The Pathology of Slipped Upper Femoral Epiphysis

The weakest part ofthe epiphysial plate is the layer ofcartilage cells nearest the metaphysis. If the overlying periosteum is incised, a separation through this layer is easily produced (Haas 1917). Even if it is conceded, as shown experimentally by Harris (1950), that, in rats treated by growth hormone, broadening of this layer can diminish the cohesion of epiphysis and metaphysis, the resistance to slipping of the upper femoral epiphysis offered by a strong. intact periosteum is nevertheless great. Its rupture, necessary before slipping can take place, is likely to produce symptoms more acute than are usual in the case with gradual onset. It is too easily assumed that slipping is the first recognisable change in position of the femoral head. From a study of lateral radiographs of slipped epiphyses, I have been impressed by the frequency with which the back of the femoral neck is materially shorter than the front (Fig. 1).