1. Division of Neurosurgery, University Medical Center Physicians, Lubbock, Texas, USA;
2. Department of Neurosurgery, Baylor College of Medicine, Houston, Texas, USA
3. Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, Texas, USA;
4. Department of Orthopedic Surgery, Texas Tech University Health Sciences Center, Lubbock, Texas, USA;