Asymmetry in sit-to-stand movement in patients following transtibial amputation and healthy individuals.

The aim of this study was to analyse the asymmetry of sit-to-stand (STS) movement in a group of subjects following unilateral transtibial amputation (STTA) and a group of healthy subjects (HSs). Experimental measurements investigated standing-up pattern from two seat heights and at three different speeds. Body motion was measured using an optical measuring system with active markers. Floor and seat reaction forces and moments were measured by two force plates and an integrated force-moment sensor. Analysis of ankle, knee, hip and trunk inclination angles shows that STTA perform STS movement with different initial foot placement than HS, resulting in different lower extremity loadings and larger trunk inclination. Asymmetry was defined as the difference between left and right extremity parameters averaged throughout STS movement. A root-mean-square error was used to assess the asymmetry in ground reaction forces and in ankle, knee and hip angles and moments. The influence of different seat heights and velocities on asymmetry was tested using one-way ANOVA. The asymmetry of STTA and HS was affected neither in kinematic nor in kinetic parameters. Performing STS at higher speeds was found to result in decreased trunk flexion. The asymmetry assessment, as determined in this study, can be used in rehabilitation for improving STS strategies or as an evaluation tool for estimating the progress of the rehabilitation process.

Rehabilitation robotics.

The paper presents the background, main achievements and components of rehabilitation robotics in a simple way, using non-technical terms. The introductory part looks at the development of robotic approaches in the rehabilitation of neurological patients and outlines the principles of robotic device interactions with patients. There follows a section on virtual reality in rehabilitation. Hapticity and interaction between robot and human are presented in order to understand the added value of robotics that cannot be exploited in other devices. The importance of passive exercise and active tasks is then discussed using the results of various clinical trials, followed by the place of upper and lower extremity robotic devices in rehabilitation practice. The closing section refers to the general importance of measurements in this area and stresses quantitative measurements as one of the advantages in using robotic devices.

Assessment of reach-to-grasp trajectories toward stationary objects.

BACKGROUND: Patients with pronounced spasticity reveal difficulties in hand opening during the approaching grasping phase. The general description and assessment procedures of reach-to-grasp movement for rehabilitation purposes is still not established. There is a necessity to develop a universal methodology to describe the approaching phase in grasping which would allow clinical evaluation of movement pathologies. METHODS: In the paper, the evaluation of approaching trajectories assessed during grasping by healthy subjects is described. The experiment, undertaken by 7 healthy volunteers, consisted of grasping three different stationary objects positioned in various poses by a robot. 3D recordings of the hand and fingertip trajectories were performed. The kinematic trajectories of the hand and finger markers were analysed in order to evaluate the reach-to-grasp movement. FINDINGS: The results of the kinematic analysis suggest that the reach-to-grasp movement of a healthy subject can be divided into 3 dominant phases (hand acceleration, hand deceleration, and final closure of the fingers). INTERPRETATION: The presented evaluation method can provide relevant information on the modalities the hand preshapes and approaches toward the object in order to obtain a stable grasp. The potential use of the approach for rehabilitation purposes is discussed.

Real-time 3D avatars for tele-rehabilitation in virtual reality.

We present work in progress on a tele-immersion system for telerehabilitation using real-time stereo vision and virtual environments. Stereo reconstruction is used to capture user's 3D avatar in real time and project it into a shared virtual environment, enabling a patient and therapist to interact remotely. Captured data can also be used to analyze the movement and provide feedback to the patient as we present in a preliminary study of stepping-in-place task. Such tele-presence system could in the future allow patients to interact remotely with remote physical therapist and virtual environment while objectively tracking their performance.

VI.2. Basic functional electrical stimulation (FES) of extremites - an engineer's view.

