1. Department of Orthopaedic Surgery, Zuyderland Medical Centre, Henri Dunantstraat 5, 6419 PC Heerlen, The Netherlands
2. CAPHRI School for Public Health and Primary Care, Maastricht University, P. Debyelaan 25, 6229 HX Maastricht, The Netherlands
3. Department of Neurosurgery, Maastricht University Medical Centre, P. Debyelaan 25, 6229 HX Maastricht, The Netherlands
4. Department of Neurosurgery, Zuyderland Medical Centre, Henri Dunantstraat 5, 6419 PC Heerlen, The Netherlands
5. Department of Neurology Zuyderland Medical Centre, Henri Dunantstraat 5, 6419 PC Heerlen, The Netherlands