Pendulum test: Quantified assessment of the type and level of spasticity in persons with central nervous system lesions

The development of a comprehensive computational model of the pendulum test which is appropriate for the analysis of the pathologic behavior of the leg in humans with the central nervous system (CNS) lesion is presented in this review. The model relates to the pendulum movement of the lower leg (shank and the foot) in the lateral plane due to the gravity and involuntary contractions of the muscles. The viscous damping and elastic stiffness reflect the soft tissues and friction in the knee joint. To quantify the pathologic activity of paralyzed muscles a reflex torque was added to the gravity generated knee joint torque. The knee joint encoder, accelerometers and gyroscopes positioned along the shank and thigh, and EMG amplifiers were used to acquire data for the illustration of the validity of the model. We show that the linear model of the movement of the lower leg is not a good representation of the motor impairment. We show that the model expanded with the reflex torque affecting the movement is well suited for the pendulum analysis. The timing of the reflex torques can be determined from the EMG recordings. © Serbian Journal of Electrical Engineering. 2018

A tool for the evaluation of human lower arm injury: approach, experimental validation and application to safe robotics

This paper treats the systematic injury analysis of lower arm robot–human impacts. For this purpose, a passive mechanical lower arm (PMLA) was developed that mimics the human impact response and is suitable for systematic impact testing and prediction of mild contusions and lacerations. A mathematical model of the passive human lower arm is adopted to the control of the PMLA. Its biofidelity is verified by a number of comparative impact experiments with the PMLA and a human volunteer. The respective dynamic impact responses show very good consistency and support the fact that the developed device may serve as a human substitute in safety analysis for the described conditions. The collision tests were performed with two different robots: the DLR Lightweight Robot III (LWR-III) and the EPSON PS3L industrial robot. The data acquired in the PMLA impact experiments were used to encapsulate the results in a robot independent safety curve, taking into account robot's reflected inertia, velocity and impact geometry. Safety curves define the velocity boundaries on robot motions based on the instantaneous manipulator dynamics and possible human injury due to unforeseen impacts. Copyright © Cambridge University Press 201

A new method and instrumentation for analyzing spasticity

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

Control of triceps surae stimulation based on shank orientation using a uniaxial gyroscope during gait

This article presents a stimulation control method using a uniaxial gyroscope measuring angular velocity of the shank in the sagittal plane, to control functional electrical stimulation of the triceps surae to improve push-off of stroke subjects during gait. The algorithm is triggered during each swing phase of gait when the angular velocity of the shank is relatively high. Subsequently, the start of the stance phase is detected by a change of sign of the gyroscope signal at approximately the same time as heel strike. Stimulation is triggered when the shank angle reaches a preset value since the beginning of stance. The change of angle is determined by integrating angular velocity from the moment of change of sign. The results show that the real-time reliability of stimulation control was at least 95% for four of the five stroke subjects tested, two of which were 100% reliable. For the remaining subject, the reliability was increased from 50% found during the experiment, to 99% during offline processing. Our conclusion is that a uniaxial gyroscope on the shank is a simple, more reliable alternative to the heel switch for the purpose of restoring push-off of stroke subjects during gait

Pendulum test: Quantified assessment of the type and level of spasticity in persons with central nervous system lesions

The development of a comprehensive computational model of the pendulum test which is appropriate for the analysis of the pathologic behavior of the leg in humans with the central nervous system (CNS) lesion is presented in this review. The model relates to the pendulum movement of the lower leg (shank and the foot) in the lateral plane due to the gravity and involuntary contractions of the muscles. The viscous damping and elastic stiffness reflect the soft tissues and friction in the knee joint. To quantify the pathologic activity of paralyzed muscles a reflex torque was added to the gravity generated knee joint torque. The knee joint encoder, accelerometers and gyroscopes positioned along the shank and thigh, and EMG amplifiers were used to acquire data for the illustration of the validity of the model. We show that the linear model of the movement of the lower leg is not a good representation of the motor impairment. We show that the model expanded with the reflex torque affecting the movement is well suited for the pendulum analysis. The timing of the reflex torques can be determined from the EMG recordings. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR35003

Medical Engineering Physics 27 (2005) 790--797

A new method for evaluating hand preshaping during reaching-to-grasp movement is proposed. The method makes use of all five fingers in estimation of prehension. The investigation was performed on six healthy subjects grasping three different objects at various positions and orientations. The objects were presented to the subjects by means of a robot, which also induced perturbations in both object position and orientation. Positions of markers attached to the finger-tips and dorsum of the hand were recorded by means of a 3D optical tracking system. In the data analysis, the adjacent fingertips were interconnected, thus obtaining a planar pentagon whose various characteristics were investigated and discussed. New parameters for the evaluation of finger preshaping, such as pentagon surface area, angle between the pentagon and hand normal vectors, and the angle between the pentagon and object normal vectors were introduced. The proposed pentagon approach is expected to be useful in future work when examining grasping abilities of subjects with neuromuscular disorders