Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-10-08
2001-02-06
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023620
Reexamination Certificate
active
06183516
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods for chemically bonding two dissimilar polymers. More particularly, it is directed to a method for providing covalent bonding between a polymeric prosthetic device and polymethylmethacrylate bone cement.
Numerous surgical procedures are available for the reconstruction and/or repair of bones. Many such methods involve the use of prosthetic devices produced from polymeric materials such as polyethylene. Indeed, a variety of polymeric prostheses are commercially available for use in repairing damaged hip joints, knee joints etc., due to such diseases as osteoarthritis, rheumatoid arthritis, traumatic arthritis, avascular necrosis, sickle cell anemia and osteoporosis.
The most common technique for reconstructing damaged bone tissue involves initially cutting and drilling the bone so that it conforms to the shape of the securement portion of a prosthesis. A number of shallow holes are generally drilled or cut into the surfaces of the bone tissue adjacent to the prosthesis in order to form projecting cavities into which bone cement can flow so as to form a strong mechanical interlock between the cement and the bone tissue.
In the majority of such procedures, the prosthesis is secured into place by use of polymethylmethacrylate (PMMA) bone cement. PMMA is a self-curing acrylic resin; it polymerizes at room temperature without any external application of heat. However, PMMA is a “luting” agent, rather than an adhesive, i.e., the cement does not produce any chemical bond with bone tissue to hold the prosthesis in place. Rather, the PMMA fills irregularities in the bone and hardens to form a mechanical interlock. Because the bond so formed is mechanical in nature, preparation and application technique can be very important in the overall success of these procedures. Ineffective bond formation can result in eventual loosening of the prosthesis and failure of the product. This, in turn, results in discomfort to the patient and a need for surgical replacement of the prosthesis.
U.S. Pat. Nos. 5,002,582 and 5,512,329 report methods for the preparation of modified surfaces by covalently bonding polymer molecules thereto by external activation of latent reactive groups, such as photactivatable ketones, carried by the polymer molecules. The polymer molecules are so spatially oriented as to enable one or more of the latent reactive groups to come into covalent bonding proximity with the substrate surface. Upon activation of the latent reactive groups by applying external stimulation, typically ultraviolet radiation, covalent bonds can be formed between the latent reactive group and the substrate.
There is a need in the orthopedic arts for simple and cost effective methods for providing improved adhesion between a prosthetic device and the bone cement to which it is bonded. A great deal of effort and expense has been directed at attempts to provide such improved attachment methods. However, for the most part, these attempts have proved largely unsuccessful and most surgeons continue to utilize PMMA in the manner described above. We provide herein a method for producing prostheses that are attached to bone cement via covalent chemical bonding, resulting in improved bonding strength between a polymeric prosthetic device and bone.
SUMMARY OF THE INVENTION
In a first aspect of this invention there is provided a method for achieving improved bonding between a polymeric prosthetic device and bone. The method involves producing a surface modified prosthetic device by reacting the surface of a prosthetic device with one or more of the disclosed surface modifying agents. A surface modifying agent of the invention comprises a first reactive group and a second reactive group. When a surface modifying agent is reacted under appropriate conditions with the surface of a prosthetic device, the first reactive group becomes covalently bonded to a plurality of the surface molecules of the prosthetic device.
Therefore, in another aspect of the invention there is provided a surface modified polymeric prosthetic device that is capable of improved bonding with a bone cement such as PMMA. The surface molecules of the surface modified prosthetic device are covalently bonded to the surface modifying agent via the first reactive group, whereas the second reactive group is available for participation in the polymerization reaction of the bone cement.
In another aspect of the invention, the surface modified prosthetic device is contacted with bone in the presence of a bone cement such as PMMA under conditions effective to cause covalent bonding between the second reactive group on the surface modified prosthetic device and the PMMA. As a result, a surface modified prosthetic device of the invention can be attached to bone with improved adhesive strength by virtue of the covalent bond formed between the surface of the modified device and the bone cement with which it is contacted.
DETAILED DESCRIPTION OF INVENTION
Prior to the present invention, the adhesion of prosthetic devices to bone surfaces has for the most part been mechanical in nature. In a typical procedure, the surface of the device is roughened or otherwise prepared before bone cement is applied so as to increase the resulting degree of mechanical adhesion. However, mechanical adhesion can be problematic and failure of the bond between a prosthesis and bone is not uncommon. It would be preferred for such prostheses to be directly or indirectly chemically bonded to the surfaces to which they are applied, for example by creating a permanent chemical bond between the bone cement and the surface of the prosthesis.
Therefore, in accordance with one aspect of the present invention, there is provided a method for improved bonding between a prosthetic device and bone cement, and as a result between the prosthetic device and bone. The surface of the prosthetic device is modified by reaction with a compound referred to herein as a surface modifying agent. The surface modifying agent contains at least one chemical group/functionality that is reactive with the polymeric surface of the prosthetic device, hereinafter referred to as the first reactive group. The surface modifying agent also contains at least one chemical group/functionality that is reactive with bone cement, said group being hereinafter referred to as the second reactive group.
Thus, the surface modifying agents of the present invention are bifunctional, i.e., they contain functionalities that are reactive both with the polymer surface of a prosthetic device and with monomer, oligomer and/or polymer of the bone cement being used. As a result, prostheses can be bonded to bone with improved adhesion strength by virtue of the covalent bond formed between the surface molecules of the prosthesis and bone cement.
The first reactive group of the surface modifying agent of the invention can be broadly defined as a group which can respond to a specific applied external stimulus to undergo active specie generation, where the active species so produced is capable of becoming chemically bonded to the surface of a polymeric prosthetic device. Thus, the first reactive group is the atom or group of atoms on the surface modifying agent which retains its chemical structure substantially unchanged under conditions of storage but which, upon activation, is capable of forming one or more covalent bonds with the polymer molecules on the surface of the prosthetic device.
The first reactive group of the surface modifying agent may be chosen to be responsive to various portions of the electromagnetic spectrum; those that are responsive to ultraviolet, visible or infrared portions of the spectrum are typically preferred. Such reactive groups have been referred to as latent reactive groups and are generally well known, as are the residues formed upon activation and reaction with a substrate (see for example U.S. Pat. No. 5,002,582, incorporated herein by reference). Upon application of the appropriate external stimulus, the first reactive group generates ac
Burkinshaw Brian D.
Frautschi Jack R.
Isabella David J.
Lyren Philip S.
Sulzer Orthopedics Inc.
LandOfFree
Method for improved bonding of prosthetic devices to bone does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for improved bonding of prosthetic devices to bone, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for improved bonding of prosthetic devices to bone will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2567733