Patent Application
20070088439
The present invention relates to spinal implants and, more particularly, to an artificial disc including endplates having cages to promote bone growth to facilitate attaching the endplates to the inferior face of the superior vertebral body and the superior face of the inferior vertebral body.
For a number of years, surgical spinal correction has been tending away from conventional fusion surgical technologies to non-fusion technologies. With fusion technology, a graft is placed between superior and inferior vertebrae. Bone growth is encouraged to fuse the superior vertebrae and the inferior vertebrae. Once fused, the pain is frequently removed or reduced, but fusion is a less than satisfactory solution because of the resulting limitation on the range of motion caused by one or more fusions. Moreover, fusing vertebrae increases the stress on adjacent levels.
Non-fusion technologies, while providing a greater range of motion and the like, have a number of problems also. In some attempts at disc replacement, for example, a flexible artificial disc is placed within the intervertebral disc space. In these systems, the expectation is the disc will remain in place based on endplate fibrous and bone in growth and/or axial loading of the cervical spine. Often, these types of discs fail as they migrate out of the disc space. They also present a potential danger for a stretch injury to the spinal cord due to minimally restrained in extension.
Thus, it would be beneficial to design an artificial disc that provides a better anchor to the vertebral bodies.
The present invention provides an anchor to attach an artificial disc to vertebral bodies. The artificial disc comprises a superior endplate and an inferior endplate. A disc section extends between the endplates. The superior endplate comprises a first wall defining a first cavity, the first cavity to contain material to facilitate fusion of the superior endplate to a superior vertebral body. Similarly, the inferior endplate comprises a second wall defining a second cavity, the second cavity to contain material to facilitate fusion of the superior endplate to a superior vertebral body.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, serve to explain the principles thereof. Like items in the drawings are referred to using the same numerical reference.
Referring to
Disc section 106 comprises an elastic material 112 in the disc portion of disc section 106 designed to facilitate artificial disc 100 mimicking the anatomical disc it is replacing. Elastic material 112 in disc section 106 could be a gel, a resin, a spring, shaped memory material, such as NiTi, or the like. Some artificial discs having elastic materials are described in, for example, U.S. Pat. No. 6,770,094, titled INTERVERTEBRAL DISC PROSTHESIS, issued Aug. 3, 2004, to Fehling et al., incorporated herein by reference as if set out in full, U.S. patent application Ser. No. 10/641,530, titled SHAPED MEMORY ARTIFICIAL DISC AND METHODS OF ENGRAFTING THE SAME, filed Aug. 14, 2004, incorporated herein by reference as if set out in full, and a U.S. Pat. No. 6,881,228, titled ARTIFICIAL DISC IMPLANT, issued Apr. 19, 2005, to Zdeblick et al., incorporated herein by reference as if set out in full. Of course, as one of ordinary skill in the art will recognize on reading the disclosure, reference to the particular types of artificial discs described is provided as exemplary and should not be considered limiting.
Referring now to
Optionally, cavity 204 may have one or more internal wall 208. Internal wall 208 may be arranged to along the long dimension, short dimension, diagonal, or the like of superior endplate 102.
As shown, superior endplate 102 and inferior endplate are rectangular in shape. However, alternative shapes are possible. Other shapes include circular, elliptical, square, other polygon shapes, or random shapes. The shape may be dictated by the anatomy of the spinal to which the artificial disc is going to be implanted.
While a particular design for superior endplate 102 (and inferior endplate 104) has been shown, one of skill in the art will now recognize superior endplate 102 may have a number of similar designs. In particular, superior endplate 102 and inferior endplate 104 may be constructed similar to conventional bone fusion cages, such as, for example, U.S. Pat. No. 6,902,581, titled APPARATUS FOR FUSING ADJACENT BONE STRUCTURE, issued Jun. 7, 2005, to. Walkenhorst, et al., incorporated herein by reference as if set out in full.
Bone growth and fusion of superior endplate 102 with the inferior surface of the superior vertebrae and inferior endplate 104 with the superior surface of the inferior vertebrae facilitates anchoring artificial disc 100. The anchoring should inhibit artificial disc from moving and decrease the failure rates of the associated artificial disc.
While bone growth is desired around endplates 102 and 104, bone growth is not desired about disc section 106. Thus, disc section 106 may comprise cover 110 around the elastic portion. Cover 110 could be made from material that inhibits bone growth. Moreover, a barrier 116 may be placed between superior endplate 102 and disc section 106, and between inferior endplate 104 and disc section 106. Because disc section 106 extends and flexes with the movement of the back, it is unlikely bone would grow or fuse to disc section 106; therefore, having cover 110 and barriers 112 that inhibit bone growth into the disc section 106 is optional.
Referring now to
While the invention has been particularly shown and described with reference to an embodiment thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention.
