Upload shank swivel head bone screw spinal implant

Abstract

A polyaxial bone screw having a bone implantable shank, a head and a retaining ring. The retaining ring includes an outer partial hemispherical surface and an inner bore with radially extending channels and partial capture recesses. The shank includes a bone implantable body with an external helical wound thread and an upwardly extending capture structure. The capture structure includes at least one spline which extends radially outward and has a wedged surface that faces radially outward therefrom. The capture structure operably passes through a central bore of the retaining ring while the spline passes through a suitably shaped channel so that the spline becomes positioned above the head at which time the shank is rotated appropriately and the shank is drawn back downwardly so that the spline engages and seats in the capture recess. The head includes an internal cavity having a spherical shaped surface that mates with the ring surface and has a lower restrictive neck that prevents passage of the ring once the ring is seated in the cavity.

1 . A polyaxial bone screw assembly including:
 a) a shank having a body for fixation to a bone and a capture structure extending from the body, the capture structure having an outer surface with a first helically wound guide and advancement structure;   b) a head having a top portion and a base, the head top portion defining an open channel, the base having a 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 the capture structure therethrough; and   c) a retainer structure separate from the shank and having an external surface, the retainer structure is joinable with the shank capture structure within the head so as to secure the retainer structure to the capture structure within the head, the retainer structure external surface configured to be in slidable mating engagement with the seating surface of the head so as to enable polyaxial movement of the shank and retainer structure with respect to the head while in a positioning configuration; and   d) the shank capture structure adapted and positioned to receive a downward force during locking and thereafter transfer the downward locking force to the retainer to urge the retainer structure against the head and lock an angular position of the shank and retainer structure relative to the head in a locked configuration.   
   
   
       2 . The assembly of  claim 1  wherein the downward force is a direct downward force. 
   
   
       3 . The assembly of  claim 1  wherein:
 a) the head seating surface which is located to be in slidable mating engagement with the retainer structure external surface is substantially spherical;   b) the retainer structure external surface that is in slidable mating engagement with the head seating surface is substantially spherical; and   c) the retainer structure is a continuous closed ring and the shank and retainer structure are threadably joined together within the head.   
   
   
       4 . The assembly of  claim 1  wherein the shank capture structure extends above the retainer structure and has a tool engagement formation disposed thereon that is accessible by a tool when the shank and retainer structure are joined and that is adapted for non-slip engagement by such a tool for driving the shank body into bone while the shank is secured to the retainer structure. 
   
   
       5 . The assembly of  claim 4  wherein the capture structure tool engagement formation is an axial projection having a hexagonal profile. 
   
   
       6 . The assembly of  claim 4  wherein the tool engagement formation is a projection and the retainer structure has a tool seating surface, the projection and the tool seating surface partially defining a recess for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       7 . The assembly of  claim 4  wherein the tool engagement formation is a projection and the capture structure has a tool seating surface, the projection and the tool seating surface partially defining a recess about a base of the projection adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       8 . The assembly of  claim 4  wherein the tool engagement formation is a projection, the retainer structure has a first seating surface, and the capture structure has a second seating surface; the projection, the first seating surface and the second seating surface partially defining a recess at a base of the projection adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with both the first and second seating surfaces when driving the shank body into bone. 
   
   
       9 . The assembly according to  claim 1  wherein the retainer structure external surface includes a top surface having a tool engagement formation. 
   
   
       10 . The assembly of  claim 9  wherein the tool engagement formation is a slot located within the top surface. 
   
   
       11 . The assembly according to  claim 1  wherein the retainer structure has a slot extending from the external surface to the internal surface, exposing a portion of the first helically wound guide and advancement structure when the retainer structure is fixed to the capture structure, the slot sized and shaped to accept a tool for deforming a portion of the first helically wound guide and advancement structure. 
   
   
       12 . The assembly according to  claim 1  wherein the first helically wound guide and advancement structure is a raised helical rib. 
   
