ANTERIOR CERVICAL PLATE
An anterior cervical plate has a lower surface adapted to engage the cervical spine and a top surface. At least one location along the plate there are two transversely aligned bone screw holes. A locking element is pivotally mounted between these two bone screw holes for movement between an open position which uncovers the two bone screw holes and a locking position wherein the locking element at least partially covers each of the two bone screw holes. A positive positioning structure positively positions the locking element in the locking position.
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This invention relates to an anterior cervical plate, and in particular it relates to such a plate with a new and improved locking element.
It is known to provide an anterior cervical plate for attachment to the anterior of two or more cervical vertebrae for the purpose of immobilizing, stabilizing and/or aligning those vertebrae. The plates can be used for a variety of conditions including for example providing added strength and rigidity after fusion of adjacent vertebrae, securing vertebrae together where an intervening vertebrae has been removed and replaced, correcting spinal deformities, and correcting instability caused by trauma, tumors, advanced degenerative discs, infection or congenital or acquired deformities.
Cervical plates of the present type are generally elongated so as to span the distance between two, three, four or more vertebrae, as required in a given situation. The plates are generally curved transversely so as to fit the curvature of the vertebrae to which they are attached. Additionally, plates of this type are generally concave longitudinally thereof to match the curvature of the cervical spine. Cervical plates of this type are provided with holes for bone screws. Holes are drilled into the adjacent vertebrae by instruments which are known in the art, after which the cervical plate is attached by bone screws which pass through the holes in the cervical plate for securing the plate to the adjacent vertebrae.
Many cervical plates of the present type are known, each having various arrangements for securing the bone screws. Such arrangements are shown in prior U.S. Pat. Nos. 5,364,399; 5,549,612; 6,193,721; 6,224,602; 6,235,034; 6,383,186; and 6,454,771. Notwithstanding the development of the prior art to date, a need exists for improvements in arrangements for securing the bone screws in place after the bone screws have secured the cervical plate onto the adjacent vertebrae.
It is a purpose of the present invention to provide an anterior cervical plate of the type for attachment to cervical vertebrae for stabilizing, immobilizing and/or aligning those vertebrae, which plate has a new and improved arrangement for securing the bone screws in place after the cervical plate has been attached to the cervical vertebrae.
In accordance with the present invention, the cervical plate includes a number of bone screw holes for attaching the cervical plate to the vertebrae. Specifically, in accordance with the present invention there is provided at least one pair of adjacent bone screw holes, preferably transversely aligned, wherein the cervical plate has a locking element mounted between the adjacent bone screw holes and movable between a first, open position where it uncovers the two bone screw holes to permit insertion there through of the bone screws and a second, locking position whereat the locking element overlies at least a portion of each of the two bone screw holes, to lock those bone screws in place. The locking element of the present invention is intended essentially to prevent the screws from backing out, i.e., it is not intended to be a force exerting member to exert a downward force on tightened bone screws.
In accordance with one arrangement of the present invention, an elongated locking element is pivotally mounted on a surface area of the cervical plate between two adjacent bone screw holes. This locking element is movable to a first position whereat it completely uncovers the two adjacent holes so as to permit the insertion of bone screws there through. The locking element is then arranged to be pivoted to partially cover the two bone screw holes with the bone screws secured in place there beneath.
The present invention provides various arrangements for effecting the pivotal connection between the plate and the locking element. In one arrangement the plate may have a raised boss onto which is pivotally mounted a locking element having an opening there through. In another arrangement the plate itself can have an opening and the locking element can have a raised boss on the lower side thereof which projects through the through hole in the plate. In another arrangement, the locking element can have a central opening and the plate can have a through hole, both of which cooperate with a third element, a post which passes through the opening and the through hole.
Another feature of the present invention is the provision of a structure to positively position the locking element in its locking position. For this purpose, a protrusion on either the bottom of the locking element or the surface of the plate can be arranged to be snap fitted into a recess or indentation in the other of the cervical plate or locking element. Preferably, the protrusions will be in the form of bumps on the surface of the plate and the indentions will be in the form of recesses on the bottom of the locking element, wherein the bumps and recesses are aligned to positively position the locking element when it is in its locking position. The bottom of the locking element may include recessed ramps which ride over the bumps as the locking element is initially turned from its open position to its locking position. The bumps would then ride up the recessed ramps and then snap into place in the recesses when the locking element has reached its locking position.
Turning of the locking element between its open and locking positions can be accomplished by using a tool, and for this purpose the locking elements are provided with a pair of openings, offset relative to the pivot axis, to receive such a tool.
The present invention is applicable to cervical plates of a virtually limitless number of configurations. Cervical plates are generally referred to by the number of levels that they overlie, wherein the word “level” refers to the number of intervening intervertebral spaces that are spanned. Thus, for example, a three level cervical plate would span the four vertebrae beyond and between the three intervertebral spaces. The plate can be connected at some places by a single central bone screw through a single central bone screw hole instead of by the two adjacent bone screw holes which include the locking element of the present invention. In virtually all configurations, an opening will be provided between adjacent vertebrae for viewing the intervening intervertebral space.
In any configuration the cervical plate would almost always be attached to the upper and lower vertebrae. Connections of the cervical plate between the upper and lower vertebrae would depend on the level of the cervical plate and the nature of the surgery performed on the spine adjacent to the cervical plate. For example, if the surgery involved replacing only the discs and leaving the vertebrae intact in a three or four level cervical plate, then screws might be attached to the intermediate vertebrae. However, a long plate such as a three level or four level plate would more likely be used after a corpectomy, wherein the intervening vertebrae and discs would have been removed and replaced with a bone plug/graft or a mesh/cage implant. In these cases, it is unlikely that screws would be attached between the upper and lower vertebrae, although it might be desirable to place one or two screws into a bone plug/graft.
