Implanted Pulse Generators in Lower Extremity Neuroprostheses: A 25-Year Review.

Objectives: Neuroprosthetic devices can improve quality of life by providing an alternative option for motor function lost after spinal cord injury, stroke, and other central nervous system disorders. The objective of this study is to analyze the outcomes of implanted pulse generators that our research group installed in volunteers with paralysis to assist with lower extremity function over a 25-year period, specifically, to determine survival rates and common modes of malfunction, reasons for removal or revision, and precipitating factors or external events that may have adversely influenced device performance.

Materials And Methods: Our implantable receiver-stimulator (IRS-8) and implantable stimulator-telemeter (IST-12 and IST-16) device histories were retrospectively reviewed through surgical notes, regulatory documentation, and manufacturing records from 1996 to 2021.

Walking after incomplete spinal cord injury with an implanted neuromuscular electrical stimulation system and a hinged knee replacement: a single-subject study.

Study Design: Single-subject repeated measures study.

Objectives: Neuromuscular electrical stimulation (NMES) can enhance walking for people with partial paralysis from incomplete spinal cord injury (iSCI). This single-subject study documents an individual's experience who both received an experimental implanted NMES system and underwent clinical bilateral hinged total knee arthroplasty (TKA).

Chronic nerve health following implantation of femoral nerve cuff electrodes.

Background: Peripheral nerve stimulation with implanted nerve cuff electrodes can restore standing, stepping and other functions to individuals with spinal cord injury (SCI). We performed the first study to evaluate the clinical electrodiagnostic changes due to electrode implantation acutely, chronic presence on the nerve peri- and post-operatively, and long-term delivery of electrical stimulation.

Methods: A man with bilateral lower extremity paralysis secondary to cervical SCI sustained 5 years prior to enrollment received an implanted standing neuroprosthesis including composite flat interface nerve electrodes (C-FINEs) electrodes implanted around the proximal femoral nerves near the inguinal ligaments.

Implanted High Density Cuff Electrodes Functionally Activate Human Tibial and Peroneal Motor Units Without Chronic Detriment to Peripheral Nerve Health.

Objective: Peripheral nerve stimulation via multi-contact nerve cuff electrodes (NCEs) has proved effective in restoring function to individuals with lower-extremity paralysis. This study investigates clinical measures of nerve health over one year post-implantation of a composite flat-interface nerve electrode (C-FINE) on the tibial and peroneal nerves above the knee in a human volunteer. This represents the first deployment of a novel NCE on new neural targets in a uniquely challenging location prone to prolonged externally applied forces, making acute and chronic postoperative observation critical.

Oxygen Consumption While Walking With Multijoint Neuromuscular Electrical Stimulation After Stroke.

This case study evaluated the effect of implanted multijoint neuromuscular electrical stimulation gait assistance on oxygen consumption relative to walking without neuromuscular electrical stimulation after stroke. The participant walked slowly with an asymmetric gait pattern after stroke. He completed repeated 6-min walk tests at a self-selected walking speed with and without hip, knee, and ankle stimulation assistance.

Intraoperative Responses May Predict Chronic Performance of Composite Flat Interface Nerve Electrodes on Human Femoral Nerves.

Peripheral nerve cuff electrodes (NCEs) in motor system neuroprostheses can generate strong muscle contractions and enhance surgical efficiency by accessing multiple muscles from a single proximal location. Predicting chronic performance of high contact density NCEs based on intraoperative observations would facilitate implantation at locations that maximize selective recruitment, immediate connection of optimal contacts to implanted pulse generators (IPGs) with limited output channels, and initiation of postoperative rehabilitation as soon as possible after surgery. However, the stability of NCE intraoperative recruitment to predict chronic performance has not been documented.

A translational framework for peripheral nerve stimulating electrodes: Reviewing the journey from concept to clinic.

The purpose of this review article is to describe the underlying methodology for successfully translating novel interfaces for electrical modulation of the peripheral nervous system (PNS) from basic design concepts to clinical applications and chronic human use. Despite advances in technologies to communicate directly with the nervous system, the pathway to clinical translation for most neural interfaces is not clear. FDA guidelines provide information on necessary evidence which should be generated and submitted to allow the agency evaluate safety and efficacy of a new medical device.

High-density peripheral nerve cuffs restore natural sensation to individuals with lower-limb amputations.

Objective: Sensory input in lower-limb amputees is critically important to maintaining balance, preventing falls, negotiating uneven terrain, responding to unexpected perturbations, and developing the confidence required for societal participation and public interactions in unfamiliar environments. Despite noteworthy advances in robotic prostheses for lower-limb amputees, such as microprocessor knees and powered ankles, natural somatosensory feedback from the lost limb has not yet been incorporated in current prosthetic technologies.

