The Parastep System - Advanced Biometric Research Center :: Home

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16. Transcutaneous FES
for Ambulation :
The Parastep System
BMSIL, SNU
Jong Min, Lee
16. Transcutaneous FES for Ambulation : The Parastep System
Contents
1.
Introduction and Background
– Historical Background
– Brief Review of FES system for Ambulation by Paraplegics.
2.
The Parastep System
– System’s Electric Charge and Charge Density Parameters
– System Parameters and Design
3.
Patient Admissibility, Contraindications, and Training
– Patient Admissibility
– Contraindications
– Patient Training
4.
Walking performance and Medical and Psychological Benefits
Evaluation results
– Waling Performance Data
– Evaluation Result on Medical Benefits for Walking with the Parastep System
– Psychological Outcome Evaluation Results
5.
6.
Regulatory status
Conclusions
Commercial FES
개인용FES자극기/근육통완화자극기/저주파자극기
기능적전기자극치료기, FES, Microstim, 마이크로스팀
6,600,000원
163,000원
FES 저주파패치
TENS : transcutaneous electrical nerve stimulation
경피 신경 전기 자극 (전류로 피부의 말초 감각 신경을 자극하여 통증을 치료하는 방법)
FES : functional electrical stimulation
기능적 전기 자극 (중추신경계 환자에게 사용)
3/37
Spinal Cord Injury
Cervical - tetraplegia (Quadriplegia)
Injuries at the C-1/C-2 levels will often result in loss of
breathing, necessitating mechanical ventilators or
phrenic nerve pacing.
C3 vertebrae and above : Typically results in loss
of diaphragm function, necessitating the use of a
ventilator for breathing.
C4 : Results in significant loss of function at the
biceps and shoulders.
C5 : Results in potential loss of function at the
shoulders and biceps, and complete loss of
function at the wrists and hands.
C6 : Results in limited wrist control, and complete
loss of hand function.
C7 and T1 : Results in lack of dexterity in the
hands and fingers, but allows for limited use of
arms
4/37
Spinal Cord Injury
Thoracic - paraplegia.
T1 to T8 : Results in the inability to control the
abdominal muscles. Accordingly, trunk stability is
affected. The lower the level of injury, the less
severe the effects.
T9 to T12 : Results in partial loss of trunk and
abdominal muscle control
Lumbarsacral
The effects of injuries to the lumbar or sacral
regions of the spinal cord are decreased control
of the legs and hips, urinary system, and anus.
cf > Hemiplegia
– commonly caused by of brain damage
5/37
Upper motor neuron
Upper motor neurons
motor neurons that originate in the
motor region of the cerebral cortex or
the brain stem and carry motor
information down to the final common
pathway, that is, any motor neurons that
are not directly responsible for
stimulating the target muscle.
6/37
Upper motor neuron
Upper motor neuron lesion
a lesion of the neural pathway above the
anterior horn cell or motor nuclei of the
cranial nerves.
This is in contrast to a lower motor
neuron lesion, which affects nerve fibers
traveling from the anterior horn of the
spinal cord to the relevant muscle(s).
7/37
Historical Background
Kantrowitz et al. (1960)
first application to a paraplegic patient
Lieberson et al. (1961)
first demonstrated modern application of FNS
to hemiplegic patient
Kralj et al. (1980)
unbraced short-distance ambulation by
transcutaneous FNS of a complete paraplegic
Graupe et all (1982)
first patient-controlled ambulation for a
complete paraplegic patient employing EMG
Luigi Galvani, 1737-1798
Parastep FNS (1982)
manually controlled system
Received FDA approval in 1994
8/37
Historical Background (cont.)
• Neuromuscular stimulation for limb movement
– 1961 : 1stFES for paralyzed limb
• For foot drop with stimulation over peroneal nerve
– 1963 : FES controlled finger extension
• Control of grasp in the paralyzed limb
– 1960 : Assisted gait in the spinal cord injured
• Rising, standing, walking & sitting -> Parastep
– 1989 : Hand grasp restoration in cervical SCI
• Using contralateral shoulder motion -> Freehand
9/37
DFS : drop foot stimulator
(Cf> parastep : both standing and ambulation)
The development of FES-based drop foot
correction has gone through the following
evolutionary stages:
Liberson’s DFS arrangement.
