1. Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
2. Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, Department of Spinal Surgery, First Affiliated Hospital of Sun Yat-sen University, Guangzhou 51008, P. R. China.
3. Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
4. Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.