Considering passive mechanical properties and patient user motor performance in lower limb prosthesis design optimization to enhance rehabilitation outcomes

Use of machine learning in the field of prosthetics and orthotics: A systematic narrative review

Although machine learning is not yet being used in clinical practice within the fields of prosthetics and orthotics, several studies on the use of prosthetics and orthotics have been conducted. We intend to provide relevant knowledge by conducting a systematic review of prior studies on using machine learning in the fields of prosthetics and orthotics. We searched the Medical Literature Analysis and Retrieval System Online (MEDLINE), Cochrane, Embase, and Scopus databases and retrieved studies published until July 18, 2021. The study included the application of machine learning algorithms to upper-limb and lower-limb prostheses and orthoses. The criteria of the Quality in Prognosis Studies tool were used to assess the methodological quality of the studies. A total of 13 studies were included in this systematic review. In the realm of prostheses, machine learning has been used to identify prosthesis, select an appropriate prosthesis, train after wearing the prosthesis, detect falls, and manage the temperature in the socket. In the field of orthotics, machine learning was used to control real-time movement while wearing an orthosis and predict the need for an orthosis. The studies included in this systematic review are limited to the algorithm development stage. However, if the developed algorithms are actually applied to clinical practice, it is expected that it will be useful for medical staff and users to handle prosthesis and orthosis.

Biomechanical accommodation to walking with an ankle-foot prosthesis: An exploratory analysis of novice users with transtibial limb loss within the first year of ambulation

BACKGROUND

The way in which a person with limb loss interacts with a prosthesis changes over time; however, there remains a lack of guidance for defining accommodation to walking with a prosthesis, limiting consistency and generalizability of research.

OBJECTIVE

To evaluate accommodations to walking with dynamic elastic response prosthetic ankle-foot devices among novice users with unilateral transtibial limb loss during the first year of ambulation.

STUDY DESIGN

This is a retrospective cohort study.

METHODS

Prosthetic and intact ankle-foot mechanical power profiles and mechanical work during step-to-step transitions were calculated using the Unified Deformable model for 22 male individuals with limb loss at five time points within the first year of independent ambulation (0, 2, 4, 6, and 12 months). Subjects walked at a self-selected walking velocity and controlled walking velocity (CWV). Subjective measures included the Prosthetic Evaluation Questionnaire and the 36-Item Short-Form Health Survey.

RESULTS

Self-selected walking velocity ranged from 1.24 ± 0.06 m/s at 0 month to 1.38 ± 0.04 m/s at 12 months, whereas CWV was 1.20 ± 0.02 m/s. At both velocities, positive work/peak power during prosthetic push-off trended upward until the 4-month time point. In addition, negative peak power during intact foot-strike seemed to qualitatively become less negative until 4 months. Positive work during intact push-off trended downward until 4 months at CWV, whereas positive peak power during intact push-off qualitatively became more positive at self-selected walking velocity.

CONCLUSIONS

These trends may partially indicate (biomechanical) accommodation to walking by appearance of a "plateau" at 4 months after initial ambulation with a prosthesis.

Biomechanical evaluation over level ground walking of user-specific prosthetic feet designed using the lower leg trajectory error framework

The walking pattern and comfort of a person with lower limb amputation are determined by the prosthetic foot’s diverse set of mechanical characteristics. However, most design methodologies are iterative and focus on individual parameters, preventing a holistic design of prosthetic feet for a user’s body size and walking preferences. Here we refined and evaluated the lower leg trajectory error (LLTE) framework, a novel quantitative and predictive design methodology that optimizes the mechanical function of a user’s prosthesis to encourage gait dynamics that match their body size and desired walking pattern. Five people with unilateral below-knee amputation walked over-ground at self-selected speeds using an LLTE-optimized foot made of Nylon 6/6, their daily-use foot, and a standardized commercial energy storage and return (ESR) foot. Using the LLTE feet, target able-bodied kinematics and kinetics were replicated to within 5.2% and 13.9%, respectively, 13.5% closer than with the commercial ESR foot. Additionally, energy return and center of mass propulsion work were 46% and 34% greater compared to the other two prostheses, which could lead to reduced walking effort. Similarly, peak limb loading and flexion moment on the intact leg were reduced by an average of 13.1%, lowering risk of long-term injuries. LLTE-feet were preferred over the commercial ESR foot across all users and preferred over the daily-use feet by two participants. These results suggest that the LLTE framework could be used to design customized, high performance ESR prostheses using low-cost Nylon 6/6 material. More studies with large sample size are warranted for further verification.