(Liberson et al. 1961)
• hard-wired single-channel surface DFS
• hard-wired multichannel surface DFS
• hard-wired single-channel implanted DFS
• microprocessor-based surface and implanted
DFS
• artificial and “natural” sensors as replacement
for the footswitch
• DFS systems incorporating real-time control of
FES
• completely implanted DFS systems
10/37
DFS : drop foot stimulator
MOV
11/37
Historical Background(cont.)
Sigmedics Inc. (founded for this purpose in 1987)
Commercialized Parastep system(Parastep-1 system)
Received FDA approval in 1994
Medicare/Medicaid for reimbursement in 2003
About 1000 patients are or have been able to ambulate over short distance .
More than 20 hospital in US and Europe.
No known detrimental effect.
12/37
Brief Review of FES System for Ambulation by Paraplegics
•
Noninvasive (transcutaneous) FES system
–
–
For both standing and ambulation
For Drop foot stimulation (DFS)
•
Hybrid FES-Long-Leg Brace Ambulation system
•
Implanted FES Ambulation System
13/37
•
For both standing and ambulation
Ljubljana FES system is unique aside from parastep.
-University of Ljubljana, Slovenia
But not commercialized and not FDA approved.
1976
2008
The improved six-channel
stimulator from the Ljubljana
group. (Stanic et al. 1978)
14/37
•
For Drop foot stimulatoin (DFS)
WalkAide
received marketing
clearance from the
FDA!!(sep., 2005)
Implanted assembly of the Rancho Los Amigos
implanted peroneal stimulator
(Waters et al. 1975).
15/37
•
For Drop foot stimulation (DFS)
WalkAide
received marketing clearance from the
FDA!!(Sep., 2005)
MOV
MOV
16/37
•
Hybrid FES-Long-Leg Brace Ambulation system
Since 1970.
Use long-leg brace or body brace
This system give up one major goal of FES-ambulation : the
patient’s independence.
Hybrid systems use a body brace or long-leg brace, they are far
heavier and far more cumbersome than the 258gram Parastep.
Advantages:
1.Partial mechanical support
2.Parallel operation of the biological and mechanical system
3.Sequential operation of the biological and the mechanical
system
17/37
•
Implanted FES Ambulation System
Implant, showing the epineural electrodes.
(Holsheimer et al. 2000)
Aalborg University implanted DFS implant and external unit.
(Haugland et al. 2000)
We note that there are presently some 600 Parastep user, and it is used
both at home and at the workspace.
In contrast, there are presently only a few(on the order of a dozen) user of
even the most advanced percutaneous systems, whereas the fully implanted
system in not yet complete, to allow out-of-clinic ambulation
18/37
The Parastep System
19/37
The Parastep System
MOV
MOV
20/37
Motor Prosthesis (MP)
• Upper Extremity MPs
– Bionic Glove
augments grasp using surface electrodes for finger movements
– Handmaster System
Electrodes mounted in a brace, so easier to use – fingers again
– AutoMove
surface electrodes but control signals augment muscle movements
– Freehand System
Implanted system: Stimulator in chest – works with palmar grasp (glass) and lateral
grasp (pencil)
• Lower Extremity MPs
– Mostly for footdrop or standing for paraplegics (limited success with walking)
– Odstock, MicroFES & Footlifter
use surface electrodes for foot & knee flexion
– Parastep System
restores standing & walking (about 1,000 recipients) – six electrodes follow pattern of
stimulation
21/37
The Parastep System
The Parastep® I System
$13,000
The Parastep® is a microcomputer controlled
functional neuromuscular stimulation (FNS)
system that enables independent, unbraced
ambulation (i.e., standing and walking) by
people with a spinal cord injury.
