This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to the use of engineered disc tissues and endplate materials in conjunction with such treatment.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of each disc is the nucleus pulposus which, in the adult human, is composed of cells and an insoluble extracellular matrix which is produced by the nucleus itself. The extracellular matrix is composed of collagen, proteoglycans, water, and noncollagenous proteins.
The cells of the nucleus pulposus have chondrocyte-like features. Blood vessels do not course into the nucleus pulposus. Rather, the cells of the nucleus pulposus of the adult human obtain nutrients and eliminate waste by diffusion through blood vessels in the endplates of the vertebrae adjacent to the disc.
The nucleus pulposus is surrounded by the annulus fibrosis, which is composed of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus.
To date, the treatment of degenerative disc disease has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, most prior-art techniques use synthetic materials to replace the entire disc or a portion thereof. My pending U.S. patent application Ser. No. 09/415,382 discloses disc replacement methods and apparatus using synthetic materials.
Prosthetic disc devices replace nucleus pulposus and/or annulus fibrosis function. Nucleus replacing devices rely on the patient""s annulus fibrosis to retain the device and perform annulus functions. Unfortunately, injuries to the annulus often accompany nucleus degeneration or trauma. In addition, the degenerated annulus fibrosis may produce pain in patients with nucleus replacement.
Devices that replace nucleus and annulus functions (total disc replacement) also exhibit certain weaknesses. Total disc replacements rely on attachment of the prosthetic disc to the vertebral endplates. Various methods of attachment have been described including the use of screws, spikes, and porous ingrowth material. The total disc/vertebral interface can loosen. The problems with prosthesis loosening and the revision surgery of the same are well known in prosthetic knee and hip surgery.
The future of treating degenerative disc disease therefore lies in treatments which preserve disc function. If disc function could be restored with biologic replacement or augmentation, the risk of premature wear out would be minimized, if not eliminated.
This invention resides in a method of treating a diseased or traumatized intervertebral disc located between adjacent vertebrae. According to the method, a disc unit is harvested from a recently deceased human or animal donor. As defined herein, this donor disc unit preferably includes not only an intervertebral disc having an extracellular matrix, but also a portion of the vertebrae on either side of the disc, including the endplates.
An affected disc is surgically removing from a patient, including the vertebral endplates and a portion of the vertebra on either side of the disc, thereby creating a void to be filled, and the donor disc unit is positioned within the surgically created void. The spine may be temporarily locally immobilized following placement of the donor disc unit into the surgically created void.
In the preferred embodiment, the donor disc unit is processed to kills living cells therewithin, while preserve the extracellular matrix. Nucleus pulposus and/or annulus fibrosis cells are harvested from a healthy intervertebral disc, cultured and transplanted into the donor disc unit. Precursors, or cells which differentiate into cells which provide nucleus pulposus and/or annulus fibrosis cell function may alternatively be used. The harvested cells are preferably kept viable until placed into the disc unit.
The method of the invention may further include the step of adding one or more therapeutic substances to the donor disc unit, the transplanted cells, or both prior to transplantation. Such therapeutic substances could include culture media, growth factors, differentiation factors, hydrogels, polymers, antibiotics, anti-inflammatory medications, immunosuppressive medications, or any useful combination thereof.