An interbody fusion system comprising in combination: a biomechanical spacer implant adapted for insertion within an intervertebral space between a superior vertebral body and an inferior vertebral body, said implant having a first insertion end portion, a second end portion opposite the first end portion, a first lateral side portion, a second lateral side portion, an upper surface and a lower surface; a bone plate having a left side surface and a right side surface, a top surface and a bottom surface, a first upper surface and a second lower surface, with a distance between said first upper surface and said second lower surface defining a thickness of said plate, a horizontal middle plane between the first upper surface and the second lower surface and a plurality of boreholes suitable for accommodating longitudinal fixation elements extending through said thickness of said plate, wherein each of said boreholes has an elongated slot located at or near said horizontal middle plane, and surrounded by arcuate and dished curvilinear sidewalls which form an engagement seat extending from said elongated slot to said first upper surface for receiving at least two bone fixation elements therein, each of said bone fixation elements having a screw head adapted to engage or be engaged by an engaging surface of each screw head to urge the screw heads into a convergent and interference relationship with one another and with said engagement seat upon tightening, thereby resulting in a locking engagement of said bone plate engagement seat and said fixation elements and a diverging outlet portion extending from said elongated slot toward said second lower surface, said divergent outlet being adapted to provide a range of angulation of each said fixation elements, whereby each of said fixation elements is individually positionable within both an inferior and superior vertebral body associated with said interbody fusion system; and a plurality of fixation elements adapted for cooperating with said bone plate and thereby securing said bone plate to said superior and inferior vertebral bodies. a biomechanical spacer implant adapted for insertion within an intervertebral space between a superior vertebral body and an inferior vertebral body, said implant having a first insertion end portion, a second end portion opposite the first end portion, a first lateral side portion, a second lateral side portion, an upper surface and a lower surface; a bone plate having a left side surface and a right side surface, a top surface and a bottom surface, a first upper surface and a second lower surface, with a distance between said first upper surface and said second lower surface defining a thickness of said plate, a horizontal middle plane between the first upper surface and the second lower surface and a plurality of boreholes suitable for accommodating longitudinal fixation elements extending through said thickness of said plate, wherein each of said boreholes has an elongated slot located at or near said horizontal middle plane, and surrounded by arcuate and dished curvilinear sidewalls which form an engagement seat extending from said elongated slot to said first upper surface for receiving at least two bone fixation elements therein, each of said bone fixation elements having a screw head adapted to engage or be engaged by an engaging surface of each screw head to urge the screw heads into a convergent and interference relationship with one another and with said engagement seat upon tightening, thereby resulting in a locking engagement of said bone plate engagement seat and said fixation elements and a diverging outlet portion extending from said elongated slot toward said second lower surface, said divergent outlet being adapted to provide a range of angulation of each said fixation elements, whereby each of said fixation elements is individually positionable within both an inferior and superior vertebral body associated with said interbody fusion system; and a plurality of fixation elements adapted for cooperating with said bone plate and thereby securing said bone plate to said superior and inferior vertebral bodies.