Assistive Hip Exoskeleton Study for Stroke
Condition: Lower Limb Injury; Stroke
MeSH terms: Stroke; Leg Injuries
Study type: Interventional

Summary: 
      The increased metabolic and biomechanical demands of ambulation limit community mobility in
      persons with lower limb disability due to neurological damage. There is a critical need for
      improving the locomotion capabilities of individuals with stroke to increase their community
      mobility, independence, and health. Robotic exoskeletons have the potential to assist these
      individuals by increasing community mobility to improve quality of life. While these devices
      have incredible potential, current technology does not support dynamic movements common with
      locomotion such as transitioning between different gaits and supporting a wide variety of
      walking speeds. One significant challenge in achieving community ambulation with exoskeletons
      is providing an adaptive control system to accomplish a wide variety of locomotor tasks. Many
      exoskeletons today are developed without a detailed understanding of the effect of the device
      on the human musculoskeletal system. This research is interested in studying the question of
      how the control system affects stroke biomechanics including kinematic, kinetics and muscle
      activation patterns. By optimizing exoskeleton controllers based on human biomechanics and
      adapting control based on task, the biggest benefit to patient populations will be achieved
      to help advance the state-of-the-art with assistive hip exoskeletons.
    

Detailed description: 
      One significant challenge in achieving community ambulation with exoskeletons is providing an
      adaptive control system to accomplish a wide variety of locomotor tasks. Many exoskeletons
      today are developed without a detailed understanding of the effect of the device on the human
      musculoskeletal system. The study is interested in exploring the question of how the control
      system affects human biomechanics including kinematic, kinetics and muscle activation
      patterns. By optimizing exoskeleton controllers based on human biomechanics and adapting
      control based on task, this work will be able to provide the biggest benefit to patients and
      advance the state-of-the-art with assistive hip exoskeletons. A large patient population that
      could benefit from lower limb assistive technology are stroke survivors, which is the
      specific population this proposal targets. One common characteristic of stroke survivors who
      regain their ability to walk is that the hip muscles are overtaxed due to distal weakness.
      The investigators propose to use a powered hip exoskeleton to augment their proximal
      musculature, which needs to produce significant power output in most locomotion activities
      such as standing up, walking, and going up stairs or slopes. Another biomechanical aspect of
      stroke survivors is an asymmetric gait in terms of kinematics, kinetics and muscle
      activations. The research will examine what kind of exoskeleton assistance is most beneficial
      to stroke survivors for enhancing community ambulation. The hypothesis is that since the gait
      is asymmetric, the controller will need to be asymmetric to provide optimal assistance to aid
      in mobility. The long-term research goal is to create powered assistive exoskeletons devices
      that are of great value to individuals with serious lower limb disabilities by improving
      clinical outcomes such as walking speed and community ambulation ability. The overall
      objective of the proposed project is to study the biomechanical effects of using a hip
      exoskeleton with adaptive controllers for assisting stroke survivors with lower limb deficits
      to improve their community ambulation capabilities. The central hypothesis overarching both
      aims is that exoskeleton control that adapts to environmental terrain will improve mobility
      metrics for human exoskeleton users on community ambulation tasks. The rationale is that
      since human biomechanics change based on task, exoskeleton controllers likewise need to
      optimize their assistance levels to match what the human is doing. The team has previously
      designed and extensively tested an autonomous hip exoskeleton in able-bodied subjects on a
      treadmill and plan to follow this up with a separate study on able bodied subjects during
      overground locomotion of walking, stairs, and ramps. The aim of this study is to translate an
      autonomous robotic hip exoskeleton to provide adaptive assistance in community ambulation for
      stroke survivors with mobility impairment. The team will analyze the biomechanical effects
      and clinical benefits with using an autonomous hip exoskeleton for a walking impaired user
      (due to stroke). The primary hypothesis for this aim is that stroke survivors will increase
      their mobility in community ambulation tasks using the adaptive control framework. A
      sub-hypothesis is that stroke survivors who present with unilateral impairment will have
      superior biomechanical and clinical outcomes using a controller with asymmetric assistance.
      The investigators expect a controller that provides a greater assistance to the impaired side
      to improve overall symmetry and help the stroke survivor maintain a more efficient gait
      pattern to help improve walking speed (primary outcome measure). The expected outcome of
      these aims will be an increased understanding of the biomechanical and clinical effects in
      applying hip assistance with a robotic exoskeleton in community ambulation tasks such as
      overground walking, ramps and stairs. This work will serve as a foundational start for a
      broader planned study of optimizing controllers to improve biomechanics in the walking
      impaired using powered hip autonomous exoskeletons. This aim will have a positive impact by
      helping to inform the design and control of future exoskeleton for assisting individuals with
      lower limb disabilities, with specific insight in stroke survivors with mobility impairment.
    

Intervention name(s): Powered hip exoskeleton
Intervention type(s): Device
Intervention description(s): The study team will be testing a powered hip exoskeleton and its capability to improve locomotion in stroke survivors.
Intervention model: Single Group Assignment
Intervention model description: The model used is a repeated measures single arm study. Multiple conditions including using and not using the device will be tested on the same subjects to have multiple test points on a per subject basis.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Exoskeleton