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.     

3D intersegmental knee loading in below-knee amputees across steady-state walking speeds

Background

Unilateral below-knee amputees often develop comorbidities that include knee joint disorders (e.g., intact leg knee osteoarthritis), with the mechanisms leading to these comorbidities being poorly understood. Mechanical knee loading of non-amputees has been associated with joint disorders and shown to be influenced by walking speed. However, the relationships between amputee knee loading and speed have not been identified. This study examined three-dimensional mechanical knee loading of amputees across a wide range of steady-state walking speeds.

Methods

Fourteen amputees and 10 non-amputee control subjects were analyzed at four overground walking speeds. At each speed, intersegmental joint moment and force impulses (i.e., time-integrals over the stance phase) were compared between the control, intact and residual knees using repeated-measures ANOVAs.

Findings

There were no differences in joint force impulses between the intact and control knees. The intact knee abduction moment impulse was lower than the non-amputees at 0.6 and 0.9 m/s. The intact knee flexion moment impulses at 0.6, 1.2 and 1.5 m/s and knee external rotation moment impulses at all speeds were greater than the residual knee. The residual knee extension moment and posterior force impulses were insensitive to speed increases, while these quantities increased in intact and control knees.

Interpretation

These results suggest the intact knees of asymptomatic and relatively new amputees are not overloaded during walking compared to non-amputees. Increased knee loads may develop in response to prolonged prosthesis usage or joint disorder onset. Further study is needed to determine if the identified bilateral loading asymmetries across speeds lead to diminished knee joint health.     

Attenuation of centre-of-pressure trajectory fluctuations under the prosthetic foot when using an articulating hydraulic ankle attachment compared to fixed attachment

Background

Disruptions to the progress of the centre-of-pressure trajectory beneath prosthetic feet have been reported previously. These disruptions reflect how body weight is transferred over the prosthetic limb and are governed by the compliance of the prosthetic foot device and its ability to simulate ankle function. This study investigated whether using an articulating hydraulic ankle attachment attenuates centre-of-pressure trajectory fluctuations under the prosthetic foot compared to a fixed attachment.

Methods

Twenty active unilateral trans-tibial amputees completed walking trials at their freely-selected, comfortable walking speed using both their habitual foot with either a rigid or elastic articulating attachment and a foot with a hydraulic ankle attachment. Centre-of-pressure displacement and velocity fluctuations beneath the prosthetic foot, prosthetic shank angular velocity during stance, and walking speed were compared between foot conditions.

Findings

Use of the hydraulic device eliminated or reduced the magnitude of posteriorly directed centre-of-pressure displacements, reduced centre-of-pressure velocity variability across single-support, increased mean forward angular velocity of the shank during early stance, and increased freely chosen comfortable walking speed (P ≤ 0.002).

Interpretation

The attenuation of centre-of-pressure trajectory fluctuations when using the hydraulic device indicated bodyweight was transferred onto the prosthetic limb in a smoother, less faltering manner which allowed the centre of mass to translate more quickly over the foot.     

The effects of hip and ankle stretching on gait function of older people

Christiansen CL. The effects of hip and ankle stretching on gait function of older people.

Objective

To examine effects of hip and ankle stretching on gait function of older people.

Design

Randomized controlled trial.

Setting

Flexibility training was performed in participants' homes. Assessments were performed in a biomechanics laboratory.

Participants

Forty healthy volunteers (mean age ± SD, 72.1±4.7y) randomized to 2 groups: intervention (n=20) and control (n=20).

Intervention

Intervention participants performed an 8-week stretching program, and control group participants maintained activity level for 8 weeks. One investigator made weekly visits to instruct and monitor participants.

Main Outcome Measures

Primary outcome measures were passive joint motion for hip extension and ankle dorsiflexion and freely chosen gait speed. Secondary outcome measures were gait parameters during freely chosen gait speed and set gait speed walking (stride length, joint displacement).

Results

Compared with the control group, the intervention group had increased combined hip and knee motion (P=.023), ankle motion (P=.020), and freely chosen gait speed (P=.016). The intervention group showed statistically nonsignificant trends of increased stride length at freely chosen gait speed and set gait speed.

Conclusions

Findings suggest joint motion is a modifiable impairment that is effectively targeted with flexibility training for older people. Participants in the intervention group had improvements in joint motion as well as increased freely chosen gait speed. Mechanisms responsible for changes in freely chosen gait speed warrant further investigation.     

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.     

