Systems and methods for the fixation or fusion of bone

A method for the fixation or fusion of a first bone segment to a second bone segment across a joint, the method comprising:

• providing an elongate implant having a proximal end, a distal end, a longitudinal axis, a lumen extending through the elongate implant along the longitudinal axis, and a cross-sectional profile transverse to the longitudinal axis that is defined by at least one apex, wherein the elongate implant is free from external screw threads;
• and
• inserting the elongate implant through the first bone segment and transversely across the joint and into the second bone segment by applying an axially directed force to the elongate implant, such that the distal end of the elongate implant is inserted into the second bone segment and the proximal end of the elongate implant remains within the first bone segment;
• wherein the first bone segment and/or the second bone segment is a vertebra.