This robotic trunk to aid patients with spinal cord injury

A Columbia Engineering team led by an Indian scientist has invented a robotic device that can be used to assist and train people with spinal cord injuries to sit more stably by improving their trunk control, gaining an expanded active sitting workspace without falling over or using their hands to balance. Spinal cord injuries (SCI) can cause devastating damage, including loss of mobility and sensation.

"We designed TruST for people with SCIs who are typically wheelchair users. We found that TruST not only prevents patients from falling, but also maximises trunk movements beyond patients' postural control, or balance limits," said Sunil Agrawal, professor of mechanical engineering and of rehabilitation and regenerative medicine.

The study, published in the journal Spinal Cord Series and Cases, is the first to measure and define the sitting workspace of patients with spinal cord injuries based on their active trunk control with help from the "Trunk-Support Trainer (TruST)" robotic device.

The robotic trunk is a motorised-cable driven belt placed on the user's torso to determine the postural control limits and sitting workspace area in people with spinal cord injuries. It delivers forces on the torso when the user performs upper body movements beyond the postural stability limits while sitting.

The five patients who participated in the pilot study were examined with the Postural Star-Sitting Test, a customised postural test that required them to follow a ball with their head and move their trunk as far as possible, without using their hands. The test was repeated in eight directions, and the researchers used the results to compute the sitting workspace of each individual.

The team then tailored the robotic device for each subject to apply personalised assistive force fields on the torso while the subjects performed the same movements again. With the 'TruST', the subjects were able to reach further during the trunk excursions in all eight directions and significantly expand the sitting workspace around their bodies, on an average of about 25 per cent more.

"The capacity of 'TruST' to deliver continuous force-feedback personalised for the user's postural limits opens new frontiers to implement motor learning-based paradigms to retrain functional sitting in people with SCI," says Victor Santamaria, a physical therapist, postdoctoral researcher in Agrawal's Robotics and Rehabilitation Laboratory.

Agrawal's team is now exploring the use of TruST within a training paradigm to improve the trunk control of adults and children with spinal cord injury. "The robotic platform will be used to train participants with the SCI by challenging them to move their trunk over a larger workspace, with the TruST providing assist-as-needed force fields to safely bring the subjects back to their neutral sitting posture," elaborated Agrawal.

"This force field will be adjusted to the needs of the participants over time as they improve their workspace and posture control," he added.