The effect of ankle foot orthosis stiffness on the energy cost of walking: a simulation study

Background

In stroke and multiple sclerosis patients, gait is frequently hampered by a reduced ability to push-off with the ankle caused by weakness of the plantar-flexor muscles. To enhance ankle push-off and to decrease the high energy cost of walking, spring-like carbon-composite Ankle Foot Orthoses are frequently prescribed. However, it is unknown what Ankle Foot Orthoses stiffness should be used to obtain the most efficient gait. The aim of this simulation study was to gain insights into the effect of variation in Ankle Foot Orthosis stiffness on the amount of energy stored in the Ankle Foot Orthosis and the energy cost of walking.

Methods

We developed a two-dimensional forward-dynamic walking model with a passive spring at the ankle representing the Ankle Foot Orthosis and two constant torques at the hip for propulsion. We varied Ankle Foot Orthosis stiffness while keeping speed and step length constant.

Findings

We found an optimal stiffness, at which the energy delivered at the hip joint was minimal. Energy cost decreased with increasing energy storage in the ankle foot orthosis, but the most efficient gait did not occur with maximal energy storage. With maximum storage, push-off occurred too late to reduce the impact of the contralateral leg with the floor. Maximum return prior to foot strike was also suboptimal, as push-off occurred too early and its effects were subsequently counteracted by gravity. The optimal Ankle Foot Orthosis stiffness resulted in significant push-off timed just prior to foot strike and led to greater ankle plantar-flexion velocity just before contralateral foot strike.

Interpretation

Our results suggest that patient energy cost might be reduced by the proper choice of Ankle Foot Orthosis stiffness.     

The effect of custom-made braces for the ankle and hindfoot on ankle and foot kinematics and ground reaction forces

OBJECTIVE: To assess the effects on gait of custom-made polypropylene orthoses: ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A). DESIGN: Experimental assessment. SETTING: Institutional practice, motion analysis laboratory. PARTICIPANTS: Twenty asymptomatic normative subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Three-dimensional kinematics, ground reaction force, and time-related factors in 4 conditions: shoe only, and shod with the AFO, HFO-R, and HFO-A. RESULTS: The AFO and HFO-R limited sagittal and coronal plane ankle-hindfoot motion. The HFO-A limited hindfoot coronal motion while allowing normal sagittal motion. At the midfoot, the AFO and HFO-A limited transverse motion, but the HFO-A also limited sagittal and coronal motion. Use of the HFO-R resulted in exaggerated midfoot sagittal and coronal motion. Braces that limited motion to a greater degree were associated with more atypical kinetic variables, indicative of less dynamic gait. The HFO-A resulted in ground reaction forces most similar to unbraced conditions. CONCLUSIONS: Alteration in gait was affected by orthosis design. Orthoses with a rigid component crossing a joint restricted motion at that joint, but potentially compromised typical gait kinetic factors. For immobilizing the hindfoot, the HFO-A may be more comfortable and still provide more stability than the HFO-R or AFO.     

Three-dimensional motions of trunk and pelvis during transfemoral amputee gait

Goujon-Pillet H, Sapin E, Fodé P, Lavaste F. Three-dimensional motions of trunk and pelvis during transfemoral amputee gait.

Objectives

To identify characteristics of upper-body kinematics and torque transmission to the ground during locomotion in a group of patients with transfemoral amputation as compared with a group of asymptomatic subjects; and to investigate the influence of walking velocity and residual limb length on several characteristics of upper-body motion.

Design

Three-dimensional gait analysis with an optoelectronic device.

Setting

Gait laboratory.

Participants

Twenty-seven patients with transfemoral amputation and a control group of 33 nondisabled subjects.

Interventions

Not applicable.

Main Outcome Measures

Three-dimensional kinematics of the pelvis and the thorax and ground reaction force for amputees and control subjects.

Results

For subjects with transfemoral amputation, it was observed that upper-body angular ranges of motion (ROMs) increased globally as walking velocity decreased. For these subjects, specific patterns of pelvic rotation and torque transmission by the lower limbs around the vertical axis were found. The counter-rotation between the pelvic and scapular girdles was reduced. This reduction proved to be linked with the decrease of walking velocity. Walking velocity also affected all the parameters describing the motion of upper body. Pelvic ROM increased with the length of the limb decreasing.

Conclusions

The huge differences found between subjects with and without amputation suggest that the motion of the upper body must be considered to enhance gait.     

