CA2494783C

CA2494783C - Polyaxial bone screw with spline capture connection

Info

Publication number: CA2494783C
Application number: CA002494783A
Authority: CA
Inventors: Roger P. Jackson
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-06-18
Filing date: 2004-04-05
Publication date: 2008-09-16
Anticipated expiration: 2024-04-05
Also published as: US8257396B2; ES2590954T3; CA2687595A1; US20180021067A1; WO2008153723A1; US6716214B1; AU2008262468A1; US20100016904A1; US7662175B2; AU2004254171A1; US11504164B2; US20100030280A1; US8636769B2; WO2005002468A3; US11925392B2; US20080234761A1; JP2010524637A; US11000314B2; US20160183984A1; CA2494783A1

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.

Description

POLYAXIAL BONE SCREW WITH SPLINE CAPTURE CONNECTION
Background of the Invention 1 The present invention is directed to a polyaxial bone

2 screw for use in spinal surgery and the like and especially

3 to such a screw adapted to receive a rod member and secure

4 the rod member to a vertebra or the like.

Many spinal surgery procedures require securing various 6 implants to bone and especially to vertebrae along the 7 spine. For example, elongate rods are often required that 8 extend along the spine to provide support to vertebrae that 9 have been damaged or weakened due to injury, disease or the like. Such rods must be supported by certain vertebra and 11 support other vertebra. The most common mechanism for 12 providing such structure is to implant bone screws into 13 certain bones which then in turn support the rod or are 14 supported by the rod. Bone screws of this type may have a fixed head relative to a shank thereof. In the fixed bone 16 screws, the head cannot be moved relative to the shank and 17 the rod must be favorably positioned in order for it to be 18 placed within the head. This is sometimes very difficult or 19 impossible to do so polyaxial bone screws are commonly used.

1 The polyaxial bone screws allow rotation of the head about 2 the shank until a desired rotational position is achieved 3 for the head relative to the shank after which the rod can 4 be inserted and the position of the head eventually locked with respect to movement relative to the shank.

6 The present invention is directed to such swivel head 7 type bone screws and, in particular, to swivel head bone 8 screws having an open head that allows placement of the rod 9 member within the head and then subsequent closure by use of a closure top, plug or the like to capture the rod in the 11 head of the screw.

12 Because such implants are for placement within the 13 human body, it is always desirable for the implant to have 14 as little effect on the body as possible. Consequently, it is quite desirable for the implants to have a relatively 16 small profile both in height and width. It is also 17 desirable that the implants be lightweight.

18 Furthermore, it is desirable that the swivel head 19 implants be unlikely to unintentionally disassemble within the body. It is very undesirable for pieces of the implant 21 to be free to move around within the body after surgery is 22 completed and it also assures that the implant retains an 23 ability to correct the structural problem for which it was 24 implanted. Furthermore, if the implant should slip or 1 become loose for some reason, it is still desirable for all 2 of the parts to remain together and not separate.

3 Consequently, it is desirable for there to be a 4 lightweight, low profile polyaxial bone screw which assembles in such a manner that each subsequent piece locks 6 proceeding pieces within the overall structure, so that 7 there is less likelihood that the various pieces of the 8 structure will undesirably disassemble.

Summary of the Invention 12 The present invention is directed to a polyaxial bone 13 screw that comprises a shank, a head and a retainer ring 14 that operably cooperate with each other. The bone screw is designed to allow the shank to be locked or secured in a 16 selected angular configuration with respect to the head, 17 while the head receives a rod member and while the shank is 18 implanted in a bone, such as a vertebra or vertebral body.
19 The shank has an implant body which includes an external helically wound thread that is in turn attached by 21 a neck to a capture end with a capture or connector type 22 structure. The capture structure is positioned outside the 23 bone in use and has a radiused and cylindrically shaped 24 radially outer surface that has at least one radially 1 outwardly extending non helically wound projection or spline 2 thereon. The capture structure also has an upper axially 3 aligned and radiused dome that protrudes above the remainder 4 of the shank and above the ring during use to manipulate the shank and to contact the rod. Further, in some embodiments 6 the shank includes off axis apertures, grooves, side slots 7 or the like for use by an installation tool with a mating 8 configured head for driving and rotating the shank into the 9 bone.

The head has a generally cylindrical shaped profile 11 with an upwardly open U-shaped channel formed therein so as 12 to effectively produce a lower base with two upstanding and 13 spaced arms. The inner surfaces of the arms have a 14 threadform thereon or another suitable guide and advancement structure such as a helically wound flangeform for use in 16 closing the upper part of the channel. Located in the 17 interior of the base and coaxially aligned with the head is 18 a chamber having an interiorly facing partial spherical 19 shaped surface. The chamber further opens onto a bottom surface of the head through a head lower wall bore forming a 21 constricted or restrictive neck sized and shaped to allow 22 passage of the capture structure therethrough.

23 The retainer ring includes an external partial 24 spherical or hemispherical surface that is sized and shaped 1 to be seated in and slidably engage the partial spherical 2 surface within the head, both having approximately the same 3 radius of generation. The ring also has an internal, 4 centrally located and axially extending ring bore sized and shaped to receive the capture structure of the shank 6 therethrough. Further, the ring has a series of axially 7 extending channels positioned about and opening into the 8 central bore that are sized and shaped to allow sliding 9 passage of the shank splines entirely through the ring so that the shank can be inserted through the ring while the 11 ring is positioned within the chamber in the head. The 12 channels are not helically wound about the bore and 13 preferably extend vertically or parallel to the axis of the 14 ring. The ring further includes a set of recesses that are circumferentially spaced from the channels and that open 16 onto the upper part of the ring and into the bore, but do 17 not pass entirely through the ring and that can be entered 18 by the splines by drawing the shank with the splines thereon 19 axially downwardly with respect to the ring. In this manner, the splines can be passed upwardly or uploaded 21 through the ring by sliding through the channels in 22 conjunction with the remainder of the shank capture and 23 after sliding completely through the bore, the shank is then 24 rotated a certain number of degrees relative to the head,

5 -------- - ------1 and then drawn back downwardly or downloaded so that the 2 splines encounter and engage the recesses wherein the 3 splines are captured by the ring. The splines preferably 4 have a wedge-shaped surface thereon which pushes not only downwardly, but radially outward against the retainer or

6 capture ring when force is applied to the top of the shank.

7 During assembly, the ring is placed through the U-

8 shaped channel into the chamber having the partial spherical

9 surface and then rotated so that the ring hemispherical surface mates with and slidably engages the head partial 11 spherical surface. Subsequently, the shank capture 12 structure is uploaded into and extended through the ring 13 central bore, while the splines pass through the channels.
14 The shank is then rotated relative to the ring and then the shank is moved in an axially reverse direction opposed to 16 uploading while the splines are positioned over the recesses 17 so as to be aligned with the recesses and not aligned with 18 the channels and so that the splines then enter the 19 recesses. The ring with connected shank effectively thereafter form a ball and socket joint with the head and 21 allow free rotation to a selected angular configuration 22 until later locked in the selected configuration. The 23 shank, head and ring are then placed in a bone by screwing 24 the shank body into the bone using the apertures on the top 1 of the shank or alternative structure such as grooves or 2 faceted surfaces on the outside of the portion of the shank 3 extending above the ring.