13 Thus, it is an object of the present invention to provide a new and improved anterior cervical plate.
It is another object of the present invention to provide a new and improved locking element in combination with a cervical plate for locking a pair of bone screws in adjacent bone screw openings of the plate.
These and other objects of the present invention will be apparent from the detailed description to follow, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGSThere follows a detailed description of preferred embodiments of the present invention which are to be read together with the drawings wherein:
Referring now to the figures, like elements are represented by like numerals throughout the several views.
An anterior cervical plate of the type with which the present invention is concerned attaches to the anterior surface of a plurality of cervical vertebrae to perform a number of different functions including stabilizing, aligning and immobilizing two or more adjacent vertebrae. These will be described generally with respect to the diagrammatic view of
A cervical plate can have different openings serving different purposes. In
Referring to
Referring to
A feature of the present invention is an elongated locking element 30 which is mounted so as to move between an open position as shown at recessed area 11 of
The embodiment of
Cervical plate 50 of
For convenience,
Referring to
Although the operation of the present invention will be apparent from the preceding discussion, for convenience the operation will be summarized herein. First, after the problem of the cervical spine has been surgically repaired, the anterior cervical plate is placed against the anterior of the cervical vertebrae. Initially it is held there by the spikes 41, 42 and/or by fixation pins passing through the openings 23, 24. The method of preparing the holes in the vertebral bodies for the bone screws is well known, conventional and need not be further described herein.
At the recessed areas which include the locking element of the present invention, the screws are tightened to the point where their upper surfaces are at or slightly below the level of the recessed areas so that the locking elements, when pivoted to the locking position, will prevent the screws from backing out but not exert an inward force thereon. The bone screws for the holes adjacent the locking elements are inserted and attached when the locking element 30 or 55 is in the open position as shown at the top of
Although the invention has been described in considerable detail with respect to preferred embodiments, it will be apparent that the invention is capable of numerous modifications and variations, apparent to those skilled in the art, without departing from the spirit and scope of the invention.
Claims
1-20. (canceled)
21. An anterior cervical plate for engaging at least two vertebrae along the anterior cervical spine, comprising:
- a lower surface adapted to engage the anterior of at least two cervical vertebrae and an opposite upper surface;
- at least one receiving area formed in the upper surface and including two transversely aligned screw holes, and
- a locking element pivotally mounted on the receiving area and being movable to a first position in which the locking element completely uncovers the screw holes and a second position in which portions of the elongated locking element extend over a portion of each screw hole to prevent the bone screws located therein from backing out; and
- at least one projection on the receiving area and at least one matching recess on the bottom of the locking element, wherein the projection will snap into place in the recess when the locking element is in said second position.
22. The cervical plate of claim 21, wherein the locking element has a pair of recessed ramps on the bottom thereof to ride up over the projections and permit the projections to snap into place in the recesses.
23. The cervical plate of claim 21 further comprising:
- a tool receiving opening in the locking element for receiving a tool to turn the locking element between the first and second positions.
24. The cervical plate of claim 21, wherein the receiving area is recessed relative to a remainder of the upper surface and extends substantially the width of the upper surface.
25. A spinal fixation assembly comprising:
- an anterior cervical plate for engaging at least two vertebrae along the anterior cervical spine;
- a lower surface of the plate adapted to engage the anterior of at least two cervical vertebrae and an opposite upper surface of the plate;
- at least two transversely aligned screw holes extending between the upper and lower surfaces;
- at least two bone screws each having a head and extending through and seated in one of the screw holes; and
- a locking element pivotally coupled to the upper surface of the plate and being movable to a first position in which the locking element completely uncovers the screw holes and a second position in which portions of the locking element extend over a portion of each screw hole to prevent the bone screws located therein from backing out;
- wherein the locking element is spaced from the heads of bone screws when the locking element is in the second position and the heads are seated in the screw holes.
26. The assembly of claim 25 further comprising:
- a positive positioning structure at an interface between the plate and the locking element, which holds the locking element in the second position.
27. The assembly of claim 25 further comprising:
- a pivot hole in one of the plate and the locking element; and
- a post extending through the pivot hole to pivotally couple the plate and locking element together.
28. An anterior cervical plate for engaging at least two vertebrae along the anterior cervical spine, comprising:
- a plate having a lower surface adapted to engage the anterior of at least two cervical vertebrae and an opposite upper surface;
- at least one pair of spaced apart screw holes through the plate;
- a locking element pivotally mounted between the screw holes and movable between a first position in which the locking element completely uncovers the screw holes and a second position in which the locking element extends over a portion of each screw hole to prevent the bone screws located therein from backing out; and
- a positive positioning structure at an interface between the plate and the locking element that holds the locking element in the second position.
29. The cervical plate of claim 28, wherein the positive positioning structure further comprises:
- a projection on one of the plate and the locking element; and
- a matching recess on the other of the plate and the locking element, the projection and the matching recess being positioned so as to hold the locking element in said second position.
30. The cervical plate of claim 29, wherein the projection is on the plate and the matching recess is on the bottom of the locking element.
31. The cervical plate of claim 30, wherein the bottom of the locking element has a recessed ramp to ride up over the projection to permit the projection to snap into the matching recess when the locking element is in the second position.
32. The cervical plate of claim 31 further comprising:
- a pair of projections on the plate and a pair of matching recesses on the bottom of the locking element.
Type: Application
Filed: Aug 3, 2007
Publication Date: Jan 24, 2008
Applicant: ZIMMER SPINE, INC. (Minneapolis, MN)
Inventor: Thomas Ross (Austin, TX)
Application Number: 11/833,536
International Classification: A61B 17/70 (20060101);