Determine socket shift in trans-radial amputees using ultrasound and 3 D motion capture

In pattern recognition-based myoelectric control several robustness problems are well known. Different positions of the upper limbs and donning and doffing cause unintended electrode shifts (pistoning) with adverse effects on classification accuracy. To our knowledge the shift of the socket with respect to bony structures has never been assessed. We developed a set up to measure the shift of the socket with ultrasound and 3 D motion capture system in trans-radial amputees. We got obtained accuracy values with .655 mm for our set up. A pilot measurement showed high reliability and a displacement of the socket around 2 mm. We are going to conduct further test measurements and develop parameters to distinguish longitudinal and perpendicular shift of the socket. In future works pistoning parameter should be considered in order improve pattern recognition based myoelectric control.