Patent ID: 8540753
Filing Date: 2013-09-24
Classification: A61B

Abstract:
1. A polyaxial bone screw assembly for implantation in a human comprising: a) an elongate shank having a body for fixation to a bone and a capture structure extending from the body, the capture structure having a first helically wound guide and advancement structure; and b) a head having an upper opening and a base with an inner surface defining a base cavity and a lower opening communicating with cavity having a second helically wound guide and advancement structure sized and shaped to rotatingly mate with the first guide and advancement structure, the capture structure being disposed and captured in the cavity upon operable mating and rotation of the first guide and advancement structure with the second guide and advancement structure until the first guide and advancement structure becomes disengaged from the second guide and advancement structure, the capture structure having a first orientation wherein the capture structure is disposed in the cavity and the shank body is swivelable relative to the head, and a second orientation, wherein the capture structure is in a non-threadedly mated frictional engagement with the second guide and advancement structure so that the shank cannot swivel relative to the head and wherein the shank capture structure can only be threadedly loaded into the cavity through the lower opening.