1 *Spine Center and Department of Orthopaedic Surgery, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Sungnam, Republic of Korea †Department of Orthopaedic Surgery, Seoul National University College of Medicine and Seoul National University Hospital, Seoul, Republic of Korea ‡ClinResearch Sdn Bhd and §Stats Consulting Sdn Bhd, Petaling Jaya, Selangor, Malaysia; and ¶Department of Orthopaedic Surgery, Kangwon National University Hospital, Gangwon-do, Korea