4 Thereafter, a rod is placed in the U-shaped channel and captured therein by closing the channel by use of a closure 6 top or plug having a threadform or other external guide and 7 advancement structure that mates with and advances along 8 mating guide and advancement structure of the arms of the 9 head, when the closure top is rotated. Preferably, the closure top also includes a break-off head that provides 11 purchase for a tool for rotation and torquing of the closure 12 top to a preselected torque and that such torque is 13 transferred and applied as pressure against the rod received 14 in the head. Once the preselected torque is achieved, the break-off head breaks away from the closure top. Under 16 pressure from the closure top, the rod pushes against the 17 dome of the shank that extends above the ring and thereby 18 urges the splines downwardly. Because of the wedge shaped 19 structure of the splines, the splines push both downwardly and outwardly upon the retainer or capture ring, when force 21 is applied to the dome, so as to frictionally engage and 22 positively seat the retaining ring in the cavity and prevent 23 further rotation in conjunction with the shank dome 24 frictionally engaging the rod under pressure. In 1 particular, the hemispherical surface of the ring abuttingly 2 and frictionally mates with the integral hemispherical 3 interior facing surface of the head, while the dome 4 frictionally mates with the rod under pressure from the rod so as to lock the shank and ring in a selected angular 6 configuration relative to the head. The shank, in this 7 manner, can be locked in a configuration selected from an 8 infinite number of angular configurations with respect to 9 the head. Once fully assembled in this manner, unless a part breaks into pieces, the shank cannot disengage from the 11 capture ring and the head without disassembly of the device 12 by reversing the process or breaking the parts.

14 Objects and Advantages of the Invention 16 Therefore, the objects in the present invention are: to 17 provide a polyaxial bone screw having a bone implantable 18 shank that can be locked in a fixed position relative to a 19 head of the bone screw; to provide such a bone screw having a capture or retaining ring having a partial external 21 hemispherical surface that seats within a partial internal 22 spherical shaped chamber surface within and integrally 23 formed with a head of the bone screw to form a ball and 24 socket joint and wherein the shank is securable to the 1 retaining ring; to provide such a bone screw wherein the 2 shank has at least one spline that extends radially outward 3 from a capture end thereof and wherein the retaining ring 4 has a central bore that receives the capture end while a channel opening into the bore allows the spline to slide 6 through the ring so as to pass above the ring, at which time 7 the shank can be rotated a select number of degrees and 8 further wherein the retaining ring has a capture recess that 9 receives the spline on further downward or reverse movement along the axis of the shank relative to the retainer ring;
11 to provide such a bone screw wherein the shank has an 12 upwardly protruding radiused dome which has a radius that in 13 one embodiment is substantially less than the radius of the 14 external hemispherical surface on the retainer ring and that extends upwardly within the head chamber so as to reduce 16 height of the screw head and further, is operably positioned 17 so as to engage a rod member received in the head so as to 18 receive downward pressure from the rod during assembly; to 19 provide such a bone screw wherein a closure top is used to close a channel in the bone screw head after receiving the 21 rod and to apply pressure to the rod member that in turn, 22 exerts pressure on the dome of the shank so as to urge each 23 spline into an abutting and tight relationship with the 24 retaining ring and to urge the retaining ring both 1 downwardly and radially outwardly, so that the external 2 hemispherical surface on the retaining ring more completely 3 contacts and frictionally engages the internal spherical 4 surface within the chamber of the head thereby providing improved mechanical fixation to prevent further rotation of 6 the shank relative to the head; to provide such a bone screw 7 which has a comparatively low profile and which is 8 comparatively light in weight; to provide such a bone screw 9 that resists disassembly thereof except by removal of the closure top; to provide such a bone screw wherein the 11 closure top can be removed by the surgeon should disassembly 12 be desired at which time the entire structure can be easily 13 and quickly disassembled and removed from the bone, if 14 necessary; to provide such a bone screw wherein the shank is locked in position relative to the head during usage in a 16 locked or fixed configuration; to provide such a bone screw 17 wherein the shank cannot disassemble from the head and the 18 retaining ring once the screw is fully assembled except if 19 the closure top is removed and the device is disassembled by the surgeon; to provide such a bone screw which is easy to 21 use and extremely effective for the intended usage thereof.
22 It is a further object of the invention for there to be 23 a polyaxial bone screw comprising a shank having a body 24 adapted to be implanted in a bone and a capture structure 1 extending from said body; said capture structure including 2 at least one spline that extends radially outward therefrom;
3 a head having a channel adapted to receive a rod member and 4 a base having a cavity with a partial spherical surface and communicating with said channel through an upper opening;

6 said cavity communicating with an exterior of said head 7 through a lower opening sized and shaped to receive said 8 shank capture structure therethrough; a retainer ring that 9 is receivable into said head cavity and having an external partial spherical surface sized and shaped to be seated on 11 said head partial spherical surface; said ring having a 12 central bore with an axial pass through ring channel opening 13 into said bore for each of said at least one spline 14 respectively; said ring bore and said ring channel being sized and shaped to allow said shank capture structure to 16 axially pass therethrough and then be rotated; said 17 retainer ring also having a capture recess for each of 18 said at least one spline sized and shaped to receive and 19 capture a respective spline when said shank is subsequently moved axially downward relative to said 21 retainer ring such that said capture structure is captured 22 by said ring, but said shank is rotatable relative to said 23 head in an unlocked assembly configuration; and a closure 24 top for operably urging said shank downward so as to frictionally engage said ring surface with said head 26 surface so as to lock said shank I in position relative to said head in a locked configuration.
2 It is a still further object of the invention that in a 3 polyaxial bone screw having a head and a shank, the 4 improvement comprising further including a capture ring sized and shaped to be received within said head and having 6 a central bore with at least one axially aligned channel 7 extending radially outward from said bore; and said shank 8 having a capture end having a radially outward extending 9 spline associated with each of said at least one axially aligned channel; said shank capture end being sized and 11 shaped to pass through said bore with each spline, such 12 that each spline is thereafter positioned above said ring;
13 said shank being thereafter axially rotatable so that each 14 spline is non aligned with a respective channel thereby capturing said shank relative to said ring.

16 It is a still further object of the invention that in a 17 polyaxial bone screw having a shank with a threaded body 18 portion and a capture component joinable by a connection 19 mechanism; the improvement wherein said capture mechanism comprises a radially outward extending spline located on a 21 capture end of said shank body portion; a passthrough bore 22 located in said capture component and including a radially 23 outward extending channel; and said bore being sized and 24 shaped to slidingly receive and allow passage of said shank 1 capture end with said spline through said bore and channel 2 in an aligned configuration; said shank body portion being 3 thereafter axially rotatable relative to said capture 4 component to position said spline in a non aligned configuration wherein said spline will not pass through said 6 channel.

7 It is a still further object of the invention that a 8 polyaxial bone screw having a head; a shank with a threaded 9 body axially adjoining a capture end; said capture end having a circular cross section with at least one non 11 helically wound and radially outward extending spline; and a 12 capture member having a bore with a radially outward 13 positioned channel; said bore and said channel being sized 14 and shaped to slidingly receive said shank capture end and spline when in an aligned configuration; said shank being 16 axially rotatable relative to said capture member after 17 passage of said capture end and spline through said bore and 18 channel to a non aligned configuration wherein said spline 19 is not aligned with said channel and in a non aligned configuration thereby joining said shank to said capture 21 member.

22 It is a still further object of the invention that a 23 polyaxial bone screw comprising a head having a channel 24 adapted to receive an elongate rod and having a lower 1 aperture; a shank having a lower portion adapted to be 2 implanted in a bone of a patient and an upper portion;
3 said shank being sized and shaped to be uploaded into said 4 head through said aperture; and said shank upper portion being sized and shaped so as to extend into said channel 6 after said shank is received in said head.

