Energy-storing Foot Research Articles

Effects of high-profile crossover feet on gait biomechanics in 2 individuals with Syme amputation.

Prosthetic treatment options for people with ankle disarticulation (i.e., Syme amputation) are limited. Prosthetic feet designed for people with Syme amputation are often low profile to accommodate build-height restrictions, resulting in decreased energy return during gait. High-profile crossover feet that attach to the posterior proximal aspect of the prosthetic socket can bypass these restrictions and may promote a more physiologic gait pattern. To compare level-ground gait biomechanics and patient-reported outcomes between crossover and traditional energy-storing feet in people with Syme amputation. Within-participant pilot study. Both participants were fit with energy-storing and crossover feet and were randomized to the order they used the feet. Participants used each foot for 2 weeks before assessment. Step length symmetry, prosthetic ankle range of motion, prosthetic-side energy return, and peak sound-side loading were determined from motion capture data obtained in a laboratory. Mobility and balance confidence were measured using standardized patient-reported outcome measures. Foot preference was assessed with an ad hoc survey. Two participants with Syme amputations completed the study. Prosthetic ankle peak dorsiflexion and push-off power increased with the crossover foot compared with the energy-storing foot for both participants. Both participants reported an overall preference of the crossover foot. Changes in patient-reported outcomes did not exceed published minimum detectable change values. Crossover feet increased prosthetic ankle range of motion and energy return compared with traditional energy-storing feet in this pilot investigation of 2 participants. Crossover feet seem to promote physiologic gait and may be a promising alternative to traditional low-profile feet for people with Syme amputation.

Identification of Gait-Cycle Phases for Prosthesis Control.

The major problem with transfemoral prostheses is their capacity to compensate for the loss of the knee joint. The identification of gait-cycle phases plays an important role in the control of these prostheses. Such control is completely up to the patient in passive prostheses or partly facilitated by the prosthesis in semiactive prostheses. In both cases, the patient recovers his/her walking ability through a suitable rehabilitation procedure that aims at recreating proprioception in the patient. Understanding proprioception passes through the identification of conditions and parameters that make the patient aware of lower-limb body segments’ postures, and the recognition of the current gait-cycle phase/period is the first step of this awareness. Here, a proposal is presented for the identification of the gait-cycle phases/periods under different walking conditions together with a control logic for a possible active/semiactive prosthesis. The proposal is based on the detection of different gait-cycle events as well as on different walking conditions through a load sensor, which is implemented by analyzing the variations in some gait parameters. The validation of the proposed method is done by using gait-cycle data present in the literature. The proposal assumes the prosthesis is equipped with an energy-storing foot without mobility.

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.

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.

Assessment of low- and high-level task performance in people with transtibial amputation using crossover and energy-storing prosthetic feet: A pilot study.

Crossover feet incorporate features of energy-storing feet and running-specific feet. As such, crossover feet may be suitable for both daily ambulation and participation in physically demanding activities. To compare crossover feet and energy-storing feet on performance-based tests including a range of low-level (e.g. sit-to-stand) and high-level (e.g. jogging) activities. Cross-sectional, repeated measures. Participants with transtibial amputation completed a battery of performance-based outcome measures, including the Five Times Sit-to-Stand, Timed-Up-and-Go, Four Square Step Test, and the Comprehensive High-level Activity Mobility Predictor. Participants wore duplicate prostheses fit with crossover feet and energy-storing feet to perform the tests; the order of foot conditions was randomized. Paired t tests were used to evaluate differences between feet and order of testing. Data from seven participants showed improvements in all measures while using crossover feet. Improvements in the second foot condition were also observed, indicating a practice effect for all measures. However, differences between feet and order of conditions were not statistically significant ( p > 0.05). Results of this study suggest that crossover feet may improve low- and high-level mobility outcomes. However, intervention effects are small and practice effects were observed in all outcomes. Future research is needed to evaluate the influence of practice effects on performance-based mobility measures. Crossover feet may improve transtibial prosthesis users' performance compared to energy-storing feet across a range of activities, but additional research is needed. Practice effects may be an influential factor in the measurement of performance-based mobility outcomes and should be considered when performing a clinical assessment.

