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Introduction
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August 2020 - present
August 2020 - present
June 2016 - July 2020
Publications
Publications (112)
Background
Two-thirds of individuals with amputations in large cities are older. Our study identifies how lower-limb amputation alters dynamic balance, muscle excitation and their relationship across samples of older individuals at multiple walking speeds. We hypothesized that individuals with amputation would express different relationships betwee...
The muscular restructuring and loss of function that occurs during a transfemoral amputation surgery has a great impact on the gait and mobility of the individual. The hip of the residual limb adopts a number of functional roles that would previously be controlled by lower joints. In the absence of active plantar flexors, swing initiation must be a...
The muscular remodeling that occurs during a transfemoral amputation surgery and subsequent long-term use of mechanically-passive prostheses have significant impacts on the mobility and gait pattern of the patient. At toe-off and during the subsequent swing phase, this behavior is characterized by increased hip flexion moment and power provided by...
Soft exosuits hold promise as assistive technology for people with gait deficits owing to a variety of causes. A key aspect of providing useful assistance is to keep the human user at the center of all considerations made in the design, configuration, and prescribed use of an assistive device. This work details a method for informing the configurat...
Background
Patient-reported outcomes are commonly used to assess patient symptoms. The effect of specific hip pathology on relationships between perceived and objectively measured symptoms remains unclear. The purpose of this study was to evaluate differences of function and pain in patients with FAIS and DDH, to assess the correlation between perc...
Background: Total hip arthroplasty (THA) for the treatment of hip dysplasia, which disproportionately impacts the younger population, has been shown to be an effective intervention to restore functionality and improve quality of life. However, it is unclear whether these outcomes can be just as beneficial in treating hip dysplasia when it presents...
Objective:
Volitional control systems for powered prostheses require the detection of user intent to operate in real life scenarios. Ambulation mode classification has been proposed to address this issue. However, these approaches introduce discrete labels to the otherwise continuous task that is ambulation. An alternative approach is to provide u...
Human ambulation is typically characterized during steady-state isolated tasks (e.g., walking, running, stair ambulation). However, general human locomotion comprises continuous adaptation to the varied terrains encountered during activities of daily life. To fill an important gap in knowledge that may lead to improved therapeutic and device interv...
Lower-limb powered prostheses can provide users with volitional control of ambulation. To accomplish this goal, they require a sensing modality that reliably interprets user intention to move. Surface electromyography (EMG) has been previously proposed to measure muscle excitation and provide volitional control to upper- and lower-limb powered pros...
Background
Patient-reported outcomes are commonly used to assess patient symptoms and track post-operative improvements. The effect that specific hip pathology has on the relationship between perceived and objectively measured symptoms remains unclear. The purpose of this study was (1) to evaluate differences of function and pain in FAIS and DDH pa...
Many people struggle with mobility impairments due to lower limb amputations. To participate in society, they need to be able to walk on a wide variety of terrains, such as stairs, ramps, and level ground. Current lower limb powered prostheses require different control strategies for varying ambulation modes, and use data from mechanical sensors wi...
Objective:
To determine which radiographic measures used to define the severity of hip dysplasia are associated with hip joint translation and to investigate relationships between position, body mass index, and joint translation.
Materials and methods:
This is a cross-sectional retrospective study evaluating 10 validated radiographic measures of...
Walking speed is an important indicator of health and function across a variety of populations. Faster walking requires both larger propulsive and braking forces, though of the two, propulsive force generation has been far more extensively investigated. This study seeks to develop and validate a quasi-static biomechanical model of braking force in...
Human ambulation is typically characterized during steady-state isolated tasks (e.g., walking, running, stair ambulation). However, general human locomotion comprises continuous adaptation to the varied terrains encountered during activities of daily life. To fill an important gap in knowledge that may lead to improved therapeutic and device interv...
