Lockable Pedicle Fastener
A spinal fixation system comprising at least one fastener having a fastener head at a proximal end and at least one body. The body comprises a rod receiving channel for receiving a fixation rod, a pressure cap for engaging the fastener head, and a fastener head receiving chamber for retaining the fastener head within the body. The fastener head receiving chamber allows for multi-axial movement of the body in relation to the fastener when the pressure cap is disengaged from the fastener head. The body is secured in a mono-axial position in relation to the fastener when the pressure cap is biased against the fastener head.
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TECHNICAL FIELDThe embodiments described and claimed herein relate to a spinal fixation system comprising a multi-axial pedicle screw that is operable to be locked in a mono-axial position.
BACKGROUND ARTVarious spinal fixation systems involving connecting fastener elements (e.g., pedicle screws) to elongated supports (e.g., fixation rods) for the purposes of vertebral fixation have been proposed. Two varieties include mono-axial fastener elements and multi-axial fastener elements. Both have distinct benefits. Accordingly, there is a need for spinal fixation systems involving connecting fastener elements (e.g., pedicle screws) to elongated supports (e.g., fixation rods) that offer the benefits of both mono-axial elements and multi-axial elements.
BRIEF SUMMARYThe embodiments described and claimed herein relate to a spinal fixation system that includes a body and a fastener, wherein a pressure cap is operable to provide the benefits of both a multi-axial assembly and a mono-axial assembly. In one embodiment, the spinal fixation system comprises at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface. It also comprises at least one body, wherein the body has a proximal portion and a distal portion. The proximal portion comprises a rod receiving channel for receiving a fixation rod, an external attachment feature, and a pressure cap disposed at a distal end of the proximal portion wherein a distal end of the pressure cap comprises an interior surface contoured to fit against the substantially spherical surface of the screw head. The distal portion comprises an internal attachment feature for engaging the external attachment feature of the proximal portion, wherein the engaging of the internal attachment feature with the external attachment feature secures the upper body to the lower body, a screw head receiving chamber disposed at a distal end of the distal portion for retaining the screw head within the body, and an external surface operable to engage a drive tool that operates to join the internal attachment feature with the external attachment feature and further cause the pressure cap to apply a bias against the screw head. The screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head. And the body can be secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
In another embodiment, the spinal fixation system comprises at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface, and at least one body comprising a rod receiving channel for receiving a fixation rod, an internal attachment feature, and a screw head receiving chamber disposed at a distal end of the body for retaining the screw head within the body. The spinal fixation system further comprises at least one pressure cap disposed at a proximal end of the screw head receiving chamber. The pressure cap comprises a distal end with an interior surface contoured to fit against the substantially spherical surface of the screw head for engaging the screw head, an external attachment feature for engaging the internal attachment feature of the body, wherein the engaging of the internal attachment feature with the external attachment feature secures the body to the pressure cap and allows the pressure cap to travel distally until the distal end is biased against the screw head, and an internal surface operable to engage a driving tool operable to adjust the position of the pressure cap in a proximal or distal direction. The screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head. And the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
In another embodiment, the spinal fixation system comprises at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface and at least one body. The body has a proximal end and a distal end and further comprises a rod receiving channel for receiving a fixation rod wherein the rod receiving channel is disposed adjacent the proximal end of the body, and a screw head receiving chamber disposed adjacent the distal end of the body. The rod receiving channel and the screw head receiving chamber are operatively connected. The spinal fixation system further comprises a pressure cap for engaging the screw head. The pressure cap comprises a proximal portion disposed at least partially within the rod receiving channel, a distal portion disposed at least partially within the screw head receiving chamber, at least two lateral sides extending from the proximal portion to the distal portion, a screw head interface disposed adjacent to the distal portion of the pressure cap, a rod receiving surface disposed proximal to the screw head interface, and an aperture extending from the rod receiving surface to the screw head interface. The pressure cap is operable to travel from within the rod receiving channel towards the screw head receiving chamber of the body when the fixation rod or a tool is used to apply a distal bias to the rod receiving surface such that the screw head interface of the pressure cap is biased against the screw head in the screw head receiving chamber. The spinal fixation system also comprises a locking mechanism for securing the pressure cap in a biased position against the screw head. The screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head. And the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
In another embodiment, the spinal fixation system comprises at least one fastener having a fastener head at a proximal end, and at least one body. The body comprises a rod receiving channel for receiving a fixation rod, a pressure cap for engaging the fastener head, and a fastener head receiving chamber for retaining the fastener head within the body. The fastener head receiving chamber allows for multi-axial movement of the body in relation to the fastener when the pressure cap is disengaged from the fastener head. The body is secured in a mono-axial position in relation to the fastener when the pressure cap is biased against the fastener head.
