A MULTICENTER STUDY OF AN IMPLANTED NEUROPROSTHESIS

FOR RESTORING HAND GRASP IN TETRAPLEGIA

P. Hunter Peckham, PhD*†‡; Michael W. Keith, MD*†‡; Kevin L. Kilgore, PhD*†‡;

Julie H. Grill, MS§; Kathy S. Wuolle, OTR/L, CHT§; Geoffrey B. Thrope§; Peter Gorman, MDxx¶;

John Hobby**, FRCS; MJ Mulcahey OTR/L††; Sara Carroll, PT‡‡; Vincent R. Hentz, MD§§xxxx; and Allen Wiegner, PhD¶¶***

* Department of Veteran’s Affairs, † MetroHealth Medical Center, and‡ Case Western Reserve University, Cleveland, Ohio

^§ NeuroControl Corporation, Cleveland, Ohio xx VA Maryland Healthcare System, Baltimore, Maryland

¶ University of Maryland Medical System, Baltimore, Maryland ^** Salisbury District Hospital, Salisbury, UK

†† Philadelphia Shriners Hospital, Philadelphia, Pennsylvania ‡‡The University of Melbourne, Australia

^§§ Stanford University Medical Center, Palo Alto, CA xxxx Palo Alto Veterans Affairs Health Care Service, Palo Alto, CA

¶¶ VA Boston Health Care System, West Roxbury, MA ^*** Harvard Medical School, Cambridge, MA

Abstract

A multi-center trial was conducted to evaluate the efficacy of an implanted neuroprosthesis for restoring hand function. Ten spinal cord injury care centers participated in the study. Fifty-one adult tetraplegic individuals with C5 or C6 spinal cord injuries were studied. Of 50 evaluable participants, pinch force was significantly greater with the neuroprosthesis in all 50, and grasp-release abilities were improved in 49. All tested participants (49/49) were more independent in performing activities of daily living with the neuroprosthesis than they were without it. Home use of the device for regular function and exercise was reported by over 90% of the participants, and satisfaction with the neuroprosthesis was high. We conclude that the neuroprosthesis is safe, well accepted by the users, and offers improved independence for C5 and C6 spinal cord injured individuals.

Introduction/Background

Functional electrical stimulation (FES) can be used to provide grasp and release function for cervical level spinal cord injured individuals. An implanted neuroprosthetic hand-grasp system was developed to restore the ability to grasp, hold, and release objects for individuals with level C5 or C6 tetraplegia.[1] This study was conducted to evaluate the safety, efficacy, and clinical impact of the neuroprosthesis.

Methods

The neuroprosthesis provides unilateral hand grasp and release to tetraplegic individuals using coordinated electrical stimulation of the paralyzed hand and forearm muscles. The neuroprosthesis has both implanted and external components (Figure. 1). The implanted components include an eight-channel receiver-stimulator device and epimysial electrodes (Figure 2). The user controls the opening and closing of their hand using movements of the contralateral shoulder, measured by a skin-mounted joystick.

The primary inclusion criteria for participants in this study were: 1) a traumatic spinal cord injury resulting in tetraplegia at the C5 or C6 motor level with impairment grade A or B (complete) occurring at least 1 year before implantation, and 2) intact lower-motor-neuron innervation of key muscles of the forearm and hand

The receiver-stimulator and eight epimysial electrodes were implanted in a single surgical procedure. Implementation and evaluation protocols were standardized across all study centers.

The study was conducted at 10 centers; 8 in the United States, and 1 each in the United Kingdom and Australia. Each participant served as his or her own control. This design was possible because individuals were tested with the neuroprosthesis on and off. Study evaluations included pinch strength, active range of motion and grasp and release ability (using the Grasp-Release Test [2,3]). Functional ability was evaluated using either an Activities of Daily Living (ADL) Abilities Test [1], or an ADL Assessment test. A user satisfaction survey was administered at one-year post-implant to assess satisfaction and use [4]. Functional outcome data were collected from August, 1986 to August, 1997, when the US Food and Drug Administration gave pre-market approval application.

Results

Fifty-one individuals received an implanted neuroprosthesis and were studied (Table 1). Pinch force in both grasp patterns increased significantly with the use of the neuroprosthesis in all participants tested (Figure 3). In the Grasp-Release test, 49 of the 50 participants (98%) moved at least one more object with the neuroprosthesis, and 37 (74%) improved by moving at least three more objects than they could with the neuroprosthesis turned off. Manipulation of larger and heavier objects was greatly improved with the neuroprosthesis (Figure 4).