Approach: In this work, we report eliciting somatic sensation with neural stimulation delivered by chronically-implanted, non-penetrating nerve cuff electrodes in two transtibial amputees.

Long-Term Performance and User Satisfaction With Implanted Neuroprostheses for Upright Mobility After Paraplegia: 2- to 14-Year Follow-Up.

Objective: To quantify the long-term (>2y) effects of lower extremity (LE) neuroprostheses (NPs) for standing, transfers, stepping, and seated stability after spinal cord injury.

Design: Single-subject design case series with participants acting as their own concurrent controls, including retrospective data review.

Setting: Hospital-based clinical biomechanics laboratory with experienced (>20y in the field) research biomedical engineers, a physical therapist, and medical monitoring review.

"Long-term stability of stimulating spiral nerve cuff electrodes on human peripheral nerves".

Background: Electrical stimulation of the peripheral nerves has been shown to be effective in restoring sensory and motor functions in the lower and upper extremities. This neural stimulation can be applied via non-penetrating spiral nerve cuff electrodes, though minimal information has been published regarding their long-term performance for multiple years after implantation.

Methods: Since 2005, 14 human volunteers with cervical or thoracic spinal cord injuries, or upper limb amputation, were chronically implanted with a total of 50 spiral nerve cuff electrodes on 10 different nerves (mean time post-implant 6.

A muscle-driven approach to restore stepping with an exoskeleton for individuals with paraplegia.

Background: Functional neuromuscular stimulation, lower limb orthosis, powered lower limb exoskeleton, and hybrid neuroprosthesis (HNP) technologies can restore stepping in individuals with paraplegia due to spinal cord injury (SCI). However, a self-contained muscle-driven controllable exoskeleton approach based on an implanted neural stimulator to restore walking has not been previously demonstrated, which could potentially result in system use outside the laboratory and viable for long term use or clinical testing. In this work, we designed and evaluated an untethered muscle-driven controllable exoskeleton to restore stepping in three individuals with paralysis from SCI.

Accelerometer-based step initiation control for gait-assist neuroprostheses.

Electrical activation of paralyzed musculature can generate or augment joint movements required for walking after central nervous system trauma. Proper timing of stimulation relative to residual volitional control is critical to usefully affecting ambulation. This study evaluates three-dimensional accelerometers and customized algorithms to detect the intent to step from voluntary movements to trigger stimulation during walking in individuals with significantly different etiologies, mobility limitations, manual dexterities, and walking aids.

Impact of an implanted neuroprosthesis on community ambulation in incomplete SCI.

Objective: Test the effect of a multi-joint control with implanted electrical stimulation on walking after spinal cord injury (SCI).

Design: Single subject research design with repeated measures.

Setting: Hospital-based biomechanics laboratory and user assessment of community use.

Feasibility of Restoring Walking in Multiple Sclerosis with Multichannel Implanted Electrical Stimulation.

A patient with multiple sclerosis-related gait dysfunction was followed over the course of his disease. Despite aggressive treatment, he developed significant weakness in ankle dorsiflexors and hip and knee flexors and was no longer capable of consistently taking a step on his own. With electrical stimulation of hip and knee flexors and ankle dorsiflexors using implanted electrodes, he was able to consistently walk short distances as far as 30 m, thus significantly improving his Expanded Disability Status Scale score.

Improving Walking with an Implanted Neuroprosthesis for Hip, Knee, and Ankle Control After Stroke.

Objective: The objective of this work was to quantify the effects of a fully implanted pulse generator to activate or augment actions of hip, knee, and ankle muscles after stroke.

Design: The subject was a 64-year-old man with left hemiparesis resulting from hemorrhagic stroke 21 months before participation. He received an 8-channel implanted pulse generator and intramuscular stimulating electrodes targeting unilateral hip, knee, and ankle muscles on the paretic side.

Forward stair descent with hybrid neuroprosthesis after paralysis: Single case study demonstrating feasibility.

The ability to negotiate stairs is important for community access and independent mobility but requires more effort and strength than level walking. For this reason, previous attempts to utilize functional neuromuscular stimulation (FNS) to restore stair navigation after spinal cord injury (SCI) have had limited success and are not readily generalizable. Stair descent is particularly challenging because it requires energy absorption via eccentric muscle contractions, a task not easily accomplished with FNS.

A preliminary comparison of myoelectric and cyclic control of an implanted neuroprosthesis to modulate gait speed in incomplete SCI.

Objective: Explore whether electromyography (EMG) control of electrical stimulation for walking after incomplete spinal cord injury (SCI) can affect ability to modulate speed and alter gait spatial-temporal parameters compared to cyclic repetition of pre-programmed stimulation.

