Spinal implants and methods of providing dynamic stability to the spine

Abstract

The present application discloses a plurality of spinal implants and methods for repairing annular defects in intervertebral discs and for providing dynamic stability to the motion segment of the spine in the vicinity of the repaired disc. Each of the implants comprises a head portion and a tail portion. In the illustrated embodiments, the head portion of each implant is enlarged relative to the tail portion. Each of the head portions and tail portions is adapted to support adjacent vertebrae and resist collapse of the intervertebral disc. A tapered portion of each implant engages end plates of the adjacent vertebrae to resist forces tending to push the implant out of the intervertebral space. The tail portion of each implant includes a tail flange (which in some embodiments is of similar diameter to the head portion) that abuts extradiscal lips of the adjacent vertebrae and resists forces tending to push the implant deeper into the intervertebral space.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to provisional application Ser. No. 60 / 711,714, filed on Aug. 26, 2005, the entire contents of which are hereby expressly incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to devices and methods for repairing annular defects in intervertebral discs and for providing dynamic stability to the motion segment of the spine in the vicinity of the repaired disc. [0004] 2. Description of the Related Art [0005] The vertebral spine is the axis of the skeleton upon which all of the body parts “hang.” In humans, the normal spine has seven cervical, twelve thoracic and five lumbar segments. The lumbar segments sit upon a sacrum, which then attaches to a pelvis, in turn supported by hip and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which act as joints, but allow known degrees of flexion, extension, l...

AI Technical Summary

Benefits of technology

[0015] The preferred embodiments of the present spinal implants and methods of providing dynamic stability to the spine have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of these spinal implants and methods as expressed by the claims that follow, their more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description of the Preferred Embodiments,” one will understand how the features of the preferred embodiments provide advantages, which include, inter alia, the capability to repair annular defects and stabilize adjacent motion segments of the spine without substantially diminishing the range of motion of the spine, simplicity of structure and implantation, and a low likelihood that the implant will migrate from the implantation site.

[0016] One embodiment of the present spinal implants and methods of providing dynamic stability to the spine comprises a spinal implant adapted to be implanted in an intervertebral disc located between a first vertebral disc and a second vertebral disc to repair an annular defect in the intervertebral disc, and to provide dynamic stability to a motion segment of a spine in the vicinity of the intervertebral disc. The implant comprises a head portion including at least a first head segment and a second head segment. Each of the first and second head segments has a length greater than zero as measured along a longitudinal axis of the implant. The first head segment has a constant height along its length. The second head segment tapers along at least a portion of its length from a greater height to a lesser height away from the first head segment. The implant further comprises a tail portion extending from the head portion and including at least a first tail segment and a second tail segment. The first tail segment adjoins the second head segment. Each of the first and second tail segments has a length greater than zero as measured along a longitudinal axis of the implant. The first tail segment has a constant height along its length. The second tail segment tapers along at least a portion of its length from a lesser height to a greater height away from the first tail segment.

[0017] Another embodiment of the present spinal implants and methods comprises a spinal implant adapted to be implanted in an intervertebral disc located between a first vertebral disc and a second vertebral disc to repair an annular defect in the intervertebral disc, and to provide dynamic stability to a motion segment of a spine in the vicinity of the intervertebral disc. The implant comprises a head portion including at least a first head segment and a second head segment. Each of the first and second head segments has a length greater than zero as measured along a longitudinal axis of the implant. The first head segment tapers along at least a portion of its length from a greater height to a lesser height away from the second head segment. The second head segment tapers along at least a portion of its length from a greater height to a lesser height away from the first head segment. The implant further comprises a tail portion extending from the head portion and including at least a first tail segment and a second tail segment. The first tail segment adjoins the second head segment. Each of the first and second tail segments has a length greater than zero as measured along a longitudinal axis of the implant. The first tail segment has a constant height along its length. The second tail segment tapers along at least a portion of its length from a lesser height to a greater height away from the first tail segment.

[0018] Another embodiment of the present spinal implants and methods comprises a method of repairing an annular defect in an intervertebral disc located between a first vertebral disc and a second vertebral disc, and providing dynamic stability to a motion segment of a spine in the vicinity of the intervertebral disc. The method comprises the steps of removing at least a portion of the intervertebral disc, preparing an implantation site in the vicinity of the intervertebral disc, and implanting a spinal implant device at the implantation site. The step of preparing the implantation site includes the steps of reaming the implantation site to remove bone material from endplates of each of the first and second vertebral discs and thereby shape a portion of each of the endplates to receive the implant device in a substantially complementary fit, and countersinking the implantation site to remove bone material from extradiscal lips of each of the first and second vertebral discs and thereby shape a portion of each of the extradiscal lips to receive the implant device in a substantially complementary fit.

[0019] Another embodiment of the present spinal implants and methods comprises a method of repairing an annular defect in an intervertebral disc located between a first vertebral disc and a second vertebral disc, and providing dynamic stability to a motion segment of a spine in the vicinity of the intervertebral disc. The method comprises the steps of removing at least a portion of the intervertebral disc, preparing an implantation site in the vicinity of the intervertebral disc, and implanting a spinal implant device at the implantation site. The implant comprises a head portion including at least a first head segment and a second head segment. Each of the first and second head segments has a length greater than zero as measured along a longitudinal axis of the implant. The first head segment has a constant height along its length. The second head segment tapers along at least a portion of its length from a greater height to a lesser height away from the first head segment. A tail portion extends from the head portion and includes at least a first tail segment and a second tail segment. The first tail segment adjoins the second head segment. Each of the first and second tail segments has a length greater than zero as measured along a longitudinal axis of the implant. The first tail segment has a constant height along its length. The second tail segment tapers along at least a portion of its length from a lesser height to a greater height away from the first tail segment.

Problems solved by technology

These spinal implants and methods are, however, susceptible to modifications and alternate constructions from that discussed above that are fully equivalent.

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