Patent Application
20080114401
The present application is directed to posterior fixation devices and, more particularly, to devices that attach to a posterior surface of a vertebral members for securing one or more elongated members.
The spine is divided into four regions comprising the cervical, thoracic, lumbar, and sacrococcygeal regions. The cervical region includes the top seven vertebral members identified as C1-C7. The thoracic region includes the next twelve vertebral members identified as T1-T12. The lumbar region includes five vertebral members L1-L5. The sacrococcygeal region includes nine fused vertebral members that form the sacrum and the coccyx. The vertebral members of the spine are aligned in a curved configuration that includes a cervical curve, thoracic curve, and lumbosacral curve.
Various conditions may lead to damage of the vertebral members and/or intervertebral discs. The damage may result from a variety of causes including a specific event such as trauma, a degenerative condition, a tumor, or infection. Damage to the intervertebral discs and vertebral members can lead to pain, neurological deficit, and/or loss of motion. Elongated members, such as but not limited to rods, bars, and blades, may extend along the spine to redistribute stresses and/or restore proper alignment of the vertebral members. The elongated members may be substantially straight, or include a curved configuration to conform to the curvature of the spine.
The elongated members should be securely fixed to one or more of the vertebral members. Fixation often proves difficult because of the varied shape and dimensions of the vertebral members.
The present application is directed to devices and methods for attaching one or more elongated members to a posterior surface of a vertebral member. The devices may include a body with a first face that contacts the vertebral member and a second opposite face. A hook may extend outward from the first face to engage the vertebral member. The body may also include one or more receivers to receive the elongated members. An engagement member may be movably connected to the body. The engagement member may include a first section that contacts the body, and a second section that includes a second hook. The engagement member may be positioned relative to the body to adjust a distance between the first and second hooks to attach the body to the vertebral member. A fastener may secure the engagement member to the body at the desired position. The fastener may also attach the one or more elongated members to the body.
The present application is directed to fixation devices and systems for attaching one or more elongated members to one or more vertebral members. The fixation devices include a body with hooks that cooperate to attach to the vertebral member. The body also includes one or more receivers for receiving the elongated members. A fastener may attach to the body to secure the position of the hooks, and the one or more elongated members to the body. The devices may be used on two or more vertebral members to form a fixation system. The fixation system extends along a section of the spine to position and/or redistribute stresses to the vertebral members.
Each of the fixation devices 10 includes a body 20 that extends across a section of the vertebral member 100. As illustrated in
The body 20 includes the inner surface 27 that contacts the posterior surface of the vertebral member 100 (i.e., faces in an anterior direction) and an outer surface 28 that faces away from the vertebral member 100 (i.e., faces in a posterior direction). One or more slots 23 may extend into the outer surface 28 to receive the elongated members 90. The slots 23 may be positioned at a variety of distances outward from the first section 21. The slots 23 may further include a variety of shapes and widths to receive the elongated members 90. Slots 23 may include a depth such that the elongated member 90 is recessed below the outer surface 28 when positioned within the slot 23, or include a depth so the elongated member 90 may extend above the outer surface 28.
In one embodiment as illustrated in
Body 20 further includes a hook 25 that extends outward from the inner surface 27. Hook 25 may extend outward from an edge of the body 20. In one embodiment, hook 25 extends outward from the superior edge of the body 20 to contact against an edge of the vertebral member 100. Hook 25 may also be laterally aligned with the first section 21 of the body 20 and may be substantially aligned with a centerline of the vertebral member 100 when the body 20 is attached.
The hook 25 includes a first section 26 that extends outward from the inner surface 27, and a second section 29 that extends at an angle from the end of the first section 26. The hook 25 is constructed for the first section 26 to extend along a superior edge of the lamina of the vertebral member 100, and the second section 29 to extend along an anterior edge of the lamina. As illustrated in
The body 20 may further include a slot 24 that extends into the outer surface 28 of the first section 21. Slot 24 may be angled with a ramped lower surface that extends within the body 20 between a first sidewall and the outer surface 28. In one embodiment, slot 24 extends through the sidewall and terminates within a central portion of the body 20. In another embodiment, slot 24 extends within the body 20 between the first sidewall and a second, opposite sidewall. The slot 24 is further aligned with the hook 25 and is sized to receive an engagement member 50.
The engagement member 50 is movably attached to body 20. One embodiment of the engagement member 50 is illustrated in
Hook 52 is shaped to engage a side of the vertebral member 100. Hook 52 works in combination with hook 25 to press in opposite directions and hold the central portion of the laminar. This forms a clamp that is stable in cephalad-caudal and pull-out directions. Hook 52 may include a variety of shapes and sizes similar to the hook 25 described above. Hook 52 may be axially aligned with the arm 51 as illustrated in
The engagement member 50 may also include other shapes and sizes to attach to the vertebral members 100.
The engagement member 50 may be constructed as a single piece, or multiple pieces. In the embodiments of
Body 20 may be attached to the vertebral member 100 in a variety of configurations. In one manner, body 20 is positioned for the hook 25 to engage a superior edge of the vertebral member 100. Another manner includes the body 20 being positioned with the hook 25 engaging an inferior edge.
