Experiment on Comparative Validation of the Destabilizing Factors in Surface Myoelectric Interface for Prosthetic Control

The use of an adjustable electrode housing unit to compare electrode alignment and contact variation with myoelectric prosthesis functionality

“…The aim of this study was not to pinpoint 'optimal' electrode alignment but to provide an assessment of the effect of alignment variations that may realistically occur using a pool of inexperienced prosthetists. Although electrode alignment has previously been shown to have a more significant effect on signal strength than contact pressure in a generic context, 7 this study used practical manipulation assessment to show that both factors can have a significant effect on prosthesis functionality. The adjustable bespoke unit used within this study mirrors the evident adjustability of other types of prosthesis control.…”

“…It is generally accepted that effective signal acquisition depends upon the electrodes being securely attached to the skin’s surface, and also placed along the long axis of the target muscle fibres. 7,8 In addition, maintaining the electrode positioned along the long axis of the muscle fibre has been shown to maximise the acquired signal strength since the signal acquired will comprise the summative voltage of all the fibres that are detected by the electrode. 3,7 Misalignment of the electrodes can also increase the chance of cross-talk, where muscle fibres from muscles other than the target muscle may be transduced and hence affect the operation of the prehensor.…”

“…7,8 In addition, maintaining the electrode positioned along the long axis of the muscle fibre has been shown to maximise the acquired signal strength since the signal acquired will comprise the summative voltage of all the fibres that are detected by the electrode. 3,7 Misalignment of the electrodes can also increase the chance of cross-talk, where muscle fibres from muscles other than the target muscle may be transduced and hence affect the operation of the prehensor. 8 Anecdotal evidence suggests that standard clinical practice is to place the long axis of the electrodes on an area parallel to the long axis of the residuum with maximum signal strength; this can be 'trial and error', particularly in paediatric cases.…”

Fabrication and application of an adjustable myoelectric transhumeral prosthetic socket

“…14 In response, the user may need to increase muscle contraction to control the device, leading to fatigue. Should a gap form between the electrode and limb, motion artifacts may be introduced to the signal resulting in unintentional movement of the prosthesis, 15 or a loss of control over the corresponding motion. In contrast, if contact pressure is increased, the sensor may register higher amplitude signals and may trigger unintentional prosthetic movement.…”