WO2017035186A1

WO2017035186A1 - Convertible bone screw assembly

Info

Publication number: WO2017035186A1
Application number: PCT/US2016/048308
Authority: WO
Inventors: Saechin Kim
Original assignee: The General Hospital Corporation
Priority date: 2015-08-25
Filing date: 2016-08-24
Publication date: 2017-03-02

Abstract

The present invention provides a bone screw assembly including a screw having a shank for fixation to a bone and a first threaded surface. The screw further includes a head, and a neck having a diameter less than that of the head. The assembly also includes a receiver for retaining the screw. In one configuration of the bone screw assembly, a longitudinal axis of the screw is fixed in a coaxial position relative to a longitudinal axis of the central bore of the receiver creating a monoaxial screw. In another configuration of the bone screw assembly, the screw is movable between angular positions such that a polyaxial screw is created.

Description

Convertible Bone Screw Assembly

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on, claims priority to, and incorporates herein by reference in its entirety U.S. Provisional Patent Application Serial No. 62/209,495, filed August 25, 2015 and entitled "Convertible Bone Screw Assembly".

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not Applicable.

FIELD OF THE INVENTION

[0003] This invention relates to orthopedic surgery, and more particularly to spinal surgery and associated apparatus.

BACKGROUND OF THE INVENTION

[0004] The human spinal cord is a highly complex system of bones and connective tissues that provide support for the body and protect the delicate spinal column and nerves. The spinal column includes a series of stacked vertebrae, each of which includes a relatively strong outer surface and a relatively weak center. Misalignment of the spinal column is the cause of various disorders including scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal forward curvature of the spine, usually in the thoracic spine), excess lordosis (abnormal backward curvature of the spine, usually in the lumbar spine), and spondylolisthesis (forward displacement of one vertebra over another, usually in the lumbar or cervical spine). Other disorders are caused by abnormalities, disease or trauma, such as ruptured or slipped discs, degenerative disc disease (DDD), fractured vertebra, and the like. Patients that suffer from such conditions usually experience extreme and debilitating pain as well as diminished nerve function.

[0005] Several known techniques, including spinal fixation with pedicle screws, are available to address many such spinal conditions. In one example, the spine is immobilized with orthopedic rods or spine rods, which run alongside the spine. The spine rod is coupled to one or more pedicle screw assemblies that are in turn fastened to the vertebrae or other suitable bone. These pedicle screws generally fall into two categories. Fixed head or monoaxial pedicle screws are used in deform ity/scoliosis fusion surgery so that a surgeon can exert force through the screw to derotate the spine, usually at the apex of the curvature, thereby straightening the spine, after which the spine can be fused. In most spine surgery, where derotation of the spine is not necessary, polyaxial screw assemblies can be used. The polyaxial configuration often includes a receiver (the spine rod holding portion of the screw) that can flex and rotate so that the insertion of the rod into the screw tulips is easier.

[0006] During scoliosis fusion surgery, both types of screws are often used, fixed head pedicle screws for parts of the spine where derotation is desirable, and polyaxial screws for rest of the spine. Doing so requires two sets of implants and sometimes two separate instrument trays, one for fixed head and one for polyaxial head screws, which further complicates these surgical procedures. Moreover, when working with fixed head screws, one or more screws can have trajectories that make fitting a contoured rod into each of the fixed head screws particularly challenging. However, current pedicle screws are not easily convertible from a fixed to a polyaxial

configuration, which would reduce the difficulty of coupling the spine rod to the pedicle screw.

[0007] Therefore, what is needed is a method and apparatus to correct the curvature of the spine that reduces or eliminates the need for multiple types of pedicle screw assemblies and instrument trays. SUMMARY OF THE INVENTION

[0008] The present invention overcomes the aforementioned issues by providing a bone screw assembly that is convertible between a first, monoaxial configuration, and one or more polyaxial configurations.

[0009] According to one aspect of the invention, a bone screw assembly includes a screw, a retainer, and an insert. The screw includes a shank having a body for fixation to a bone and having an outer surface with a first helically wound guide and advancement structure, a head comprising a first recess, and a neck disposed at the base of the head and having a diameter less than that of the head. The receiver is for retaining the screw and has a central bore with an internal surface. The insert is dimensioned to be received within the central bore of the receiver and includes at least one of a projection dimensioned to mate with the first recess of the screw and an opening. A longitudinal axis of the screw is fixed in a substantially coaxial position relative to a longitudinal axis of the central bore of the receiver when the insert is mated with the screw.

[0010] In some forms, the neck may be dimensioned to limit an angular position of the screw.

[0011] In some forms, the receiver may further include a shaped recess for receiving a rod.

[0012] In some forms, the insert may include a surface section and a projection dimensioned to mate with the first recess of the screw in which the projection extends outwardly from the surface section. The surface section of the insert may be dimensioned to contact a portion of the internal surface of the receiver when the projection is mated with the first recess of the screw. The surface section of the insert and the portion of the internal surface of the receiver may be flat.