The historical development of electrical stimulators producing contraction of paralyzed muscles is briefly presented. The influence of electrical stimulation parameters (amplitude of pulses, frequency, pulse duration, and duration of a pulse train) is explained. Special attention is paid to the description of the muscle recruitment curve. The phenomenon of reversed recruitment order, resulting in fatiguing of electrically stimulated muscle, is presented. The properties of surface electrodes (electrode size, polarity, resistance, and distance between electrodes) are examined. The use of surface electrodes made of metal plate or wire mesh, silicone impregnated with rubber, and conductive adhesive gel are discussed. The design of electrical stimulator circuits is also presented.

VI.3. Rehabilitation robotics.

The paper presents the background, main achievements and components of rehabilitation robotics in a simple way, using non-technical terms. The introductory part looks at the development of robotic approaches in the rehabilitation of neurological patients and outlines the principles of robotic device interactions with patients. There follows a section on virtual reality in rehabilitation. Hapticity and interaction between robot and human are presented in order to understand the added value of robotics that cannot be exploited in other devices. The importance of passive exercise and active tasks is then discussed using the results of various clinical trials, followed by the place of upper and lower extremity robotic devices in rehabilitation practice. The closing section refers to the general importance of measurements in this area and stresses quantitative measurements as one of the advantages in using robotic devices.

Force exertion capacity measurements in haptic virtual environments.

An objective test for evaluating functional status of the upper limbs (ULs) in patients with muscular distrophy (MD) is presented. The method allows for quantitative assessment of the UL functional state with an emphasis on force exertion capacity. The experimental measurement setup and the methodology for the assessment of maximal exertable force utilizing the Phantom 1.5 haptic interface has been developed. The measurement setup consists of a powerful virtual reality simulator, capable of providing haptic, visual and audio feedback. The patient's task in the virtual environment is goal oriented and includes stretching a virtual spring in six different directions. The Phantom 1.5 haptic interface serves as a kinematic measuring device and as a force feedback generator. By moving the haptic interface control stick the patient exerts the force in six radial directions to the best of his or her abilities. The new test offers numerical as well as graphic results. The method has been applied to 32 MD patients. Several typical force exertion capacity characteristics, affected by neuro-muscular disorders are shown in a quantitative manner. Data mining was used to demonstrate good content validity of the proposed test. The method allows for a quick, accurate, repeatable and objective measurements of the UL force exertion capability.

Comparison of four evaluation approaches in transcutaneous electrical nerve stimulation treatment in two incomplete tetraplegic subjects.

INTRODUCTION: In the present investigation, we applied the whole-hand transcutaneous electrical nerve stimulation (TENS) therapy to two incomplete tetraplegic subjects and assessed their progress with four evaluation methods. METHODS: Two spinal cord injured subjects with spastic upper extremities participated in the study. The TENS therapy was added to their regular treatment. The TENS was delivered to the subject's hands by a conductive glove. The therapy consisted of 20-min sessions each working day during a period of four weeks. The used assessment methods were: maximal force test, force tracking task, Jebsen-Taylor hand function test, and modified Ashworth scale. RESULTS: The results show increased finger muscle strength, improved motor control and hand function in both patients. The reduction of muscle tone, as assessed by the modified Ashworth scale, was observed in one subject. DISCUSSION: There was no correlation found between the Jebsen-Taylor test and the maximal force test or force tracking task in this investigation. Assessment methods are complementary to each other as each one adds new or more detailed information about level of impairment. CONCLUSION: From the comparison of four evaluation methods, it is evident that different assessments and measurements should be used in order to get better picture of patient's upper extremity impairment.

Basic functional electrical stimulation (FES) of extremities: an engineer's view.

The historical development of electrical stimulators producing contraction of paralyzed muscles is briefly presented. The influence of electrical stimulation parameters (amplitude of pulses, frequency, pulse duration, and duration of a pulse train) is explained. Special attention is paid to the description of the muscle recruitment curve. The phenomenon of reversed recruitment order, resulting in fatiguing of electrically stimulated muscle, is presented. The properties of surface electrodes (electrode size, polarity, resistance, and distance between electrodes) are examined. The use of surface electrodes made of metal plate or wire mesh, silicone impregnated with rubber, and conductive adhesive gel are discussed. The design of electrical stimulator circuits is also presented.

