Pathologic morphology of the acetabulum in paralytic and congenital hip instability.

The nature of acetabular deficiency in both congenital and paralytic hip instability was investigated by computed tomography (CT). Sixty-six hips in 35 children with paralytic or congenital hip instability underwent transpelvic CT. Two angles were defined: angle 1 is a function of anterior and angle 2 a function of posterior coverage. The sum of the two angles represented acetabular depth. Results showed anterior deficiency in cerebral palsy and congenital hip instability. An absolute acetabular deficiency as opposed to a torsional disorder was present.