Multipoint fixation implants
Bone anchor assemblies are disclosed herein that can provide for improved fixation as compared with traditional bone anchor assemblies. An exemplary assembly can include a bracket or wing that extends down from the receiver member and accommodates one or more auxiliary bone anchors that augment the fixation of the assembly's primary bone anchor. Another exemplary assembly can include a plate that is seated between the receiver member and the rod and accommodates one or more auxiliary bone anchors that augment the fixation of the assembly's primary bone anchor. Another exemplary assembly can include a hook that extends out from the receiver member to hook onto an anatomical structure or another implant to augment the fixation of the assembly's primary bone anchor. Surgical methods using the bone anchor assemblies described herein are also disclosed.
1. A bone anchor assembly, comprising:
a body defined by a proximal end, a distal end having a distal-facing surface, and a sidewall that extends between the proximal and the distal ends, the body having a plurality of openings that are formed in the proximal end of the body; and
wherein a first opening of the plurality of openings extends distally towards a first inner proximal-facing surface recessed within the first opening, the first proximal-facing surface defining a first reduced-diameter opening that extends to the distal end to terminate at the distal-facing surface, the first opening being parallel to the proximal end, and the first reduced-diameter opening having a smaller diameter than the first opening and being parallel to the proximal end; and
wherein a second opening of the plurality of openings extends distally towards a second inner proximal-facing surface recessed within the second opening, the second proximal-facing surface defining a second reduced-diameter opening that extends to the distal end to terminate at the distal-facing surface, at least a portion of the second opening being parallel to the proximal end, and the second reduced-diameter opening having a smaller diameter than the second opening and having at least a portion thereof being obliquely angled with respect to the proximal end,
one or more bone anchors configured to be disposed within the plurality of openings, at least one of the bone anchors being an auxiliary bone anchor configured to be received in the second opening.
2. The assembly of claim 1 , wherein a portion of the sidewall that defines the first opening is greater than a portion of the sidewall that defines the second opening in a plane drawn to intersect the body in a direction parallel to a central axis of at least the first opening.
3. The assembly of claim 1 , wherein at least a portion of the proximal end defines at least a portion of the second opening and at least a portion of the second reduced-diameter opening.
4. The assembly of claim 1 , wherein the second opening and the second reduced-diameter opening overlap at least at a first location along the body.
5. The assembly of claim 4 , further comprising a recessed lead-in surface that extends from the first location at the proximal end to the second proximal-facing surface along the second proximal-facing surface.
6. The assembly of claim 1 , wherein a central axis of the second opening is obliquely angled with respect to the distal-facing surface of the body.
7. The assembly of claim 1 , wherein a central axis of the second opening extends at an angle of 0 degrees to 15 degrees with respect to the distal-facing surface.
8. The assembly of claim 1 , wherein a central axis of the second opening extends at an angle of 15 degrees to 45 degrees with respect to the distal-facing surface.
9. The assembly of claim 1 , wherein a central axis of the second reduced-diameter opening is obliquely angled with respect to a central axis of the second opening.
10. The assembly of claim 1 , wherein an inner surface of an inner sidewall that circumscribes the first opening tapers from the first opening to the first reduced-diameter opening.
11. The assembly of claim 1 , wherein the auxiliary bone anchor has a length of 6 mm to 20 mm.
12. The assembly of claim 1 , wherein the auxiliary bone anchor received in the second opening has a shank diameter that is between 50% and 70% of a shank diameter of a bone anchor received in the first opening.
13. The assembly of claim 1 , wherein the auxiliary bone anchor received in the second opening has a length that is between 60% and 80% of the length of a bone anchor received in the first opening.
14. The assembly of claim 1 , wherein at least the second reduced-diameter opening includes a threaded inner surface.
15. The assembly of claim 14 , wherein a proximal head of the auxiliary bone anchor is spherical.
16. The assembly of claim 15 , wherein the threaded inner surface has a profile that follows an arc-shaped radius of curvature of the spherical proximal head.
17. The assembly of claim 1 , wherein a first central longitudinal axis of a bone anchor of the one or more bone anchors disposed in the first opening diverges from a second central longitudinal axis of the auxiliary bone anchor disposed in the second opening.
18. The assembly of claim 1 , wherein a first central longitudinal axis of a bone anchor of the one or more bone anchors disposed in the first opening converges from a second central longitudinal axis of the auxiliary bone anchor disposed in the second opening.
19. The assembly of claim 1 , wherein the body is configured to be contoured to a bone surface before implantation.
20. The assembly of claim 1 , wherein the body is configured to be contoured to a bone surface in situ.
21. The assembly of claim 20 , wherein the body is configured to be flexed in one or more of a medial-lateral direction or a superior-inferior direction to move the plurality of openings into contact with the bone surface.