In hemiplegic patients, spastic hypertonia of the calf muscle with a greater or lesser degree of paresis or even paralysis of the flexor muscles of the foot (anterior tibial muscle and extensor muscles of the toes) cause the foot to drop when walking. Foot drop can be prevented by electrically induced tetanic contraction of the levator muscles of the foot, synchronized with the phase of the gait during which the foot concerned is lifted from the ground.
The electrical stimulation parameters must be selected so as to obtain a short term tetanic contraction of the anterior compartment of the leg to prevent the foot from dropping, at the appropriate moment and with maximum comfort for the patient.