IMPROVEMENTS RELATING TO BONE ANCHORS

Abstract

The present invention describes a bone anchor having a bone abutment surface adapted for congruent attachment to a bone and methods for the production of said bone anchor. The manufacturing methods generally involve mapping of the form of the bone to which the bone anchor is to be applied, commonly carried out by means of an imaging technique. Manufacturing methods further include any suitable process used to make a three-dimensional object: such process generally include either additive or subtractive manufacturing methods. In particular, said bone anchors are useful for attachment to the spine. The present invention also provides a kit for use in spinal surgery, for correcting spinal deformities and fusing adjacent vertebrae in the spine, using the bone anchors described herein.

Claims

1. A bone anchor having a bone abutment surface adapted for congruent attachment to a bone.

2. The bone anchor of claim 1, wherein the bone anchor is adhered to the bone by means of adhesive interposed between the bone and the bone abutment surface.

3. The bone anchor of claim 2, wherein the adhesive is selected from the group consisting of acrylate or methacrylate adhesives, dentine bonding agents including but not limited to glass-ionomer composites, and bone cements.

4. The bone anchor of claim 1, which has a congruent fit with a part of the spine.

5. The bone anchor of claim 4, wherein the part of the spine is a vertebra.

6. The bone anchor of claim 5, wherein the part of the spine is the pedicle of a vertebra.

7. The bone anchor of claim 6, wherein the bone anchor is attached to the bone by means of a pedicle screw.

8. The bone anchor of claim 1, wherein the bone anchor is provided with one or more attachment parts for coupling the bone anchor to other components.

9. The bone anchor of claim 8, wherein the attachment parts are selected from the group consisting of an eyelet connection, a ball connection, a hole and bushing, and a drilling and/or tapping guide.

10. The bone anchor of claim 1, wherein the bone anchor includes a porous region.

11. The bone anchor of claim 1, wherein all or part of the bone anchor carries a coating including hydroxyapatite and/or cytokines.

12. A method for the production of a bone anchor, which method comprises: manufacturing the bone anchor with a bone abutment surface formed in accordance with a data file embodying the form of the bone to which the bone anchor is to be attached, such that the abutment surface is adapted for congruent attachment to the bone.

13. The method of claim 12, which method comprises the preliminary step of generating the data file embodying the form of the bone to which the bone anchor is to be attached.

14. The method of claim 13, wherein the data file is the output of an imaging procedure.

15. The method of claim 14, wherein the imaging procedure is computer-tomography (CT), magnetic resonance imaging (MRI) or MRI with CT.

16. The method of claim 12, wherein the bone anchor is manufactured using an additive manufacturing process or a subtractive manufacturing process.

17. (canceled)

18. The method of claim 12, wherein the bone anchor is made from titanium or titanium alloy or polyetheretherketone (PEEK).

19. (canceled)

20. A plurality of bone anchors having bone abutment surfaces adapted for congruent attachment to the same area of a patient's bone, the bone anchors being provided with differing attachment parts for coupling of the bone anchor to other components.

21. The plurality of bone anchors of claim 20, wherein the attachment parts are selected from the group consisting of an eyelet connection, a ball connection, a hole and bushing, and a drilling and/or tapping guide.

22. A kit for use in spinal surgery, the kit comprising at least two bone anchors, each having a bone abutment surface adapted to have a congruent fit with a corresponding vertebra of a patient's spine, the bone anchors extending when applied to those vertebrae across both pedicles of the vertebrae, and the bone anchors being provided with attachment parts disposed centrally and adapted for coupling to a rod disposed, in use, substantially centrally of the patient's spine.

23. A surgical method, which method includes the step of affixing to a bone a bone anchor having a bone abutment surface adapted for congruent attachment to the bone, wherein the bone anchor has been manufactured by a process including the steps of a) using an imaging technique to generate a data file embodying the form of the bone to which the bone anchor is to be attached; and b) manufacturing the bone anchor with a bone abutment surface formed in accordance with the data file, such that the abutment surface is adapted for congruent attachment to the bone.

24. The method of claim 23, which is a method for correcting spinal deformities, and includes the steps of affixing bone anchors to at least two vertebrae and then connecting the bone anchors to support the spine.

25. The method of claim 23, which is a method for fusing adjacent vertebrae in the spine and, includes the steps of affixing bone anchors to at least two adjacent vertebrae and then connecting the bone anchors to fuse the vertebrae.

