Thirty-two patients (thirty-seven hips) who had a so-called
acute-on-chronic or chronic slipped capital femoral epiphysis were treated
with traction for relief of symptoms and then with immobilization in a
spica cast for eight to sixteen weeks. The disappearance on radiographs of
a metaphyseal juxtaphyseal radiolucency, rather than closure of the physis,
was used as the criterion for removing the cast. In one (3 per cent) of the
thirty-seven hips, the slip progressed; possibly this could have been
prevented by keeping the cast on for a longer period of time. Narrowing of
the cartilage space was seen after treatment in a cast in seven (19 per
cent) of the thirty-seven hips. In five of these seven hips, this was true
chondrolysis; in one, the diagnosis of chondrolysis had been apparent
before treatment. Avascular necrosis did not develop as a result of
treatment in any patient. Treatment in a spica cast should be considered as
an alternative for patients who have an acute-on-chronic or chronic slipped
capital femoral epiphysis.