Optimal Powered Ankle-Foot Prosthesis Torque Profiles to Improve Walking Performance for Individuals With a Unilateral Transtibial Amputation.

Individuals with unilateral transtibial amputation (TTA) often demonstrate asymmetrical gait patterns, which are further exacerbated during load carriage as passive prostheses cannot modulate their mechanical stiffness to accommodate the increased demand. Load carriage also increases the loads on the intact limb that can lead to overuse injuries and is also associated with increased metabolic cost and decreased forward propulsion. While active and passive load-suspended backpacks have been studied in healthy populations, no studies have explored the use of active backpacks to improve the walking performance for individuals with TTA. Therefore, the purpose of this study was to identify active backpack loading patterns to improve the metabolic cost, forward propulsion, and knee joint loading of individuals with TTA using a musculoskeletal simulation-based optimization framework. Different loading patterns were simulated using a time-varying actuator force applied to an active backpack over the gait cycle. The magnitude and timing of the actuator force were optimized for each performance criterion that resulted in a unique actuation pattern for each biomechanical measure. Interestingly, similar improvements relative to a passive backpack were observed across all actuation patterns, regardless of the optimization criteria. With all active backpacks, the force impulse experienced by the body from the dynamic load decreased, which resulted in increased forward propulsion, decreased intact knee joint loading, and improved metabolic cost. This suggests that active backpacks have the potential to improve walking performance during load carriage for individuals with TTA.

People have debated whether athletes with transtibial amputations should compete with nonamputees in track events despite insufficient information regarding how the use of running-specific prostheses (RSPs) affect athletic performance. Thus, we sought to quantify the spatiotemporal variables, ground reaction forces, and spring-mass mechanics of the fastest athlete with a unilateral transtibial amputation using an RSP to reveal how he adapts his biomechanics to achieve elite running speeds. Accordingly, we measured ground reaction forces during treadmill running trials spanning 2.87 to 11.55 m/s of the current male International Paralympic Committee T44 100- and 200-m world record holder. To achieve faster running speeds, the present study's athlete increased his affected leg (AL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and his unaffected leg (UL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and greater stance average vertical ground reaction forces ( P < 0.001). At faster running speeds, step time decreased for both legs ( P < 0.001) through shorter ground contact and aerial times ( P < 0.001). Unlike athletes with unilateral transtibial amputations, this athlete maintained constant AL and UL stiffness across running speeds ( P ≥ 0.569). Across speeds, AL step lengths were 8% longer ( P < 0.001) despite 16% lower AL stance average vertical ground reaction forces compared with the UL ( P < 0.001). The present study's athlete exhibited biomechanics that differed from those of athletes with bilateral and without transtibial amputations. Overall, we present the biomechanics of the fastest athlete with a unilateral transtibial amputation, providing insight into the functional abilities of athletes with transtibial amputations using running-specific prostheses. NEW & NOTEWORTHY The present study's athlete achieved the fastest treadmill running trial ever attained by an individual with a leg amputation (11.55 m/s). From 2.87 to 11.55 m/s, the present study's athlete maintained constant affected and unaffected leg stiffness, which is atypical for athletes with unilateral transtibial amputations. Furthermore, the asymmetric vertical ground reaction forces of athletes with unilateral transtibial amputations during running may be the result of leg length discrepancies.

Introduction Loss of power production at the ankle joint contributes to many problems people with unilateral transtibial (UTT) amputation experience during walking. Little is known about walking acceleration and deceleration, which is common in daily living and may require substantial compensatory behaviors from the residual lower-limb joints. Objective The aim of this study was to quantify individual lower-limb joint contributions to walking acceleration and deceleration in people with UTT amputations. We hypothesized that joint work on the prosthetic limb would be primarily modulated at the hip, and joint work on the sound limb would be primarily modulated at the ankle. Study Design The study is a repeated-measures design. Methods Six K3 level ambulators with UTT amputations participated. Participants performed a total of 40 walking trials while wearing their own nonarticulated dynamic prosthetic foot and socket. Each trial consisted of walking along a straight walkway. After walking approximately 2 m, participants received a cue instructing them to perform one of three walking conditions: continue walking at a constant average velocity, rapidly accelerate, or rapidly decelerate. We used ground reaction forces and motion capture data to derive joint kinematics and kinetics during the three walking conditions. We used one-way repeated-measures analyses of variance (ANOVAs) to identify significant differences between conditions. Results For the sound limb, positive hip and ankle work was significantly greater during acceleration compared with constant average velocity or deceleration conditions, and negative knee work was significantly greater during acceleration compared with deceleration. For the prosthetic limb, negative ankle work was significantly greater during acceleration compared with deceleration. Conclusions People with UTT amputation who use nonarticulated prostheses primarily modulated joint work on their sound limb to accelerate or decelerate walking speed. Clinical Relevance Characterizing compensatory behaviors of people with a UTT amputation is important for understanding injury mechanisms, informing clinical guidelines, and improving future ankle-foot prosthesis designs.