26. The method of claim 23, wherein the bone anchor is adhered to the bone or vertebra by means of adhesive interposed between the bone and the bone abutment surface.

27. The bone anchor of claim 26, wherein the adhesive is selected from the group consisting of acrylate or methacrylate adhesives, dentine bonding agents including but not limited to glass-ionomer composites, and bone cements.

28. The method of claim 23, wherein the bone anchor(s) are provided with one or more attachment parts for coupling the bone anchor to other components.

29. The method of claim 28, wherein the attachment parts are selected from the group consisting of an eyelet connection, a ball connection, a hole and bushing, and a drilling and/or tapping guide.

30. The method of claim 23, wherein the bone anchor(s) include a porous region.

31. The method of claim 23, wherein all or part of the bone anchor(s) carries a coating including hydroxyapatite and/or cytokines.

32. (canceled)

Description

[0085] The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which:

[0086] FIG. 1 shows a first embodiment of a bone anchor according to the invention, with a ball connection;

[0087] FIG. 2 is a side view of the bone anchor of FIG. 1;

[0088] FIG. 3 shows the bone anchor of FIG. 1 applied to the right pedicle of a vertebra, and a second embodiment of a bone anchor according to the invention, with a drill guide and bushing for insertion of a pedicle screw, applied to the left pedicle;

[0089] FIG. 4 is a side view of the second embodiment of the bone anchor;

[0090] FIG. 5 shows a third embodiment of a bone anchor according to the invention, being a bilateral anchor applied to both pedicles of a vertebra;

[0091] FIG. 6 is a side view of the bilateral bone anchor of FIG. 5;

[0092] FIG. 7 is a view similar to FIG. 3, but showing a fourth embodiment of a bone anchor, with an eyelet connection, applied to the right pedicle, and a fifth embodiment of a bone anchor, with a bushing for a pedicle screw, on the left pedicle;

[0093] FIG. 8 is a side view of the fourth embodiment of the bone anchor, with an eyelet connection;

[0094] FIG. 9 is a side view of the fifth embodiment of the bone anchor, with a bushing for a pedicle screw;

[0095] FIG. 10 is a schematic illustration of the manner in which the bone anchor of FIG. 5 may be produced by an additive manufacturing process;

[0096] FIG. 11 is a schematic illustration of the manner in which the bone anchor of FIG. 5 may be produced by a subtractive manufacturing process; and

[0097] FIGS. 12(a) and 12(b) illustrate schematically two different types of spacer formation that may be incorporated into a bone anchor of the invention.

[0098] FIGS. 1 and 2 show a first embodiment of a bone anchor according to the invention, generally designated 1. The bone anchor 1 is intended for application to a patient's spine for use in the correction of a spinal deformity. The same is true of the other embodiments described below.

[0099] The bone anchor 1 comprises a baseplate 2 which is custom-manufactured for congruent attachment to a patient's vertebra. The baseplate 2 has a generally concave undersurface that is shaped to fit against the pedicle of the vertebra with a congruent fit. The baseplate 2 has an approximately uniform thickness.

[0100] An upstand 3 with a ball-shaped end 4 projects from the upper surface of the baseplate 2, and serves for attachment of the bone anchor 1 to other components used in corrective spinal surgery, eg rigid rods or wires or the like. The baseplate 2 is also formed with a porous region 5 of open structure. This allows for ingress of tissue into the bone anchor 1, thereby leading to enhanced fixation of the bone anchor 1. The baseplate 2 also carries an integrally formed label 6, being the code T8R, which indicates that the bone anchor 1 is designed to fit vertebra T8 on the right pedicle, as shown in FIG. 3.

[0101] The bone anchor 1 is made from titanium alloy (Tialloy), typically by an additive manufacturing process.

[0102] To adhere the bone anchor 1 to the vertebra, a suitable medical grade adhesive is applied to the undersurface of the baseplate 2 and the bone anchor 1 is pressed into place. As can be seen in FIG. 3, when the bone anchor 1 is positioned on the pedicle of the vertebra, the upstand 3 extends substantially perpendicular to the patients's spine. At a suitable point during surgery, a rod or the like (not shown) may be attached by the surgeon to the ball-shaped end 4 of the upstand 3 by means of a suitable coupling component, such as a tulip clamp.

