1. Department of Orthopedic Surgery, Rothman Orthopedic Institute, Thomas Jefferson University, Philadelphia, PA
2. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, PA
3. Department of Biomedicine, Neurosurgical Unit, Neurosciences and Advance Diagnostics, University of Palermo, Palermo, Italy
4. Department of Neurosurgery, Duke University Medical Center, Durham, NC
5. Department of Orthopedic Surgery, The Johns Hopkins University, Baltimore, MD