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 connector, comprising:
a body that defines a first opening and a second opening, each of the first and second openings extending between a proximal-facing surface and a distal-facing surface of the body, wherein:
the first opening includes a first central axis,
the second opening is offset from the first opening and configured to receive an auxiliary bone anchor therethrough,
the second opening includes a second central axis that extends therethrough, the second central axis extending at an oblique angle with respect to each of the first central axis and a distal-facing surface of the second opening,
a portion of the distal-facing surface surrounding the first opening is parallel to a portion of the distal-facing surface surrounding the second opening, and
the proximal-facing surface surrounding the first opening is parallel to the proximal-facing surface surrounding the second opening.
2. The connector of claim 1 , wherein the second opening is recessed with respect to the proximal-facing surface of the body.
3. The connector of claim 2 , wherein the second opening further includes a recessed lead-in surface proximal of the second opening, the lead-in surface being positioned between the proximal-facing surface and a proximal-most surface that defines the second opening.
4. The connector of claim 1 , wherein the second central axis extends at an angle of between 0 degrees and 15 degrees with respect to the distal-facing surface.
5. The connector of claim 1 , wherein the second central axis extends at an angle of between 15 degrees and 45 degrees with respect to the distal-facing surface.
6. The connector of claim 1 , wherein the auxiliary bone anchor is made of titanium.
7. The connector of claim 1 , wherein the auxiliary bone anchor is used for implantation in the sacral or lumbar spine.
8. The connector of claim 1 , wherein the auxiliary bone anchor has a length of 6 mm to 100 mm.
9. The connector of claim 1 , wherein the first opening includes a smooth, non-threaded interior surface.
10. The connector of claim 1 , wherein the proximal-facing surface of the body is domed.
11. The connector of claim 1 , wherein the distal-facing surface of the body forms a negative of a receiver-member engaged therewith.
12. The connector of claim 1 , wherein the body includes only two openings.
13. The connector of claim 1 , wherein the second opening is partially threaded.
14. The connector of claim 13 , wherein the auxiliary bone anchor includes a variable-angle locking screw having a threaded proximal head configured to engage threads of the second opening.
15. The connector of claim 14 , wherein the threaded proximal head is partially spherical having a thread with a profile that follows an arc-shaped radius of curvature of the spherical portion of the threaded proximal head.
16. The connector of claim 1 , further comprising a protrusion configure to engage a corresponding recess of an object inserted through one or more of the first and second openings.
17. The connector of claim 1 , wherein a distance between the first and second openings is such that bone anchors that extend through the first and second openings are received in a single vertebral level.
18. The connector of claim 17 , wherein a center of the second opening is spaced radially apart from a center of the first opening by between 5 mm and 10 mm.
19. The connector of claim 1 , wherein at least a portion of a proximal-most extent of the second opening is distal to the first opening.
20. The connector of claim 1 , wherein the auxiliary bone anchor has a length that is between 60% and 80% of a bone anchor configured to be received in the first opening.