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 bone anchor;
a receiver member coupled to a proximal end of the bone anchor and defining a recess configured to receive a rod;
a closure mechanism threadably mated to the receiver member;
a wing having a proximal portion with a distal surface that bears against the receiver member, the proximal portion being disposed proximal to the receiver member, a distal portion that defines a bone anchor opening, the distal portion having a lateral surface that is distal to a rod seat of the receiver member and a proximal surface that is distal to the distal surface of the proximal portion, and a spanning portion that connects the proximal and distal portions, the spanning portion having a lateral surface that extends along a sidewall of the receiver member; and
a nut configured to threadably engage the closure mechanism to secure the proximal portion of the wing to the proximal end of the receiver member.
2. The assembly of claim 1 , wherein the closure mechanism comprises a threaded post and wherein the wing includes an opening through which at least a portion of the threaded post is disposed.
3. The assembly of claim 1 , wherein the wing is rotatable about the closure mechanism.
4. The assembly of claim 1 , wherein a distal-facing surface of the proximal portion of the wing bears against a proximal terminal end of the receiver member.
5. The assembly of claim 1 , wherein the lateral surface of the distal portion of the wing forms a negative of the sidewall of the receiver member and wherein the lateral surface of the spanning portion of the wing forms a negative of the sidewall of the receiver member.
6. The assembly of claim 1 , wherein the lateral surface of the spanning portion of the wing includes a protrusion that engages a corresponding recess formed in the receiver member.
7. The assembly of claim 1 , wherein the spanning portion hugs the sidewall of the receiver member.
8. The assembly of claim 1 , wherein the receiver member is polyaxially movable relative to the bone anchor.
9. The assembly of claim 1 , further comprising an auxiliary bone anchor disposed in the bone anchor opening of the distal portion of the wing.
10. The assembly of claim 9 , wherein the proximal-most extent of the auxiliary bone anchor is distal to a rod when the rod is disposed in the recess of the receiver member.
11. The assembly of claim 9 , wherein the proximal-most extent of the auxiliary bone anchor is distal to the distal-most extent of the receiver member.
12. The assembly of claim 1 , wherein the spanning portion has an adjustable height.
13. The assembly of claim 12 , wherein the spanning portion comprises first and second legs movable toward one another to increase the height of the spanning portion and movable away from one another to decrease the height of the spanning portion.
14. The assembly of claim 1 , wherein the spanning portion is deformable to allow the distal portion of the wing to be angled to match an abutting bone surface.
15. A bone anchor assembly, comprising:
a bone anchor;
a receiver member coupled to a proximal end of the bone anchor and defining a recess configured to receive a rod;
a closure mechanism threadably mated to the receiver member;
a wing having a proximal mating portion disposed proximal to the receiver member, the proximal portion having a distal surface that bears against the receiver member to mate the wing to the receiver member, a distal portion that defines a plurality of bone anchor openings, and a spanning portion that connects the proximal and distal portions, the distal portion having a proximal surface that is distal to the distal surface of the proximal portion; and
a nut configured to threadably engage the closure mechanism to secure the proximal portion of the wing to the proximal end of the receiver member.
16. The assembly of claim 15 , wherein the spanning portion includes a protrusion for engaging a sidewall of the receiver member.
17. The assembly of claim 16 , wherein the protrusion engages a recess formed in the sidewall of the receiver member.
18. The assembly of claim 15 , wherein the spanning portion has ribs on an outer surface thereof.
19. The assembly of claim 15 , wherein a central axis that extends through at least one of the plurality of openings is substantially parallel to a central axis that extends through an opening in the proximal portion.