Patent ID: 7625396
Filing Date: 2009-12-01
Classification: A61B

Abstract:
1. A polyaxial bone screw assembly comprising: a) a shank having an elongate body and a capture structure, the body configured for fixation to a bone; b) a head having a top portion and a base, the head top portion defining an open channel having a width, the base having a curved seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive at least the shank body therethrough; and c) a retainer structure having at least two discrete parts, each part having an inner surface and an outer surface, the inner surface configured to be in a fixed engagement with the capture structure and the outer surface having a lower portion that is curved and slidably engages the head seating surface so as to polyaxially rotate relative to the head seating surface during assembly and before locking when the retainer part is captured between the capture structure and the head seating surface, the discrete parts having a first configuration wherein the parts have a width less than the width of the channel to allow passage of the parts through the channel and a second configuration wherein the combined parts have a width greater than the channel and wherein the combined parts support the shank in the head during assembly the retainer structure and the shank being polyaxially rotatable together relative to the head.