Characterizing the Gait of People With Different Types of Amputation and Prosthetic Components Through Multimodal Measurements: A Methodological Perspective

Prosthetic gait implies the use of compensatory motor strategies, including alterations in gait biomechanics and adaptations in the neural control mechanisms adopted by the central nervous system. Despite the constant technological advancements in prostheses design that led to a reduction in compensatory movements and an increased acceptance by the users, a deep comprehension of the numerous factors that influence prosthetic gait is still needed. The quantitative prosthetic gait analysis is an essential step in the development of new and ergonomic devices and to optimize the rehabilitation therapies. Nevertheless, the assessment of prosthetic gait is still carried out by a heterogeneous variety of methodologies, and this limits the comparison of results from different studies, complicating the definition of shared and well-accepted guidelines among clinicians, therapists, physicians, and engineers. This perspective article starts from the results of a project funded by the Italian Worker's Compensation Authority (INAIL) that led to the generation of an extended dataset of measurements involving kinematic, kinetic, and electrophysiological recordings in subjects with different types of amputation and prosthetic components. By encompassing different studies published along the project activities, we discuss the specific information that can be extracted by different kinds of measurements, and we here provide a methodological perspective related to multimodal prosthetic gait assessment, highlighting how, for designing improved prostheses and more effective therapies for patients, it is of critical importance to analyze movement neural control and its mechanical actuation as a whole, without limiting the focus to one specific aspect.

Effects of women’s footwear on the mechanical function of heel-height accommodating prosthetic feet

The loaded mechanical function of transtibial prostheses that result from the clinical assembly, tuning, and alignment of modular prosthetic components can directly influence an end user’s biomechanics and overall mobility. Footwear is known to affect prosthesis mechanical properties, and while the options of footwear are limited for most commercial feet due to their fixed geometry, there exists a selection of commercial prosthetic feet that can accommodate a moderate rise in heel height. These feet are particularly relevant to women prosthesis users who often desire to don footwear spanning a range of heel heights. The aim of this study was to assess the effects of adding women’s footwear (flat, trainer, 5.08 cm heel) on the mechanical properties (deformation and energy efficiency) of four models of heel-height accommodating prosthetic feet. Properties were measured through loading-unloading at simulated initial contact, midstance and terminal stance orientations with a universal materials test system, and statistically compared to a barefoot condition. Results suggest that the addition of footwear can alter the level of foot deformation under load, which may be a function of the shoe and alignment. Moreover, while each foot displayed different amounts of energy storage and return, the addition of footwear yielded similar levels of energy efficiency across foot models. Overall, prosthesis users who don shoes of varying heel heights onto adjustable prosthetic feet and their treating clinicians should be aware of the potential changes in mechanical function that could affect the user experience.

Deleterious Musculoskeletal Conditions Secondary to Lower Limb Loss: Considerations for Prosthesis-Related Factors

Significance: The intent of this work was to summarize the existing evidence of, and highlight knowledge gaps specific to, prosthetic devices/componentry and training regimes, particularly in the context of the human-device interaction and deleterious musculoskeletal conditions secondary to lower limb loss. Recent Advances: With the recent and evolving technological advancements in prostheses, there are numerous devices available to individuals with lower limb loss. Current literature demonstrates the importance of expanding the knowledge of all prosthetic device-specific factors and the significance of proper prescription, fit, and alignment, along with adequate device-/activity-specific training, to enhance human-device interaction, reduce gait abnormalities and compensatory motions, and as a result, mitigate risk for secondary musculoskeletal conditions. Critical Issues: Inadequate device prescription, fit, alignment, and training are evident owing to the lack of knowledge or awareness of the many device-specific properties and factors, leading to suboptimal use, as well as, biomechanical compensations, which collectively and adversely affect the function, activity level, and overall health of the prosthesis user. Future Directions: To maximize optimal outcomes after lower limb loss, it is essential to better appreciate the factors that affect both prosthesis use and satisfaction, particularly any modifiable factors that might be targeted in rehabilitation interventions such as device prescription, fit/alignment, and training regimes. A better understanding of such device-specific factors will help enhance the human-device interaction and resulting functional performance, thereby reducing secondary musculoskeletal conditions, allowing for the readiness of the fighting force (return-to-duty/redeployment) and/or improved reintegration into civilian society/work, and overall enhancing quality of life after lower limb loss.

