Secondary avascular necrosis after treatment for congenital dislocation of the hip.

We made a radiographic study of 104 unilateral congenital dislocations of the hip (CDH) that had an average age of 12 months (range 4-24), were treated with the same therapeutic protocol, and had an average six years follow-up (range 3-13). Radiographic changes were evident in the proximal femoral epiphysis in 57 hips (55%). In 7 (7%) the changes consisted of central osteoporosis with a cystic aspect, without metaphyseal or physeal changes, and had a normal end result without sequelae. This group was classified as type I. Fifty hips (48%) that were type II showed epiphyseal changes consisting of trabecular rarefaction with osteoporosis and irregular sclerosis, followed by a decrease of epiphyseal height and trabecular recovery. Forty-two hips (40%) were type IIA, with < 75% decrease in epiphyseal height with respect to the healthy side; five of these had a normal evolution, 35 had coxa magna and/or decrease of epiphyseal height, and only two cases had physeal lesion. In type IIB, hips, with > 75% decrease of epiphyseal height, 8 cases (8%) had a final physeal lesion.