Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2001-01-29
2004-03-23
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C123S019000
Reexamination Certificate
active
06709458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an improved push-in interbody (for placement at least in part between adjacent vertebral bodies) spinal fusion implant for the immobilization of vertebrae. The present invention is directed to push-in implants only and not to threaded implants. In particular, the invention relates to a push-in spinal fusion implant that is selectively directionally expandable and which specifically has height raising capabilities that are utilized once the implant is initially positioned. More particularly, the invention relates to a push-in implant having arcuate portions of upper and lower members that in a first, collapsed, or insertion position are angled to one another and form at least a portion of a frusto-conical shape, or of a cylinder split along a horizontal plane through its mid-longitudinal axis wedging the upper half from the lower half by an inclined plane, along a substantial portion of the length of the implant.
2. Description of the Related Art
Push-in spinal fusion implants having upper and lower arcuate portions adapted for placement in contact with adjacent vertebral bodies are known in the related art. Such a push-in spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,593,409, filed Feb. 17, 1995, which is hereby incorporated by reference.
Lordotic, frusto-conical, or tapered, push-in spinal fusion implants are also known in the art. By way of example, Michelson has invented such implants as disclosed in U.S. application Ser. No. 08/484,928, filed Jun. 7, 1995, which is hereby incorporated by reference.
Expandable fusion implants are known in the related art. The first expandable spinal fusion (allowing for the growth of bone from vertebral body to vertebral body through the implant) implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,776,199, filed Jun. 28, 1988, which is hereby incorporated by reference.
Lordotic, frusto-conical, or tapered, spinal fusion implants have the advantage of restoring or enhancing spinal lordosis. Push-in spinal fusion implants offer the advantage of being easily positioned in the implantation space and of having excellent fastening or holding features. Expandable fusion implants offer the advantage of allowing for the placement of a potentially larger implant through a smaller opening in a patient's body. Selective expansion along a single direction, (e.g. vertically only when correctly installed) offers the advantage of increasing the height of the implant and therefore the distraction of the disc space, but without a concomitant increase in the width of the implant.
There exists a need for an artificial interbody spinal fusion implant providing for all of the aforementioned advantages in combination.
SUMMARY OF THE INVENTION
In accordance with the present invention, as embodied and broadly described herein, there is provided an expandable push-in artificial interbody spinal fusion implant, having a shape that is generally frusto-conical or generally that of a cylinder split along a horizontal plane through its mid-longitudinal axis wedging the upper half from the lower half by an inclined plane when inserted, for insertion across a disc space between two adjacent vertebral bodies of a human spine. The push-in implant of the present invention includes an upper member having an arcuate portion adapted for placement toward and at least in part within one of the adjacent vertebral bodies and a lower member having an arcuate portion adapted for placement toward and at least in part within the other of the adjacent vertebral bodies. The arcuate portions of the upper and lower members have at least one opening in communication with one another for permitting for the growth of bone from a vertebral body to an adjacent vertebral body through the implant. The upper and lower members are articulated therebetween, preferably proximate one of the proximal ends and the distal ends of the upper and lower members and preferably allow for divergence between the articulating members at the end opposite the articulating end of the implant. The upper and lower members have a first position relative to one another that allows for a collapsed implant height and a second position relative to one another that allows for an increased height. The arcuate portions of the upper and lower members in the first position of the present invention are angled to one another and form at least a portion of a frusto-conical shape, or of a cylinder split along a horizontal plane through its mid-longitudinal axis wedging the upper half from the lower half by an inclined plane, along the length of the implant. On the exterior of each of the opposed arcuate portions of the upper and lower members is at least one bone-engaging projection adapted for linear insertion for engaging the adjacent vertebral bodies. The upper and lower members have a leading or distal end, an opposite trailing or proximal end, and a length therebetween. A blocker that is preferably in the form of an expander is located proximate at least one of the ends for holding at least a portion of the upper and lower members apart so as to maintain the increased height of the implant and resist the collapse of the implant to the collapsed implant height. Expansion of the implant preferably increases the implant height only, that is in a plane passing through the mid-longitudinal axis of the implant and the upper and lower members.
The blocker need not be in contact with the upper and lower members when the implant is initially inserted into the implantation space. The blocker may be a block or any type of spacer that is inserted between or otherwise holds apart the articulated upper and lower members after the implant is positioned so as to hold portions of the upper and lower members spaced apart the optimal height and angulation relative to one another. That is, the implant may be expanded with an extrinsic tool and then the expanded portions held apart in the second position by a third body blocker or blockers placed therebetween. Further, a physician may be able to select from a series of blockers having different heights usable with the same implant. The present invention includes expanding the implant with a tool, such as a spreader or a distractor, but is not limited to a scissors type, a rack and gear type, a threaded member type or any other type of particular external expander tool mechanism. Each tool nevertheless preferably engages the upper and the lower implant members to urge the implant apart. Then the blocker may be inserted into contact with the upper and lower members to maintain the implant at an expanded height. The height of the gap created by expanding the implant may be measured so that the appropriately sized blocker or expander may be inserted into contact with the upper and lower members depending upon the amount of distraction of the implant desired by the physician.
In a preferred embodiment, the blocker is in contact with the upper and lower members prior to the implant expansion, and the blocker is itself the expander, which may be operated by an extrinsic tool. By way of example only, the expander may rotate: to increase the height of the implant; in a single direction; more than 40 degrees and less than 140 degrees and more preferably approximately 90 degrees to move from a first insertion position to a second/deployed position; and in a plane perpendicular to the longitudinal axis of the implant to increase the height of the implant. The expander preferably remains in the same perpendicular plane relative to the longitudinal axis of the implant when rotated. In another embodiment the expander may be a member, such as a plate, a rod, or of any other configuration suitable for the intended purpose initially within the interior between the upper and lower members in a collapsed position that is erected to a more erect position when the implant is in the expanded position. The expander can be hollow or solid.
In a preferred embodiment,
Barrett Thomas
Martin & Ferraro LLP
McDermott Corrine
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