Functional Outcomes in People with Transtibial Amputation Using Crossover and Energy-Storing Prosthetic Feet: A Pilot Study

ABSTRACT Introduction Contemporary prosthetic feet are purposefully designed to address the many functional limitations experienced by people with transtibial amputation (TTA). Choice of materials, geometry, and fabrication techniques contribute to the overall performance of the foot, and ultimately to the functional outcomes achieved by the user. The crossover foot is a novel foot design that integrates features from traditional energy-storing feet and modern, running-specific feet in an effort to maximize performance and energy return. Although initial user feedback is promising, research is needed to determine whether the crossover foot is capable of improving user outcomes relative to other types of contemporary prosthetic feet. Materials and Methods A cross-sectional pilot study was conducted to evaluate mobility, endurance, perceived exertion, and walking performance attained by participants wearing prostheses with crossover and energy-storing feet. Participants with unilateral TTA were administered a short battery of performance-based tests while wearing a prosthesis with a crossover foot and a prosthesis with a traditional energy-storing foot. The order of prostheses worn was randomly assigned. Tests included the Timed Up and Go (TUG) performed at comfortable speed, the TUG performed at fast speed, and the 6-minute walk test (6MWT). Spatiotemporal measures (speed, cadence, step length, step width, and step time) were assessed during the 6MWT using a GAITRite electronic walkway. Participants were asked to report their perceived exertion following the 6MWT using the Borg rating of perceived exertion (CR100). Results Seven participants completed all pilot study procedures. On average, participants exhibited better mobility at comfortable and fast speeds (0.83 second and 0.63 second faster during the TUG-comfortable and TUG-fast, respectively), improved endurance (19.7 m farther in the 6MWT), reduced perceived exertion (12.9 points less on the Borg CR100), increased speed (0.05 m/s), faster cadence (2 steps/min), and longer sound side steps (3.3 cm) while wearing the crossover foot than when wearing the energy-storing foot. However, not all participants exhibited the same functional benefits from using the crossover foot. Conclusions The crossover foot is a promising prosthetic foot design that appears to provide modest functional benefits to transtibial prosthesis users. Given the pilot nature of this study, additional research is needed to assess benefits across a larger and more diverse range of users to inform prescription practices.

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.

Laboratory- and community-based health outcomes in people with transtibial amputation using crossover and energy-storing prosthetic feet: A randomized crossover trial.

Contemporary prosthetic feet are generally optimized for either daily or high-level activities. Prosthesis users, therefore, often require multiple prostheses to participate in activities that span a range of mobility. Crossover feet (XF) are designed to increase the range of activities that can be performed with a single prosthesis. However, little evidence exists to guide clinical prescription of XF relative to traditional energy storing feet (ESF). The objective of this study was to assess the effects of XF and ESF on health outcomes in people with transtibial amputation. A randomized crossover study was conducted to assess changes in laboratory-based (endurance, perceived exertion, walking performance) and community-based (step activity and self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction) outcomes. Twenty-seven participants were fit with XF and ESF prostheses with standardized sockets, interfaces, and suspensions. Participants were not blinded to the intervention, and wore each prosthesis for one month while their steps were counted with an activity monitor. After each accommodation period, participants returned for data collection. Endurance and perceived exertion were measured with the Six-Minute Walk Test and Borg-CR100, respectively. Walking performance was measured using an electronic walkway. Self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction were measured with survey instruments. Participants also reported foot preferences upon conclusion of the study. Differences between feet were assessed with a crossover analysis. While using XF, users experienced improvements in most community-based outcomes, including mobility (p = .001), fatigue (p = .001), balance confidence (p = .005), activity restrictions (p = .002), and functional satisfaction (p < .001). Participants also exhibited longer sound side steps in XF compared to ESF (p < .001). Most participants (89%) reported an overall preference for XF; others (11%) reported no preference. Results indicate that XF may be a promising alternative to ESF for people with transtibial amputation who engage in a range of mobility activities.Trial registration: ClinicalTrials.gov NCT02440711

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.

