Patent ID: 8734493

Claim:
A locking system for retaining a prosthetic implant to vertebrae comprising: a first bone screw for retaining and securing said prosthetic implant on to a vertebra; and at least one second bone screw for securing said prosthetic implant to another of said vertebrae, said first bone screw and said at least one second bone screw each having a head and being adapted to be screwed into bone; said at least one second bone screw engages said first bone screw to retain at least one of said first bone screw or said at least one second bone screw in a tightened position; wherein said first bone screw comprises a head having a first wall portion having a first radius and a second wall portion having a second radius that is larger than said first radius; said first wall portion being adapted to permit said at least one second bone screw to rotate when said at least one second bone screw is screwed into bone and said second wall portion being adapted to engage said head of said at least one second bone screw upon rotation of said first bone screw, thereby locking said head of said first bone screw to said head of said at least one second bone screw; wherein said first bone screw has a shank with a threaded portion having a threaded axis, said head of said bone screw having a head center that is offset from said threaded axis to provide an eccentric head portion.