Yves Stauffer

The WalkTrainer—A New Generation of Walking Reeducation Device Combining Orthoses and Muscle Stimulation

This paper presents a novel reeducation device for paraplegics that combines hybrid orthoses and closed-loop electrical muscle stimulation. Based on the so called cyberthosis concept, the WalkTrainer enables an active muscular participation of the subject in the walking reeducation process by the mean of closed-loop muscle stimulation. The WalkTrainer is also equipped with a leg and pelvic orthosis, an active bodyweight support, and motorized wheels to allow true over ground deambulation. This paper will focus on the development of the WalkTrainer, the presentation of the control strategies, and also give some preliminary results of the first clinical trials.

Design of a new lower extremity orthosis for overground gait training with the WalkTrainer

A new set of lower limb orthoses was developed for the WalkTrainer project. This mobile reeducation device for paralyzed people allows overground gait training combining closed loop electrical muscle stimulation and lower limb guiding while walking. An active body weight support system offers precise body weight unloading during locomotion. A 6 DOF parallel robot moves the pelvis in any desired position and orientation. The lower extremity orthosis is composed of two key parts. First, a purely passive lightweight exoskeleton acts as the interface between the human leg and the machine. A 1 DOF knee orthotic joint is also designed to prevent hyperextension. Second, the active part - composed of a mechanical leg equipped with motors and sensors - is located behind each human leg, with its base fixed to the WalkTrainer base frame. The two kinematic chains are connected with appropriate linkages at the thigh and the ankle joint. Actuation of the hip, knee and ankle joints is thus provided for their flexion/extension axis. The active mechanism operates only within the sagittal plane and guides the ankle-foot subsystem. Thigh and shank add/abduction movements are possible and even essential since the pelvis moves in a 3D space. This achievement prevents the scissors effect while allowing natural walking motion at the other joints. This paper describes the design and development of the lower extremity orthosis. Starting from a biomechanical approach, the needed actuation and the mechanical structure are discussed as well as the interface between the patient and the robot.

Pelvic motion measurement during over ground walking, analysis and implementation on the WalkTrainer reeducation device

Pelvic motions are of great importance while walking, and have thus to be taken into account when developing and controlling rehabilitation devices. This paper will first introduce a new reeducation device for paraplegic people: the WalkTrainer. This device is composed of a leg and pelvic orthosis, an active bodyweight support and closed loop muscle stimulation. Second, the six degrees of freedom (DOF) of the pelvis will be measured by using the WalkTrainer on a population of twenty healthy subjects. Each DOF was successfully measured and can be analyzed as a function of time or gait cycle. Third several models that predict the pelvic motion amplitude as a function of various parameters (speed, size, ...) will be proposed and analyzed. Fourth, pelvic trajectories will be programmed on the WalkTrainer and applied on healthy subjects by the mean of the pelvic orthosis. In that phase one of the previously proposed models will be implemented. A force reduction of 20% is measured on the pelvic orthosis when the pelvic motion amplitude prediction model is used. At last muscle identification and stimulation will be introduced in the future works chapter.

Pelvic motion implementation on the WalkTrainer

Pelvic motion is of great importance when walking, and have thus to be taken into account while developing rehabilitation robotics. This paper describes the implementation of a pelvic motion amplitude prediction model on a pelvic orthosis and tests on valid subjects. Furthermore over ground versus treadmill walking was also performed. For comparison averaged pelvic trajectories were tested against subjects own trajectories. The results showed that the model was valid and that over ground walking resulted in smaller forces applied on the subject.

A Novel Verticalized Reeducation Device for Spinal Cord Injuries: the WalkTrainer, from Design to Clinical Trials

Robotic assistive devices have been developed and are now being introduced in clinical environments. Such robots can advantageously provide long raining, with quantifiable mobilization (force and position). But in the event of a complete lesion the patient’s muscles remain completely passive. To overcome that issue electrical muscle stimulation can be employed. The complex nature of the muscles associated to the dynamics of walking, require subtle stimulation schemes which rely on position and force information provided by the robot. The combination of muscle stimulation (preferably in a closed loop manner to avoid rapid exhaustion and guarantee better control) and robotic mobilization optimizes the afferent feedback provided to the subject and allows an effective muscle training. The WalkTrainer that is one of these reeducation devices, will be extensively presented in this chapter.

CLINICAL TRIALS WITH THE WALKTRAINER: PRELIMINARY RESULTS

Robotic devices are well suited for providing motion to the patient and information (positions, forces, etc.) to the therapist. The FSC and LSRO are combining their effort in the development of robotic re-education devices, focusing on active rehabilitation. A new generation of rehabilitation devices combining mobility, closed loop functional electrical muscle stimulation through force feedback and a compliant mechanical interaction was elaborated. At this time, two devices are developed: the MotionMaker™; a stationary device for functional muscle strengthening and the WalkTrainer™; the mobile rehabilitation device used for this study. Previous clinical results on the MotionMaker™ have demonstrated the enhancement of such concept to paraplegic’s life quality and muscle force increasing. The first clinical trials of the WalkTrainer™ on a population of SCI patients will be presented. These trials are made at the Clinique Romande de Readaptation (CRR) in Sion with the help of medical actors through a predefined protocol.