Andrew Sawers

Outcomes associated with the use of microprocessor-controlled prosthetic knees among individuals with unilateral transfemoral limb loss: A systematic review

Microprocessor-controlled prosthetic knees (MPKs) have been developed as an alternative to non-microprocessor-controlled knees (NMPKs) to address challenges facing individuals with lower-limb loss. A body of scientific literature comparing MPKs and NMPKs exists but has yet to be critically appraised. Therefore, we conducted a systematic review to examine outcomes associated with the use of these interventions among individuals with transfemoral limb loss. A search of biomedical databases identified 241 publications, of which 27 met the inclusion and exclusion criteria and were reviewed for methodological quality and content. We developed 28 empirical evidence statements (EESs) in 9 outcome categories (metabolic energy expenditure, activity, cognitive demand, gait mechanics, environmental obstacle negotiation, safety, preference and satisfaction, economics, and health and quality of life) based on findings in the literature. The level of evidence supporting these EESs varied due to quantity, quality, and consistency of the results. EESs supported by a moderate level of evidence that noted significant differences between MPKs and NMPKs were derived in five of the nine outcome categories. The results from this review suggest that evidence exists to inform clinical practice and that additional research is needed to confirm existing evidence and better understand outcomes associated with the use of NMPKs and MPKs.

Long-term training modifies the modular structure and organization of walking balance control

How does long-term training affect the neural control of movements? Here we tested the hypothesis that long-term training leading to skilled motor performance alters muscle coordination during challenging, as well as nominal everyday motor behaviors. Using motor module (a.k.a., muscle synergy) analyses, we identified differences in muscle coordination patterns between professionally trained ballet dancers (experts) and untrained novices that accompanied differences in walking balance proficiency assessed using a challenging beam-walking test. During beam walking, we found that experts recruited more motor modules than novices, suggesting an increase in motor repertoire size. Motor modules in experts had less muscle coactivity and were more consistent than in novices, reflecting greater efficiency in muscle output. Moreover, the pool of motor modules shared between beam and overground walking was larger in experts compared with novices, suggesting greater generalization of motor module function across multiple behaviors. These differences in motor output between experts and novices could not be explained by differences in kinematics, suggesting that they likely reflect differences in the neural control of movement following years of training rather than biomechanical constraints imposed by the activity or musculoskeletal structure and function. Our results suggest that to learn challenging new behaviors, we may take advantage of existing motor modules used for related behaviors and sculpt them to meet the demands of a new behavior.

Perspectives on human-human sensorimotor interactions for the design of rehabilitation robots.

Physical interactions between patients and therapists during rehabilitation have served as motivation for the design of rehabilitation robots, yet we lack a fundamental understanding of the principles governing such human-human interactions (HHI). Here we review the literature and pose important open questions regarding sensorimotor interaction during HHI that could facilitate the design of human-robot interactions (HRI) and haptic interfaces for rehabilitation. Based on the goals of physical rehabilitation, three subcategories of sensorimotor interaction are identified: sensorimotor collaboration, sensorimotor assistance, and sensorimotor education. Prior research has focused primarily on sensorimotor collaboration and is generally limited to relatively constrained visuomotor tasks. Moreover, the mechanisms by which performance improvements are achieved during sensorimotor cooperation with haptic interaction remains unknown. We propose that the effects of role assignment, motor redundancy, and skill level in sensorimotor cooperation should be explicitly studied. Additionally, the importance of haptic interactions may be better revealed in tasks that do not require visual feedback. Finally, cooperative motor tasks that allow for motor improvement during solo performance to be examined may be particularly relevant for rehabilitation robotics. Identifying principles that guide human-human sensorimotor interactions may lead to the development of robots that can physically interact with humans in more intuitive and biologically inspired ways, thereby enhancing rehabilitation outcomes.

