Patent Application
20100324680
The present invention relates to the surgical treatment of intervertebral discs in the spine that have suffered from tears in the annulus fibrosis, herniation of the nucleus pulposus and/or significant disc height loss.
The main functions of the spine are to allow motion, transmit load and protect the neural elements. The vertebrae of the spine articulate with each other to allow motion in the frontal, sagittal, and transverse planes. The intervertebral disc is a major link between the adjacent vertebrae of the spine.
The intervertebral discs make up about 20-33% of the lumbar spine length and perform the important role of absorbing mechanical loads while allowing for constrained flexibility of the spine. The disc is composed of a soft, central nucleus pulposus surrounded by a tough, woven annulus fibrosis.
The nucleus pulposus is primarily composed of mucoid material containing mainly proteoglycans with a small amount of collagen and can be characterized as a loose hydrogel. The annulus fibrosus consists of fibrocartilaginous tissue and fibrous protein. The collagen fibers are arranged in layers to form concentric rings around the nucleus pulposus. The layers of collagen fibers are arranged in a generally crisscross fashion which allows the annulus fibrosus to withstand torsional and bending loads.
Repeated loading on the intervertebral discs from spinal movement can initiate circumferential tears in the annulus fibrosus of an intervertebral disc, which gradually form radial tears into the nucleus pulposus resulting in the herniation of the nucleus pulposus and/or significant disc height loss. In addition, excessive loading on the intervertebral disc from spinal trauma can also cause tears in the annulus fibrosis resulting in the herniation of the nucleus pulposus and/or significant disc height loss. Herniation of the nucleus pulposus and/or significant disc height loss reduces the disc's ability to resist compressive loads and can also result in excessive motion in the spine such as excessive extension or flexion, resulting in spine segmental instability. The spine is, thus, more vulnerable to trauma and disease such as stenosis of the intervertebral foramen, nerve root compression, and further disc herniation or disc re-herniation.
As such, there exists a need for an intradiscal member capable of being installed inside an intervertebral disc that provides support to the intervertebral disc that has a compromised annulus fibrosis to preclude tearing or, in the case of an existing tear, preclude further tearing of the annulus fibrosis to prevent the herniation or re-herniation of the nucleus pulposus and/or limit further disc height loss.
In an exemplary embodiment, the present invention provides a resilient support member capable of being installed inside an intervertebral disc to provide support to an intervertebral disc that has a compromised annulus fibrosis. In one embodiment, the intradiscal member includes an upper support surface, a lower support surface, and an outer wall. In another embodiment, the intradiscal member includes an inner wall defining a volume. In yet another embodiment, the intradiscal member includes a fastening element. The present invention also provides a method for installing the intradiscal member in the nucleus pulposus region of an intervertebral disc.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred or exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
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In another embodiment of the intradiscal member 10, an inner wall 18 can also be included. In this embodiment, the member 10 has an upper support surface 12, a lower support surface 14, an outer wall 16, and an inner wall 18, the inner wall defining an interior 20. In this embodiment, the intradiscal member 10 can be comprised of several materials. For example, outer surfaces as well as the inner wall 18 of the member 10 can be primarily comprised of a polyeurathane jacket while the interior 20 of the member 10 can be filled with silicon. Instead of silicone, the interior 20 of member 10 can be filled with any known biocompatible, resilient and compressible member such as a hydrogel material. Alternatively, the interior 20 can remain empty and serve as an air filled support member.
In another embodiment of the intradiscal member 10, a fastening element 22 is included. In this embodiment, the member 10 has an upper support surface 12, a lower support surface 14, an outer wall 16, and a fastening element 22 extending from the lower support surface 14. The fastening element 22 is configured and dimensioned to serve as an anchor, anchoring the intradiscal member 10 to a predetermined position in the intervertebral disc. Although the fastening element 22 is shown as a shaft having threading extending along at least a portion thereon, any element capable of fastening the member 10 in a predetermined position is contemplated, including a non-threaded interference fit type shaft, a shaft including a plurality of gripping or puncturing elements, or a bonding agent such as glue.
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The intradiscal member 10 can be installed in the intervertebral disc 1 (specifically in the nucleus pulposus 5) via a channel or bore 26 drilled or cut into the vertebral body 3 (or into the vertebral body 2) in the direction of the endplate that is adjacent to the intervertebral disc that is to be treated. The channel 26 preferably extends through the endplate (not shown) of the intervertebral body 3 and into the intervertebral disc 1. The channel 26 is oriented such that the channel 26, when entering the intervertebral disc 1 through the annulus fibrosis 4, will be at or near the predetermined position of installation of the intradiscal member 10 in the nucleus pulposus 5 of the intervertebral disc 1. Alternatively, the channel 26 can be oriented such that the predetermined position of installation is not immediately near the point of entry into the nucleus pulposus 5 but is along the path or trajectory of channel 26 and the predetermined position of installation is further within the nucleus pulposus 5 of the intervertebral disc 1. It is important to note that although the channel 26 is cutting through the annulus fibrosis 4 of the intervertebral disc, it is doing so through the endplate of the vertebral body 3. By cutting through this portion of the annulus fibrosis 4, the intervertebral disc 1 won't be further compromised as the endplate of the vertebral body serves as a natural buttress or barrier. Although the entry or initial opening of the channel 26 can be located anywhere on the intervertebral body 3, in one embodiment, the entry or initial opening of the channel 26 is located centrally on the intervertebral body 3 to prevent compromising the vertebral body 3. Depending on the number of intradiscal members 10 to be implanted and the location of implantation in the nucleus pulposus 5 of the intervertebral disc 1, addition channels can be created, where each channel begins at the same entry initial opening on the vertebral body 3 as the original channel 26 and ends within the nucleus pulposus 5 of the intervertebral body 1 at the desired location for implantation.
Although the channel 26 is shown as being created through the anterior portion of the vertebral body 3 (or vertebral body 2), it is also contemplated that the channel 26 can be created through any portion of the vertebral body 2, 3 including the posterior or lateral portions of the vertebral body 2, 3. For example, it is contemplated that the channel 26 can be created through the pedicle of the vertebral body 2, 3 in the direction of the endplate that is adjacent to the intervertebral disc that is to be treated.
Once the channel 26 is prepared, the intradiscal member 10 can be introduced into the nucleus pulposus 5 of the intervertebral disc 1. The channel 26 is configured and dimensioned so that the intradiscal member 10 can be received through the channel 26 with no change in dimension or a minor change in dimension. In other words, if the channel 26 is configured and dimensions such that the channel 26 is smaller in diameter than the intradiscal member 10, the intradiscal member 10 will compress slightly as it is passed through the channel 26.
The intradiscal member 10 is introduced into the intervertebral disc 1 (specifically into the nucleus pulposus 5 of the disc 1) through the channel 26 with the aid of an installation instrument 28. In one embodiment, the installation instrument 28 will contact and engage the intradiscal member 10 at its distal end. The instrument 28 can then be manipulated to guide the intradiscal member 10 through the channel 26, through the annulus fibrosis 4, into the nucleus pulposus 5 of intervertebral disc 1. Once the intradiscal member 10 is in the desired installation position, the instrument 28 is then disengaged from the intradiscal member 10 and is removed from the intervertebral disc 1 and the channel 26. At this point, if there are additional intradiscal members to be installed, the process is repeated.
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The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
