title: Intraobserver and interobserver reliability of measures of cervical sagittal rotation.
abstract: BACKGROUND
  Diagnosis and treatment decisions of cervical instability are made, in part, based on the clinician's assessment of sagittal rotation on flexion and extension radiographs. The objective of this study is to evaluate the intraobserver and interobserver reliability of three measurement techniques in assessing cervical sagittal rotation.
  
  
  METHODS
  Fifty lateral radiographs of patients with single-level cervical degenerative disc were selected and measured on two separate occasions by three spine surgeons using three different measurement techniques. Cervical sagittal rotation was measured using three different techniques.
  
  
  RESULTS
  Intraclass correlation coefficients were most consistent for Method 2 (ICC 0.93-0.96) followed by Method 1 (ICC 0.88-0.91) and Method 3 (ICC 0.81-0.87). Intraobserver agreement (% of repeated measures within 0.5° of the original measurement) ranged between 76% and 96% for all techniques, with Method 2 showing the best agreement (92%-96%). Paired comparisons between observers varied considerably with interobserver reliability correlation coefficients ranging from 0.54 to 0.89. Method 2 showed the highest interobserver reliability coefficient (0.82, range 0.73-0.88). Method 2 was also more reliable for the classification of "instability". Intraobserver percent agreements ranged from 94 to 98% for Method 2 versus 84% to 90% for Method 1 and 78% to 86% for Method 3, while interobserver percent agreements ranged from 90% to 98% for Method 2 versus 86% to 94% for Method 1 and 74% to 84% for Method 3.
  
  
  CONCLUSIONS
  Method 2 (measuring the angle from the inferior endplate of the vertebra above the degenerative disc and the inferior endplate of the vertebra below the degenerative disc) showed the best intraobserver and interobserver reliability overall in assessing cervical sagittal rotation.
authors.forename: Sheng-Dan
authors.initials: SD
authors.lastname: Jiang
authors.forename: Jiang-Wei
authors.initials: JW
authors.lastname: Chen
authors.forename: Yue-Hua
authors.initials: YH
authors.lastname: Yang
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092, China. chenxdmd@163.com.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Chen
authors.forename: Lei-Sheng
authors.initials: LS
authors.lastname: Jiang
mesh_terms: D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods / Q000592:standards*; D015203:Reproducibility of Results; D012399:Rotation; D066231:Surgeons / Q000592:standards*