Femoral head position: Concentric reduction vs. eccentric reduction.

A. Medial joint space distance is defined as the distance between the triradiate cartilage and femoral capital epiphysis. If the medial joint space width is 3 mm or less, it is defined as a concentric reduction. B. Eccentric reduction of the left DDH in a 17-month-old girl. Medial joint space distance is 6 mm. Note the dysplastic left acetabulum and no visible ossification center of the left proximal femoral epiphysis.