SLIPPED CAPITAL FEMORAL EPIPHYSIS - INCIDENCE AND CLINICAL-ASSESSMENTOF PHYSEAL INSTABILITY

In an unselected series of 55 cases of slipped capital femoral epiphys is (SCFE) we observed an incidence of 25% of epiphyseal reduction, mos tly unintentional, Reduction indicated physeal instability and was ass ociated with an effusion, detected by sonography on admission, and ina bility to bear weight. The true prevalence of instability may be highe r since an effusion was noted in 33 cases (60%) on the initial sonogra phic assessment, Serial radiographs showed reduction in 12 (22%), with an average change of 15.1 degrees in the head-neck angle, Serial sono graphy showed reduction in 7 out of 20 cases (35%), with an average ch ange of 3.7 mm in displacement, In two cases reduction was seen on son ography but not on radiography. Of the hips which showed subsequent re duction, 12 had had a bone scan on admission; three showed initial epi physeal avascularity but only one progressed to symptomatic avascular necrosis, All stable hips had normal epiphyseal vascularity on the ini tial bone scan, This indicates the importance of injury from the initi al displacement in causing avascular necrosis, rather than effusion, v ascular compromise or iatrogenic injury from gentle repositioning. Phy seal instability in SCFE is common and should be assessed clinically o n admission, It is indicated by joint effusion or inability to bear we ight, A slip is very unlikely to be unstable in a child able to bear w eight and with no sonographic effusion.