1. Department of Neurosurgery, Leiden University Medical Center, University Neurosurgical Center Holland, Leiden, The Netherlands
2. Department of Neurosurgery, Haaglanden Medical Center, University Neurosurgical Center Holland, The Hague, The Netherlands
3. The Health Scientist, The Hague, The Netherlands
4. Department of Neurosurgery, Maastricht University Medical Center, Academic Neurosurgical Center Limburg, Maastricht, The Netherlands
5. Department of Neurosurgery, Zuyderland Medical Center, Academic Neurosurgical Center Limburg, Heerlen, The Netherlands
6. Department of Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands
7. Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands
8. CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands
9. Department of Neurosurgery, Spaarne Gasthuis, Haarlem, The Netherlands