(a) Pelvis CT scan of a patient with acetabular fracture who has a retroacetabular angle of 42 degrees and a retroacetabular tangent length of 32 mm. The contralateral normal acetabulum is used for preoperative angle assessment. The medialization distances and correspond to allowance angles and . (b) The increment in the magnitude of the allowance angle in relation to the medialization distance for the same patient is graphically demonstrated by a curve plotted using a computer program for preoperative planning.