Focusing research efforts on the unique needs of women prosthesis users

Introduction

Women with lower limb loss represent a relevant and growing patient cohort with unique rehabilitation needs. These needs are emphasized in a growing body of literature and the most recent Veteran Affairs/Department of Defense clinical practice guidelines.

Prosthetics Challenges

Women with limb loss experience greater dissatisfaction with prosthetic fit, appearance, and types of footwear they can use. There is a lack of prosthetics solutions to accommodate the desire of women to wear different footwear varieties, including high heels. The choice to wear a variety of footwear is important to attire and hence community participation. Despite these recognized challenges, women are still underserved in prosthetics research, which limits available information to guide the rehabilitation process.

Research Initiatives

This narrative review describes considerations of lower limb prosthesis prescription and use by women, and examples of current research to address these topics. Research efforts are beginning to explore factors that contribute to prosthetics prescription for women, and design creative prosthetics solutions to expand the range of available footwear options. Research is still needed to characterize the types of footwear women with limb loss prefer to use, and the effects of prosthesis designs, footwear, and lower limb loss on women mobility outcomes and community participation.

Conclusions

Through targeted research initiatives, scientists and clinicians can be responsive to the specific needs of women to provide evidence-based guidelines for prosthetics prescription and improve the patient-centered care after limb loss.

Analysis of Continuously Varying Kinematics for Prosthetic Leg Control Applications

Powered prosthetic legs can improve the quality of life for people with transfemoral amputations by providing net positive work at the knee and ankle, reducing the effort required from the wearer, and making more tasks possible. However, the controllers for these devices use finite state machines that limit their use to a small set of pre-defined tasks that require many hours of tuning for each user. In previous work, we demonstrated that a continuous parameterization of joint kinematics over walking speeds and inclines provides more accurate predictions of reference kinematics for control than a finite state machine. However, our previous work did not account for measurement errors in gait phase, walking speed, and ground incline, nor subject-specific differences in reference kinematics, which occur in practice. In this work, we conduct a pilot experiment to characterize the accuracy of speed and incline measurements using sensors onboard our prototype prosthetic leg and simulate phase measurements on ten able-bodied subjects using archived motion capture data. Our analysis shows that given demonstrated accuracy for speed, incline, and phase estimation, a continuous parameterization provides statistically significantly better predictions of knee and ankle kinematics than a comparable finite state machine, but both methods' primary source of predictive error is subject deviation from average kinematics.

Using a Simple Walking Model to Optimize Transfemoral Prostheses for Prosthetic Limb Stability-A Preliminary Study

The interaction between the prescribed prosthetic knee and foot is critical to the safety of transfemoral prosthesis users primarily during the stance phase of the gait, when knee buckling can result in a fall. Nonetheless, there is still a need for standardized approaches to quantify the effects of prosthetic component interactions and associated mechanical function on user gait biomechanics. A numerical model was defined to simulate sagittal plane prosthetic limb stance based on a single inverted pendulum and predict effects of prosthetic knee alignment and foot stiffness on knee moment to identify optimal solutions. Model validation against laboratory gait data suggests it is appropriate to preliminary simulate prosthetic gait during single-limb support, when prosthetic knee stability may be most at risk given reliance on the prosthetic limb and proximal anatomy, but only for knees with flexion smaller than 4°. Model predictions identify a solution space containing those combinations of knee alignment and foot stiffness (via roll-over shape radius) guaranteeing knee stability in early and mid- single-limb support, whilst facilitating knee break at the end of it. Specifically, a posterior to in-line knee alignment should be combined with low to medium ankle-foot stiffness, whereas anterior knee alignments and rigid feet should likely be avoided. Clinicians can use these solution spaces to optimize transfemoral prostheses including knees with little to no change in stance flexion, ensuring the safety of users. Model prediction can further inform in-vivo investigations on commercial device interactions, providing evidence for future Clinical Practice Guidelines on transfemoral prostheses design.

