Fastener assembly that fastens to polyaxial pedicle screw

A fastener assembly comprising:

• a spinal prosthesis comprising upper and lower elongate rods adapted for attachment to spinal structure of a patient, wherein said upper elongate rod extends from an upper plate, and said lower elongate rod extends from a lower plate, and a flexure assembly is positioned between said plates;
• left and right pedicle screws mounted on left and right distal portions of each of said elongate rods for attaching said elongate rods to the spinal structure, each of said pedicle screws comprising a polyaxial head;
• a left fastening portion fastened to said polyaxial head of said left pedicle screw of said lower elongate rod and a right fastening portion fastened to said polyaxial head of said right pedicle screw of said lower elongate rod, and wherein said left and right fastening portions are located at opposite ends of said lower elongate rod;
• and
• a left connector element that extends from said left fastening portion in a direction transverse to said lower elongate rod and a right connector element that extends from said right fastening portion in a direction transverse to said lower elongate rod, said connector elements being connectable to another spinal structure, and wherein said left and right connector elements are located at opposite ends of said lower elongate rod;
• and
• wherein at least one of said left and right fastening portions comprises a wedge ring and at least one of said corresponding left and right connector elements comprises a conical ring into which said wedge ring fits, said connector element comprising a connecting member that extends from said conical ring, wherein said wedge ring is sized to fit over said polyaxial head and said conical ring wedges said wedge ring onto said polyaxial head;
• and further comprising a fastening tool operative to install said wedge ring and said connector element on at least one of said corresponding left and right pedicle screws, wherein said fastening tool comprises a pair of jaws into which said wedge ring and said connector element are inserted, a pair of handles connected to said jaws and an alignment indicator that indicates proper alignment of said connector element with said spinal prosthesis, wherein squeezing of said handles causes said conical ring to wedge said wedge ring onto said polyaxial head of each of said polyaxial screws.