[0103] FIG. 3 shows a second embodiment of a bone anchor according to the invention, generally designated 21, attached to the left pedicle of the vertebra that also carries the first embodiment 1 on the right pedicle. This embodiment 21 is also shown in FIG. 4. It should be understood that this arrangement is for illustration only; in most instances, where a bone anchor such as the first embodiment 1 is affixed to one pedicle, a second bone anchor of similar form will be attached to the other pedicle.

[0104] The bone anchor 21 has a baseplate 22 of generally similar form to that of the first embodiment 1, save that in this case there is no porous region. The upper surface of the baseplate 22 is formed with two upstanding formations: a bushing 23 around a circular opening 24 in the baseplate 22, and a post 25. As for the first embodiment 1, the baseplate is formed with a label 26, T8L, which indicates that it is made to fit vertebra T8, on the left pedicle.

[0105] In this second embodiment, the bone anchor 21 is attached to the bone using a pedicle screw, in addition to adhesive. The post 25 is sized and angled to guide a drill, with the drill bit moving through the bushing 23 and opening 24 to form a hole in the pedicle, the orientations of the post 25 and bushing 23 being such that the hole is formed at the optimal position and orientation. The bushing 23 also serves to guide the drill, and potentially the depth of the hole, and then to act as a guide for insertion of the pedicle screw.

[0106] The post 25 is designed to be removed from the baseplate 22 once it has been used to guide the drill and/or insertion of the pedicle screw, and the bushing 23 may also be designed to be removed after use, for example by unscrewing.

[0107] Thus, the bone anchor 21 is attached to the left pedicle of vertebra T8 using adhesive, a hole is drilled, guided by the post 25 and bushing 23, and a pedicle screw (not shown) is then inserted. The post 25 and bushing 23 are then removed.

[0108] FIGS. 5 and 6 show a third embodiment of a bone anchor according to the invention, generally designated 31. This embodiment is termed bilateral, by which is meant that it has a single baseplate 32 that is applied across both the right and left pedicles of a vertebra. The bone anchor 31 has two ball-headed upstands 33,34 that extend from the baseplate 32 in a similar fashion to the upstand 3 of the first embodiment 1.

[0109] Thus, when the bone anchor 31 is applied to a vertebra, the upstands 33,34 extend generally perpendicularly from opposite sides of the patient's spine. Two or more such bone anchors 31 may then be connected by rods coupled to the ball-headed upstands 33,34 by any suitable means, eg tulip clamps.

[0110] Finally, FIG. 7 shows fourth and fifth embodiments of a bone anchor according to the invention, generally designated 41 and 51 respectively. These embodiments are shown separately in FIGS. 8 and 9. Once again, it will be appreciated that the depiction of two different forms of bone anchor attached to the same vertebra is for illustration purposes only, and in practice it will generally be the case that pairs of bone anchors applied to any particular vertebra will be of the same form.

[0111] The fourth embodiment 41 has a baseplate 42 that is generally similar to that of the embodiments described above, having a generally concave undersurface that is shaped to fit against the pedicle of a vertebra with a congruent fit.

[0112] The fourth embodiment 41 differs from those previously described in the nature of the attachment part provided on the upper surface of the baseplate 42. In this embodiment 41, an eyelet 43 is formed integrally with the baseplate 42. As can be seen from FIG. 7, when the bone anchor 41 has been affixed to the vertebra, the eyelet 43 extends substantially perpendicularly from the patient's spine and is aligned essentially parallel to the spine. Bone anchors of this type applied to two or more vertebrae may be connected to rods by wires or the like tied to the eyelets 43.

[0113] The fifth embodiment 51, shown in FIGS. 7 and 9, is similar to that of FIG. 3, in that it has a baseplate 52 that is formed with a bushing 53 around an opening 54. The bushing 53 serves as a guide for insertion of a pedicle screw (not shown). Thus, the bone anchor 51 may be attached to the pedicle using adhesive, and then fastened more securely in place by means of the screw. Alternatively, the bone anchor 51 may be attached only with the screw.

[0114] As described above, the bone anchors such as those just described in detail may be produced by various methods, including both additive and subtractive manufacturing methods.

[0115] FIG. 10 illustrates schematically the manufacture of the bone anchor 31 of FIG. 5 by an additive process. Such a process involves the stepwise formation of the bone anchor 31 in a series of layers (segments) that are fused together. FIG. 10 shows the bone anchor 31 in a semi-complete state, with the next layers to be formed (a and b) shown separately. The layer b incorporates the first part of the ball-headed upstands 33,34, and those upstands and the remainder of the bone anchor 31 will be completed by the formation of further layers of fused material. Thus, the bone anchor 31 is progressively built up, layer by layer.

