title: Influence of variation in semiflexed knee positioning during image acquisition on separate quantitative radiographic parameters of osteoarthritis, measured by Knee Images Digital Analysis.
abstract: OBJECTIVE
  The clinical application of quantitative measurement of separate radiographic parameters of knee osteoarthritis (OA) might be hampered by a lack of reproducible semiflexed joint positioning during acquisition of radiographs. The influence of systematic variations in knee positioning on measurement of separate quantitative radiographic parameters was studied.
  
  
  METHODS
  Five components of knee position during radiographic acquisition (beam height, lower and upper leg extension, internal rotation, and lateral shift) were systematically varied within a clinically relevant range, using three cadaver legs. The influence of these variations on the measurement of the separate quantitative radiographic parameters by Knee Images Digital Analysis (KIDA) was evaluated. Significant changes were validated in vivo. Changes were compared with differences during 2-year follow-up in a radiographic progression cohort of early OA.
  
  
  RESULTS
  Systematic variation in upper and lower leg extension induced changes in the measurement of joint space width (JSW). Lower leg extension also influenced osteophyte area and eminence height measurement. Also bone density measurement was influenced by variation in all five position components. Variations were of clinical relevance compared with 2-year differences in knees with radiographic progression, and were confirmed in vivo.
  
  
  CONCLUSIONS
  Variations in semiflexed knee positioning, which are considered to occur easily during image acquisition in trials and clinical practice despite standardization, are of significant influence on the quantitative measurement of most separate radiographic parameters of OA using KIDA. The additional value of quantitative measurement might improve significantly by better standardization during radiographic acquisition; with radiography still being the gold standard for structure-modification in OA.
authors.affiliation: Rheumatology & Clinical Immunology, University Medical Center Utrecht, The Netherlands.
authors.forename: M B
authors.initials: MB
authors.lastname: Kinds
authors.forename: K L
authors.initials: KL
authors.lastname: Vincken
authors.forename: T N
authors.initials: TN
authors.lastname: Hoppinga
authors.forename: R L A W
authors.initials: RL
authors.lastname: Bleys
authors.forename: M A
authors.initials: MA
authors.lastname: Viergever
authors.forename: A C A
authors.initials: AC
authors.lastname: Marijnissen
authors.forename: P M J
authors.initials: PM
authors.lastname: Welsing
authors.forename: F P J G
authors.initials: FP
authors.lastname: Lafeber
mesh_terms: D000328:Adult; D000368:Aged; D015519:Bone Density / Q000502:physiology; D002102:Cadaver; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D054850:Osteophyte / Q000000981:diagnostic imaging; D056888:Patient Positioning; D011859:Radiography