Proof-of-concept of a Robotic Knee Exoskeleton in Healthy Subjects and Hemiparetic Patients During Gait.
Condition: Hemiparesis/Hemiplegia (One Sided Weakness/Paralysis)
MeSH terms: Paralysis; Hemiplegia; Paresis
Study type: Interventional

Summary: 
      Hemiparetic gait is characterized by strong asymmetries that could severely affect the
      quality of life of stroke survivors. This asymmetry is due to motor deficits in the paretic
      leg and the resulting compensations in the non-paretic limb.

      In this study, the investigators aim to evaluate the effect of actively promoting gait
      symmetry in hemiparetic patients by assessing the behavior of both paretic and non-paretic
      lower limbs. To this end, the investigators use a unilateral active Knee-Ankle-Foot Orthosis
      able to assist the paretic limb of hemiparetic patients during gait.

      The system is able to synchronize its action with the movement of the unassisted joints,
      promoting a natural and intuitive interaction. The device generate the assistance according
      to two differents strategies: (1) Replicating the movement of the helathy leg or (2) Inducing
      a healthy gait pattern on the paretic leg.

      The hypothesis is that a proper and natural interaction between the user and the exoskeleton
      would enable the patients to consider the robot action as a part of their own gait
      capability, improving their gait quality as consequence. Hemiparetic asymmetry is not only
      due to impairments in the affected limb, but also it is the consequence of biomechanical
      compensatory mechanisms that might arose in the non-paretic leg. We aim to assess the
      adaptation process of the subject to the exoskeleton assistance, and to evaluate the effects
      of such human-robot interaction in both paretic and non-paretic legs.
    

Detailed description: 
      - Brief name: Proof-of-concept of a unilateral robotic knee exoskeleton and evaluation of its
      effects over gait symmetry.

      - Materials: The investigators have developed a Knee-Ankle-Foot orthosis (KAFO) composed of
      two joints aligned to the knee and ankle of the user. The length of its bars and the
      positions of its braces can be tailored to the anthropometry of different users. The knee
      joint is actuated by a DC brushless motor EC-60 flat 408057 (Maxon ag, Switzerland) coupled
      with a harmonic drive CSD-20-160-2AGR (Harmonic Drive LLC, EE.UU.). The transmission ratio of
      1:60 of this system enables the application of a mean torque of 35Nm. The ankle joint of the
      prototype remains non-actuated and unlimited, enabling its free movement in the sagittal
      plane. The total weight of the KAFO is about 4kg.

      The prototype is equipped with sensors that provide information on system variables that are
      used for its control in real-time, such as the flexion angle of the robot joint or the
      interaction torque between user and robot. In addition, the gait kinematic of the user is
      measured by Inertial Measurement Units (IMUs) and the contact of both feet with the floor by
      Force Sensing Resistors (FSRs).

      The system uses an Adaptive Frequency Oscillator to estimate the continuous gait phase of the
      contralateral limb and synchronically assists the paretic leg following two different control
      strategies: (1) Replicating the movement of the sound leg (Echo Strategy) or (2) Inducing a
      healthy gait pattern on the paretic leg (Pattern strategy). The action of the robot depends
      on the gait phase of the assisted leg: during stance the robot reinforces the limb so the
      system composed of the leg and the exoskeleton can load the user's weight and not collapse,
      while during the swing phase the robot guides the limb's movement according to the
      Assisted-As-Needed (AAN) paradigm creating a force tunnel around the prescribed trajectory.

      - Procedures: Subjects were instructed to walk on a treadmill at a constant speed during
      trials of 5 minutes. All subjects carried out four different kinds of trials: (1) NoExo:
      subjects only wore the inertial sensors and the insole pressure sensors to acquire their
      basal motion; (2) Free: subjects wore the exoskeleton although the actuator was mechanically
      decoupled, so it enabled the free movement of the knee; (3) Echo: the device provided gait
      assistance following the Echo-control strategy; and (4) Pattern: the device provided gait
      assistance following the Pattern strategy. During trials, patients wore a safety harness,
      although it did not support any weight. Previously to the execution of the trials, the gait
      velocity was self-selected by the subjects to a comfortable level. Subjects rested between
      trials for five minutes at least, in order to avoid adaptation and learning effects from
      trial to trial.

      Healthy subjects also performed a previous trial under variable gait speed (VariableSpeed).
      They walked over the treadmill as in the NoExo condition, although the gait speed randomly
      varies from 1km/h to 3km/h in 0.2km/h steps for 15 seconds at least.

      - Intervention providers A physiotherapist and an engineer are present during the trials. The
      first is responsible of assessing the basal gait of the subjects and evaluating his/her state
      while the assistance is provided. The engineer is responsible of managing the device and
      recording the data.

      Both researchers monitor fidelity to the intervention by direct supervision.

        -  Modes of delivery The protocol is provided to one participant at a time. Each patient
           completes the protocol once.

        -  Location Hospital Beata María Ana (Madrid, Spain)

        -  Tailoring and modifications The protocol remains unaltered across applications. The only
           adaptation to patients is the choice of the comfortable gait speed for the trials.
    

Intervention name(s): Exoskeleton assisted gait on a treadmill
Intervention type(s): Device
Intervention description(s): Subjects were instructed to walk on a treadmill at a constant speed during trials of 5 minutes. All subjects carried out four trials: (1) NoExo: subjects only wore the sensors to acquire their basal motion; (2) Free: subjects wore the exoskeleton although the actuator was mechanically decoupled, so it enabled the free movement of the knee; (3) Echo: the device provided gait assistance following the Echo-control strategy; and (4) Pattern: the device provided gait assistance following the Pattern strategy. During trials, patients wore a safety harness that did not support any weight. Previously to the execution of the trials, the gait velocity was self-selected by the subjects to a comfortable level. Subjects rested between trials for five minutes. Healthy subjects also performed a previous trial under variable gait speed. They walked over the treadmill as in the NoExo condition, although the gait speed randomly varies from 1km/h to 3km/h in 0.2km/h steps for 15 seconds at least.
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Device Feasibility
Keywords: Hemiparetic Gait; Robotic Knee Exoskeleton