Storage Foot Research Articles

Finite element modeling of an energy storing and return prosthetic foot and implications of stiffness on rollover shape.

Energy storing and return (ESAR) prosthetic feet showed continuous improvements during the last 30 years. Despite this, standard guidelines are still missing to achieve an optimal foot design in terms of performances. One of the most important design parameters in ESAR feet is the Rollover Shape (RoS). This represents the foot Center of Pressure (CoP) path in a shank-based coordinate system during stance. RoS objectively describes the foot behavior according to its stiffness, which depends on foot geometry and material. This work presents the development of a finite element modeling methodology able to predict the stiffness characteristic of an ESAR foot and its RoS. The validation of the model is performed on a well-known commercially available prosthetic foot both in bench tests and realistic walking scenario. The obtained results confirm an error of +6.1% on stiffness estimation and +10.2% on RoS evaluation, which underlines that the proposed method is a powerful tool able to replicate the mechanical behavior of a prosthetic foot.

Prosthetic Limb User Experiences With Crossover Feet: A Pilot Focus Group Study to Explore Outcomes That Matter

ABSTRACT Introduction Many different prosthetic feet are available to meet the diverse needs of people with lower-limb amputation. Current methods used to assess comparative effectiveness of prosthetic feet may not align with outcomes that are most important to people with lower-limb amputation. User participation in qualitative research is one approach to guide selection of outcome measures for clinical practice and quantitative research studies. This pilot study examined outcomes of importance to people who have used both energy storing and crossover prosthetic feet. Materials and Methods An in-person focus group of people with lower-limb amputation was conducted. Inclusion criteria were as follows: 18 years of age or older, lower-limb amputation, previous use of an energy storing foot and crossover foot, and a minimum of 1 year prosthesis use. Results Five participants with lower-limb amputation (4 males/1 female), aged 41 to 59 years (mean, 45.6 ± 7.7 years), participated in the focus group. Three participants had unilateral transtibial amputations; one had bilateral transtibial amputations; and another had bilateral involvement with a transtibial and partial-foot amputation. All participants reported daily use of a prosthesis (mean, 15.2 ± 1.1 hours). Three categories of themes arose from this focus group: direct outcomes, external influences, and indirect outcomes. Direct outcomes included balance and stability, endurance and sustained gait quality, and naturalness. External influences included peer and prosthetist interactions. Indirect outcomes included increased confidence and expanded mobility. Outcome measures available to assess identified constructs were suggested. Conclusions Engagement of prosthesis users through qualitative research methods can inform the choice of outcome measures used to assess clinical outcomes or evaluate the effectiveness of prosthetic devices.

Energy storing and return prosthetic feet improve step length symmetry while preserving margins of stability in persons with transtibial amputation

BackgroundEnergy storing and return (ESAR) feet are generally preferred over solid ankle cushioned heel (SACH) feet by people with a lower limb amputation. While ESAR feet have been shown to have only limited effect on gait economy, other functional benefits should account for this preference. A simple biomechanical model suggests that enhanced gait stability and gait symmetry could prove to explain part of the difference in the subjective preference between both feet.AimTo investigate whether increased push-off power with ESAR feet increases center of mass velocity at push off and enhance intact step length and step length symmetry while preserving the margin of stability during walking in people with a transtibial prosthesis.MethodsFifteen people with a unilateral transtibial amputation walked with their prescribed ESAR foot and a SACH foot at a fixed walking speed (1.2 m/s) over a level walkway while kinematic and kinetic data were collected. Push-off work generated by the foot, center of mass velocity, step length, step length symmetry and backward margin of stability were assessed and compared between feet.ResultsPush-off work was significantly higher when using the ESAR foot compared to the SACH foot. Simultaneously, center of mass velocity at toe-off was higher with ESAR compared to SACH, and intact step length and step length symmetry increased without reducing the backward margin of stability.ConclusionCompared to the SACH foot, the ESAR foot allowed an improvement of step length symmetry while preserving the backward margin of stability at community ambulation speed. These benefits may possibly contribute to the subjective preference for ESAR feet in people with a lower limb amputation.

Differences in Gait Patterns of Unilateral Transtibial Amputees With Two Types of Energy Storing Prosthetic Feet.