The engagement member 50 is secured to the body 20 with a fastener 30. In one embodiment, fastener 30 includes one or more fixation members 31 that attach at the outer surface 28 of the body 20. In one embodiment as illustrated in
A capture member 32 may also be position below the fixation member 31. In one embodiment, capture member 32 includes a central opening sized to fit around the threaded bolt 33. Capture member 32 includes a width to extend across the entirety or a limited section of the slots 23 to maintain the elongated members 90 within the slots 23. Capture member 32 may include a width that is substantially the same or greater than the fixation member 31. In one embodiment, the capture member 32 extends to the slots 32, but the fixation member 31 includes a shortened width that does not extend to the slots 23. Therefore, the capture member 32 maintains the members 90 within slots 23, but the fixation nut 31 does not.
The threaded bolt 33 may include an extended length as illustrated in
One or more attachment members 40 may further attach the body 20 to the vertebral member 100. Attachment members 40 include a shaft 41 that extends from the body 20, and a pivoting foot 42 at the lower end to contact the posterior surface of the vertebral member 100. The shaft 41 fits within an aperture that extends through the body 20. Shaft 41 may include threads with rotation causing the shaft to move into and out of the body 20. An outer end of the shaft 41 may further include a tool engaging surface, such as a polygonal configuration. Feet 42 are pivotally attached to an inner end of the shaft 41 and are adjustable to accommodate the varied surface of the vertebral member 100. Feet 42 may include an enlarged contact area for increased contact with the posterior surface of the vertebral member 100. In one embodiment, attachment members 40 are positioned at each of the wings 22. In one embodiment, an attachment member 40 is positioned on each of the wings 22. The members 40 work in combination to control the positioning of the body 20.
The stability of the device 10 is based on a multi-directional equilibrium of control forces from the various attachment points. In one embodiment, hooks 25, 52 press in opposite directions and hold the central portion of the laminar, while opposing attachment members 40 press down to the posterior surface of the laminar. The combination of the hooks 25, 52 and attachment members 40 actively controls both anterior-posterior and medial-lateral movements. The relative positioning of these members also controls any rotational movement.
Installation of the device 10 on the posterior of the vertebral member 100 may initially require removal of the spinous process. The removal may be performed by various measures known in the art. Once removed, the body 20 is placed on the posterior surface of the vertebral member 100. Initially, the hook 25 may capture the vertebral member 100 with the first section 26 extending along a first edge of the vertebral member 10 and the second section 29 positioned a second edge of the vertebral member 100. With the hook 25 positioned, the remainder of the body 20 is aligned relative to the vertebral member 100. The first section 21 may be aligned on the centerline of the vertebral member 100, with the wings 22 extending laterally outward from the centerline. Further, the inner surface 27 is positioned in contact with the posterior surface of the vertebral member 100.
After positioning the body 20, the engagement member 50 is adjusted to cooperate with the hook 25. The one or more hooks 52 engage the vertebral member 100, and then the arm 51 is slid within the slot 24. The cooperation between the one or more hooks 52 and hook 25 captures the vertebral member. In one embodiment, the arm 51 may be moved an amount causing the hooks 25, 52 to apply a compressive force to the vertebral member 100. The one or more attachment members 40 may further be positioned with the feet 42 contacting the posterior surface to further solidify the attachment of the body 20.
The one or more elongated members 90 are placed with the slots 23 of the body 20. The fastener 30 may then be used to extend over the slots 23 and prevent removal of the elongated members 90. The fastener 30 further locks the position of the engagement member 50.
A cap 70 may attach to the outer surface 28 of the body 20.
Cap 70 may also include a connector 72 that attaches to the elongated member 90. Connector 72 may include a clip on an underside that extends around and attaches to the elongated member 90. In one method of attaching the elongated member 90 to the body 20, the member 90 is initially attached to the cap 70 and then fixed to the body 20 together with the cap 70. As illustrated in
The fixation system 200 may be comprised of one or more devices 10. The devices 10 may be attached to vertebral members 100 that are adjacent, or spaced apart. Further, the fixation system may include one or more elongated members 90 that extend along the spine.
Fixation system 200 may be used alone, or in combination with other structures.
In some of the embodiments described above, the arm 51 of the engagement member 50 is positioned within a slot 24 in the body 20. In another embodiment, the arm 51 is simply placed on the outer surface 28 of the body 20. The fastener 30 applies a compressive force to capture the arm 51 against the outer surface 28. In one embodiment, the arm 51 includes a slot sized to receive the threaded bolt 33 or shaft of the fastener 30.
In one embodiment, the body 20 includes a first section 21 and a pair of wings 22 that extend laterally outward. In another embodiment, body 20 may include a single wing 22 extending outward from the first section 21. This embodiment may be used when the fixation system 200 anchors a single elongated member 90 to the vertebral members 100.
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, “superior”, “inferior”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