The Parastep® is a non-invasive system and
consists of the following components:
- a microcomputer controlled neuromuscular
stimulation unit
- a battery activated power pack with recharger
- the Paratester™, a unit for pre-testing main
system operation and electrode cables
- surface applied skin electrodes
- power and electrode cables
- a control and stability walker with finger
activated control switches.
22/37
The Parastep System
Tutorial
MOV
23/37
The Parastep System
?
Cognitive feedback
Commands
?
CNS PROCESSOR
BRAIN
VISUAL
VESTIBULAR
SPINAL
NATURAL
SENSORS
UPPER LIMB SEGMENT
DYNAMICS/KINEMATICS
MUSCLES
Disturbances
Spinal Lesion
CONTROLLER
NATURAL
SENSORS
ARTIFICIAL
SENSORS
Desired Task
SPINAL CIRCUITS
MUSCLES
LOWER LIMB SEGMENT
DYNAMICS/KINEMATICS
Disturbances
24/37
The Parastep System
System’s Electric Charge and Charge Density parameter
• Parameters of stimulation signal and standard Constraints
ANSI(American National Standard Institute) A/s limit : 10mA/s
Pulse
120 ~ 150 us duration(width)
20 ~ 25 pps (pulse per second)
-> As low as possible while still allowing full contraction for safety.
Powered by 9.6 VDC battery
maximum current Io= 0.3A
Average current Iave = Io x T x f = 0.3 x 24 x 0.00015 = 1.08 mA
-> below the ANSI limit
25/37
The Parastep System
System’s Electric Charge and Charge Density parameter
• Parameters of stimulation signal and standard Constraints
ANSI(American National Standard Institute) ‘uC/pulse’ limit : 75uC/pulse
Q = Io x T = 0.3 A x 0.00015 s = 45uC
ANSI(American National Standard Institute) ‘uC/mm2’ limit : 10uC/mm2
<Current density>
Electrode dimension : S = 4000mm2
Iave/S = 0.00108/4000 = 0.25uC/mm2
26/37
The Parastep System
System Parameters and Design
•
Pulse Width and Pulse Repetition Rate (Frequency)
27/37
The Parastep System
System Parameters and Design -
Stimulation Site
Optional for T7 or higher spinal lesion
28/37
The Parastep System
Sequencing Control Menu for the Stimulation Signal
29/37
The Parastep System
Above- Lesion EMG-Controlled Menu Selection
MOV
30/37
Patient Admissibility,
Contraindications and Training
Patient Admissibility Criteria
31/37
Patient Admissibility Criteria (cont.)
32/37
Contraindication
Once admission criteria met, no contraindications are known.
None are known to have been reported in the literature.
(as long as to author)
33/37
Walking Performance and Medical and
Psychological Benefits Evaluation Result
Walking Performance Data
34/37
Regulatory Status
FDA – 1994
The first and still the only FES ambulation system to have received FDA
approval.
Center for medicare and Medicaid Services (CMS) – 2003
Medicare covers around 80% of equipment cost.
35/37
Conclusions
•
•
•
Discussed the Parastep system
The first and still the only, FDA-approved noninvasive FES system
For ambulation by complete or near complete thoracic-level paraplegic.
•
Completion of four months of daily training, ambulation distances for the
parstep system were reported to average 444m per walk.
•
Medical benefits have been documented in terms of
–
–
–
–
–
•
greatly increased blood flow to the lower extremities
Reduced spasticity
Reduced incidence of decubiti
Increased thigh circumference
Psychological benefits
However, even 10yr after FDA and medicare approval, there is great
ignorance in the paraplegic community about the availability of such
system and of its performance and benefits.
36/37
Conclusions
•
The Desire to stand upright independently and to
ambulate even short distances is the prime desire of
paraplegics!
•
Nether the Parastep nor any other FES approach can
be a substitute for spinal cord regeneration because
FES does not heal
•
It is an aid, just like eyeglasses or a hearing aid…
•
It is hoped that regeneration will become a reality for
SCI patients
•
In the meantime, a realistic aid does exist that is
already FDA approved and reimbursable.
•
It can always be and will be improved, but its
performance is usually pretty good!!
37/37
END

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