Chemically crosslinked ultrahigh molecular weight polyethylene for artificial human joints
OwnerRonald Salovey, Harry A. McKellop +1inventors
InventorsRonald Salovey, Harry A. McKellop, Fu-Wen Shen
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Abstract
The present invention discloses a method for enhancing the wear-resistance of polymers by crosslinking them, especially before irradiation sterilization. In particular, this invention presents the use of chemically crosslinked ultrahigh molecular weight polyethylene in in vivo implants.
Claims41
A method for producing a crosslinked polymer with increased ability to withstand wear, comprising the steps of:
- a) crosslinking a polymer to form a crosslinked polymer;
- b) determining the degree of crystallinity of the crosslinked polymer;
- and
- c) adjusting reaction conditions such that the degree of crystallinity of the polymer after crosslinking is reduced by 10% to 50%;
- wherein the crosslinking is achieved by a method selected from the group consisting of:
- i) irradiation crosslinking of the polymer when it is in a molten state;
- ii) photocrosslinking of the polymer in the melt;
- and
- iii) crosslinking of the polymer with a free radical generating chemical.
A method for producing a crosslinked polymer with increased ability to withstand wear, comprising the steps of:
- a) crosslinking a polymer to form a crosslinked polymer without irradiating the polymer in its solid state;
- b) irradiating the crosslinked polymer in its solid state at a sterilization dose;
- and
- c) selecting for the crosslinked polymer which, after the irradiation in step (b), possesses a degree of crystallinity of about 45% or less.
A method for producing a crosslinked polymer with increased ability to withstand wear, comprising the steps of:
- a) crosslinking a polymer to form a crosslinked polymer without irradiating the polymer in its solid state;
- b) annealing the crosslinked polymer;
- c) irradiating the crosslinked polymer in its solid state at a sterilization dose;
- and
- d) selecting for the crosslinked polymer which, after the irradiation in step (c) and the annealing in step (b), possesses a degree of crystallinity of about 45% or less.
A method for making a crosslinked polymer suitable for use in vivo implant, said crosslinked polymer has an increased ability to withstand wear, said method comprising the steps of:
- a) reducing crystallinity of the polymer by crosslinking the polymer;
- and
- b) molding the resulting polymer into a shape suitable for in vivo implant;
- wherein the crosslinking of step (a) does not include irradiating the polymer in a solid state.
An in vivo implant made by a polymer produced by the method comprising the steps of:
- a) reducing the crystallinity of the polymer to enable it to better withstand wear;
- and
- b) molding the polymer into a shape suitable for in vivo implant;
- wherein the reduction of crystallinity in step (a) does not include irradiating the polymer in a solid state.
A polyhydrocarbon capable of maintaining a degree of crystallinity of about 42% or less after gamma irradiation to an average dose of about 3.4 Mrad or less.
A crosslinked in vivo implant comprising a component of an animal joint, said in vivo implant being capable of suffering about one-fifth or less of the wear suffered by an uncrosslinked in vivo implant, wherein the crosslinked in vivo implant and the uncrosslinked in vivo implant are made of UHMW polyethylene and have been sterilized by irradiation, and the crosslink is achieved by a method selected from the group consisting of:
- a) irradiation crosslinking of the UHMW polyethylene when it is in a molten state;
- b) photocrosslinking of the UHMW polyethylene in the melt;
- and
- c) crosslinking of the UHMW polyethylene with a free radical generating chemical.
An in vivo implant made from a polyhydrocarbon having a crystallinity of about 43% or less.
Dependencies are inferred from the claim text.