title: Postoperative Increase in Occiput-C2 Angle Negatively Impacts Subaxial Lordosis after Occipito-Upper Cervical Posterior Fusion Surgery.
abstract: METHODS
  Retrospective case series.
  
  
  OBJECTIVE
  To elucidate the impact of postoperative occiput-C2 (O-C2) angle change on subaxial cervical alignment.
  
  
  BACKGROUND
  In the case of occipito-upper cervical fixation surgery, it is recommended that the O-C2 angle should be set larger than the preoperative value postoperatively.
  
  
  METHODS
  The present study included 17 patients who underwent occipito-upper cervical spine (above C4) posterior fixation surgery for atlantoaxial subluxation of various etiologies. Plain lateral cervical radiographs in a neutral position at standing were obtained and the O-C2 angle and subaxial lordosis angle (the angle between the endplates of the lowest instrumented vertebra (LIV) and C7 vertebrae) were measured preoperatively and postoperatively soon after surgery and ambulation and at the final follow-up visit.
  
  
  RESULTS
  There was a significant negative correlation between the average postoperative alteration of O-C2 angle (DO-C2) and the average postoperative alteration of subaxial lordosis angle (Dsubaxial lordosis angle) (r=-0.47, p=0.03).
  
  
  CONCLUSIONS
  There was a negative correlation between DO-C2 and Dsubaxial lordosis angles. This suggests that decrease of mid-to lower-cervical lordosis acts as a compensatory mechanism for lordotic correction between the occiput and C2. In occipito-cervical fusion surgery, care must be taken to avoid excessive O-C2 angle correction because it might induce mid-to-lower cervical compensatory decrease of lordosis.
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Taigo
authors: T
authors: Inada
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Takeo
authors: T
authors: Furuya
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Koshiro
authors: K
authors: Kamiya
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Mitsutoshi
authors: M
authors: Ota
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Satoshi
authors: S
authors: Maki
authors: Department of Bioenvironmental Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Takane
authors: T
authors: Suzuki
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Kazuhisa
authors: K
authors: Takahashi
authors: Department of Orthopedic Surgery, University of Tsukuba, Tsukuba, Japan.
authors: Masashi
authors: M
authors: Yamazaki
authors: Department of Orthopedic Surgery, Teikyo University, Chiba Medical Center, Ichihara, Japan.
authors: Masaaki
authors: M
authors: Aramomi
authors: Department of Orthopedic Surgery, Teikyo University, Chiba Medical Center, Ichihara, Japan.
authors: Chikato
authors: C
authors: Mannoji
authors: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Masao
authors: M
authors: Koda
keywords: Cervical spine; Occipital bone; Spinal curvatures; Spinal fusion