Polyaxial bone screw with uploaded threaded shank and method of assembly and use

A polyaxial bone screw assembly for implantation in a human bone comprising:

• a) an elongate shank having a body for fixation in a bone and a capture structure extending from the body, the capture structure having a top and a radially outer surface with a first helically wound guide and advancement structure;
• and
• b) a head having a base and a top portion, the head top portion having an open channel, the base having a lower opening with a second helically wound guide and advancement structure therein that is sized and shaped to rotatingly mate with the first guide and advancement structure, the base further having a cavity openly joined to the opening, the channel communicating with the cavity, the cavity communicating with an exterior of the base through the opening, during assembly the capture structure being positionable in the cavity upon operable rotation of the first guide and advancement structure with the second guide and advancement structure until a disengagement between the first and second guide and advancement structures occurs such that the capture structure is substantially in the cavity and the shank body is exterior of the cavity whereby the shank capture structure can only be loaded into the head from below through the opening and thereafter locked in position relative to the head, the first and second guide and advancement structures configured for frictional engagement when the capture structure is urged toward the opening without rotation while the capture structure is within the head such that the shank body is locked in a fixed angular position with respect to the head.

A polyaxial bone screw assembly for implantation into a human spine comprising:

• a) an elongate shank having a body for fixation to a bone and a capture structure extending from and integral with the body, the capture structure having a top, a radially outward facing surface with a first helically wound guide and advancement structure, and a tool engagement formation disposed adjacent the top, the tool engagement formation having a projection and a recessed tool seating surface having a bottom and an outer wall, both the bottom and outer wall sized and shaped for receiving and frictionally engaging a driving tool engaged with the tool engagement projection when driving the shank body into bone;
• and
• b) a head having a base with an inner surface defining a cavity, a portion of the inner surface having a second helically wound guide and advancement structure sized and shaped to rotatingly mate with the first guide and advancement structure, the base cavity communicating with an exterior of the base through an opening associated with the second guide and advancement structure such that the shank capture structure can only be upward loaded into the head through the lower opening in the head, the capture structure being pivotally disposed and captured in the cavity upon operable rotation of the first guide and advancement structure with the second guide and advancement structure until the first guide and advancement structure is disengaged from the second guide and advancement structure;
• (c) the head has upstanding spaced arms defining an open channel, the arms having a third guide and advancement structure on an inside surface thereof, the channel communicating with the cavity;
• (d) a closure structure insertable into an upper opening of the head, the closure structure being adapted for operably urging the shank in a direction to operably urge the shank capture structure against the head so as to frictionally lock the capture structure to the head, thereby locking the shank body in a selected angular position with respect to the head;
• and
• (e) the closure structure being sized and shaped to be positionable between the arms for closing the channel, the closure structure having a fourth guide and advancement structure for rotatably mating with the third guide and advancement structure.