Determining asymmetry of roll-over shapes in prosthetic walking

How does the inherent asymmetry of the locomotor system in people with lower-limb amputation affect the ankle-foot roll-over shape of prosthetic walking? In a single-case design, we evaluated the walking patterns of six people with lower-limb amputation (3 transtibial and 3 transfemoral) and three matched nondisabled controls. We analyzed the walking patterns in terms of roll-over characteristics and spatial and temporal factors. We determined the level of asymmetry by roll-over shape comparison (root-mean-square distance) as well as differences in radius of curvature. In addition, we calculated ratios to determine spatial and temporal asymmetries and described different aspects of asymmetry of roll-over shapes. All participants showed some level of asymmetry in roll-over shape, even the nondisabled controls. Furthermore, we found good intralimb reproducibility for the group as a whole. With respect to spatial and temporal factors, the participants with transtibial amputation had a quite symmetrical gait pattern, while the gait in the participants with transfemoral amputation was more asymmetrical. The individual ankle-foot roll-over shapes provide additional insight into the marked individual adjustments occurring during the stance phase of the nondisabled limb. The two methods we present are suitable for determining asymmetry of roll-over shapes; both methods should be used complementarily.     

Gait characteristics of persons with bilateral transtibial amputations

The gait characteristics of persons with unilateral transtibial amputations are fairly well documented in the literature. However, much less is known about the gait of persons with bilateral transtibial amputations. This study used quantitative gait analysis to investigate the gait characteristics of 19 persons with bilateral transtibial amputations. To reduce variability between subjects, we fitted all subjects with Seattle Lightfoot II feet 2 weeks before their gait analyses. The data indicated that subjects walked with symmetrical temporospatial, kinematic, and kinetic parameters. Compared with nondisabled controls, the subjects with amputations walked with slower speeds and lower cadences, had shorter step lengths and wider step widths, and displayed hip hiking during swing phase. Additionally, compared with the nondisabled controls walking at comparable speeds, the subjects with amputations demonstrated reduced ankle dorsiflexion and knee flexion in stance phase, reduced peak ankle plantar flexor moment, reduced positive ankle power (i.e., energy return) in late stance, and increased positive and negative hip power. These results demonstrate the deficiencies in current prosthetic componentry and suggest that further research is needed to enhance prosthesis function and improve gait in persons with amputations.     

Efficacy of shock-absorbing versus rigid pylons for impact reduction in transtibial amputees based on laboratory, field, and outcome metrics

Prosthetic manufacturers have marketed shock-absorbing pylons (SAPs) for attenuation of injurious loads from foot-ground contact. In this study, we compared a commonly prescribed SAP with a conventional rigid pylon, using a within-subject design (n = 15 unilateral transtibial amputees), to assess effect on gait mechanics, measure transmitted accelerations in situ, and determine functional outcomes using step counts and questionnaires. No differences were found across pylons for self-selected walking speed, prosthetic-side step length, prosthetic-side loading rate and decelerative peak of the vertical ground reaction force, peak pylon acceleration, step count per week, or questionnaire results that examined pylon performance and subjects' pain and fatigue levels. The only statistically significant finding was for the prosthetic-side knee angle at initial contact, where subjects displayed an average of 2.6 degrees more flexion with the rigid pylon than the SAP while walking at a controlled speed (p = 0.004); this result indicates that transtibial amputees are able to modulate the effective stiffness of their residual limb in response to changes in prosthetic component stiffness. The results from the laboratory, field, and subjective outcome measurements suggest that the SAP in this study is as effective as a rigid pylon for unilateral transtibial amputees.     

