CN101495052A - Multi-axial bone screw mating base - Google Patents

Abstract

Embodiments of a bone fixation system including a coupling having a base are generally described herein. Other embodiments may be described and claimed.

Description

Multiaxial Bone Screw Mating Base

technical field

[001] The present invention relates generally to a multiaxial bone screw, and more particularly to a multiaxial bone screw having improved clamping between the screw head and the coupling base of the bone screw.

Background technique

[002] A bone fixation system may be provided to couple a bone stabilizing rod or element to a bone fastener. In some systems, a coupling may be provided between the bone stabilization rod and the bone fastener. The coupling or element may comprise an interface between a portion of the bone fastener and the rod.

Brief description of the drawings

[003] FIGS. 1A and 1B illustrate perspective views of a polyaxial bone screw system before and after assembly of system components, in accordance with one embodiment of the present invention.

[004] FIG. 1C shows a cross-sectional view of the polyaxial bone screw system of FIG. 1B.

[005] FIG. 2A shows a perspective view of a coupling in accordance with one embodiment of the present invention.

[006] FIG. 2B shows a cross-sectional side view of the coupling of FIG. 2A.

[007] FIG. 2C shows a cross-sectional preview view of the coupling of FIG. 2A.

[008] FIG. 3A shows a perspective view of a coupling according to another embodiment of the invention.

[009] FIG. 3B shows a cross-sectional top view of the coupling of FIG. 3A.

[0010] FIG. 4A shows a cross-sectional side view of a multiaxial bone fixation system.

[0011] FIG. 4B shows an enlarged view of the interface between the bone fastener head and the flexible J-shaped base of the coupling of FIG. 4A.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] FIG. 1A shows an exploded view of a multiaxial bone fixation system 10 in accordance with an embodiment of the present invention. The multiaxial bone fixation system 10 includes a bone fastener 12 , a rod-to-bone fastener coupling 22 , a saddle 29 and a mating cap 28 . In an embodiment, the bone fastener 12 has a threaded shaft portion 14 (threads not shown), a head portion 16 , a tip 18 , and a neck portion 20 . Tip 18 may be configured to pierce the patient's bone and is positioned distally on threaded stem portion 14 opposite bone fixation element head portion 16 . In one embodiment the bone fastener 12 may be a pedicle screw.

[0013] Neck portion 20 may be positioned between screw head 16 and threaded shank 14. In an embodiment, the neck portion 20 has a smaller width than the threaded rod 14 to enhance multi-axial movement of the coupling member 22 when coupled with the bone fastener head 16 . Coupling 22 includes an opening 24 in the bottom surface configured to allow passage of bone fixation tip 18 and threaded rod 14 . In an embodiment, the bone fastener head 16 may have a curved underside. The curved underside of the head 16 may engage the base 30 of the coupling 22 (FIG. 1C). The coupling 22 may include a side slot or channel 26 formed by the two arms 25A, 25B for receiving the bone stabilization rod 11 therein (Fig. IB).

[0014] The bone fixation system 10 may also include a mating cap 28 including a snap cap with set threads, an interlock cap, or a locking cap with set screws thereon. In an embodiment the mating cap 28 may lock the rod 11 in the slot 26 of the coupling 22 by transmitting a downward force from the rod 11 , the saddle 29 , the head 16 of the fixture 12 and the base 30 of the coupling 22 . In an embodiment a saddle 29 may be seated in the channel 26 above the head 16 of the bone fastener 12 and assist in holding the system 10 together after installation. Saddle 29 may have a bottom surface configured to rest on the upper surface of head 16 of mount 12 , and an inwardly curved top surface for matingly receiving cylindrical rod 11 .

[0015] In one embodiment, the saddle 29 may serve as an intermediate structure to facilitate even distribution of the load force on the top surface of the head 16 of the bone fastener 12, which is generated by the mating cap 28 being tightened onto the rod 11 of. The coupling head 22 includes a base 30 to provide a clamping and retaining force between the coupling 22 and the head 16 of the bone fastener 12 to limit any post-installation displacement of the bone fastener 12 relative to the coupling 22 .

[0016] FIG. 1B shows a perspective view of the assembled multiaxial bone fixation system of FIG. 1A. In an embodiment, bone fastener 12, after being inserted into coupling 22 through opening 24, may be driven into bone (to be secured), such as by a spinal pedicle of known techniques. Head 16 of bone fastener 12 may include a Hex, Phillips, or other tool engagement opening 32 (FIG. 1C). The fastener 12 can be driven into the bone as far as the shoulder 20 to allow polyaxial articulation between the locking coupling 22 and the head 16 of the bone fastener 12 before engaging the cap 28 . Rod 11 may be inserted into channel 26 after bone fastener 12 is installed in the bone.

