Overview

We have combined our understanding of walking and a particular foot force control deficit following stroke to design and build a rehabilitation interface for retraining the appropriate coordination needed for walking. The treadmill-like device focuses on training stroke patients to produce foot force appropriate for walking without relying on a harness for balance. The device requires the patient to actively practice generating the appropriate muscle coordination characterized in our previous work. This approach to focusing on the coordination needed to balance during walking is currently overlooked by conventional therapies.

Device Design

Our rehabilitation interface is a treadmill-like environment. Rather than a belt, programmable motor-driven footplates move fore and aft under the feet as the person walks. The feet are attached to the plates with selected degree of freedom constraints. The feet cannot move fore and aft relative to the plate but do have a limited range of pitch, yaw, and roll rotation as well as the latitude to lift off of the plate. This allows for a natural heel-to-toe motion of the foot during walking while safely keeping the foot on the plate. Each foot plate is instrumented with a six-axis force/torque sensor to assess the lower limb coordination of the user. The patient is also connected to the device with a torso harness that can only provide horizontal and rotational (not vertical) support if needed. This torso harness is instrumented to quantify the force from the harness on the user that he or she is depending on for balance. This allows the patient to explore his or her motor coordination abilities without the consequence of falling.

The theory that impaired walking behaviors observed following stroke are largely compensations for an underlying foot force direction deficit predicts that the horizontal and rotational stabilization provided by our torso harness will be sufficient to remove the need for these compensatory behaviors. This should result in more non-impaired walking similar to that which is elicited by the stabilization body-weight supported treadmill training harnesses implicitly provide. Operation of the device then focuses on the person training appropriate balance without these compensatory behaviors.

Device Operation

Our rehabilitation interface allows us to quantify all of the external forces acting on the patient. This provides the ability to not only characterize balance and foot force deficits, but also give the patient feedback on how to reduce reliance on harness for support while walking with appropriate leg muscle coordination. Patients can be given visual feedback on a screen in front of them while walking to indicate how they are leaning into the harness. Another feedback mode involves speed modulation of the plate motors in response to coordination performance. The plates can be programmed such that the patient’s foot force acts as a throttle; the plates will only move through a walking motion when correct coordination is used.

Additional Applications

The programmable nature of the device allows endless opportunities for future studies and applications. Other impaired walking populations (Parkinson’s disease, traumatic brain injury, cerebral palsy, elderly individuals, etc.) can be studied and specialized interventions developed. This approach to walking may also be useful in the field of prosthetics & orthotics, sport-specific training, and injury recovery.

Commercialization Efforts

Commercialization efforts aim to place this device in hospitals and clinics where it can best reach patients. Ideally, the device will also be available to other institutions as a research tool in order to expand understanding of walking impairments and their treatment. Initial funding for commercialization efforts was provided by the University of Wisconsin Discovery-to-Product program. The KIINCE (‘keen-say’, kinetic immersive interfaces for neuromuscular coordination enhancement) company is driving forward commercialization efforts.

Patents:

Gruben K, Schmidt M: Electromechanical force-magnitude, force-angle sensor. Sept. 2, 2008, U.S. patent #7,418,862.

Gruben K, Schmidt M: Training device for muscle activation patterns. Sept. 4, 2012, U.S. Patent #8,257,284 B2

Gruben K, Boehm W: Footplate harness for natural kinematics in walking training apparatus. May 18, 2015, U.S. Patent application filed.