Rudi Kobetic

Implanted functional electrical stimulation system for mobility in paraplegia: a follow-up case report

A 16-channel functional electrical stimulation (FES) system has been implanted in a person with T10 paraplegia for over a year. The system consists of two eight-channel radio frequency controlled receiver-stimulators delivering stimuli through a network of 14 epimysial and two intramuscular electrodes. Using this system and a walker for support, the subject was able to stand up for 8 min and walk regularly for 20 m. The standing duration was limited by arm fatigue since upper extremities supported an average of 25% of body weight. This was due to suboptimal hip extension and some undesired recruitment of rectus femoris and sartorius with stimulation of quadriceps electrodes. The left quadriceps exhibited rapid fatigue that limited walking distance and duration. The metabolic energy requirements were well within the aerobic limits of the sedentary paraplegic population. At one-year follow-up evaluation all electrodes are functional except one intramuscular electrode. The implant caused no adverse physiological effects and the individual reported health benefits such as increased energy and overall fitness as a result of the FES system use. With further improvements in muscle response through innovative surgical techniques, the 16-channel implanted FES system can be a viable addition to exercise and mobility function in persons with paraplegia.

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. A novel variable coupling hip-reciprocating mechanism either acts as a standard reciprocating gait orthosis or allows each hip to independently lock or rotate freely. Rotary actuators at each hip are configured in a closed hydraulic circuit and regulated by a finite state postural controller based on real-time sensor information. The knee mechanism locks during stance to prevent collapse and unlocks during swing, while the ankle is constrained to move in the sagittal plane under FES-only control. The trunk is fixed in a rigid corset, and new ankle and trunk mechanisms are under development. Because the exoskeletal control mechanisms were built from off-the-shelf components, weight and cosmesis specifications for clinical use have not been met, although the power requirements are low enough to provide more than 4 hours of continuous operation with standard camcorder batteries.

Implanted functional neuromuscular stimulation systems for individuals with cervical spinal cord injuries: Clinical case reports

OBJECTIVE To determine the feasibility of providing the ability to stand and to facilitate the performance of standing transfers to individuals with cervical-level spinal cord injuries via functional neuromuscular stimulation (FNS). The applicability of implantable technology to this population was investigated, and the characteristics of the potential system users were explored. The effects of FNS on the effort and assistance required to stand and complete standing transfers were examined. SETTING Institutional rehabilitation practice. DESIGN Nonrandomized controlled trial. PATIENTS Twenty-four individuals with low cervical spinal cord injuries were evaluated for inclusion in a program of lower extremity FNS, four of whom received the intervention. INTERVENTION Chronically indwelling percutaneous intramuscular electrodes were used to exercise the hip, knee, and trunk extensors and develop activation patterns to produce standing function. These temporary systems were then replaced with silicone-enclosed helical wire electrodes suitable for eventual use with an eight-channel implantable receiver/stimulator. MAIN OUTCOME MEASURES Full sensory and motor evaluations were performed and physical contraindications to stimulation were catalogued. For active subjects, American Spinal Injury Association Total Motor Scores with and without FNS were recorded, along with quadriceps strength and ability to complete exercise, standing, controlled sitting, and standing transfer maneuvers. Performances of implanted electrodes were determined by the stability of recruitment properties, impedances or surface potentials, and serial radiographs. RESULTS Motor scores increased an average of nine points with stimulation over baseline volitional values. With FNS, all four volunteers were able to exercise, stand, and sit independently or with minimal assistance. Although they required varying degrees of assistance with the pivot phase of the transfer maneuver, all were able to raise and lower their body weight independently with stimulation and to use the system to facilitate standing transfers. One participant received the implantable receiver/stimulator, which remains operational at follow-up more than 3 years later. CONCLUSION FNS can provide the ability to exercise, stand, and transfer to individuals with tetraplegia, even in the presence of medical complications and upper extremity impairment. FNS facilitates standing transfers by eliminating the heavy lifting usually required by a caregiver, thus decreasing the effort and assistance necessary to gain access to places impossible to approach with conventional sliding transfers.

