US 20050124994 A1
An occipitocervical fixation system includes a plate for securing to the occiput and at least one pre-bent rod. The plate includes holes for receiving bone fasteners, and at least one clamping assembly for retaining a portion of a rod. The clamping assembly is selectively pivotable and lockable in place to fix the position of the rod.
1. An occipital plate assembly comprising: a bone contacting surface, an outer surface, an upper end, a lower end, and at least one hole extending from the bone contacting surface to the outer surface for receiving a bone screw, wherein the plate further includes at least one rod clamping portion on the lower end, the rod clamping portion having a rod-receiving recess with an opening for receiving a spinal rod, the opening being generally directed upwards when the plate is affixed to a patient's occiput.
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16. An occipital plate assembly comprising:
a plate having a central portion and a pair of supporting arms extending therefrom, the central portion including a plurality of holes extending from a bone contacting surface to an outer surface for receiving a plurality of bones screws to secure the plate to a patient's occiput; and
at least one pre-bent spinal rod wherein the rod has a first section, a second section, and an intermediate section disposed therebetween, the first and second sections being disposed substantially perpendicular with respect to one another;
wherein each of the supporting arms includes a rod-receiving recess for engaging one of the sections of the pre-bent rod.
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This application is a continuation of and claims priority to U.S. patent application Ser. No. 09/788,639, filed Feb. 21, 2001, which is expressly incorporated by reference herein in its entirety.
The present invention is related to a system for stabilizing the spine. More particularly, the present invention is related to an occipitocervical fixation system that is mounted to both the occiput and spine.
Occipitocervical fixation has been achieved using a variety of techniques which generally provide stabilization of the base of the skull with respect to the neck. In order to promote fusion, for example, bone struts formed of autogenous ribs or curved iliac crest struts have been fixed to the occiput and spinous processes, cervical laminae, or facets. Wires are used to fix the struts in place until bone fusion occurs. The thickness of the occiput varies, however, and thus the occiput is typically wired in regions of greater thickness such as near the foramen magnum, at the nuchal line, and along the midline crest. Holes are drilled in the occiput to receive the wires that are also fed through holes in the struts. Although bone fusion occurs with this technique, the struts may be weak prior to fusion, and additional orthosis is applied such as with a halo vest or other hard collar until the struts can provide acceptably strong immobilization. Alternatively, metal struts may be used.
Other techniques for occipitocervical fixation involve the use of other metal implants. One metal implant is a stainless steel, U-shaped device known as a Steinman pin. The threaded pin is bent to match the contour of the occipitocervical region, and fixed to the occiput and cervical laminae or facets using wires. The pin is generally symmetrically disposed about the spine, with the sides of the “U” creating a central region in which a bone graft can be disposed and further wired to the pin. When attached to the occiput and spine, the pin assumes an inverted-U configuration. Several holes are formed in the occiput so that the U-bend may be fixed in place.
Additional metal implants include grooved or roughened titanium rods, smooth steel rods in the form of a Hartshill rectangle or Ransford loop, a Cotrel-Dubousset rod screw plate, and titanium frames have been employed.
Despite these developments, there exists a need for an occipital plate and system for spinal stabilization in which the plate and rod components are separated to permit greater flexibility in installation by the surgeon. In particular, because a traditional unitary plate and rod system is bent in two planes in order to properly adjust it with respect to the occiput, such a unitary design presents difficulties in achieving the desired fit.
The present invention is related to an occipital plate that includes a Y-shaped plate portion having a front side and a back side, a central portion, two leg portions, and a plurality of bone screw holes in the central portion, the holes being configured and dimensioned to receive a bushing. The occipital plate also includes at least one clamping portion disposed on the front side proximate a free end of at least one of the leg portions, and the plate is bendable to conform to the an occiput. In one embodiment, the central portion includes an upper portion, a lower portion, and a grooved portion therebetween, the upper portion having one bone screw hole. The grooved portion is flexible to permit the upper portion to be disposed at an angle with respect to the lower portion. The leg portions and at least a portion of the central portion are disposed in nonparallel planes, and the planes may intersect at an angle of between about 160° and about 175°, and in one embodiment the planes intersect at an angle of about 170°.