Introduction Prosthetic ankle-foot devices incorporating a hydraulic articulation between the pylon and prosthetic foot have been shown to be beneficial to the gait of more active individuals with unilateral transtibial amputation (UTA). However, the functional benefits of using hydraulic ankle-foot devices to less active individuals with UTA are yet to be determined. The aim of the current study was to investigate the effects on gait performance of using a non-energy-storage-and-return foot with a hydraulic attachment compared with an identical rigidly attached foot during overground walking in less active individuals with UTA. Materials and Methods Kinematic and kinetic data were recorded while five individuals with UTA, deemed K2 activity level by their prescribing physician, performed two-minute walk tests (2MWTs) and 10 overground gait trials in two conditions: using a hydraulically articulating ankle-foot device (HYD) and using a rigidly attached ankle-foot device (RIG). Results Walking speed during the 2MWT was increased by 6.5% on average in the HYD (1.07 m/second) condition compared with the RIG (1.01 m/second) condition (Cohen d = 0.4). Participants displayed more symmetrical interlimb loading (d = 0.8), increased minimum forward center of pressure velocity (d = 0.8), increased peak shank rotational velocity (d = 1.0), and decreased prosthetic energy efficiency (d = 0.7) when using the HYD compared with the RIG device. Conclusions Individuals with lower activity levels walk faster and therefore further when using a foot with a hydraulically articulating attachment in comparison with a rigid attachment. A reduced braking effect in early stance phase as a result of the action of the hydraulic component present in the articulating attachment partially explains the improvement in walking performance.

Carbon fibre insoles (CFIs) may be a highly suitable option to augment ankle moment and improve walking performance in older adults. However, some footwear modifications have been implicated as possible contributors in detrimentally altering knee joint loading. Therefore, the purpose of the study was to determine the magnitude of differences in model-predicted knee joint loading in healthy older adults walking with three footwear conditions (i.e. standard walking shoes with and without 1.6-mm and 3.2-mm CFIs). Participants (n = 14) completed three, 2-minute walking trials (i.e. no insole, 1.6-mm CFIs, and 3.2-mm CFIs) on a dual-belt instrumented treadmill at self-selected overground walking speed. Marker trajectories and ground reaction forces were extracted from a single step occurring at the midpoint of the trial and used as inputs to a computational cost-optimisation algorithm (i.e. Concurrent Optimisation of Muscle Activation and Kinematics) to estimate medial and lateral tibiofemoral joint contact force magnitudes. A repeated-measures, functional linear model assessed within-subject differences in knee joint contact force profiles across conditions. Compared to standardised footwear alone, neither the 1.6-mm CFIs nor 3.2-mm CFIs significantly altered knee joint contact forces in the medial compartment of the tibiofemoral joint. Greater lateral compartment tibiofemoral joint contact force magnitudes were identified only for the 3.2-mm CFIs compared to the 1.6-mm CFIs in a small portion of late stance (81%–91% stance phase; maximum between-condition difference: +0.23 kN; d = 1.53). Altered knee joint forces may not be a substantial contraindication for older adults who seek to use CFIs to enhance walking performance.

A comparison of two different prosthetic feet on functional capacity, pain severity, satisfaction level and quality of life in high activity patients with unilateral traumatic transtibial amputation

Running-specific prostheses reduce lower-limb muscle activity compared to daily-use prostheses in people with unilateral transtibial amputations

Running-specific prostheses enable athletes with lower limb amputations to run by emulating the spring-like function of biological legs. Current prosthetic stiffness and height recommendations aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, it is unclear how different prosthetic configurations influence the biomechanics and metabolic cost of running. Consequently, we investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic cost of running. Ten athletes with unilateral transtibial amputations each performed 15 running trials at 2.5 or 3.0 m/s while we measured ground reaction forces and metabolic rates. Athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. Use of an Ottobock 1E90 Sprinter prosthesis reduced metabolic cost by 4.3 and 3.4% compared with use of Freedom Innovations Catapult [fixed effect (β) = -0.177; P < 0.001] and Össur Flex-Run (β = -0.139; P = 0.002) prostheses, respectively. Neither prosthetic stiffness (P ≥ 0.180) nor height (P = 0.062) affected the metabolic cost of running. The metabolic cost of running was related to lower peak (β = 0.649; P = 0.001) and stance average (β = 0.772; P = 0.018) vertical ground reaction forces, prolonged ground contact times (β = -4.349; P = 0.012), and decreased leg stiffness (β = 0.071; P < 0.001) averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces (β = 0.007; P = 0.003) but was unrelated to stride kinematic symmetry (P ≥ 0.636). Therefore, prosthetic recommendations based on symmetric stride kinematics do not necessarily minimize the metabolic cost of running. Instead, an optimal prosthetic model, which improves overall biomechanics, minimizes the metabolic cost of running for athletes with unilateral transtibial amputations.NEW & NOTEWORTHY The metabolic cost of running for athletes with unilateral transtibial amputations depends on prosthetic model and is associated with lower peak and stance average vertical ground reaction forces, longer contact times, and reduced leg stiffness. Metabolic cost is unrelated to prosthetic stiffness, height, and stride kinematic symmetry. Unlike nonamputees who decrease leg stiffness with increased in-series surface stiffness, biological limb stiffness for athletes with unilateral transtibial amputations is positively correlated with increased in-series (prosthetic) stiffness.

