[The Graf standard plane--a "standard sector"? Ultrasound studies of anatomic preparations of hip acetabula of infants].
OBJECTIVE
To answer the question as to which ultrasound sections, related to the hip joint plane, lead to pictures of the so-called "standard-plan" of Graf, anatomic preparations of infant hips were examined by ultrasound.


METHODS
10 anatomic preparations of infant hips were fixed in a support which allows an exact positioning of the ultrasound plane related to the acetabular inlet plane in a water bath. The joints were examined while changing the relative position in steps of 10 degrees. The ultrasound images were documented by video-print and the alpha-angles were measured if the criterias of the standard plane were fulfilled.


RESULTS
In order to obtain images that are analysable by the method of Graf, the ultrasound beam has to intersect with the acetabular inlet plane at defined angles. The acetabular notch has to be anteriorly rotated from the ultrasound beam plane by at least 20 degrees. Beam entry within a 50-degree sector posterior to the perpendicular on the inlet plane gave analysable images. The alpha-angles were markedly affected by coronal-plane transducer tilt. Caudad tilts were associate with lower values, a fact that should be borne in mind in clinical ultrasound investigations.


CONCLUSIONS
The "standard plane" of graf is a "standard sector", which can be defined in all three dimensions. The relations between the acetabular inlet plane and the sonographic beam are described exactly for the first time. The results are important because of their influence on clinical ultrasound examinations.
Falliner
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Orthopädische Universitätsklinik Kiel.
D000077:Acetabulum / Q000000981:diagnostic imaging*; D004867:Equipment Design; D005260:Female; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology; D012016:Reference Values; D014463:Ultrasonography / Q000295:instrumentation*