   
       13 . The assembly according to  claim 1  wherein the second helically wound guide and advancement structure is a raised helical rib. 
   
   
       14 . The assembly according to  claim 1  wherein the shank is cannulated. 
   
   
       15 . The assembly according to  claim 1  wherein the retainer structure has a first planar seating surface and the capture structure has a second planar seating surface, the first and second planar seating surfaces being in contact when the retainer structure is secured to the capture structure. 
   
   
       16 . The assembly of  claim 15  wherein the retainer structure has a second internal surface, the second internal surface and the first planar seating surface partially defining a recess, the second planar seating surface disposed in the recess when the retainer structure is secured to the capture structure. 
   
   
       17 . The assembly according to  claim 1  wherein the retainer structure is sized and shaped to be loadable into the head through the open channel and the shank is sized and shape to be loadable into the head through the base opening. 
   
   
       18 . The assembly of  claim 17  wherein the head seating surface includes a recess shaped and sized for providing for and guiding the insertion of the retainer structure into the cavity. 
   
   
       19 . The assembly according to  claim 1  further including a closure structure insertable into the head, the closure structure for operably urging the shank in a direction to frictionally lock the position of the retainer structure external surface relative to the head seating surface, thereby locking the shank body in a selected angle with respect to the head. 
   
   
       20 . The assembly of  claim 19  wherein:
 a) the head has upstanding spaced arms defining the open channel, the arms having guide and advancement structures on an inside surface thereof; and   b) the closure structure is sized and shaped to be positionable between the arms for closing the channel, the closure structure having a closure guide and advancement structure for rotatably mating with the guide and advancement structures on the arms, biasing the closure structure upon advancement rotation against a rod disposed in the channel.   
   
   
       21 . The assembly of  claim 19  wherein the capture structure end has a dome sized and shaped to extend into the channel for engagement with a rod when received in the head and wherein the closure structure is adapted to operably urge the rod against the dome upon the closure structure being positioned in the head. 
   
   
       22 . A polyaxial bone screw assembly for surgical implantation and including a shank having an upper end and a threaded body for inserting into a bone and a head having an outward opening channel adapted to receive a rod within the channel, the head having a lower shank receiving opening, the bone screw including:
 a) a capture structure disposed on the shank upper end sized and configured to be positioned in the head such that the shank extends through the shank receiving opening of the head; and   b) a retainer structure separate from the shank having an external surface; the shank and retainer structure joining in the head so as to be secured together and to polyaxially rotate with one another relative to the head when in a non locking configuration; the shank being positioned to first receive a downward locking force from above and to then transfer the downward locking force to the retainer structure to lock the retainer structure against the head and to lock the angular position of the retainer structure and shank with respect to the head in a locked configuration.   
   
   
       23 . The improvement of  claim 22  wherein the downward locking force is a direct locking force. 
   
   
       24 . The improvement of  claim 22  wherein:
 a) the head has an inner substantially spherical seating surface partially defining a cavity, the cavity communicating with both the channel and the shank receiving opening;   b) the retainer structure external surface is substantially spherical and in slidable mating engagement with the head seating surface; and   c) the retainer structure is a closed circular ring and the shank and retainer structure are threadably joined within the head.   
   
   
       25 . The improvement of  claim 22  wherein the capture structure has a tool engagement formation disposed thereon for non-slip engagement by a tool for driving the shank body into bone. 
   
   
       26 . The improvement of  claim 25  wherein the tool engagement formation is a projection and the retainer structure has a tool seating surface, the projection and the tool seating surface partially defining a recess for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       27 . The improvement of  claim 25  wherein the tool engagement formation is a projection and the capture structure has a tool seating surface, the projection and the tool seating surface partially defining a recess about a base of the projection adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       28 . The improvement of  claim 25  wherein the tool engagement formation is a projection, the retainer structure has a first seating surface, and the capture structure has a second seating surface; the projection, the first seating surface and the second seating surface partially defining a recess adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with both the first and second seating surfaces when driving the shank body into bone. 
   
