20110503LHJ contents 17 Development of a Multifunctional 22Channel Functional E lectrical S timulator for Paraplegia 171 introduction 175 conclusion 174 Praxis FES24A system ID: 561487
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Slide1
17. Development of a Multifunctional 22-Channel Functional Electrical Stimulator for Paraplegia
2011.05.03.LHJSlide2
contents
17. Development of a Multifunctional
22-Channel Functional
E
lectrical
S
timulator for Paraplegia
17.1 introduction
17.5 conclusion
17.4 Praxis FES-24A system
17.2 historical aspect
17.3 neural engineering clinicSlide3
17.1 introduction
the authors’ aim
to develop a generic FES implant for the restoration of
functions
in spinal cord injured (SCI) paraplegic individuals
to match to individual’s requirementsupright functional mobility, pressure relief and lower extremity exercise, bladder and bowel controlbladder control: less invasive surgical proceduresto offer more functions and less surgery to patients with a cost-benefit ratiocf) neural implants have been developed to restore only specific functions-> “multifunctional”Slide4
the idea (during 1983, Davis)the possibilities of modifying and using the
22-channel cochlear implant technology
as the basis for an implantable FES system for the restoration of multiple functions in SCI
paraplegics
history
since 1984,3 FES implant models have evolved from Cochlear’s technology and its subsidiary: Neopraxis Pty. Ltd. in 1991,the initial Nucleus FES-22 Stimulator was implanted after animal and human studies with FDA approval (IDE# G87014
)Institutional Review Board (IRB) approval in a 21-year-old paraplegic subject17.1 introductionSlide5
17.2 historical aspect
in 1984,
the initial animal studies at the
Togus
VA Medical Center
(Augusta, Maine) a modified cochlear implant maximum pulse output of 4.3 mA and 0.4-ms pulse width, to be suitable for FES use in humans. an initial decision epineurally placed electrodes (2.5 mm diameter platinum disks) the lower stimulation currents
less movement of the electrodesSlide6
17.2 historical aspect
with
the approval
of
IRB and volunteer patients
undergoing lower extremity amputationstimulation studies0.2 ms pulse duration with 20 pps frequency, with a portable, battery-operated, calibrated constant-current unit (Cordis Corp., Miami, Florida, Model 910 A). the pulse amplitudes for producing maximal stimulation and contraction in the largest of the nerves (medial sciatic) 0.6 to 2.5 mA: within
the range of the Cochlear receiver-stimulating unitSlide7
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
FES-22 stimulator
(first device)
to only provide its recipient with enhanced mobility
functionsRoger Avery (Custom Med Laboratories, Durham, New Hampshire) (during 1985) design and manufacture for the implantable leads and electrodesfor higher output currentsa new transmitter coil capable of delivering the higher power each
of 22 output channels individually availablea circular epoxy housing with 22 sockets around the perimeter with the diameter of the housing determined by the diameter of the
coilSlide8
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
Nucleus
FES-22 system
implanted
in
subject A (21-year-old male paraplegic subject) (during Nov., Dec. 1991)3 separate surgical procedures (each 2 weeks apart)first procedure receiver/stimulator was placed subcutaneously(피하) at the lower right anterior intercostal
(늑간의) margin 11 connecting leads subcutaneously tunneled to the right and 11 to the left hip areas 2.5-mm diameter platinum disk electrodesepineurally
on the individual branches of the right and left femoral nerves by
suturing the silicone elastomer ring around each electrode to the connective tissues on each side of the nerve branchesSlide9
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
Nucleus FES-22 system
3 separate surgical procedures (each 2 weeks apart)
in the
second
and third procedures, electrodes were attached over gluteal(둔근의), posterior tibial(
경골의), peroneal(종아리뼈의), and sciatic nerves(좌골
(궁둥) 신경) bilaterally
a total of 22 electrodes were implanted epineurally
one electrode placed subcutaneously in a Teflon bag in each of the femoral triangles, as a spare leadSlide10
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
Nucleus FES-22 system
first testing (Jan. 1992)
threshold and maximal muscle contractions as tested in 22 channels
second testing session (Feb. 1992)
implanted system did not function properlyowing to a suspected electrostatic damage in the implant resulting in the loss of 7 channels hardware and software changes the remaining 15 channels third testing (in Dec. 1992)15 channels were retestedchange of electrode locationsSlide11
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
Nucleus FES-22 system
subject A exercised his lower extremity muscles at home
using a PC computer to control the implanted stimulator
a battery-operated external Portable Conditioning System (19×11×6 cm) (Jan. 1997)
exercise protocolsstimulates the right and left knee extensors(신근) and ankle plantar(발바닥)/dorsi flexors
(굴근) alternately (4 s ON/4 s OFF), for a total of 20 minbilateral knee extension torque of 45 to 55 Nm at 30° and 65 Nm at 60° of knee flexionat least three days a weekSlide12
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
laboratory PC-based
FES-22 system
10-ms duty-cycle state machine for open- and closed-loop control for use in prolonged standing mode
controller
is divided into three phasesopen-loop sit-to-stand closed-loop standclosed-loop stand-to-sitinitiation of standing up and sitting downuse a remote switch on a hand glovesensors used for closed-loop control electrogoniometers across both kneesaccelerometers attached to the back at T6Slide13
17.3 neural engineering clinic : two male subjects with necleus FES-22 stimulating system
controlled
Nucleus FES-22
stimulation to the motor nerves
uninterrupted standing for over 60 min
bilateral knee-angle goniometer sensors with Andrews’ stabilizing Anterior Floor Reaction Orthosis (AFRO)stimulator “ON” when a 10° buckle between 3 and 8% of the standing time automatic switch “OFF” (on recovery) knee flexion less than 5°.