Table 1. Demographic and Clinical Characteristics of 51 Tetraplegic Participants Receiving an Implanted Neuroprosthesis to Restore Hand Grasp

Characteristic	Participants Receiving Implant
Number (%) Men Number (%) Women	42 (82%) 9 (18%)
Injury level, n (%) [ASIA/IC]* C5/0 C5/1 C6/1 C6/2 C6/3	15 (29%) 20 (39%) 2 (4%) 13 (26%) 1 (2%)
Median time, injury to implant, years (min to max)	4.6 (1.1 to 32.2)
Median age at implant, years (min to max)	32 (16 to 57)
Median Follow-up time, years (min to max)	5.4 (3.0 - 13.9)

* The ASIA motor level is based on the presence of antigravity (3/5) strength in biceps and wrist extension for C5 and C6 levels, respectively. The International Classification (IC) for Surgery of the Hand in Tetraplegia identifies the number of forearm muscles that have at least 4/5 voluntary strength. Patients have an IC score of 1 if the brachioradialis meets this criterion, a 2 if the extensor carpi radialis longus also meets this criterion and a 3 if, in addition, the extensor carpi radialis brevis meets this criterion.

Min to max = minimum to maximum values

Disability was reduced in all 49 participants tested, as measured by either the ADL Abilities or ADL Assessment Tests. All participants were more independent in at least two activities (Figure 5). The Satisfaction Survey was administered to 40 participants. User satisfaction with the neuroprosthesis was high. Ninety-seven percent (34/35) of participants would recommend the neuroprosthesis to others, and 91% (32/35) stated that the neuroprosthesis improved their quality of life. Device usage was also high (Figure 6). Regular device usage for functional activities was reported by 34/40 participants, and three additional participants use the device regularly for exercise.

Discussion/Conclusions

An implantable neuroprosthesis that provides hand grasp for C5- and C6-level spinal cord injured individuals has now completed a prospective, multi-center clinical trial, has received FDA pre-market approval and is now marketed as the FREEHANDâ System (NeuroControl Corporation, Cleveland, Ohio). Fifty of the 51 participants studied demonstrated
improved function when using the neuroprosthesis. No participant lost function as a result of the neuroprosthesis, and there were few adverse events. Over 90% of the implant recipients indicated that they used the neuroprosthesis regularly for either function or exercise or both. This compares favorably with the reported usage rates for commercial FNS devices that are based on surface stimulation technology, which have reported usage rates of 17% to 50% [5-7]. Also, our long term follow up data show that daily use of the neuroprosthesis is maintained beyond three years.

As with any implanted device, the time and monetary cost of implementation is an important consideration. We have shown that the monetary cost of the neuroprosthesis used in this study can be recovered by a concomitant reduction in personal attendant services [8], as shown in Figure 7. This analysis was based purely on the direct monetary costs, without even considering any potential value provided by the neuroprosthesis in terms of improved quality of life.

In summary, this new technology offers an improved quality of life and increased independence for a population without comparable alternatives. The results of this multi-center study indicate that an upper-extremity neuroprosthesis provides substantial added function for C5- and C6-level spinal-cord injured individuals. We propose that neuroprosthetic intervention should be considered as an important option in the treatment of C5/C6 tetraplegic individuals.

References

[1] Kilgore KL, Peckham PH, Keith MW, Thrope GB, Wuolle KS, Bryden AS, et al. An implanted upper extremity neuroprosthesis: A five patient review. J Bone Joint Surg 1997;79A(4):533-41.

[2] Wuolle KS, Van Doren CL, Thrope GB, Keith MW, Peckham PH. Development of a quantitative hand grasp and release test for participants with tetraplegia using a hand neuroprosthesis. J Hand Surg 1994;19A:209-18.

[3] Smith BT, Mulcahey MJ, Betz RR. Quantitative comparison of grasp and release abilities with and without functional neuromuscular stimulation in adolescents with tetraplegia. Paraplegia 1996;34:16-23.

[4] Wuolle KS, Van Doren CL, Bryden AM, Peckham PH, Keith M, Kilgore KL, Grill J. Satisfaction with and usage of a hand neuroprosthesis. Arch Phys Med Rehabil 1999;80:206-13.

[5] Popovic D, Stojanovic A, Pjanovic A, Radosavljevic S, Popovic M, Jovic S, Vulovic D. Clinical evaluation of the bionic glove. Arch Phys Med Rehabil 1999;80:299-304.

[6] Snoek GJ, Ijzerman MJ, in 't Groen FACG, Stoffers TS, Zilvold G. Use of the NESS handmaster to restore handfunction in tetraplegia: clinical experiences in ten patients. Spinal Cord 2000;38:244-249.

[7] Brissot R, Gallien P, Le Bot MP, Beaubras A, Laisne D, Beillot J, Dassonville J. Clinical experience with functional electrical stimulation-assisted gait with Parastep in spinal cord-injured patients. Spine 2000;25:501-508.

[8] Creasey G, Kilgore KL, Brown-Triolo DL, Dahlberg JE, Peckham PH, Keith MW. Reduction of costs of disability using neuroprostheses. Assistive Technology 2000;12:67-75.

Acknowledgments: This study was funded in part by the Department of Veterans Affairs Rehabilitation Research and Development Service, the NIH National Institute of Neurological Disorders and Stroke Neural Prosthesis Program, and the Food and Drug Administration Office of Orphan Product Development Grant No. 000832. Clinical trial support was provided by NeuroControl Corporation, manufacturer of the Freehand ® System. Additional funding was provided by the NIH General Clinical Research Center 5M01RR 00080, the Inspire Foundation in the UK, and the Shriners Hospitals for Children Grant 9530.