[0013] In some forms, the insert may include a concave first surface conforming to the head and a second surface for receiving the rod.

[0014] In some forms, the insert may further include a second recess such that, when the projection is mated with the first recess of the screw, the second recess of the insert may be concentrically positioned within the first recess of the screw.

[0015] According to still another aspect of the invention, a bone screw assembly includes a screw assembly and a receiver. The screw includes a shank having a body for fixation to a bone and having an outer surface with a first helically wound guide and advancement structure, a head, a neck disposed at the base of the head and having a diameter less than that of the head, and a shoulder disposed at the base of the neck in which the shoulder has an outer surface with a second helically wound guide and advancement structure. The receiver is for retaining the screw and includes a central bore with an internal surface having a proximal helically wound guide and advancement structure thereon. The second helically wound guide and advancement structure is configured to rotatably mate with the proximal helically wound guide and advancement structure to secure the receiver to the shoulder. A longitudinal axis of the screw is fixed in a coaxial position relative to a longitudinal axis of the central bore of the receiver when the receiver is secured to the shoulder. The screw is movable from a first angular position to a second angular position different from the first angular position when the second helically wound guide and

advancement structure is advanced past the proximal helically wound guide and advancement structure.

[0016] In some forms, an interior dimension of the proximal helically wound guide and advancement structure may be less than an exterior dimension of the head.

[0017] In some forms, the neck may be dimensioned to limit an angular position of the screw.

[0018] In some forms, the receiver may further comprise a shaped recess for receiving a rod. The bone screw assembly may further include an insert dimensioned to be received within the central bore of the receiver in which the insert has a concave lower surface conforming to the head and an upper surface for receiving the rod.

[0019] According to yet another aspect of the invention, a bone screw assembly includes a screw, a receiver, and a retainer. The screw includes a shank having a body for fixation to a bone and having an outer surface with a first helically wound guide and advancement structure, a head comprising a first recess, and a neck disposed at the base of the head and having a diameter less than that of the head. The receiver is for retaining the screw and includes a central bore with an internal surface and a lower end comprising an inwardly directed flange in which the flange includes a recess. The retainer is dimensioned to mate with the recess. A

longitudinal axis of the screw is is fixed in a coaxial position relative to a longitudinal axis of the central bore of the receiver when the retainer is mated with the recess.

[0020] In some forms, the retainer may include a generally ring-shaped structure. The retainer may further include a break in the ring-shaped structure dimensioned to allow the shank to pass through the break.

[0021] According to another aspect of the invention, a method for fixation of a first bone and a second adjacent bone is provided. A first bone screw assembly of the any of the types described above is attached to the first bone and a second bone screw assembly of any of the types described above is attached to the second bone. A rod is secured in the first bone screw assembly and the second bone screw assembly. [0022] In some forms, the first bone may be a first vertebrae and the second bone may be a second vertebrae.

[0023] The foregoing and other advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration non-limiting example embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a perspective view of a set of pedicle screws and rods implanted into a human vertebral column.

[0025] FIG. 2 is a superior view of a typical human vertebra.

[0026] FIG. 3 shows a side view of a bone screw assembly according to a first embodiment.

[0027] FIG. 4 shows a side view in partial cross-section of the bone screw assembly of FIG. 3.

[0028] FIG. 5 shows a side view in partial cross-section of the bone screw assembly of FIG. 3 in a first configuration.

[0029] FIG. 6 shows a side view in partial cross-section of the bone screw assembly of FIG. 3 in a second configuration.

[0030] FIG. 7 shows a plan view of the bone screw assembly of FIG. 3 as taken along line 7-7 of FIG. 6.

[0031] FIG. 8 shows a side view in partial cross-section of the bone screw assembly of FIG. 3.

[0032] FIG. 9 shows an enlarged, partial side view in partial cross-section of the bone screw assembly of FIG. 3 as taken along line 9-9 of FIG. 8.

[0033] FIG. 10 shows a side view in partial cross-section of an alternate

configuration of the bone screw assembly of FIG. 3.

[0034] FIG. 1 1 shows an enlarged, partial side view in partial cross-section of the alternate embodiment of the bone screw assembly of FIG. 3 as taken along line 1 1 -1 1 of FIG. 10. [0035] FIG. 12A shows a side view in partial cross-section of a bone fixation assembly according to a second embodiment.

[0036] FIG. 12B shows a side view in partial cross-section of a bone fixation assembly of FIG. 12A with an insert for fixing the bone screw assembly in a first configuration.

[0037] FIG. 12C shows an enlarged cross-sectional view of the insert of FIG. 12B in isolation.

[0038] FIG. 13 shows a plan view of the bone fixation/screw assembly of FIG. 12A as taken along line 13-13 of FIG. 12A.

