M W Keith

MetroHealth Medical Center, Cleveland, Ohio, United States

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Publications (71)86.29 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective To develop and apply an implanted neuroprosthesis to restore arm and hand function to individuals with high level tetraplegia Design Case study. Setting Clinical research laboratory. Participants Two individuals with spinal cord injuries at or above the C4 motor level. Interventions The individuals were each implanted with two stimulators (24 stimulation channels and 4 myoelectric recording channels total). Stimulating electrodes were placed in the shoulder and arm, including the first chronic application of spiral nerve cuff electrodes to activate a human limb. Myoelectric recording electrodes were placed in the head and neck areas. Main Outcome Measures The successful installation and operation of the neuroprosthesis, along with the electrode performance, range of motion, grasp strength, joint moments, and performance in activities of daily living. Results The neuroprosthesis system was successfully implanted in both individuals. Spiral nerve cuff electrodes were placed around upper extremity nerves and activated the intended muscles. In both individuals, the neuroprosthesis has functioned properly for at least 2.5 years post-implant. Hand, wrist, forearm, elbow and shoulder movements were achieved. A mobile arm support was needed to support the mass of the arm during functional activities. One individual was able to perform several activities of daily living with some limitations due to spasticity. The second individual was able to partially complete two activities of daily living. Conclusions Functional electrical stimulation is a feasible intervention for restoring arm and hand functions to individuals with high tetraplegia. Forces and movements were generated at the hand, wrist, elbow and shoulder that allowed the performance of activities of daily living, with some limitations requiring the use of a mobile arm support to assist the stimulated shoulder forces.
    Archives of physical medicine and rehabilitation 01/2014; · 2.18 Impact Factor
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    ABSTRACT: Multi-contact cuff electrodes were implanted in the median, ulnar, and radial nerves of an upper-limb amputee. 19 of 20 contacts produced selective, sensory response in the phantom limb from nerve stimulation. The neural interface has been stable for the duration of this ongoing chronic study, 12 months post-implant, with consistent threshold and impedance measures.
    Neural Engineering (NER), 2013 6th International IEEE/EMBS Conference on; 01/2013
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    ABSTRACT: Loss of arm and hand function is common after stroke. An implantable, 12-channel, electromyogram (EMG)-controlled functional electrical stimulation neuroprosthesis (NP) may be a viable assistive device for upper-limb hemiplegia. In this study, a research participant 4.8 yr poststroke underwent presurgical screening, surgical installation of the NP, training, and assessment of upper-limb impairment, activity limitation, and satisfaction over a 2.3 yr period. The NP increased active range of finger extension from 3 to 96 degrees, increased lateral pinch force from 16 to 29 N, increased the number of objects from 1 to 4 out of 6 that the participant could grasp and place in a Grasp-Release Test, and increased the Arm Motor Abilities Test score by 0.3 points. The upper-limb Fugl-Meyer score increased from 27 at baseline to 36 by the end of the study. The participant reported using the NP at home 3-4 d/wk, up to 3 h/d for exercise and household tasks. The effectiveness of the NP to assist with activities of daily living was dependent on the degree of flexor tone, which varied with task and level of fatigue. The EMG-based control strategy was not successfully implemented; button presses were used instead. Further advancements in technology may improve ease of use and address limitations caused by muscle spasticity.
    The Journal of Rehabilitation Research and Development 12/2012; 49(10):1505-16. · 1.78 Impact Factor
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    ABSTRACT: Improved hand and arm function is the most sought after function for people living with a cervical spinal cord injury (SCI). Surgical techniques have been established to increase upper extremity function for tetraplegics, focusing on restoring elbow extension, wrist movement, and hand opening and closing. Additionally, more innovative treatments that have been developed (implanted neuroprostheses and nerve transfers) provide more options for improving function and quality of life. One of the most important steps in the process of restoring upper extremity function in people with tetraplegia is identifying appropriate candidates - typically those with American Spinal Injury Association (ASIA) motor level C5 or greater. Secondary complications of SCI can pose barriers to restoring function, particularly upper extremity spasticity. A novel approach to managing spasticity through high-frequency alternating currents designed to block unwanted spasticity is being researched at the Cleveland FES Center and may improve the impact of reconstructive surgery for these individuals. The impact of these surgeries is best measured within the framework of the World Health Organization's International Classification of Function, Disability and Health. Outcome measures should be chosen to reflect changes within the domains of body functions and structures, activity, and participation. There is a need to strengthen the evidence in the area of reconstructive procedures for people with tetraplegia. Research continues to advance, providing more options for improved function in this population than ever before. The contribution of well-designed outcome studies to this evidence base will ultimately help to address the complications surrounding access to the procedures.