ankle-foot braceSlide14
17.4 Praxis FES-24A system
Neopraxis
Pty. Ltd. (in 1998)
a subsidiary company of Cochlear Ltd.
produce the
Praxis FES-22A System multiple functions — bladder and bowel control, enhanced mobility and seated pressure relief — in an effort to provide recipients with a cost-effective deviceSlide15
17.4 Praxis FES-24A system
1
17.4
4.3. Praxis FES-24-B
system
4.1. bladder control
4.5. complications on follow-up
of the first two implanted
at the NEC site, subject(A&B)
4.4. experience at
Shriners
hospital for children
4.2. Praxis system clinical results
-4.2.1. bladder results
-4.4.1. upright mobility
-4.4.2. bladder
and bowel
-4.4.3. electrode stability
-4.4.4. sensorsSlide16
17.4 Praxis FES-24A system17.4.1 bladder control
Finetech–Brindley
Stimulator, and now
Vocare
(NeuroControl Corp., Cleveland, Ohio)traditional bladder stimulatorstimulate the sacral anterior rootstwo primary drawbacksposterior sacral rhizotomies (척추신경근절단수술), via a laminectomy(척추후궁절제술)
an areflexive bladder(무반사성 방광) with increased capacitya sacral laminectomy is done to access the anterior sacral roots for fitting cuff-type electrodes
eliminates reflex erection in male recipients -> “Praxis system”Slide17
17.4 Praxis FES-24A system17.4.1 bladder control
Praxis FES-24A
stimulator
implanted in subject B
(35-year-old male paraplegic subject)
18 channels for stimulating individual nerves or branches for muscle contractions and limb movements10 thin flexible platinum cuffs (Flexi-Cuff)electrodes implanted for epineural stimulationsized, cut, and sutured closed with at least twice the diameter of encircled nerve8 electrodes 3-mm-diameter platinum buttons on the epineurium(신경외막)sutured to the adjacent connective tissue on each side of the nerveSlide18
17.4 Praxis FES-24A system 17.4.1 bladder control
Praxis FES-24A
stimulator
3 channels
for bladder control (bowel control and erection)
bilateral sacral root stimulation (S2-4) LPR electrodes (10-mm long, solid platinum tubing of 1.0-mm diameter) inserted in external sacral foramina(천골공)1 channel an epidural spinal cord stimulating electrode (Pisces Quad: Medtronic Inc., Minneapolis, Minnesota) for conus medullaris
(척수원뿔) modulation of spastic bladder and bowel reflexesSlide19
17.4 Praxis FES-24A system17.4.2 Praxis system clinical results
prior to
implantation, subject B stands
without knee bracing
with Andrews’ Anterior Floor Reaction Orthosis + closed-loop skin surface FES applied directly over the femoral nervesclosed-loop control of stimulation stand uninterrupted for 30 min, and up to 70 min with training, “C” posture and stood with the stimulation “OFF” for more than 50% of the standing timeSlide20
17.4 Praxis FES-24A system17.4.2 Praxis system clinical results
after
implantation of
Praxis FES 24-A system
(in 1998)
standing with doing a variety of one-handed tasks while in the “C” posture with closed-loop activation to the lower extremity muscles balance maintained by the other upper extremitydaily stimulation decreased his muscle spasms Slide21
17.4 Praxis FES-24A system17.4.2.1 bladder results
urodynamic
testing
in the
Urodynamic
Testing Laboratory, subject 2sacral roots (S3 and 4) bilaterally stimulated intermittentlyon Sept. 1998, bladder contractions with pressures of between 45 and 50 cm of wateron Dec. 1998, three sustained bladder contractions5 s on / 5 s off, 20 Hz, 8 bursts pressures of 40 to 55 cm water and urinationon April 1999, two bladder reflex activations5 s on / 5 s off, 20 Hz, 8 to 14 bursts pressures of 50 to 70 cm of water Slide22
17.4 Praxis FES-24A system17.4.3 Praxis FES-24-B system
FES-24B System
eliminates internal wire breakage possibility
consists of
body-worn controller “Navigator”
skin surface stimulator “ExoStim” “sensor packs” incorporating accelerometers and a gyroscope a new implant receiver/stimulator
to be capable of executing a wide variety of software control strategies
to mimic an implant and to provide simple exercise functions prior to implantation
to provide feedback information to control strategies
to be based on the latest cochlear implant control integrated circuit (IC), the “CIC3”
a range of implantable electrode leads suitable for the system’s multiple functionsSlide23
17.4 Praxis FES-24A system17.4.3 Praxis FES-24-B system
Praxis FES-24B
s
ystem
maximum current output of 8 mA
in a constant-current modestimulationbiphasic (negative and positive phases) current pulsespulse widths: from 25 to 500μsa per-channel pulse frequency of 0 to 400 Hz on each of the twenty-two channels stimulatorreal-time data telemetry functionsthe ability to measure the impedance of the current path through each electrodethe ability to transmit voltage measurements from each electrodeSlide24
