Patent ID: 6716214
Filing Date: 2004-04-06
Classification: A61B

Abstract:
A polyaxial bone screw comprising:(a) a shank having a body adapted to be implanted in a bone and a capture structure extending from said body; said capture structure including at least one spline that extends radially outward therefrom; (b) a head having a channel adapted to receive a rod member and a base having a cavity with a partial spherical surface and communicating with said channel through an upper opening; said cavity communicating with an exterior of said head through a lower opening sized and shaped to receive said shank capture structure therethrough; (c) a retainer ring that is receivable into said head cavity and having an external partial spherical surface sized and shaped to be seated on said head partial spherical surface; said ring having a central bore with an axial pass through ring channel opening into said bore for each spline respectively; said ring bore and ring channels being sized and shaped to allow said shank capture structure to axially pass therethrough and then be rotated; said retainer ring also having a capture recess for each spline sized and shaped to receive and capture a respective spline when said shank is subsequently moved axially downward relative to said retainer ring such that said capture structure is captured by said ring, but said shank can be rotated relative to said head in an unlocked assembly configuration; and (d) a closure top for operably urging said shank downward so as to frictionally engage said ring surface with said head surface so as to lock said shank in position relative to said head in a locked configuration.