These and other features, aspects, objects, and advantages of the embodiments described and claimed herein will become better understood upon consideration of the following detailed description, appended claims, and accompanying drawings where:
It should be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the embodiments described and claimed herein or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the inventions described herein are not necessarily limited to the particular embodiments illustrated. Indeed, it is expected that persons of ordinary skill in the art may devise a number of alternative configurations that are similar and equivalent to the embodiments shown and described herein without departing from the spirit and scope of the claims.
Like reference numerals will be used to refer to like or similar parts from Figure to Figure in the following detailed description of the drawings.
DETAILED DESCRIPTIONReferring first to
Also shown in
As shown in
The embodiment shown in
When the pressure cap 56 is biased against the fastener head 32, the body 14 can be secured in a mono-axial position in relation to the fastener 12. The pressure cap 56 may be transitioned from a disengaged position, wherein the body 14 retains multi-axial movement in relation to the fastener 12, to a biased position, wherein the body 14 is restricted to mono-axial movement in relation to the fastener 12, by a multitude of mechanisms. For example, as shown in
Referring now to
As can be seen in the embodiment shown in
Also shown in
The assembly 60 shown in
As shown in
When the pressure cap 72 is disengaged from the fastener head 32, the fit between the distal interior surface 78 of the pressure cap 72 and the fastener head 32 allows the body 62 to pivot along multiple axes in relation to the fastener 12. This multi-axial movement allows the fastener to be placed in the vertebral body much easier than a mono-axial fixation system. A mono-axial fixation system requires very accurate placement of the fastener in order to properly seat the fixation rod 40 for connection to another fixation assembly. Mono-axial fixation systems require contouring of the fixation rod 40 to account for the static placement of the fastener assembly. A multi-axial fastener assembly, such as is available with the fastener assembly of the present application, requires less accurate placement of the fastener into the vertebral body as well as less contouring of the fixation rod 40 to achieve proper installation of the spinal fixation system.
When the pressure cap 72 is biased against the fastener head 32, the body 62 can be secured in a mono-axial position in relation to the fastener 12. The pressure cap 72 may be transitioned from a disengaged position, wherein the body 62 retains multi-axial movement in relation to the fastener 12, to a biased position, wherein the body 62 is restricted to mono-axial movement in relation to the fastener 12, by a multitude of mechanisms. For example, as shown in
Referring now to
As can be seen in the embodiment shown in
Although not shown in
The assembly 90 shown in
When the pressure cap 100 is disengaged from the fastener head 32, the fit between the distal interior surface 108 of the pressure cap 100 and the fastener head 32 allows the body 92 to pivot along multiple axes in relation to the fastener 12. This multi-axial movement allows the fastener to be placed in the vertebral body much easier than a mono-axial fixation system. A mono-axial fixation system requires very accurate placement of the fastener in order to properly seat the fixation rod for connection to another fixation assembly. Mono-axial fixation systems require contouring of the fixation rod to account for the static placement of the fastener assembly. A multi-axial fastener assembly, such as is available with the fastener assembly of the present application, requires less accurate placement of the fastener into the vertebral body as well as less contouring of the fixation rod to achieve proper installation of the spinal fixation system.
The pressure cap 100 can travel in a longitudinal direction, either proximally or distally. When the pressure cap 100 is in a disengaged position, the pressure cap 100 can be moved in a distal direction by applying a pressure to the rod receiving surface 110 using a tool or a fixation rod in contact with the rod receiving surface 110. As the pressure 100 cap travels distally, the distal interior surface 108 of the pressure cap 110 will become biased against the fastener head 32.
When the pressure cap 100 is biased against the fastener head 32, the body 92 can be secured in a mono-axial position in relation to the fastener 12. The pressure cap 100 may be transitioned from a disengaged position, wherein the body 92 retains multi-axial movement in relation to the fastener 12, to a biased position, wherein the body 92 is restricted to mono-axial movement in relation to the fastener 12. For example, the pressure cap 100 shown in
In some embodiments, the fastener assembly 90 also comprises a locking mechanism for securing the pressure cap 100 in a biased position, thereby locking the body 92 in a mono-axial state. One example can be seen in
Another embodiment of a locking mechanism is shown in
Yet another embodiment of a locking mechanism is shown in
All embodiments of the fastener assembly can be delivered to the user and surgically implanted in either pre-assembled form or modular form. The elements of the fastener assembly can be manufactured from any medical-grade material suitable for its purpose.
