Head-Shaft Angle (HSA) and Grade of Slipped Capital Femoral Epiphysitis (SCFE)

Analysis: X-ray of the hip in a frog-leg position with the hip flexed to 90 degrees

Lines:

(1) line connecting the superior and inferior margins of the epiphysis for the femoral head (epiphyseal line)

(2) line through the central long axis of the femoral shaft (femoral long axis)

(3) line taken perpendicular to the midpoint of the epiphyseal line through the femoral long axis

Line 3 is normally the line through the central long axis of the femoral head and neck.

The head-shaft angle (HSA) is the angle between the femoral long axis (line 2) and the line 3.

If there is no slip then the angle is 0°.