17.4 Praxis FES-24A system17.4.4 experience at shriners hospital for children
3 males with paraplegia, ages 18, 21, and 21 years
Praxis FES-24B System
between Jan. 2002 and May 2003
18 epineural electrodes implanted for upright mobility in all subjectsthree pairs of bifurcated linear pararadicular electrodesextradurally on the bilateral S2, S3, and S4 mixed nerve roots for bladder and bowel function in the first two subjectsSlide25
17.4 Praxis FES-24A system17.4.4.1 upright mobility
goals
transitions between sitting and standing, swing-through and/or reciprocal gait with a walker or crutches, and prolonged standing
advanced activities
ascending and descending stairs and the achievement of subject-specific goalsSlide26
17.4 Praxis FES-24A system17.4.4.1 upright mobility
tested mobility activities
subject 1 & 3
swing-through gait pattern
a walker with wheels
subject 2 reciprocal pattern for ascending stairs forearm crutchesNone of the subjects required physical assistancebilateral ankle–foot orthoses were worn for all upright mobility activitiesSlide27
17.4 Praxis FES-24A system17.4.4.2 bladder and bowel
to improve bowel evacuation
using two different stimulation paradigms
low frequency electrical stimulation (20 Hz, 350
μ
s, 8 mA) a combination of low-frequency and high-frequency stimulation (500 Hz, 350 μs, 8 mA). daily use of electrical stimulation reduction in the time to complete defecation by 40% with the first stimulation strategy and by 60% with the second strategydespite numerous attempts with varying stimulation parameters to the sacral nerve roots, neither subject could obtain detrusor(배뇨근) pressures sufficient to provide voiding with stimulation
both subjects continued to catheterize for bladder emptyingSlide28
17.4 Praxis FES-24A system17.4.4.3 electrode stability
3 of 52 electrodes
placed for lower extremity stimulation
changes in the responses of the muscles
one electrode
due to a disconnection at the connector site between the implant and the electrode lead repaired and continued to function without further problems2 electrodes (biceps femoris and tibial nerve) not replaced, as they did not impact function for the subjects involvedSlide29
17.4 Praxis FES-24A system17.4.4.4 sensors
closed-loop standing using
sensor packs
with subject 1
incorporating accelerometers and a gyroscope
attached externally on the thigh and the calf to detect the position of the knee while standingstimulation would decrease until a change in the knee joint angle was detectedat which time stimulation would again increase to prevent a knee buckleSlide30
17.4 Praxis FES-24A system17.4.4.4 sensors
the use of the sensors for closed-loop feedback to the right quadriceps muscles during standing
stand with less stimulation
stand for a longer period of time before the muscle fatigued
the algorithm for increasing and decreasing stimulation did not create any balance disturbancesSlide31
17.4 Praxis FES-24A system17.4.5 complications on follow-up of the first two implanted at the NEC site, subject (A & B)
subject A
accidentally cut his left foot (in 2002)
left lower extremity was swollen with an infection
swelling resolved tissues around the
Nucleus FES-22 system were swollen and inflamedafter treated with intravenous antibiotics, the implanted system was explantedsubject Bintermittent pain in the T7-8 vertebra (in 2001)in 2003, implanting the Praxis FES-24B stimulatorNeopraxis Company had been closedwithout further support, leads and electrodes removedSlide32
17.4 Praxis FES-24A system17.4.5 complications on follow-up of the first two implanted at the NEC site, subject (A & B)
subject 2
at the SHC site, during the training period
sustained a stress fracture
(
피로골절) of the left proximal first metatarsal(중족골)immobilized for 6 weeks in a soft bootsubject 1at the end June of 2002 sustained an abrasion near his ankleantibiotics were startedat the beginning of Aug. 2002, high fevers and inflammation around one of his surgical incisionsantibiotic treatment appeared to temporarily suppressthe majority of the system has been removedSlide33
17.5 conclusion
in the developing field of FES and implantable neural prosthetic devices
a need for reliable and safe, multichannel implantable stimulating systems
the stimulating systems’ functions
design for individual’s requirements
an energy-efficient mobility aid for prolonged usetwo Praxis FES Systems a new rehabilitation aid for restoration of function in spinal cord injury paraplegia the more channels available, the more nerves that can be activated and the more modes of functionality that can be restoredSlide34
Thank you for your attention
2011.05.03.LHJ