Patent Application
20150238233
Immobilization of the spine is a surgical objective for achieving spinal fusion. Spine surgeons utilize various methods and implants to immobilize the spine in an effort to join one vertebra to another. These methods include the utilization of a plate and screws that bridge the gap between vertebrae or intervertebral disc space. There are a number of surgical plates available for this purpose in the lumbar, thoracic, and cervical spine.
In one aspect, provided are systems for stabilizing adjacent superior and inferior vertebrae separated by an intervertebral disc space. The system includes a plate having at least one plate aperture and at least one bone screw sized and shaped to be positioned through the at least one plate aperture. The plate has a first cross-sectional area and thickness near a midline of the plate that is aligned with the intervertebral disc space upon deployment of the system, a second cross-sectional area and thickness located near a superior margin of the plate that is aligned with the superior vertebra upon deployment of the system, and a third cross-sectional area and thickness located near an inferior margin of the plate that is aligned with the inferior vertebra upon deployment of the system. The first cross-sectional area and thickness is greater than the second cross-sectional area and is greater than the third cross-sectional area and thickness such that the plate projects in a fusiform manner both toward and away from the intervertebral disc space.
The plate can be at least partially made of a radiolucent material. The plate can be at least partially made of an implantable polymer. A first plate aperture of the at least one plate aperture can be asymmetric. A first bone screw of the at least one bone screw can be sized and shaped to be advanced along an insertional axis through the first plate aperture. Advancement of the first bone screw can result in a generally perpendicular translation of the plate relative to the insertional axis. A first bone screw of the at least one bone screw can be captured by a superimposition of a second bone screw of the at least one bone screw. The first bone screw can be immediately adjacent the second bone screw. The at least one bone screw can be secured to the plate with a locking mechanism. The at least one bone screw can include a shaft having a threaded region, a proximal head coupled to the shaft, and a threadless segment located distal to the proximal head and proximal to the threaded region. The locking mechanism can include a female thread form within the at least one plate aperture configured to engage the threaded region of the shaft and retain the at least one bone screw within the at least one plate aperture. The locking mechanism can include a tapered conical feature within the at least one plate aperture; and a shell having a generally cylindrical internal bore configured to be positioned coaxially around the threadless segment and a tapered conical external surface sized to form an interference fit with the tapered conical feature. The threadless segment can have a length being equal to or longer than a thickness of the at least one plate aperture through which the at least one bone screw is advanced and a diameter that is less than a major diameter of the threaded region of the shaft. The locking mechanism can include a deformable material forming at least a portion of the at least one aperture that is smaller in diameter than a major diameter of the threaded region of the shaft. Upon rotationally advancing the at least one bone screw through the at least one plate aperture, the threaded region can engage and deform the deformable material until a proximal extent of the threaded region is retained by the deformable material preventing reverse migration of the screw out of the aperture. The deformable material can be an implantable polymer.
In an interrelated aspect, described is a system for stabilizing adjacent superior and inferior vertebrae separated by an intervertebral disc space that includes a plate having at least one plate aperture and at least one bone screw sized and shaped to be positioned through the at least one plate aperture. The plate includes a first margin projecting from the plate and configured to contact the superior vertebra and a second margin projecting from the plate and configured to contact the inferior vertebra. The first and second margins projecting from the plate are configured to asymmetrically compress the intervertebral disc space. Prior to deployment a surface of the plate can be generally more concave than surface features of the adjacent superior and inferior vertebrae onto which the plate is being deployed.
In an interrelated aspect, described is a system for stabilizing adjacent superior and inferior vertebrae separated by an intervertebral disc space including a plate having at least one plate aperture and at least two pairs of projecting elements positioned on a surface of the plate configured to project toward the intervertebral disc space upon deployment of the system on the adjacent vertebrae; and at least one bone screw sized and shaped to be positioned through the at least one plate aperture. The at least two pairs of projecting elements are tapered and serve to align or fix the plate relative to the intervertebral disc space upon deployment of the system.
In an interrelated aspect, described is a system for stabilizing adjacent superior and inferior vertebrae separated by an intervertebral disc space including a plate having at least two plate apertures; a first bone screw sized and shaped to be positioned through a first of the at least two plate apertures along a first insertion axis above the intervertebral disc space; and a second bone screw sized and shaped to be positioned through a second of the at least two plate apertures along a second insertion axis below the intervertebral disc space. The first and second insertion axes of the first and second bone screws above and below the intervertebral disc space are convergent on a point in space. The point can be at least greater than a distance between a midpoint of the first bone screw and the second bone screw. The distance can be less than 50 cm.
Reference is made to the following description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.
Disclosed are intervertebral plate systems configured to be deployed in a patient adjacent the patient's spine. The plate systems described herein can be generally deployed in the spine using lateral and anterior approaches. In some implementations, lateral approaches can be used to access the lumbar and thoracic spine and anterior approaches can be used to access the cervical, thoracic and lumbar spine.
Again with respect to
The plate systems described herein can accommodate and compress intervertebral implants and/or bone grafts positioned within the disc space between the adjacent vertebrae to be fused.
It should be appreciated that other locking mechanisms between the plate and the screw are considered herein. For example, a plate screw interface is considered in which a collapsible bushing is used under the screw head. The collapsible bushing can have a truncated taper lock geometry externally and a slip fit, cylindrical geometry internally such that advancing the distal aspect of the screw head against the upper or proximal portion of the collapsible bushing can result in the bushing being driven within a mating truncated conical locking feature on the plate. In other implementations, the locking mechanism incorporated an unthreaded aperture formed of a compliant deformable material that provides an interference fit with the threadform of the screw upon advancement of the screw through the aperture.