Outcome of trans-tibial amputees equipped with energy-storing foot in Nord-Pas de Calais and Picardie

Outcome of trans-tibial amputees equipped with energy-storing foot in Nord-Pas de Calais and Picardie

A Comparative Study of Conventional and Energy-Storing Prosthetic Feet in High-Functioning Transfemoral Amputees

Graham LE, Datta D, Heller B, Howitt J. 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±0.13m/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°±4.73°, P<.001) and 3 times as much power from the prosthetic ankle at push-off (1.13±0.22W/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.

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.

An iterative method for viscoelastic modeling of prosthetic feet

Prosthetic foot designs are growing in complexity, but a few material and structural properties, including stiffness and viscoelasticity, remain critical to foot function. Consistent identification of these critical properties would aid prosthesis prescription. This investigation evaluates a new technique to model prosthetic feet as a combination of springs and dampers, and therefore characterize a foot's stiffness and viscoelasticity by means of spring and damper coefficients. A quasi-Newton iterative algorithm was developed to determine model coefficients for 9 prosthetic feet based on compressive creep, stress–relaxation, and constant strain rate tests. A broad range of current energy-storing feet including designs from Otto Bock, Seattle, Kingsley, and Ohio Willow Wood were very accurately modeled with the iterative technique. Feet without a solid ankle from Flex and College Park were the least accurately modeled. The Flex foot, tested without a cover, had a considerably lower damping coefficient. Damper coefficients were similar for most all other feet, suggesting similar material properties of the foam cover. Stiffness varied and generally agreed with published data. The ability of the model to produce two separate parallel spring stiffness constants might provide insight into foot structure. The model represents a means to objectively quantify material properties for a range of solid ankle dynamic elastic response prosthetic feet, but may be limited in its characterization of other foot varieties.

Synthesis of a cycloidal mechanism of the prosthetic ankle.

