1. a Institute of Science and Technology in Medicine, Keele University, The Guy Hilton Research Centre , Thornburrow Drive, Hartshill, Stoke-on-Trent , Staffordshire , ST4 7QB , UK
2. b ConMed-Linvatec Biomaterials Ltd , Tampere , Finland
3. c Department of Biomedical Engineering , Tampere University of Technology , Tampere , Finland
4. d Department of Surgery , Oulu University Hospital , Oulu , Finland