altering the mass had little effect on the cadence, single support or the velocity. Both the affected and intact limb hip pull-off power at terminal stance was increased, although the effect was greater for the affected limb than for the intact limb. The affected limb hip power at initial contact did not alter in a manner directly related to the mass. Conclusions : Altering the mass had an inconsistent effect on the gait parameters tested. The subject volunteered that he preferred the prosthesis of the middle mass.     

Influence of rotators on the kinematic adaptations in stubby prosthetic gait

We report on the results of gait analysis in a patient with bilateral knee disarticulation amputations who used short nonarticulated prosthetic limbs (stubbies) to meet his ambulation needs over an extended period. To compensate for the loss of knee and ankle articulations, exaggerated pelvic obliquity (hip hiking), transverse pelvic rotation, and hip abduction were needed to ensure limb clearance and a functional step length. The addition of rotators to the prostheses improved gait velocity and reduced the perceived exertion of walking by favorably altering center of mass energetics.     

Trans-tibial amputee gait adaptations as a result of prosthetic inertial manipulation

Purpose: To establish through gait analysis how changing the mass at the distal end of an in-house, custom-made trans-tibial dynamic elastic response prosthetic limb altered selected gait variables. Including; walking velocity, cadence, single support and hip power for a single amputee. Method: A before-after single-subject research design was used with two interventions. A 3-dimensional gait analysis was conducted to analyse the effect on selected gait variables. The mass and moment of inertia of the prosthesis were altered by inserting wedges of different materials. Results: Altering the mass had little effect on the cadence, single support or the velocity. Both the affected and intact limb hip pull-off power at terminal stance was increased, although the effect was greater for the affected limb than for the intact limb. The affected limb hip power at initial contact did not alter in a manner directly related to the mass. Conclusions: Altering the mass had an inconsistent effect on the gait parameters tested. The subject volunteered that he preferred the prosthesis of the middle mass.     

假肢步态实验平台设计

背景:目前对于假肢的评价还停留在主观感受,缺乏一套客观的评价系统,建立模拟人体运动的在线假肢参数检测系统对于假肢性能的评价、假肢研究设计具有重要意义。目的:实现假肢的多种步态运动,并通过运动学、动力学数据的比对,评价其仿真程度。方法:根据仿生学原理,将下肢假肢简化成四杆四轴的力学模型,利用采集得到的多种步态模式,驱动下肢假肢运动,并搭建动态力学测试平台,实时测量假肢运动的地面垂直反力和前后剪力。结果与结论:假肢步态运动,髋膝关节的变化曲线与正常步态数据相一致,而其地面垂直反力与前后剪力也与正常人体相接近。提示假肢步态实验平台模拟了下肢假肢步态运动,并实时采集假肢运动的多项运动学、动力学参数,具备较高的仿真程度。     

Mechanical properties of prosthetic limbs: adapting to the patient.

Lower-limb amputees have identified comfort and mobility as the two most important characteristics of a prosthesis. While these in turn depend on a multitude of factors, they are strongly influenced by the biomechanical performance of the prosthesis and the loading it imparts to the residual limb. Recent years have seen improvements in several prosthetic components that are designed to improve patient comfort and mobility. In this paper, we discuss two of these: VSAP and prosthetic foot-ankle systems; specifically, their mechanical properties and impact on amputee gait are presented.     

The effects of prosthetic ankle dorsiflexion and energy return on below-knee amputee leg loading

Background

Prosthetic devices are intended to return lower limb amputees to their pre-amputation functional status. However, prosthetic devices designed for unilateral below-knee amputees have yet to completely restore the biomechanical functions normally provided by the ankle muscles, leading to gait asymmetries and increased reliance on their intact leg. In an effort to improve amputee gait, energy storage and return feet have been developed that store mechanical energy in elastic structures in early to mid-stance and return it in late stance. However, little is known regarding how ankle compliance and the level of energy return influences walking mechanics. The purpose of this study was to identify the influence of prosthetic ankle dorsiflexion and energy storage and return on leg loading during steady-state walking.

Methods

Compliant ankles with different stiffness levels were attached to a Seattle Lightfoot2 in different orientations (forward- and reverse-facing).

Findings

The ankles decreased residual leg vertical ground reaction forces in late stance, increased residual leg propulsive ground reaction force impulses and increased residual leg knee joint extensor moments. The reverse-facing ankles increased residual leg vertical ground reaction forces in early stance, and the compliant forward-facing ankle increased residual leg braking impulses. In contrast to previous studies, increased energy storage and return from compliant ankles did not decrease hip joint powers or the intact leg vertical ground reaction forces.

Interpretation

These results provide insight into the relationships between ankle dorsiflexion, energy storage and return, and leg loading, which may lead to more effective prosthetic devices to improve amputee gait.     

