1. Orthopaedic Research Laboratory; Department of Orthopaedics; Nijmegen Centre for Molecular Life Sciences; Radboud University Nijmegen Medical Centre; 547 Orthopaedic Research Laboratory; P.O. Box 9101 6500 HB Nijmegen The Netherlands
2. Department of Biomaterials Science and Technology; MIRA Institute; University of Twente; Enschede, P.O. Box 217 7500 AE Enschede The Netherlands
3. Department of Biomedical Engineering; W. J. Kolff Institute; University Medical Centre Groningen; University of Groningen; Antonius Deusinglaan 1 9713 AV Groningen The Netherlands