A bone fixation system comprising: a bone plate including a thru-bore having an entry diameter, an intermediate diameter, and an exit diameter, wherein said intermediate diameter is larger than said entry diameter and said exit diameter; and a bone screw assembly configured to be coupled to said thru-bore; wherein said screw assembly comprises: a bone screw having a head section, a thread section, and a central bore; an expandable ring coupled to said head section; and a pin arranged to be at least partially disposed in said central bore; wherein said pin includes a varying outer profile that engages said expandable ring to vary an outer diameter of said expandable ring to couple said screw assembly in said thru-bore; and the head section further comprising a ring channel configured to retain said expandable ring in both a relaxed position and an expanded position and wherein said pin comprises: a generally cylindrical body having a proximal end and a distal end; a graduated entry taper formed on said distal end; a first engagement diameter disposed along said body, wherein said first engagement diameter corresponds to a relaxed diameter of said expandable ring; and a second engagement diameter disposed along said body between said first engagement diameter and said proximal end of said pin, wherein said second engagement diameter corresponds to an expanded diameter of said expandable ring. a bone plate including a thru-bore having an entry diameter, an intermediate diameter, and an exit diameter, wherein said intermediate diameter is larger than said entry diameter and said exit diameter; and a bone screw assembly configured to be coupled to said thru-bore; wherein said screw assembly comprises: a bone screw having a head section, a thread section, and a central bore; an expandable ring coupled to said head section; and a pin arranged to be at least partially disposed in said central bore; wherein said pin includes a varying outer profile that engages said expandable ring to vary an outer diameter of said expandable ring to couple said screw assembly in said thru-bore; a bone screw having a head section, a thread section, and a central bore; an expandable ring coupled to said head section; and a pin arranged to be at least partially disposed in said central bore; wherein said pin includes a varying outer profile that engages said expandable ring to vary an outer diameter of said expandable ring to couple said screw assembly in said thru-bore; and the head section further comprising a ring channel configured to retain said expandable ring in both a relaxed position and an expanded position and wherein said pin comprises: a generally cylindrical body having a proximal end and a distal end; a graduated entry taper formed on said distal end; a first engagement diameter disposed along said body, wherein said first engagement diameter corresponds to a relaxed diameter of said expandable ring; and a second engagement diameter disposed along said body between said first engagement diameter and said proximal end of said pin, wherein said second engagement diameter corresponds to an expanded diameter of said expandable ring. a generally cylindrical body having a proximal end and a distal end; a graduated entry taper formed on said distal end; a first engagement diameter disposed along said body, wherein said first engagement diameter corresponds to a relaxed diameter of said expandable ring; and a second engagement diameter disposed along said body between said first engagement diameter and said proximal end of said pin, wherein said second engagement diameter corresponds to an expanded diameter of said expandable ring.