James S Harrop MD FACSProfessor of Neurological and Orthopaedic Surgery, Director, Division of Spine and Peripheral Nerve Disorders, Neurosurgical Director Delaware Valley SCI Centre, Jefferson Medical College, Philadelphia, PA, USAAhmed J Awad MDPost-Doctoral Fellow, Neurosurgery, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus, PalestineAlexander R Vaccaro MD PhDThe Everett and Marion Gordon Professor of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University Medical Centre, Philadelphia, USA