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. Electrodes were implanted bilaterally, recruiting iliopsoas, vastus intermedius and lateralis, tensor fasciae latae, tibialis anterior, and peroneus longus muscles. Twelve weeks of training followed limited activity post-surgery. Customized stimulation patterns addressed gait deficits via an external control unit. The system was well-tolerated and reliable. After the 12-week training, maximal walking distance increased (from 14 m to 309 m), maximal walking speed was 10 times greater (from 0.02 m/s to 0.20 m/s), and physiological cost index was 5 times less (from 44.4 beats/m to 8.6 beats/m). Voluntary locomotor function was unchanged. The implanted FES system was well-tolerated, reliable, and supplemented function, allowing the participant limited community ambulation. Physiological effort decreased and maximal walking distance increased dramatically over 12 weeks.

The Case Western Reserve University hybrid gait orthosis.

Abstract Six individuals with paraplegia and injury levels from C-1 through T-12 participated in a study to evaluate the functional capabilities of a hybrid gait orthotic system. Subjects learned to use a custom-built reciprocal gait orthosis without stimulation and with electrical stimulation activating between 4 and 16 muscles. Outcomes were scored with standard physical therapy measures including the Tinetti test, a timed get up and go, Borg rating of perceived exertion, and the Functional Index Measure (FIM). Subjects have successfully accomplished sit to stand, stand to sit, and walking maneuvers measured for time, speed, and distance. Metabolic consumption was measured for walking in the light work region of 5.1 to 6.5 metabolic equivalents (METs) 1 MET= 3.5 ml of 02/kg/min with hybrid gait orthosis. Perceived exertion as measured with the Borg scale indicated that use of the bracing system with functional electrical stimulation was “easier” than without stimulation. Subjects using a hybrid system were able to walk up to 350 m at average speeds of 0.25 m/s. Walking speeds for 30- and 50-meter distances reached 0.45 m/s. Additionally, walking distances with stimulation were 2 times greater than those of non-stimulated reciprocal gait. FIM scores indicated that system users would become slightly more independent in mobility. Results were used to determine the most useful brace modifications for the next generation of Case Western Reserve University hybrid gait orthoses to allow an expanded function that will include stair climbing and side stepping.

Functional Electrical Stimulation and Spinal Cord Injury

Spinal cord injuries (SCI) can disrupt communications between the brain and the body, resulting in loss of control over otherwise intact neuromuscular systems. Functional electrical stimulation (FES) of the central and peripheral nervous system can use these intact neuromuscular systems to provide therapeutic exercise options to allow functional restoration and to manage medical complications following SCI. The use of FES for the restoration of muscular and organ functions may significantly decrease the morbidity and mortality following SCI. Many FES devices are commercially available and should be considered as part of the lifelong rehabilitation care plan for all eligible persons with SCI.

Gait Evaluation of a Novel Hip Constraint Orthosis With Implication for Walking in Paraplegia

The aim of this study was to determine the effects of a newly developed reciprocal gait orthosis (RGO) with a variable constraint hip mechanism (VCHM) on the kinematics and kinetics of normal gait. The VCHM was compared with the isocentric reciprocating gait orthosis (IRGO) for walking after paraplegia. Both the VCHM and the IRGO were evaluated with able-bodied volunteers with the hip reciprocating mechanisms coupled and uncoupled. The VCHM was further evaluated with context-dependent coupling based on a finite-state control algorithm utilizing information from brace-mounted sensors. Walking performance for each brace condition was also compared to normal walking without an orthosis. Without the hip controller, the VCHM affected the kinematics of the hip joint in a similar manner as the IRGO, regardless of whether the hip reciprocator was coupled or uncoupled. With the controller active, hip kinematics with the VCHM were closer to normal gait than with the IRGO or any other condition tested (Intraclass correlation coefficient, ICC=0.96). The effects of the braces on the knee and ankle angles were not as prominent as their effects on the hip angles. In terms of kinetics, the VCHM with controller active allowed the generation of joint moments that were closer to normal (ICC=0.80) than the IRGO with hips coupled (ICC= 0.68). There was no statistically significant difference between the various conditions tested in terms of step-length ( p <; 0.01) and no statistically significant difference in the preferred walking speed between the IRGO and normal walking, whether or not the hips were coupled. However, there was a 25% reduction in walking speed with the VCHM when compared to normal, and the relative magnitudes of the EMG activity of three muscles (tibialis anterior, quadriceps, and hamstrings) were also higher with the VCHM than with either the IRGO or normal gait, likely due to the additional weight of the mechanism. Overall, the VCHM with controller active provided smooth control of the hip joints via context-dependent coupling and allowed for increased hip flexion relative to the IRGO. The results suggest that the VCHM with controlled joint coupling may eventually be a valuable component of a hybrid system combining functional electrical stimulation (FES) with orthotics.

