1. Department of Orthopedic Surgery, Rijnstate, Arnhem, Gelderland, The Netherlands
2. Department of Neurology, A.S.S.T. della Franciacorta, Chiari, Italy
3. Department of Clinical Sciences and Community Health, Universita degli Studi di Milano, Milano, Lombardia, Italy
4. Department of Orthopedic Surgery, Amphia Ziekenhuis, Breda, North Brabant, The Netherlands
5. Department of Orthopedic Surgery, AMC, Amsterdam, The Netherlands