假肢步态实验平台设计

背景：目前对于假肢的评价还停留在主观感受,缺乏一套客观的评价系统,建立模拟人体运动的在线假肢参数检测系统对于假肢性能的评价、假肢研究设计具有重要意义。目的：实现假肢的多种步态运动,并通过运动学、动力学数据的比对,评价其仿真程度。方法：根据仿生学原理,将下肢假肢简化成四杆四轴的力学模型,利用采集得到的多种步态模式,驱动下肢假肢运动,并搭建动态力学测试平台,实时测量假肢运动的地面垂直反力和前后剪力。结果与结论：假肢步态运动,髋膝关节的变化曲线与正常步态数据相一致,而其地面垂直反力与前后剪力也与正常人体相接近。提示假肢步态实验平台模拟了下肢假肢步态运动,并实时采集假肢运动的多项运动学、动力学参数,具备较高的仿真程度。     

Stubby prostheses: an alternative to conventional prosthetic devices

Stubby prostheses offer potential advantages over conventional prosthetic devices in terms of safety, stability, and energy efficiency. Although cosmesis is compromised in the process, these short nonarticulated pylon prostheses may be a viable option to consider in bilateral A-K or knee disarticulation amputee patients under the following circumstances: (1) as a training tool to determine whether progression to full-length articulated devices is feasible; (2) as permanent prostheses for the patient whose primary need for ambulation is within his own home; (3) for the elderly bilateral amputee in whom ambulation is feasible but safety and energy efficiency are of particular importance; and (4) as a definitive device in the patient who expresses a preference for them. Two patients who have become successful users of stubby prostheses are presented to illustrate these points.     

A clinical comparison of variable-damping and mechanically passive prosthetic knee devices

OBJECTIVE: Although variable-damping knee prostheses offer some improvements over mechanically passive prostheses to transfemoral amputees, there is insufficient evidence that such prostheses provide advantages at self-selected walking speeds. In this investigation, we address this question by comparing two variable-damping knees, the hydraulic-based Otto Bock C-leg and the magnetorheological-based Ossur Rheo, with the mechanically passive, hydraulic-based Mauch SNS. DESIGN: For each prosthesis, metabolic data were collected on eight unilateral amputees walking at self-selected speeds across an indoor track. Furthermore, kinetic, kinematic, and electromyographic data were collected while walking at self-selected speeds across a 10-m walkway in a laboratory. RESULTS: When using the Rheo, metabolic rate decreases by 5% compared with the Mauch and by 3% compared with the C-leg. Furthermore, for the C-leg and Rheo knee devices, we observe biomechanical advantages over the mechanically passive Mauch. These advantages include an enhanced smoothness of gait, a decrease in hip work production, a lower peak hip flexion moment at terminal stance, and a reduction in peak hip power generation at toe-off. CONCLUSION: The results of this study indicate that variable-damping knee prostheses offer advantages over mechanically passive designs for unilateral transfemoral amputees walking at self-selected ambulatory speeds, and the results further suggest that a magnetorheological-based system may have advantages over hydraulic-based designs.     

A comparison of two prosthetic feet on the multi-joint and multi-plane kinetic gait compensations in individuals with a unilateral trans-tibial amputation

OBJECTIVE: To determine the effects of two different prosthetic feet on the three-dimensional kinetic patterns of both the prosthetic and sound limbs during unilateral trans-tibial amputee gait. DESIGN: Eleven individuals with a unilateral trans-tibial amputation participated in two walking sessions: once while using the conventional SAFE foot, the other while using the dynamic Flex foot. BACKGROUND: Despite the wide variation in the design of prosthetic feet, the benefits of these prostheses remain unclear. METHODS: During each test session, peak joint moments and powers in the sagittal, transverse and frontal planes were examined, as subjects walked at a comfortable speed. RESULTS: The majority of the kinetic differences that occurred due to the changing of prosthetic foot type were limited to ankle joint variables in the sagittal plane with greater peak moments and power during propulsion for the Flex foot compared to the SAFE foot. However, effects were also found at joints proximal to the prosthesis (e.g. knee) and differences were also found in the kinetics of the sound limb. CONCLUSION: The dynamic Flex foot allowed subjects to rely more heavily on the prosthetic foot for propulsion and stability during walking with minimal compensations at the remaining joints. RELEVANCE: Determining the biomechanical differences between the conventional and dynamic prosthetic feet may advocate the use of one prosthetic foot type over another. This information, when used in conjunction with subjective preferences, may contribute to higher functioning and greater satisfaction for individuals with a lower limb amputation.     