   
       29 . The improvement according to  claim 22  wherein the retainer structure external surface includes a top surface having a tool engagement formation. 
   
   
       30 . The improvement of  claim 29  wherein the tool engagement formation is a slot located in the top surface. 
   
   
       31 . The improvement according to  claim 22  wherein the retainer structure has a slot extending from the external surface to the internal surface, exposing a portion of the first helically wound advancement structure when the retainer structure is secured to the capture structure, the slot being sized and shaped to be adapted to accept a tool for deforming a portion of the first helically wound advancement structure. 
   
   
       32 . The improvement according to  claim 22  wherein the first helically wound advancement structure is a raised helical rib. 
   
   
       33 . The improvement of  claim 32  wherein the second helically wound advancement structure is a raised helical rib. 
   
   
       34 . The improvement according to  claim 22  wherein the retainer structure has a first planar seating surface and the capture structure has a second planar seating surface, the first and second planar seating surfaces being in contact when the retainer structure is secured to the capture structure. 
   
   
       35 . A polyaxial bone screw assembly including:
 a) a shank having a threaded body for fixation to a bone and a capture structure extending from the body, the capture structure having an outer substantially cylindrical surface with a first raised helical rib disposed thereon;   b) a head having a top portion and a base, the top portion defining an open channel, the base having a partial substantially spherical seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through a lower opening therein sized and shaped to receive the shank when the capture structure is positioned within the head;   c) a retainer structure separate from the shank and having an external partial spherical surface and an internal substantially cylindrical surface having a second raised helical rib disposed thereon, the first rib configured to rotatably mate with the second rib to secure the retainer structure to the capture structure within the head cavity so as to allow the retainer structure and shank to move together polyaxially relative to the head in an unlocked configuration; the shank extending above the retainer structure when joined therewith; the shank first receiving a downward locking force from a rod positioned in the head channel and thereafter transferring the downward locking force to the retainer structure to lock the angular position of the shank and retainer structure relative to the head in a locked configuration; and   d) a tool engagement formation disposed on at least one of the capture structure and the retaining structure, the formation adopted for non-slip engagement by a tool for driving the shank body into bone and being accessible to such a tool when the retainer structure and shank are joined in the head.   
   
   
       36 . The assembly of  claim 35  wherein the shank receives the downward locking force directly from the rod positioned in the head channel. 
   
   
       37 . The assembly of  claim 35  wherein the tool engagement formation is a projection extending axially from the capture structure and the retainer structure has a tool seating surface, the projection and the tool seating surface partially defining a recess about a base of the projection adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       38 . The assembly of  claim 35  wherein the tool engagement formation is a projection extending axially from the capture structure and the capture structure has a tool seating surface, the projection and the tool seating surface partially defining a recess about a base of the projection adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with the tool seating surface when driving the shank body into bone. 
   
   
       39 . The assembly of  claim 35  wherein the tool engagement formation is a projection extending axially from the capture structure, the retainer structure has a first seating surface, and the capture structure has a second seating surface; the projection, the first seating surface and the second seating surface defining a recess adapted for receiving a driving tool engaged with the tool engagement projection and wherein the driving tool is adapted to be in contact with both the first and second seating surfaces when driving the shank body into bone. 
   
   
       40 . The assembly of  claim 35  wherein the tool engagement formation is a slot formed in the retainer structure external surface. 
   
   
       41 . The assembly of  claim 40  wherein the slot extends from the retainer structure external surface to the internal surface, exposing a portion of the first helically wound advancement structure when the retainer structure is secured to the capture structure, the slot being sized and shaped to be adapted accept a tool for deforming a portion of the first helically wound advancement structure. 
   
   
       42 . The assembly according to  claim 35  wherein the retainer structure has a first planar seating surface and the capture structure has a second planar seating surface, the first and second planar seating surfaces being in contact when the retainer structure is secured to the capture structure. 
   
