title: Reliability of cervical lordosis measurement techniques on long-cassette radiographs.
abstract: Lateral radiographs are commonly used to assess cervical sagittal alignment. Three assessment methods have been described and are commonly utilized in clinical practice. These methods are described for perfect lateral cervical radiographs, however in everyday practice radiograph quality varies. The aim of this study was to compare the reliability and reproducibility of 3 cervical lordosis (CL) measurement methods.
  
  
  
  Forty-four standing lateral radiographs were randomly chosen from a lateral long-cassette radiograph database. Measurements of CL were performed with: Cobb method C2-C7 (CM), C2-C7 posterior tangent method (PTM), sum of posterior tangent method for each segment (SPTM). Three independent orthopaedic surgeons measured CL using the three methods on 44 lateral radiographs. One researcher used the three methods to measured CL three times at 4-week time intervals. Agreement between the methods as well as their intra- and interobserver reliability were tested and quantified by intraclass correlation coefficient (ICC) and median error for a single measurement (SEM). ICC of 0.75 or more reflected an excellent agreement/reliability. The results were compared with repeated ANOVA test, with p < 0.05 considered as significant.
  
  
  
  All methods revealed excellent intra- and interobserver reliability. Agreement (ICC, SEM) between three methods was (0.89°, 3.44°), between CM and SPTM was (0.82°, 4.42°), between CM and PTM was (0.80°, 4.80°) and between PTM and SPTM was (0.99°, 1.10°). Mean values CL for a CM, PTM, SPTM were 10.5° ± 13.9°, 17.5° ± 15.6° and 17.7° ± 15.9° (p < 0.0001), respectively. The significant difference was between CM vs PTM (p < 0.0001) and CM vs SPTM (p < 0.0001), but not between PTM vs SPTM (p > 0.05).
  
  
  
  All three methods appeared to be highly reliable. Although, high agreement between all measurement methods was shown, we do not recommend using Cobb measurement method interchangeably with PTM or SPTM within a single study as this could lead to error, whereas, such a comparison between tangent methods can be considered.
authors.affiliation: Department of Orthopaedic Surgery, University of Illinois at Chicago, 835 South Wolcott Ave, Room E-270, Chicago, IL, 60612, USA. mdpjanusz@gmail.com.|Department of Spine Disorders and Pediatric Orthopedics, University of Medical Sciences, Poznan, Poland. mdpjanusz@gmail.com.
authors.forename: Piotr
authors.initials: P
authors.lastname: Janusz
authors.affiliation: Department of Orthopaedics, Pediatric Orthopaedics and Traumatology, The Centre of Postgraduate Medical Education in Warsaw, Konarskiego 13, 05-400, Otwock, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Tyrakowski
authors.affiliation: Department of Orthopedics, General Hospital of Shenyang Military Area Command of Chinese PLA, Shenyang, 110016, People's Republic of China.
authors.forename: Hailong
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Orthopaedic Surgery, University of Illinois at Chicago, 835 South Wolcott Ave, Room E-270, Chicago, IL, 60612, USA.
authors.forename: Kris
authors.initials: K
authors.lastname: Siemionow
mesh_terms: D000293:Adolescent; D000328:Adult; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008141:Lordosis / Q000000981:diagnostic imaging*; D008297:Male; D011859:Radiography / Q000379:methods / Q000592:standards; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Cervical lordosis; Cervical lordosis measurement; Cobb method; Harrison method