8 It is a still further object of the invention that in 9 a polyaxial bone screw having a shank and a head with an upward opening receiving channel and a lower opening; the 11 improvement comprising: a) said shank being sized and 12 shaped to be loaded upwardly through said head lower 13 opening; said shank being sized and shaped to extend into 14 said channel after being received in said head.
16 It is a still further object of the invention that a 17 polyaxial bone screw and rod assembly comprising a head 18 having a channel adapted to receive a rod and having a 19 lower aperture; a shank having a threaded lower portion adapted to be implanted in a bone and an upper portion 21 with a first capture structure; said shank upper portion 22 being sized and shaped to be uploaded through said head 23 lower aperture; a retaining structure having a second 24 capture structure that mates with and secures to said first capture structure inside said head; said retaining 26 structure being non integral with said shank; said 27 retaining structure being downloaded from a top of said 28 head; the rod adapted to be received in said channel; and 29 said shank upper portion further including an upper convex surface sized, shaped and positioned such that when said 31 bone screw is fully assembled and said rod is located in 32 said channel, said convex surface engages said rod to urge 33 said shank into a non moveable configuration relative to 1 said head.

3 It is a still further object of the invention that in 4 a polyaxial bone screw having a shank and a head wherein said head includes a rod receiving channel; the 6 improvement comprising: a) said shank being sized and 7 shaped to allow uploading of said shank into said head 8 from below; and b) a retaining structure non integral with 9 said head and said shank for capturing said shank in said head; said shank extending into said channel after 11 assembly of said shank with said head.

13 It is a still further object of the invention that in 14 a polyaxial bone screw having a shank and a head wherein said head includes a rod receiving channel; the 16 improvement comprising said shank being sized and shaped 17 to allow for said shank to be uploaded into said head; and 18 said shank having an upper engagement region sized and 19 shaped to project into said channel after said shank is loaded into said head.

22 It is a still further object of the invention that in 23 a polyaxial bone screw having a shank and a head wherein 24 said head includes a rod receiving channel; the improvement comprising: a) said head having a lower 26 aperture and said shank being sized and shaped so as to 27 allow uploading of an upper portion of said shank through 28 said aperture into said head; and b) retaining structure 29 that is non integral with said shank and loaded separately into said head; said retaining structure mating with and 31 capturing said shank in said head and forming a combined 32 assembly with said shank; and wherein c) a portion of said 33 assembly extends into said channel.

2 It is a still further object of the invention that in 3 a polyaxial bone screw having a shank and a head; the 4 improvement comprising: a) said head having a lower aperture and said shank being sized and shaped so as to 6 allow uploading of an upper portion of said shank through 7 said aperture into said head; b) retaining structure that 8 is non integral with said shank and loaded separately into 9 said head; said retaining structure mating with and capturing said shank in said head; and c) said retaining 11 structure being uploaded into said head prior to said 12 shank.

14 It is a still further object of the invention that in a polyaxial bone screw having a head and a shank wherein 16 said head includes a rod receiving channel; the 17 improvement comprising: a) said head has an inner chamber 18 and a lower aperture having a first radius; b) said shank 19 having an upper portion with a second radius less than said first radius such that said shank upper portion is 21 insertable through said aperture; c) retaining structure 22 within said chamber and independent of said head that is 23 sized and shaped to mate with and be secured to said shank 24 upper portion; said retaining structure and said shank upper portion being joined in said head to form an 26 assembly; and d) a portion of said assembly extending into 27 said channel.

29 It is a still further object of the invention that in a polyaxial bone screw having a shank and a head having an 31 inner chamber with a radiused surface and also having a 32 lower aperture wherein said head includes a rod receiving 33 channel; the improvement comprising: a) said chamber 1 surface having a larger radius than said aperture; b) said 2 shank having an upper portion that has a smaller radius 3 than said aperture to allow said shank to be uploaded 4 through said aperture; c) a retaining device that loads separately from said shank into said chamber and 6 captures said shank in said chamber to form an assembly;
7 said retaining device having a lower surface sized and 8 shaped to slidingly mate and rotate with said chamber 9 surface during positioning; and d) a portion of said assembly extending into said channel.

12 It is a still further object of the invention that a 13 method of implanting a bone screw in a patient comprising 14 the steps of providing a bone screw head having a lower aperture and an implant receiving channel; providing an 16 elongate shank having a lower threaded portion and an 17 upper portion with said upper portion having an implant 18 engagement end; loading said shank upper portion into said 19 head from below and through said aperture; implanting said shank into a bone of a patient; and placing said implant 21 into said channel so that said shank engagement end abuts 22 against said implant, so as to fix the position of said 23 shank relative to said head.

It is a still further object of the invention that a 26 method of implanting a bone screw in a patient comprising 27 the steps of providing a bone screw head having a lower 28 aperture and a rod receiving channel; providing an 29 elongate shank having a lower threaded portion and an upper portion with said upper portion having a rod 31 engagement region; loading said shank upper portion into 32 said head from below through said aperture; capturing said 33 shank inside said head while allowing pivoting of said 1 shank relative to said head; implanting said shank into a 2 bone of a patient; moving said head into a selected 3 angular configuration with respect to said shank; placing 4 said rod into said channel so that said rod engagement - 17a-1 region abuts against said rod; installing a closure in 2 said head that closes said channel and biases against said 3 rod so as to bias said rod against said rod engagement 4 region and lock said head in said selected angular configuration relative to said shank.

7 It is a still further object of the invention that in 8 a method of implanting a polyaxial bone screw in a patient 9 wherein the bone screw has a shank and a head that has a channel adapted to receive a rod; the improvement 11 comprising uploading said shank into said head so as to be 12 captured therein; providing said shank with an upper 13 engagement end; and positioning said shank upper 14 engagement end in said channel so as to abut against a rod placed within said charinel.

17 It is still a further object of the invention that 18 use of an elongate shank having a lower threaded portion 19 and an upper portion with said upper portion having an implant engagement end and a bone screw head having a 21 lower aperture communicating with an implant receiving 22 channel for implanting a bone screw in a patient, wherein 23 said upper portion of said shank is adapted to be loaded 24 into said bone screw head from below and through said aperture and wherein said shank extends into said channel 26 when said shank upper end is in said head.

28 It is still a further object of the invention that 29 use of a bone screw head for implanting a bone screw in a patient, said bone screw head having a lower aperture 31 communicating with a rod receiving channel and an elongate 32 shank having a lower threaded portion for implantation in 33 a bone and an upper portion with said upper portion having 1 a rod engagement region extending into said channel when 2 said upper portion is in said head, wherein said shank 3 upper portion is adapted to be loaded into said head from 4 below through said aperture while allowing pivoting of said shank relative to said head; and wherein said head 6 comprises a closure that closes said channel and biases 7 against said rod when received in the channel so as to 8 bias said rod against said rod engagement region and lock 9 said head in said selected angular configuration relative to said shank.

12 It is still a further object of the invention that 13 use of a bone screw having a shank and a head that has a 14 channel adapted to receive a rod for implanting the bone screw in a patient, the shank adapted to be uploaded into 16 the head, wherein said shank comprises an upper engagement 17 end extending into the channel when the bone screw is 18 fully assembled, such that the upper engagement end is 19 adapted to abut against a rod placed within said channel.

21 Other objects and advantages of this invention will become 22 apparent from the following description taken in 23 conjunction with the accompanying drawings wherein are set 24 forth, by way of illustration and example, certain embodiments of this invention.

27 The drawings constitute a part of this specification and 28 include exemplary embodiments of the present invention and 29 illustrate various objects and features thereof.

