Y. Shimada et al., Closed-loop control using a stretch sensor for restoration of standing with functional electrical stimulation in complete paraplegia, TOH J EX ME, 193(3), 2001, pp. 221-227
A closed-loop control system for standing with functional electrical stimul
ation (FES) using percutaneous intramuscular electrodes in complete paraple
gia is described. The system consisted of ultrafine percutaneous intramuscu
lar electrodes, a 32-channel stimulator and a stretch sensor with active cu
rrent control. to detect knee buckling. The closed-loop control system was
applied in a T8 completely paraplegic patient. Compared to the stretch sens
or with a wide use flexible goniometer for direct current control during st
anding, the stretch sensor was superior to the flexible goniometer in both
ease of use and response. The average time delay from the start of knee buc
kling until the sensor turned on was 0.56 +/-0.19 seconds (Mean +/-S.D.) in
the goniometer and 0.21 +/-0.06 seconds in the stretch sensor. The average
time delay from the start of knee buckling until the recovery from knee bu
ckling was 1.01 +/-0.05 seconds in the goniometer and 0.78 +/-0.06 seconds
in the stretch sensor. The continuous standing ability of the patient incre
ased from 12 minutes with open-loop stimulation to 30 minutes with the clos
ed-loop control. No complications such as falling occurred during clinical
use. This system prevented falling due to knee buckling during standing and
prolonged upright; activities in complete paraplegics.