[Technical errors in the application of Graf's hip sonography method].
OBJECTIVE
The aim of the study is to point out possible examination errors because of a titled transducer, and to analyse their sources.


METHODS
The results obtained by experienced examiners using the correct examination technique were compared to results obtained under defined deviations from the standard. With the use of a computer model the course taken by the ultrasound waves in the neonatal hip was simulated and the sonographic image reconstructed.


RESULTS
Twisted as well as tilted positions of the transducer lead to significant errors in alpha, the acetabular roof angle. This is in accordance with the computer model predictions. Caudo-cranially tilted probes lead to false-positive, therapeutically relevant incorrect diagnoses.


CONCLUSIONS
The computer simulation predicts a high degree of accuracy of hip sonography in Graf's technique under standard conditions. The effectiveness of sonographic infant hip screening largely depends on the ability to adhere to the standardized approach, minimizing possible errors. A mechanical transducer guide prevents tilting errors by reducing the degrees of variability in positioning the transducer.
Institut für Medizinische Physik und Biophysik, Graz, Austria. wolfram.mueller@kfunigraz.ac.at
W
W
Müller
K
K
Lercher
T T
TT
DeVaney
F
F
Giner
R
R
Graf
D016477:Artifacts; D003198:Computer Simulation; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging*; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007231:Infant, Newborn; D008403:Mass Screening; D011187:Posture; D015203:Reproducibility of Results; D014463:Ultrasonography