    Topics in Spinal Cord Injury Rehabilitation 01/2012; 18(1):43-49.
  • Michael W Keith, Allan Peljovich
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    ABSTRACT: People with spinal cord injury (SCI) have a profound loss of control of their lives and abilities. Surgical procedures are of significant benefit in improving autonomy, self-care, and body function. Functional electrical stimulation (FES) is useful at higher levels of paralysis such as ASIA C5 or C6 where there are no remaining voluntary muscles for tendon transfer and can partially replace respiration, balance, and ambulation. Outcomes studies show that surgical care improves independence, strength of grasp, and measured quality of life. Those with tetraplegia should be referred for consultation for surgical reconstruction, release of contractures, consideration for neuroprostheses, and reconstruction.
    Handbook of Clinical Neurology 01/2012; 109:167-79.
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    ABSTRACT: Nine spiral nerve cuff electrodes were implanted in two human subjects for up to three years with no adverse functional effects. The objective of this study was to look at the long term nerve and muscle response to stimulation through nerve cuff electrodes. The nerve conduction velocity remained within the clinically accepted range for the entire testing period. The stimulation thresholds stabilized after approximately 20 weeks. The variability in the activation over time was not different from muscle-based electrodes used in implanted functional electrical stimulation systems. Three electrodes had multiple, independent contacts to evaluate selective recruitment of muscles. A single muscle could be selectively activated from each electrode using single-contact stimulation and the selectivity was increased with the use of field steering techniques. The selectivity after three years was consistent with selectivity measured during the implant surgery. Nerve cuff electrodes are effective for chronic muscle activation and multichannel functional electrical stimulation in humans.
    IEEE Transactions on Neural Systems and Rehabilitation Engineering 11/2009; · 3.26 Impact Factor
  • Kevin L Kilgore, P Peckham, Michael W Keith
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    ABSTRACT: The long-term durability and safety of implanted devices is of great importance in the field of motor neuroprosthetics, where systems may possibly be utilized in excess of 50 years by some individuals. Neuroprosthetic systems have now been implanted in the upper extremity of spinal cord injured individuals for more than 20 years. The experience with these systems shows a high level of durability of the implanted components, particularly the stimulating electrodes and leads.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:7212-5.
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    ABSTRACT: The purpose of this study was to evaluate the potential of a second-generation implantable neuroprosthesis that provides improved control of hand grasp and elbow extension for individuals with cervical level spinal cord injury. The key feature of this system is that users control their stimulated function through electromyographic (EMG) signals. The second-generation neuroprosthesis consists of 12 stimulating electrodes, 2 EMG signal recording electrodes, an implanted stimulator-telemeter device, an external control unit, and a transmit/receive coil. The system was implanted in a single surgical procedure. Functional outcomes for each subject were evaluated in the domains of body functions and structures, activity performance, and societal participation. Three individuals with C5/C6 spinal cord injury received system implantation with subsequent prospective evaluation for a minimum of 2 years. All 3 subjects demonstrated that EMG signals can be recorded from voluntary muscles in the presence of electrical stimulation of nearby muscles. Significantly increased pinch force and grasp function was achieved for each subject. Functional evaluation demonstrated improvement in at least 5 activities of daily living using the Activities of Daily Living Abilities Test. Each subject was able to use the device at home. There were no system failures. Two of 6 EMG electrodes required surgical revision because of suboptimal location of the recording electrodes. These results indicate that a neuroprosthesis with implanted myoelectric control is an effective method for restoring hand function in midcervical level spinal cord injury.