There exists motor redundancy during human gait that allows individuals to perform the same task in different observable ways (i.e., with varied styles). However, how differences in observable walking mechanics depend on unique and underlying biomechanical objectives is unclear. As an example, these objectives could include metabolic energy consump...
Exosuits are close-fitting devices, which are meant to be worn without restricting the motion of the user in the way that a rigid device would. These soft devices augment lower-limb biomechanics by using flexible, joint-spanning linear elements that are actuated to create moments about the spanned joints, effectively using the human body as the mec...
Fundamental knowledge in activity recognition of individuals with motor disorders such as Parkinson’s disease (PD) has been primarily limited to detection of steady-state/static tasks (e.g., sitting, standing, walking). To date, identification of non-steady-state locomotion on uneven terrains (stairs, ramps) has not received much attention. Further...
Research on robotic lower-limb assistive devices over the past decade has generated autonomous, multiple degree-of-freedom devices to augment human performance during a variety of scenarios. However, the increase in capabilities of these devices is met with an increase in the complexity of the overall control problem and requirement for an accurate...
Advances in powered assistive device technology, including the ability to provide net mechanical power to multiple joints within a single device, have the potential to dramatically improve the mobility and restore independence to their users. However, these devices rely on the ability of their users to continuously control multiple powered lower-li...
Anticipated and unanticipated directional changes are commonplace in daily lives. The need for dynamic balance is amplified when these transitions are performed in an unplanned (i.e., unanticipated) manner. In this study, we used predictive simulations and optimal control constructs to test a method for reshaping dynamic balance of unanticipated cr...
Stair ambulation is commonplace in daily living activities, yet biomechanically more challenging compared to level-ground walking. With reduced lower-limb muscle strength and increased rigidity of extremities, people with Parkinson's disease (PD) experience impaired balance and higher incidence of falls each year. However, the regulation of whole-b...
Sonomyography, or dynamic ultrasound imaging of skeletal muscle, has gained significant interest in rehabilitation medicine. Previously, correlations relating sonomyography features of muscle contraction, including muscle thickness, pennation angle, angle between aponeuroses and fascicle length, to muscle force production, strength and joint motion...
The purpose of this study was to understand how the form (i.e., shape and presence of underlying soft tissue) of residual limb tissue influences limb function and comfort for individuals with transfemoral limb loss. Specifically, there exist surgical techniques that are frequently applied to the lower limbs of individuals to reduce an excessive sof...
Pain in the lower back is frequent problem for most individuals with transfemoral amputation, which limits their overall mobility and quality of life. While the underlying root causes of back pain are multifactorial, a contributing factor is the mechanical loading environment within the lumbopelvic joint. Specifically, this study aims to explore th...
Human locomotion involves continuously variable activities including walking, running, and stair climbing over a range of speeds and inclinations as well as sit-stand, walk-run, and walk-stairs transitions. Understanding the kinematics and kinetics of the lower limbs during continuously varying locomotion is fundamental to developing robotic prosth...
Human locomotion involves continuously variable activities including walking, running, and stair climbing over a range of speeds and inclinations as well as sit-stand, walk-run, and walk-stairs transitions. Understanding the kinematics and kinetics of the lower limbs during continuously varying locomotion is fundamental to developing robotic prosth...
Background
Gait impairment is a common complication of multiple sclerosis (MS). Gait limitations such as limited hip flexion, foot drop, and knee hyperextension often require external devices like crutches, canes, and orthoses. The effects of mobility-assistive technologies (MATs) prescribed to people with MS are not well understood, and current de...
Objective
Intent recognition in lower-extremity assistive devices (e.g., prostheses and exoskeletons) is typically limited to either recognition of steady-state locomotion or changes of terrain (e.g., level ground to stair) occurring in a straight-line path and under anticipated condition. Stability is highly affected during non-steady changes of d...