- 18a-1 Brief Description of the Drawings 2 Fig. 1 is an exploded perspective view of three 3 elements of a polyaxial bone screw in accordance with the 4 present invention, including a shank, a head, and a retaining ring.

6 Fig. 2 is an enlarged top plan view of the retaining 7 ring.

8 Fig. 3 is an enlarged perspective view of the retaining 9 ring.

Fig. 4 is an enlarged side elevational view of the 11 retaining ring.

12 Fig. 5 is an enlarged bottom plan view of the retaining 13 ring.

14 Fig. 6 is an enlarged cross-sectional view of the head, taken along line 6-6 of Fig. 1, illustrating the retaining 16 ring being inserted into the head.

17 Fig. 7 is an enlarged cross-sectional view of the head 18 similar to Fig. 6, showing the retaining ring seated in the 19 head.

Fig. 8 is a cross-sectional view of a vertebra 21 illustrating the shank implanted therein.

22 Fig. 9 is an enlarged and fragmentary perspective view 23 of the shank, head and retainer ring during assembly and 24 just prior to the retainer ring being placed over the shank.

1 Fig. 10 is an enlarged, fragmentary and perspective 2 cross-sectional view of the head similar to Fig. 6, 3 illustrating splines on a capture end of the shank that have 4 been inserted through channels in the retainer ring and are positioned upwardly in the head above the retainer ring.

6 Fig. 11 is a cross-sectional view of the head, similar 7 to Fig. 10, showing the upper capture end of the shank with 8 the splines lowered into receiving recesses in the ring and 9 positioned therein.

Fig. 12 is a cross sectional view of the head and a top 11 plan view of the shank and ring corresponding to the 12 positioning shown in Fig. 10.

13 Fig. 13 is a cross sectional view of the head and a top 14 plan view of the shank and ring corresponding to the positioning shown in Fig. 11.

16 Fig. 14 is a side elevational view of the head, ring 17 and shank, illustrating the shank swinging or rotating from 18 one position shown in solid lines to a second position shown 19 in phantom lines.

Fig. 15 is a fragmentary and partially exploded view of 21 a complete polyaxial bone screw assembly, prior to final 22 assembly and illustrating a rod received in the head and a 23 closure top with a break-off head, prior to the closure top 24 being rotatably inserted into the head.

1 Fig. 16 is a fragmentary and enlarged front elevational 2 view of the bone screw assembly fully assembled and 3 illustrating the head with the rod received therein and with 4 the closure top fully inserted and biasing against the rod that in turn biases against the top of the shank.

6 Fig. 17 is an enlarged and fragmentary cross-sectional 7 view of the bone screw assembly with rod inserted therein, 8 taken along line 17-17 of Fig. 16.

9 Fig. 18 is an enlarged cross-sectional view of the vertebra, head, rod and closure top, taken along line 18-18 11 of Fig. 17 showing the shank implanted in the vertebra and 12 with the bone screw assembly in a completely assembled and 13 operational configuration with the shank locked in an angled 14 orientation with respect to the head.

Fig. 19 is a perspective view of a modified retainer 16 ring of a first modified embodiment in accordance with the 17 present invention.

18 Fig. 20 is a perspective view of a second modified 19 embodiment of the present invention illustrating a cannulated shank having four splines and a hex tool 21 engageable head for manipulating the shank.

22 Fig. 21 is a perspective view of a ring for use in 23 accordance with the second modified embodiment of the 24 invention and the shank of Fig. 20.

1 Detailed Description of the Invention 3 As required, detailed embodiments of the present 4 invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely 6 exemplary of the invention, which may be embodied in various 7 forms. Therefore, specific structural and functional 8 details disclosed herein are not to be interpreted as 9 limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to 11 variously employ the present invention in virtually any 12 appropriately detailed structure.

13 The reference number 1 generally represents a polyaxial 14 bone screw apparatus or assembly in accordance with the present invention operably utilized by implantation into a 16 vertebra 2 and in conjunction with a longitudinal member or 17 rod 3 so as to operably secure the rod 3 in a fixed position 18 relative with respect to the vertebra 2.

19 The fully assembled bone screw assembly 1 comprises a shank 6, a head 7, a retainer ring 8 and a closure top-9.
21 The shank 6 is perhaps best seen in Figs. 1 and 8. The 22 shank 6 is elongate and has a lower body 15 ending in a tip 23 16. The shank body 15 has a helically wound bone 24 implantable thread 17 extending from near the tip 16 to near 1 the top 18 of the body 15 and extending radially outward 2 therefrom. During use, the body 15 utilizing the thread 17 3 is implanted into the vertebra 2, as is seen in Fig. 18.

4 The shank 6 has an elongated axis of rotation generally identified by the reference letter A. It is noted that the 6 reference to the words top and bottom as used herein refers 7 to the alignment shown in the various drawings, as well as 8 the normal connotations applied to such devices, and is not 9 intended to restrict positioning of the assembly 1 in actual use.

11 Axially extending outward and upward from the shank 12 body 15 is a neck 20 of reduced radius as compared to the 13 adjacent top 18 of the body 15. Further extending axially 14 and outwardly from the neck 20 is a capture end or structure 21 operably providing a connective or capture structure free 16 from the bone or vertebra 2 for joining with the head 7.

17 The capture structure 21 has a radially outer cylindrical 18 surface 22. The cylindrical surface 22 has at least one 19 non-helically wound and radially outward extending projection or spline 24 that extends beyond the surface 22.
21 In the embodiment shown in Figs. 1 through 18, the capture 22 structure 21 has three such splines 24. The splines 24 are 23 located near an upper end 25 of the shank 6 and are equally 24 circumferentially centered and spaced thereabout so as to be 1 centered at approximately 120 degree intervals relative to 2 each other. Each of the splines 24 has a triangular shaped 3 profile and a front wedge forming face 27 that slopes 4 downwardly and radially inwardly from near the upper end 25 of the shank 6. Also located on the shank upper end 25 is a 6 centrally located, axially extending and upwardly directed 7 projection or dome 29 that is centrally radiused so as to 8 have a first radius.

9 The shank upper end 25 still further includes at least one tool engagement aperture for engagement by a tool 11 driving head (not shown) that is sized and shaped to fit 12 into the apertures for both driving and rotating the shank 6 13 into the vertebra 2. In the illustrated embodiment, a pair 14 of apertures 31 located in spaced relationship to each other, the dome 29 and the shank axis of rotation A are 16 located on the shank upper end 25. The apertures 31 extend 17 into the shank capture structure 21 parallel to the axis A.
18 It is foreseen that various numbers of apertures, slots or 19 the like may be utilized in accordance with the invention for engaging the driving tool of suitable and similar mating 21 shape, or that the outer surface of the upper axial 22 projection can be grooved or formed with a faceted surface 23 that can be driven by a mating tool that goes over the 24 surface.

1 The head 7 has a generally cylindrical shaped profile, 2 as is seen in Fig. 1, although the head 7 is not a solid 3 cylinder. The head 7 has a base 33 with a pair of 4 upstanding arms 34 and 35 forming a U-shaped channel 38 between the arms 34 and 35 with a lower seat 39 having 6 substantially the same radius as the rod 3 for operably 7 snugly receiving the rod 3. Each of the arms 34 and 35 has 8 an interior surface 41 that includes a partial helically 9 wound guide and advancement structure 42. In the illustrated embodiment, the guide and advancement structure 11 42 is a partial helically wound flangeform which will mate 12 under rotation with a similar structure on the closure top 13 9, as described below. However, it is foreseen that the 14 guide and advancement structure 42 could alternatively be a V-shaped thread, a buttress thread, a reverse angle thread 16 or other thread like or non-thread like helically wound 17 advancement structures for operably guiding under rotation 18 and advancing the closure top between the arms 34 and 35.