Predicting Individualized Joint Kinematics over a Continuous Range of Slopes and Speeds

Individuality in clinical gait analysis is often quantified by an individual's kinematic deviation from the norm, but it is unclear how these deviations generalize across different walking speeds and ground slopes. Understanding individuality across tasks has important implications in the tuning of prosthetic legs, where clinicians have limited time and resources to personalize the kinematic motion of the leg to therapeutically enhance the wearer's gait. This study seeks to determine an efficient way to predictively model an individual's kinematics over a continuous range of slopes and speeds given only one personalized task at level ground. We were able to predict the kinematics of able-bodied individuals at a wide variety of conditions that were not specifically tuned. Applied to 10 human subjects, the individualization method reduced the RMSE between the model and subject's kinematics over all tasks by an average of 2% (max 52%) at the ankle, 27% (max 59%) at the knee, and 45% (max 83%) at the hip. Our results indicate that knowing how an individual subject differs from the average subject at level ground alone is enough information to improve kinematic predictions across all tasks. This research offers a new method for personalizing robotic prosthetic legs over a variety of tasks without the need of an engineer, which could make these complex devices more clinically viable.

Ambulatory Status following Major Lower Extremity Amputation

BACKGROUND

The ability to ambulate following major lower extremity amputation, either below (BKA) or above knee (AKA), is a major concern for all prospective patients. This study analyzed ambulatory rates and risk factors for nonambulation in patients undergoing a major lower extremity amputation.

METHODS

A retrospective review of 811 patients who underwent BKA or AKA at our institution between January 2009 and December 2014 was conducted. Demographic information and co-morbid conditions, including the patients' functional status prior to surgery, at 6 months, and at latest follow up were recorded. Following exclusion criteria, 538 patients were included. Patients who were either independent or used an assistive device were considered ambulatory, while those who were completely wheelchair-dependent or bed-bound were considered nonambulatory.

RESULTS

Pre-operatively, 83.1% of BKA patients were ambulatory, significantly more so than those undergoing AKA (44.9%, P < 0.0001). At 6-month follow-up these percentages dropped to 58.0% and 25.2%, respectively, for all patients. For patients who were ambulatory pre-operatively, 182/246 (73.9%) of BKA and 32/51 (62.7%) of AKA remained so post-amputation. Of those patients with both 6-month and greater than 1-year follow-up, there was no change in ambulatory status between the 2 time periods. On multivariable logistic regression, age greater than 70 years and female sex were associated with nonambulation post-operatively (P = 0.001, P = 0.015, respectively). None of the co-morbid conditions recorded (diabetes, renal insufficiency, end-stage renal disease, peripheral vascular disease, or body mass index > 35) was found to have a statistically significant correlation with post-operative ambulation using multivariable analysis.

CONCLUSIONS

The majority of ambulatory patients undergoing a major amputation were able to remain ambulatory. Patients who failed to ambulate 6 months after their amputation, failed to resume ambulating. Age greater than 70 and female sex were found to have a statistically significant association with becoming nonambulatory following surgery.

Perturbation recovery during walking is impacted by knowledge of perturbation timing in below-knee prosthesis users and non-impaired participants

Previous research found that below-knee prosthesis users proactively increase their lateral margin-of-stability on their impaired side in anticipation of an impending perturbation when the timing is predictable and potentially directed toward the impaired limb. While knowledge of perturbation timing and direction influences proactive strategies, the consequences of such knowledge and anticipatory behavior on recovery from perturbations is unclear. This study characterized center-of-mass (CoM) dynamics of below-knee prosthesis users and non-impaired controls following a lateral perturbation when the perturbation direction is known but a priori knowledge of the timing of perturbation is either known or unknown. Across groups, CoM displacement during perturbation exposure increased when directed towards the impaired or non-dominant limb with no influence of timing knowledge. In addition, peak CoM displacement was less with known timing irrespective of the perturbation direction. Generally, the CoM displacement during perturbation exposure correlated well with the CoM medial-lateral velocity during unperturbed walking, supporting evidence that human response dynamics to lateral perturbations are influenced by the instantaneous state of the body's momentum.