[0039] FIG. 14 shows a side view in partial cross-section of the bone fixation/screw assembly of FIG. 12A in a second configuration.

[0040] FIG. 15 shows a side view in partial cross-section of a bone fixation assembly in a first configuration according to a third embodiment.

[0041] FIG. 16 shows a perspective view of the retainer of the bone screw assembly of FIG. 15 in isolation.

[0042] FIG. 17 shows a bottom plan view of the bone fixation/screw assembly of FIG. 15 as taken along line 17-17 of FIG. 15.

[0043] FIG. 18 shows a side view in partial cross-section of a polyaxial

configuration of the bone screw assembly of FIG. 15 in a second configuration.

[0044] FIG. 19 shows a side view in partial cross-section of a bone fixation assembly according to a fourth embodiment.

[0045] FIG. 20 shows a side view in partial cross-section of the bone fixation assembly of FIG. 19 with an insert for fixing the bone screw assembly in a second configuration.

[0046] FIG. 21 shows an enlarged cross-sectional view of the insert of FIG. 20 in isolation.

[0047] Like reference numerals will be used to refer to like parts from Figure to Figure in the following detailed description. DETAILED DESCRIPTION OF THE INVENTION

[0048] Embodiments of the invention may further be understood with reference to the Figures. Figure 1 schematically illustrates one embodiment of a spinal fixation system 10 mounted to a spine 12 of a patient. The spinal fixation system 10 can generally include one or more bone screw assemblies 14 (see, for example, FIG. 3) that can be coupled to a spine rod 16. A portion of the bone screw assembly 14 is inserted into a vertebra 18 in the patient's spine 12 with the spine rod 16 mounted to the pedicle screw assembly 12. However, it will readily be appreciated by those of ordinary skill in the art that the bone screw of this invention can readily be used at other locations along the spine or other bones in a patient's body in addition to those shown in FIG. 1.

[0049] In one embodiment of the present disclosure, the bone screw assembly 14 is coupled to a vertebral pedicle 20. Referring to FIG. 2, a superior view of a typical vertebra with pedicles 20 is schematically illustrated. The vertebral pedicle 20 is a dense stem-like structure that projects from the posterior of a vertebra 18. There are two pedicles 20 per vertebra 18 that connect to other structures (e.g. lamina, vertebral arch).

[0050] As shown in FIG. 3, the pedicle screw assembly 14 according to a first embodiment of this invention includes a bone screw 22 having a threaded shaft 24 and a tip 26 for insertion into the spine 12. A head 28 of the screw 22 is located opposite from the tip 26 and includes a generally spherical or convex profile. The bone screw 22 further includes a neck 30 positioned at the base of the head 28. The neck 30 includes a generally concave or inwardly directed outer surface. Moreover, the neck 30 couples the head 28 to a shoulder 32 of the bone screw 22. The shoulder 32 includes a threaded outer surface that is distinct from the threaded shaft 24. As illustrated in FIG.4, an exterior dimension of the head 28 transverse to a longitudinal axis of the bone screw 22 is greater than the neck 30, shoulder 32 and shaft 24, with the shoulder 32 having the next largest exterior dimension. The bone screw 22 further includes a hexagonal or other shaped socket 34 (FIG. 4) by which an appropriate tool may be used to screw the bone screw 22 into a patient's spine 12 or other bone structure. [0051] An articulating receiver 36 can be selectively mounted to the pedicle screw 22 according to various embodiments of this invention. The receiver 36 defines a generally cylindrical housing with a centrally positioned longitudinal bore and a pair of opposed, upwardly directed and spaced walls 38 forming a generally U-shaped slot 40. The U-shaped slot 40 of the receiver accommodates the spine rod 16 which can be seated therein. The spine rod 16 is captured in the U-shaped slot 40 by a set screw 42 which is threadably engaged between the walls 38 of the receiver 36 as shown in FIG. 3.

[0052] The receiver 36 also includes an inwardly directed flange 44 positioned on a distal end of the receiver 36 opposite from the U-shaped slot 40. The flange 44 includes a threaded interior surface 46 dimensioned to engage and mate with the threaded outer surface of the shoulder 32 of the bone screw 22. The diameter of the passage defined by the flange 44 is seen in FIG. 4 to be less than an outer dimension of the head 28. However, the passage defined by the internal bore within the receiver 36 is able to accommodate the head 28 in order that the head 28 is retained in the receiver 36 when the bone screw 22 is assembled with the receiver 36 as in FIG. 3.

[0053] The bone screw 14 assembly further includes an insert 48 with an exterior surface dimensioned to be telescopically received within the internal bore of the receiver 36. The insert 48 includes a lower end face 50 having generally convex inner surface shaped to provide a bearing surface for the head 28 of the bone screw 22. An opposing upper end face 52 of the insert 48 forms a generally U-shaped channel to accommodate the generally cylindrical spine rod 16.

