Patent US6017975A successfully refreshed from Google Patents.
US6017975A
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Process for medical implant of cross-linked ultrahigh molecular weight polyethylene having improved balance of wear properties and oxidation resistance
Assignee: DePuy Orthopaedics Inc
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Filing: 1997-08-15
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Granted: 2000-01-25
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Expires: 2017-08-15
Abstract
Abstract A medical implant of ultrahigh molecular weight polyethylene having an improved balance of wear properties and oxidation resistance is prepared by irradiating a preform of ultrahigh molecular weight polyethylene, annealing the irradiated preform in the absence of oxygen to a temperature at or above the onset of melting temperature, and forming an implant from the stabilized cross-linked polymer. Implants prepared according to the process of the present invention have comparable oxidation resistance and superior wear performance compared to unirradiated ultrahigh molecular weight polyethylene.
Inventors
- 👤 Kenneth Ashley Saum
- 👤 William Michael Sanford
- 👤 William Gerald Dimaio, Jr.
- 👤 Edward George Howard, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:50
CPC Classifications
A; A61; A61L; A61L31/00; A61L31/04; A61L31/048; A61L2/00; A61L2/02; A61L2/08; A61L2/14; A61L2/16; A61L2/20; A61L2/206; A61L27/00; A61L27/14; A61L27/16; B; B29; B29C; B29C35/00; B29C35/02; B29C35/08; B29C35/0805; B29C2035/085; B29C43/00; B29C43/02; B29C43/16; B29K; B29K2105/00; B29K2105/25; B29K2105/253; B29K2995/00; B29K2995/0037; B29K2995/0087; B29K2995/0089; B29L; B29L2031/00; B29L2031/753; B29L2031/7532; Y; Y10; Y10S; Y10S522/00; Y10S522/911; Y10S522/912; Y10S623/00; Y10S623/92
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
104 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating in a substantially oxygen-free atmosphere at a temperature above about 150° C. for a time sufficient to recombine substantially all of the free radicals and cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform while maintaining a substantially oxygen-free atmosphere; forming a medical implant from the cross-linked preform; packaging the medical implant in an air-permeable package; and sterilizing the packaged implant using non-irradiative methods.
Claim 2
Dependent Claim
104 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating in a substantially oxygen-free atmosphere at a temperature above about 150° C. for a time sufficient to recombine substantially all of the free radicals and cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform while maintaining a substantially oxygen-free atmosphere; forming a medical implant from the cross-linked preform; packaging the medical implant in an air-permeable package; and sterilizing the packaged implant using non-irradiative methods.
Claim 3
Dependent Claim
22 words
The process of claim 1 wherein the irradiating step comprises irradiating the preform with gamma radiation at a dose of 0.5-10 Mrad.
Claim 4
Dependent Claim
22 words
The process of claim 1 wherein the irradiating step comprises irradiating the preform with gamma radiation at a dose of 1.5-6 Mrad.
Claim 5
Dependent Claim
22 words
The process of claims 2 or 3 wherein the preform is contained in an inert atmosphere or vacuum during the irradiating step.
Claim 6
Dependent Claim
14 words
The process of claim 1 wherein the implant is sterilized using a gas plasma.
Claim 7
Dependent Claim
13 words
The process of claim 1 wherein the implant is sterilized using ethylene oxide.
Claim 8
Dependent Claim
18 words
The process of claim 1 wherein the annealing step is performed near or above the peak melting temperature.
Claim 9
Dependent Claim
19 words
The process of claim 1 wherein the annealing step is performed at a temperature greater than about 160° C.
Claim 10
Dependent Claim
20 words
The process of claim 1 wherein the annealing step is performed at a temperature of 150-170° C. for 12-60 hours.
Claim 11
Dependent Claim
52 words
The process of claim 1 wherein the annealing step is performed for a time sufficient to form a cross-linked preform having an oxidation level of less than 0.2 carbonyl area/mil sample thickness after aging the cross-linked preform at 70° C. for 14 days in oxygen at a pressure of about 5 atmospheres.
Claim 12
Dependent Claim
34 words
The process of claim 8 wherein the preform is irradiated with a dose of 1.5-6 Mrads and the irradiated preform is annealed at a temperature of 150-170° C. for a period of 12-60 hours.
Claim 13
Dependent Claim
24 words
The process of claim 1 wherein the annealing step comprises melting the irradiated preform and applying an isostatic or hydrostatic pressure of 33-70 kpsi.
Claim 14
Dependent Claim
37 words
The process of claim 1 further comprising pre-annealing the preform at a temperature of 280° C.-355° C. in an inert atmosphere without the application of external pressure for at least 0.5 hour prior to the irradiating step.
Claim 15
Dependent Claim
22 words
The process of claim 13 wherein the preform is pre-annealed at a temperature of about 320-355° C. for at least 3 hours.
Claim 16
Dependent Claim
77 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating in a substantially oxygen-free atmosphere at a temperature above about 150° C. to cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform while maintaining a substantially oxygen-free atmosphere; and forming a medical implant from the cross-linked preform.
Claim 17
Dependent Claim
77 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating in a substantially oxygen-free atmosphere at a temperature above about 150° C. to cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform while maintaining a substantially oxygen-free atmosphere; and forming a medical implant from the cross-linked preform.
