Abstract
BackgroundReplacement of a lost limb by an artificial substitute is not yet ideal. Resolution and coordination of motor control approximating that of a biological limb could dramatically improve the functionality of prosthetic devices, and thus reduce the gap towards a suitable limb replacement.MethodsIn this study, we investigated the control resolution and coordination exhibited by subjects with transhumeral amputation who were implanted with epimysial electrodes and an osseointegrated interface that provides bidirectional communication in addition to skeletal attachment (e-OPRA Implant System). We assessed control resolution and coordination in the context of routine and delicate grasping using the Pick and Lift and the Virtual Eggs Tests. Performance when utilizing implanted electrodes was compared with the standard-of-care technology for myoelectric prostheses, namely surface electrodes.ResultsResults showed that implanted electrodes provide superior controllability over the prosthetic terminal device compared to conventional surface electrodes. Significant improvements were found in the control of the grip force and its reliability during object transfer. However, these improvements failed to increase motor coordination, and surprisingly decreased the temporal correlation between grip and load forces observed with surface electrodes. We found that despite being more functional and reliable, prosthetic control via implanted electrodes still depended highly on visual feedback.ConclusionsOur findings indicate that incidental sensory feedback (visual, auditory, and osseoperceptive in this case) is insufficient for restoring natural grasp behavior in amputees, and support the idea that supplemental tactile sensory feedback is needed to learn and maintain the motor tasks internal model, which could ultimately restore natural grasp behavior in subjects using prosthetic hands.
Highlights
The last decade has witnessed significant progress in the field of upper limb prosthetics
As measured by the VET6N, this study suggests that implanted epimysial electrodes improve grip force control of a prosthetic hand over surface EMG
Even though one Conclusions This study assessed the control of an osseointegrated prosthesis via implanted epimysial electrodes and compared this configuration to the conventional surface electrodes approach
Summary
The last decade has witnessed significant progress in the field of upper limb prosthetics. Mastinu et al Journal of NeuroEngineering and Rehabilitation (2019) 16:49 of signals recorded over the skin curtails its reliability Factors such as temperature, electromagnetic interference, body impedance changes, and motion artefacts can have a destructive effect on the reliability of sEMG-based prosthetic devices. Whereas the differences between implantable and sEMG electrodes have been investigated in terms of signal to noise ratio, selectivity, and stability [5], only a few studies compared them from the perspective of an interface for prosthetic control [11,12,13]. None explored their effects on functional tasks. Resolution and coordination of motor control approximating that of a biological limb could dramatically improve the functionality of prosthetic devices, and reduce the gap towards a suitable limb replacement
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