1. Department of Neurosurgery, Amsterdam University Medical Center, Amsterdam, the Netherlands.
2. Department of Neurosurgery, Haaglanden Medical Center, the Hague, the Netherlands.
3. Department of Orthopedic Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
4. Department of Orthopedic Surgery, Erasmus Medical Center, Rotterdam, the Netherlands.
5. Department of Plastic and Reconstructive Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
6. De Hoogstraat Rehabilitation, Utrecht, the Netherlands.
7. Division of Neurosurgery and Spine Program, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.