Bone fixation assembly
A bone fixation assembly and associated method. The bone fixation assembly includes a bone fastener having a head and a bone-engaging portion, a receiver defining an opening along a first axis for receiving the bone fastener at a variable angle, and at least one supporting augment coupled to the bone fastener. The receiver has an inner articulation surface at a lower portion of the opening and matingly articulates with the supporting augment.
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Various internal fixation devices are known for correcting and/or stabilizing malformation or other condition of bones, including long bones and the spine. Such fixation devices can include elongated rods affixed with bone screws at desired orientations relative to the bone or spine. Some known bone fixation devices utilize poly-axial or multi-axial screws for adjusting the fixation device at a desired orientation.
Although the existing fixation devices can be satisfactory for their intended purposes, there is still a need for modular bone screw assemblies that can provide variable angle orientation, and which are easy to assemble.
SUMMARYThe present teachings provide a bone fixation assembly. The bone fixation assembly includes a bone fastener having a head and a bone-engaging portion, a receiver defining an opening along a first axis for receiving the bone fastener at a variable angle, and at least one supporting augment coupled to the bone fastener. The receiver has an inner articulation surface at a lower portion of the opening and matingly articulates with the supporting augment.
The present teachings also provide a method for bone fixation. The method includes providing a receiver defining an opening along a first axis for receiving a bone fastener at a variable angle, inserting the head of the bone fastener into the opening, and inserting at least one supporting augment into the opening. The at least one supporting augment is articulable with an inner articulation surface of the receiver. The method further includes coupling the at least one supporting augment to the head of the bone fastener, and varying the angle of the bone fastener relative to the first axis by articulating the at least one supporting augment relative to the articulation surface.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
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The supporting augments 110 can be positioned relative to each other such that upon assembly each of the first and second end surfaces 140a, 140b of one supporting augment 110 can mate with the second and first end surfaces 140b, 140a, respectively, of the other supporting augment 110, thereby completing an annular curved surface with a 360-degree circumference. The shape of the supporting augments 110 can be defined for ease of assembly and angulation during assembly. For example, during assembly, the supporting augments 110 can be positioned such that the sharp corner 145b of each supporting augment 110 rides on the notch 136 of the other supporting augment 110, such that the supporting augments 110 overlap partially, and the overall size/volume of the resulting configuration is smaller during assembly than the size of the assembled supporting augments 110.
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The bone fixation assembly 100 can be assembled during or before the surgical procedure. Generally, the head 108 of the bone fastener 104 can be inserted first into the opening 118. At least one supporting augment 110 can be inserted into the opening 118, and coupled to the head 108 of the bone fastener 104. The angle α of the bone fastener 104 relative to the first axis X can then be varied by articulating the supporting augment 110 relative to the articulation surface 120.
In one exemplary aspect, the fastener ring 112 can be assembled on the exterior groove 1 11 of the head 108 of the bone fastener 104. The head 108 with the fastener ring 1 12 thereon can be inserted into the receiver 102 through the lower end 122 of the opening 118, and can be pushed above its final seating position to facilitate assembly, as necessary. The supporting augments 110 can then be inserted from an upper end 123 of the receiver 102 and can be pushed toward the fastener ring 112 while the bone fastener 104 is pulled down, until the supporting augments 110 engage the fastener ring 112 and the bone fastener 104 is seated in engagement with the receiver 102. In this position, the bone fastener 104 can freely angulate relative to axis X, but can not be removed from the receiver 102 either through the lower end 122 or through the upper end 123. For facilitating insertion the supporting augments 110 can be arranged with partial overlapping therebetween, as discussed above. In another aspect, the supporting augments 110 can be inserted into the receiver 102 through the lower end 122 of the opening 118, and manipulated into engagement with the fastener ring 112.
The cap 116 with the cap ring 114 can be inserted from the upper end 123 of the receiver 102 such that the cap ring 114 engages the interior slot 119 of the receiver 102. For a particular application, such as spinal fixation, a rod or other longitudinal fixation member 130 can be positioned along the channel 128 and pressed against the cap 116 with a compression member (not shown). Pressing the cap 116 against the head 108 with the compression member secures the bone fastener 104 in a desired orientation.
