Polyaxial bone anchor with compound articulation and pop-on shank

Abstract

A polyaxial bone screw assembly includes a threaded shank body having an integral shank head receivable in a one-piece receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A compression insert (some with an independent tool lock, lock and release feature and/or friction fit feature) and a split retaining ring articulatable with respect to both the shank head and the receiver (prior to locking) cooperate with the receiver to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra.

What is claimed and desired to be secured by Letters Patent is as follows: 
     
         1 . In a bone anchor, the improvement comprising:
 a) a shank having a body for fixation to a bone and an integral upper portion having a substantially spherical surface;   b) a receiver having a top portion and a base with a lower opening, the receiver top portion defining a first open channel, the base having a curved surface partially defining a cavity, the channel communicating with the cavity and the lower opening;   c) at least one insert disposed within the receiver, the insert having a second open channel and a concave surface operatively frictionally mating and locking with the shank first spherical surface;   d) a resilient open retainer captured within the cavity and expandable in the cavity about at least a portion of the shank, the open retainer having an inner surface for unlocked slidable, articulatable engagement with the shank and an outer surface for unlocked slidable articulatable engagement with the receiver curved surface; and   e) wherein expansion-only operative locking engagement occurs between the shank upper portion and the retainer and between the retainer and the receiver.   
     
     
         2 . The improvement of  claim 1  wherein the receiver curved surface has a first radius and the retainer outer surface has a second radius, the first radius being substantially equal to the second radius. 
     
     
         3 . The improvement of  claim 1  wherein the retainer inner surface has a first radius and the shank substantially spherical surface has a second radius, the first radius being substantially equal to the second radius. 
     
     
         4 . The improvement of  claim 1  wherein at least one of the insert arms has an outer surface engaging the receiver top portion. 
     
     
         5 . The improvement of  claim 4  wherein the receiver top portion has at least one surface crimped inwardly against at least one of the insert arms. 
     
     
         6 . The improvement of  claim 1  wherein the insert is top loaded into the receiver and then rotated into a position above the retainer with the second channel aligned with the first channel. 
     
     
         7 . The improvement of  claim 1  wherein the receiver top portion has a first pair of opposed tool receiving through apertures formed therein and the insert has a second pair of opposed tool receiving apertures in alignment with the first pair of apertures, the first pair of apertures sized and shaped to provide tool access to the insert, each of the second pair of opposed tool receiving apertures having a tool receiving surface sized and shaped to allow a tool to press the insert downwardly into temporary locking engagement with the shank. 
     
     
         8 . The improvement of  claim 7 , wherein the receiver top portion has at least one sloping surface communicating with each of the first pair of apertures, each sloping surface sized and shaped for aligning a tool with the respective insert tool receiving surface. 
     
     
         9 . The improvement of  claim 8  wherein the receiver top portion at least one sloping surface is a first sloping surface and the insert has a second sloping surface substantially aligned with the first sloping surface, the second sloping surface being adjacent to and oriented at an obtuse angle with respect to one of the insert tool receiving surfaces. 
     
     
         10 . The improvement of  claim 1  wherein the retainer has a top surface and a slit. 
     
     
         11 . The improvement of  claim 10  wherein the slit is disposed at an obtuse angle with respect to the top surface. 
     
     
         12 . The improvement of  claim 10  wherein the retainer top surface is planar. 
     
     
         13 . The improvement of  claim 1  wherein the insert is spaced from the retainer in all angular orientations of the shank with respect to the receiver. 
     
     
         14 . In a bone anchor, the improvement comprising:
 a) a shank having a body for fixation to a bone and an integral head having at least one curved surface;   b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a first surface partially defining a cavity, the channel communicating with the cavity, the receiver having at least one tool receiving through aperture;   c) at least one insert disposed within the receiver, the insert sized and shaped to directly engage with the shank head curved surface and to cooperate with lock and release tools that extend through the receiver tool receiving aperture for pressing the insert downwardly against the shank head into one of non-floppy sliding engagement and temporary locking engagement with the shank head; and   d) a resilient open retainer captured within the cavity and expandable within the cavity about at least a portion of the shank head, the retainer having a first polyaxial articulation with the shank head and a second polyaxial articulation with the receiver when in an unlocked position, and wherein expansion-only locking engagement occurs between the shank head and the retainer and between the retainer and the receiver when in a locked position.   
     
     
         15 . The improvement of  claim 14  wherein the at least one tool receiving aperture is a pair of opposed tool receiving apertures and the insert has a pair of opposed recessed tool receiving surfaces formed in outer walls thereof, the recessed tool receiving surfaces being accessible through the receiver tool receiving apertures. 
     
     
         16 . The improvement of  claim 14  wherein the receiver has a first tool receiving sloping surface adjacent the through aperture and the insert has a second tool receiving surface generally aligned with the first tool receiving sloping surface. 
     
     
         17 . The improvement of  claim 16  wherein the insert tool receiving surface forms a v-shaped recess. 
     
     
         18 . In a bone anchor, the improvement comprising:
 a) a shank having a body for fixation to a bone and an integral head having a first spherical surface;   b) a receiver having a top portion and a base, the receiver top portion having first and second opposed arms defining an open channel, the base having a lower opening and a second spherical surface partially defining a base cavity, the channel communicating with the cavity and the lower opening, each receiver arm having a tool receiving sloping surface and a through aperture;   c) at least one top loaded insert disposed within the receiver, the insert having a third spherical surface sized and shaped to directly engage with the shank head first spherical surface, the insert having third and fourth opposed arms, each arm having a recessed surface aligned with one of the receiver sloping surfaces and sized and shaped for receiving lock and release tools that extend through the receiver tool receiving apertures for pressing the insert downwardly into engagement with the shank head; and   d) a resilient open retainer captured within the cavity and expandable within the cavity about at least a portion of the shank head first spherical surface, the retainer having a first polyaxial articulation with the shank head first spherical surface and a second polyaxial articulation with the receiver second spherical surface when in an unlocked position, and wherein the retainer is in expansion-only locking engagement between the shank head and the receiver when the shank is in a locked position with respect to the receiver.   
     
     
         19 . The improvement of  claim 18 , wherein the retainer has a fourth spherical surface and a fifth spherical surface, the fourth spherical surface engaging the shank first spherical surface and the fifth spherical surface engaging the receiver second spherical surface. 
     
     
         20 . The improvement of  claim 18 , wherein the insert is top loaded into the receiver.