Although the embodiments described and claimed herein have been described in considerable detail with reference to certain embodiments, one skilled in the art will appreciate that the inventions described and claimed herein can be practiced by other than those embodiments, which have been presented for purposes of illustration and not of limitation. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
Claims
1. A spinal fixation system, comprising:
- at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;
- at least one body, wherein the body has a proximal portion and a distal portion;
- the proximal portion comprising: a rod receiving channel for receiving a fixation rod; an external attachment feature; and a pressure cap disposed at a distal end of the proximal portion wherein a distal end of the pressure cap comprises an interior surface contoured to fit against the substantially spherical surface of the screw head;
- the distal portion comprising: an internal attachment feature for engaging the external attachment feature of the proximal portion, wherein the engaging of the internal attachment feature with the external attachment feature secures the upper body to the lower body; a screw head receiving chamber disposed at a distal end of the distal portion for retaining the screw head within the body; and an external surface operable to engage a drive tool that operates to join the internal attachment feature with the external attachment feature and further cause the pressure cap to apply a bias against the screw head;
- wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and
- wherein the body can be secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
2. The spinal fixation system of claim 1, further comprising:
- a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.
3. The spinal fixation system of claim 2, wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body.
4. The spinal fixation system of claim 1, wherein the external attachment feature of the proximal portion of the body comprises external threads and the internal attachment feature of the distal portion of the body comprises complementary internal threads.
5. The spinal fixation system of claim 1, wherein the external surface of the distal portion of the body comprises a perimeter of three or more flat sides for engaging the drive tool.
6. The spinal fixation system of claim 1, wherein the at least one screw is a bone screw.
7. The spinal fixation system of claim 6, wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine.
8. The spinal fixation system of claim 1, wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw.
9. The spinal fixation system of claim 1, wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head.
10. A spinal fixation system, comprising:
- at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;
- at least one body, the body comprising: a rod receiving channel for receiving a fixation rod; an internal attachment feature; a screw head receiving chamber disposed at a distal end of the body for retaining the screw head within the body;
- at least one pressure cap disposed at a proximal end of the screw head receiving chamber and wherein the pressure cap comprises: a distal end with an interior surface contoured to fit against the substantially spherical surface of the screw head for engaging the screw head; an external attachment feature for engaging the internal attachment feature of the body, wherein the engaging of the internal attachment feature with the external attachment feature secures the body to the pressure cap and allows the pressure cap to travel distally until the distal end is biased against the screw head; and an internal surface operable to engage a driving tool operable to adjust the position of the pressure cap in a proximal or distal direction;
- wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and
- wherein the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
11. The spinal fixation system of claim 10, further comprising:
- a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.
12. The spinal fixation system of claim 11, wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body.
13. The spinal fixation system of claim 10, wherein the internal attachment feature of the at least one body comprises internal threads and the external attachment feature of the at least one pressure cap comprises complementary external threads.
14. The spinal fixation system of claim 10, wherein the internal surface of the pressure cap comprises a perimeter of three or more flat sides for engaging the driving tool.
15. The spinal fixation system of claim 10, wherein the at least one screw is a bone screw.
16. The spinal fixation system of claim 15, wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine.
17. The spinal fixation system of claim 10, wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw.
18. The spinal fixation system of claim 10, wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head.
19. A spinal fixation system, comprising:
- at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;
- at least one body, the body having a proximal end and a distal end and further comprising: a rod receiving channel for receiving a fixation rod wherein the rod receiving channel is disposed adjacent the proximal end of the body; and a screw head receiving chamber disposed adjacent the distal end of the body; wherein the rod receiving channel and the screw head receiving chamber are operatively connected;
- a pressure cap for engaging the screw head, the pressure cap comprising: a proximal portion disposed at least partially within the rod receiving channel; a distal portion disposed at least partially within the screw head receiving chamber; at least two lateral sides extending from the proximal portion to the distal portion; a screw head interface disposed adjacent to the distal portion of the pressure cap; a rod receiving surface disposed proximal to the screw head interface; and an aperture extending from the rod receiving surface to the screw head interface; wherein the pressure cap is operable to travel from within the rod receiving channel towards the screw head receiving chamber of the body when the fixation rod or a tool is used to apply a distal bias to the rod receiving surface such that the screw head interface of the pressure cap is biased against the screw head in the screw head receiving chamber;
- a locking mechanism for securing the pressure cap in a biased position against the screw head;
- wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and
- wherein the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.
