Screw equipped ilium mortar transplantation systematic piece null of crotch

摘要

PURPOSE: To reduce clogging of a graft at the time of inserting a prosthetic component of a hip joint by dividing the thread of a self-tapping screw into segments with a number of grooves and gradually reducing the radii of the screw along the leading edge to the terminating edge of each segment. CONSTITUTION: A metallic cup shell 2 is equipped with a self-tapping screw around its exterior surface. The thread of the screw consists of long thread segments 8 and short thread segments 10 placed alternately. All segments 8 and 10 are gradually reduced from leading edges 12 to terminating edges 14 in order to reduce clogging of a graft arising from the viscoelasticity of the bone. The degree of reduction is at least 3% of the radius of the screw, ideally around 10%, but not exceeding 30%. As a result, the leading edges 12 of the segments 8 and 10 have sharp cutting surfaces facing the bone, and tap the bone conveniently without deflecting the bone. In the figure, RaRbReRd is satisfied.