Walking symmetry and energy cost in persons with unilateral transtibial amputations: matching prosthetic and intact limb inertial properties

OBJECTIVES: To investigate the hypothesis that increasing the mass and moment of inertia of the prosthetic limb of people with unilateral, transtibial amputations to match the mass and moment of inertia of the intact limb improves walking symmetry without increasing energy cost. DESIGN: Gait symmetry and metabolic energy cost of walking for six subjects with unilateral, transtibial amputations were evaluated under three prosthesis loading conditions. SETTING: University research laboratory. SUBJECTS: Six ambulatory individuals with unilateral, transtibial amputations. INTERVENTIONS: Subjects walked at 1.34 m/sec under three prosthetic limb loading conditions: (1) no added load; (2) loading that produced a match of prosthetic shank and foot mass and moment of inertia with those of the intact limb (100% load); and (3) a load that was half that of the 100% condition (50% load). MAIN OUTCOME MEASURES: Step length, swing time, stance time, and metabolic energy expenditure. RESULTS: As mass and moment of inertia of the prosthetic limb became more closely matched to the intact limb, step length, swing time, and stance time became less symmetrical. Energy cost for the 100% load condition was significantly greater (6% to 7%) than the baseline and 50% conditions. CONCLUSIONS: The loading configuration required to produce a match in the moments of inertia of the prosthetic and intact lower legs resulted in greater gait asymmetry and higher energy cost.     

Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension

BackgroundThe elevated vacuum suspension system has demonstrated unique health benefits for amputees, but the effect of vacuum pressure values on gait characteristics is still unclear. The purpose of this study was to investigate the effects of elevated vacuum levels on temporal parameters, kinematics and kinetics for unilateral transtibial amputees.MethodsThree-dimensional gait analysis was conducted in 9 unilateral transtibial amputees walking at a controlled speed with five vacuum levels ranging from 0 to 20 in Hg, and also in 9 able-bodied subjects walking at self-preferred speed. Repeated ANOVA and Dunnett's t-test were performed to determine the effect of vacuum level and limb for within subject and between groups.FindingsThe effect of vacuum level significantly affected peak hip external rotation and external knee adduction moment. Maximum braking and propulsive ground reaction forces generally increased for the residual limb and decreased for the intact limb with increasing vacuum. Additionally, the intact limb experienced an increased loading due to gait asymmetry for several variables.InterpretationThere was no systematic vacuum level effect on gait. Higher vacuum levels, such as 15 and 20 in Hg, were more comfortable and provided some relief to the intact limb, but may also increase the risk of osteoarthritis of the residual limb due to the increased peak external hip and knee adduction moments. Very low vacuum should be avoided because of the negative effects on gait symmetry. A moderate vacuum level at 15 in Hg is suggested for unilateral transtibial amputees with elevated vacuum suspension.     

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.     

Gait patterns of transtibial amputee patients walking indoors barefoot

OBJECTIVE: To evaluate the gait patterns of lower limb amputee patients walking with and without shoes and to identify differences in barefoot gait patterns when using different prosthetic feet. DESIGN: Optoelectronic three-dimensional motion analysis of gait was performed on six transtibial amputees using a solid ankle cushion heel foot and a single-axis foot, both with and without shoes. RESULTS: Gait abnormalities were observed during barefoot walking when the solid ankle cushion heel foot was used. These included knee joint hyperextension of 9.9 +/- 2.0 degrees and the loss of ankle plantar flexion in the early stance phase. When the single-axis foot was used, knee flexion thrust declined from 9.9 +/- 3.7 degrees to 7.2 +/- 3.8 degrees and ankle plantar flexion decreased from 9.9 +/- 2.8 degrees to 7.0 +/- 2.1 degrees during the early stance phase. CONCLUSIONS: In transtibial amputees, significant gait abnormalities were observed during barefoot walking using the solid ankle cushion heel foot. These gait patterns improved, however, with use of a single-axis prosthetic foot, which permits a further plantar flexion after the initial contact.     

Sprint kinematics of athletes with lower-limb amputations.

