Patent ID: 7503918

Claim:
A system for immobilizing two or more vertebrae, which system comprises two or more screws, an elongate connecting member and two or more fastening systems, wherein each screw comprises a screw body and a screw head having the shape of a portion of a sphere consisting of a first spherical surface portion between the screw body and a diametral plane orthogonal to an axis of the screw body and a second spherical surface portion; and each fastening system comprises: a clamping member; and a fastening member formed in one piece having the shape of a ring having a lateral wall around an axial passage, said wall including a first aperture adapted to receive and to cooperate with said clamping member and a second aperture having a first portion and a second portion, said two portions communicating with each other, the first portion being angularly offset relative to the second portion about an axis (Y, Y′) of the axial passage of the fastening member, said first portion having a diametral axis (Z, Z′) substantially coinciding with that of said first aperture and a rim forming a bearing surface for said first spherical surface portion of the screw head, said second portion of the second aperture allowing the screw head to pass through it, said axial passage being adapted to receive at least one end of said connecting member and said screw head, whereby the screw head is introduced into the axial passage of the fastening member via said second portion of the second aperture by rotating said fastening member, with the bearing surface of the first portion of the second aperture made to face the first spherical surface portion of the screw head, the end of the connecting member and the screw head immobilized against rotation and against movement in translation relative to said fastening member.