Design and evaluation of a functional electrical stimulation system for hand sensorimotor augmentation.

The aim of this study was to perform a preliminary evaluation of a new method for therapeutic exercise of grasping in patients with upper limb disability. The new method combines active voluntary exercise augmented with electrical stimulation and controlled by using force feedback. The feedback has two functions: automatic control of the intensity of electrical stimulation by minimizing the tracking error, and biofeedback to the patient on the computer screen. The force feedback is realized by the use of a newly designed adjustable hand force measuring device, which comprises two force sensors. The therapy requires from patients to volitionally try to open and close the hand while tracking the target on the screen. The system was evaluated in a pilot study in five healthy and two chronic incomplete tetraplegic subjects. Results in healthy subjects were used for reference and for stimulation controller evaluation. The therapy in incomplete tetraplegic subjects of 45-min daily session delivered during four weeks. The results of pilot study show that augmentation of voluntary grip force control with presented system is possible.

Virtual environment for lower-extremities training.

This study proposed virtual reality (VR) as a modality of lower-extremities training. A kinematic model of a human body and a corresponding virtual figure were developed, in order to visualize the movements of the subject in a real-time virtual environment on a large display, which represented a virtual mirror. An optical system with active markers was used to assess the movements of a training subject. A preliminary investigation was conducted with a group of healthy male subjects, who performed the stepping-in-place test by tracking the movements of the reference virtual figure, which represented a virtual instructor. Both figures were shown in the virtual mirror at the same time from the desired angle of view. Four stepping tasks featuring different cadences and hip angles were performed, with difficulty levels ranging from easy to demanding. The results obtained included basic kinematic and temporal parameters, which provided quantitative measures of a subject's adaptation to the virtual training environment, and thereby justifying the feasibility of the virtual mirror as a useful system in lower-extremities training applications.

Human voluntary activity integration in the control of a standing-up rehabilitation robot: a simulation study.

The paper presents a novel control approach for the robot-assisted motion augmentation of disabled subjects during the standing-up manoeuvre. The main goal of the proposal is to integrate the voluntary activity of a person in the control scheme of the rehabilitation robot. The algorithm determines the supportive force to be tracked by a robot force controller. The basic idea behind the calculation of supportive force is to quantify the deficit in the dynamic equilibrium of the trunk. The proposed algorithm was implemented as a Kalman filter procedure and evaluated in a simulation environment. The simulation results proved the adequate and robust performance of "patient-driven" robot-assisted standing-up training. In addition, the possibility of varying the training conditions with different degrees of the subject's initiative is demonstrated.

Biomechanical characterization and clinical implications of artificially induced toe-walking: differences between pure soleus, pure gastrocnemius and combination of soleus and gastrocnemius contractures.