19 Tool engaging apertures 44 are formed on the outsides of the arms 34 and 35 for holding the head 7 during assembly.

21 A chamber or cavity 47 is located within the head base 22 33 that opens upwardly into the U-shaped channel 38. The 23 cavity 47 includes a partial spherical shaped surface 48, at 24 least a portion of which forms a partial internal 1 hemispherical seat 49 for the ring 8, as is described 2 further below. A bore 52 further communicates between the 3 cavity 47 and the bottom exterior of the base 33 and is 4 coaxial with a rotational axis B of the head 7. The bore 52 at least partially defines a restrictive neck 54 that has a 6 radius which is smaller than the radius of the ring 8, as 7 will be discussed further below, so as to form a restrictive 8 constriction at the location of the neck 54 relative to the 9 retainer ring 8 to prevent the ring 8 from passing between the cavity 47 and the lower exterior of the head 7. A bevel 11 55 extends between the neck 54 and the bottom exterior of 12 the base 33. The hemispherical shaped surface 48 has a 13 second radius associated therewith.

14 The retainer ring 8 which is best seen in Figs. 2 through 5 has an operational central axis which is the same 16 as the elongate axis A associated with the shank 6, but when 17 the ring 8 is separated from the shank 2, the axis of 18 rotation is identified as axis C, such as in Fig. 4. The 19 retainer ring 8 has a central bore 57 that passes entirely through the retainer ring 8 from a top surface 58 to a 21 bottom surface 59 thereof. The bore 57 is sized and shaped 22 to fit snugly but slidably over the shank capture structure 23 cylindrical surface 22 in such a manner as to allow sliding 24 axial movement therebetween under certain conditions, as 1 described below. Three axially aligned channels 60 are 2 spaced from the axis C and extend radially outward from the 3 bore 57 and into the wall of the retainer ring 8 so as to 4 form three top to bottom grooves or slots therein. Backs 61 of the channels 60 are the same radial distance from the 6 axis C as the distance the outermost portion of the splines 7 24 extend from the axis A of the shank 6. The channels 60 8 are also circumferentially angularly spaced equivalent to 9 and have a width that corresponds with the splines 24. In this manner, the shank capture structure 21 can be uploaded 11 into the ring 8 by axially sliding the capture structure 21 12 through the ring central bore 57 whenever the splines 24 are 13 aligned with the channels 60 or are in an aligned 14 configuration, as seen in Fig. 12.

The retainer ring 8 also has three capture partial 16 slots, receivers or recesses 62 which extend radially 17 outward from the upper part the bore 57 and that do not 18 extend the entire length from top to bottom of the retainer 19 ring 8, but rather only open on the top surface 59 and extend partly along the height of the ring 8 thereof. The 21 recesses 62 are sized and positioned and shaped to receive 22 the splines 24 from above when the splines 24 are in a non-23 aligned configuration relative to the channels 60. That is, 24 each of the recesses 62 has a width that approximates the 1 width of the splines 24 and has a mating wedge engaging 2 surface 64 that is shaped similar to the spline wedge 3 forming faces 27, so that the splines 24 can be slidably 4 received into the recesses 62 from above by axially translating or moving the shank 6 downward relative to the 6 ring 8 when the splines 24 are positioned above the recesses 7 62 in a recess aligned configuration.

8 In some embodiments, the wedge engaging faces 64 slope 9 slightly greater than the wedge forming faces 27 on the splines 24 so that there is additional outward wedging that 11 takes place when the splines 24 are urged downwardly into 12 the recesses 62, as further discussed below.

13 In this manner the shank capture structure 21 can be 14 uploaded or pushed upwardly through the retainer ring central bore 57 so as to clear the top 58 of the retainer 16 ring 8, rotated approximately 60 degrees and then downloaded 17 or brought downwardly so that the splines 24 become located 18 and captured in the recesses 62. Once the splines 24 are 19 seated in the recesses 62 the shank 6 cannot move further axially downward relative to the ring 8. Preferably, the 21 retainer ring 8 is constructed of a metal or other material 22 having sufficient resilience and elasticity as to allow the 23 ring 8 to radially expand slightly outward by downward 24 pressure of the splines 24 on the recesses 62 under pressure ---- ------ - -1 from structure above, as will be discussed further below.

2 This produces a slight outward radial expansion in the ring 3 8 at the location of the recesses 62.

4 The ring 8 has a radially outer partial hemispherical shaped surface 65 sized and shaped to mate with the partial 6 spherical shaped surface 48 and having a third radius 7 approximately equal to the second radius associated with the 8 surface 48. The ring third radius is substantially larger 9 than the first radius associated with the dome 29 and also substantially larger than the radius of the neck 54.

11 The longitudinal member or elongate rod 3 can be any of 12 many different types of implants utilized in reconstructive 13 spinal surgery and the like, but is normally a cylindrical 14 elongate structure having a cylindrical surface 66 of uniform diameter. The rod 3 is preferably sized and shaped 16 to snugly seat near the bottom of the U-shaped channel 38 17 and, during normal operation, will be positioned slightly 18 above the bottom of the channel 38. In particular, the rod 19 3 normally engages the shank dome 29, as is seen in Fig. 16 and urges the dome 29 and, consequently, the shank 6 21 downwardly when the entire assembly 1 is fully assembled.
22 The closure top 9 can be any of the variety of 23 different types of closure tops for use in conjunction with 24 the present invention with suitable mating structure on the 1 upstanding arms 34 and 35. The illustrated closure top 9 2 has a generally cylindrical shaped base 67 with an upwardly 3 extending break-off head 68. The base 67 includes a 4 helically wound guide and advancement structure 71 that is sized, shaped and positioned so as to engage the guide and 6 advancement structure 42 on the arms 34 and 35 to allow the 7 closure top 9 to be rotated into the head 7 and, in 8 particular, to close the top of the U-shaped channel 38 to 9 capture the rod 3, see Fig. 16, preferably without splaying of the arms 34 and 35. The closure top 9 also operably 11 biases against the rod 3 by advancement and applying 12 pressure to the rod 7 under torquing, so that the rod 3 is 13 urged downwardly against the shank dome 29. Downward 14 biasing of the shank dome 29 operably produces a frictional engagement between the rod 3 and dome 29 and also urges the 16 splines 24 downwardly to both bias downwardly and radially 17 outwardly against the retainer ring 8, so as to snugly and 18 frictionally seat the retainer ring external hemispherical 19 surface 65 into and quite tightly against the partial internal spherical surface 48 of the head 7 and further so 21 as to lock the shank 6 and retainer ring 8 in a fixed 22 position relative to the head 7.

23 The closure top break-off head 68 is secured to the 24 base 67 at a neck 73 that is sized and shaped so as to break 1 away at a preselected torque that is de6igned to properly 2 seat the retainer ring 8 in the head 7. The break-off head 3 68 includes an external faceted surface 75 that is sized and 4 shaped to receive a conventional socket head of a driving tool (not shown) to rotate and torque the closure top 9.
6 The break-off head 68 also includes a central bore 77 and 7 grooves 78 for operably receiving the manipulating tools.
8 The closure top 9 also includes removal structure 9 comprising a pair of off axis pass through apertures 81 that extend from top to bottom of the base 67. The apertures 81 11 are located parallel to an axis of rotation axis D of the 12 closure top 9, but are radially spaced away therefrom. The 13 apertures 81 become accessible from the top of the base 67 14 after the break-off head 68 breaks away from the base 67, as is seen in Fig. 18. The apertures 81 are designed to 16 receive a tool having a face that mates with and is 17 insertable into the apertures 81 for rotating the closure 18 top base 67 subsequent to installation so as to provide for 19 removal, if necessary.