[0017] The rod 11 and coupling member 22 can be adjusted to form the desired relationship with the bone fastener 12 until the mating cap 28 is locked relative to the rod 11. 1C is a cross-sectional side view of the bone fixation system 10 shown in FIG. 1B along line A-A. In an embodiment, the underside of the bone fastener head 16 can engage and rest against the base 30 of the coupling 12 . The base 30 may determine the shape of the opening 24 .

[0018] FIG. 2A is a side perspective view of a coupling 22 in accordance with an embodiment of the present invention. 2B is a cross-sectional side view of the coupling 22 of FIG. 2A along line A-A, and FIG. 2C is a cross-sectional top view of the coupling 22 of FIGS. 2A and 2B. The coupling member 22 includes a polygonal shape 31 with a base 30 providing a discrete number of contact surfaces or points 34 for engaging the underside of the head 16 of the bone fastener 12 .

[0019] Coupling member 22 may also include a lip 36 for engaging a flange or raised portion of mating cap 28 to fixedly couple rod 11, coupling member 22, and bone fastener 12 together. As shown in FIG. 2C , the polygonal 31 base 30 may be configured as a polygon including an octagon with eight distinct sides or faces 31 . When the bone fastener head 16 is placed in the multi-faceted base 30 and pressed against the base 30 by the mating cap 28, a discrete friction or clamping force can be generated primarily near the center of each side or face 34 of the polygonal base 30. Point 34 on the junction shown.

[0020] By providing discrete points of contact, the base 30 can provide increased clamping force between the head 16 of the bone fastener 12 and the coupling member 22. In an embodiment, the primary contact between head 16 and base 30 is centered at or near point 34 when head 16 of bone fastener 12 is pressed into base 30 . The polygonal 31 base 30 may provide enhanced clamping between the coupling member 22 and the head 16 of the bone fastener 12 due to discrete contacts 34, reactive loads, and deformation of the head 16 at the base contact surface 30. The base contact surface 30 can deform at each contact point 34 when the mating cap 38 is locked in place by pressure or stress at the point 34 . In an embodiment, the discrete contact points 34 of the base 30 can significantly increase the force on each area between the coupling member 22 and the fixing member 12 .

[0021] FIG. 3A is a perspective view of another coupling 40 in accordance with an embodiment of the present invention. Coupling 40 includes a channel 42 for receiving a rod (not shown) therein and a base 44 having discrete prongs 46 . Each prong 46 may be bent inwardly at the bottom portion of the coupling 40 . FIG. 3B is a cross-sectional top view of coupling 40 . When the head 16 of the bone fastener 12 is placed and pressed against the base 44, it can engage the discrete prongs 46. In an embodiment, the inner surface of the prong 46 forms the base 44 and provides increased friction between the head 16 of the bone fastener 12 and the base 44 in accordance with the principles described above with respect to the coupling 22 .

[0022] The coupling 40 may also provide increased compliance and the ability to dynamically distribute loads across the surface of the base due to the discrete prongs 46. The coupling member 40 can reliably withstand and handle the external force without moving relative to the bone fixation member 12 in the face of the external force. Additionally, the prongs 46 can provide flexibility between the coupling 40 and the head 16 of the bone fastener 12 so that the load can be more evenly distributed across the prongs 46 .

[0023] FIG. 4A is a cross-sectional view of a bone fixation system 50 in accordance with an embodiment of the present invention, and FIG. 4B is an enlarged view of a portion of the system 50. Bone fixation system 50 includes bone fastener 52 having threaded shaft 54 , neck portion 60 , tip 58 and spherical threaded head 56 . In an embodiment, neck portion 60 is narrower than threaded rod 54 to allow for increased multi-axial articulation between coupling 62 and bone fastener 52 . The coupling head 62 may include a U-shaped channel 64 for receiving the bone stabilization rod 11 therein.

System 50 may include a mating cap 68 , such as a snap cap, configured to be received and locked within a correspondingly shaped chamber 66 of coupling 62 . The chamber 66 may include a ledge 70 configured to lock the mating cap 68 within the chamber 66 . As shown in FIG. 4B , the coupling 62 may include a circular J-shaped base 71 with a J-shaped lip 72 . J-shaped base 71 may be configured to flexibly retain head 56 of bone fastener 52 within coupling 62 . The J-shaped base surface lip 72 may provide greater performance to resist and distribute loads between the base surface 71 and the head 56 so that less tip transfer or breakage occurs due to external forces. In an embodiment, the base 72 may be divided into discrete J-shaped lips 72 similar to the prongs 46 shown in FIG. 3A .