[0054] The bone screw assembly 14 can be converted between at least two different configurations. In a first, monoaxial configuration as shown in FIG. 5, the angular position of the receiver 36, which can otherwise articulate about the head 28 of the bone screw 22, is fixed by aligning the threaded surface 46 of the flange 44 with the threaded surface of the shoulder 32. By mating the flange 44 with the shoulder 32 in this way, the central axis of the receiver 36 and the bone screw 22 are coaxially aligned along a central axis and the spatial orientation of the receiver 36 is fixed relative to the bone screw. With the bone screw assembly 22 in the first configuration, the insert 48 can be seated within the internal bore of the receiver 36 in contact with the head 28. Thereafter, the spinal rod 16 can be positioned within the U-shaped slot 40 and in contact with the upper face 52 of the insert 48. Finally, the set screw 42 can be threadably engaged between the walls 38 of the receiver 36 as shown in FIG. 3. in order to fixedly couple the spine rod 16 to the bone screw assembly 14.

[0055] From the first configuration, the shoulder 32 can be advanced past the lower end of the receiver 36 such that neck 30 is disposed in the central passage defined inwardly directed flange 44 as shown in FIGS. 6 and 8-1 1. In this second, polyaxial configuration, the receiver 36 is capable of pivotal, rotational and angular movement relative to the bone screw 22 to allow a surgeon the ability to position the bone screw 22 in the patient's spine 12 securely while still accommodating the various geometries and contours of the spine rod 16 as shown in FIGS. 8-1 1 . The benefits of a polyaxial configuration for a bone screw assembly 14 are well known in the art and these benefits are likewise realized by this invention.

[0056] As in the first configuration, with the bone screw assembly 22 in the second configuration, the insert 48 can be seated within the internal bore of the receiver 36 in contact with the head 28. Thereafter, the spinal rod 16 can be positioned within the U-shaped slot 40 and in contact with the upper face 52 of the insert 48. Finally, the set screw 42 can be threadably engaged between the walls 38 of the receiver 36 as shown in FIG. 6. in order to fixedly couple the spine rod 16 to the bone screw assembly 14.

[0057] Different inserts 48 can be used with the bone screw assembly 14 in the second configuration. In one example, a restrictive insert 48 can be used such that a load is transferred from the set screw 42 through the spine rod 16 to the restrictive insert 48 and onto the head 28 of the bone screw 22. In this way, the head 28 is captured between the restrictive insert 48 and the flange 44. The restrictive type insert 48 is suitably implemented in situations where it is desirable to be able to initially maneuver the receiver 36 relative to the bone screw 22 during a procedure. Once the proper orientation of the receiver 36 relative to the bone screw 22 is obtained, the spine rod 16 is positioned in the U-shaped channel 40 in contact with the upper face 52 of the insert 48 thereby locking the position of the receiver body 32 relative to the pedicle screw 20. Advantageously, the receiver 36 and bone screw 22 are fixed or locked relative to one another without deformation of any of the

components of the bone screw assembly 14.

[0058] Alternatively, a non-restrictive insert can be used with the bone screw assembly 14 to fixedly couple the spine rod 16 to the receiver 36 without fixing the orientation of the receiver 36 relative to the bone screw 24. A non-restrictive insert can be positioned in the insert can be seated within the internal bore of the receiver 36. In one example, the insert does not contact the head 28, but instead contact a feature within the receiver, such as an internal flange. In another example, the insert contacts the head 38 but does not directly contact the spine rod 16 in order to prevent the transfer of a load from the spine rod 16 to the head 28 of the bone screw 22. In one aspect as shown in FIG. 6, set screws 54 can be positioned in passages 56 on opposing face of the receiver 36. The set screws 54 can be made to engage the insert 48 and fix the position of the insert within the internal bore of the receiver 36 in order to enable articulation of the bone screw 22 relative to the receiver 36.

[0059] Following placement of the non-restrictive insert, the spinal rod 16 can be positioned within the U-shaped slot 40 and optionally in contact with the upper face of the insert. Finally, the set screw 42 can be threadably engaged between the walls 38 of the receiver 36 as shown in FIG. 6. in order to fixedly couple the spine rod 16 to the receiver 36 such that the orientation of the receiver is still variable relative to the bone screw 22. Referring to FIG. 7, a plan view of the partially assembled bone screw assembly 14 is shown. It can be seen that the receiver 36 and insert 48 are concentrically positioned on a central axis of the receiver 36. Moreover, FIG. 7 shows the location of the U-shaped slot 40 and the upper end face 52 of the insert 48.