A more compliant prosthetic foot better accommodates added load while walking among Servicemembers with transtibial limb loss

Selecting an optimal prosthetic foot is particularly challenging for highly active individuals with limb loss, such as military personnel, who need to seamlessly perform a variety of demanding activities/tasks (often with and without external loads) while minimizing risk of musculoskeletal injuries over the longer term. Here, we expand on prior work by comparing biomechanical and functional outcomes in two prosthetic feet with the largest differences in mechanical response to added load (i.e., consistently "Compliant" and "Stiff" forefoot properties). In each foot, fourteen male Servicemembers with unilateral transtibial limb loss (from trauma) completed instrumented gait analyses in all combinations of two loading conditions (with and without 22 kg weighted vest) and two walking speeds (1.34 and 1.52 m/s), as well as the Prosthesis Evaluation Questionnaire. With the Stiff foot, sound limb peak loading was 2% smaller (p = 0.043) in the loaded versus unloaded condition, but similar between loading conditions in the Compliant foot (note, the Stiff foot was associated with larger loads, overall). Independent of load or walking speed, the Compliant (versus Stiff) foot provided 67.9% larger (p < 0.001) prosthetic push-off, 17.7% larger (p = 0.01) roll-over shape radii, and was subjectively favored by 10 participants. A more Compliant versus Stiff prosthetic foot therefore appears to better accommodate walking with and without added load, and reinforce the notion that mechanical properties of prosthetic feet should be considered for near-term performance and longer-term (joint) health.

Design Optimization in Lower Limb Prostheses: A Review

This paper aims to develop a knowledge base and identify the promising research pathways toward designing lower limb prostheses for optimal biomechanical and clinical outcomes. It is based on the literature search representing the state of the art in the lower limb prosthesis joint design and biomechanical analysis. Current design solutions are organized in terms of fulfilling four key functional roles: body support, propulsion, task flexibility, and loading relief. Biomechanical analyses of these designs reveal that the hypothesized outcomes are not consistently observed. We suggest that these outcomes may be improved by incorporating tools that can predict user performance metrics to optimize the device during the initial design process. We also note that the scope of the solution space of most current designs is limited by focusing on the anthropomorphic design approaches that do not account for the person's altered anatomy post-amputation. The effects of the prosthetic joint behavior on whole-body gait biomechanics and user experience are likewise under-explored. Two research paths to support the goal of better predicting the user outcomes are proposed: experimental parameterization of designs and model-based simulations. However, while work in these areas has introduced promising new possibilities, connecting both to improve real-world performance remains a challenge.

Does Decreasing Below-Knee Prosthesis Pylon Longitudinal Stiffness Increase Prosthetic Limb Collision and Push-Off Work During Gait?

Investigations have begun to connect leg prosthesis mechanical properties and user outcomes to optimize prosthesis designs for maximizing mobility. To date, parametric studies have focused on prosthetic foot properties, but not explicitly longitudinal stiffness that is uniquely modified through shock-absorbing pylons. The linear spring function of these devices might affect work performed on the body center-of-mass during walking. This study observed the effects of different levels of pylon stiffness on individual limb work of unilateral below-knee prosthesis users walking at customary and fast speeds. Longitudinal stiffness reductions were associated with minimal increase in prosthetic limb collision and push-off work, but inconsistent changes in sound limb work. These small and variable changes in limb work did not suggest an improvement in mechanical economy due to reductions in stiffness. Fast walking generated greater overall center-of-mass work demands across stiffness conditions. Results indicate limb work asymmetry as the prosthetic limb experienced on average 61% and 36% of collision and push-off work, respectively, relative to the sound limb. A series spring model to estimate residuum and pylon stiffness effects on prosthesis energy storage suggested that minimal changes to limb work may be due to influences of the residual limb which dominate the system response.

Fall Prevalence and Contributors to the Likelihood of Falling in Persons With Upper Limb Loss

BACKGROUND

Arms are important for locomotor stability and preventing falls by controlling whole-body angular momentum, redirecting the body's center of mass, and providing support to arrest descent. Hence, upper limb loss (ULL) can increase fall risk. However, the prevalence of falls and factors that influence fall risk have not previously been reported for people with ULL.

OBJECTIVE

This study quantified fall prevalence in persons with ULL at or proximal to the wrist and identified clinical factors that contributed to the likelihood of falling.

DESIGN

This was a cross-sectional study.

METHODS

Factors including body and health characteristics, activity level, fall history, prosthesis use, and balance confidence were determined for persons with ULL proximal to the wrist using an online survey. Logistic regression analyses assessed the contribution of these factors to the classification of fallers (≥2 falls in previous year) and nonfallers.

