Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2001-07-06
2004-10-26
Robert, Eduardo C. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06808537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an improved 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. In particular, the invention relates to a spinal fusion implant that is selectively directionally expandable and which specifically has 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 an implant having portions of upper and lower members that have a first, collapsed position relative to one another during insertion and a second, expanded position relative to one another allowing for an increased height. Further, the invention relates to cooperatively configured interlocking side walls of the upper and lower members that are adapted to hold the implant in an expanded position when moved from the collapsed position.
2. Description of the Related Art
Threaded and push-in spinal fusion implants having upper and lower portions adapted for placement in contact with adjacent vertebral bodies are known in the related art. The first artificial threaded spinal fusion implant was invented by Michelson and is disclosed in U.S. Pat. No. 5,015,247, filed Jun. 13, 1988, which is hereby incorporated by reference. Various push-in spinal fusion implants have been invented by Michelson and are disclosed in U.S. Pat. No. 5,593,409, filed Feb. 17, 1995 and U.S. Pat. No. 5,776,199, filed Jun. 28, 1988, which are hereby incorporated by reference.
Lordotic, frusto-conical, or tapered, threaded and 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. 08/480,904 and EP 96917996.9, and U.S. Pat. No. 5,609,635, filed Jun. 7, 1995, which are 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, previously incorporated by reference herein.
Lordotic, frusto-conical, or tapered, spinal fusion implants have the advantage of restoring or enhancing spinal lordosis. Threaded and 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 artificial interbody spinal fusion implant for insertion across a disc space between two adjacent vertebral bodies of a human spine. The implant of the present invention includes an upper member having a portion adapted for placement toward and into contact with or at least in part within one of the adjacent vertebral bodies and a lower member having a portion adapted for placement toward and into contact with or at least in part within the other of the adjacent vertebral bodies. The 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 portions of the upper and lower members in the first position of the present invention may be parallel or angled to one another. Preferably, at least a portion of a bone-engaging projection, such as a helical thread, ratchet, or knurling, is on the exterior of each of the opposed portions of the upper and lower members 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 cooperatively configured interlocking side wall of the upper and lower members is adapted to hold 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 preferably passing through the mid-longitudinal axis of the implant and the upper and lower members.
Each of the upper and lower members of at least one embodiment of the present invention have side walls adapted to cooperatively engage one another along at least a portion of the length of the side walls to hold 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 when the implant is in a final deployed position. Preferably the side walls of at least one, and if desired both, of the upper and lower members flex when the implant is moved from the first position to the second position. In particular, when the implant is moved from the first position to the second position certain of the side walls may spring from a position closer to the mid-longitudinal axis of the implant to a position further away from the mid-longitudinal axis or may spring from a position further from the mid-longitudinal axis of the implant to a position closer to the mid-longitudinal axis. This movement of at least one of the side walls may include rotating at least a portion of the side wall along an arc around an axis that is parallel to the mid-longitudinal axis of the implant when the implant is moved from the first position to the second position. These rotational, flexing, or springing forces acting to engage the cooperatively configured side walls of the upper and lower members together add lateral stability to the implant while maintaining the increased height of the implant.
Preferably, the side walls of the upper and lower members have cooperatively engaging stepped surfaces. Preferred stepped surfaces of one embodiment of the present invention include interdigitating projections and detents. The side walls having detents preferably have more detents than the cooperatively engaging side walls having projections have projections to permit the implant to move from the first position to the second position. During movement of the implant from the first position to the second position the side walls having detents in one embodiment have at least one detent that narrows during movement of the side wall having detents. This movement moves the side wall having detents into alignment and engagement with the projections of the wall having projections to increase the height of the implant. One particular preferred embodiment of the present invention includes side walls with two projections adapted to cooperatively engage side walls with
Martin & Ferraro LLP
Robert Eduardo C.
LandOfFree
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