The purpose of this study was to characterize biomechanically three different toe-walking gait patterns, artificially induced in six neurologically intact subjects and to compare them to selected cases of pathological toe-walking. The subjects, equipped with lightweight mechanical exoskeleton with elastic ropes attached to the left leg's heel on one end and on shank and thigh on the other end in a similar anatomical locations where soleus and gastrocnemius muscles attach to skeleton, walked at speed of approximately 1m/s along the walkway under four experimental conditions: normal walking (NW), soleus contracture emulation (SOL), gastrocnemius contracture emulation (GAS) and emulation of both soleus and gastrocnemius contractures (SOLGAS). Reflective markers and force platform data were collected and ankle, knee and hip joint angles, moments and powers were calculated using inverse dynamic model for both legs. Characteristic peaks of averaged kinematic and kinetic patterns were compared among all four experimental conditions in one-way ANOVA. In the left leg SOL contracture mainly influenced the ankle angle trajectory, while GAS and SOLGAS contractures influenced the ankle and knee angle trajectories. GAS and SOLGAS contractures significantly increased ankle moment during midstance as compared to SOL contracture and NW. All three toe-walking experimental conditions exhibited significant power absorption in the ankle during loading response, which was absent in the NW condition, while during preswing significant decrease in power absorption as compared to NW was seen. In the knee joint SOL contracture diminished, GAS contracture increased while SOLGAS contracture approximately halved knee extensor moment during midstance as compared to NW. All three toe-walking experimental conditions decreased hip range of motion, hip flexor moment and power requirements during stance phase. Main difference in the right leg kinematic and kinetic patterns was seen in the knee moment trajectory, where significant increase in the knee extensor moment took place in terminal stance for GAS and SOLGAS experimental conditions as compared to SOL and NW. The kinetic trajectories under SOL and GAS experimental conditions were qualitatively compared to two selected clinical cases showing considerable similarity. This implies that distinct differences in kinetics between SOL, GAS and SOLGAS experimental conditions, as described in this paper, may be clinically relevant in determining the relative contribution of soleus and gastrocnemius muscles contractures to toe-walking in particular pathological gait.

Estimation of hand preshaping during human grasping.

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.

Grip force tracking system for assessment and rehabilitation of hand function.

The aim of the paper is to present a novel tracking system for the assessment and training of grip force control. The system consists of two force measuring units of different shapes, which can be connected to a personal computer for visual feedback and data acquisition. We present the results of the assessment of the grip force control in 32 healthy subjects of different age groups and preliminary results obtained in a patient after head-injury who was treated with Botulinum-Toxin for hand spasticity. The proposed tracking system was also applied as a training tool in 10 post-stroke patients to possibly improve their grip force control. The results in healthy subjects showed significant differences in grip force control among different age groups. In the patient after Botulinum-Toxin treatment the method revealed noticeable effects of the therapy on the patient's tracking performance. Training with the tracking system showed considerable improvements in the grip force control in 8 out of 10 stroke patients. The proposed tracking method is aimed to be used in connection with different rehabilitation therapies (e.g. physiotherapy, functional electrical stimulation, drug treatment) to follow the influence of the therapy on patient's muscular strength and grip force control.

Sensory supported FES control in gait training of incomplete spinal cord injury persons.

Sensory supported electrical stimulation of the peroneal nerve during treadmill walking is proposed as a gait-training modality in incomplete spinal cord injury (SCI) patients. A multisensor device provides information on the tilt of the shank during gait. The information provided significantly improves the triggering instant of the electrical stimulation. Simultaneously, swing-phase estimation serves as a reference to determine the required motor augmentation support. Both approaches, as well as triggering using intensity control of the functional electrical stimulation were applied on a healthy person and on an incomplete C4-5 SCI patient.

Nonlinear modeling of FES-supported standing-up in paraplegia for selection of feedback sensors.

This paper presents analysis of the standing-up manoeuvre in paraplegia considering the body supportive forces as a potential feedback source in functional electrical stimulation (FES)-assisted standing-up. The analysis investigates the significance of arm, feet, and seat reaction signals to the human body center-of-mass (COM) trajectory reconstruction. The standing-up behavior of eight paraplegic subjects was analyzed, measuring the motion kinematics and reaction forces to provide the data for modeling. Two nonlinear empirical modeling methods are implemented--Gaussian process (GP) priors and multilayer perceptron artificial neural networks (ANN)--and their performance in vertical and horizontal COM component reconstruction is compared. As the input, ten sensory configurations that incorporated different number of sensors were evaluated trading off the modeling performance for variables chosen and ease-of-use in everyday application. For the purpose of evaluation, the root-mean-square difference was calculated between the model output and the kinematics-based COM trajectory. Results show that the force feedback in COM assessment in FES assisted standing-up is comparable alternative to the kinematics measurement systems. It was demonstrated that the GP provided better modeling performance, at higher computational cost. Moreover, on the basis of averaged results, the use of a sensory system incorporating a six-dimensional handle force sensor and an instrumented foot insole is recommended. The configuration is practical for realization and with the GP model achieves an average accuracy of COM estimation 16+/-1.8 mm in horizontal and 39+/-3.7 mm in vertical direction. Some other configurations analyzed in the study exhibit better modeling accuracy, but are less practical for everyday usage.

