Presentation
Clinical DDH
Patient Data
Pelvis and bilateral Hip x-ray.
No imaging is available for comparison.
Mild coxa valga deformity of bilateral femora is demonstrated with mild coxa magna. There is mild protrusio, the inner margin of the acetabulum passing deep to the ilioischial line. Apparent crossover sign of the acetabulum bilaterally is likely due to pelvic tilt since the distance between the symphysis pubis and coccyx is greater than 3 cm. Lucency at the junction of the right femoral head and neck laterally may be secondary to impaction (impingement).
Case Discussion
Apparent acetabular retroversion occurs when there is pelvic tilt. AP pelvic film should be taken with a film-tube distance of 1.2 m. Distance between the tip of the coccyx and symphysis pubis should be between 1 and 3 cm. I this case it is greater than 3 cm indicating pelvic tilt. This causes apparent cross over between the anterior and posterior margins of the acetabulum.
In this case the medial margin of the acetabulum passes medial to the ilio-ischial line although the center edge angle is normal indicating mild protrusio.
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