While the embodiment illustrated in Figs. 1 through 18 21 includes three of spline 3, it is foreseen that a shank 6 22 with a single spline would be operable within the scope of 23 the invention. However, in some embodiments additional 24 splines may provide a more even distribution of force upon the 1 ring 8 and reduce the likelihood of failure because of hoop 2 strain or the like. Paired and opposed splines in certain 3 embodiments may provide a more even distribution of forces.
4 While any number of splines are foreseen as possible for use under the present invention, the requirement that the 6 splines must get smaller as their number gets larger, limits 7 the maximum number at some point. However, the concept 8 appears viable until that point is reached. It is also 9 noted that additional channels and recesses allow the ring to be more elastic in certain embodiments.

11 When the polyaxial bone screw assembly 1 is placed in 12 use in accordance with the invention the retainer ring 8 is 13 normally first slid through the head U-shaped channel 38, as 14 is shown in Fig. 6, and into and seated in the chamber 47, as is seen in Fig. 6. Thereafter, the retainer ring 8 is 16 rotated 90 degrees so as to be coaxial with the head 7 and 17 so that the retainer ring outer surface 65 snugly but 18 slidably mates with the head interior spherical shaped 19 surface 48, as is seen in Fig. 7.

With reference to Figs. 9, 10, and 12 the ring 8 in the 21 head 7 is slid over the shank capture structure 21 so that 22 the splines 24 slide upwardly through and above respective 23 channels 60 so that the splines 24 are then located, at 24 least partially, in the U-shaped channel 38 and chamber 47 1 above the retainer ring 8, as is shown in Fig. 10. The 2 shank 6 is then rotated 60 degrees relative to the head 3 about the axis A and the translational direction of the 4 shank 6 is reversed so that it goes downwardly or axially with respect to the head 7, as is seen in Figs. 11 and 13 6 and the splines 24 enter the recesses 62. At this point 7 there is no substantial outward or downward pressure on the 8 retainer ring 8 and so the retainer ring 8 is easily 9 rotatable along with the shank 6 within the chamber 47 and such rotation is of a ball and socket type limited by 11 engagement of the shank neck 20 with the ring restrictive 12 neck 54. Rotation is shown in Fig. 14 where it is 13 illustrated that the shank 6 can be rotated through a 14 substantial angular rotation relative to head 7, both from side to side and from front to rear so as to substantially 16 provide a universal or ball joint wherein the angle of 17 rotation is only restricted by engagement of the neck 20 18 with the neck 54 on the head 7.

19 The assembly 1 is then normally screwed into a bone, such as vertebra 2, by rotation of the shank 6 using a 21 suitable driving tool (not shown) that operably drives and 22 rotates the shank 6 by engagement thereof at the apertures 23 31. The relative position of the shank 6 is shown in Fig. 8 24 with a phantom vertebra 2. Normally, the head 7 and ring 8 1 are assembled on the shank 6 before placing the shank 6 in 2 the vertebra 2, but in certain circumstances, the shank 6 3 can be first implanted with the capture structure 21 4 extending proud to allow assembly and then the shank 6 can be further driven into the vertebra 2.

6 A rod 3 is eventually positioned within the head U-7 shaped channel 38, as is seen in Fig. 15, and the closure 8 top 9 is then inserted into and advanced between the arms 34 9 and 35 so as to bias or push against the rod 3. The break-off head 68 of the closure top 9 is torqued to a preselected 11 torque, for example 90 inch pounds, to urge the rod 3 12 downwardly. The shank dome 29, because it is radiused and 13 sized to extend upwardly into the U-shaped channel 38, is 14 engaged by the rod 3 and pushed downwardly when the closure top 9 pushes downwardly on the rod 3, as is seen in Fig. 16.
16 The downward pressure on the shank 6 in turn urges the 17 splines 24 downwardly which exerts both a downward and 18 outward thrust on the retainer ring 8, as is seen in the 19 configuration shown in Fig. 17. The polyaxial bone screw assembly 1 including rod 3 and shown positioned in a 21 vertebra 2 is illustrated in Fig. 18. The axis A of the 22 bone screw shank 6 is illustrated as not being coaxial with 23 the axis B of the head 7 and the shank 6 is locked in this 24 angular locked configuration. Other angular configurations 1 can be achieved, as required during installation surgery due 2 to positioning of the rod 3 or the like.

3 If removal of the assembly 1 is necessary, the assembly 4 1 can be disassembled by using a driving tool mating with the closure top apertures 81 to rotate the base 67 and 6 reverse the advancement thereof in the head 7 and then 7 disassembly of the remainder of the assembly 1 in reverse 8 mode in comparison to the procedure described above for 9 assembly.

Illustrated in Fig. 19 is a second embodiment of a 11 retainer ring 88 in accordance with the present invention.
12 The retainer ring 88 is quite similar to the retainer ring 8 13 of the previous embodiment except that it is noncontinuous 14 and has a radially extending space or gap 90 from top to bottom along one side thereof. The gap 90 allows for 16 expansion without requiring stretching of the material of 17 construction of the ring 88, as is the case with the 18 previous embodiment. The ring 88 includes a central bore 19 92, spline channels 93 and spline receivers 94 which are all similar to the similar structures described for the previous 21 embodiment. The retainer ring 88 also has a partial 22 hemispherical shaped surface 95 on the outer side thereof.
23 Illustrated in figures 20 and 21 are elements of a 24 third embodiment of the present invention including a shank 1 106 and a capture ring 107 which are used otherwise in the 2 same manner as has been described in the first embodiment 3 and, in particular, with a head such as head 7 which is not 4 further described herein. The shank 106 is similar to the shank 6 in that it has a body 110 with a helically round 6 thread 111 thereon and a capture structure 114 joined to the 7 body 110 by a neck 115. The principle differences between 8 the present embodiment and the first embodiment is that the 9 capture structure 114 includes four splines 120 that are similar in shape to the splines 24 of the first embodiment, 11 but the splines 120 are centered and located at 90 degrees 12 from one another such that there is a pairing of opposed 13 splines 120 and the dome of the prior embodiment is replaced 14 with an axial extension 122. Each of the splines 120 includes a wedge face 121. The extension 122 has a faceted 16 surface 123 that extends parallel to the axis of the shank 17 106 and that is sized and shaped to receive a hex head 18 driving tool (not shown) for driving the shank 106 into 19 bone. The extension 123 also has a radiused upper surface 124. The shank 106 also has an axial extending cannulation 21 or bore 125 that extends entirely through the length of the 22 shank 106.

23 The capture ring 107, shown in Fig. 21, is otherwise 24 similar to the retainer ring 8 except that it includes a set 1 of four channels 126 and four recesses 127 that are sized 2 shaped and positioned so as with respect to the channels 126 3 to allow the splines 120 to slidingly pass upwardly through 4 and with respect to the recesses 127 to capture and receive the splines 120, as they move axially downwardly. The ring 6 107 has a partial hemispherical outer surface 129 that mates 7 with the corresponding surface in the head 7 in the manner 8 described for the first embodiment.

9 It is to be understood that while certain forms of the present invention have been illustrated and described 11 herein, it is not to be limited to the specific forms or 12 arrangement of parts described and shown.

