A bone fixation element consisting of a hollow member having a wall, a plurality of perforations locating in the wall, a front end which is suited for insertion into the bone, a rear end, and a longitudinal axis. The stiffness of the hollow member may vary along its longitudinal axis from the rear end to the front end. Changes in the porosity and/or the thickness of the wall of the bone fixation element may result in changes in stiffness of the bone fixation element. An increase in porosity and/or decrease in thickness may result in a decrease in stiffness, and a decrease in porosity and/or increase in thickness may result in an increase in stiffness.