Research ArticleREHABILITATION ROBOTICS

Robot-driven downward pelvic pull to improve crouch gait in children with cerebral palsy

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Science Robotics  26 Jul 2017:
Vol. 2, Issue 8, eaan2634
DOI: 10.1126/scirobotics.aan2634
  • Fig. 1 Gait characteristics of crouch gait and TPAD training.

    Motion capture data from a child with crouch gait during free walking before the training is illustrated, which was collected using a Vicon system. The gait pattern of the crouch gait can be described as excessively flexed hips/knees and reduced plantar flexion of the ankle. TPAD training applies a downward force on the stance leg to improve the muscle patterns necessary for extension of the limbs while bearing the child’s weight. Here, the soleus muscle engaged during the single stance phase is intensively trained to improve the crouch gait.

  • Fig. 2 System setup and results of a representative participant in a single training session.

    (A) TPAD system setup. (B) EMG data, (C) lower limb angles for hip, knee, and ankle, (D) pelvic translational ROM and trunk angle, and (E) vertical GRFs during session 1 including free walking before training, during training with force, and free walking after training. Data during training (black line) were recorded at the seventh minute of training, and data after training (blue line) were recorded at the third minute after training. Yellow shaded area presents the stance phase of the gait cycle. Trunk ankle is defined by two markers attached to the seventh cervical vertebra and sacrum, averaged over the gait cycle.

  • Fig. 3 Results of a representative participant with multiple training sessions.

    Average and SE are presented for the data before and after 15 training sessions during free walking. (A) EMG of muscles. (B) Lower limb angles. (C) Pelvic translation ROM and the trunk angle. (D) Vertical GRFs (please refer to movie S1).

  • Fig. 4 Group data during free walking between sessions 1 and 16.

    For (A) to (C), the left side of the graphs presents data for each week (sessions 1, 3, 6, 9, 12, and 15), and the right side presents data for sessions 1 and 16, which have the same walking speed. From sessions 1 to 15, the treadmill speed was increased every first session of each week, as described in Materials and Methods. (D) EMG is scaled with the maximum value of baseline in session 1. (E) Trunk angle during walking. (F) The definition of the GRF difference is illustrated, and its group value is presented in (G). Mean and SEs are presented for six participants (n = 6), except EMG (n = 5).

  • Fig. 5 Cable-driven system diagram for structure matrix.

    The TPAD is a cable-driven parallel system with m actuated cables connected to the participant’s pelvis having n = 6 DOFs. One end of each cable is attached to the pelvis, and the other end is attached to an electrical motor, shown as points Bi and Pi, respectively. These cables together exert an external wrench, We, on the pelvis.

  • Fig. 7 TPAD controller performance for three force components.

    (A) Fx in medial-lateral direction satisfies to be within ±1.5% BW. (B) Fy in anterior-posterior direction is within ±1.5% BW. (C) Fz in vertical direction is controlled to be at −10% BW.

  • Fig. 6 TPAD controller schematic and testing for WPC.

    (A) Control architecture of low- and high-level controller. (B) Schematic of cable motion test. (C) WPC function. (D) A cable was pulled and pushed about 1 ft by hand at frequencies of 0.4 and 0.5 Hz for tension Td = 20 N. Tc and Tnc are the cable tension values with and without the WPC term. The performance of controller is improved during pulling phase, when WPC is added.

  • Fig. 8 TPAD training protocol.

    Training consists of 15 training sessions over 5 weeks. Pre-evaluation was conducted 1 week before the first session, and post-evaluation was conducted 2 weeks after the last training session. The 16th session was added after the 15th training session to record free walking on the treadmill with the same speed as session 1.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/8/eaan2634/DC1

    Materials and Methods

    Fig. S1. Vertical GRF of sessions 1, 15, and 16 for all six children during free walking.

    Fig. S2. Vertical GRF of all six children during free walking and training with downward force.

    Fig. S3. Pelvic ROM and gait parameters during the training.

    Fig. S4. EMG for five different muscles before and after 15 training sessions.

    Fig. S5. Walking speed of individual children with CP.

    Fig. S6. System setup.

    Fig. S7. Defining motor constant.

    Fig. S8. Vertical force evaluation during training sessions.

    Table S1. Participant information and clinical measurements.

    Table S2. Response of the participant and parents from clinical chart.

    Table S3. Spasticity of ankle and knee joints.

    Table S4. Cable attachment locations on the frame.

    Movie S1. Experiment video including overground walking before/after training.

  • Supplementary Materials

    Supplementary Material for:

    Robot-driven downward pelvic pull to improve crouch gait in children with cerebral palsy

    J. Kang, D. Martelli, V. Vashista, I. Martinez-Hernandez, H. Kim, S. K. Agrawal*

    *Corresponding author. Email: sunil.agrawal{at}columbia.edu

    Published 26 July 2017, Sci. Robot. 2, eaan2634 (2017)
    DOI: 10.1126/scirobotics.aan2634

    This PDF file includes:

    • Materials and Methods
    • Fig. S1. Vertical GRF of sessions 1, 15, and 16 for all six children during free walking.
    • Fig. S2. Vertical GRF of all six children during free walking and training with downward force.
    • Fig. S3. Pelvic ROM and gait parameters during the training.
    • Fig. S4. EMG for five different muscles before and after 15 training sessions.
    • Fig. S5. Walking speed of individual children with CP.
    • Fig. S6. System setup.
    • Fig. S7. Defining motor constant.
    • Fig. S8. Vertical force evaluation during training sessions.
    • Table S1. Participant information and clinical measurements.
    • Table S2. Response of the participant and parents from clinical chart.
    • Table S3. Spasticity of ankle and knee joints.
    • Table S4. Cable attachment locations on the frame.

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Experiment video including overground walking before/after training.

    Files in this Data Supplement:

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