Dr. Sunil K. Agrawal

In the United States alone, there are some 300,000 people living with spinal cord injury (SCI) and more than 17,000 new cases occur each year. Males account for 80 percent and generally injuries are due to vehicle crashes, falls, and acts of violence. The ability to recover functional movement — walking, standing, and balance — is difficult and often slow even for patients with incomplete injuries. However, studies have shown that activity-based therapies offer an encouraging approach to helping individuals with SCI. To that end, Sunil K. Agrawal, PhD, Professor of Mechanical Engineering and of Rehabilitation and Regenerative Medicine at Columbia University Irving Medical Center, has been leading research efforts in the development of novel robotic devices and interfaces that help patients retrain their movements.

In 2016, Dr. Agrawal’s current project — Tethered Pelvic Assist Device (TPAD) and Epidural Stimulation for Recovery of Standing in Spinal Cord Injured Patients — was awarded a five-year, $5 million grant from the New York State Spinal Cord Injury Research Board (SCIRB). The project is a collaboration with Co-Principal Investigator Susan Harkema, PhD, and Enrico Rejc, PhD, Department of Neurological Surgery, University of Louisville, Kentucky, Spinal Cord Injury Research Center, and Joel Stein, MD, Chair of the Department of Rehabilitation and Regenerative Medicine at Columbia University Irving Medical Center. Dr. Agrawal, who is also Director of the Robotics and Rehabilitation Laboratory and Robotic Systems Engineering Laboratory at Columbia University, is focused on improving the effectiveness of stand/balance training during SCI rehabilitation by using the TPAD device developed in his Robotics and Rehabilitation (ROAR) Lab.

The TPAD is a cable-driven robot for studying force adaptation in human walking by applying external forces and moments on the human pelvis. Wearable and lightweight, the pelvic belt consists of multiple cables connected to motors, a real-time motion capture system, and a real-time controller to regulate the tensions in the cables. TPAD can be programmed to provide symmetric or asymmetric pelvic forces, as well as corrective or perturbative forces, in any direction and respond to motions of the human body.

Applying TPAD to Spinal Cord Injury

Dr. Susan Harkema

Dr. Agrawal and his team have previously conducted studies that have shown that a single session of therapy with TPAD improved gait function and reactive reactions to unexpected perturbations for a short amount of time in patients with Parkinson’s disease, the results of which were published in the December 19, 2017 issue of Scientific Reports.

In a study of children with cerebral palsy who commonly exhibit crouch gait, the Columbia researchers used TPAD to apply down-ward symmetric or asymmetric pelvic force. “We hypothesized that walking with a downward pelvic pull would strengthen extensor muscles, especially the soleus, against the applied downward pull and would improve muscle coordination during walking,” explains Dr. Agrawal. “We took an approach opposite to conventional therapy with these children. Instead of partial body weight suspension during treadmill walking, we trained participants to walk with a force augmentation, applying a downward force of 10 percent of their body weight while walking on the treadmill. Following training, the children were actually able to walk more erect as compared to before training.” Results of this study were published in the July 26, 2017 issue of Science Robotics.

Now in the next phase of the TPAD development, Dr. Agrawal and his team are addressing the major issue of poor body control associated with spinal cord injury. “A person with SCI may have poor control at the pelvis level, upper body chest area, or the knees,” says Dr. Agrawal. “The earlier TPAD device only augments control at the pelvis level. But in order to facilitate standing training, which is the objective of the SCIRB project, we had to provide active assistance and support at three levels of the human body. Essentially, we are creating three TPADs that cooperate with each other at different levels of the human body within the same system.”

When perturbed while standing, a person with SCI requires the assistance of several physical therapists to prevent falling. “The newest iteration of the TPAD would provide the right force assistance and the ability to rebalance and move around rather than being fixed in one position, allowing the person to maintain equilibrium, as well as the confidence of being able to stand and support oneself,” says Dr. Agrawal.

“In the first year, our goal was to put together this special device and we are very much there,” continues Dr. Agrawal. “In the next several months we plan to test TPAD on healthy individuals and then slowly transition to applying it to patients with spinal cord injury.”

Drs. Susan Harkema, Enrico Rejc, and their colleagues at the Kentucky Spinal Cord Injury Research Center have pioneered the use of activity-based rehabilitation for SCI patients and the use of epidural stimulation of the lumbosacral spinal cord during standing training. The researchers combine epidural stimulation and principles of motor learning and have successfully shown this strategy to benefit severely injured individuals. However, even though these patients are able to stand, they cannot maintain balance and therefore are unable to transfer this skill to activities of daily living.

“When I visited Dr. Agrawal’s lab and observed their approach it was the first time that I saw something that could actually work with what we were doing scientifically.”

— Dr. Susan Harkema

Enter Dr. Agrawal and TPAD to provide the additional assistance needed. “When I visited Dr. Agrawal’s lab and observed their approach it was the first time that I saw something that could actually work with what we were doing scientifically. I was incredibly impressed,” says Dr. Harkema. “We’re very excited about this collaboration. What is so powerful is that these robotic devices are tailored to work with new discoveries about the nervous system. From my perspective, Dr. Agrawal and the Columbia researchers are creating an elegant design and an interface with the individual that is as least intrusive as possible. With TPAD, a person can do as much as they are able, but if they go outside preset parameters, the device can then provide support to keep them safe.”

“Dr. Harkema and her team have designed ways to use already available spinal cord stimulators that were shown to be effective in prodding the individual’s capability to stand and do things that they could not otherwise do paralyzed,” says Dr. Agrawal. “One of the challenges in their program is that each patient undergoes 70 to 80 sessions of several hours of training over many days and months. During each session, several trainers work with the individual, trying to balance them and perturb them simultaneously so that slowly they can get their balance back.”

The approach is time and labor intensive, prompting the Kentucky researchers to look to a robotic device that would provide similar capabilities and be available to more patients over time. “We’ve been discovering that the nervous system, especially after injury, relies on key sensory signals from the environment to function or relearn how to do a task,” says Dr. Harkema. “Integrating information from the environment, as well as any residual information that might still be crossing the injury from supraspinal centers, and practicing those over and over again with the right kinematic for that task, we believe one could regain the ability to do that task. The TPAD device can pay close attention to sensory cues and potentially accelerate the learning of the task, or relearning sitting, standing, sit-to-stand, or maybe, eventually, stepping and walking.”

“Dr. Harkema and her team have designed ways to use already available spinal cord stimulators that were shown to be effective in prodding the individual’s capability to stand and do things that they could not otherwise do paralyzed.”

— Dr. Sunil K. Agrawal

“Devices like TPAD are valuable in so many rehabilitation settings,” adds Dr. Agrawal. “Integrating technology can be great to collect quantitative data, as well as providing a very controlled experience to individuals as they’re undergoing these therapeutics.”

“Looking to the future,” notes Dr. Harkema, “I believe that these types of robotic training devices, which are much more consistent with what we’re doing, will continue to be developed and refined, and hopefully enable people with the most severe injuries to be much more functional in the home and in the community.”