A shell 105 (or pair of shells) can surround a length of the threadless segment 75 such that the shell 105 is positioned coaxially with the threadless segment 75 of the screw 15. The shell 105 can be a rigid element having a bore 110 extending from a proximal extent to a distal extent of the shell 105. The bore 110 can be generally cylindrical. The shell 105 can have a distal diameter that is less than the major diameter of the proximal extent of the threaded region of the screw 15. The external geometry of the surrounding shell 105 can be generally conical and associated with tapered lock dimensions, for example, an angle between two and six degrees (e.g. Morse taper) relative to the longitudinal axis of the shell 105.
A collar 115 can be fixed within an aperture 20 of the plate 10 such that the screw 15 and shell 105 can be advanced through the collar 115. The collar 115 can include an internal bore 118 and be formed of a rigid material. The bore 118 can be conical and tapered such that the bore 118 corresponds with the external taper lock geometry of the shell 105. Linear advancement of the shell 105 within the bore 118 of the collar 115 can result in a friction lock between the shell 105 and the bore 118 of the collar 115. It should be appreciated that the plate 10 may not incorporate a collar 115 and the friction lock can occur between the shell 105 and the aperture 20 of the plate 10. When the shaft 35 of the screw 15 is advanced into the vertebral bone, the shell 105 surrounding the threadless segment 75 of the screw 15 can advance within the rigid taper lock of the plate 10 resulting in a friction lock between the plate 10 and the surrounding shell 105. The friction lock can retain the screw 15 while permitting the screw 15 to be freely rotated relative to both the surrounding shell 105 and the plate 10. The external geometry of the collar 115 can provide a way for securing the collar 115, which can be a rigid component, to the plate 10, which can be an injection molded body. For example, the collar 115 can have upper and lower flanges that can prevent the migration of the collar 115 relative to the plate 10. The external or outer surface of one or both of the flanges can have a surface geometry, such as a flat, splined, knurled or other surface feature that can prevent the rotation of the collar 115 about its generally cylindrical axis with respect to the plate 10.
One or more regions of the plate 10 in addition to the aperture 20 can be formed of a deformable material such as an implantable polymer. The deformable material of the plate 10 can be the same as or a different material as the deformable material 22 of the aperture 20. One or more regions of the plate 10 can also be formed of a radiolucent material. Polymers such as PEEK are radiolucent and can provide an advantage that they do not impede observation of the implantation site. For example, a plate system 5 formed at least partially of radiolucent materials like PEEK can allow for assessment of the progression of bone growth between vertebrae during the post-operative period, which is generally assessed with the use of X-ray observation, either routine or with computer assisted tomography or CAT scans. Metal plates are generally stiffer than the bones to which they are attached. The transfer of loads from one vertebra to another via the plate can be in part stress shielded by the relatively stiff intervening metal plate. Polymers have a modulus that is more compliant than most implanted metals. Comparable immobilization using polymeric materials such as PEEK can be achieved although the cross sectional area may be greater than metal implants.
One or more of the screws inserted through the apertures in the plate can be captured by a superimposition of one or more of the other screws inserted through a different aperture in the plate. As shown in
As described above, advancement of the screw can result in a generally perpendicular translation of the plate 10 relative to the insertional axis of the screw 10. A first bone screw 15 can be sized and shaped to be positioned through an aperture along a first insertion axis, for example above the intervertebral disc space. A second bone screw 15 can be sized and shaped to be positioned through another aperture along a second insertion axis, for example below the intervertebral disc space. The first and second insertion axes of the first and second bone screws above and below the intervertebral disc space can be convergent on a point in space. The point in space can be at least greater than a distance between a midpoint of the first bone screw and the second bone screw. The distance can be less than 50 centimeters (see
As shown in
Prior to deployment, the deep surface 30 of the plate 10 can be generally more concave than surface features of the adjacent vertebrae to which the plate 10 is to be deployed that align with the plate 10. The plate can initially confer an increased convergence of the vertebrae to which the plate is affixed on the side of the disc space away from the side on which the plate is positioned, relative to the side to which the plate is immediately located. With additional screw advancement, concurrent plate compression and resistive loading of an intervertebral disc space implant, the plate 10 can bend or warp. The bending or warping of the plate 10 can lessen the concavity toward the disc space and result in “dynamization” of the plate 10. This can enhance stability and reduce the inclination for distraction of the opposite side of the disc space D as might otherwise occur with ipsilateral plate compression. This provides an asymmetric “angled” or “dynamic” compression of the intervertebral disc space, particularly when provided in conjunction with an intervening intervertebral device such as a cage or a stent. By compressing the disc space initially and preferentially on the side opposite the plate's affixed position, the resistance afforded by the intervertebral cage, spacer, stent, implant or other device that may be generally non-compressible can cause the plate to bow or “dynamize.”
Now with respect to
While this specification contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. It should also be appreciated that sizes, materials, surface patterns and finishes can be altered to suit uses including extreme environments and loading to achieve required performance in those situations.
Although embodiments of various methods, systems and devices are described herein in detail with reference to certain versions, it should be appreciated that other versions, embodiments, methods of use, and combinations thereof are also possible. Therefore the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
This application claims the benefit of priority under 35 U.S.C. §119(e) of co-pending U.S. Provisional Patent Application Ser. No. 61/681,521, filed Aug. 9, 2012. Priority of the aforementioned filing date is hereby claimed and the disclosure of the provisional patent application hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/054393 | 8/9/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61681521 | Aug 2012 | US |