   
       43 . The assembly of  claim 42  wherein the retainer structure has a second internal surface, the second internal surface and the first planar seating surface partially defining a recess, the second planar seating surface being disposed in the recess when the retainer structure is secured to the capture structure. 
   
   
       44 . The assembly according to  claim 35  wherein the retainer structure is sized and shaped to be loadable into the head through the open channel and the shank is sized and shape to be loadable into the head through the base opening. 
   
   
       45 . The assembly of  claim 44  wherein the head seating surface defines a recess shaped and sized for facilitating the insertion of the retainer structure into the cavity. 
   
   
       46 . The assembly according to  claim 35  further including a closure structure insertable into the head, the closure structure closing a top of the channel and adapted to operably urge the shank in a direction to frictionally fix the retainer external surface to the head seating surface, thereby rigidly positioning the shank body in a selected angle with respect to the head. 
   
   
       47 . The assembly of  claim 46  wherein:
 a) the head has upstanding spaced arms defining the open channel, each of the arms having guide and advancement structures on an inside surface thereof; and   b) the closure structure is disposable between the arms for closing the channel, the closure structure having an advancement structure for rotatably mating with the guide and advancement structures on the arms, thereby biasing the closure structure against a rod disposed in the channel when rotated in an advancement direction.   
   
   
       48 . The assembly of  claim 46  wherein the capture structure end has a dome sized and shaped to be adapted for engagement with a rod when received in the head and wherein the closure structure is adapted to operably urge the rod against the dome upon the closure structure being positioned in the head. 
   
   
       49 . A polyaxial bone screw assembly for surgical implantation and including a shank having a capture end and an elongate threaded body having an axis of rotation for being driven by rotation into a bone, and a head having an outward opening channel adapted to receive a rod within the channel, the head further having an inner cavity and a lower opening, the bone screw further including:
 a) a capture structure disposed on the shank capture end sized and configured to positioned to be located in the head when the shank extends through the lower opening, the capture structure having a tool engagement projection extending therefrom; and   b) a retainer structure separate from the shank and configured to couple with the capture structure in the head and thereafter polyaxially rotate with the shank capture structure within the head in a non locked configuration, the shank capture end extending above the retainer structure when joined therewith and having a tool seating surface extending radially from the projection and disposed coaxial with the shank body such that the tool seating surface is accessible to a tool when the retainer structure is mated with the capture structure, the capture structure being sized and shaped to extend into the channel when assembled in the head so as to receive a downward locking force from the rod and then transfer the downward force to the retainer structure to lock the retainer structure in place relative to the head when in a locked configuration.   
   
   
       50 . The improvement of  claim 49  wherein the capture structure receives the downward locking force directly from the rod. 
   
   
       51 . The improvement of  claim 49  wherein the at least one tool seating surface is disposed on the capture structure, the projection and the capture structure tool seating surface partially defining a recess adapted for receiving a driving tool engaged with the projection and wherein the driving tool is adapted to be in contact with the capture structure tool seating surface when driving the shank body into bone. 
   
   
       52 . The improvement of  claim 49  wherein the at least one tool seating surface is disposed on the retainer structure, the projection and the retainer structure tool seating surface partially defining a recess adapted for receiving a driving tool engaged with the projection and wherein the driving tool is adapted to be in contact with the retainer structure tool seating surface when driving the shank body into bone. 
   
   
       53 . The improvement of  claim 49  wherein the at least one tool seating surface is a first tool seating surface on the capture structure and a second tool seating surface on the retainer structure, the projection and the first and second tool seating surfaces partially defining a recess adapted for receiving a driving tool engaged with the projection and wherein the driving tool is adapted to be in contact with both the first and second tool seating surfaces when driving the shank body into bone. 
   