膝上假肢使用者步态对称性分析

在对膝上假肢使用才健侧和残侧的步态进行检测的基础上、对健、则在步态周期内的地面反力、下肢 时相对称性进行了对比和分析，时相对生差异是膝上截肢者步态的主要问题，指同了产生时相不对称的原因并对则对健侧的影响进行了探讨。由于受残侧的影响，健侧的步态与正常步态相差也很大，所得结论对改进假肢性能１假肢装配和患者的训练有重要意义。     

Effects of ankle dorsiflexion on active and passive unilateral straight leg raising

The purpose of this study was to analyze the straight-leg-raising (SLR) maneuver while the ankle was fixed in dorsiflexion or relaxed in plantar flexion. Twenty-two healthy subjects underwent active and passive SLR with the ankle in each position. We used cinematography to document movement of the right lower limb and pelvis and electromyography to document hamstring muscle activity. Analyses of variance of the angles of maximum SLR and change in the pelvic position showed a significant F ratio (p = .01) among the active and passive trials. Post hoc analyses demonstrated significant differences (p = .01) between SLR with dorsiflexion and SLR with plantar flexion. The EMG activity among trials was not significantly different. The possible causes of the effects of dorsiflexion on SLR are discussed. We encourage clinicians to document and compare SLR with dorsiflexion and SLR with plantar flexion, and we recommend additional research to examine the relative influence of tissue structures on SLR.     

The influence of fascial manipulation on function,ankle dorsiflexion range of motion and postural sway in individuals with chronic ankle instability

BackgroundProprioceptive deficits may attribute to functional Chronic ankle instability (CAI) with impairments in balance and postural control. Physical therapy interventions such as taping, bracing, manual therapy, and balance training play an essential role in managing ankle instabilities. Fascial Manipulation (FM) is a manual therapy technique considered to restore function by improving the joint range of motion and proprioception. However, the effects of FM on Ankle dorsiflexion range of motion (ADROM) and postural sway in athletes with chronic ankle instability are unclear.ObjectiveThis study aims to determine the effect of FM on function, ADROM, and Postural sway in athletes with CAI.DesignSingle group, pretest-posttest design.MethodsIndividuals with a history of recurrent ankle sprains with the Cumberland ankle instability tool (CAIT) score of ≤27 were included. FM was applied to the painful and densified center of coordination points on the lower limb myofascial lines based on Stecco's FM method. The outcomes measures include Foot and ankle disability index (FADI), ADROM during the weight-bearing lunge, and postural sway (excursion of the center of pressure during single limb stance).ResultsThere was a significant improvement in the FADI scores (Z = −3.626, p < 0.05), ADROM [F (2)=38.056, p<0.05], ηp ² = 0.69 following FM. However, the center of pressure excursion with both opened and closed eyes showed no differences following FM.ConclusionSince fascial manipulation had shown improvement in the function and ankle dorsiflexion range, it can be used as an adjunct treatment strategy in CAI management.     

The influence of excess body mass on adult gait

Background

This study aimed to assess the presentation of gait for adults who are overweight, independent of the confounding influence of velocity.

Methods

Cross sectional study design. Twenty-five adults of a healthy weight were matched by age, gender, height and velocity to twenty-five adults who were overweight. Participants traversed a 10 m walkway embedded with 2 AMTI force platforms (AMTI BP400600 Force Platforms: Advanced Mechanical Technologies, Inc., Watertown, MA, USA) and running between 2 CODA Dual CX1 sensors (CODA CX1: Charnwood Dynamics, Barrow on Soar, Leicestershire, England). Temporal–spatial parameters, maximum ground reaction forces, maximum joint powers, and three dimensional kinematic and kinetic parameters at the 7 events of the gait cycle were assessed.

Findings

With velocity accounted for, relatively few changes in the presentation of gait were seen for adults who were overweight. Alterations included increased stance phase duration, hip flexion, knee flexion, hip abduction, and knee varus for overweight adults. A reduction in hip abductor moment normalised for body mass was noted for overweight adults. Absolute maximum ground reaction forces were increased while maximum hip power absorption was reduced for overweight adults.

Interpretation

Changes were seen at the hip and knee during the swing phase of gait. During swing there is a stronger association with soft tissue injury as compared to joint injury. Overweight individuals were seen to adopt few alterations during the stance phase to accommodate for the increased absolute ground reaction forces. As a result the joint surfaces of overweight adults are exposed to increased loading.     

