Pedicle dimensions of T3 (A), T8 (B), and L4 (C) vertebrae. Vertical diameter (c) increases from 0.7 to 1.5 cm, horizontal diameter (d) increases from 0.7 to 1.6 cm with minimum of 0.5 cm in T5. Direction is almost sagittal from T4 to L4. Angle (e) seldom extends beyond 10 degrees. More proximally, direction is more oblique: T1 = 36 degrees, T2 = 34 degrees, T3 = 23 degrees. L5 is oblique (30 degrees) but is large and easy to drill.