Natural control of limb motion is continuous and progressively adaptive to individual intent. While intuitive interfaces have the potential to rely on the neuromuscular input by the user for continuous adaptation, continuous volitional control of assistive devices that can generalize across various tasks has not been addressed. In this study, we pr...
Clinical translation of “intelligent” lower-limb assistive technologies relies on robust control interfaces capable of accurately detecting user intent. To date, mechanical sensors and surface electromyography (EMG) have been the primary sensing modalities used to classify ambulation. Ultrasound (US) imaging can be used to detect user-intent by cha...
Intent recognition in lower-limb assistive devices typically relies on neuromechanical sensing of an affected limb acquired through embedded device sensors. It remains unknown whether signals from more widespread sources such as the contralateral leg and torso positively influence intent recognition, and how specific locomotor tasks that place high...
Seamless integration of lower-limb assistive devices with the human body requires an intuitive human-machine interface, which would benefit from predicting the intent of individuals in advance of the upcoming motion. Ultrasound imaging was recently introduced as an intuitive sensing interface. The objective of the present study was to investigate t...
Bimanual coordination is critical in many robotic and haptic systems, such as surgical robots and rehabilitation robots. While these systems often incorporate two robotic manipulators for each limb, there may be a missed opportunity to leverage overarching models of human bimanual coordination to improve the way in which the robotic manipulators ar...
UNSTRUCTURED
Objective: Intent recognition in lower-extremity assistive devices (e.g., prostheses and exoskeletons) is typically limited to either recognition of steady-state locomotion or changes of terrain (e.g., level ground to stair) occurring in a straight-line path and under anticipated condition. Stability is highly affected during non-stead...
Background
Gait impairment is a common complication of multiple sclerosis (MS). Gait limitations such as limited hip flexion, foot drop, and knee hyperextension often require external devices like crutches, canes, and orthoses. The effects of mobility-assistive technologies (MATs) prescribed to people with MS are not well understood, and current de...
Abstract Background Locomotor transitions between different ambulatory tasks are essential activities of daily life. During these transitions, biomechanics are affected by various factors such as anticipation, movement direction, and task complexity. These factors are thought to influence the neuromotor regulation of dynamic balance, which can be q...
Osteoarthritis is one of the most common causes of ambulatory disability. Developmental dysplasia of the hip (DDH) and femoroacetabular impingement (FAI) may lead to premature osteoarthritis in a young adult population. Current clinical assessments of DDH and FAI include clinical history, static radiological metrics, and physical examinations. Meth...
Ultrasound (US) imaging of muscle has been introduced as a promising sensing modality for assistive device control. Ten able-bodied subjects completed level, incline and decline walking on a treadmill in a motion capture laboratory while wearing reflective markers on upper- and lower-body. A wearable US transducer was affixed to subjects' anterior...
Objectives
Femoroacetabular impingement (FAI) and hip dysplasia are the most common causes of groin pain originating from the hip joint. To date, there is controversy over cut off values for the evaluation of abnormal femoral head-neck anatomy with significant overlap between the normal and abnormal hips. Our aim was to perform 3DCT analysis of fem...
Bimanual coordination plays a vital role in many haptic and robotic system operations. However, theories in bimanual human motor control are rarely integrated into the control system for human-in-the-loop robots, potentially limiting the usability and collaborative potential between the human and robot, particularly for complex tasks such as roboti...
Background:
Clinical balance assessments often rely on functional tasks as a proxy for balance (e.g., Timed Up and Go). In contrast, analyses of balance in research settings incorporate quantitative biomechanical measurements (e.g., whole-body angular momentum, H) using motion capture techniques. Fully instrumenting patients in the clinic is not f...
A reliable, flexible and simple source of
information would benefit robust handling of predicting
locomotion modes for assistive device control (e.g., prostheses).
However, to date, the sources of mechanical signals have been
mainly limited to the information acquired through embedded
sensors in the device. It remains unclear whether biomechanical...
