Does unstable slipped capital femoral epiphysis require urgent stabilization?

Controversy exists regarding the role of early reduction and stabilization in the management of unstable slipped capital femoral epiphysis. It seems logical that early reduction and stabilization of an unstable slip might preserve the remaining blood supply to the epiphysis and reduce the incidence of avascular necrosis. Some studies have indeed shown lower rates of avascular necrosis following early reduction and stabilization, but others have shown the contrary. To try to resolve this disagreement, we conducted a retrospective review of slipped capital femoral epiphysis treated in Alder Hey Hospital over a 4-year period. We reviewed 117 consecutive slips in 82 children (43 boys and 39 girls, mean age 12 years), treated by internal fixation from 1998 to 2002. Mean follow-up was 18 months (range, 12-48 months). Sixteen cases (19%) were unstable at presentation. Avascular necrosis developed in eight of these, of which all but one were treated between 24 and 72 h after symptom onset. The eight unstable slips that did not develop avascular necrosis were treated either within 24 h (five children) or at 8 days (three children). Avascular necrosis did not develop in any of the stable slips. We recommend immediate stabilization of unstable slips presenting within 24 h. If this is not possible because of delayed presentation, we recommend deferring definitive management until at least a week has elapsed. This study supports the notion that there is a definite period of time during which medical intervention increases the risk of avascular necrosis and should be actively avoided. We term this period 'the unsafe window'.