[0025] The accompanying drawings, which form a part hereof, show by way of illustration and not limitation specific embodiments in which the subject matter may be practiced. The illustrated embodiments describe in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived thereby, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Therefore, this detailed description is not to be limiting, and the scope of different embodiments is to be defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0026] If more than one embodiment is in fact disclosed, the term "invention" may be used herein to refer to those embodiments of the inventive subject matter, individually or collectively, for convenience only and not to automatically limit the scope of the application for a single invention or inventive concept. Therefore, although specific embodiments have been shown and described herein, any arrangement which achieves the same purpose may be substituted for the specific embodiment shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combining the above embodiments and other embodiments not described in detail here will be obvious to those skilled in the art based on the above description.

[0027] The Abstract of the Disclosure is provided pursuant to 37 C.F.R. §1.72(b), requiring the Abstract to allow the reader to quickly ascertain the substance of the technical disclosure. It should be understood that it will not be used to interpret or limit the scope or meaning of the claims. In the foregoing Detailed Description, various features are grouped together in a single embodiment for simplicity of description. This method of description is not to be construed as requiring more features than are expressly recited in each claim. Rather, inventive subject matter may be found in less than all features of a single disclosed embodiment. Thus hereby incorporated into the following claims of the Detailed Description, each claim standing on its own as a separate embodiment.

Claims (29)

CLAIMS 1. A coupling comprising a base having an opening through which a first portion of a bone fastener passes, and the opening has a discrete number of discrete contact elements each capable of engaging a bone fastener. the second part. 2. The coupling of claim 1, the bone fixation first portion comprising a bone fixation element. 3. The coupling of claim 1, the bone fastener second portion including an at least partially spherical head. 4. The coupling of claim 1, wherein at least one of the limited number of contact elements is deformable. 5. The coupling of claim 1, wherein at least one of the limited number of contact elements is flexible. 6. The coupling of claim 1, wherein each contact element has a contact point configured to engage the second portion of the bone fastener. 7. The coupling of claim 1, wherein at least one of the limited number of contact elements includes a prong. 8. The coupling of claim 1, wherein the coupling couples the bone fastener to the rod. 9. The coupling of claim 8, the coupling further comprising a rod receiving channel. 10. A system comprising: Bone Fixation; stick; and A coupling for coupling a bone fastener to a rod, the coupling including a base having an opening through which a first portion of the bone fastener can pass, and the opening has a discrete number of discrete contact elements each contacting The element is capable of engaging the second portion of the bone fastener. 11. The system of claim 10, the bone fastener first portion comprising bone fixation elements. 12. The system of claim 10, the bone fastener second portion comprising an at least partially spherical head. 13. The system of claim 10, wherein at least one of the limited number of contact elements is deformable. 14. The system of claim 10, wherein at least one of the limited number of contact elements is flexible. 15. The system of claim 10, wherein each contact element has a contact point configured to engage the second portion of the bone fastener. 16. The system of claim 10, wherein at least one of the limited number of contact elements includes a prong. 17. The system of claim 10, the coupling further comprising a rod receiving channel. 18. A coupling comprising a base having an opening through which a first portion of a bone fastener passes, and the opening having a flexible deformable contact element capable of flexibly engaging a bone fastener the second part. 19. The coupling of claim 18, the bone fixation first portion comprising a bone fixation element. 20. The coupling of claim 18, the bone fastener second portion including an at least partially spherical head. 21. The coupling of claim 18, wherein the flexibly deformable contact element includes a plurality of discrete sub-elements, each sub-element configured to flexibly engage the second portion of the bone fastener. 22. The coupling of claim 18, wherein the flexibly deformable contact element includes a flexibly deformable lip configured to flexibly engage the second portion of the bone fastener. 23. The coupling of claim 18, wherein the coupling couples the bone fastener to the rod. 24. The coupling of claim 23, further comprising a rod receiving channel. 25. A system comprising: Bone Fixation; stick; and A coupling for coupling a bone fastener to a rod, the coupling comprising a base having an opening through which a first portion of the bone fastener can pass, and the opening has a flexible deformable contact element, the contact element A second portion of the bone fastener is flexibly engageable. 26. The system of claim 25, the bone fastener first portion comprising bone fixation elements. 27. The system of claim 25, the bone fastener second portion comprising an at least partially spherical head. 28. The system of claim 25, wherein the flexibly deformable contact element includes a plurality of discrete sub-elements each configured to flexibly engage the second portion of the bone fastener. 29. The system of claim 25, wherein the flexibly deformable contact element includes a flexibly deformable lip configured to flexibly engage the second portion of the bone fastener.

Images