OBJECTIVE: To determine and compare the kinematics of the sound and prosthetic limb in five of the world's best unilateral amputee sprinters. SUBJECTS: Five men, all unilateral lower-limb amputee (one transfemoral, four transtibial) athletes. The individual with transfemoral amputation used a Endolite Hi-activity prosthesis incorporating a CaTech hydraulic swing and stance control unit, a Flex-Foot Modular III, and an ischial containment total contact socket. Those with transtibial amputations used prostheses incorporating a Flex-Foot Modular III and patellar tendon-bearing socket, with silicone sheath liner (Iceross) and lanyard suspension. DESIGN: Case series. Subjects were videotaped sprinting through a performance area. Sagittal plane lower-limb kinematics derived from manual digitization (at 50 Hz) of the video were determined for three sprint trials of the prosthetic and sound limb. Hip, knee, and ankle kinematics of each subject's sound and prosthetic limb were compared to highlight kinematic alterations resulting from the use of individual prostheses. Comparisons were also made with mean data from five able-bodied men who had similar sprinting ability. RESULTS: Sound limb hip and knee kinematics in all subjects with amputation were comparable to those in able-bodied subjects. The prosthetic knee of the transfemoral amputee athlete fully extended early in swing and remained so through stance. In the transtibial amputee athletes, as in able-bodied subjects, a pattern of stance flexion-extension was evident for both limbs. During stance, prosthetic ankle angles of the transtibial amputee subjects were similar to those of the sound side and those of able-bodied subjects. CONCLUSION: Prosthetic limb kinematics in transtibial amputee subjects were similar to those for the sound limb, and individuals achieved an "up-on-the-toes" gait typical of able-bodied sprinting. Kinematics for the prosthetic limb of the transfemoral amputee subject were more typical of those seen for walking. This resulted in a sprinting gait with large kinematic asymmetries between contralateral limbs.     

The mechanics of landing when stepping down in unilateral lower-limb amputees

BACKGROUND: The ability to successfully negotiate stairs and steps is an important factor for functional independence. While work has been undertaken to understand the biomechanics of gait in lower-limb amputees, little is known about how amputees negotiate stairs and steps. This study aimed to determine the mechanics of landing in unilateral lower-limb amputees when stepping down to a new level. A secondary aim was to assess the effects of using a shank-mounted shock-absorbing device (Tele-Torsion Pylon) on the mechanics of landing. METHODS: Ten unilateral amputees (five transfemoral and five transtibial) and eight able-bodied controls performed single steps down to a new level (73 and 219 mm). Trials were repeated in amputees with the Tele-Torsion Pylon active and inactive. The mechanics of landing were evaluated by analysing peak limb longitudinal force, maximal limb shortening, lower extremity stiffness, and knee joint angular displacement during the initial contact period, and limb and ankle angle at the instant of ground-contact. Data were collected using a Vicon 3D motion analysis system and two force platforms. FINDINGS: Amputees landed on a straightened and near vertical limb. This limb position was maintained in transfemoral amputees, whereas in transtibial amputees knee flexion occurred. As a result lower extremity stiffness was significantly greater in transfemoral amputees compared to transtibial amputees and able-bodied controls (P<0.001). The Tele-Torsion Pylon had little effect on the mechanics of landing in transtibial amputees, but brought about a reduction in lower extremity stiffness in transfemoral amputees (P<0.05). INTERPRETATION: Amputees used a stepping strategy that ensured the direction of the ground reaction force vector was kept anterior of the knee joint centre. Using a Tele-Torsion Pylon may improve the mechanics of landing during downward stepping in transfemoral amputees.     

A noncontact sensor for measurement of distal residual-limb position during walking

A simple noncontact device was implemented for measuring the position of the distal residual limb relative to the prosthetic socket during ambulation. The device was a small and lightweight photoelectric sensor positioned within a frame mounted immediately beneath the socket. Calibration tests showed that the sensor had a displacement range of 60.0 mm. The root-mean-square error for all sources of error considered (different reflective surfaces, peak-to-peak signal noise, drift, nonlinearity, different surface tilt angles, surface curvature, and wetness [simulating sweating]) was <1.95% full-scale output. We used the sensor in a preliminary study on a unilateral, transtibial amputee with diabetes to assess pistoning during ambulation. Results showed an average 41.7 mm proximal displacement during swing phase relative to stance phase. When the subject was walking on a flat surface, pistoning was significantly less (p = 0.000) with a supracondylar strap compared with no supracondylar strap, although the difference was not substantial (0.8 mm). A 5 min rest period caused the limb to displace proximally in the socket approximately 4.8 mm during subsequent walking trials, possibly reflecting limb enlargement and thus a more proximal position in the socket after the rest period. The device can potentially be used in prosthetics research for evaluating clinical features that may affect limb position and pistoning and thus fit.     

Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet

We examined the application of outcome measures to determine changes in function caused by standardized functional prosthetic gait training and the use of four different prosthetic feet in people with unilateral transtibial limb loss. Two self-report measures (Prosthetic Evaluation Questionnaire-Mobility Scale [PEQ-13] and Locomotor Capabilities Index [LCI]), and three performance-based measures (Amputee Mobility Predictor with a prosthesis [AMPPRO], 6-minute walk test [6MWT] and step activity monitor [SAM]) were used. Ten people with unilateral transtibial limb loss, five with peripheral vascular disease (PVD) and five without PVD, completed testing. Subjects were tested at baseline and after receiving training with their existing prosthesis and with the study socket and four prosthetic feet, i.e., SACH (solid ankle cushion heel), SAFE (stationary attachment flexible endoskeletal), Talux, and Proprio feet, over 8 to 10 weeks. Training was administered between testing sessions. No differences were detected by the PEQ-13, LCI, 6MWT, or SAM following training and after fitting with test feet. The AMPPRO demonstrated differences following training with the existing prosthesis in the PVD group and between selected feet from baseline testing ( p 相似文献   

Assessment of upper-body dynamic stability during walking in patients with subacute stroke

The analysis of upper-body acceleration is a promising and simple technique to quantitatively assess dynamic gait stability. However, this method has rarely been used for people with stroke, probably because of some technical issues still not addressed. We evaluated the root-mean-square (RMS) and harmonic ratio of trunk accelerations for a group of 15 inpatients with subacute stroke who were able to walk (61.4 +/- 14.9 yr) and compared them with those of an age-matched group of nondisabled subjects (65.1 +/- 8.8 yr) and those of a highly functional group of young nondisabled subjects (29.0 +/- 5.0 yr). Small (<2%) but significant (p < 0.03) differences were found in RMS values obtained by applying the two most common computational approaches: (1) averaging among individual-stride RMS values and (2) computing the RMS value over the entire walking trial without stride partitioning. We found that the intersubject dependency of acceleration RMS values by selected walking speed was specific for each group and for each of the three body axes. The analysis of ratios between these three accelerations provided informative outcomes correlated with clinical scores and not affected by walking speed. Our findings are an important step toward transferring accelerometry from human movement analysis laboratories to clinical settings.     

A preliminary investigation of pelvic obliquity patterns during gait in persons with transtibial and transfemoral amputation

Differences in pelvic obliquity between small groups of persons with unilateral lower limb amputation and subjects without amputation were analyzed. Kinematic walking data were collected as six males with transtibial amputation and three males with transfemoral amputation walked over a range of speeds. The pelvic obliquity patterns and amplitudes from the groups with amputation were compared to normal data. Results showed that smaller peak-to-peak amplitudes of pelvic obliquity were associated with higher amputation levels. Pelvic drop during early prosthetic-limb stance tended to be smaller than during early sound-limb stance. Most of the subjects with amputation exhibited an obliquity pattern in which the hip on the prosthetic side was raised above the stance-side hip during prosthetic swing phase, indicative of a compensatory action known as hip-hiking. The subjects with transfemoral amputation exhibited this hip-hiking pattern during sound-limb swing phase as well. Results from this study suggest that further investigation is required to determine those limitations of current prosthetic technology that adversely affect pelvic obliquity in the gait of persons with amputation, and to determine if significant benefit can be realized by restoring a normal pattern of pelvic obliquity to the gait of persons with amputation.     

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

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. 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 inter-subject variability of these profiles by calculating variance-to-signal ratios. 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. 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.     

Effects of alignment on interface pressure for transtibial amputee during walking

Purpose. To assess the mechanical behaviour at interface for unilateral transtibial amputees during walking when the prosthesis is misaligned, since studies examining interface pressure between residual limb and prosthetic socket have been restricted to unsupported stance and natural gait.

