Slipped capital femoral epiphysis: assessment of epiphyseal displacement and angulation.

Nineteen hips with slipped capital femoral epiphysis underwent assessment of the severity of epiphyseal displacement on anteroposterior and lateral roentgenograms and by computerized tomography. The head-shaft angle, the percentage of maximal epiphyseal displacement, and the computed tomographic head-neck angle were determined. The head-shaft angle showed great variability when compared with the percentage of epiphyseal displacement and with the head-neck angle. The percentage of epiphyseal displacement showed less variability when compared with the computerized tomographic head-neck angle; however, the range of error was still significant. These data suggest that the computerized tomographic measurement of degree of slip is more accurate than previously described techniques. We believe that the computerized tomographic measurement of head-neck angle achieves greater accuracy and therefore reproducibility by virtue of a decrease in position dependency. This measurement may be indicated as a reproducible standard for assessing slip severity in the horizontal plane.