Measurement of gait parameters from free moving subjects

In this paper a telemetry system for real-time force measurement in the legs and crutches or cane is presented. The system provides a quantitative gait analysis of orthopaedic patients with details, which are often hidden to a visual observation. Three vertical force components in each leg are measured. For this purpose flat and pliable capacitive sensors, which are placed on the sole of the shoes, were developed. The infrared telemetry is applied to enable free and unconstrained movements of the patient inside a wide indoor environment. Measured forces, after transmission and processing on the receiver side, are presented on the computer monitor as eight channel time diagrams. An original software package (GAS) for on-line monitoring and processing of vertical force data was developed. The processing enables calculation of many diagnostically important parameters (e.g. temporal parameters, average force, force-time integral, sum of forces, etc.), spectral and time-frequency analysis and many other. As an example of clinical application,temporal parameters during ten strides for 20 normal subjects and 20 patients with lower extremities degenerative joint diseases were calculated and compared. (C) 2000 Elsevier Science Ltd. All rights reserved.