초록 ▼

A polyaxial bone screw assembly includes a threaded shank body having an upper portion, a receiver, a compression insert and an articulation structure made from at least two discrete pieces. The shank upper portion cooperates with the compression insert to place the retainer in frictional engagement

A polyaxial bone screw assembly includes a threaded shank body having an upper portion, a receiver, a compression insert and an articulation structure made from at least two discrete pieces. The shank upper portion cooperates with the compression insert to place the retainer in frictional engagement with the receiver. The geometry of the retainer structure pieces corresponds and cooperates with the external geometry of the shank upper portion to frictionally envelope the retainer structure between the capture structure and an internal surface defining a cavity of the receiver.

대표청구항 ▼

1. A bone anchor assembly comprising: a) a bone attachment structure having an integral upper capture portion and a lower threaded portion for fixation in a bone;b) a receiver having an inner cavity and a lower opening through which the bone attachment structure can pivot with respect to the receive

1. A bone anchor assembly comprising: a) a bone attachment structure having an integral upper capture portion and a lower threaded portion for fixation in a bone;b) a receiver having an inner cavity and a lower opening through which the bone attachment structure can pivot with respect to the receiver; the inner cavity operably receiving the upper capture portion and having an interior surface; andc) a retainer structure being positioned within the receiver cavity prior to the bone attachment structure and having at least two discrete parts, each part having an upper capture portion engaging inner surface and a receiver cavity engaging outer surface, the inner surfaces configured to become into mating contact with the upper capture portion within the receiver cavity, so as to maintain the upper capture portion in the receiver, and wherein the outer surfaces are configured to be in slidable engagement with the cavity interior surface when the retainer structure is located in the receiver between the bone attachment structure and the cavity interior surface. 2. The assembly of claim 1, including a compression insert disposed within the receiver to frictionally engage the bone attachment structure. 3. The assembly of claim 1, wherein the bone attachment structure upper capture portion extends above the retainer structure. 4. The assembly of claim 1, wherein each retainer structure part outer surface and the cavity interior surface are partially spherical in shape. 5. The assembly of claim 1, wherein the bone attachment structure upper capture portion is uploaded into the cavity through the opening. 6. The assembly of claim 2, wherein the bone attachment structure upper capture portion extends above the retainer structure. 7. A bone anchor assembly comprising: a) a receiver having an upper portion integral with a base, the upper portion defining a rod-receiving channel therein, the base including a bottom opening communicating with an internal cavity, the cavity having a surface;b) a shank having a lower bone attachment structure and an integral upper capture structure up-loadable into the cavity through the receiver bottom opening; andc) a retainer structure having at least two discrete parts, each part with a top and bottom surface and being pre-disposed in the cavity of the receiver before the shank is up-loaded; and wherein the two discrete parts capture the shank in the receiver at the shank upper capture structure such that the shank is then pivotable with respect to the receiver, and the two discrete parts form a plurality of spaces between the parts that extend from the top to the bottom surfaces thereof with respect to each part. 8. The bone anchor assembly of claim 7, wherein the two discrete parts rotate while slidably engaging the receiver cavity surface when capturing the shank capture structure. 9. The bone anchor assembly of claim 7, wherein the shank is bottom-loaded. 10. The bone anchor assembly of claim 7, wherein the shank has polyaxial motion with respect to the receiver. 11. The bone anchor assembly of claim 7, wherein the two discrete parts pivot with respect to the shank. 12. The bone anchor assembly of claim 7, wherein the shank upper capture structure extends above each of the retainer discrete parts. 13. The bone anchor assembly of claim 7, wherein the two discrete parts move away from each other while slidably engaging the receiver cavity surface, so as to capture the shank capture structure. 14. The bone anchor assembly of claim 7, wherein the shank further includes an annular seating surface. 15. A bone anchor assembly comprising: a) a receiver including an upper portion having a rod-receiving channel and an integral base with a lower opening communicating with an internal cavity, the cavity having a cavity surface;b) a shank having a distal bone attachment portion and a proximal capture portion;c) a retainer structure including at least two discrete parts, each part having an outer surface and an internal surface that engages the shank proximal capture portion; and wherein the outer surface of the retainer structure is in slidable engagement with the cavity surface of the receiver and the internal surface captures the shank capture portion, such that the shank pivots with respect to the receiver. 