title: Differential segmental motion contribution of single- and two-level anterior cervical discectomy and fusion.
abstract: OBJECTIVE
  To determine and compare the biomechanical effects of single- and two-level anterior cervical decompression and fusion (ACDF) on the re-distribution of the segmental contribution to total cervical range of motion (ROM) in a prospective longitudinal design.
  
  
  METHODS
  Fifty-one patients undergoing either a single- or two-level ACDF due to cervical disc disease were recruited. Functional radiographs were taken preoperatively and then at 3, 6 and 12-month follow-ups. Global ROM of C2-C7, ROM of the treated functional spinal unit (FSU) and the superior and inferior segmental ROMs were then measured. The relative contribution from the FSU and each of the adjacent segments to total cervical ROM were compared pre- and post-operatively within and between the two groups at each of the time points.
  
  
  RESULTS
  Single-level ACDF patients demonstrated a significantly greater total cervical ROM at 6 and 12 months compared with the two-level ACDF group (p = 0.021 and 0.045, respectively). A significantly greater contribution from the FSU to the total ROM was found at 3 months in the two-level ACDF group (p = 0.016), but the greater contribution shifted to the superior adjacent segment at 6 and 12 months (p = 0.025 and 0.046). The two-level ACDF group did not demonstrate a significant difference at 3 months (p = 0.087), but a significant increase in contribution was found at 6 and 12 months (p < 0.01).
  
  
  CONCLUSIONS
  Single-level ACDF maintains and restores a more physiological re-distribution of segmental contribution of ROM compared with two-level ACDF, which required longer time to achieve stable FSU immobilization and coupled with significantly increased superior segment contribution.
authors: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan.|Institute of Biomedical Engineering, Department of Mechanical Engineering, College of Medicine and College of Engineering, National Taiwan University, 602 Jen-Su Hall, 1 Section 4, Roosevelt Road, Taipei, 10617, ROC, Taiwan.
authors: Andy
authors: A
authors: Chien
authors: Division of Neurosurgery, Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan. dmlai@ntu.edu.tw.
authors: Dar-Ming
authors: DM
authors: Lai
authors: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors: Shwu-Fen
authors: SF
authors: Wang
authors: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, Chang Gung University, Taoyuan, Taiwan.
authors: Chih-Hsiu
authors: CH
authors: Cheng
authors: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors: Wei-Li
authors: WL
authors: Hsu
authors: Institute of Biomedical Engineering, Department of Mechanical Engineering, College of Medicine and College of Engineering, National Taiwan University, 602 Jen-Su Hall, 1 Section 4, Roosevelt Road, Taipei, 10617, ROC, Taiwan. jlwang@ntu.edu.tw.
authors: Jaw-Lin
authors: JL
authors: Wang
mesh_terms: D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods*; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000379:methods*
keywords: Anterior cervical discectomy and fusion; Cervical kinematics; Decompression surgery; Range of motion; Segmental contribution