ObjectiveTo evaluate if there is a difference in gait pattern when applying two different shapes of energy storing prosthetic feet for trainstibial amputation we conducted a comparative study. Energy storing prosthetic feet for transtibial amputation are increasing in use, but there are few studies that evaluate the effects of the shape of energy storing feet on gait patterns.MethodsTen unilateral transtibial amputees were recruited. Two different shapes of dynamic response feet were applied to each subject either 1C30 Trias or 1C60 Triton. The main differences between the two are a split forefoot and the presence of a heel wedge. Spatiotemporal, kinematic, and kinetic data was obtained through gait analysis. Differences between intact and prosthetic side and differences between the two prosthetics were assessed.ResultsOn a side to side comparison, cadence asymmetry with 1C30 Trias was observed. Ankle plantarflexion at the end of stance and ankle supination at the onset of preswing was smaller with both prosthetic feet compared to the intact side. Other spatiotemporal, kinematic, and kinetic data showed no significant differences in a side to side comparison. In a comparison between the two prosthetics, stance and swing ratio and ankle dorsiflexion through mid-stance was closer to normal with 1C60 Triton than 1C30 Trias. Other spatiotemporal, kinematic, and kinetic data showed no statistically significant differences between prosthetics.ConclusionBoth energy storing feet implants showed symmetric gait in unilateral transtibial amputees who are functionally independent in daily living. And 1C60 Triton showed closer to normal gait patterns than 1C30 Trias in our study.

Energy expenditure in people with transtibial amputation walking with crossover and energy storing prosthetic feet: A randomized within-subject study

BackgroundEnergy storing feet are unable to reduce the energy required for normal locomotion among people with transtibial amputation. Crossover feet, which incorporate aspects of energy storing and running specific feet, are designed to maximize energy return while providing stability for everyday activities. Research questionDo crossover prosthetic feet reduce the energy expenditure of walking across a range of speeds, when compared with energy storing feet among people with transtibial amputation due to non-dysvascular causes? MethodsA randomized within-subject study was conducted with a volunteer sample of twenty-seven adults with unilateral transtibial amputation due to non-dysvascular causes. Participants were fit with two prostheses. One had an energy storing foot (Össur Variflex) and the other a crossover foot (Össur Cheetah Xplore). Other components, including sockets, suspension, and interface were standardized. Energy expenditure was measured with a portable respirometer (Cosmed K4b2) while participants walked on a treadmill at self-selected slow, comfortable, and fast speeds with each prosthesis. Gross oxygen consumption rates (VO2 ml/min) were compared between foot conditions. Energy storing feet were used as the baseline condition because they are used by most people with a lower limb prosthesis. Analyses were performed to identify people who may benefit from transition to crossover feet. ResultsOn average, participants had lower oxygen consumption in the crossover foot condition compared to the energy storing foot condition at each self-selected walking speed, but this difference was not statistically significant. Participants with farther six-minute walk test distances, higher daily step counts, and higher Medicare Functional Classification Levels at baseline were more likely to use less energy in the crossover foot. SignificanceCrossover feet may be most beneficial for people with higher activity levels and physical fitness. Further research is needed to examine the effect of crossover feet on energy expenditure during high-level activities.

Prosthetic restoration in patient with incomplete spinal cord injury.

We describe a case of 55-years-old man with a known T11 AIS C since 1985. The muscle strength of his left leg is better than the right leg and he is an active community ambulator. He walks using his right knee ankle foot orthosis without a knee lock. However, on April 2012 he had undergone a left transtibial amputation secondary to infected diabetic foot ulcer. He only had his first contact with rehabilitation team 2 months after the amputation and started on gait retraining since. Given the fact that he is a K3 level as he used to climb Batu Caves which is known to have 272 steps and he plans to continue this activity for his religious purposes, we prescribed him with prosthesis - patella tendon bearing socket, pin and lock suspension, silicone liner and energy storing foot. In conclusion, a community ambulator in dual disabilities, that is, spinal cord injury and amputee is hardly encountered due to multiple confounding factors. However, the right prosthetic prescription in patient with good prognosticating factors to ambulate will determine successful rehabilitation.