20. The spinal fixation system of claim 19, further comprising:
- a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.
21. The spinal fixation system of claim 20, wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body.
22. The spinal fixation system of claim 19, wherein the at least one screw is a bone screw.
23. The spinal fixation system of claim 22, wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine.
24. The spinal fixation system of claim 19, wherein the aperture extending from the rod receiving channel to the screw head receiving chamber is operable to allow a tool to be inserted therethrough to apply torque to the screw.
25. The spinal fixation system of claim 19, wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head.
26. The spinal fixation system of claim 19, wherein the locking mechanism comprises:
- a linear rack of one or more teeth disposed on the external surface of one or more of the lateral sides of the pressure cap; and
- one or more pawls disposed within the rod receiving channel of the body, operable to engage the one or more teeth of the pressure cap such that when the one or more pawls engage at least one of the one or more teeth, the pressure cap is secured in a biased position against the screw head.
27. The spinal fixation system of claim 26, wherein the one or more teeth are asymmetrical in shape such that each tooth has a moderate slope on a distal edge and a much steeper slope on a proximal edge wherein interaction of the one or more pawls with the one or more teeth allows the pressure cap to travel distally but prevents travel in the proximal direction when the pawl is engaged.
28. The spinal fixation system of claim 27, wherein the one or more pawls comprise a spring-loaded clip.
29. The spinal fixation system of claim 19, wherein the rod receiving channel further comprises at least two lateral walls and wherein the locking mechanism comprises:
- an undercut disposed within one or more of the lateral walls of the rod receiving channel;
- one or more flanges disposed at the proximal end of the pressure cap;
- wherein, upon a distal pressure being applied to the rod receiving surface, the pressure cap is operable to travel distally within the rod receiving channel such that when the one or more flanges engage the undercut of the rod receiving channel the pressure cap is secured in a biased position against the screw head.
30. The spinal fixation system of claim 19, wherein the locking mechanism comprises:
- one or more bores disposed within the body at a proximal end of the screw head receiving chamber and extending from an external surface of the body to an internal surface of the screw head receiving chamber;
- one or more wedge elements disposed within the one or more bores wherein the one or more wedge elements are operable to travel laterally within the bores;
- one or more recesses disposed within the pressure cap proximal to the screw head interface; and
- wherein pressure applied in a medial direction to the one or more wedge elements causes a medial end of the one or more wedge elements to fit between a proximal surface of the one or more bores and a distal surface of the one or more recesses in a wedged position such that in the wedged position the pressure cap is secured in a biased position against the screw head.
31. A spinal fixation system, comprising:
- at least one fastener having a fastener head at a proximal end;
- at least one body, wherein the body comprises: a rod receiving channel for receiving a fixation rod; a pressure cap for engaging the fastener head; and a fastener head receiving chamber for retaining the fastener head within the body;
- wherein the fastener head receiving chamber allows for multi-axial movement of the body in relation to the fastener when the pressure cap is disengaged from the fastener head; and
- wherein the body is secured in a mono-axial position in relation to the fastener when the pressure cap is biased against the fastener head.
32. The spinal fixation system of claim 31, further comprising:
- a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.
33. The spinal fixation system of claim 32, wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body.
34. The spinal fixation system of claim 31, wherein the at least one screw is a bone screw.
35. The spinal fixation system of claim 34, wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine.
36. The spinal fixation system of claim 31, wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw.
37. The spinal fixation system of claim 31, wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head.
Type: Application
Filed: Nov 8, 2013
Publication Date: May 14, 2015
Applicant: BLACKSTONE MEDICAL, INC. (Lewisville, TX)
Inventors: Tara Ziolo (Hewitt, NJ), Michael A. Hammer (Cranford, NJ), John Lovell (North Bergen, NJ), Francesco A. Larosa (Neptune, NJ), Nelson Li (Hillsdale, NJ)
Application Number: 14/075,795
International Classification: A61B 17/70 (20060101);