Self-reported use of an implanted FES hand system by adolescents with tetraplegia

An implanted upper-extremity neuroprosthesis using myoelectric control

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

These results indicate that a neuroprosthesis with implanted myoelectric control is an effective method for restoring hand function in midcervical level spinal cord injury.

Analyse critique des modalités d’évaluation des résultats de la chirurgie fonctionnelle du membre supérieur tétraplégique. Revue de la littérature sur les 50 dernières années

OBJECTIVE

To study the methods of assessment of upper limb functional surgery in the literature.

METHODS

The literature review relating to the years 1950-2002 was carried out with three data bases: Medline, Pascal, Embase. This review also involved a thorough study of non-indexed references.

RESULTS

Although many instruments or tests are used to assess outcome after surgery, their reliability, validity and responsiveness have not been adequately proven. Methodology appears to be the major failing of the various scales used to assess these patients. The conceptual models underlying the evaluation are all too often unspecified. There is a lack of pertinence of the selected tasks for tetraplegics. There is limited documentation of the guiding framework or conceptualisation. Furthermore, the process of item selection is often unknown. Scales or instruments are also deemed to be too insensitive to document the small but meaningful functional gains made by tetraplegics after functional surgery.

CONCLUSION

To answer the need for a specific assessment tool for tetraplegics who undergo functional surgery, we have developed a national, multicenter, prospective and longitudinal study based on two concepts: the first concept is related to Life Habits that are the activities of daily living and social roles recognised by the socio-cultural context of a person according to age, sex and social and personal identity. They include activities that should be accomplished on a daily basis (nutrition, fitness, personal care, communication, mobility, etc.). Life Habits presenting a significant level of disruption can create handicap situations. The second concept is in relation with Motor Capacities that correspond to the abilities of a patient to perform basic and functional tasks regardless of contextual factors (environmental and personal factors).

Neuroprostheses for the upper extremity

Functional electrical stimulation (FES) neuroprostheses can be used to replace lost motor and sensory function in persons with neurological disorders. FES technology has subsequently been shown effective and safe in restoring hand function in adults with spinal cord injury. The freehand system consists of an implanted receiver-stimulator, an external shoulder position sensor, and an external control unit. Commands are originated by voluntary movement of the contralateral shoulder and are measured by the sensor. There are several types of electrodes: epimysial, intramuscular, nerve cuff, and intraneural. Neuroprostheses are recommended within the context of all available reconstructive options for the upper limbs. Voluntary tendon transfers are the first choice. The clinical outcomes as measured by improvement on scales of impairment, activities of daily living, and satisfaction are rewarding. The next step in improvement of the motor function of person with spinal cord injury will be the addition of a controllable second upper extremity and the elimination of additional external hardware.