Synthesis of standing-up trajectories using dynamic optimization.

Dynamic optimization as a tool to compute standing-up trajectories was investigated. Sit-to-stand manoeuvres in five intact persons and five trans-femoral amputees were measured. Movements and ground reaction forces acting on the body were recorded. A five-segment 3D dynamic model of standing-up was developed. In each particular subject, the optimization criterion which yielded trajectories that best resemble the measured standing-up movement was determined. Since the intact persons used considerably different criteria in choosing the standing-up trajectories than the amputees, the optimal trajectories were computed by minimizing cost functionals (CF) with distinctive structures for each group of individuals. In intact persons, a unique cost functional was found which yielded realistic standing-up manoeuvres. In amputees, subject-specific sets of parameters indicating slightly different preferences in optimizing the effort of particular muscle groups were used.

Muscle contracture emulating system for studying artificially induced pathological gait in intact individuals.

When studying pathological gait it is important to correctly identify primary gait anomalies originating from damage to the central nervous and musculoskeletal system and separate them from compensatory changes of gait pattern, which is often challenging due to the lack of knowledge related to biomechanics of pathological gait. A mechanical system consisting of specially designed trousers, special shoe arrangement, and elastic ropes attached to selected locations on the trousers and shoes is proposed to allow emulation of muscle contractures of soleus (SOL) and gastrocnemius (GAS) muscles and both SOL-GAS. The main objective of this study was to evaluate and compare gait variability as recorded in normal gait and when being constrained with the proposed system. Six neurologically and orthopedically intact volunteers walked along a 7-m walkway while gait kinematics and kinetics were recorded using VICON motion analysis system and two AMTI forceplates. Statistical analysis of coefficient of variation of kinematics and kinetics as recorded in normal walking and during the most constrained SOL-GAS condition showed comparable gait variability. Inspection of resulting group averaged gait patterns revealed considerable resemblance to a selected clinical example of spastic diplegia, indicating that the proposed mechanical system potentially represents a novel method for studying emulated pathological gait arising from artificially induced muscle contractures in neurologically intact individuals.

Force tracking system for the assessment of grip force control in patients with neuromuscular diseases.

BACKGROUND: The majority of hand functionality assessment methods consist of the maximal voluntary grip force measurement. Additional knowledge on sensory-motor control can be obtained by capturing functional grip force in a time frame. Tracking methods have been successfully used for the assessment of grip force control in stroke patients and patients with Parkinson's disease. METHODS: A novel tracking system for the evaluation of grip force control is presented. The system consists of a grip-measuring device with the end-objects of different shapes which was used as input to a tracking task where the patient applied the grip force according to the visual feedback. The grip force control was assessed in 20 patients with neuromuscular diseases and 9 healthy subjects. The performance of two tracking tasks was analysed in five grips. The ramp-tracking task was designed to assess the grip strength and muscle fatigue. The sinus-tracking task was used to evaluate grip force control during periodic muscle activation. FINDINGS: The results suggest that in some patients the disease did not affect their grip force control despite evident muscular weakness. Most patients produced larger tracking errors in precision grip while the healthy subjects showed less significant differences in performance among the grips tested. INTERPRETATION: The current study investigated force control in patients with neuromuscular diseases where detection of small changes in motor performance is important when following the progress of disease. The presented evaluation method can provide additional information on muscle activation and fatigue as compared to traditional grip strength testing.