A self-drilling anchor for use in a friable material or a semi-rigid material comprises a body having an axis, an axial bore adapted to receive a fastener, a proximal end, a drilling end, a proximal portion adjacent the proximal end having high threading having a crest diameter for engaging the friable or semi-rigid material, and a drilling portion adjacent the drilling end, an additional thread proximate the proximal end, the additional thread continuing between turns of the high threading, and a head at the proximal end having an outer diameter that is smaller than the crest diameter. The anchor additional thread is configured to engage either the friable material or, additionally, to firmly engage the semi-rigid material.