Patent ID: 8663290

Claim:
An assembly for a polyaxial screw comprising: a bone anchor having a spherical connector and a shank with at least one thread formed along a length of said shank and, a connector assembly having a first side wall and a second side wall each having a U-shaped opening, said connector assembly including an internal passageway having a wall that extends from a first end to a second end, a diameter of the internal passageway being greater than the diameter of the spherical connector at said first end and the diameter of the internal passageway at said second end being smaller than the diameter of the spherical connector, said internal passageway further including a first groove formed in said wall of the internal passageway, and a retaining ring having a circular cross section is positioned within said first groove, said first groove includes an upper end wall, a lower end wall and a sidewall of said first groove therebetween, said sidewall of said first groove is angularly positioned wherein a junction of the upper end wall and said sidewall of said first groove forms a first annulus having a first diameter and a junction of the lower end wall and said sidewall of said first groove forms a second annulus having a second diameter, said second diameter greater than said first diameter; and a saddle being generally cylindrical in shape and having a generally flat upper surface and a lower surface that is generally spherical and is configured to conform to the surface of the spherical connector, and a second groove formed about the circumference of said generally cylindrical saddle, wherein as the shank is inserted into the first end of said internal passageway and out of the second end of the internal passageway the spherical connector is moved past the retaining ring which is initially expanded to allow the spherical connector to pass and once past the retaining ring will return to its unexpanded state, and said saddle is inserted into the first end of said internal passageway and as the saddle is moved toward said spherical connector the retaining ring is initially expanded and will return to its unexpanded state whereby said retaining ring simultaneously engages said first annulus formed from said junction of said upper end wall and said sidewall of said first groove and said second groove to prohibit the removal of the saddle from the connector assembly.