1. Greater Baltimore Neurosurgical Associates, Baltimore, Maryland;
2. Spine Institute of Louisiana, Shreveport, Louisiana;
3. Department of Neurological Surgery, University of California, Davis, Sacramento, California;
4. Texas Back Institute, Plano, Texas;
5. Orange County Neurosurgical Associates, Laguna Hills, California;
6. Cedars-Sinai Spine Center, Los Angeles, California;
7. Orthopaedics Northeast, Fort Wayne, Indiana;
8. Oklahoma Brain and Spine Institute, Tulsa, Oklahoma; and
9. Precision Spine Care, Tyler, Texas