Introduction: Receiving artificial limb, transtibial amputees are forced to use a kind of prosthetic feet to replace lost limb. Biomechanical Characteristics of unilateral transtibial amputees with various types of prosthetic feet during running have been studied. Although SACH and Dynamic-Response feet manufactured by Otto Bock are the most components used in Iran, examining function of these feet is less considered in locomotion activity .The purpose of this study was to survey the effect of SACH and Dynamic-Response feet on several kinetic variables in stance phase of running of individuals with unilateral transtibial amputees.\n\nMaterials and Methods: Eight male unilateral transtibial amputees participated in this study. Each subjects running in 12 meter runway three times at a speed of 2.5 meters per second with each feet. Kistler force plate and three-dimensional motion analysis Vicon system were used to collect kinetic data and control running speed respectively. Determination the effect of feet was used ANOVA with repeated measures in normal data and Friedman test in non-normal data (P &lt; 0.05).\n\nResults: The residual leg of individuals with unilateral transtibial amputees did not show shock absorption index (peak vertical ground reaction force during heel contact). Ground reaction force were significantly different between the SACH, Dynamic-Response and main feet (P &lt; 0.001) that SACH feet have greater ground reaction force rather than Dynamic-Response and main feet (P &lt; 0.001). There was no statistical difference vertical impulse between feet (P = 0.38).

These abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, SPO designates a Sports Physical Therapy Section poster presentation. J Orthop Sports Phys Ther 2011;41(1):A94–A101. doi:10.2519/jospt.2011.41.1.A94

BackgroundPeople with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds.MethodsWe analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance.ResultsUse of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet.ConclusionsUse of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

Whole-body angular momentum (H) influences fall risk, is tightly regulated during walking, and is primarily controlled by muscle force generation. People with transtibial amputations using passive-elastic prostheses typically have greater H compared with nonamputees. (1) Do people with unilateral transtibial amputations using passive-elastic prostheses have greater sagittal and frontal plane H ranges of motion during walking compared with nonamputees and compared with using powered prostheses? (2) Does use of powered ankle-foot prostheses result in equivalent H ranges in all planes of motion compared with nonamputees during walking as a result of normative prosthetic ankle power generation? Eight patients with a unilateral transtibial amputation and eight nonamputees walked 0.75, 1.00, 1.25, 1.50, and 1.75 m/s while we measured kinematics and ground reaction forces. We calculated H for participants using their passive-elastic prosthesis and a powered ankle-foot prosthesis and for nonamputees at each speed. Patients using passive-elastic prostheses had 32% to 59% greater sagittal H ranges during the affected leg stance phase compared with nonamputees at 1.00 to 1.75 m/s (p < 0.05). Patients using passive-elastic prostheses had 5% and 9% greater sagittal H ranges compared with using powered prostheses at 1.25 and 1.50 m/s, respectively (p < 0.05). Participants using passive-elastic prostheses had 29% and 17% greater frontal H ranges at 0.75 and 1.50 m/s, respectively, compared with nonamputees (p < 0.05). Surprisingly, patients using powered prostheses had 26% to 50% greater sagittal H ranges during the affected leg stance phase compared with nonamputees at 1.00 to 1.75 m/s (p < 0.05). Patients using powered prostheses also had 26% greater frontal H range compared with nonamputees at 0.75 m/s (p < 0.05). People with a transtibial amputation may more effectively regulate H at two specific walking speeds when using powered compared with passive-elastic prostheses. Our results support the hypothesis that an ankle-foot prosthesis capable of providing net positive work during the stance phase of walking reduces sagittal plane H; future studies are needed to validate our biomechanical findings with larger numbers of patients and should determine whether powered prostheses can decrease the risk of falls in patients with a transtibial amputation.

Dynamic balance during running using running-specific prostheses

Whole-body angular momentum during stair walking using passive and powered lower-limb prostheses*

Introduction This study was a double-blinded, randomized, repeated measures test of 14 persons with a unilateral transtibial amputation (TTA) walking and running on the Vari-Flex, Elite Blade, and the Re-Flex Rotate feet, with comparisons to persons without an amputation. The goal of the study was to compare ankle flexion, ankle moment, step length, ground reaction force (GRF), and metabolic cost of similar prosthetic feet for walking and running. Materials and Methods Marker-based motion capture, GRF, and metabolic data were recorded, whereas participants walked and ran on a treadmill at self-selected speeds. Data were statistically analyzed for significant differences between conditions and groups using a multivariate analysis, with post hoc Tukey's test for multiple comparisons. Results Plantarflexion was found to be significantly lower for prosthetic conditions than the contralateral and control conditions. Control participants had a shorter step length during walking. GRFs were generally lower for control and contralateral limbs. Heart rate, oxygen uptake, and self-selected speed were higher for TTAs than controls for walking and running. Conclusions Differences between prosthetic feet included in this study were minimal. Although significant differences between TTAs and controls were found, these differences were confounded by the difference in self-selected speeds.