    The Journal Of Hand Surgery 05/2008; 33(4):539-50. · 1.57 Impact Factor
  • Topics in Spinal Cord Injury Rehabilitation 01/2008; 13(4):37-53.
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    ABSTRACT: Testing of the recruitment properties and selective activation capabilities of a multi-contact spiral nerve cuff electrode was performed intraoperatively in 21 human subjects. The study was conducted in two phases. An exploratory phase with ten subjects gave a preliminary overview of the data and data collection process and a systematic phase with eleven subjects provided detailed recruitment properties. The mean stimulation threshold of 25 +/- 17 nC was not significantly different than previous studies in animal models but much lower than muscle electrodes. The selectivity, defined as the percent of total activation of the first muscle recruited before another muscle reached threshold, ranged from 27% to 97% with a mean of 55%. In each case, the muscle that was selectively activated was the first muscle to branch distal to the cuff location. This study serves as a preliminary evaluation of nerve cuff electrodes in humans prior to chronic implant in subjects with high tetraplegia.
    IEEE Transactions on Neural Systems and Rehabilitation Engineering 04/2007; 15(1):76-82. · 3.26 Impact Factor
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    ABSTRACT: Four nerve cuff electrodes were implanted in the shoulder and arm of one subject with high tetraplegia. Stimulation produced shoulder abduction, elbow flexion and extension, and wrist and finger extension. Recruitment properties were quantified using twitch EMG recruitment curves and tetanic moment measurements. The chronic qualitative 'function' of each channel of stimulation could be predicted from the intraoperative data collection. The average threshold was 11.3 +/- 9 nC and stabilized to this value over the 35 weeks of testing. The moment production of most muscles increased over the testing period due to exercise of the atrophied muscles. No muscle decreased its moment and most appeared to plateau after 15 weeks. Sensation was also evaluated since this subject had an incomplete injury and nerve stimulation was not found to painful throughout the range of muscle activation. Nerve electrodes have been shown to be a stable, effective means of activating muscles for neuroprosthetics.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:3584-7.
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    ABSTRACT: A second generation implantable neuroprosthesis has been developed which provides improved control of grasp-release, forearm pronation, and elbow extension for individuals with cervical level spinal cord injury. In addition to the capacity to stimulate twelve muscles, the key technological feature of the advanced system is the capability to transmit data out of the body. This allows the use of myoelectric signal recording via implanted electrodes, thus minimizing the required external components. Clinical studies have been initiated with a second generation neuroprosthesis that consists of twelve stimulating electrodes, two myoelectric signal recording electrodes, an implanted stimulator-telemeter device and an external control unit and transmit/receive coil. This system has now been implemented in nine arms in seven C5/C6 spinal cord injured individuals. The results from these subjects demonstrate that myoelectric signals can be recorded from voluntary muscles in the presence of electrical stimulation of nearby muscles. The functional results show that the neuroprosthesis provides significantly increased pinch force and grasp function for each subject. All subjects have demonstrated increased independence and improved function in activities of daily living. We believe that these results indicate that implanted myoelectric control is a desirable option for neuroprostheses.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:1630-3.
