1. Center for Bionics and Pain Research, Mölndal 43130, Sweden
2. Department of Electrical Engineering, Chalmers University of Technology, Gothenburg 41296, Sweden
3. Operational Area 3, Sahlgrenska University Hospital, Mölndal 43180, Sweden
4. Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg 41345, Sweden