Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2002-04-23
2004-04-06
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S017110
Reexamination Certificate
active
06716247
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 in the space previously occupied by disc material) spinal fusion implant for the immobilization of vertebrae. The present invention is directed to expandable push-in implants only not including push-in implants having substantially arcuate upper and lower members oriented toward the adjacent vertebral bodies and designed to engage the vertebral bodies along arcuate cuts therein typically formed by a drill. Further, the present invention is not directed to threaded implants requiring rotation for insertion into the implantation space in the spine. In particular, the invention relates to push-in spinal fusion implants that have height raising capabilities that are utilized once the implant is initially positioned. Such height raising capability may be utilized within the spine anteriorly, posteriorly, or both and to various extents, respectively so as to raise the front, back, or both of the implant by the same or various amounts. More particularly, the invention relates to a push-in implant having upper and lower surfaces of upper and lower members that in a first or insertion position are collapsed relative to one another and in a second or deployed position are adapted to contact the adjacent vertebral bodies.
2. Description of the Related Art
Push-in spinal fusion implants having upper and lower surfaces 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. 5,776,199, filed Jun. 28, 1988, which is hereby incorporated by reference.
Lordotic 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. Pat. No. 5,609,635, 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 also is disclosed in U.S. Pat. No. 5,776,199 previously incorporated by reference herein.
Lordotic 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 with upper and lower surfaces 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 upper surface adapted for placement toward and into contact with one of the adjacent vertebral bodies and a lower member having a lower surface adapted for placement toward and into contact with the other of the adjacent vertebral bodies. The upper and lower surfaces 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 upper and lower surfaces in the first position of the present invention of one embodiment are generally planar to one another.
As used herein the terms “generally or substantially planar” and “non-arcuate” are intended to describe the upper and lower surfaces of the implant of the present invention as having (1) no curvature, as in a planar surface, (2) slight or mild curvature from the leading end to the trailing end of the implant, and/or (3) slight or mild curvature across the implant width. Slight or mild curvature does not include the curvature associated with the upper and lower surfaces of implants for insertion into a disc space having a circular cross section formed across a spinal disc and into the adjacent vertebral bodies. While the upper and lower surfaces of the present invention may have some curvature, in comparison to an implant having a circular cross section, the curvature is minimal. For implants having a circular cross section such as threaded implants the curvature of the upper and lower surfaces contacting the adjacent vertebral bodies is a radius of half the width of the implant. If there is a curvature to the upper and lower surfaces of the present invention, the curvature is that of a circle much greater than the width of the implant; thus, it has a slight curvature that may correspond to an anatomical curvature of a disc or the surface of the vertebral endplate.
The upper and lower surfaces of the upper and lower members may be either generally parallel or angled to one another when the implant is in the initial insertion position. In another embodiment, the upper and lower surfaces may have a relatively mild convexity in at least one or both directions so as to better conform to the anatomical shape of the disc space or the vertebral endplates. While a substantially parallelepiped shape having a quadrilateral cross section may be generally preferred the leading and trailing ends may be substantially rounded to some advantage.
The height of the implant is at least that of the height of the restored disc space into which it is inserted. The implant is inserted at least in part within the space that was previously occupied by the disc material that was contained between the vertebral bodies.
Preferably, on the exterior of each of the upper and lower surfaces 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 preferably 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 po
Barrett Thomas
Martin & Ferraro LLP
McDermott Corrine
LandOfFree
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