RESULTS

A percentage (28.6%) of participants (n = 105) reported experiencing 2 or more falls in the past year. The regression model (R2 = 0.473) correctly classified 84.5% of cases and indicated that increased likelihood of falling was significantly influenced by reduced balance confidence, use of upper limb prostheses, and reduced physical capabilities.

LIMITATIONS

Data were collected online from a convenience sample, and fall classification was based on retrospective data.

CONCLUSIONS

Falls in persons with ULL are prevalent, suggesting that clinicians should use screening methods to identify at-risk individuals. Balance confidence, use of upper limb prostheses, and perceived physical capabilities could be useful screening metrics. Research is warranted to better understand the factors that underlie fall risk in persons with ULL and the efficacy of therapeutic interventions capable of mitigating fall risk.

Amputee perception of prosthetic ankle stiffness during locomotion

Background

Prosthetic feet are spring-like, and their stiffness critically affects the wearer’s stability, comfort, and energetic cost of walking. Despite the importance of stiffness in ambulation, the prescription process often entails testing a limited number of prostheses, which may result in patients receiving a foot with suboptimal mechanics. To understand the resolution with which prostheses should be individually optimized, we sought to characterize below-knee prosthesis users’ psychophysical sensitivity to prosthesis stiffness.

Methods

We used a novel variable-stiffness ankle prosthesis to measure the repeatability of user-selected preferred stiffness, and implemented a psychophysical experiment to characterize the just noticeable difference of stiffness during locomotion.

Results

All eight subjects with below-knee amputation exhibited high repeatability in selecting their Preferred Stiffness (mean coefficient of variation: 14.2 ± 1.7%) and were able to correctly identify a 7.7 ± 1.3% change in ankle stiffness (with 75% accuracy).

Conclusions

This high sensitivity suggests prosthetic foot stiffness should be tuned with a high degree of precision on an individual basis. These results also highlight the need for a pairing of new robotic prescription tools and mechanical characterizations of prosthetic feet.

Proactive Locomotor Adjustments Are Specific to Perturbation Uncertainty in Below-Knee Prosthesis Users

Sensory-motor deficits associated with below-knee amputation impair reactions to external perturbations. As such, below-knee prosthesis users rely on proactive control strategies to maintain locomotor stability. However, there are trade-offs (metabolic, comfort, etc.) associated with proactive strategies. We hypothesize that because proactive control strategies are costly, prosthesis users and non-impaired participants will use a priori knowledge (timing, direction) of an impending lateral perturbation to make specific gait adaptations only when the timing of the perturbation is known and the adaptation can be temporally-limited. This hypothesis was partially supported. When the perturbation timing was predictable, only prosthesis users, and only on their impaired side, increased their lateral margin of stability during the steps immediately preceding the perturbation when perturbation direction was either unknown or known to be directed towards their impaired side. This strategy should reduce the likelihood of requiring a corrective step to maintain stability. However, neither group exhibited substantial proactive adaptations compared to baseline walking when perturbation timing was unpredictable, independent of perturbation direction knowledge. The absence of further proactive stabilization behaviors observed in prosthesis users in anticipation of a certain but temporally unpredictable perturbation may be partially responsible for impaired balance control.

Segmental contributions to sagittal-plane whole-body angular momentum when using powered compared to passive ankle-foot prostheses on ramps

Understanding the effects of an assistive device on dynamic balance is crucial, particularly for robotic leg prostheses. Analyses of dynamic balance commonly evaluate the range of whole-body angular momentum (H). However, the contributions of individual body segments to overall H throughout gait may yield futher insights, specifically for people with transtibial amputation using powered prostheses. We evaluated segment contributions to H using Statistical Parametric Mapping to assess the effects of prosthesis type (powered vs passive) and ramp angle on segmental coordination. The slope main effect was significant in all segments, the prosthesis main effect was significant in the prosthetic leg (device and residuum) and trunk, and the slope by prosthesis interaction effect was significant in the prosthetic leg and trunk. The magnitude of contributions to sagittal-plane H from the prosthetic leg was larger when using the powered prosthesis. The trunk contributed more positive (backward) H after prosthetic leg toe-off when using the powered prosthesis on inclines, similar to the soleus muscle. However, trunk contributions to H on declines were similar when using a powered and passive prosthesis, suggesting that the powered prosthesis may not replicate soleus function when walking downhill. Our novel assessment method evaluated robotic leg prostheses not only based on local joint mechanics, but also considering whole-body biomechanics.