[0116] FIG. 11 is a schematic illustration of the manufacture of the bone anchor 31 by an alternative, subtractive, manufacturing method. In such a method, the bone anchor 31 is produced by machining, eg multi-axis milling, from a block of solid material 110. Thus, the bone anchor 31 emerges from the block 110, as material is machined away from the block 110.

[0117] Whichever manufacturing method is used, the general process is the same and includes the collection of medical data (ie the data file defining the form of the bone to which the bone anchor is to be applied), segmentation to define the series of layers necessary for creation of the undersurface of the baseplate (ie the bone abutment surface), determination of the optimal positions and orientation of any pedicle screw guides, selection and positioning of attachment features and areas of porosity, and the creation of a final CAD file. That CAD file is then used to control the manufacturing process. As described above, a number of bone anchors may be produced, each having the same bone abutment surface but having alternative attachment parts, so that the surgeon is provided with a range of alternatives from which he can choose prior to, or during, the surgical procedure.

[0118] In the first step, the bones are scanned to provide the necessary two-dimensional medical data that will be used to create a three-dimensional image. This will normally be CT or MRI with CT and will be provided by the radiologist working with the clinician. The next step is segmentation. Once a segmentation mask has been created, it is straightforward to convert it into a three-dimensional model. As this may be created using industry standard methods it does not require decisions by the technician. The design of the undersurface of the baseplate of the bone anchor is defined by the surface of the vertebra to which it will be attached. If a screw or attachment part needs to be positioned in line with the pedicle then computer techniques to visualise the screw and rotate the three-dimensional design may be used at this stage to ensure correct positioning and check whether the screw intersects with the outer bone of the vertebra. The attachments can then be chosen from a library of attachment parts, as can the position of any porosity and the size and arrangement of porous regions in the bone anchors. Once all the aspects of the bone anchor have been chosen, positioned and designed, the virtual model can be created in vectors and output in a standard file format, eg a CAD file, before final validation and sign-off by the clinician. The data file is then sent to the manufacturer who generally produces the bone anchors by additive or subtractive manufacturing.

[0119] In order to ensure optimal spacing any of the bone anchors of FIGS. 1 to 9 from the surface of the bone to which the bone anchor is applied, the bone abutment surface of the bone anchor may be formed with one or more downwardly depending spacer formations that bear against the surface of the bone and position the bone abutment surface at precisely the desired separation from the bone, the void between bone abutment surface and the bone thus being occupied by precisely the desired thickness of adhesive.

[0120] This is illustrated schematically in FIGS. 12(a) and 12(b), both of which are fragmentary cross-sectional views of a bone anchor according to the invention positioned on the surface of a bone.

[0121] Referring first to FIG. 12(a), there is shown the peripheral region of the baseplate 2 of the bone anchor 1 of FIGS. 1 and 2 (though the bone anchor could be any of the other illustrated embodiments, or indeed any other bone anchor according to the invention). The bone anchor 1 is positioned on the surface of a bone designated B.

[0122] As can be seen, the underside of the baseplate 2 (ie the bone abutment surface) has a form that mirrors the contours of the bone B. At its periphery, however, the baseplate 2 is formed with a downwardly depending rim 8 that bears directly on the surface of the bone B. The effect of the rim 8 is to position the bone abutment surface of the bone anchor 1 at a precise separation from the bone. That separation corresponds to the depth of the rim 8 (typically 80 m or 100 m). Because of the correspondence between the contours of the bone and the bone abutment surface, the void between them is of substantially uniform depth. That void is occupied by adhesive (designated A), the layer of adhesive thus also being of uniform thickness.

[0123] FIG. 12(b) is similar, but shows a pillar 9 that depends downwardly from the bone abutment surface. The effect of that pillar 9 is similar to that of the rim 8, positioning the bone abutment surface precisely relative to the bone surface and hence providing for a uniform and optimised thickness of adhesive A. The pillar 9 is depicted with a generally cylindrical form, but may have other forms, such as cuboid or conical.

[0124] Of course, a bone anchor according to the invention may be provided with more than one such spacer formation and indeed more than one type of spacer formation.