Yutaka Tomita, RE, PhD, Genichi Tanino, RPT, Shiho Mizuno, MD, PhD, Hirofumi Maeda, MD, Hiroyuki Miyasaka, OTR, PhD, Orand Abbas, RE, PhD,
Kotaro Takeda, RE, PhD, Shigeru Sonoda, MD, PhD
Jpn J Compr Rehabil Sci 5: 147-155, 2014
Objective: This research aimed to develop a system to
measure the stiffness of the ankle joint for evaluating
spasticity or contracture, and for quantifying the
characteristics of spasticity. Functionality of the
system was verified by testing it on an able-bodied
individual and a hemiplegic patient. Additionally, a
biomechanical model was developed to estimate the
plantar flexion torque caused by viscoelasticity and
muscle contraction.
Methods: An electromotor, rack and pinion,
potentiometer, and torque sensor were installed on a
double Klenzak ankle-foot orthosis (AFO). By rotating
the electromotor, the ankle joint of the AFO moves
dorsally at a fixed speed. The angle and torque of
dorsiflexion were measured simultaneously. The
subjects sat either in a chair or a wheelchair and wore
the abovementioned AFO in the knee-extension and
knee-flexion positions, while the AFO moved dorsally.
Electromyograms of the tibialis anterior and
gastrocnemius muscles were recorded concurrently.
The contributions of elastic, viscous, and musclecontraction
components to the plantar flexion torque
were calculated using the system identification
approach.
Results: The system’s ability to measure dynamic
characteristics, and also its accuracy, were confirmed.
The plantar flexion torque was found to be larger in the
knee-extension position than in the knee-flexion
position in both the able-bodied person and the patient.
Moreover, the patient showed larger plantar flexion
torque than the able-bodied subject.
Conclusions: A system that measures ankle-joint
stiffness for evaluating spasticity was developed, and
sufficient functionality was verified by applying it to
both an able-bodied individual and a hemiplegic
patient. In addition, plantar flexion torque caused by
viscoelasticity and muscle contraction was estimated.
Key words: joint stiffness, quantification, viscoelasticity, electromyogram, spasticity