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    ABSTRACT: Neuroprostheses use electrical stimulation of paralyzed muscles to produce controlled limb movement. A first generation implanted neuroprosthesis for upper extremity function underwent a successful multi-center clinical trial and received FDA approval in 1997. We have now developed a family of second generation implanted neuroprosthetic systems. These systems provide control of grasp-release, forearm pronation, and elbow extension for individuals with cervical level spinal cord injury. The key feature of the advanced system is the capability to transmit data out of the body, allowing the use of implanted control sensors, thus minimizing the required external components. Clinical studies have been initiated with a second generation neuroprosthesis that consists of twelve stimulating electrodes, two myoelectric signal recording electrodes, an implanted stimulator-telemeter device and an external control unit and transmit/receive coil. This system has now been implemented in three C5/C6 spinal cord injured individuals, including one subject with bilateral implants. The results from these three subjects demonstrate that myoelectric signals can be recorded from voluntary muscles in the presence of electrical stimulation of nearby muscles. Myoelectric signals can be used for both discrete and proportional control signals. The results to date are promising, and all subjects have demonstrated improved function using the implanted neuroprosthesis
    Neural Engineering, 2005. Conference Proceedings. 2nd International IEEE EMBS Conference on; 04/2005
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    ABSTRACT: Nerve cuff electrodes were used intraoperatively to stimulate peripheral nerves to test electrode selectivity in the human upper extremity. Subjects were recruited from patients undergoing upper extremity nerve repair procedures. The nerves were stimulated through different contacts in the cuff and with varying parameters. Data was recorded to estimate stimulation threshold and determine selectivity data. Thresholds appeared to be higher than anticipated based on previous cat data. Preliminary selectivity was demonstrated on several nerves
    Neural Engineering, 2005. Conference Proceedings. 2nd International IEEE EMBS Conference on; 04/2005
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    ABSTRACT: To measure the satisfaction of individuals with tetraplegia with their upper-extremity reconstructive surgery. Survey. Two Spinal Cord Injury Model Systems centers. Sixty-seven individuals with spinal cord injury at the C4 through C8 motor level (107 arms). Participants had upper-extremity surgery to improve function. The surgical procedures included tendon transfers for elbow extension, wrist extension, hand grasp, and pinch or hand grasp neuroprosthesis. A survey was mailed to participants, who were asked to respond to statements such as, "If I had it to do over, I would have the hand/arm surgery again," using a 5-level Likert scale (ranging from strongly agree to strongly disagree). Seventy percent of the participants were generally satisfied with the results of their upper-extremity surgery, 77% reported a positive impact on their lives, 68% reported improvements in activities of daily living (ADLs), 66% reported improved independence, 69% reported improvement in occupation, 71% reported improved appearance or neutral, 78% reported their hand worked as well (or neutral) as it did when surgery was first performed, and 86% reported postoperative therapy as being beneficial. Upper-extremity surgery had a positive impact on life, increased ability to perform ADLs and to be independent, and improved quality of life.
    Archives of Physical Medicine and Rehabilitation 09/2003; 84(8):1145-9. · 2.36 Impact Factor
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    ABSTRACT: Implanted neuroprosthetic systems have been successfully used to provide upper-limb function for over 16 years. A critical aspect of these implanted systems is the safety, stability, and-reliability of the stimulating electrodes and leads. These components are (1) the stimulating electrode itself, (2) the electrode lead, and (3) the lead-to-device connector. A failure in any of these components causes the direct loss of the capability to activate a muscle consistently, usually resulting in a decrement in the function provided by the neuroprosthesis. Our results indicate that the electrode, lead, and connector system are extremely durable. We analyzed 238 electrodes that have been implanted as part of an upper-limb neuroprosthesis. Each electrode had been implanted at least 3 years, with a maximum implantation time of over 16 years. Only three electrode-lead failures and one electrode infection occurred, for a survival rate of almost 99 percent. Electrode threshold measurements indicate that the electrode response is stable over time, with no evidence of electrode migration or continual encapsulation in any of the electrodes studied. These results have an impact on the design of implantable neuroprosthetic systems. The electrode-lead component of these systems should no longer be considered a weak technological link.
    The Journal of Rehabilitation Research and Development 01/2003; 40(6):457-68. · 1.78 Impact Factor
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    ABSTRACT: Functional electrical stimulation of the triceps is a method of restoring elbow extension to individuals with paralyzed triceps. Eleven arms of individuals with cervical-level spinal cord injuries (SCIs) received a triceps electrode as an addition to a hand-grasp neuroprosthesis. Stimulation was controlled either as part of a preprogrammed pattern or via a switch or an accelerometer that was connected to the neuroprosthesis external controller. The outcome measures were (1) elbow extension moments at different elbow positions, (2) performance in controllable workspace experiments, and (3) comparison to an alternative method of providing elbow extension in these individuals--a posterior deltoid (PD) to triceps tendon transfer. Stimulated elbow extension moments in 11 arms ranged from 0.8 to 13.3 N.m. The stimulated elbow extension moments varied with elbow angle in a manner consistent with the length-tension properties of the triceps. Triceps stimulation provided a significantly stronger elbow extension moment than the PD to triceps tendon transfer. The elbow extension moment generated by the tendon transfer and triceps electrode being activated together was always greater than either method used separately. Stimulation of the long head of the triceps should be avoided in persons with weak shoulder abduction, since the long head adducts the shoulder and limits shoulder function in these cases. Statistically, elbow extension neuroprostheses significantly increased the ability to successfully reach and move an object and significantly decreased the time required to acquire an object while reaching.
