Thread design for bone screw

An implant device for engagement with a bone of a subject, said implant device comprising a distal end, a proximal end, a central shaft extending therebetween and a longitudinal central axis;

• said implant device further including a helical thread portion extending circumferentially about said central shaft and extending in a direction from the distal end of the implant device and towards the proximal end thereof, and a root at the base of the helical thread portion adjacent the central shaft of the of the implant device, said helical thread portion in cross section including:
• a leading edge and a trailing edge, both of which extend at least radially outwardly from the central shaft and define the thread portion therebetween, whereby a root of the thread portion is defined therebetween in a direction of the longitudinal central axis of the implant device;
• a crest portion disposed between the leading edge and the trailing edge and wherein said crest portion forms a radially outward portion of the thread portion, and wherein, the crest portion provides an engagement surface for abutment and engagement with bone of a subject radially disposed at said thread portion, the crest portion has a greater longitudinal length than that of the root in the direction of the longitudinal central axis of the implant device;
• wherein said leading edge faces in a direction at least towards the distal end of the implant device, and wherein said trailing edge faces at least in a direction towards the proximal end of the implant device;
• wherein a portion of the leading edge extends in a direction towards the distal end of the implant device further than the most distal portion of the root of the thread portion and wherein the distance in the longitudinal direction from the most proximal portion of the root to the most distal portion of the leading edge is greater than the longitudinal length of the root, such that said portion of the leading edge forms a recess between the central shaft and the leading edge;
• wherein the portion of said leading edge defining said recess between the central shaft and the leading edge provides for abutment and engagement with bone tissue of a subject disposed within said recess;
• and
• wherein the trailing edge extends in a direction of from the most proximal portion of the root in a radial outward direction towards the distal end.

A bone screw comprising:

• a. a screw shaft;
• b. a screw head;
• c. a screw tip;
• d. a thread;
• and
• e. an undercut structure in the thread facing the screw tip,
• wherein the thread comprises a thread surface facing the screw head having an angle larger than 90 degrees with the screw shaft, and wherein the undercut structure is formed in a leading edge of the thread that has first and second facets, said second facet extending from the screw shaft substantially normal to a longitudinal central axis thereof and said first facet extending from an end of the second facet at an inclination angle in the range of 95 degrees and 150 degrees to a crest surface parallel to the longitudinal central axis.