   
       54 . The improvement of  claim 49  wherein:
 a) the capture structure has an outer cylindrical surface with a first raised helically wound rib thereon; and   b) the retainer structure has an external surface and an inner cylindrical surface with a second raised helically wound rib thereon, the first helically wound rib configured to rotatably mate with the second helically wound rib to secure the retainer structure to the capture structure within the head cavity, and the retainer structure external surface enabling selective angular positioning of the shank with respect to the head.   
   
   
       55 . The improvement of  claim 54  wherein:
 a) the head has an inner substantially spherical seating surface partially defining the cavity; and   b) the retainer structure external surface is substantially spherical and in slidable mating engagement with the head seating surface.   
   
   
       56 . A polyaxial bone screw assembly method including:
 a) inserting a ring-like retainer structure into a cavity of a head;   b) inserting a capture structure of a bone screw shank separate from the retainer structure into the head such that the shank extends through a lower opening of the head and into the cavity thereof, the capture structure being integral with an elongate threaded shank body, the head channel opening outwardly and adapted to receive a rod within the channel, the head cavity being disposed between and communicating with both the channel and the shank receiving opening;   c) attaching the capture structure to the retainer structure within the cavity so as to move polyaxially together during positioning in a non locked configuration; and   d) applying a downward force to the shank so as to transfer the downward force to the retainer structure to lock the retainer structure and the shank in a selected angular position relative to the head in a locked configuration.   
   
   
       57 . The method of  claim 56  wherein applying the downward force includes directly applying the downward force. 
   
   
       58 . The method of  claim 56  further including:
 d) driving the shank body into bone by rotating the shank body with a tool engaged with a tool engagement formation disposed on at least one of the capture structure and the retainer structure.   
   
   
       59 . The method of  claim 56  further including:
 e) subsequently inserting a rod into the channel; and   f) biasing the rod against the capture structure by inserting a closure structure into the channel.   
   
   
       60 . A method of assembling a polyaxial bone screw including the steps of:
 a) providing a bone screw shank, head and ring-like retainer structure;   b) providing the shank with an upper threaded capture structure;   c) providing the retainer structure with a closed threaded bore;   d) providing the head with a central cavity and a lower opening connecting the cavity with an underside of the head;   e) loading the retainer structure into the cavity;   f) loading the shank capture structure into the cavity so that the shank extends through the head lower opening;   g) screwing the shank capture structure into the retainer structure threaded bore while within the head so that the shank and retainer structure polyaxially rotate together with each other relative to the head in an unlocked configuration; and   h) positioning the shank capture structure so as to receive a downward locking force and thereafter transfer the locking force to the retainer structure so as to lock the angular position of the shank and retainer structure relative to the head in a locked configuration.   
   
   
       61 . The method according to  claim 60 , wherein receiving the downward locking force includes directly receiving the downward locking force. 
   
   
       62 . The method according to  claim 60  including the steps of:
 a) providing the head with an upwardly open channel that communicates with the cavity; and   b) downloading the retainer structure through the channel into the cavity.   
   
   
       63 . A shank assembly for a bone screw mated for polyaxial movement with a retainer ring in a bone screw head, the shank having structure near an upper end thereof that is accessible when the shank and retainer ring are mated and that is adapted for operably mating with a tool to drive the shank into a bone, wherein the shank projection first receives a locking force in a locking configuration and then transfers the force to the retainer ring. 
   
   
       64 . The shank assembly of  claim 63  wherein the shank projection directly receives the locking force in the locking configuration. 
   
   
       65 . The shank assembly according to  claim 63  wherein the projection includes a base and the shank includes a recess surrounding the base adapted to receive the tool. 
   
   
       66 . The assembly according to  claim 65  wherein:
 a) said recess has an outer wall opposite the projection that is sized and shaped to be adapted to fit the contour of an outer surface of the tool.   
   
   
       67 . The assembly according to  claim 66  wherein:
 a) the outer wall is hexagonal.   
   
   
       68 . The assembly according to  claim 66  wherein:
 a) the outer wall is multi faceted in shape.