title: Radiographic quantification of dynamic hip screw migration.
abstract: OBJECTIVE
  This study aimed to propose a technique to quantify dynamic hip screw (DHS®) migration on serial anteroposterior (AP) radiographs by accounting for femoral rotation and flexion.
  
  
  METHODS
  Femoral rotation and flexion were estimated using radiographic projections of the DHS® plate thickness and length, respectively. The method accuracy was evaluated using a synthetic femur fixed with a DHS® and positioned at pre-defined rotation and flexion settings. Standardised measurements of DHS® migration were trigonometrically adjusted for femoral rotation and flexion, and compared with unadjusted estimates in 34 patients.
  
  
  RESULTS
  The mean difference between the estimated and true femoral rotation and flexion values was 1.3° (95% CI 0.9-1.7°) and -3.0° (95% CI - 4.2° to -1.9°), respectively. Adjusted measurements of DHS® migration were significantly larger than unadjusted measurements (p = 0.045).
  
  
  CONCLUSIONS
  The presented method allows quantification of DHS® migration with adequate bias correction due to femoral rotation and flexion.
authors.affiliation: AO Clinical Investigation and Documentation, AO Foundation, Duebendorf, Switzerland.
authors.forename: Laurent
authors.initials: L
authors.lastname: Audigé
authors.forename: Flurin
authors.initials: F
authors.lastname: Cagienard
authors.forename: Christoph Martin
authors.initials: CM
authors.lastname: Sprecher
authors.forename: Norbert
authors.initials: N
authors.lastname: Suhm
authors.forename: Marc Andreas
authors.initials: MA
authors.lastname: Müller
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D005260:Female; D005264:Femoral Fractures / Q000601:surgery*; D005269:Femur / Q000503:physiopathology; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging*; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012399:Rotation