Exploration of paretic gait by differential loading in normals

OBJECTIVE: To determine if the gait patterns of artificially loaded healthy subjects resemble those of patients with weak ambulatory muscles. DESIGN: The gaits of artificially loaded healthy subjects and their controls were compared with the gaits of amputees and paretic patients, using analysis of variance. BACKGROUND: Muscle weakness due to paresis or limb amputation results in a misrelation between muscle power and body weight borne during ambulation. When body weight is increased by artificial loading of a normal subject, a misrelation between muscle strength and body weight results. METHODS: The gaits of paretic patients and artificially loaded normal subjects were recorded in the laboratory, by means of foot-switches. Stride length and stride frequency were used to calculate stride ratio which was used to compare the different gaits. RESULTS: Mean stride ratios of paraparetics, peroneal paretics and healthy subjects who carried load in the hand showed no statistically significant difference, while the ratio for hemiparetics differed significantly from the value for the artificially loaded healthy subjects. Below-knee amputees had a similar stride ratio to normal subjects who carried load on the ankles, while the above-knee stride ratio differed significantly from ankle-loaded normal subjects. CONCLUSION: Paraparetic and peroneal paretic gaits were approximated by the gaits of normal subjects who carried artificial load in the hand while the below-knee amputee gait was mimicked by normal subjects who carried load on the ankles. The two models of artificial loading could not generate any semblance with hemiparetic and above-knee gaits.     

Development of an integrated CAD-FEA process for below-knee prosthetic sockets

BACKGROUND: Computer-aided design and manufacturing has been successfully used in prosthetic applications since 1980s. It simplifies the socket rectification process and improves reproducibility but does not introduce any new principle into socket design. Integrating finite element analysis to CAD will provide a more objective assessment of socket fit and improve the chance of a successful first fitting. METHODS: Current study aims to establish a finite element model generation technique directly from geometrical information of commercial prosthetic CAD workstation. A program developed in-house automatically performs meshing of the stump geometry and assigns suitable material properties, load and boundary conditions to the model. The model was validated by comparing predicted pressure with experimentally measured values for one amputee subject. FINDINGS: The predicted pressure distribution has an root-mean-square error of 8.8 kPa compared to experimental values at 10%, 25% and 50% of the gait cycle. INTERPRETATION: Current method was able to develop a finite element model to predict interface pressure reasonably well and can be integrated with prosthetic CAD system to provide quantitative feedback to the prosthetist in an automated process.     

Lower-leg inertial properties in transtibial amputees and control subjects and their influence on the swing phase during gait

OBJECTIVES: To identify the factors that constitute optimal inertial properties for a lower-limb prosthesis. DESIGN: Experimental, controlled; simulation using a subject-specific double-pendulum model based on individual kinematic data and leg inertial properties. Simulation outcomes were compared with gait analysis data. SETTING: A gait laboratory. PARTICIPANTS: Ten transtibial amputees and 10 matched healthy controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Inertial properties of the lower leg; kinematics and kinetics of the swing phase; and kinematics of double-pendulum model simulations. RESULTS: In all amputees, inertial properties were reduced. No between-group differences existed in kinematics; hip and knee joint torques and powers were reduced in the amputees. Deviations between the double-pendulum model and experimental data were larger in the amputees than in the control subjects. CONCLUSIONS: Although current lightweight prostheses have less optimal pendular behavior, their light weight requires smaller joint torques to influence the pendular trajectory. Therefore, optimal inertial properties, in terms of swing phase kinematics and kinetics, will be a compromise between pendular properties and efficient control.     

The therapeutic effect of functional and transcutaneous electric stimulation on improving gait speed in stroke patients: a meta-analysis

OBJECTIVE: To determine the effect of previous treatments of functional electric stimulation (FES) and transcutaneous electric stimulation (TENS) on improving gait speed in subjects poststroke. DATA SOURCES: Relevant articles were obtained through a search of English-language articles cited in Medline, EMBASE, CINHAL, and PubMed databases from January 1966 to May 2005. STUDY SELECTION: Prospective clinical studies were included if electric stimulation was used to treat subjects poststroke and gait speed was used as an outcome measure. Excluded studies examined subjects with a variety of neurologic conditions, used implantable electrodes, or combined electric stimulation with treadmill training. A paired consensus between authors produced 8 articles. DATA EXTRACTION: Two investigators extracted data independently. The methodologic quality of the studies was assessed with the Downs and Black checklist. DATA SYNTHESIS: A fixed-effects model produced a mean difference (.18; 95% confidence interval, .08-.28) that was significant (z=3.65, P<.01), indicating the effectiveness of FES treatment at increasing gait speed in subjects poststroke. The effect sizes of the studies ranged from -.11 to 1.43 for FES and .19 to .42 for TENS. The type of FES and TENS devices, location of electrodes, amount of exposure, and subjects' stages of recovery varied between the studies. CONCLUSIONS: FES is effective at improving gait speed in subjects poststroke. Future research should examine the effectiveness of practical and readily available FES units to improve function in subjects in the subacute stages of recovery from a stroke. These studies should attempt to use a randomized controlled design with blinding and standardized outcome measures.     

Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

ABSTRACT: BACKGROUND: Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user's nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking. METHODS: We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step intersubject variability of these profiles by calculating variance-to-signal ratios. RESULTS: We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects. CONCLUSION: Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee's nervous system.