Sarah Stamm1, John W McClellan1, Annie Knierim2, Ian P Suiter3, K Daniel Riew4. 1. Nebraska Spine Center, 13616 California Street, Suite 100, Omaha, NE 68154. 2. Department of Orthopaedic Surgery and Rehabilitation, University of Nebraska Medical Center, 981080 Nebraska Medical Center, Omaha, NE 68198-1080. Email address: aknierim@unmc.edu. 3. Washington University in St. Louis, Campus Box 6779, 6985 Snow Way Drive, St. Louis, MO 63130. 4. Washington University Orthopedics, Campus Box 8233, 660 South Euclid Avenue, St. Louis, MO 63110.