[0060] Turning now to FIGS. 8 and 9, the dimensions of the neck 30 can be seen to limit the angle through which the shaft 24 of the bone screw 22 can articulate. In the embodiment illustrated in FIG. 8, the dimension of the neck 30 relative to the internal dimension defined by the flange 44 results in a maximum offset or angle of articulation of 5° for the screw shaft 22 relative to the a longitudinal axis of the receiver 36. In part, the maximum angle of articulate can also be defined by the exterior dimension of the shoulder 32 and the threaded surface thereon. A detailed view of the neck 30 and flange 44 as illustrated in FIG. 9 shows that the at the maximum angle of articulation, the head 28 is in contact with the outer surface of the internal bore of the receiver 36, and the exterior surface of the neck 30 is in contact with the threaded surface of the flange 44. However, the threaded surface of the shoulder 32 is does not necessarily contact the lower end of the receiver 36.

[0061] Referring to FIG. 10, an embodiment of the bone screw assembly 14 with an alternatively dimensioned neck 30' is illustrated. The neck 30' differs from the neck 30 as shown, for example, FIGS. 4-6 and 8. In particular, the neck 30' has an exterior dimension that is less than the exterior dimension of the neck 30 as well as in comparison with an exterior dimension of the head 28. The reduced size of the neck 30' allow for a greater maximum angle of articulation of the bone screw 22. As can be seen in FIG. 10, the maximum angle of articulation is about 15° compared with about 5° as in FIG. 8. Turning to FIG. 1 1 , a detailed view of a portion of the neck 30' shows that the head 28 is in contact with the surface of the internal bore of the receiver 36, and the exterior surface of the neck 30' is in contact with the threaded surface of the flange 44. However, the threaded surface of the shoulder 32 is does not necessarily contact the lower end of the receiver 36. Depending on the dimensions of the neck 30, maximum angles of articulation of about 20°, or about 25°, or about 30°, or about 35°, or about 40°, or about 45° are also possible.

[0062] A second embodiment of a convertible bone screw assembly according to the present disclosure is illustrated in FIGS. 12-14. In general, a bone screw assembly 60 includes a bone screw 62 with a threaded shaft 64, a head 66 and a neck 68. Unlike the bone screw 22 according to the first embodiment (e.g., FIG. 4), the bone screw 62 does not necessarily include a shoulder with a threaded outer surface, as in the case of shoulder 32. The head 66 includes a hexagonal or other shaped socket 70 by which an appropriate tool, such as hex tool 72 can be used to screw the bone screw 62 into a patient's spine or other bone structure.

[0063] An articulating receiver 74 can be selectively mounted to the bone screw 62 according to various embodiments of this bone screw assembly. The receiver 74 defines a generally cylindrical housing with a centrally positioned longitudinal bore and a pair of opposed, upwardly directed and spaced walls 78 forming a generally U- shaped slot 80. The U-shaped slot 80 of the receiver accommodates the spine rod 16 which can be seated therein. The spine rod 16 is captured in the U-shaped slot 80 by a set screw 82 (see FIG. 14) which is threadably engaged between the walls 78 of the receiver 74.

[0064] The receiver 74 also includes an inwardly directed flange 84 positioned on a distal end of the receiver 74 opposite from the U-shaped slot 40. The flange 84 differs from the flange 44 in that it does not necessarily include a threaded interior surface 46. The diameter of the passage defined by the flange 84 is seen in FIG. 12 to be less than an outer dimension of the head 66. However, the passage defined by the internal bore within the receiver 74 is able to accommodate the head 66 in order that the head 66 is retained in the receiver 74 when the bone screw 62 is assembled with the receiver 74.

[0065] The bone screw 60 assembly further includes an insert 86 (see FIG. 12C) with an exterior surface 87 dimensioned to be telescopically received within the internal bore 76 of the receiver 74. The insert 86 includes a lower end face 88 having generally convex inner surface shaped to provide a bearing surface for the head 66 of the bone screw 62. An opposing upper end face 90 of the insert 86 forms a generally U-shaped channel to accommodate the generally cylindrical spine rod 16. Unlike the insert 48, the insert 86 includes a centrally positioned projection 92 extending in an axial direction from the lower end face 88. The projection is dimensioned to mate with the socket 70 as shown in FIG. 12B. The insert 86 can optionally have a passage 94 formed therethrough. The passage 94 has a cross-section dimensioned to receive an appropriate tool, such as hex tool 96. The inclusion of a passage 94 enables a surgeon to still be able to screw the bone screw 62 into a patient's spine or other bone structure even after the insert 86 is positioned within the receiver 74.

[0066] Alternatively, a socket or recess can be substituted for the passage 94 with one difference being that the recess has an opening in the upper end face 90 but does not pass all of the way through the insert 86 to the lower end face 88. Referring to FIG. 13, a plan view of the partially assembled bone screw assembly 60 is shown. It can be seen that the receiver 74, insert 86 and passage 94 are concentrically positioned on a central axis of the receiver 74. Moreover, FIG. 13 shows the location of the U-shaped slot 80 and the upper end face 90 of the insert 86.

