Fig. (1) Canal shape and proximal femur. Canal shape was classified by canal flare index, defined as ratio of the intracortical width of the femur at a point 20 mm proximal to the lesser trochanter and at canal isthmus. (a): stovepipe (canal flare index < 3.0), (b): normal (3.0-4.7), (c) champagne-flute (4.7-6.5).