Objective
To analyze regional muscle CT density and bulk in femoroacetabular impingement (FAI) and hip dysplasia (HD) versus controls.
Materials and methods
Patients who obtained perioperative CT imaging for FAI and HD before surgery were retrospectively studied. Asymptomatic controls included for comparison. Two readers independently evaluated re...
Control of lower-limb assistive devices would benefit from predicting the intent of individuals in advance of upcoming motion, rather than estimating the current states of their motion. Human lower-limb motion estimation using ultrasound (US) image derived features of skeletal muscle has been demonstrated. However, predictability of motion in time...
Clinical viability of powered lower-limb assistive devices requires reliable and intuitive control strategies. Stance and swing are the main phases of the gait cycle across different locomotion tasks. Hence, a reliable method to accurately identify these phases can decrease sensing complexity and assist in enabling high-level control of assistive d...
Aim
Determine correlations of 3DCT cam-type femoroacetabular impingement (FAI) measurements with surgical findings of labral tear and cartilage loss.
Methods
Digital search of symptomatic cam-type FAI from July 2013 to August 2016 yielded 43 patients. Two readers calculated volumes of femoral head, bump, and alpha angles on 3DCT images. Correlatio...
Active ankle-foot prostheses generate mechanical power during the push-off phase of gait, which can offer advantages over passive prostheses. However, these benefits manifest primarily in joint kinetics (e.g., joint work) and energetics (e.g., metabolic cost) rather than balance (whole-body angular momentum, H), and are typically constrained to pus...
Objective:
Powered assistive devices need improved control intuitiveness to enhance their clinical adoption. Therefore, the intent of individuals should be identified and the device movement should adhere to it. Skeletal muscles contract synergistically to produce defined lower-limb movements so unique contraction patterns in lower-extremity muscu...
Maintaining balance on ramps is important for mobility. However, balance is commonly assessed using inverted pendulum-based metrics (e.g., margin of stability), which may not be appropriate for assessment of human walking on non-level surfaces. To investigate this, we analyzed stability on ramps using four different inverted pendulum models: extrap...
Purpose:
Evaluate feasibility and reliability of 3DCT semi-automatic segmentation and volumetrics of CAM lesions in femoroacetabular impingement and determine correlations with anthropometrics.
Methods:
Consecutive series of 43 patients with CAM type FAI underwent 3DCT. 20 males and 23 females (30 unilateral and 13 bilateral symptomatic hips) we...
Intent recognition strategies for lower-limb assistive
technologies (e.g., prostheses and exoskeletons) are typically
limited to transitions from one terrain to another (e.g., level
ground to stairs) occurring under anticipated cognitive states
and in a straight path. However, such systems might be unable
to robustly handle unanticipated transition...
Clinical Balance Assessments Often Rely On Functional Tasks As A Proxy For Balance (E.G., Timed Up And Go). In Contrast, Analyses Of Balance In Research Settings Incorporate Quantitative Biomechanical Measurements (E.G., Whole-Body Angular Momentum, H) Using Motion Capture Techniques. Fully Instrumenting Patients In The Clinic Is Not Feasible, And...
Two-Thirds Power Law is a frequently observed relationship in human movement, relating velocity and curvature of movement trajectory. These movements span handwriting, larvae crawling, and human-robot interaction. Despite vast acceptance as a common principle of biology, it is unknown if the power law applies to interaction between amputees and pro...
Background:. Excess residual limb fat is a common problem that can impair prosthesis control and negatively impact gait. In the general population, thighplasty and liposuction are commonly performed for cosmetic reasons but not specifically to improve function in amputees. The objective of this study was to determine if these procedures could enhan...
Background: Selection of prosthesis mechanical characteristics to restore function of persons with lower limb loss can be framed as an optimization problem to satisfy a given performance objective. However, the choice of a particular objective is critical, and considering only device and generalizable outcomes across users without accounting for in...
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 wi...
