Multipoint fixation implants and related methods
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. The distal portion of the wing can define a bone anchor opening through which one or more auxiliary bone anchors can be disposed to augment the fixation of the assembly's primary bone anchor. A distal surface of the distal portion of the wing can be obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction. A distal surface of the distal portion of the wing can be obliquely angled relative to the proximal-distal axis of the spanning portion to face one of a medial direction or a lateral direction. Surgical methods using the bone anchor assemblies described herein are also disclosed.
1. A bone anchor assembly, comprising:
a bone anchor;
an auxiliary bone anchor;
a receiver member coupled to a proximal end of the bone anchor and defining a rod seat configured to receive a rod;
a closure mechanism threadably mated to the receiver member;
a wing that includes a proximal portion, a distal portion, and a spanning portion that connects the proximal and distal portions, the proximal portion having a distal-facing surface that opposes a proximal terminal end of the receiver member and defines an opening through which at least a portion of the closure mechanism is disposed, the spanning portion extending vertically along a side wall of the receiver member between the proximal portion and the distal portion, the distal portion extending outward from a distal end of the spanning portion; and
a nut configured to threadably engage the closure mechanism to secure the proximal portion of the wing to the receiver member,
wherein the distal portion of the wing defines a bone anchor opening through which the auxiliary bone anchor is disposed and wherein a distal surface of the distal portion of the wing is obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction,
wherein the opening of the proximal portion has a maximum diameter that is less than or equal to a maximum diameter of the rod seat of the receiver member.
2. The bone anchor assembly of claim 1 , wherein the distal surface of the distal portion of the wing is obliquely angled relative to the proximal-distal axis of the spanning portion such that the distal surface faces in the cephalad direction.
3. The bone anchor assembly of claim 1 , wherein the distal surface of the distal portion of the wing is obliquely angled relative to the proximal-distal axis of the spanning portion such that the distal surfaces faces in the caudal direction.
4. The bone anchor assembly of claim 1 , wherein the distal surface of the distal portion of the wing is obliquely angled relative to the proximal-distal axis of the spanning portion such that a central axis of the bone anchor opening extends in one of a caudal direction or a cephalad direction and in one of a medial direction or a lateral direction when the wing is secured to the receiver member.
5. The bone anchor assembly of claim 4 , wherein the distal surface of the distal portion of the wing is obliquely angled inward and obliquely angled relative to the proximal-distal axis of the spanning portion such that the central axis of the bone anchor opening extends in the cephalad direction and in the medial direction when the wing is secured to the receiver member.
6. The bone anchor assembly of claim 4 , wherein the distal surface of the distal portion of the wing is obliquely angled outward and obliquely angled relative to the proximal-distal axis of the spanning portion such that the central axis of the bone anchor opening extends in the cephalad direction and in the lateral direction when the wing is secured to the receiver member.
7. The bone anchor assembly of claim 4 , wherein the distal surface of the distal portion of the wing is obliquely angled inward and obliquely angled relative to proximal-distal axis of the spanning portion such that the central axis of the bone anchor opening extends in the caudal direction and in the medial direction when the wing is secured to the receiver member.
8. The bone anchor assembly of claim 4 , wherein the distal surface of the distal portion of the wing is obliquely angled outward and obliquely angled relative to the spanning portion such that the central axis of the bone anchor opening extends in the caudal direction and in the lateral direction when the wing is secured to the receiver member.
9. The bone anchor assembly of claim 1 , wherein a proximal surface of the distal portion of the wing is substantially parallel to the distal surface of the distal portion.
10. The bone anchor assembly of claim 1 , wherein the auxiliary bone anchor has a threaded proximal head and the bone anchor opening has a partially threaded interior surface configured to engage the threaded proximal head of the auxiliary bone anchor such that the auxiliary bone anchor is capable of being locked at any angle amongst a plurality of selectable angles relative to the central axis of the bone anchor opening.
11. The bone anchor assembly of claim 1 , wherein the closure mechanism comprises a threaded post having a radially extending shoulder portion and wherein a counter bore is formed about the opening in the distal-facing surface of the proximal portion of the wing to accommodate the radially extending shoulder portion extending at least partially above the proximal terminal end of the receiver member.
12. The bone anchor assembly of claim 1 , wherein the bone anchor opening defined in the distal portion of the wing comprises a plurality of bone anchor openings.
13. The bone anchor assembly of claim 1 , wherein a central axis of the bone anchor opening is substantially perpendicular to the distal surface of the distal portion such that the central axis of the bone anchor opening extends in the caudal direction or the cephalad direction.
14. The bone anchor assembly of claim 1 , wherein the wing includes a unilateral locking interface, wherein the unilateral locking interface is configured to enable a surgical instrument to hold onto one side of the wing.
15. A bone anchor assembly, comprising:
a bone anchor;
an auxiliary bone anchor;
a receiver member coupled to a proximal end of the bone anchor and defining a rod seat configured to receive a rod;
a closure mechanism threadably mated to the receiver member;
a wing that includes a proximal portion, a distal portion, and a spanning portion that connects the proximal and distal portions, the proximal portion having a distal-facing surface that opposes a proximal terminal end of the receiver member and defines an opening through which at least a portion of the closure mechanism is disposed, the spanning portion extending vertically along a side wall of the receiver member between the proximal portion and the distal portion, the distal portion extending outward from a distal end of the spanning portion; and
a nut configured to threadably engage the closure mechanism to secure the proximal portion of the wing to the receiver member,
wherein the distal portion of the wing defines a bone anchor opening through which the auxiliary bone anchor is disposed and wherein a distal surface of the distal portion of the wing is obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction,
wherein the proximal-distal axis of the spanning portion extends substantially parallel to a longitudinal axis of the opening of the proximal wing portion,
wherein a proximal surface of the distal portion is distal to a majority of the spanning portion along the proximal-distal axis.
16. A bone anchor assembly, comprising:
a bone anchor;
an auxiliary bone anchor;
a receiver member coupled to a proximal end of the bone anchor and defining a rod seat configured to receive a rod;
a closure mechanism threadably mated to the receiver member;
a wing that includes a proximal portion, a distal portion, and a spanning portion that connects the proximal and distal portions, the proximal portion having a distal-most facing surface that opposes a proximal terminal end of the receiver member and defines an opening through which at least a portion of the closure mechanism is disposed, the spanning portion extending vertically along a side wall of the receiver member between the proximal portion and the distal portion, the distal portion extending outward from a distal end of the spanning portion; and
a nut configured to threadably engage the closure mechanism to secure the proximal portion of the wing to the receiver member,
wherein the distal portion of the wing defines a bone anchor opening through which the auxiliary bone anchor is disposed and wherein a distal surface of the distal portion of the wing is obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction.