[1] Department of Orthopaedic Surgery, Washington University School of Medicine, Campus Box 8233, St. Louis, MO 63110, One Barnes-Jewish Hospital Plaza
[2] Department of Neurologic Surgery, University of Wisconsin Hospital, Madison, WI 53792-0001
[3] Emory Spine Center, Emory University School of Medicine, Atlanta, GA 30329
[4] Rothman Institute at Jefferson, Philadelphia, PA 19107-4216
[5] University of California at Los Angeles, Department of Orthopaedic Surgery and Neurosurgery, University of California at Los Angeles School of Medicine, Santa Monica, CA 90404