1. Golden State Orthopedics and Spine, Oakland, California, USA;
2. Department of Neurosurgery, Hurley Medical Center, Flint, Michigan, USA;
3. Department of Surgery, Michigan State University, East Lansing, Michigan, USA;
4. College of Science and Technology, Temple University, Philadelphia, Pennsylvania, USA;
5. Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington, USA