Claims

What is claimed and desired to be secured by Letters Patent is as follows:

1. A polyaxial bone screw comprising:

(a) a shank having a body adapted to be implanted in a bone and a capture structure extending from said body; said capture structure including at least one spline that extends radially outward therefrom;
(b) a head having a channel adapted to receive a rod member and a base having a cavity with a partial spherical surface and communicating with said channel through an upper opening; said cavity communicating with an exterior of said head through a lower opening sized and shaped to receive said shank capture structure therethrough;

(c) a retainer ring that is receivable into said head cavity and having an external partial spherical surface sized and shaped to be seated on said head partial spherical surface; said ring having a central bore with an axial pass through ring channel opening into said bore for each of said at least one spline respectively; said ring bore and said ring channel being sized and shaped to allow said shank capture structure to axially pass therethrough and then be rotated; said retainer ring also having a capture recess for each of said at least one spline sized and shaped to receive and capture a respective spline when said shank is subsequently moved axially downward relative to said retainer ring such that said capture structure is captured by said ring, but said shank is rotatable relative to said head in an unlocked assembly configuration; and (d) a closure top for operably urging said shank downward so as to frictionally engage said ring surface with said head surface so as to lock said shank in position relative to said head in a locked configuration.

2. The screw according to claim 1 wherein:
(a) said shank has at least two splines circumferentially equally spaced.

3. The screw according to claim 1 wherein:
(a) said shank has at least four splines circumferentially equally spaced.

4. The screw according to claim 1 wherein:

(a) said shank capture structure includes an upward extension having a radiused dome sized and shaped so as to be adapted to engage the rod member when received in said head and wherein said closure top is adapted to operably urge the rod member against said dome upon said closure top being operably positioned in said head.

5. The screw according to claim 4 wherein:

(a) said dome has a radius that is substantially less than the radius of said retainer ring external partial surface.

6. The screw according to claim 1 wherein:

(a) said head includes upstanding spaced arms forming the channel adapted to receive the rod member and having first guide and advancement structures on the inside of said arms; and (b) said top operably is positioned between said arms to close said channel and includes second guide and advancement structure mating with the first guide and advancement structures on said arms to allow said closure top to be rotated into said head and to be adapted to bias against the rod member located therein.

7. The screw according to claim 6 in combination with:
(a) a rod received in said U-shaped channel.

8. The screw according to claim 1 wherein:

(a) said head lower opening has a restrictive neck that is smaller in radius than said retainer ring.

9. The screw according to claim 1 wherein:

(a) said ring loads into said head through said upper opening and said shank loads into said head through said lower opening.

10. The screw according to claim 1 wherein:

(a) said ring is a split ring having a radially extending gap therealong.

11. In a polyaxial bone screw having a head and a shank, the improvement comprising:

(a) further including a capture ring sized and shaped to be received within said head and having a central bore with at least one axially aligned channel extending radially outward from said bore;
and (b) said shank having a capture end having a radially outward extending spline associated with each of said at least one axially aligned channel;
said shank capture end being sized and shaped to pass through said bore with each spline, such that each spline is thereafter positioned above said ring; said shank being thereafter axially rotatable so that each spline is non aligned with a respective channel thereby capturing said shank relative to said ring.

12. The bone screw according to claim 11 including at least two channels and at least two splines sized and shaped and positioned to slidingly mate with respective channels when in an aligned configuration.

13. The bone screw according to claim 11 wherein:

(a) said shank includes an upper projection that extends above said ring after said shank and ring are joined; and including (b) a closure mechanism for said head; said closure mechanism biasing against said projection when said bone screw is assembled so as to urge each of said splines against said ring.

14. The screw according to claim 13 wherein:

(a) said projection is a dome having a first radius of curvature that is smaller than a second radius of curvature associated with said ring.

15. The screw according to claim 11 wherein;

(a) said head has an inner chamber that has a partial spherical surface substantially having the same radius as a partial hemispherical surface on said ring; said ring operably seating in said head chamber and on said head surface.

16. The screw according to claim 15 wherein:

(a) said chamber opens onto an exterior of said head through a neck sized and shaped to receive said shank; said shank being operably at least partially received through said neck; and (b) said neck is smaller in diameter than said ring.

17. The screw according to claim 16 wherein:

(a) said head has a rod receiving channel; and including (b) a rod operably positioned in said rod channel and operably engaging said shank;

(c) a closure top for operably closing said rod channel and biasing against said rod.

18. The screw according to claim 11 wherein:

(a) said ring includes a spline receiving recess for each of said splines; each of said recesses being circumferentially spaced from a respective ring spline channel and operably capturing a respective spline therein when such a spline is aligned with a respective recess and inserted from above said ring.

19. In a polyaxial bone screw having a shank with a threaded body portion and a capture component joinable by a connection mechanism; the improvement wherein said capture mechanism comprises:

(a) a radially outward extending spline located on a capture end of said shank body portion;

(b) a passthrough bore located in said capture component and including a radially outward extending channel; and (c) said bore being sized and shaped to slidingly receive and allow passage of said shank capture end with said spline through said bore and channel in an aligned configuration; said shank body portion being thereafter axially rotatable relative to said capture component to position said spline in a non aligned configuration wherein said spline will not pass through said channel.

20. The bone screw according to claim 19 wherein:

(a) said capture component includes a capture recess for said spline that is only accessible when said spline is not aligned with said channel in said non aligned configuration.

21. A polyaxial bone screw having:
(a) a head;

(b) a shank with a threaded body axially adjoining a capture end; said capture end having a circular cross section with at least one non helically wound and radially outward extending spline; and (c) a capture member having a bore with a radially outward positioned channel; said bore and said channel being sized and shaped to slidingly receive said shank capture end and spline when in an aligned configuration; said shank being axially rotatable relative to said capture member after passage of said capture end and spline through said bore and channel to a non aligned configuration wherein said spline is not aligned with said channel and in a non aligned configuration thereby joining said shank to said capture member.

22. The bone screw according to claim 21 wherein:

(a) said capture member includes a capture recess for receiving and capturing said spline in said channel non aligned configuration.

23. The bone screw according to claim 21 wherein:

(a) said head includes a cavity with an integral partial spherical shaped surface; and (b) said capture member includes an outer surface that is sized and shaped to be rotatingly received in said head surface.

24. The bone screw according to claim 23 including:

(a) a rod channel for receiving a rod member; and (b) a locking closure top for operably locking said rod and said capture member in a fixed position relative to said head.

25. The bone screw according to claim 23 wherein:
(a) said cavity has a lower neck that operably receives said shank capture end and said neck has a radius associated therewith that is smaller than a radius of said capture member, so as to prevent passage of said capture member therethrough when said capture member is in said head cavity.

26. A polyaxial bone screw comprising:

a) a head having a channel adapted to receive an elongate rod and having a lower aperture;

b) a shank having a lower portion adapted to be implanted in a bone of a patient and an upper portion; said shank being sized and shaped to be uploaded into said head through said aperture; and c) said shank upper portion being sized and shaped so as to extend into said channel after said shank is received in said head.

27. The bone screw according to Claim 26 including:

a) a capture structure separate from said shank and received in said head; said capture structure mating with said shank upper portion so as to secure said shank to said head while allowing polyaxial movement of said shank relative to said head.

28. The bone screw according to Claim 27 wherein:

a) said shank upper portion includes an engagement end positioned and shaped so as to be adapted to abut against the elongate rod placed in said channel.

29. The bone screw according to Claim 28 wherein:
a) said engagement end is convex.

30. The bone screw according to Claim 26 including:

a) a closure including mating structure for mating with said head and closing said channel so as to be adapted to capture the rod in said channel.

