Daniel V C Stoffelen1, Koen Eraly2, Philippe Debeer3. 1. Orthopaedics, GZA St Augustinus Hospital, Wilrijk, Belgium. Electronic address: dannystoffelen@yahoo.com. 2. Department of Mechanical Engineering, Katholieke Universiteit Leuven, Leuven, Belgium; Mobelife R&D, Heverlee, Belgium. 3. Orthopaedics, University Hospitals Leuven, Department of Development and Regeneration, Katholieke Universiteit Leuven, Pellenberg, Belgium.