An anterior cervical plate assembly comprising: a base plate (11; 211) including: at least two bone screw seats (222a-222d), each bone screw seat including a borehole (223a-223d) dimensioned to receive a bone screw (12a-12d), and a first blocking seat positioned between the at least two bone screw seats(222a-222d); and a blocking mechanism (14a, 14b; 214a, 214b; 1514) retained within the first blocking seat of the base plate (11; 211), the blocking mechanism (14a, 14b; 214a, 214b; 1514) being selectively positionable between a closed position in which the blocking mechanism (14a, 14b; 214a, 214b; 1514) obstructs at least one bone screw seat of the base plate (222a-222d) to retain a bone screw with the base plate (11; 211), and an open position in which the bone screw seats (222a-222d)are unobstructed; wherein the blocking mechanism (14a, 14b; 214a, 214b; 1514) includes a central biasing element and a first blocking element (1114a, 1114b; 1526a, 1526b) and a second blocking element (1114a, 1114b; 1526a, 1526b), wherein the first blocking element (1114a, 1114b; 1526a, 1526b) is configured to obstruct a first bone screw seat (222a-222d) of the at least two bone screw seats (222a-222d), and the second blocking element (1114a, 1114b; 1526a, 1526b) is configured to obstruct a second bone screw seat (14a, 14b; 214a, 214b) of the at least two bone screw seats (14a, 14b; 214a, 214b), and wherein the first blocking element (1114a, 1114b; 1526a, 1526b) and the second blocking element (1114a, 1114b; 1526a, 1526b) are independently positionable from each other and wherein the first blocking element (1114a, 1114b; 1526a, 1526b) and the second blocking element (1114a, 1114b; 1526a, 1526b) define a housing cavity which is dimensioned to house a portion of the central biasing element (1126; 1526). at least two bone screw seats (222a-222d), each bone screw seat including a borehole (223a-223d) dimensioned to receive a bone screw (12a-12d), and a first blocking seat positioned between the at least two bone screw seats(222a-222d); and a blocking mechanism (14a, 14b; 214a, 214b; 1514) retained within the first blocking seat of the base plate (11; 211), the blocking mechanism (14a, 14b; 214a, 214b; 1514) being selectively positionable between a closed position in which the blocking mechanism (14a, 14b; 214a, 214b; 1514) obstructs at least one bone screw seat of the base plate (222a-222d) to retain a bone screw with the base plate (11; 211), and an open position in which the bone screw seats (222a-222d)are unobstructed; wherein the blocking mechanism (14a, 14b; 214a, 214b; 1514) includes a central biasing element and a first blocking element (1114a, 1114b; 1526a, 1526b) and a second blocking element (1114a, 1114b; 1526a, 1526b), wherein the first blocking element (1114a, 1114b; 1526a, 1526b) is configured to obstruct a first bone screw seat (222a-222d) of the at least two bone screw seats (222a-222d), and the second blocking element (1114a, 1114b; 1526a, 1526b) is configured to obstruct a second bone screw seat (14a, 14b; 214a, 214b) of the at least two bone screw seats (14a, 14b; 214a, 214b), and wherein the first blocking element (1114a, 1114b; 1526a, 1526b) and the second blocking element (1114a, 1114b; 1526a, 1526b) are independently positionable from each other and wherein the first blocking element (1114a, 1114b; 1526a, 1526b) and the second blocking element (1114a, 1114b; 1526a, 1526b) define a housing cavity which is dimensioned to house a portion of the central biasing element (1126; 1526). <EOS>