31. The bone screw according to Claim 30 wherein:

a) said closure is threaded and said head includes mating threads to allow said closure to be threaded into and torqued in said head.

32. The bone screw according to Claim 31 including:
a) the rod.

33. The bone screw according to Claim 32 wherein:

a) said shank upper portion is shaped and positioned such that upon assembly of said bone screw and said rod said shank upper portion has an engagement region that directly and frictionally engages said rod so as to secure said shank in a selected fixed angular configuration relative to said head.

34. In a polyaxial bone screw having a shank and a head with an upward opening receiving channel and a lower opening; the improvement comprising:
a) said shank being sized and shaped to be loaded upwardly through said head lower opening; said shank being sized and shaped to extend into said channel after being received in said head.

35. The screw according to Claim 34 wherein:
a) said shank includes an upper portion that extends into said channel when said shank is loaded into said head.

36. The bone screw according to Claim 35 including:

a) a retainer structure separate from said shank and being securable to said shank upper portion;
said retainer structure being receivable into said head.

37. The bone screw according to Claim 36 wherein:
a) said retainer structure is sized and shaped to be downloaded into said head through said channel from a side opposite said shank.

38. The bone screw according to Claim 37 wherein:

a) said retainer structure has a radiused surface adapted to pivotally mate with a radiused mating surface in a chamber in said head.

39. A polyaxial bone screw and rod assembly comprising:
a) a head having a channel adapted to receive a rod and having a lower aperture;

b) a shank having a threaded lower portion adapted to be implanted in a bone and an upper portion with a first capture structure;

c) said shank upper portion being sized and shaped to be uploaded through said head lower aperture;

d) a retaining structure having a second capture structure that mates with and secures to said first capture structure inside said head; said retaining structure being non integral with said shank; said retaining structure being downloaded from a top of said head;
e) the rod adapted to be received in said channel;
and f) said shank upper portion further including an upper convex surface sized, shaped and positioned such that when said bone screw is fully assembled and said rod is located in said channel, said convex surface engages said rod to urge said shank into a non moveable configuration relative to said head.

40. The bone screw according to Claim 39 wherein:

a) said retaining structure is a continuous ring.

41. The bone screw according to Claim 39 wherein:

a) said retaining structure is a discontinuous ring.

42. In a polyaxial bone screw having a shank and a head wherein said head includes a rod receiving channel;
the improvement comprising:

a) said shank being sized and shaped to allow uploading of said shank into said head from below; and b) a retaining structure non integral with said head and said shank for capturing said shank in said head; said shank extending into said channel after assembly of said shank with said head.

43. In a polyaxial bone screw having a shank and a head wherein said head includes a rod receiving channel;
the improvement comprising:

a) said shank being sized and shaped to allow for said shank to be uploaded into said head; and b) said shank having an upper engagement region sized and shaped to project into said channel after said shank is loaded into said head.

44. In a polyaxial bone screw having a shank and a head wherein said head includes a rod receiving channel;
the improvement comprising:
a) said head having a lower aperture and said shank being sized and shaped so as to allow uploading of an upper portion of said shank through said aperture into said head; and b) retaining structure that is non integral with said shank and loaded separately into said head;
said retaining structure mating with and capturing said shank in said head and forming a combined assembly with said shank; and wherein c) a portion of said assembly extends into said channel.

45. The bone screw according to Claim 44 wherein:
a) said retaining structure is sized and shaped to be loaded into said head opposite said shank.

46. In a polyaxial bone screw having a shank and a head;
the improvement comprising:

a) said head having a lower aperture and said shank being sized and shaped so as to allow uploading of an upper portion of said shank through said aperture into said head;

b) retaining structure that is non integral with said shank and loaded separately into said head;
said retaining structure mating with and capturing said shank in said head; and c) said retaining structure being uploaded into said head prior to said shank.

47. In a polyaxial bone screw having a head and a shank wherein said head includes a rod receiving channel;
the improvement comprising:

a) said head has an inner chamber and a lower aperture having a first radius;

b) said shank having an upper portion with a second radius less than said first radius such that said shank upper portion is insertable through said aperture;

c) retaining structure within said chamber and independent of said head that is sized and shaped to mate with and be secured to said shank upper portion; said retaining structure and said shank upper portion being joined in said head to form an assembly; and d) a portion of said assembly extending into said channel.

48. In a polyaxial bone screw having a shank and a head having an inner chamber with a radiused surface and also having a lower aperture wherein said head includes a rod receiving channel; the improvement comprising:

a) said chamber surface having a larger radius than said aperture;

b) said shank having an upper portion that has a smaller radius than said aperture to allow said shank to be uploaded through said aperture;

c) a retaining device that loads separately from said shank into said chamber and captures said shank in said chamber to form an assembly; said retaining device having a lower surface sized and shaped to slidingly mate and rotate with said chamber surface during positioning; and d) a portion of said assembly extending into said channel.

49. Use of an elongate shank having a lower threaded portion and an upper portion with said upper portion having an implant engagement end and a bone screw head having a lower aperture communicating with an implant receiving channel for implanting a bone screw in a patient, wherein said upper portion of said shank is adapted to be loaded into said bone screw head from below and through said aperture and wherein said shank extends into said channel when said shank upper end is in said head.

50. The use according to Claim 49 further comprising use of a separate capture structure for capturing said shank within said head.

51. The use according to Claim 50 wherein said capture -54a-structure is adapted to be secured to said upper portion of said shank prior to implantation of said shank in said bone.

The use according to Claim 50 wherein said capture structure is a continuous ring; and said ring comprises a structure adapted to mate with said shank.

The use according to Claim 50 wherein said capture structure is adapted for placement in said head from above at least partially through said channel.

The use according to Claim 49 further comprising use of a closure for said channel.

The use according to Claim 54 wherein said implant is a rod.

The use according to Claim 55 wherein said closure and said head each comprise mating threads for screwing said closure into said head.

The use according to Claim 55 wherein said shank comprises a pivot structure relative to said head to allow adjustment of the angular position of said shank relative to said head; wherein said shank engagement end is radiused, such that said shank engagement end is adapted to engage said rod in a plurality of selectable angular configurations between said shank and said rod; whereby in use said rod frictionally engages and locks said shank in a selected angular configuration relative to said head when said rod is biased against said shank upper engagement end.

58. The use according to Claim 49 wherein said shank upper portion engagement end is adapted for projection into said channel prior to placement of said implant into said channel.

59. Use of a bone screw head for implanting a bone screw in a patient, said bone screw head having a lower aperture communicating with a rod receiving channel and an elongate shank having a lower threaded portion for implantation in a bone and an upper portion with said upper portion having a rod engagement region extending into said channel when said upper portion is in said head, wherein said shank upper portion is adapted to be loaded into said head from below through said aperture while allowing pivoting of said shank relative to said head; and wherein said head comprises a closure that closes said channel and biases against said rod when received in the channel so as to bias said rod against said rod engagement region and lock said head in said selected angular configuration relative to said shank.

60. Use of a bone screw having a shank and a head that has a channel adapted to receive a rod for implanting the bone screw in a patient, the shank adapted to be uploaded into the head, wherein said shank comprises an upper engagement end extending into the channel when the bone screw is fully assembled, such that the upper engagement end is adapted to abut against a rod placed within said channel.

61. The use according to Claim 60 further comprising use of a capture structure for capturing said shank.

62. The use according to Claim 61 wherein said capture structure is adapted to be downloaded into said head from an opposite side from said shank.