1. Department of Physiology, Anatomy and Genetics, University of OxfordOxford OX1 3QX, UK
2. Centre for Computational Science, University College LondonLondon WC1H 0AJ, UK
3. Institute for Research in Applicable Computing, University of BedfordshireBedfordshire LU1 3JU, UK
4. Istituto Ortopedico Rizzoli, via di Barbiano 1/10, 40136 Bologna, Italy