Step to step transition cost when walking with an energy storing and release prosthetic foot and SACH foot

s / Gait & Posture 39S (2014) S1–S141 S83 Table 1 Cohort information (height and mass including prostheses). Participant Age (yrs) Height (m) Mass (kg) Amputation level Time between fitting and Session 1 (days) Activity on limbs between Sessions 1 and 2 (h)

Variability of kinetic variables during gait in unilateral transtibial amputees

Prosthetic gait increases demands on stability. Some variability measures can be used to investigate the stability of movement for prosthetic feet. The purpose of this study was to determine the influence of the prosthetic foot on ground reaction force variability for transtibial amputee gait. Comparative analysis. Eleven male unilateral transtibial amputees participated in this study. Each subject walked at self-selected speed with both conventional (SACH) and energy storing (Sureflex) feet. Time and ground reaction force variables and their coefficients of variation were calculated for each foot type and limb. Mediolateral force variables had high variability for all conditions. The Sureflex had a larger variability than the SACH foot for the braking peak (p < 0.05), which may have been caused by gait instability after the heel strike. There were significant differences between intact and prosthetic limbs in total loading (force impulses) with the SACH foot (p < 0.05). The prosthetic foot and alignment issues related to the foot influence GRF variability. During the braking phase the SACH foot is characterized by higher variability in mediolateral direction and Sureflex by higher variability in anterior-posterior direction. Differences in variability in ground reaction force variables can represent a person's stability. Observing variability can contribute to better understanding of critical events in gait cycle with the use of various prosthetic feet.

Design, development and performance evaluation of latent heat storage foot warmers

In this paper, three PCM based foot warmers of cylindrical and rectangular in shape were designed, developed and fabricated to store solar energy during sunshine hours. The stored energy was utilised to warm the feet in the late evening to replace electric heaters. By trial experiment, it was found out that the surface temperature of the storage units of the foot warmer should be between 37?C?41?C for heating the feet. Therefore, commercial grade lauric acid (Melting Point 42.2?C, Latent Heat of Fusion 181 ? 103 J/kg) was used as a latent heat storage material. Experiments were conducted during a winter season to study the latent heat storage units and the thermal performance of the rectangular shaped foot warmer was found better than the cylindrical shaped with the same storage capacity. The experimental thermal performance studies of these latent heat storage systems showed that such type of foot warmer can be used for heating purpose of the feet and legs in composite and cold and sunny climates.

Amputation rehabilitation and prosthetic restoration. From surgery to community reintegration

Purpose: The purpose of this review is to summarize the literature related to the advances that have taken place in the management and rehabilitation care of limb amputation.Results: Prostheses for the lower and upper limb amputee have changed greatly over the past several years, with advances in components, socket fabrication and fitting techniques, suspension systems and sources of power and electronic controls. Higher levels of limb amputation can now be fitted with functional prostheses, which allow more patients to achieve independent life styles. This is of particular importance for the multi-limb amputee. The rehabilitation of more traditional lower limb levels of amputation have also greatly benefited from the technological advances including energy storing feet, electronic control hydraulic knees, ankle rotators and shock absorbers to mention a few. For the upper limb amputee, myoelectric and proportional controlled terminal devices and elbow joints are now used routinely in some rehabilitation facilities. Experimental prosthetic fitting techniques and devices such as the use of osseo-implantation for suspension of the prosthesis, tension control hands or electromagnetic fluids for knee movement control will also be briefly discussed in this paper.Conclusion: It is possible to conclude from this review that many advances have occurred that have greatly impacted the functional outcomes of patients with limb amputation.

인공발(Prosthetic Foot) 스프링용 유리섬유강화 적층재의 적층배향에 따른 층간분리거동 해석

It is considered that the application of advanced composite materials to the prostheses for the disables is important to improve their bio-mechanical performance. Particularly, energy storing foot prosthesis is mostly important to restore gait ability of the disables with low-extremity amputation since it could provide propulsion at terminal stance enhancing the disables ability to walk long distance even run and jump. Therefore, the energy storing spring of prosthetic foot keel under cyclic bending moment use mainly of high strength glass fiber reinforced plastic. The main objective of this study was to evaluate the stacking sequence effect using the delamination growth rate(dA_D/dN) of energy storing spring in glass fiber reinforced plastic under cyclic bending moment. The test results indicated that the shape of delamination zone depends on stacking sequence in GFRP laminates. Delamination area(A_D) tums out that variable types with the contour increased non-linearly toward the damage zones.

