Model-based analysis of a distal sensory feedback implant for thumb prostheses

Naturalistic sensory feedback is crucial for improving the functionality and acceptance of upper-limb prostheses. Electrical stimulation of peripheral nerves via implanted electrodes has shown a viable approach to providing real-time sensory information to hand prostheses. Although the loss of digits accounts for most upper-limb amputations, no existing digital prosthesis incorporates sensory feedback. This would be particularly important in the case of thumb amputation, as it leads to major functional impairments. Here, we present a computational model to assess the feasibility of using a cuff electrode to provide sensory feedback to thumb prostheses. We propose the distal index-thumb branch of the median nerve as an ideal implantation site and derive a plausible topography for its fascicular organization. We then employ surrogate models of fiber activation to enable rapid and accurate evaluation of the implant performance. Our results demonstrate that while the system can achieve selective sensory feedback to the thumb at coarse levels, delivering fine-grained sensory information remains challenging. Future developments in cuff electrode design and stimulation protocols will be necessary to enhance feedback resolution while preventing unintended activation of the first lumbrical muscle.Clinical Relevance- Our in-silico analysis supports the development of distal implants based on cuff electrodes for providing sensory feedback to thumb prostheses.