Most prosthetic feet are designed to mimic shock absorption and push-off (Gitter et al., 1991). Such materials as tibreglass and carbon graphite in Seattle Foot, Flex-Foot, Carbon Copy II, so-called Energy Storing (ES) prosthetic feet, enable a greater portion of energy of the “falling” body to be accumulated and released before plantar flexion (Bartkus et al., 1994). The ES feet provide some amount of eversion/inversion as well in the Genesis Foot, Seattle-Light, and Dual Ankle Springs (DAS). Certain positive outcomes of using ES feet have been reported, e.g. improved ankle range of motion and gait symmetry (Wagner et al., 1987); a smaller number of skin problems like abrasions compared to the “conventional” SACH foot (Alaranta et al., 1994). The amputees preferred ES feet as transmitting Jess shock and having greater damping properties (Wirta et al., 1991). Nevertheless, ES feet have not shown sufficient improvement in overall performance (Childress et al., 1974; Torbum et al., 1990; Lehmann et al., 1993) in comparison with the conventional SACH foot (Goh et al., 1984). No significant differences in frequency of stump pain were observed (Aiaranta et al., 1994). No improvements have been found in such amputee gait characteristics such as the performance of the existing knee in trans-tibial patients (Edelstein, 1990). During the early stance, the patient's knee bends notably less than normal because the prosthetic foot, either conventional, or ES does not produce the controlled plantar flexion obtained naturally by eccentric contraction of dorsiflexors. Knee flexion is also less than normal during late stance. The author believes, that the reason for this is that both SACH and ES feet have a similar mechanical outcome in the dorsiflexion phase, namely, the moment of resistance to dorsiflexion, and this characteristic does not mimic the moment of resistance to dorsiflexion in normal gait. The moment of resistance (resistive curve) to dorsiflexion in a normal ankle typically has a concave downwards shape shown in Figure 1a (Scott and Winter, 1991). The beginning of dorsiflexion during regular level gait occurs with practically no resistance from plantar flexor muscles. Then, resistance slowly increases as the dorsiflexion progresses, while at the end of dorsiflexion the resistance rapidly increases nonlinearly. In contrast with this concave shape of resistive curve seen in the normal ankle, existing prostheses demonstrate a convex shape of their resistive curves (Fig. 1b). Fig. 1 (a). Moment of resistance (resistive curve) to dorsiflexion in the ankle during normal walking (from Scott and Winter (1991), with kind permission from Elsevier Science Ltd., Kidlington OX5 1GB, UK. If one agrees that a concave resistive curve in the prosthetic ankle is beneficial for an amputee's gait and wants to build an initially compliant prosthesis, the conflict between compliance and durability must first be overcome. Mechanically there are two basic structures employed in the ES foot design. The first is an L-shaped leaf spring (Seattle Foot, Flex-Foot, Carbon Copy II). The second is a multi-bar linkage with elastic elements (Genesis Foot, DAS, College Park Foot). Both types of mechanisms have similar resistive curves (Fig. 1b) with at least non-concave shape (convex or linear). Both types of mechanisms provide an initial moment of resistance M0 which must be applied to a tibial component of the prosthesis to deviate from a vertical position and to articulate the ankle. As this analysis indicates, the initial resistive moment M0 cannot be made zero in both kinds of mechanisms. In a mechanism based on the L-shaped leaf spring, for example, the structure acts simultaneously as a resistor to deflection and as a feature for load bearing. If a designer intends to lower M0 he is at risk of losing durability. The purpose of this work was to synthesise a mechanism of a prosthetic foot with more natural moment of resistance in the dorsiflexion phase.

Bioenergetic comparison of a new energy-storing foot and SACH foot in traumatic below-knee vascular amputations

In this study, the metabolic performances of a new energy-storing foot (Proteor) and of the solid-ankle cushion heel (SACH) are compared. Twelve patients with traumatic below-knee amputations (mean age: 50.0 ± 19.9 years) and 12 patients with vascular below-knee amputations (mean age: 73 ± 7 years) were studied. Oxygen uptake ( V ˙ O 2 ) was measured in all the subjects on a walkway at a self-selected velocity; only the subjects with traumatic amputation were tested on a level treadmill (progressive speed: 2.4–4 and 6 km/h), and then in two randomized trials: incline (+5%) and decline walking treadmill test at 4 km/h. Vascular explorations were done in the vascular patients: distal pressure measurements, pulse plethysmography, transcutaneous oxygen tension. Free walking was improved in subjects with traumatic amputation using the energy-storing foot (+6%), with a better bioenergetic efficiency (0.24 ± 0.4mL/kg · m vs 0.22 ± 0.04mL/kg · m). However, in subjects with vascular amputation, this foot did not produce an increased free velocity nor an improved energy cost. During the level treadmill test, the traumatic amputee subjects showed a decrease of energy expenditure with the new prosthetic foot, more significant at sufficient speed (4 km/h): 17.00 ± 3.42 vs 14.67 ± 2.05 mL/kg/min ( p < .05). The same effect is shown during the incline (19.31 ± 2.80 vs 16.79 ± 2.32mL/kg/min— p < .02) and decline walking tests (14.13 ± 3.64 vs 11.81 ± 1.54mL/kg/min— p < .02). There is no significant difference in cardiocirculatory effects between the two types of prosthetic foot. Despite a lower velocity, the subjects with vascular amputation exceed 70% of the maximal heart rate, with the cardiocirculatory factor being the main cause of walking restriction. The energy-storing foot should be reserved for active and fast walkers, whereas the SACH foot seems more suitable for elderly patients with amputation with a slow walk.

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%).