Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-06-16
2001-01-30
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S017110
Reexamination Certificate
active
06179875
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the fusing of spinal vertebrae. More particularly this invention concerns an implant for fusing lumbar vertebra and a method of using the implant.
BACKGROUND OF THE INVENTION
When a defective disk has been removed from between two vertebrae it is necessary to provide an implant to maintain a spacing between these vertebrae so that the spine is not unstable in the region of the resected disk and to prevent the two bones from rubbing painfully together. As a rule such implants are generally closed cages whose interiors are only accessible through small apertures in their side walls. Bone chips must be introduced into the interior of such an implant so the two flanking vertebrae will grow and fuse together. This is a fairly difficult job, and necessitates the use of tiny bone fragments that do not grow well and that are quite hard to handle. Furthermore the job of packing the implant can take quite some time due to the smallness of the bone fragments, making the operation fairly long and, hence, even more expensive and dangerous for the patient than is strictly necessary.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved implant for fusing two vertebrae.
Another object is the provision of such an improved implant for fusing two vertebrae which overcomes the above-given disadvantages, that is which is easy to install and which promotes rapid bone growth and fusion.
A further object is the provision of an improved method of stabilizing vertebrae by means of an implant for a spinal fusion.
SUMMARY OF THE INVENTION
An implant for intersomatic fusion of two adjacent vertebrae has according to the invention a web plate and a pair of arms extending from ends of the web plate and imparting a U-shape to the implant. The arms form with the web plate a space.
Such implants are used to stabilize two adjacent vertebrae following resection of a disk between them and distraction of the two vertebrae to form between confronting faces of the vertebrae a gap through which the patient's spinal chord extends. The implants are inserted into the gap from the posterior to each side of the spinal chord and then the spaces defined between the arms are packed with bone chips. Such a procedure is, by comparison with the standard anterior approach, relatively noninvasive and therefore is much less expensive and difficult for the patient.
According to the invention one of the arms of each implant extends substantially at a right angle to the respective web plate and the other of the respective arms extends at an acute angle to the respective web plate and to the respective one arm. The two implants are positioned with their one arms immediately adjacent and generally parallel to each other. Thus the two angled-out arms are on the outside, with the planes of the web plate and arms perpendicular to the faces of the flanking vertebrae for very solid engagement.
The web plate in accordance with the invention is formed with a tool-receiving hole and the implants are inserted by being mounted at the hole onto a tool and pushed by the tool into the space. The hole is threaded and the tool has a threaded end.
The bone chips according to the invention are obtained autologously from the patient, typically from the pelvis. Normally in accordance with the invention the arms have free ends formed with inwardly directed holding formations and the chips include a bone plate fixed crosswise between the arms at the formations. The arms are formed with throughgoing holes so that bone can grow through the holes. More bone chips are normally packed around the implant, to fuse through the holes with the chips in the spaces.
The edges of the arms according to the invention are formed with angled barbs that are directed away from the web plate. Thus they can be pushed into place, but will lock there and not move once whatever is used to distract the vertebrae is released.
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patent: 5192327 (1993-03-01), Brantigan
patent: 5397364 (1995-03-01), Kozak et al.
patent: 5522899 (1996-06-01), Michelson
patent: 5609635 (1997-03-01), Michelson
patent: 5716415 (1998-02-01), Steffee
patent: 5766252 (1998-06-01), Henry et al.
patent: 5776199 (1998-07-01), Michelson
patent: 5888227 (1999-03-01), Cottle
Dubno Herbert
Smith Jeffrey A.
Ulrich GmbH & Co. KG
Wilford Andrew
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