Unilateral congenital hip dislocation with contralateral avascular necrosis.

Seventy-six children with previoulsy undiagnosed unilateral congenital dislocation of the hip were examined after 2 years of age. Nine had radiologic signs of dislocation on one side and avascular necrosis of the contralateral femoral head. The incidence of necrosis on the contralateral side in older children with unilateral dislocation is much higher than among the normal population. The cause of these occurrences of aseptic necrosis is not known but could be associated with abnormal stress on an undislocated femoral head from dysfunction of a contralateral unstable dislocated femoral head.