Design of a Variable Constraint Hip Mechanism for a Hybrid Neuroprosthesis to Restore Gait After Spinal Cord Injury

A variable constraint hip mechanism (VCHM) has been developed for a hybrid neuroprosthesis system (HNP) to provide postural stability and uninhibited sagittal hip rotation throughout the gait of individuals with paraplegia. This paper describes the design concepts used in the development of the VCHM. The VCHM utilizes a hydraulic system to reciprocally couple the hips or individually lock and/or free a hip to rotate in one or both sagittal directions. Bench testing results show the feasibility of utilizing a portable hydraulic system in controlling hip joint kinematics. The passive resistive torques of the VCHM against user hip rotation at hip angular velocities typical of gait does not exceed 10% of the achievable hip torque generated by functional neuromuscular stimulation of paralyzed muscle. With the state of the VCHM configured to reciprocally couple the hips, the normalized mechanical efficiency of the VCHM was determined to be 0.7. Since each hip will be independently driven by the FNS of muscle, high torque transfer efficiency between the hips is not essential for successful operation of the VCHM. Future work will focus on the development of a sensor-based feedback controller to modulate the hip constraints of the VCHM and validation of the VCHM as part of a HNP for paraplegic individuals implanted with FNS systems.

Functional electrical stimulation for walking in paraplegia: 17-year follow-up of 2 cases.

Abstract Objective: To assess the safety and effectiveness of long-term use of functional electrical stimulation (FES) for exercise, standing, and walking in individuals with paraplegia, using percutaneous intramuscular wire electrodes. Design: Case study with more than 1 7 years of follow-up. Setting: Institutional rehabilitation practice. Study Participants: Two long-term (17 years) volunteer participants with paraplegia who were able to stand and walk using FES. Intervention: Chronically indwelling percutaneous intramuscular wire electrodes connected to a portable microprocessor-controlled stimulator were used to exercise muscles while controlling trunk, hips, knees, and ankles and develop activation patterns to produce standing and walking. Main Outcome Measures: Clinical complications, electrode performance and survival probability, and functional performance. Results: The most noted clinical complications included localized inflammation at the electrode site and superficial infection that responded well to topical and oral antibiotic treatment. The change from coil-wire electrodes, with a survival of 35% after 1 year, to double-helix electrodes improved electrode survival to 80% at 1 year and 48% at 5 years. Maintenance of the multichannel percutaneous FES walking system required replacement of an average of 2 electrodes every 6 months. Participants were able to use their system for independent exercise and standing and for walking with standby assistance. Conclusion: Although the FES system was devised as a temporary means of achieving functional activation until permanent means could be achieved, it was found to be effective and relatively safe for more than 17 years. Two long-time users of the system had no adverse effects to their skeletal system. The most common problems were daily care of electrodes at exit sites, frequent irritation of the skin around electrodes, and replacement of failed electrodes. The percutaneous system has the potential for short-term rehabilitation in individuals with incomplete paraplegia or stroke. Spinal Cord Med. 2003;26:86-91

Ambulation After Incomplete Spinal Cord Injury With EMG-Triggered Functional Electrical Stimulation

Individuals with incomplete spinal cord injury (iSCI) retain some control of the partially paralyzed muscles, necessitating careful integration of functional electrical stimulation (FES) with intact motor function. In this communication, the volitional surface electromyogram (sEMG) from partially paralyzed muscle was used to detect the intent to step in an iSCI volunteer. The classifier was able to trigger the FES-assisted swing phase with a false positive rate less than 1% and true positive rate of 82% for left foot-off (FO) and 83% for right FO over 110 steps taken during three testing sessions spread over a week.