Walk Assist Device to Improve Community Ambulation

The goal of this research study was to examine the immediate effectiveness of a prototype wearable robotic stride management assist device (SMA) designed by Honda R&D on clinical walking performance, walking energetics, gait kinematics and corticospinal excitability in individuals with stroke.

The SMA assists walking by providing a flexion and extension torque assist at the hip joint. The subjects in this study are asked to perform two sets of experiments: one set with the device on and one set with the device turned off. The order in which the subjects performed these sets of experiments is selected randomly. Each set of experiments includes over-ground walking speed and endurance tests, a graded treadmill test with metabolic measures, motion capture and force treadmill analysis, and measures of corticospinal drive using transcranial magnetic stimulation (TMS). The primary outcome to be measured is change in self-selected walking speed with the device on, the secondary outcome measures include metabolic, corticospinal and biomechanical analysis.

Inclusion criteria

• Stroke subjects with a history of unilateral, supratentorial, ischemic or hemorrhage stroke will be recruited, with lesion location confirmed by radiographic findings.
• All subjects who score > 10 on the Lower Extremity Motor Score (LEMS) developed previously to measure strength in Spinal Cord Injury (SCI). For the LEMS criteria, preliminary data indicate that subjects with LEMS < 10 in the chronic stages do not recover walking.
• All subjects will be required to walk > 10 m over ground without physical assistance at self-selected walking speeds ≤ 0.8 m/s using assistive devices and bracing below the knee as needed. A criterion of 0.8 m/s is utilized to target participants with limited or minimal ambulation in the community. Subjects will be further stratified into those who walk < 0.4 m/s and > 0.4 m/s, identified as household vs. limited community ambulators, respectively.
• Range of motion (ankle: -10 to 30 deg, knee: 0 to 90 deg, hip: -10 to 40 deg) consistent with gait;
• Medically stable with medical clearance to participate (absence of concurrent illness, including unhealed decubiti, infection, cardiopulmonary disease, osteoporosis, active heterotrophic ossification or peripheral nerve damage in the lower limbs, history of traumatic head injury);
• Able to tolerate 30 minutes of upright (standing) position without orthostasis (decrease in blood pressure by 20 mmHg systolic and 10 mmHg diastolic; minimized with ambulatory population);
• Must not be undergoing concurrent physical therapy to eliminate effects of additional interventions;
• Patients prescribed medications for spasticity will not be excluded from participation but will be asked to maintain current levels of medication or inform the researcher if changes are necessary.

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Exclusion criteria

• Women of childbearing potential will not be excluded, although women who are pregnant will be excluded due to potential forces at trunk from body weight support or pelvic assistance;
• Significant cardiorespiratory or metabolic disease that may limit exercise participation.
• Weights limit > 250 lbs (limit of most counter-weight safety systems).
• History of previous orthopedic or neurological conditions which may impair walking.
• Exclusion for TMS: pacemaker, metal implants in the head region, history of epilepsy or seizures, skull fractures or skull deficits, concussion within the last 6 months, unexplained recurring headaches, medications that lower seizure threshold, and pregnancy.
• Subjects with scores < 23 on the Mini Mental Status Exam will be excluded.