Claim 18
Dependent Claim
22 words
The process of claim 15 wherein the irradiating step comprises irradiating the preform with gamma radiation at a dose of 0.5-10 Mrad.
Claim 19
Dependent Claim
22 words
The process of claim 15 wherein the irradiating step comprises irradiating the preform with gamma radiation at a dose of 1.5-6 Mrad.
Claim 20
Dependent Claim
22 words
The process of claims 16 or 17 wherein the preform is contained in an inert atmosphere or vacuum during the irradiating step.
Claim 21
Dependent Claim
14 words
The process of claim 15 wherein the implant is sterilized using a gas plasma.
Claim 22
Dependent Claim
13 words
The process of claim 15 wherein the implant is sterilized using ethylene oxide.
Claim 23
Dependent Claim
18 words
The process of claim 15 wherein the annealing step is performed near or above the peak melting temperature.
Claim 24
Dependent Claim
19 words
The process of claim 15 wherein the annealing step is performed at a temperature up to about 160° C.
Claim 25
Dependent Claim
20 words
The process of claim 15 wherein the annealing step is performed at a temperature of 150-170° C. for 12-60 hours.
Claim 26
Dependent Claim
52 words
The process of claim 15 wherein the annealing step is performed for a time sufficient to form a cross-linked preform having an oxidation level of less than 0.2 carbonyl area/mil sample thickness after aging the cross-linked preform at 70° C. for 14 days in oxygen at a pressure of about 5 atmospheres.
Claim 27
Dependent Claim
34 words
The process of claim 22 wherein the preform is irradiated with a dose of 1.5-6 Mrads and the irradiated preform is annealed at a temperature of 150-170° C. for a period of 12-60 hours.
Claim 28
Dependent Claim
37 words
The process of claim 15 further comprising pre-annealing the preform at a temperature of 280° C.-355° C. in an inert atmosphere without the application of external pressure for at least 0.5 hr prior to the irradiating step.
Claim 29
Dependent Claim
23 words
The process of claim 26 wherein the preform is pre-annealed at a temperature of about 320° C.-355° C. for at least 3 hours.
Claim 30
Dependent Claim
24 words
The process of claim 15 wherein the annealing step comprises melting the irradiated preform and applying an isostatic or hydrostatic pressure of 33-70 kpsi.
Claim 31
Dependent Claim
19 words
The process of claim 15 wherein the annealing step comprises melting the preform at a temperature of 280-355° C.
Claim 32
Dependent Claim
19 words
The process of claim 29 wherein the annealing step comprises melting the preform at a temperature of 320-355° C.
Claim 33
Dependent Claim
13 words
A medical implant prepared according to the process of claims 1 or 15.
Claim 34
Dependent Claim
50 words
A cross-linked ultrahigh molecular weight polyethylene having a swell ratio of less than about 5 and an oxidation level of less than about 0.2 carbonyl area/mil sample thickness after aging the ultrahigh molecular weight polyethylene at 70° C. for 14 days in oxygen at a pressure of about 5 atmospheres.
Claim 35
Dependent Claim
50 words
A cross-linked ultrahigh molecular weight polyethylene having a swell ratio of less than about 5 and an oxidation level of less than about 0.2 carbonyl area/mil sample thickness after aging the ultrahigh molecular weight polyethylene at 70° C. for 14 days in oxygen at a pressure of about 5 atmospheres.
Claim 36
Dependent Claim
44 words
The cross-linked ultrahigh molecular weight polyethylene of claim 31 having an oxidation level of less than about 0.1 carbonyl area/mil sample thickness after aging the ultrahigh molecular weight polyethylene at 70° C. for 14 days in oxygen at a pressure of about 5 atmospheres.
Claim 37
Dependent Claim
14 words
A medical implant comprising the ultrahigh molecular weight polyethylene of claims 31 or 32.
Claim 38
Dependent Claim
93 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating at a temperature above about 150° C. for a time sufficient to recombine substantially all of the free radicals and cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform; forming a medical implant from the cross-linked preform; packaging the medical implant in an air-permeable package; and sterilizing the packaged implant using non-irradiative methods.
Claim 39
Dependent Claim
93 words
A process for preparing a medical implant having an improved balance of wear properties and oxidation resistance comprising the steps of: irradiating a preform of ultrahigh molecular weight polyethylene to form free radicals; annealing the irradiated preform by heating at a temperature above about 150° C. for a time sufficient to recombine substantially all of the free radicals and cross-link the ultrahigh molecular weight polyethylene; cooling the cross-linked preform; forming a medical implant from the cross-linked preform; packaging the medical implant in an air-permeable package; and sterilizing the packaged implant using non-irradiative methods.
Claim 40
Dependent Claim
26 words
The process of claim 35 wherein the irradiating step comprises irradiating the preform with gamma radiation at a dose of about 0.5 to about 10 Mrad.
Claim 41
Dependent Claim
19 words
The process of claim 35 wherein the annealing step is performed at a temperature greater than about 160° C.
Claim 42
Dependent Claim
20 words
The process of claim 35 wherein the annealing step is performed at a temperature of 150-170° C. for 12-60 hours.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-01-24 | 2003-07-26 | 2004-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-01-24 | 2007-07-26 | 2008-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-01-24 | 2011-07-26 | 2012-01-25 | $7700.00 | Window Closed / Lapsed |