[0067] An alternative embodiment of an insert 98 is shown in FIG. 14. The insert 98 includes an exterior surface 100 dimensioned to be telescopically received within the internal bore 76 of the receiver 74. The insert 98 also has a lower end face 102 and upper end face 104 that can be similar is dimension to lower and upper end face 88 and 90. Unlike the insert 86, the insert 98 does not necessarily include a projection 92. Instead, the insert 98 includes an opening 106 in the central axis of the insert 98. The opening 106 has is dimensioned to receive an appropriate tool, such as hex tool 72 or 96. The inclusion of opening 106 enables a surgeon to still be able to screw the bone screw 62 into a patient's spine or other bone structure even after the insert 98 is positioned within the receiver 74.

[0068] As with the bone screw assembly 14, bone screw assembly 60 can be converted between at least two different configurations depending on the choice of insert. In a first, monoaxial configuration as shown in FIG. 12B, the angular position of the receiver 74, which can otherwise articulate about the head 66 of the bone screw 62, is fixed by positioning the insert 86 such that the projection 92 mates with socket 70. In this way, the central axis of the receiver 74 and the bone screw 62 are coaxially aligned along a central axis and the spatial orientation of the receiver 74 is fixed relative to the bone screw 62. At this point, adjustment of the bone screw 62 is possible by way of passage 94. Thereafter, the spinal rod 16 can be positioned within the U-shaped slot 80 and in contact with the upper face 90 of the insert 86. Finally, the set screw 82 can be threadably engaged between the walls 78 of the receiver 74 in order to fixedly couple the spine rod 16 to the bone screw assembly 60.

[0069] Alternatively, the bone screw assembly 60 can have a second, polyaxial configuration by substituting insert 98 for insert 86. In the second configuration, the receiver 74 is capable of pivotal, rotational and angular movement relative to the bone screw 62 to allow a surgeon the ability to position the bone screw 62 in the patient's spine 12 securely while still accommodating the various geometries and contours of the spine rod 16 as shown in FIG. 14. As in the first configuration, a suitable tool can still access the socket 70 in the head 66 by way of opening 106. Thereafter, the spinal rod 16 can be positioned within the U-shaped slot 80 and in contact with the upper face 90 of the insert 86. Finally, the set screw 82 can be threadably engaged between the walls 78 of the receiver 74 in order to fixedly couple the spine rod 16 to the bone screw assembly 60. It is to be understood that insert 98 can be modified as with the previous embodiments described herein to achieve both restricted and non- restricted configurations of the receiver 74 relative to the bone screw 62.

[0070] A third embodiment of a convertible bone screw assembly according to the present disclosure is illustrated in FIGS. 15-18. A bone screw assembly 1 10 can generally be described with reference to bone screw assembly 74, and therefore, like reference numerals with the addition of a prime symbol (') will be used to refer to like parts in the Figures. For example receiver 74' in FIGS. 15 and 18 corresponds to receiver 74 in FIG. 12A. One aspect of bone screw assembly 1 10 is that receiver 74' includes a recess 1 12 dimensioned to receive an elastic retainer 1 14. The retainer 1 14 can be a partial ring-shaped structure with an opening or break 1 16 in the structure. The retainer 1 14 can be positioned in the recess 1 12 about the shaft 64' of the bone screw 62'

[0071] The bone screw assembly 1 10, like bone screw assembly 60, can be converted between at least two different configurations with retainer 1 14. In a first, monoaxial configuration as shown in FIG. 15, the angular position of the receiver 74', which can otherwise articulate about the head 66' of the bone screw 62', is fixed by positioning the retainer 1 14 in the recess 1 12. If the bone screw 62' is already fixed in the spine 12 or other bone, the shaft 64' can pass through the break 1 16 in order to position the retainer 1 14 in the recess 1 12. In one aspect, the retainer 1 14 prevents articulation of the bone screw 62' relative to the receiver 74' by engaging at least a portion of the bone screw 62' such as the shaft 64' or the neck 68'. In the case of bone screw assembly 1 10, a particular insert, such as insert 86 is not required to fix the bone screw assembly 1 10 in the first configuration. Instead, an insert 48 as described herein can be used. Thereafter, the spinal rod 16 and set screw 82' can be positioned as described previously for bone screw assembly 60.

[0072] Alternatively, the bone screw assembly 60 can have a second, polyaxial configuration by removing or omitting retainer 1 14. In the second configuration, the receiver 74' is capable of pivotal, rotational and angular movement relative to the bone screw 62' as shown in FIG. 18. As in other embodiments, it is to be understood that insert 48 can be modified to achieve both restricted and non-restricted

configurations of the receiver 74' relative to the bone screw 62'.

