Biology Reference
In-Depth Information
with a cuff electrode implanted in the sural nerve at the ankle (
Haugland &
Sinkjaer, 1999
), or force sensors measuring the components of moment gen-
erated at the ankle joint (
Kottink et al., 2004
).
Walking assistance prostheses
. Several FES systems have been designed and
implanted for assisting standing and walking in paraplegic and stroke
patients. Bilateral programmed systems excite the quadriceps muscle or
the femoral nerve to maintain knee extension for stance in one lower limb,
whereas the other stimulates the common peroneal nerve at a high strength
to elicit a flexion reflex that produces flexion of the hip and knee for the
swing phase in the other limb (
Stein & Mushahwar, 2005
). Some systems
use surface electrodes (
Graupe, Cerrel-Bazo, Kern, & Carraro, 2008;
Popovic & Keller, 2005
), but more advanced ones take use of a variety of
epimysial, intramuscular, and nerve electrodes implanted in the appropriate
muscles or nerves (
Bailey et al., 2010; Guiraud, Stieglitz, Koch, Divoux, &
Rabischong, 2006
). Systems with more electrodes allow for more normal
pattern of walking and may reduce the excessive metabolic demand and
muscle fatigue; moreover, neural stimulation proved to be more efficient,
require less energy, and provide more selective stimulation than muscular
stimulation. Electromyography (EMG) signals recorded from partially con-
trolled muscles can be used to trigger FES-assisted gait initiation that results
more coordinated and stable than with switch-triggered systems (
Dutta,
Kobetic, & Triolo, 2009
).
Hand grasping prostheses
. Restoration of hand function in tetraplegic and
stroke patients is achieved by upper extremity neuroprostheses that use FES
to power hand and arm muscles. A variety of devices send signals via a small
external controller and transmitting coil to an implanted stimulator. The
stimulator activates selected arm and hand muscles via implanted wires
and muscular electrodes. Palmar and lateral grasp, among other functions,
can be reliably restored, leading to significant improvements in ADL
(
Peckham et al., 2001; Popovic, Curt, Keller, & Dietz, 2001; Rupp &
Gerner, 2004
). The hand closure and opening may be commanded using
a position sensor placed on the shoulder of the subject, a push button or pres-
sure sensors. Recent advances have demonstrated improved outcomes of
hand grasping by incorporating start control and proportional control of
grasp strength from EMG signals recorded in shoulder and arm muscles
(
Kilgore et al., 2008
), or by providing sensory feedback to the system by
neural signals recorded with cuff electrodes around digital nerves
(
Inmann & Haugland, 2004
). Exciting ongoing research aims to bring such
a hand neuroprosthesis under volitional control from either noninvasive
