title: Measurement considerations on examiner-dependent factors in the ultrasound assessment of developmental dysplasia of the hip.
abstract: The standardized sonographic hip screening according to Graf has increased reliability and comparability of measurements in the screening of developmental dysplasia of the hip (DDH). However, examiner dependent factors have been discussed to influence sonographic measurements. The objectives of this study were to examine the tolerance of the transducer positioning and to analyse the impact of transducer inclinations on Graf's hip grading system.
  
  
  
  Twenty-four hips in consecutive newborns were screened sonographically in combination with an optoelectronic motion capture system to trace transducer positions in space. Subsequently five defined inclinations of the transducer relative to Graf's neutral transducer position were analysed, giving a total of 144 sonographic images.
  
  
  
  We found a permissible transducer inclination in the axial plane of 8.8° to anterior and 8.1° to posterior. In the frontal plane we found a permissible inclination of 15.4° to caudal and 7.2° to cranial. The impact on the α-angle was significant for posterior-cranial (p < 0.001), cranial (p = 0.009), and caudal (p < 0.001) inclined transducer positions. The effect on the results according to Graf's grading system was significant for the caudal inclination of the transducer position (p < 0.001).
  
  
  
  Our findings show that the standardized plane defined by Graf's criteria allows notable inclinations of the transducer positions. Transducer inclinations show an impact on measurement results, which are clinically relevant. Those effects cannot be ruled out using Graf's ultrasound criteria alone. The examiner should pay attention to avoid transducer inclinations in the frontal plane and a combination of posterior and cranial inclination.
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria. alexander.kolb@meduniwien.ac.at.
authors.forename: Alexander
authors.identifier: 0000-0001-7869-2586
authors.initials: A
authors.lastname: Kolb
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria.
authors.forename: Emir
authors.initials: E
authors.lastname: Benca
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Willegger
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria.
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Puchner
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Windhager
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria.
authors.forename: Catharina
authors.initials: C
authors.lastname: Chiari
mesh_terms: D005260:Female; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging*; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015203:Reproducibility of Results; D014159:Transducers; D014463:Ultrasonography / Q000379:methods*
keywords: Developmental Dysplasia of the Hip (DDH); Hip sonography