The Potential for Error With Use of Inverse Dynamic Calculations in Gait Analysis of Individuals With Lower Limb Loss: A Review of Model Selection and Assumptions

Lower limb joint kinetics are among the most commonly reported values after instrumented gait analysis and are typically estimated via inverse dynamic calculations. These calculations require, among other things, the selection of a link-segment model that is representative of the subject being tested. In applying inverse dynamics calculations to a standard link-segment model, several assumptions are commonly made in an effort to simplify the calculations. These assumptions regarding the link-segment model are derived from conventional anatomy and physiology and therefore may not be valid when applied to individuals with lower limb loss because their unique anatomical characteristics and the design of lower limb prosthetic componentry may not be accurately accounted for. This article reviews the validity of applying these common assumptions to the analysis of individuals with lower limb loss, with the goal of enabling prosthetists to better judge the quality and accuracy of empirical research findings by furthering their understanding of inverse dynamic theory and its application to the quantitative gait analysis of individuals with lower limb loss.

Beam walking can detect differences in walking balance proficiency across a range of sensorimotor abilities

The ability to quantify differences in walking balance proficiency is critical to curbing the rising health and financial costs of falls. Current laboratory-based approaches typically focus on successful recovery of balance while clinical instruments often pose little difficulty for all but the most impaired patients. Rarely do they test motor behaviors of sufficient difficulty to evoke failures in balance control limiting their ability to quantify balance proficiency. Our objective was to test whether a simple beam-walking task could quantify differences in walking balance proficiency across a range of sensorimotor abilities. Ten experts, ten novices, and five individuals with transtibial limb loss performed six walking trials across three different width beams. Walking balance proficiency was quantified as the ratio of distance walked to total possible distance. Balance proficiency was not significantly different between cohorts on the wide-beam, but clear differences between cohorts on the mid and narrow-beams were identified. Experts walked a greater distance than novices on the mid-beam (average of 3.63±0.04m verus 2.70±0.21m out of 3.66m; p=0.009), and novices walked further than amputees (1.52±0.20m; p=0.03). Amputees were unable to walk on the narrow-beam, while experts walked further (3.07±0.14m) than novices (1.55±0.26m; p=0.0005). A simple beam-walking task and an easily collected measure of distance traveled detected differences in walking balance proficiency across sensorimotor abilities. This approach provides a means to safely study and evaluate successes and failures in walking balance in the clinic or lab. It may prove useful in identifying mechanisms underlying falls versus fall recoveries.

Beyond componentry: How principles of motor learning can enhance locomotor rehabilitation of individuals with lower limb loss—A review

Relatively little attention has been given to the use of well-established motor learning strategies to enable individuals with lower limb loss to effectively and safely learn to walk with their prostheses in the home and community. Traditionally, such outcomes have been pursued by focusing on the design and function of a patients prosthesis, rather than on how he or she should learn to use it. The use of motor learning strategies may enhance physical rehabilitation outcomes among individuals with lower limb loss. This review explores these motor learning strategies and ways in which they can be applied to the physical rehabilitation of individuals with lower limb loss and highlights some of the challenges to their implementation, as well as unanswered research questions.

Regulation of whole-body frontal plane balance varies within a step during unperturbed walking

This study sought to determine whether the need to actively control lateral balance is consistent within a step. Variability of the frontal plane COM-Ankle angle was calculated over 50 strides at discrete gait events for twenty-one healthy young adults to quantify active control of lateral balance within a step. Frontal plane COM-Ankle angle variability was found to vary significantly between all gait events, decreasing progressively within a step. This suggests that active control of lateral balance varies significantly within a step and that the greatest degree of active control occurs at heel-strike. The increased active control of lateral balance during heel-strike indicates a degree of preparation to ensure sufficient lateral balance control prior to more challenging events. These results provide insight into the mechanisms of lateral balance control and how to assess and treat locomotor balance control impairments.

