1. Department of Orthopaedics, St. Maartenskliniek, P. O. Box 9011, 6500 GM Nijmegen, The Netherlands.
2. Department of Orthopaedics, Canisius-Wilhelmina Hospital, P. O. Box 9015, 6500 GS, Nijmegen, The Netherlands.
3. Orthotrauma Research Center, Academic Medical Center, P. O. Box 22660, 1100 DD, University of Amsterdam, Amsterdam, The Netherlands.
4. Department of Anatomy and Embryology, University of Nijmegen, P. O. Box 9101, 6500 HB, Nijmegen, The Netherlands.