Limitations of Current Prosthetic Technology

The Challenge of Prosthetic Acceptance

Current limitations in prosthetic technology hinder acceptance among amputees. Researchers in the United States are investigating whether new computerized prosthetic hands can enhance control through improved kinesthesia.

Modern vs. Traditional Prosthetics

While contemporary prosthetics allow amputees to perform basic movements, many still prefer older models, such as cable-actuated split-hook grippers and body-powered elbows. These traditional devices provide a degree of kinesthesia, which is the awareness of position and movement that modern computerized models often lack. This kinesthetic sense is vital as it gives amputees a greater sense of agency over their prosthetics. Fully motorized prosthetics, devoid of any kinesthetic feedback, require constant monitoring, which can reduce an amputee’s acceptance and limit their movement efficiency and multitasking capabilities.

Innovative Research in Prosthetic Technology

Exploring Regenerative Neural Interfaces

In response to these challenges, a research team in Cleveland, USA, has published findings in the journal Science Translational Medicine. Their study focuses on implanted regenerative neural interfaces and the concept of illusory kinesthesia to enhance the acceptance and functionality of motorized prosthetic hands among amputees.

Research Methodology

The research involved six amputees who underwent surgery to redirect motor and sensory nerves to muscles in the upper arm, such as the biceps and triceps. These reinnervated nerves could be stimulated with vibrations, allowing amputees to experience the sensation of movement in joints that were no longer present. Electromyographic (EMG) signals stimulated the prosthetic limbs, enabling the detection of 22 distinct hand and forearm muscle movements across the participants, all originating from the biceps, triceps, brachialis, or pectoralis muscles.

Coupling Virtual Prosthetics with Kinesthetic Feedback

The researchers demonstrated that by integrating a virtual prosthetic, rendered by a computer, and a vibration unit worn by the amputees to stimulate their reinnervated nerves, amputees could perceive changes in the computerized prosthetic. Using vibration-induced illusory movements, these individuals could manipulate virtual prosthetic hands with precision comparable to five able-bodied individuals performing similar tasks. Additionally, the combination of vision and kinesthesia resulted in enhanced confidence in their movements for three of the amputees.

Technological Integration for Enhanced Control

One participant was fitted with a thermoplastic prosthetic socket that merged previous EMG and kinesthetic vibratory technologies. This integration allowed the amputee to control a dexterous robotic hand while receiving kinesthetic feedback through vibrations.

Implications of Vibration-Induced Illusory Movement

Improving Agency and Control

The study successfully illustrated that vibration-induced movement enhances an amputee’s sense of agency regarding their prosthetic. Moreover, the integration of vision and kinesthesia significantly improved the control of prosthetic hands for users.

Limitations and Future Research

A key limitation of this study is the small sample size, which was a result of time constraints. This limitation restricts the ability to conduct meaningful statistical analyses on the results. However, the depth of investigation into vibration-induced illusory movements on prosthetic use provides a compelling foundation for further exploration of this emerging technology.

Reference

Marasco PD, et al. (2018) Illusory movement perception improves motor control for prosthetic hands. Science Translational Medicine Vol. 10, Issue 432.