Engineers develop new Robotic Spine Exoskeleton design

The Robotic Spine Exoskeleton consists of two six-degrees-of-freedom parallel-actuated modules connected in series, each with six actuated limbs. Each module controls the translations/rotations or forces/moments of one ring in three dimensions with respect to the adjacent ring. Photo credit: Sunil Agrawal/Columbia Engineering

Needing to wear a back brace can be both helpful and frustrating. Current brace options, which fit around the torso and hips, can help to correct abnormal curvatures of the spine but can often be bulky, uncomfortable and limit the user’s range of motion. What is more, wearers also tend to suffer from skin breakdown due to prolonged, excessive force.

A team of Columbia Engineering researchers have addressed these issues with a new Robotic Spine Exoskeleton (RoSE) design.

The team designed RoSE in order to study vivo measurements of torso stiffness and characterizes the three-dimensional stiffness of the human torso. This dynamic brace is unique and allows the researchers to study with actual human users.

“Earlier studies used cadavers, which by definition don’t provide a dynamic picture,” says the study’s principal investigator Sunil Agrawal, professor of mechanical engineering at Columbia Engineering and professor of rehabilitation and regenerative medicine at Columbia University Vagelos College of Physicians and Surgeons.

According to Agrawal, RoSE is the first device to measure and modulate the position or forces in all six degrees-of-freedom in specific regions of the torso.

Developed in Agrawal’s Robotics and Rehabilitation (ROAR) Laboratory, RoSE consists of three rings placed on the pelvis, mid-thoracic, and upper-thoracic regions of the spine. The motion of two adjacent rings is controlled by a six-degrees-of-freedom parallel-actuated robot.

The system has a total of 12 degrees-of-freedom controlled by 12 motors. RoSE can control the motion of the upper rings with respect to the pelvis ring or apply controlled forces on these rings during the motion. The system can also apply corrective forces in specific directions while still allowing free motion in other directions.

The researchers used 8 healthy male participants and 2 participants with spinal deformities to control the position/orientation of specific cross sections of the subjects’ torsos while simultaneously measuring the exerted forces/moments.

According to the findings, three-dimensional stiffness of the human torso can be characterized using RoSE and that the spine deformities induce torso stiffness characteristics significantly different from the healthy subjects.

“Our results open up the possibility for designing spine braces that incorporate patient-specific torso stiffness characteristics,” says the study’s co-principal investigator David P. Roye, a spine surgeon and a professor of pediatric orthopedics at the Columbia University Irving Medical Center.

“We built upon the principles used in conventional spine braces, i.e., to provide three-point loading at the curve apex using the three rings to snugly fit on the human torso,” says the lead author Joon-Hyuk Park, who worked on this research as a PhD student and a team member at Agrawal’s ROAR laboratory. “In order to characterize the three-dimensional stiffness of the human torso, RoSE applies six unidirectional displacements in each DOF of the human torso, at two different levels, while simultaneously measuring the forces and moments.”

While this first study used a male brace designed for adults, Agrawal and his team have already designed a brace for girls as idiopathic scoliosis is 10 times more common in teenage girls than boys.

“Directional difference in the stiffness of the spine may help predict which children can potentially benefit from bracing and avoid surgery,” says Agrawal.

The study was published online March 30 in IEEE Transactions of Neural Systems and Rehabilitation Engineering.

www.engineering.columbia.edu