title: Radiologic Findings and Risk Factors of Adjacent Segment Degeneration after Anterior Cervical Discectomy and Fusion : A Retrospective Matched Cohort Study with 3-Year Follow-Up Using MRI.
abstract: OBJECTIVE
  The purpose of this study was to figure out the radiologic findings and risk factors related to adjacent segment degeneration (ASD) after anterior cervical discectomy and fusion (ACDF) using 3-year follow-up radiography, computed tomography (CT), and magnetic resonance image (MRI).
  
  
  METHODS
  A retrospective matched comparative study was performed for 64 patients who underwent single-level ACDF with a cage and plate. Radiologic parameters, including upper segment range of motion (USROM), lower segment range of motion (LSROM), upper segment disc height (UDH), and lower segment disc height (LDH), clinical outcomes assessed with neck and arm visual analogue scale (VAS), and risk factors were analyzed.
  
  
  RESULTS
  Patients were categorized into the ASD (32 patients) and non-ASD (32 patients) group. The decrease of UDH was significantly greater in the ASD group at each follow-up visit. At 36 months postoperatively, the difference for USROM value from the preoperative one significantly increased in the ASD group than non-ASD group. Preoperative other segment degeneration was significantly associated with the increased incidence of ASD at 36 months. However, pain intensity for the neck and arm was not significantly different between groups at any post-operative follow-up visit.
  
  
  CONCLUSIONS
  The main factor affecting ASD is preoperative other segment degeneration out of the adjacent segment. In addition, patients over the age of 50 are at higher risk of developing ASD. Although there was definite radiologic degeneration in the ASD group, no significant difference was observed between the ASD and non-ASD groups in terms of the incidence of symptomatic disease.
authors.affiliation: Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Spine Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Sang-Soak
authors.initials: SS
authors.lastname: Ahn
authors.affiliation: Department of Neurosurgery, 21 Century Hospital, Ansan, Korea.
authors.forename: Wan-Soo
authors.initials: WS
authors.lastname: So
authors.affiliation: Department of Neurosurgery, 21 Century Hospital, Ansan, Korea.
authors.forename: Min-Geun
authors.initials: MG
authors.lastname: Ku
authors.affiliation: Department of Radiology, Dong-A University Medical Center, Busan, Korea.
authors.forename: Sang-Hyeon
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Radiology, Dong-A University Medical Center, Busan, Korea.
authors.forename: Dong-Won
authors.initials: DW
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, The Armed Forces Capital Hospital, Seongnam, Korea.
authors.forename: Byung-Hun
authors.initials: BH
authors.lastname: Lee
keywords: Adjacent segment degeneration; Anterior; Cervical; Fusion; Spondylosis