1. Division of Neurological Surgery, University of Alabama, Birmingham, Alabama;
2. Division of Neurosurgery, David Geffen School of Medicine, University of California at Los Angeles;
3. Department of Neurosurgery, University of California at San Francisco, California;
4. Departments of Orthopaedic Surgery and
5. Department of Neurosurgery, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, Massachusetts;
6. Department of Neurosurgery, University of Medicine and Dentistry of New Jersey—New Jersey Medical School, Newark, New Jersey;
7. Department of Neurological Surgery, Neurological Institute, Columbia University, New York, New York;
8. Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa;
9. Department of Neurosurgery, Mount Sinai School of Medicine, New York, New York; and
10. Department of Orthopaedic Surgery, Milton S. Hershey Medical Center, Pennsylvania State College of Medicine, Hershey, Pennsylvania
11. Neurological Surgery, University of Wisconsin, Madison, Wisconsin;