[0073] A fourth embodiment of a convertible bone screw assembly according to the present disclosure is illustrated in FIGS. 19-21 . The bone screw assembly 260 includes a bone screw 262 with a threaded shaft 264, a head 266 and a neck 268. The head 266 includes a hexagonal or other shaped socket 270 by which an appropriate tool, such as hex tool 272, can be used to screw the bone screw 262 into a patient's spine or other bone structure.

[0074] An articulating receiver 274 can be selectively mounted to the bone screw 262 according to various embodiments of this bone screw assembly. The receiver 274 defines a generally cylindrical housing with a centrally positioned longitudinal bore and a pair of opposed, upwardly directed and spaced walls 278 forming a slot 280. The slot 280 of the receiver accommodates a spine rod 16 which can be seated therein in the same manner as shown in the embodiment of FIG. 14. The spine rod 16 is captured in the 280 by a set screw (similar to set screw 82 in FIG. 14) which is threadably engaged in the hole 279 in the walls 278 of the receiver 274 . The bottom of the slot 280 is partially defined by a flat ledge 281 of the receiver 274, which also includes an inwardly directed flange 284 positioned on a distal end of the receiver 274 opposite from the ledge 281 .

[0075] The bone screw assembly 260 further includes an insert 286 (see FIG. 21 ) dimensioned to be received within the slot 280 of the receiver 274. The insert 286 includes a disc shaped section 287 with a lower end face 288 dimensioned to contact the flat ledge 281 of the receiver 274 and the head 266 of the bone screw 262. The insert 286 includes a centrally positioned projection 292 extending in an axial direction from the center of the lower end face 288. The projection 292 is dimensioned to mate with the socket 270 as shown in FIG. 20 and therefore, the projection 292 can have different shapes depending on the shape of the socket 270 of the bone screw 262. The insert 286 can optionally have an opening 294 formed partially or fully through the insert 286. The passage 294 has a cross-section dimensioned to receive an appropriate tool, such as hex tool 296. The inclusion of a passage 294 enables a surgeon to still be able to screw the bone screw 262 into a patient's spine or other bone structure even after the insert 286 is positioned within the receiver 274.

Optionally, the projection 292 can have external threads that mate with internal threads of the socket 270 of the bone screw 262.

[0076] Referring to FIG. 20, a view of the partially assembled bone screw assembly 260 is shown. It can be seen that the receiver 274, insert 286 and passage 294 are concentrically positioned on a central axis of the receiver 274. Moreover, FIG. 20 shows the location of the slot 280 and the disc shaped section 287 of the insert 286.

[0077] As with the bone screw assemblies 14 and 60 described above, the bone screw assembly 260 can be converted between at least two different configurations depending on the use of the insert. The bone screw assembly 260 can have a first, polyaxial configuration shown in FIG. 19. In this first, polyaxial configuration, the receiver 274 is capable of pivotal, rotational and angular movement relative to the bone screw 262 to allow a surgeon the ability to position the bone screw 262 in the patient's spine 12 securely while still accommodating the various geometries and contours of the spine rod 16. A suitable tool 272 can access the socket 270 in the head 266. Thereafter, the spinal rod 16 can be positioned within the slot 280. Finally, set screws can be threadably engaged in the holes 279 in the walls 278 of the receiver 274 in order to fixedly couple the spine rod 16 to the bone screw assembly 260.

[0078] In a second, monoaxial configuration as shown in FIG. 20, the angular position of the receiver 274, which can otherwise articulate about the head 266 of the bone screw 262, is fixed by positioning the insert 286 (e.g., by a press fit or threading) such that the projection 292 mates with socket 270 of the bone screw 262. In this way, the central axis of the receiver 274 and the bone screw 262 are coaxially aligned along a central axis and the spatial orientation of the receiver 274 is fixed relative to the bone screw 262. At this point, adjustment of the bone screw 262 is possible by way of passage 294. Thereafter, the spinal rod 16 can be positioned within the slot 280 and in contact with an upper face 290 of the insert 286. Finally, a set screw can be threadably engaged in the hole 279 in the walls 278 of the receiver 274 in order to fixedly couple the insert 286 and bone screw 262 in the bone screw assembly 260. Thus, the polyaxial screw configuration of FIG. 19 can be converted into a monoaxial screw configuration of FIG. 20 using insert 286 thereby cutting back an inventory that previously had to be maintained with both polyaxial screws and monoaxial screws. Users can purchase all polyaxial screws and then decide to convert the desired screws into monoaxial screws by inserting the insert.

[0079] As used herein, the term "patient" refers to a human or non-human mammalian patient suffering from a condition in need of treatment. The present invention is generally applied to humans. In certain embodiments, non-human mammals, such as rats, may also be used for the purpose of demonstration. One may use the present invention for veterinary purpose. For example, one may wish to treat commercially important farm animals, such as cows, horses, pigs, rabbits, goats, and sheep. One may also wish to treat companion animals, such as cats and dogs.

