Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-03-20
2001-05-01
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06224631
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to procedures for intervertebral stabilization. Specifically, the disclosure provides implants, instrumentation and methods to facilitate stabilization or fusion between two vertebrae.
BACKGROUND OF THE INVENTION
Chronic back problems cause pain and disability for a large segment of the population. Frequently, the cause of back pain is traceable to diseased disk material between opposing vertebrae. When the disk material is diseased, the opposing vertebrae may be inadequately supported, resulting in persistent pain.
Surgical techniques have been developed to remove the diseased disk material and fuse the joint between opposing vertebral bodies. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain associated with movement of an intervertebral joint having diseased disk material. Generally, fusion techniques involve removal of the diseased disk and packing the void area with a suitable matrix for facilitating a bony union between the opposing vertebral bodies.
Surgical devices for facilitating interbody fusion have also been developed. These devices typically provide for maintaining appropriate intervertebral spacing and stabilization of the vertebrae during the fusion process. Generally, these devices are referred to as cages. Examples of such devices are disclosed in, for example, U.S. Pat. Nos. 5,458,638, 5,489,307, 5,055,104, 5,026,373, 5,015,247, 4,961,740, 4,743,256 and 4,501,269, the entire disclosures of which are incorporated herein by reference.
Generally, the fusion device is implanted within a site prepared between opposing vertebrae. Typically, the site is a bore formed in the disk material and extends through the cortical end plates and into the cancellous bone of the opposing vertebrae. Many of the present fusion devices have a chamber enclosed by a cylindrical or rectangular wall that substantially contacts the entire interior surface of the bore. After placement of the device into the bore, the enclosed chamber (interior of the cage) can be filled with bone chips or other suitable material for facilitating bony union between the vertebrae.
Most of the present fusion devices provide vertebral stabilization during the fusion process by contact of the entire outer wall of the fusion device with substantially the entire interior surface of the wall of the insertion bore. While support provided by contact of the device with the entire wall of the bore provides adequate vertebral stabilization during the fusion process, it also has many disadvantages. For example, the greater the overall contact area of the device with the surface of the bore, the slower the rate at which new bone can grow into the bore to stabilize the joint. In addition, the greater the surface area of the device that contacts the surface area of the bore, the less continuity that can occur between the bone that is external to the device and the bone that is internal to the device. This lack of continuity of bone can translate into reduced structural integrity of the bony union. Furthermore, reducing the amount and continuity of the bone growth into the fusion site can cause the patient's body to rely on the device for long term stabilization rather than relying on the structural integrity of the new bony union. The potential orthopedic problems resulting from the body's reliance on orthopedic implants for structural support are well known.
Moreover, because most fusion devices are manufactured with materials that are radiopaque to typical diagnostic imaging modalities, assessment of the status of new bone growth during the fusion process can be limited.
Accordingly, there is a continuing need for improved intervertebral stabilizing devices and methods. The present invention is directed to addressing these needs.
SUMMARY OF THE INVENTION
The invention is directed to procedures for intervertebral stabilization of opposing vertebrae. The disclosure provides implants, instruments and methods for stabilization or fusion of opposing vertebrae.
At various locations throughout the specification, lists of examples are provided. It should be noted that the examples are provided for illustrative purposes and are not intended to limit the scope of the invention.
An implant according to the invention includes an implant body having a first and second end spaced apart by a longitudinal axis of the implant. The implant body includes a first transverse member and a second transverse member maintained in spaced apart relationship by a central support member. The transverse members each include a bearing surface oriented to contact opposing vertebral surfaces.
The bearing surfaces of the implant can be linear, curved or other suitable configuration. In addition, the bearing surfaces can include a pattern for anchoring the implant and/or resisting displacement once the implant is inserted between opposing vertebrae.
An implant of the invention provides a reduced displacement volume relative to the insertion bore necessary to accommodate the implant. The central support member or transverse members can also include openings which further reduce the displacement volume of the implants. In addition to enhancing the continuity of the new bone growth between the stabilized vertebral bodies, the reduced displacement volume of the implant facilitates assessment of the fusion process using known imaging modalities.
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Ray Cervical Threaded Fusion Cage,Surgical Dynamics, 1994.
Merchant & Gould P.C.
Snow Bruce
Sulzer Spine-Tech Inc.
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