Patent ID: 8512410

Claim:
A stemless humerus implant adapted to be securely fixed within the humerus of a patient with minimal removal of bone material, said stemless humerus implant having a cup shaped body ( 10 ) having sidewalls between an open top side ( 11 ) and a convex bottom side ( 12 ), the cup shaped body further comprising a multiple start thread ( 13 ) extending radially from the sidewalls of the body, said multiple start thread comprised by: a plurality of fins ( 14 , 15 ) starting with a first fin ( 14 ) disposed in proximity to the convex bottom side and ending with a last fin ( 15 ) disposed in proximity to the top side, with cutouts ( 16 ) between the fins; each of the plurality of fins ( 14 , 15 ) having an inclined leading surface ( 21 ) which helps in incising into the bone by rotating the body in an inward direction; each of the plurality of fins further having a forward oriented undercut trailing surface ( 25 ) resulting in an angle of less than 90 degrees between a top surface ( 23 ) and the trailing surface ( 25 ) blocking rotation in the outward direction, wherein depth of the fins increase from the first fin ( 14 ) to the last fin ( 15 ), wherein thickness of the fins decrease from the first fin ( 14 ) to the last fin ( 15 ), and wherein at least one of surfaces ( 21 , 23 , 25 ) of the fins are rounded to reduce stress risers in the native bone stock.