Spine deformities, such as idiopathic
scoliosis and kyphosis (also known as "hunchback"), are characterized
by an abnormal curvature in the spine. The children with these spinal
deformities are typically advised to wear a brace that fits around the torso
and hips to correct the abnormal curve. Bracing has been shown to prevent
progression of the abnormal curve and avoid surgery. The underlying technology
for bracing has not fundamentally changed in the last 50 years.
While
bracing can stop/retard the progression of abnormal spine curves in
adolescents, current braces impose a number of limitations due to their rigid,
static, and sensor-less designs. In addition, users find them uncomfortable to
wear and can suffer from skin breakdown caused by prolonged, excessive force.
Moreover, the inability to control the correction provided by the brace makes
it difficult for users to adapt to changes in the torso over the course of
treatment, resulting in diminished effectiveness.
To
address these deficiencies, Columbia Engineering researchers have invented a
new Robotic Spine Exoskeleton (RoSE) that may solve most of these limitations
and lead to new treatments for spine deformities. The RoSE is a dynamic spine
brace that enabled the team to conduct the first study that looks at in vivo
measurements of torso stiffness and characterizes the three-dimensional
stiffness of the human torso. The study was published online March 30 in IEEE Transactions
of Neural Systems and Rehabilitation Engineering.
"To
our knowledge, there are no other studies on dynamic braces like ours. 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. "The 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. This study is foundational and we believe will lead to
exciting advances both in characterizing and treating spine deformities."
Developed
in Agrawal's Robotics and Rehabilitation (ROAR) Laboratory, the 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. Overall, the system has 12
degrees-of-freedom controlled by 12 motors. The 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.
Eight
healthy male subjects and two male subjects with spine deformities participated
in the pilot study, which was designed to characterize the three-dimensional
stiffness of their torsos. The researchers used the RoSE, to control the position/orientation
of specific cross sections of the subjects' torsos while simultaneously
measuring the exerted forces/moments.
The
results showed that the three-dimensional stiffness of the human torso can be
characterized using the RoSE and that the spine deformities induce torso
stiffness characteristics significantly different from the healthy subjects.
Spinal abnormal curves are three-dimensional; hence the stiffness
characteristics are curve-specific and depend on the locations of the curve
apex on the human torso.
"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.
"Our findings could also lead to new interventions using dynamic
modulation of three-dimensional forces for spine deformity treatment."
"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, the 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. The team is actively recruiting girls
with scoliosis in order to characterize how torso stiffness varies due to such
a medical condition.
"Directional
difference in the stiffness of the spine may help predict which children can
potentially benefit from bracing and avoid surgery," says Agrawal.
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