A retrospective study involving 276 patients with 319 congenitally
dislocated hips was undertaken to assess whether premanipulation fraction
prevents avascular necrosis. Roentgenographic criteria were utilized and
only cases of frank dislocation unassociated with other disorders were
included. It was found that in a child less than one year old,
premanipulation traction of twenty-one days or more substantially reduces
the incidence of avascular necrosis. For the child more than a year old,
however, the prognosis is not as good, even if premanipulation traction is
prescribed for twenty-one days or more. We found a 14 per cent incidence of
avascular necrosis in children less than three months old and suggest that
the cartilaginous femoral head prior to the appearance of the ossific
nucleus is particularly vulnerable to vascular injury.