A new technique for the calculation of the energy stored, dissipated, and recovered in different ankle-foot prostheses

Previous research reported calculation of mechanical power of ankle-foot devices using the dot product of the ankle moment times the ankle angular velocity. Unfortunately, there are two errors in this analysis technique. The biomechanical model used assumed a rigid foot articulating around the ankle and there was no accounting for energy storage or dissipation and recovery in the viscoelastic material of the cosmetic cover. The first purpose of this paper is to propose a rigorous technique for the calculation of the net energy efficiency that could be used for any articulated or nonarticulated ankle-foot prosthesis. The second purpose is to quantify the amount of energy stored or dissipated and then recovered in order to discriminate between different ankle-foot prostheses. The SACH, Seattle, Flex-foot, and Golden-Ankle ankle-foot prostheses; were evaluated on the same amputee, while walking at his natural cadence. The power entering and leaving the distal end of the prosthetic leg was calculated as the sum of the translational (force-velocity product) and rotational (moment-angular velocity product). All ankle-foot prostheses showed the same distal power pattern. After initial contact, a large energy storage was observed in the cushioned heel, which was followed by some energy recovery. Then, during mid and late stance, another period of storage or dissipation and recovery was observed. Even the SACH foot should be considered an energy storing foot prosthesis since it's cosmetic material was seen to be capable of recovering energy. The balance between the rate of change of foot mechanical energy and the foot powers showed that the new technique takes into account the energy stored or dissipated and then recovered within the compliant material and flexing keel. The new analysis technique can be used by prosthetic designers to assess any type of ankle-foot prostheses. Criteria for ankle-foot prosthesis selection should include, not only the net mechanical efficiency for both rearfoot and forefoot sections, but also, the total energy recovered by the ankle-foot prostheses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

BIOMECHANICAL ANALYSIS OF THE INFLUENCE OF PROSTHETIC FEET ON BELOW-KNEE AMPUTEE WALKING

Although energy storing prosthetic feet have achieved widespread clinical acceptance, the effect of these components on the biomechanics of below-knee amputee gait is poorly understood. The purpose of this study was to determine the biomechanical adaptations used by the below-knee amputee while wearing a conventional prosthetic foot and to assess the influence of energy storing prosthetic feet on these adaptations. Mechanical power outputs of the lower extremity in five normal and five below-knee amputee subjects using the SACH, Seattle and Flex feet were studied. Ground reaction forces and kinematic data were collected at a walking speed of 1.5 m/s and were used to determine the muscular power outputs of the lower extremity during stance. Consistent patterns of muscular power output at the hip and knee of the residual limb occur. While wearing the SACH foot, negligible energy generation occurs at the prosthetic foot during pushoff. A decrease in energy absorption at the knee during the first half of stance and an increase in energy generation by the hip extensors were the major adaptations noted in the proximal muscle groups. Compared to the SACH foot, the energy storing feet demonstrated increased energy generation during pushoff. Despite the improvements in the performance of the energy storing prosthetic feet, no significant differences were found in the pattern or magnitude of knee and hip power outputs compared to the SACH foot.

Joint moment and muscle power output characteristics of below knee amputees during running: The influence of energy storing prosthetic feet

Stance phase joint moments, muscle power outputs and mechanical energy characteristics were determined in five normal and five below knee amputee subjects running at 2.8 m s −1. The amputees were studied sequentially on three different prosthetic feet: the SACH foot (solid ankle cushion heel), and two energy storing feet, Seattle and Flex. While wearing the SACH foot, the amputees exhibited major alterations in the distribution and magnitude of muscle power output and muscle work: (1) the total work done by the lower extremity was reduced; (2) the hip extensors became the main source of energy absorption and generation, while in normal subjects the ankle plantarflexors were the major energy generators and the knee extensors the major energy absorbers; (3) the eccentric and concentric knee extensor power outputs were reduced and an abnormal concentric knee flexor power output was noted immediately after heel contact. In four of the amputees, energy storing feet resulted in improvements in the power output and mechanical work characteristics of the lower extremity: (1) the energy storing prosthetic feet generated 2–3 times greater energy than the SACH foot; (2) with the Flex foot the amputees exhibited a more normal pattern and magnitude of hip and knee extensor muscle work. One of the subjects, however, exhibited increased abnormalities with the energy storing prosthetic feet. The amount of energy restored relative to the amount of energy absorbed by each of the prosthetic feet was greater with the energy storing feet than the SACH foot (Flex 84%, Seattle 52%, SACH 31%).