Modeling and simulation of muscle forces of trans-tibial amputee to study effect of prosthetic alignment

BackgroundThe muscle forces tend to change when any musculoskeletal system is damaged. It is necessary to predict and explain the patterns of muscle forces in the stump of a left trans-tibial amputee during walking, and to study the effects of the prosthetic alignment.MethodsMusculoskeletal modeling and computer simulation were combined to calculate muscle forces in the trans-tibial lower limb during walking. The prosthesis was aligned to be in optimal position for the subject and then changed into +6° and −6° in the sagittal plane relatively. Kinematic data of the stump wearing a prosthesis and ground reaction forces were simultaneously recorded by a gait analysis system and a force platform, respectively. The data were input into a model of the lower trans-tibial extremity with three-dimensional geometry and the corresponding seven muscle forces were predicted by a static optimization.FindingsMuscles performed much more actively in stance than in swing phase. Most muscles appeared very active around both heel-strike and toe-off. Muscle forces predicted were similar to that in temporal distribution at all three alignment conditions but the major muscles such as gluteus maximus, hamstrings, vasti and rectus femoris generated remarkable greater forces in −6° and +6° alignments than the normal condition.InterpretationThe above results showed the muscle forces increasing at the mal-alignment. Because the incorrect alignment could break the relative position of the socket and foot, and that would generate the extra joint moments. As a result, muscle forces increased, and the long-duration fatigue occurs more easily. The finding suggests that the proper prosthetic alignment is very important for the stump muscles normal activities.     

Comparative effect of walking meditation and rubber-band exercise on ankle proprioception and balance performance among persons with chronic ankle instability: A randomized controlled trial

BackgroundAnkle proprioception and balance impairments are usual consequences of chronic ankle instability (CAI). The impairments affect functional and sport activities and can lead to recurrent ankle sprain. Mind-body practice is claimed to improve ankle proprioception and balance.ObjectiveTo investigate the effects of walking meditation, a mind-body practice, and compare it with the rubber-band exercise on ankle proprioception and balance among individuals with CAI.Study designA randomized controlled trial.MethodsThirty-two participants with CAI aged 20.3 ± 1.8 years were randomized into three groups; 1) walking meditation (WM, n = 10), 2) Rubber-band exercise (RE, n = 11) and 3) control (n = 11). WM and RE were enrolled on a 4-week training regimen (30 min/day, 3 days/week). Before and after the training, ankle proprioception was evaluated by angular error of the ankle reposition test (AEA) at three positions, randomly, i.e., plantarflexion-5°, plantarflexion-10° and dorsiflexion-5°. Balance performance was assessed by the star excursion balance test (SEBT).ResultsAs adjusted by pre-training baseline, no significant difference in AEA and SEBT was found among three groups. However, after training, only the WM group revealed a significant decrease in AEA at plantarflexion-5° (p = 0.007) and plantarflexion-10° (p = 0.04) compared to the baseline. For SEBT, the WM and RE groups showed significant improvements compared to the baseline in 4 directions each (p < 0.05), while the control group improved only 2 directions (p < 0.05).ConclusionsWM and RE groups significantly improved SEBT after 4-week training when compared to before training. Additionally, WM group also improved ankle proprioception. Therefore, WM demonstrates feasibility as a promising intervention that could be applied for balance and ankle proprioceptive rehabilitations in persons with CAI.     

Kinematic comparison of walking on uneven ground using powered and unpowered prostheses

Background

Recent research has focused on the design of intelligent prosthetic ankle devices with the goal of adapting behavior of the device to accommodate all walking surfaces that an individual encounters in daily life. To date, no studies have looked at how such devices perform on uneven terrain.

Methods

11 young adults with unilateral transtibial amputation participated in two data collection sessions spaced approximately 3 weeks apart. In each session they walked across a loose rock surface at three controlled speeds. In the first session, they wore a passive, energy storage and return prosthesis and in the second, they wore a powered prosthesis (BiOM, iWalk, Bedford, MA, USA).

Findings

Subjects had a 10% faster self-selected walking speed when wearing the powered (1.16 m/s) compared to unpowered prosthesis (1.05 m/s; p = 0.031). They walked with increased ankle plantarflexion on their prosthetic limb throughout the gait cycle when wearing the powered compared to unpowered prosthesis. This was especially evident in the increased plantarflexion during push-off (p < 0.001). There was a small (< 3°), but statistically significant decrease in knee flexion during early stance when wearing the powered device (p = 0.045). Otherwise, the kinematics of the knee and hip were nearly identical when wearing the different devices. Subjects had decreased medial–lateral motion of their center of mass when wearing the powered prosthesis (p = 0.020), but there were no differences in medial–lateral margins of stability between the devices (p = 0.662).

Interpretation

Subjects did not significantly alter their proximal joint kinematics on this irregular surface as a result of the addition of power.