Selecting a specific foot placement strategy to perform walking maneuvers requires the management of several competing factors, including: maintaining stability, positioning oneself to actively generate impulses, and minimizing mechanical energy requirements. These requirements are unlikely to be independent. Our purpose was to determine the impact...
Powered knee-ankle prostheses are capable of providing net-positive mechanical energy to amputees. Yet, there are limitless ways to deliver this energy throughout the gait cycle. It remains largely unknown how different combinations of active knee and ankle assistance affect the walking mechanics of transfemoral amputees. This study assessed the re...
The majority of fall-related accidents are during stair ambulation-occurring commonly at the top and bottom stairs of each flight, locations in which individuals are transitioning to stairs. Little is known about how individuals adjust their biomechanics in anticipation of walking-stair transitions. We identified the anticipatory stride mechanics o...
Objective:
To test a new user-modulated control strategy that enables improved control of a powered knee-ankle prosthesis during sit-to-stand and stand-to-sit movements.
Design:
Within-subject comparison study.
Setting:
Gait laboratory.
Participants:
Seven (4 male, 3 female) unilateral transfemoral amputees capable of community ambulation....
Improving lower-limb prostheses is important to enhance the mobility of amputees. The purpose of this paper is to introduce an impedance-based control strategy (consisting of four novel algorithms) for an active knee and ankle prosthesis and test its generalizability across multiple walking speeds, walking surfaces, and users. The four algorithms i...
Lower limb prostheses that can generate net positive mechanical work may restore more ambulation modes to amputees. However, configuration of these devices imposes an additional burden on clinicians relative to conventional prostheses; devices for transfemoral amputees that require configuration of both a knee and an ankle joint are especially chal...
While myoelectric prosthetic devices have been used for decades in the upper extremities, only recently have motorized knee and ankle components proven durable and effective enough for use in the lower extremity amputee. The control schemes developed to capitalize on these prosthetic advances must take into account the biomechanical differences bet...
Lower limb prostheses that can generate near physiological joint power have the potential to improve the way amputees go about their activities of daily living. Amputees who have lost both their knee and ankle would also benefit from a system that allowed them to easily perform sit-to-stand and stand-to-sit movements, reposition their prosthesis us...
Intent recognition systems using pattern recognition technology to control powered lower-limb prostheses are promising for seamlessly changing between locomotion modes- such as transitioning from level walking to stair ascent. These transitions can be accomplished by training an algorithm to recognize the patterns of mechanical and/or myoelectric s...
New computerized and powered lower limb prostheses are being developed that enable amputees to perform multiple locomotion modes. However, current lower limb prosthesis controllers are not capable of transitioning these devices automatically and seamlessly between locomotion modes such as level-ground walking, stairs and slopes. The focus of this s...
Recently developed powered lower limb prostheses allow users to more closely mimic the kinematics and kinetics of non-amputee gait. However, configuring such a device, in particular a combined powered knee and ankle, for individuals with a transfemoral amputation is challenging. Previous attempts have relied on empirical tuning of all control param...
This paper presents the design and experimental implementation of a novel feedback control strategy that regulates effective shape on a powered transfemoral prosthesis. The human effective shape is the effective geometry to which the biological leg conforms - through movement of ground reaction forces and leg joints - during the stance period of ga...
Unilateral below-knee amputees develop abnormal gait characteristics that include bilateral asymmetries and an elevated metabolic cost relative to non-amputees. In addition, long-term prosthesis use has been linked to an increased prevalence of joint pain and osteoarthritis in the intact leg knee. To improve amputee mobility, prosthetic feet that u...
Unilateral below-knee amputees often develop comorbidities that include knee joint disorders (e.g., intact leg knee osteoarthritis), with the mechanisms leading to these comorbidities being poorly understood. Mechanical knee loading of non-amputees has been associated with joint disorders and shown to be influenced by walking speed. However, the re...
