1. Departments of Neurosurgery and
2. Chicago Medical School, Rosalind Franklin University of Medicine and Science, Chicago, Illinois
3. Public Health Sciences, and
4. Departments of Orthopedic Surgery and
5. Neurosurgery, William Beaumont Hospital, Royal Oak;
6. Departments of Orthopaedic Surgery and
7. Neurosurgery, University of Michigan Hospital, Ann Arbor;
8. Department of Orthopedic Surgery, William Beaumont Hospital–Troy, Michigan; and
9. Center for Health Services Research, Henry Ford Hospital, Detroit;