Postreduction computed tomography in developmental dislocation of the hip: part II: predictive value for outcome.

Computed tomographic (CT) scans were performed after closed reduction of 68 dislocated hips in 53 infants in spica casts with developmental hip dislocation (DDH). Ten measurements were made on the CT scans including acetabular indices and anteversion, hip-abduction angle, lateral and posterior displacement of the femur from the acetabulum, and femoral displacement from a modified Shenton's line drawn from the pubic rami. By using analysis of variance, the correlation of each variable with outcome after reduction was determined, including the development of avascular necrosis or the need for further surgery because of residual dysplasia. None of the variables was predictive of the outcome of persistent hip dysplasia. The subsequent development of avascular necrosis was statistically associated with hip-abduction angles >55 degrees as measured on postreduction CT scans, with 20% of the involved hips developing avascular necrosis on subsequent follow-up.