It will be appreciated that the modularity and shape of the various parts of the bone fixation assembly 100 can provide a compact (non-bulky) bone fixation device, which can be easily assembled during the surgical procedure, or can also be at least partially pre-assembled. Furthermore, the bone fixation assembly 100 can be easily configured for accommodating various surgical situations at the site of operation as desired by the surgeon.
The fixation assembly can be formed from biocompatible materials, such as, for example, metallic materials.
The foregoing discussion discloses and describes merely exemplary arrangements of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.
Claims
1. A bone fixation assembly comprising:
- a bone fastener having a head and a bone-engaging portion;
- a receiver defining an opening along a first axis for receiving the bone fastener at a variable angle, the receiver having an inner articulation surface at a lower portion of the opening; and
- at least one supporting augment coupled to the bone fastener and matingly articulable with the articulation surface of the receiver.
2. The bone fixation assembly of claim 1, wherein the at least one supporting augment includes two separate supporting augments.
3. The bone fixation assembly of claim 1, wherein the articulation surface is substantially spherical and wherein the supporting augment has an outer mating surface that is substantially spherical.
4. The bone fixation assembly of claim 1, wherein a lower end of the opening is configured for receiving the head of the bone fastener therethrough.
5. The bone fixation assembly of claim 4, further comprising a fastener ring, the fastener ring couplable to the head of the bone fastener such that the fastener ring can be inserted assembled to the bone fastener from the lower end of the opening.
6. The bone fixation assembly of claim 5, wherein the fastener ring is supportable on a groove of the supporting augment.
7. The bone fixation assembly of claim 6, wherein the fastener ring is a split ring.
8. The bone fixation assembly of claim 6, wherein the supporting augment is shaped for allowing variable angulation of the fastener.
9. The bone fixation assembly of claim 2, wherein each supporting augment includes a notch on an upper surface of the augment.
10. The bone fixation assembly of claim 8, wherein each supporting augment includes two oppositely inclined end surfaces.
11. The bone fixation assembly of claim 9, wherein each supporting augment is shaped for partial overlapping about the notch during assembly.
12. The bone fixation assembly of claim 8, wherein the supporting augment is further shaped for preventing removal of the fastener when the ring is coupled to the supporting augment and to the head of the fastener.
13. The bone fixation assembly of claim 1, further comprising a fastener cap for coupling the head of the fastener to an inner surface of the receiver.
14. The bone fixation assembly of claim 13, further comprising a cap ring for coupling the fastener cap and the receiver.
15. The bone fixation assembly of claim 14, wherein the receiver defines a channel extending along a second axis generally perpendicular to the first axis.
16. The bone fixation assembly of claim 15, wherein the channel is shaped for receiving a fixation rod above the fastener cap.
17. The bone fixation assembly of claim 14, wherein the cap ring is a split ring.
18. A method for spinal fixation comprising:
- providing a receiver defining an opening along a first axis for receiving a bone fastener at a variable angle, the receiver having an inner articulation surface at a lower portion of the opening;
- inserting the head of the bone fastener into the opening;
- inserting at least one supporting augment into the opening, the at least one supporting augment articulable with the articulation surface;
- coupling the at least one supporting augment to the head of the bone fastener; and
- varying the angle of the bone fastener relative to the first axis by articulating the at least one supporting augment relative to the articulation surface.
19. The method of claim 18, wherein coupling the at least one augment is performed after inserting the head of the bone fastener into the opening.
20. The method of claim 18, wherein inserting the head of the bone fastener into the opening includes inserting the head through a lower end of the opening.
21. The method of claim 20, wherein coupling the at least one supporting augment to the head of the bone fastener includes preventing the head of the bone fastener from withdrawal through the opening.
22. The method of claim 18, wherein coupling the at least one supporting augment to the head of the bone fastener includes coupling a retention member to the at least one supporting augment and to the head of the bone fastener.
23. The method of claim 20, further comprising inserting a cap through an upper end of the opening for engaging the head of the bone fastener.
Type: Application
Filed: Oct 20, 2005
Publication Date: May 24, 2007
Applicant:
Inventors: Moti Altarac (Irvine, CA), Lenny Schaust (Delano, MN), Philip Mellinger (Ladera Ranch, CA)
Application Number: 11/255,138
International Classification: A61F 2/30 (20060101);