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The 3 months clinical trial successfully ended aht the Clinique Romande de Réadaptation (CRR).
Cyberthoses @ LSRO
Robotic assistance offers the possibility of performing therapeutic mobilization treatments on paralyzed people. The LSRO is working on a challenging locomotor re-education project that combines functional orthoses and Functional Electrical Stimulation (FES): the “Cyberthoses” project.
Palsy can be traced back to a lesion of the Central Nervous System (CNS). The effects are: immobility and serious medical complications. The latter can be prevented by a mobilization of the paralyzed limbs and by maintaining the musculature with physiotherapeutic exercises or fitness training. New ways of training are now available; these are based on neuromuscular stimulation or Functional Electrical Stimulation (FES). To be effective, such training must stimulate the muscles in a pattern that is as natural as possible, and the forces have to be equivalent to those encountered during natural activity. The kinematics and dynamics of the articular displacements generated by the FES must be close to the physiological movements.
Closed-loop control of the electrically-stimulated muscular contractions is thus mandatory for the realization of complex and repetitive movements such as cycling and leg-press. Such control is achieved by combining FES with an orthosis equipped with motors and sensors. The benefit of this technique is the achievement of a progressive and active muscular participation. Thus, prevention of the problems linked to palsy, and the enhancement of the re-education of the affected limbs, is achieved.
MotionMaker: a stationary device for the mobilization of lower limbs; associating functional orthoses and FES.
Conception of locomotor re-education and walking assistance devices with the combination of a functional orthosis and closed-loop FES.
In re-education it is essential to perform a movement or a set of movements not only precisely, but also in a physiologically correct way. Treadmill training is the outcome of this request for walking re-education. This technique is both tiring and time-consuming for the therapists. Furthermore, the difficulty of control increases with the severity of the patient’s lesion. Robotization of the re-education training allows a better reproduction of the physiological walking pattern. However, the active muscular contribution for this kind of re-education is still limited by the subject’s residual motor activity. Also, the dynamics of treadmill walking are different from overground walking. Proprioceptive information is also biased if walking is performed on a treadmill. The bottom line is that during such training the locomotor patterns will be different from normal walking.
The Swiss Foundation for Cyberthosis (SFC) aims to create new re-education methods. A research program has been initiated, with the goal of developing locomotor re-education and walking assistance devices that combine functional orthoses and closed-loop FES. Acceleration of the re-education process by an active muscular contribution is sought while keeping the physiological dynamical effects of natural walking.
WalkTrainer: mobile equipment for verticalization and locomotion
A deambulator is currently being developed. Hip biomechanics will be investigated using the simplified prototype currently available. Motricity and direction control of the system will also be developed on this prototype. Furthermore, an adaptative active body-weight support apparatus will also be tested. Finally, a hip orthosis design is ongoing as well as a two-leg orthosis that will complete the system.
The MotionMaker :stationary mobilization and muscle strengthening system
In a second phase a complete device was developed: the MotionMaker. This apparatus is equipped with two complete lower limb orthoses. The controller allows a simultaneous control of the three articulations (hip, knee and ankle) and of the seven muscles (rectus femoris, vastus lateralis, vastus medialis, gluteus maximus, hamstrings, tibialis anterior and gastrocenmius) of each leg. Electro-stimulated bilateral leg-press movements were tested on healthy subjects. Optimization and validation of the closed-loop control on Spinal Cord Injured (SCI) people are ongoing.
The MotionMaker can also be used for medical diagnostics. Mobility, speed, voluntary force and plasticity can be measured and analyzed.
Futur project WalkMaker: walking Cyberthosis enabling autonomous walking with closed-loop FES
As depicted, this device is light-weight and its development is aimed towards incomplete SCI; to bring a complementary FES to the voluntary muscular activity still available.
First, a robotized knee orthosis prototype was built. Control of the knee flexion/extension was provided by an electric motor; helping the movement or creating resistance was thus possible. Built-in sensors provided the controller and stimulator with real-time knee torque and angular position. These values were used to provide a precise control of the motor-generated torque and the stimulation of the quadriceps muscles as a function of the chosen kinematic and dynamic parameters. This prototype confirmed the possibility of using closed-loop FES on healthy subjects as well as on para/ tetraplegic subjects.
In order to fulfill the needs and requirements of the FES, a high performance electrostimulator was developed. Twenty modular and independent channels are available. A central unit can control in real time the parameters of each channel by a standard serial link. Each channel delivers biphasic symmetric current pulses up to 100mA. The frequency and the pulse width are adjustable from 10 to 85Hz and 100 to 300µs respectively. Parasitic current flow between electrode pairs is avoided because each output is electrically floating. The main concern is the security of the subject. Indeed, several hardware and software securities were implemented, such as: pulse timeout, programmable current limitation, command order test, communication test.