Biomedical Engineering Reference
In-Depth Information
3.5 ADVANTAGES TO INTRODUCE ROBOTICS TO SCI GAIT
RECONSTRUCTION
As trials for gait reconstruction in paraplegics, orthoses, functional electrical stim-
ulation (FES) (CS; (2005)), or hybrid assistive systems (HAS), which combine FES
and an orthosis (Popovic; (1989)), have been used. An orthosis, providing standing
stability, maintains stance stability in the stance phase and smooth clearance in
the swing phase by restriction of the DOF in the lower extremities. However,
restriction of the DOF to fix the knee in an extension position causes difficulties
in standing up and sitting down.
Since paraplegics lack power in the lower extremities, the upper extremities
are mostly used for progression and lateral motion of the body in orthotic walking,
which places a large burden on the upper extremities and high energy consump-
tion in walking (Suzuki; (2007)) making it difficult to continue walking for a long
distance without rest.
Subject was able to stand and walk independently with the WPAL that we
developed. The sit-to-stand motion requires the largest torque for knee joint move-
ment, and it has been postulated that torque of 12-50 N is required for one knee
to achieve standing from a seated position on a regular height chair. (Yoshioka;
(2007)) Since design of the WPAL was focused on small size, light weighted and
ability to be used with a wheelchair, the largest torque of the developed knee joint
motor produced 33 N, which was not considered sufficient. However, standing
from a wheelchair with the support of the upper extremities with a walker was
smoothly achieved, and the subject felt that the burden on the upper extremities
was not large.
Recently, as a trial to apply robotic engineering for reconstruction of paraplegic
gait, a system to control knee and hip joints with a motor (RGO) (Ohta; (2007))
and a robot to regulate hip and knee joints (ReWalk) (Medgadget; (2008)) have
been developed. However, taking into account compatibility with a wheelchair, it
would be necessary to develop a robot adopting the medial system.
Consecutive walking distance and time was lengthened several-fold with
WPAL compared with Primewalk. It was presumed that a reduced burden on the
upper extremities during walking enabled continuous walking. Swinging lower
extremities in walking with an orthosis becomes a pendulum movement due to
gravity. Therefore, it is necessary to keep the trunk ahead of the lower extremities
and support most of the weight of the trunk tilted to the anterior side with the
upper extremities using a cane or an orthosis. (Saitoh; (1997)) The addition of
power to the lower extremities can reduce the anterior tilting of the trunk and the
burden on the upper extremities.
Walking with an orthosis without free ROM in knee and foot joints presented a
large problem. Toe clearance can be obtained by knee flexion and ankle dorsiflex-
ion at the initial stage of the swing phase in the normal gait. Sufficient clearance
has not been obtained during the swing because of the extended knee and fixed
ankle joints with an orthosis, making the length of the swing phase equal to that