Trajectory of the center of rotation in non-articulated energy storage and return prosthetic feet

Non-articulated energy storage and return prosthetic feet lack any true articulation or obvious point of rotation. This makes it difficult to select a joint center about which to estimate their kinetics. Despite this absence of any clear point of rotation, methods for estimating the kinetic performance of this class of prosthetic feet typically assume that they possess a fixed center of rotation and that its location is well approximated by the position of the contralateral lateral malleolus. To evaluate the validity of this assumption we used a finite helical axis approach to determine the position of the center of rotation in the sagittal plane for a series of non-articulated energy storage and return prosthetic feet. We found that over the course of stance phase, the sagittal finite helical axis position diverged markedly from the typically assumed fixed axis location. These results suggest that researchers may need to review center of rotation assumptions when assessing prosthetic foot kinetics, while clinicians may need to reconsider the criteria by which they prescribe these prosthetic feet.

Small forces that differ with prior motor experience can communicate movement goals during human-human physical interaction

BackgroundPhysical interactions between two people are ubiquitous in our daily lives, and an integral part of many forms of rehabilitation. However, few studies have investigated forces arising from physical interactions between humans during a cooperative motor task, particularly during overground movements. As such, the direction and magnitude of interaction forces between two human partners, how those forces are used to communicate movement goals, and whether they change with motor experience remains unknown. A better understanding of how cooperative physical interactions are achieved in healthy individuals of different skill levels is a first step toward understanding principles of physical interactions that could be applied to robotic devices for motor assistance and rehabilitation.MethodsInteraction forces between expert and novice partner dancers were recorded while performing a forward-backward partnered stepping task with assigned “leader” and “follower” roles. Their position was recorded using motion capture. The magnitude and direction of the interaction forces were analyzed and compared across groups (i.e. expert-expert, expert-novice, and novice-novice) and across movement phases (i.e. forward, backward, change of direction).ResultsAll dyads were able to perform the partnered stepping task with some level of proficiency. Relatively small interaction forces (10–30N) were observed across all dyads, but were significantly larger among expert-expert dyads. Interaction forces were also found to be significantly different across movement phases. However, interaction force magnitude did not change as whole-body synchronization between partners improved across trials.ConclusionsRelatively small interaction forces may communicate movement goals (i.e. “what to do and when to do it”) between human partners during cooperative physical interactions. Moreover, these small interactions forces vary with prior motor experience, and may act primarily as guiding cues that convey information about movement goals rather than providing physical assistance. This suggests that robots may be able to provide meaningful physical interactions for rehabilitation using relatively small force levels.

Outcomes Associated with the Use of Microprocessor-Controlled Prosthetic Knees among Individuals with Unilateral Transfemoral Limb Loss: A Systematic Review

ABSTRACT Microprocessor-controlled prosthetic knees (MPKs) have been developed as an alternative to non-microprocessor-controlled knees (NMPKs) to address challenges facing individuals with lower limb loss. A body of scientific literature comparing MPKs and NMPKs exists, but has yet to be critically appraised. Therefore, a systematic review was conducted to examine outcomes associated with use of these interventions among individuals with transfemoral limb loss. A search of biomedical databases identified 241 publications. Twenty-seven met the inclusion/exclusion criteria and were reviewed for methodological quality and content. Twenty-eight evidence statements, in nine outcome categories (Metabolic Energy Expenditure, Activity, Cognitive Demand, Gait Mechanics, Environmental Obstacle Negotiation, Safety, Preference & Satisfaction, Economics, and Health & Quality of Life) were developed based on findings in the literature. The level of evidence supporting these statements varied due to quantity, quality, and consistency of the results in the literature. Evidence statements supported by a moderate level of evidence that noted significant differences between MPKs and NMPKs were derived in five of the nine outcome categories. The results from this review suggest that evidence exists to inform clinical practice, and that additional research is needed to confirm existing evidence and better understand outcomes associated with use of NMPKs and MPKs.