1 Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul, Korea.
2 Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul, Korea. spinelee@snu.ac.kr.
3 Department of Orthopedic Surgery, Seoul Metropolitan Government - Seoul National University Boramae Medical Center, 20 Boramaero 5-gil, Dongjak-gu, Seoul, 07061, Korea. spinelee@snu.ac.kr.