Evaluation of Gyroscope as a Sensor in Functional Electrical Stimulation or Children with Cerebral Palsy

CATALFAMO FORMENTO, PAOLA

Año: 2009 p. 295

Cerebral Palsy (CP) refers to a motor disorder which affects 2 to 4 per 1000 live births. A common outcome is a imbalance in the muscles that control the ankle resulting in increased effort for walking, risks of falls and possibilities for permanent contractures and deformations. Electrical stimulation has been proposed as a method by which a more normal walking pattern may be achieved. One of the limitations of this approach is the sensor commonly used to start and stop stimulation. Several sensors have been proposed as alternatives, but these have mainly been tested in adults. The key objective of the present work was to evaluate the performance of the gyroscope as a sensor to detect gait events in unimpaired children and those with CP, with particular application during stair and ramp walking. To enable the evaluation to take place, two reference systems were first developed with adults based on kinematic and in-shoe pressure sensing data. Both of these showed accuracy within the predefined values when compared with the force plate. In addition a new algorithm for gait event detection using the gyroscope was also developed. The gyroscope sensor was subsequently evaluated in six unimpaired and two CP children while walking on level ground, and on seven unimpaired children while walking on a path that included level ground walking, ramps and stairs. In both cases, its performance was compared to the reference systems and, when possible, with a conventional footswitch. Overall, the results showed a tendency for the gyroscope to be more accurate for initial contact detection and less accurate for foot off detection that foot switches. The gyroscope was slightly more reliable in ramps and stairs than the foot switch . Additional testing on a larger patient population should be performed before the sensor is used in the clinical environment. If the results of such evaluation support the findings of this study, further work should be directed towards the development of a self - contained unit that includes the stimulator and sensor.