Abstract
PurposeThe 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.Materials and methodsTwenty-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.ResultsWe 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).ConclusionOur 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.
Highlights
A relatively wide range of incidence rates of developmental dysplasia of the hip (DDH) is reported among the literature
Our findings show that the standardized plane defined by Graf’s criteria allows notable inclinations of the transducer positions
A standardized sonographic hip screening method like the sonographic method according to Graf et al is expected to increase the reliability and comparability of given incidence rates [1]
Summary
A relatively wide range of incidence rates of developmental dysplasia of the hip (DDH) is reported among the literature. A standardized sonographic hip screening method like the sonographic method according to Graf et al is expected to increase the reliability and comparability of given incidence rates [1]. Several studies were conducted and proved Graf’s broadly used sonographic screening method for DDH to be reliable and reproducible [2,3,4]. Previous studies focused on the method of measurement on given sonographic images, whereas the process of acquisition of sonographic images was not examined. Considering the clinical importance of Graf’s method in established national screening programs for DDH in many European countries, it is interesting that an essential issue like the link of transducer inclinations to measurement results was not examined before [5, 6]
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