Abstract
We quantified prosthesis embodiment and phantom pain reduction associated with motor control and sensory feedback from a prosthetic hand in one human with a long-term transradial amputation. Microelectrode arrays were implanted in the residual median and ulnar arm nerves and intramuscular electromyography recording leads were implanted in residual limb muscles to enable sensory feedback and motor control. Objective measures (proprioceptive drift) and subjective measures (survey answers) were used to assess prosthesis embodiment. For both measures, there was a significant level of embodiment of the physical prosthetic limb after open-loop motor control of the prosthesis (i.e., without sensory feedback), open-loop sensation from the prosthesis (i.e., without motor control), and closed-loop control of the prosthesis (i.e., motor control with sensory feedback). There was also a statistically significant reduction in reported phantom pain after experimental sessions that included open-loop nerve microstimulation, open-loop prosthesis motor control, or closed-loop prosthesis motor control. The closed-loop condition provided no additional significant improvements in phantom pain reduction or prosthesis embodiment relative to the open-loop sensory condition or the open-loop motor condition. This study represents the first long-term (14-month), systematic report of phantom pain reduction and prosthesis embodiment in a human amputee across a variety of prosthesis use cases.
Highlights
The emotional, psychological, and functional effects of upper limb amputation can be devastating
We used Utah Slanted Electrode Arrays (USEAs) implanted in residual peripheral arm nerves and implanted USEAs and electromyographic recording leads (iEMGs) implanted in residual limb muscles to provide one human subject with touch sensation, motor control, and closed-loop control of physical and virtual prosthetic hands
The present report represents the first use of the shift in perceived phantom hand location as a prosthesis embodiment metric for closed-loop controlled prostheses where feedback is provided via peripheral nerve microstimulation
Summary
The emotional, psychological, and functional effects of upper limb amputation can be devastating. Many amputees undergo a period of mourning, a chronic struggle with depression, and endurance of life-long phantom pain (Marshall et al, 1992; Desmond and MacLachlan, 2006; Bhuvaneswar et al, 2007; Ziegler-Graham et al, 2008; Hanley et al, 2009), in addition to practical difficulties associated with activities of daily living (ADL) and potential loss of employment. We hypothesize that engagement with a motorized, sensorized prosthetic hand will enhance prosthesis embodiment—i.e., meaningful integration of the prosthesis into one’s body image—and phantom pain reduction Such consequences, together with sophisticated functional prosthesis use, may in turn improve many of these aspects of life for amputees, and may result in substantial cost savings to healthcare organizations and payment agencies. For commercially-available prostheses, the residual limb does not provide the sophisticated multi-DOF motor control provided by an intact hand
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