Design: Single case study with subject acting as own concurrent control. Setting Hospital-based biomechanics laboratory.

Sensor-based hip control with hybrid neuroprosthesis for walking in paraplegia.

The objectives of this study were to test whether a hybrid neuroprosthesis (HNP) with an exoskeletal variable-constraint hip mechanism (VCHM) combined with a functional neuromuscular stimulation (FNS) controller can maintain upright posture with less upper-limb support and improve gait speed as compared with walking with either an isocentric reciprocating gait orthosis (IRGO) or FNS only. The results show that walking with the HNP significantly reduced forward lean in FNS-only walking and the maximum upper-limb forces by 42% and 19% as compared with the IRGO and FNS-only gait, respectively. Walking speed increased significantly with VCHM as compared with 1:1 reciprocal coupling and by 15% when using the sensor-based FNS controller as compared with HNP with fixed baseline stimulation without the controller active.

Stance control knee mechanism for lower-limb support in hybrid neuroprosthesis.

A hydraulic stance control knee mechanism (SCKM) was developed to fully support the knee against flexion during stance and allow uninhibited motion during swing for individuals with paraplegia using functional neuromuscular stimulation (FNS) for gait assistance. The SCKM was optimized for maximum locking torque for body-weight support and minimum resistance when allowing for free knee motion. Ipsilateral and contralateral position and force feedback were used to control the SCKM.

Neurotherapeutic and neuroprosthetic effects of implanted functional electrical stimulation for ambulation after incomplete spinal cord injury.

The purpose of this single-subject study was to determine the neurotherapeutic and neuroprosthetic effects of an implanted functional electrical stimulation (FES) system designed to facilitate walking in an individual with a longstanding motor and sensory incomplete spinal cord injury. An implanted pulse generator and eight intramuscular stimulating electrodes were installed unilaterally, activating weak or paralyzed hip flexors, hip and knee extensors, and ankle dorsiflexors during 36 sessions of gait training with FES. The neurotherapeutic effects were assessed by a comparison of pre- and posttraining volitional walking.

Fascicular anatomy of human femoral nerve: implications for neural prostheses using nerve cuff electrodes.

Clinical interventions to restore standing or stepping by using nerve cuff stimulation require a detailed knowledge of femoral nerve neuroanatomy. We harvested eight femoral nerves with all distal branches and characterized the branching patterns and diameters. The fascicular representation of each distal nerve was identified and traced proximally to create fascicle maps of the compound femoral nerve in four cadaver specimens.

Intraoperative demonstration of selective stimulation of the common human femoral nerve with a FINE.

We have tested the hypothesis that the Flat Interface Nerve Electrode (FINE) can selectively stimulate each muscle innervated by the common femoral nerve of the human, near the inguinal ligament in a series of intraoperative trials. During routine vascular surgeries, an 8-contact FINE was placed around the common femoral nerve between the inguinal ligament and the first branching point. The efficacy of the FINE to selectively recruit muscles innervated by the femoral nerve was determined from electromyograms (EMGs) recorded in response to electrical stimulation.

Development of hybrid orthosis for standing, walking, and stair climbing after spinal cord injury.

This study explores the feasibility of a hybrid system of exoskeletal bracing and multichannel functional electrical stimulation (FES) to facilitate standing, walking, and stair climbing after spinal cord injury (SCI). The orthotic components consist of electromechanical joints that lock and unlock automatically to provide upright stability and free movement powered by FES. Preliminary results from a prototype device on nondisabled and SCI volunteers are presented.

"Pseudostring sign" on carotid computed tomographic angiography: collateralization by vasa vasorum.

We present 3 cases of unilateral internal carotid artery (ICA) occlusions with prominent single collateralizing vessel of vasa vasorum on computed tomographic angiography. The features on axial source and 3-dimensional images of computed tomographic angiography include "pseudostring sign," serpigenous course of the vasa vasorum, eccentric dot appearance in the wall of chronically thrombosed ICA, and termination in the neck or reconstituting into the ICA at or below the skull base.

Walking after incomplete spinal cord injury using an implanted FES system: a case report.

Implanted functional electrical stimulation (FES) systems for walking are experimentally available to individuals with incomplete spinal cord injury (SCI); however, data on short-term therapeutic and functional outcomes are limited. The goal of this study was to quantify therapeutic and functional effects of an implanted FES system for walking after incomplete cervical SCI. After robotic-assisted treadmill training and overground gait training maximized his voluntary function, an individual with incomplete SCI (American Spinal Injury Association grade C, cervical level 6-7) who could stand volitionally but not step was surgically implanted with an 8-channel receiver stimulator and intramuscular electrodes.