BIOMECHANICAL MODEL OF THE HUMAN KNEE EVALUATED BY NEUROMUSCULAR STIMULATION

A detailed model of the human knee was developed to predict shank moti on induced by functional neuromuscular stimulation (FNS). A discrete-t ime model is used to characterize the relationship between stimulus pa rameters and muscle activation. A Hill-based model of the musculotendo n actuator accounts for nonlinear static and dynamic properties of bot h muscle and tendon. Muscle fatigue and passive muscle viscosity are m odeled in detail. Moment arms are computed from musculotendon paths of 13 actuators and from joint geometry. The model also takes nonlinear body-segmental dynamics into consideration. The simulated motion is vi sualized by graphic animation. Individual model parameters were identi fied by specific procedures such as anthropometric measurements, a pas sive pendulum test, and specific open-loop stimulation experiments. Mo del results were compared with experimental data obtained by stimulati ng the quadriceps muscle of paraplegic patients with surface electrode s. The knee moment, under isometric conditions, and the knee angle, un der conditions of freely swinging shank, were measured. In view of the good correspondence obtained between model predictions and experiment al data, we conclude that a biomechanical model of human motion induce d by FNS can be used as a mathematical tool to support and accelerate the development of neural prostheses. Copyright (C) 1996 Elsevier Scie nce Ltd.