A trocar for preparing pilot holes, tunnels and other spaces within bone includes a piercing tip, a cutting element, and an expansion element for expanding the cutting element radially outwardly with respect to a longitudinal axis of the trocar. The cutting element includes one or more cutting blades. The trocar also includes a hollow shaft. The hollow shaft can include one or more apertures axially and radially aligned with the one or more cutting blades. The expansion element can include an activation rod housed inside the hollow shaft. The one or more cutting blades can be in the form of two opposed cutting blades separated by a gap, the two opposed cutting blades being radially displaceable with respect to the longitudinal axis. The activation rod can include a wedge that partially enters the gap between the two opposed cutting blades to displace the cutting blades to an expanded position.