[0080] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; inventive

embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0081] Unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

Claims

CLAIMS What is claimed is:

1 . A bone screw assembly comprising:

a screw comprising:

a shank having a body for fixation to a bone and having an outer surface with a first helically wound guide and advancement structure; a head comprising a first recess;

a neck disposed at the base of the head and having a diameter less than that of the head;

a receiver for retaining the screw, the receiver comprising a central bore with an internal surface; and

an insert dimensioned to be received within the central bore of the receiver, the insert comprising at least one of a projection dimensioned to mate with the first recess of the screw, and an opening,

wherein a longitudinal axis of the screw is fixed in a substantially coaxial position relative to a longitudinal axis of the central bore of the receiver when the insert is mated with the screw.

2. The bone screw assembly of claim 1 , wherein the neck is dimensioned to limit an angular position of the screw.

3. The bone screw assembly of claim 1 , wherein the receiver further comprises a shaped recess for receiving a rod.

4. The bone screw assembly of claim 1 , wherein the insert includes a surface section, and a projection dimensioned to mate with the first recess of the screw, the projection extending outwardly from the surface section.

5. The bone screw assembly of claim 4, wherein the surface section of the insert is dimensioned to contact a portion of the internal surface of the receiver when the projection is mated with the first recess of the screw.

6. The bone screw assembly of claim 4, wherein the surface section of the insert and the portion of the internal surface of the receiver are flat.

7. The bone screw assembly of claim 1 , wherein the insert includes a concave first surface conforming to the head, and a second surface for receiving the rod.

8. The bone screw assembly of claim 1 , wherein the insert further comprises a second recess, wherein when the projection is mated with the first recess of the screw, the second recess of the insert is concentrically positioned within the first recess of the screw.

9. A method for fixation of a first bone and a second adjacent bone, the method comprising:

attaching a first bone screw assembly according to claim 1 to the first bone; attaching a second bone screw assembly according to claim 1 to the second bone; and

securing a rod in the first bone screw assembly and the second bone screw assembly.

10. The method of claim 9 wherein the first bone is a first vertebrae and the second bone is a second vertebrae.

1 1 . A bone screw assembly comprising:

a screw comprising:

a shank having a body for fixation to a bone and having an outer surface with a first helically wound guide and advancement structure; a head;

a shoulder disposed at the base of the neck, the shoulder having an outer surface with a second helically wound guide and advancement structure; and

a receiver for retaining the screw, the receiver comprising a central bore with an internal surface having a proximal helically wound guide and advancement structure thereon,

wherein the second helically wound guide and advancement structure is configured to rotatably mate with the proximal helically wound guide and advancement structure to secure the receiver to the shoulder,

wherein a longitudinal axis of the screw is fixed in a coaxial position relative to a longitudinal axis of the central bore of the receiver when the receiver is secured to the shoulder, and

wherein the screw is movable from a first angular position to a second angular position different from the first angular position when the second helically wound guide and advancement structure is advanced past the proximal helically wound guide and advancement structure.

12. The bone screw assembly of claim 1 1 , wherein an interior dimension of the proximal helically wound guide and advancement structure is less than an exterior dimension of the head.

13. The bone screw assembly of claim 1 1 , wherein the neck is dimensioned to limit an angular position of the screw.

14. The bone screw assembly of claim 1 1 , wherein the receiver further comprises a shaped recess for receiving a rod.

15. The bone screw assembly of claim 14, further comprising an insert dimensioned to be received within the central bore of the receiver, the insert comprising a concave lower surface conforming to the head and an upper surface for receiving the rod.

16. A method for fixation of a first bone and a second adjacent bone, the method comprising:

attaching a first bone screw assembly according to claim 1 1 to the first bone; attaching a second bone screw assembly according to claim 1 1 to the second bone; and

17. The method of claim 16 wherein the first bone is a first vertebrae and the second bone is a second vertebrae.

18. A bone screw assembly comprising:

a screw comprising:

a receiver for retaining the screw, the receiver comprising:

a central bore with an internal surface;

a lower end comprising an inwardly directed flange, the flange comprising a recess; and

a retainer dimensioned to mate with the recess,

wherein a longitudinal axis of the screw is fixed in a coaxial position relative to a longitudinal axis of the central bore of the receiver when the retainer is mated with the recess.

19. The bone screw assembly of claim 18, wherein the retainer comprises a generally ring-shaped structure.

20. The bone screw assembly of claim 19, wherein the retainer further comprises a break in the ring-shaped structure dimensioned to allow the shank to pass through the break.

21 . A method for fixation of a first bone and a second adjacent bone, the method comprising:

attaching a first bone screw assembly according to claim 18 to the first bone; attaching a second bone screw assembly according to claim 18 to the second bone; and

22. The method of claim 21 wherein the first bone is a first vertebrae and the second bone is a second vertebrae.