1. Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
2. Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
3. Departments of Orthopaedic Surgery and Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland
4. Departments of Neurosurgery, Oncology, and Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland