A new method and instrumentation for analyzing spasticity

Abstract

The assessment of spasticity is an important indicator of the course of the recovery in humans with central nervous system lesion. This recovery may be augmented by optimal ergonomic design of wheelchairs, beds, transferring devices and other devices used in activities of daily life. To quantify the influence of different aids and methods in reduction or increase of spasticity, an objective measure is required. The pendulum test was introduced to induce the stretch of the muscle, thereby, trigger spastic response, and the amplitudes of first sinusoidal movements are used as the measure of spasticity. We present a new model of the lower leg during the pendulum test which includes the nonlinear characteristics of the muscles, and a model of the shank and foot that are customized to the patient. The spastic torque component is calculated based on acquired values of angular acceleration, angular velocity, and angle. We developed a new analysis methodology and tool to describe the level and course of reflexive behavior. We describe the instrumentation for data acquisition. The kinematics is captured by two accelerometers, one gyroscope, and a Hall-effect joint angle encoder. Muscle activities of prime knee flexors and extensors are synchronously recorded. The simulation uses user's particular inertial parameters and data from repeated pendulum movements of the lower leg and outputs the reflexive torque. We developed the user-friendly software in MatLab for the analysis of data recorded with the new instrument. We present the application of the method in representative healthy subject and two spastic SCI patients. The main finding is that this method allows distinction between the flexion and extensions types of spasticity and the level of reflexive behavior.