Investigation performed at the Departments of Orthopaedic Surgery and Neurology, Emory University School of Medicine, Atlanta.* No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.** Schenectady Orthopedic Associates, 847 Union Street, Schenectady, New York 12308.*** The Emory Clinic Spine Center, 2165 North Decatur Road, Decatur, Georgia 30033.**** Department of Neurology, The Emory Clinic Spine Center, 1365 Clifton Road N.E., Atlanta, Georgia 30322.