Magnetic resonance imaging study of acetabular morphology in developmental dysplasia of the hip.

Acetabular morphology in developmental dysplasia of the hip (DDH) can be delineated by magnetic resonance imaging (MRI) more accurately than by previously available imaging methods. We describe the acetabular morphology observed in 10 girls and one boy aged < 3 years with untreated DDH. The bony pathology was iliac bone widening with lateral drift of the superior and posterior portions of the acetabular floor (extrusio acetabulae), loss of sphericity, and diminished aperture of the acetabulum. The cartilage changes were a distortion and overgrowth of the acetabular cartilage, including labrum, and a convex appearance of the posterior portion of the acetabular cartilage.