Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2001-10-12
2003-07-29
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023740, C623S023290, C623S020170
Reexamination Certificate
active
06599322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the production of textured surfaces for medical and industrial applications and is directed more particularly to the production of undercut micro recesses in a surface, a surgical implant made thereby, and a method for fixing an implant to bone.
2. Description of the Prior Art
It is known to use textured surfaces on surgical implants for the purpose of encouraging bone adhesion and thus stabilize the location of the implant relative to the bone. For example, in an artificial hip, consisting of a femoral sub-assembly for positioning in a patient's femur, and an acetabular sub-assembly for positioning in the patient's acetabulum, the femoral sub-assembly includes an artificial stem which is typically provided with a textured surface, and the acetabular sub-assembly includes an acetabular cup which is typically provided with a textured surface, the textured surfaces being provided to promote bone in-growth.
The desirability of roughened, textured, bone-engaging surfaces to assure stable positioning of surgical implants has been recognized in U.S. Pat. No. 5,298,115, issued Mar. 29, 1994, in the name of Ian Leonard, U.S. Pat. No. 5,456,723, issued Oct. 10, 1995, in the name of Samuel G. Steinemann, U.S. Pat. No, 5,603,338, issued Feb. 18, 1997, in the name of Keith D. Beaty, U.S. Pat. No. 5,853,561, issued Dec. 29, 1998, in the name of Bruce A. Banks, and U.S. Pat. No. 5,965,006, issued Oct. 12, 1999, in the names of Roland Baege et al.
To produce such textured surfaces, one known method is to provide a mass of titanium spheres vacuum fused onto the datum surface of the implant. This method is described in U.S. Pat. No. 4,834,756, issued May 30, 1989, to Robert V. Kenna. In a similar procedure, described in U.S. Pat. No. 4,644,942, issued Feb. 24, 1987 to Kenneth R. Sump, an extractable component and titanium spheres are densified as a coating, which is fused onto a datum surface of the implant, and the extractable component subsequently is extracted. While an improvement over untreated metal, questions have arisen over the longevity of usefulness of the implanted devices utilizing such surfaces. It is questionable whether there is substantial genuine adhesion. It is believed that the voids formed by the spheres are not sufficient for long-term nourishment of ingrowing tissue and/or bone. Further, there have been failures of prosthetics treated in this manner because of the fusing process adversely affecting metallurgical properties of the implant material, and because of difficulties in removing manufacturing contaminants, such as cutting oils, from the fused sphere network. Still further, the original datum surface, which can be accurately determined, is lost by the application of the coating spheres.
The formation of perforated thin metallic sheets or plates by means of chemical milling and/or photo-chemical etching techniques has been described in U.S. Pat. No. 3,359,192, issued Dec. 19, 1967, in the names of Hans-Joachim Heinrich et al, U.S. Pat. No. 5,606,589, issued Feb. 25, 1997, in the names of Anthony J. Pellegrino et al, and U.S. Pat. No, 5,814,235, issued Sep. 29, 1998, in the names of Anthony J. Pellegrino et al. The processes therein described have been found lacking in precise control over the degree and extent of roughness or texturing.
In U.S. Pat. No. 5,258,098, issued Nov. 2, 1993, to Donald J. Wagner et al, U.S. Pat. No. 5,507,815, issued Apr. 16, 1996, to Donald J. Wagner et al, and U.S. Pat. No. 6,193,762, issued Feb. 27, 2001, in the names of Donald J. Wagner, et al, there are described chemical and electrochemical etching processes used in conjunction with random sprayed patterns of maskant to create a pattern of dots resistant to etching. After etching and maskant stripping repeatedly, a complex pattern is produced. While complex in appearance, such patterns offer little predictability and repeatability between implants, and lack engineered datum points.
Accordingly, there remains a need for a method for producing an engineered textured surface for interlocking with an adjacent body, such as a bone or other ingrowing body.
SUMMARY OF THE INVENTION
An object of the invention is, therefore, to provide a method for producing a textured surface which is adapted to interlock with an adjacent body.
A further object is to provide a method for producing undercut micro recesses in a surface of a body.
A still further object is to provide a method for producing such recesses in a desired pattern which is measurable and predictable, and which can be duplicated and repeated precisely in any selected number of surfaces.
A still further object is to provide a method for producing a surgical implant device wherein the material of the device retains its metallurgical properties throughout production.
A still further object is to provide a method for producing textured surfaces for surgical implants, which surfaces promote the ingrowth of tissue and/or bone to securely interconnect the implant and the tissue and/or bone.
A still further object is to provide a method for producing such surfaces which include undercut and interconnecting recesses which promote and facilitate ingrowth of bone and which, upon implantation, facilitate a “scratch fit” with bone, to stabilize the position of the surface on the bone and to initiate an interconnection process between the implant and the bone. The “scratch fit” is accomplished by the textured surface scraping bone from the implant site during a press fit implantation, thereby producing autografted bone in the voids of the textured surface.
A still further object of the invention is to provide methods for attaching a surgical implant to bone.
A still further object of the invention is to provide a method for bone harvesting and seeding of a surgical implant with particulate bone matter during attachment of the implant to the bone.
A still further object is to provide a method for making a surgical implant which exhibits a precise fit with a bone implant site, to reduce micro-motion between the implant and the bone site.
A still further object of the invention is to provide a surgical implant having undercut micro recesses with sharply defined edges in a bone-engaging surface thereof.
With the above and other objects in view, a feature of the invention is the provision of a method for producing a multiplicity of undercut micro recesses in a surface of an article, such that the article thereby exhibits a greater fractal area at a level below the surface than is exhibited at the surface, the method comprising the steps of applying a maskant layer to substantially an entirety of the article surface, removing the maskant layer in selected loci to expose underlying portions of the article surface in a selected, predictable, and reproducible pattern, applying an etchant to the exposed underlying surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of the maskant layer and produce a multiplicity of undercut recesses, and removing the remaining maskant layer portions to provide the article surface in exposed condition with the multiplicity of recesses undercut and comprising interconnected recesses, to provide an engineered pattern of the recesses.
In accordance with a further feature of the invention, there is provided a method for producing a multiplicity of undercut micro recesses in a surface of an article in a selected pattern which can be repeated in any selected number of surfaces. The method includes the steps of applying a maskant layer to substantially an entirety of a selected surface of the article. The maskant layer is then removed by computer-directed laser ablation in programmed loci to expose underlying portions of the surface of the article in a programmed pattern. An etchant is then applied to the exposed underlying surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of
Amrich Mark P.
Buturlia Joseph
Lynch Robert F.
Rolfe Jonathan L.
McDermott Corrine
Miller Cheryl
Morgan & Lewis & Bockius, LLP
Tecomet Inc.
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