Method. One male subject with transtibial amputation volunteers for the study. Interface pressures over five sites are measured under three sagittal alignment settings. MP (mean peak interface pressure), TP₉₀₊ (time in which pressure exceeded 90% of peak pressure) and TPI₉₀₊ (time-pressure integral at the period of sustained sub-maximal load) are discussed for each alignment setting.

Results. Compared with optimal alignment, the trend of interface pressure, the mean peak pressure do not change much, but the duration of sub-maximal pressure changes remarkably, except that at the patellar tendon, and finally the TPI₉₀₊ changes considerably with different alignment settings.

Conclusions. The results offer the clinician and paramedical staff further insight in residual limb/socket interface mechanics in the transtibial amputation patients and provide potentially useful information for socket design and prosthesis fitting.     

Psychological state estimation from physiological recordings during robot-assisted gait rehabilitation

Robot-assisted treadmill training is an established intervention used to improve walking ability in patients with neurological disorders. Although it has been shown that attention to the task is a key factor for successful rehabilitation, the psychological state of patients during robot-assisted gait therapy is often neglected. We presented 17 nondisabled subjects and 10 patients with neurological disorders a virtual-reality task with varying difficulty levels to induce feelings of being bored, excited, and overstressed. We developed an approach to automatically estimate and classify a patient's psychological state, i.e., his or her mental engagement, in real time during gait training. We used psychophysiological measurements to obtain an objective measure of the current psychological state. Automatic classification was performed by a neural network. We found that heart rate, skin conductance responses, and skin temperature can be used as markers for psychological states in the presence of physical effort induced by walking. The classifier achieved a classification error of 1.4% for nondisabled subjects and 2.1% for patients with neurological disorders. Using our new method, we processed the psychological state data in real time. Our method is a first step toward real-time auto-adaptive gait training with potential to improve rehabilitation results by optimally challenging patients at all times during exercise.     

Interlimb symmetry of traumatic unilateral transtibial amputees wearing two different prosthetic feet in the early rehabilitation stage

This study evaluated the SACH and the Greissinger Plus prosthetic feet, in terms of the symmetry provided between the lower limbs, in the case of unilateral transtibial amputees 16.3 weeks from the time of limb fitting and 38.9 weeks from surgery. Sagittal plane gait analysis was carried out for nine right-limb traumatic amputees. In all examined cases, the spatial and temporal parameters measured were significantly improved. When the symmetry indexes of the same parameters calculated with three different methods were considered, significant improvement was observed for the hip and ankle ranges of motion and the stance phase period. However, no significant differences were found for the symmetry indexes of the knee range of motion, cadence, and walking speed. In addition, for most spatial parameters, the statistical significance varied considerably among the three methods used for the analysis of symmetry.     

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.     

比较青年男子走与跑的能量消耗

背景：能量代谢是健身、减重、行军、假肢评定、医疗诊断等比较关注的热点之一。康复师与健身教练根据具体情况以及不同目的选择不同的运动方式、运动量与运动强度,有关同等运动速度不同走跑步态模式的能量消耗差异研究较少。目的：探讨相同运动速度两种步态模式下走跑步态特征以及能耗差异,为大众健身以及运动处方的制定提供理论支持。方法：受试者为男性健康大学生志愿者20名,使用H/P/COSMOS Gaitway跑台控制走跑运动的速度,测量走跑的步频和步长,使用气体成分分析仪VO2000间接测试人体的能量代谢。在人体第一骶椎放置两维加速度传感器采集前后方向以及垂直方向的加速度原始信号。结果与结论：相同速度跑模式的步频明显高于走模式下的步频。随着速度的递增,行走主要依靠步频的增加,而跑动时主要依靠步长加大来维持速度。同等速度下跑的能耗明显高于行走的能耗。相同速度下跑明显大于走的人体质心垂直方向加速度均方根值。建议根据不同目的选择不同的步态模式,如需要减重健身时可选择跑模式,而在长距离行军时为了节省能量可以选择快走模式。