title: Factors determining cervical spine sagittal balance in asymptomatic adults: correlation with spinopelvic balance and thoracic inlet alignment.
abstract: BACKGROUND
  Based on the previous studies, cervical lordosis (CL) is a parameter influenced by thoracic kyphosis (TK); however, the correlations still remain unclear. Few studies have analyzed the correlations between the cervical spine lordosis and global spinopelvic balance. To date, there has been no study focused on the factors determining cervical spine sagittal balance.
  
  
  METHODS
  Seventy-seven asymptomatic volunteers without the history of symptoms related to whole spine.
  
  
  METHODS
  Statistical significance of correlations of radiographic parameters on cervical spine and whole-spine standing lateral radiograph.
  
  
  OBJECTIVE
  To analyze the factors determining cervical spine sagittal balance, including global spinopelvic balance and thoracic inlet (TI) alignment in asymptomatic adults.
  
  
  METHODS
  A prospective radiographic study.
  
  
  METHODS
  Cervical and whole-spine standing lateral radiographs were taken to analyze the following parameters: spinopelvic parameters pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), and TK; TI parameters thoracic inlet angle (TIA) and T1 slope; and cervical spine parameters C0-C2, C2-C7, and C0-C7 angles and cervical tilting. Statistical analysis was performed using the Pearson correlation coefficients and multiple regression analysis.
  
  
  RESULTS
  All the parameters showed a normal distribution. There was a significant sequential linkage between PI and SS (r=0.653), SS and LL (r=0.807), LL and TK (r=-0.516), and TK and C0-C7 angle (r=-0.322). There was a significant relationship between TK and T1 slope (r=0.351) but no significant relationship between TK and TIA. There were significant sequential relationships between TIA and T1 slope (r=0.694), T1 slope and C2-C7 angle (r=-0.624), and C2-C7 and C0-C2 angles (r=-0.547). T1 slope was the only parameter that demonstrated a significant correlation with both SP and TI parameters. A linear regression model showed that T1 slope had a stronger relationship with TIA (r=0.694) than TK (r=0.351).
  
  
  CONCLUSIONS
  T1 slope was a key factor determining cervical spine sagittal balance. Both spinopelvic balance and TI alignment have a significant influence on cervical spine sagittal balance via T1 slope, but TIA had a stronger effect than TK. An individual with large T1 slope required large CL to preserve physiologic sagittal balance of the cervical spine. The results of the present study could serve as baseline data for further studies on the cervical spine sagittal balance in various clinical conditions including the surgical reconstruction of lordosis.
authors.affiliation: Department of Orthopedic Surgery, Kyung Hee University Hospital at Gangdong, #149, Sangil-dong, Gangdong-gu, Seoul 134-727, Korea. Electronic address: shl6@khu.ac.kr.
authors.forename: Sang-Hun
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Kei Myung University, #56 Dalseong-RO, Jung-Gu, Daegu, Korea 700-712.
authors.forename: Eun-Seok
authors.initials: ES
authors.lastname: Son
authors.affiliation: Hallym University, Chuncheon Sacred Heart Hospital, #153, Gyo-dong, Chuncheon, Gangwon-do 200-060, Korea.
authors.forename: Eun-Min
authors.initials: EM
authors.lastname: Seo
authors.affiliation: Department of Orthopedic Surgery, Kyung Hee University Hospital at Gangdong, #149, Sangil-dong, Gangdong-gu, Seoul 134-727, Korea.
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Suk
authors.affiliation: Department of Orthopedic Surgery, Kyung Hee University Hospital at Gangdong, #149, Sangil-dong, Gangdong-gu, Seoul 134-727, Korea.
authors.forename: Ki-Tack
authors.initials: KT
authors.lastname: Kim
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008141:Lordosis / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011859:Radiography; D012447:Sacrum / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Cervical spine sagittal balance; Spinopelvic balance; T1 slope; Thoracic inlet alignment