Fig. 2

a The new tool for removal of autologous bone from the femoral head consists of the trephine with inboard cutting edges, the guiding device with a convex tip (introducer) and the handle containing a 3.2 mm canal for further guidance during the following introduction with hammer blows. b After cautious reaming to open the cortical bone, the trephine is introduced into the bone by means of a guidance device with a convex tip (introducer). When the trephine is in place, the introducer is removed and the proximal handle is attached. When the instrument has achieved its final position, it can be turned to cut respectively break the cylinder with the inside cutting edges