    The Journal of Rehabilitation Research and Development 01/2003; 40(6):477-86. · 1.78 Impact Factor
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    ABSTRACT: Wuolle KS, Bryden AM, Peckham PH, Murray PK, Keith M. Satisfaction with upper-extremity surgery in individuals with tetraplegia. Arch Phys Med Rehabil 2003;84:1145–9.
    Archives of Physical Medicine and Rehabilitation - ARCH PHYS MED REHABIL. 01/2003; 84(8):1145-1149.
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    ABSTRACT: In patients who have an injury of the cervical spinal cord, the brachioradialis tendon may be transferred to the extensor carpi radialis brevis tendon to restore voluntary wrist extension. We hypothesized that the active range of motion of the wrist depends on the position of the elbow after this transfer because the brachioradialis changes length substantially during elbow flexion, which implies the maximum force that the muscle can produce varies with elbow position. The objectives of this study were to determine whether the position of the elbow influences the range of motion of the wrist following transfer of the brachioradialis to the extensor carpi radialis brevis tendon and to evaluate the effect of surgical tensioning. The range of motion of eight wrists was assessed after brachioradialis transfer. Two positions of the elbow were tested, the passive limit of elbow extension and 120 degrees of flexion. The range of motion of the wrist was also simulated with use of a biomechanical model. Using the model, we compared the active range of motion of the wrist, with the elbow at 0 degrees and 120 degrees of flexion, following three different approaches to surgical tensioning. The simulations were also repeated to evaluate how muscle strength influences outcomes. Wrist extension decreased and passive flexion increased when the elbow was flexed. Maximum wrist extension was significantly correlated with passive flexion in all subjects (r = 0.95 and p < 0.001 when the elbow was extended and r = 0.82 and p < 0.03 when the elbow was flexed). The biomechanical model suggested that tensioning the tendon transfer so that the fibers of the brachioradialis do not become excessively short when the elbow is flexed may improve outcomes. The simulations also revealed that it is more difficult to maintain a consistent wrist position with the elbow in different postures when a weaker muscle is transferred. The model suggests that altering the surgical tension could improve wrist extension when the elbow is flexed. However, the ultimate result is sensitive to the strength of the brachioradialis.
    The Journal of Bone and Joint Surgery 12/2002; 84-A(12):2203-10. · 3.23 Impact Factor
  • Michael W Keith, Harry Hoyen
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    ABSTRACT: The development of the upper extremity neuroprosthesis has been a challenging and rewarding contribution to the management of the SCI patient. The authors' experience and that of their clinical trial teams has verified that this technology is a strong alternative to conventional reconstruction and conservative management. In the future, even more powerful tools will emerge from the laboratory as these devices and collaborative surgical procedures evolve.
    Hand Clinics 09/2002; 18(3):519-28, viii. · 0.95 Impact Factor

Publication Stats

2k Citations
86.29 Total Impact Points

Institutions

  • 2002–2014
    • MetroHealth Medical Center
      Cleveland, Ohio, United States
  • 2012
    • Case Western Reserve University School of Medicine
      Cleveland, Ohio, United States
  • 1989–2012
    • Case Western Reserve University
      • • Department of Biomedical Engineering
      • • Division of Hospital Medicine (MetroHealth Medical Center)
      • • MetroHealth Medical Center
      • • Department of Orthopaedics (University Hospitals Case Medical Center)
      Cleveland, OH, United States
    • University of Delaware
      Delaware, United States
  • 2003
    • Louis Stokes Cleveland VA Medical Center
      Cleveland, Ohio, United States
  • 1997
    • Aalborg University
      • Department of Health Science and Technology
      Ålborg, North Denmark, Denmark
  • 1992
    • Shriners Hospitals for Children
      Tampa, Florida, United States