[Errors in diagnosis of children's hip joint using conventional X-ray technique (author's transl)].

X-rays of the hip joints in anteroposterior direction in adults and children should be made with the leg in the middle rotation position. But the middle position is different in children than in adults. In adults the patella should be facing directly upwards because from this position the leg can be rotated medially. In children of 3 to 8 years (or older), however, the leg can be rotated much further medially than it can be laterally. Thus in children the "middle rotation" position is one in which the leg is positioned more medially than would be the case with adults; the ideal position for X-ray is the one in which the leg can be rotated to the same extend medially and laterally. X-rays must be performed in this manner to prevent errors in judging children's hip joints. Examples of wrong diagnosis on the basis of conventional X-rays are demonstrated. Only with X-rays in the correct middle position can we arrive at reliable assessments of the hip.U