Neuroprostheses may provide the most promising gains in arm and hand function to individuals with SCI (Kilgore et al., 2018). Neuroprostheses utilize functional electrical stimulation or myoelectrically controlled systems to move prostheses or robotic end effectors. This is achieved through stimulation of residual motor nerves via transcutaneous, percutaneous, or implanted electrodes (Krucoff et al., 2016). Transcutaneous stimulation utilizes electrodes placed on the surface of the skin to stimulate a motor point of the muscle of interest (Baker et al., 1993; Mortimer 1981, while percutaneous and fully implanted electrodes are placed under the skin or in the muscle to stimulate the motor nerve of the muscle of interest (Cameron et al., 1997; Hoshimiya & Nanda 1989).
A variety of neuroprosthetic systems exist including the Handmaster-NMS-1, BGS, and ETHZ-ParaCare systems. All have been applied successfully as rehabilitation tools to restore grasping function in individuals with SCI. However, the most widely used neuroprosthesis for grasping is the Freehand system. Generally, to control the neuroprosthesis, individuals use an on/off switch or apply analog sensors to generate a desired command. There is usually a time delay of one or two seconds from command issue to grasp execution. Therefore, the speed that an individual can grasp and release objects is somewhat limited. Besides the technological drawbacks of neuroprostheses, an important barrier contributing to the use of neuroprostheses (or lack thereof) is the commercial availability of the device. Despite demonstrated improvements in upper extremity function and QOL following stroke or SCI, only one device is commercially available (Venugopalan et al., 2015). For a full list of the benefits and drawbacks of neuroprostheses, please refer to Table 10.
Table 10: Benefits and Drawbacks of Neuroprostheses Systems
|Benefits of Neuroprostheses||Drawbacks of Neuroprostheses|
Neuroprostheses can increase independence, reduce the need for other assistive devices, and decrease the time it takes to carry out activities of daily living (Kilgore et al., 2018). As such, neuroprotheses are typically used to complete tasks such as eating, drinking and personal hygiene. It is important to note that neuroprostheses are distinct from brain computer interfaces. Neuroprostheses connect any part of the nervous system to a device, whereas BCIs connect the brain with a computer and/or robotic system (Krucoff et al., 2016).
With advances in the technological capacity of neuroprostheses, many studies have examined their use in individuals with SCI. As such, the methodological details and results from 18 studies are presented in Table 11.