title: Sequential alignment change of the cervical spine after anterior cervical discectomy and fusion in the lower cervical spine.
abstract: The cervical spine has a linear chain of correlation or reciprocal relationship regionally (within the cervical spine) and globally (head to whole spine). The purpose of this study was to assess the sequential alignment change of the regional and global cervical spine after two-level anterior cervical discectomy and fusion (ACDF) performed on the lower cervical spine.
  
  
  
  This study included 61 patients (mean age 56 ± 8.6 years; range 35-70 years) who underwent ACDF at C5-6-7 with a plate-cage construct and whose C-spine neutral lateral radiographs showed an identical degree of horizontal gaze (occipital slope) peri-operatively. We compared the change in cervical curvature from the occiput to C7 with the absolute value (slope angle) and relative value (between two different slopes). We also investigated the correlated change in multiple angular parameters according to the change in the occipital slope.
  
  
  
  The occipital slope was significantly correlated with the value of the C1-slope (r = 0.33) and C2- slope (r = 0.51). The value of the center of the sellar turcica-C7 sagittal vertical axis (St-SVA) was very closely related to the C1-slope (r = -0.83), C2-slope (r = -0.8), C2-7 angle (r = -0.43), and C2-5 angle (r = -0.46). The amount of angular change at the surgical level (C5-7A) was 5.8° (2.9° -> 8.5°), and the sum of the change in the C5-slope and C7-slope was 6° (3.1° + 2.9°). In general, the C2-5 angle decreased about 3°, in proportion to the upward inclination of C5-slope (3.1°), because the C2-slope was fixed. However, patients who showed improvement in cervical alignment (greatly increased C5-7 lordosis or greatly decreased St-SVA after surgery) often had upper cervical slope change (C1-s and C2-s).
  
  
  
  The ACDF procedure itself can induce regional slope change (C5-s and C7-s) directly at the surgical level and can also influence upper cervical slope change (C1-s and C2s) indirectly. Then the change in the upper cervical spine can induce a change in the St-CVA and spino-cranial angle (SCA).
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, 56, Dongsu-ro, Bupyeong-Gu, Incheon, 403-720, Republic of Korea.
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, 56, Dongsu-ro, Bupyeong-Gu, Incheon, 403-720, Republic of Korea. rhother@hanmail.net.
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, 56, Dongsu-ro, Bupyeong-Gu, Incheon, 403-720, Republic of Korea.
authors.forename: Doo Yong
authors.initials: DY
authors.lastname: Choi
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, 56, Dongsu-ro, Bupyeong-Gu, Incheon, 403-720, Republic of Korea.
authors.forename: Myoung Hoon
authors.initials: MH
authors.lastname: Shin
authors.affiliation: Department of Neurosurgery, St. Vincent Hospital, The Catholic University of Korea, Suwon, Republic of Korea.
authors.forename: Jae Taek
authors.initials: JT
authors.lastname: Hong
mesh_terms: D000328:Adult; D000368:Aged; D001860:Bone Plates; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D017586:Diskectomy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D011859:Radiography; D012189:Retrospective Studies; D012886:Skull / Q000000981:diagnostic imaging / Q000473:pathology; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome
keywords: Anterior cervical discectomy and fusion; Cervical spine curvature; Upper cervical spine segment
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