The clamping portion may include a pivot member and a clamp plate, the clamp plate being pivotable about the pivot member. The clamp plate may further include a hole, the pivot member being received in the hole. The pivot member also may include a tapered portion with serrations, and the leg portion may further include a tapered hole with serrations, with the serrations of the tapered portion positively engaging the serrations of the tapered hole. The diameter of the tapered hole increases from the back side to the front side, and the clamp plate is secured to the pivot member with a fastener. The leg portion additionally includes a rod-receiving first recess and the clamping plate additionally includes a rod-receiving second recess, with the first and second recesses generally opposing each other and the second recess being serrated. The bone screw holes in the lower portion may be disposed in a rectangular array, and at least one group of bone screw holes in the array may be disposed along a central axis of the plate extending between the leg portions. The bone screw hole in the upper portion may be disposed on the central axis, and at least two bone screw holes may be disposed coaxially. In one embodiment, the bushings permit polyaxial angulation, the plate is bendable along at least two generally parallel axes and/or at least two generally perpendicular axes.
The present invention is also related to an occipitocervical fixation system including an occipital plate having at least one rod clamp portion and a plate portion with at least one hole for receiving a bone screw, the rod clamp portion having a post, a clamp plate with a hole for receiving the post, and a fastener for tightening the clamp to the post. The system also includes at least one bone screw and at least one rod, with the rod being retained between the plate portion and the clamp plate and being pivotable about the post.
Furthermore, the present invention is related to a pre-bent rod for attachment to an occipital plate including a straight section, a bent section, and a serrated clamping section, with the straight section and the serrated clamping section being disposed substantially perpendicular to each other, and the serrated clamping section and the bent section being disposed at an angle of about 45° with respect to each other. In one embodiment, the serrated clamping section is generally cylindrical and includes circumferential serrations about an angular range of between about 90° and 180°.
Preferred features of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and wherein:
Referring initially to
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With reference to
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Bushing 20 includes slots 128 located on sidewall 120. Slots 128 allow sidewall 120 to expand outwardly against through hole 18. This outward expansion locks bushing 20 at the selected orientation relative to the axis of through hole 18. In order to enhance the locking effect upon expansion, exterior surface 122 of sidewall 120 and/or the periphery of through holes 18 can be provided with ridges 130. Ridges 130 provide an additional mechanism to resist motion of bushing 20 relative to occipital plate 10 once sidewall 120 has expanded outwardly. Although bushing 20 is shown having four slots, any number of slots, including one, can be used as long as the chosen number of slots provides for outward expansion of sidewall 120. Slot 128 a extends from upper surface 116 through lower surface 118 while the rest of slots 128 do not extend through to lower surface 118. Slots 128 all extend from upper surface 116 of bushing 20.
In the preferred embodiment, pre-bent rods suitable for use with the present invention are shown in
The pair of rods used with occipital plate 10 are typically mirror images of each other. For example, a rod 140 would be used with right clamp assembly 26 while a mirror image of rod 140, as shown in
Pre-bent rods 140, 160 are shown retained in clamp assemblies 24, 26, respectively, in
Alternate embodiments of occipital plates are shown in
Additional embodiments of occipital plates are shown in
In some preferred embodiments of the present invention, cylindrical rods with a diameter of 3.5 mm are used as the spinal rods or pre-bent rods. In alternate embodiments, straight rods may be used and oriented accordingly by a surgeon using a rod bender.
In the occipital plate designs disclosed herein, screw holes have been positioned along the midline of the plate for use at the midline of the occiput, since the bone thickness there is greater than on the sides. In some embodiments, the screw holes may be angled about 12° to facilitate access to the screws with a screwdriver, and to enhance pull-out strength of the screws due to the wedge effect. Although expansion head screws are preferred, other non-locking screws may be used. Arc shaped cuts between the clamping assemblies or arrangements of each plate allow the placement of a bone graft. In the preferred embodiment, occipital plate 10 is formed of titanium. Preferably, the shape of the occipital plate facilitates polyaxial bending thereof.
The number of holes provided in an occipital plate of the present invention for receiving bone screws may be varied, as may the pattern of the holes and the relative alignment. Other screw hole shapes such as an oval shape, and other hole sizes may be used, as well as alternative means for locking screws. Bushings may not be included in some embodiments. Alternative fasteners for attaching an occipital plate to bone include staples and wires.
While various descriptions of the present invention are described above, it should be understood that the various features can be used singly or in any combination thereof. Therefore, this invention is not to be limited to only the specifically preferred embodiments depicted herein.
Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. For example, the C-shaped clamping sections of some embodiments of the occipital plate may instead include full-circle regions for receiving rods. In another embodiment, a sleeve for receiving the rods may extend across some or the entire the length of the occipital plate. In yet another embodiment, two smaller occipital plates are provided for securement to the occiput, with each plate having a single clamp assembly and receiving one rod. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly defined as set forth in the appended claims.