16. The bone anchor assembly of claim 15, wherein the two discrete parts rotate while slidably engaging the receiver cavity surface when capturing the shank proximal capture structure. 17. The bone anchor assembly of claim 15, wherein the shank is bottom-loaded. 18. The bone anchor assembly of claim 15, wherein the shank has polyaxial motion with respect to the receiver. 19. The bone anchor assembly of claim 15, wherein the two discrete parts pivot with respect to the shank. 20. The bone anchor assembly of claim 15, wherein the shank proximal capture structure extends above each of the retainer discrete parts. 21. The bone anchor assembly of claim 15, wherein the two discrete parts move away from each other while slidably engaging the receiver cavity surface, so as to capture the shank proximal capture portion. 22. The bone anchor assembly of claim 15, wherein the shank further includes an annular seating surface. 23. A bone anchor assembly comprising: a) a receiver having an upper portion and base, the upper portion defining a rod-receiving channel therein, the base including a bottom opening communicating with an internal cavity, the cavity having a cavity surface;b) a shank having a lower bone attachment structure and an upper capture structure up-loadable into the cavity through the receiver bottom opening;c) a retainer structure having at least two discrete parts, each part being positioned within the cavity and substantially below the rod-receiving channel in the cavity and in slideable engagement with the cavity surface, prior to the shank being up-loaded; and wherein the two discrete parts mate to capture the shank in the receiver at the shank upper capture structure such that the shank is then pivotable with respect to the receiver and prevented from coming out of the receiver bottom opening. 24. A bone anchor assembly comprising: a) a shank having an elongate body including an upper capture portion and a lower threaded portion for fixation in a bone that are integral with the elongate body;b) a receiver having a body including an upper portion and a lower portion integral with the body, and an inner cavity operably receiving the shank upper capture portion and having an interior surface; the receiver including a lower opening through which the shank can pivot with respect to the receiver; andc) a retainer structure being positioned within the receiver cavity prior to the shank and having at least two discrete parts, each part having a shank engaging inner surface and a receiver cavity engaging outer surface, the inner surfaces configured to become into mating contact with the shank upper capture portion within the receiver cavity, so as to maintain the shank upper capture portion in the receiver, each part cooperating to prevent the shank from coming out of the lower opening, and wherein the outer surfaces are configured to be in slidable engagement with the cavity interior surface when the retainer structure is located in the receiver between the shank upper capture portion and the cavity interior surface, the retainer structure at least partially surrounding the shank upper capture portion. 25. A bone anchor assembly comprising: a) a bone attachment structure having an integral upper capture portion and a lower portion for fixation in a bone;b) a receiver having an inner cavity and a lower opening through which the bone attachment structure can pivot with respect to the receiver; the inner cavity operably receiving the upper capture portion and having an interior surface; andc) a retainer structure being positioned within the receiver cavity prior to the bone attachment structure and having at least two discrete parts, each part having an upper capture portion engaging inner surface and a receiver cavity engaging outer surface, the inner surfaces configured to become into mating contact with the upper capture portion within the receiver cavity, so as to maintain the upper capture portion in the receiver, and wherein the retainer structure is located in the receiver between the bone attachment structure and the cavity interior surface, so as to prevent the bone attachment structure from exiting the receiver lower opening. 26. A bone anchor assembly comprising: a) a receiver having an upper portion and base, the upper portion defining a rod-receiving channel therein, the base including a bottom opening communicating with an internal cavity, the cavity having a cavity surface;b) a shank having a lower bone attachment structure and an upper capture structure up-loadable into the cavity through the receiver bottom opening;c) a retainer structure having at least two discrete parts, each part being positioned within the cavity and moveable with respect to each other and with respect to the cavity surface, prior to the shank being up-loaded; and wherein the two discrete parts mate to capture the shank in the receiver at the shank upper capture structure such that the shank is then pivotable with respect to the receiver and prevented from coming out of the receiver bottom opening.