US5728748A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Non oxidizing polymeric medical implant
Assignee: Howmedica Osteonics Corp
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Filing: 1996-10-16
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Granted: 1998-03-17
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Expires: 2016-10-16
Abstract
Abstract A medical implant made of polymeric material having an increased oxidation resistance is formed by a method including the steps of placing a resin powder in a sealed container. A substantial portion of the oxygen is removed from the sealed container by either a vacuum, an oxygen absorbent or by flushing with inert gas. The container is then repressurized with a gas such as nitrogen, argon, helium or neon so that long term storage may be possible. On use, the resin is transferred to a forming device which both melts and forms the resin in an oxygen reduced atmosphere to produce a polymeric raw material such as a rod or bar stock. The medical implant is then formed from this raw material annealed and sealed in an air-tight package in an oxygen reduced atmosphere. The implant is then radiation sterilized and thereafter annealed in the package for a predetermined time and temperature sufficient to form cross-links between any free radicals in neighboring polymeric chains.
Inventors
- 👤 Deh-Chuan Sun
- 👤 Casper F. Stark
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:44
CPC Classifications
A; A61; A61L; A61L2/00; A61L2/02; A61L2/08; A61L2/081; A61L15/00; A61L15/16; A61L15/42; A61L15/60; A61L2/082; A61L2/087; A61L27/00; A61L27/14; A61L27/16; A61L29/00; A61L29/04; A61L29/041; A61L31/00; A61L31/04; A61L31/048; B; B29; B29C; B29C35/00; B29C35/02; B29C35/08; B29C35/0805; B29C2035/085; B29C43/00; B29C43/02; B29C43/16; B29K; B29K2023/00; B29K2023/04; B29K2023/06; B29K2023/0658; B29K2023/0683; 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; Y10S522/915; Y10S525/00; Y10S525/937; Y10S623/00; Y10S623/901
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
87 words
A medical implant comprising a formed olefinic material having a molecular weight greater than 400,000, said material irradiated in an atmosphere with no more than 1% oxygen in the absence of a free radical generation catalyst to form free radicals in the material and using heat to form cross-links between free radicals in neighboring polymeric chains in an atmosphere having no more than 1% oxygen at a temperature of at least 25° C. for a sufficient time to inactivate any residual free radicals by producing cross-links therebetween.
Claim 2
Dependent Claim
87 words
A medical implant comprising a formed olefinic material having a molecular weight greater than 400,000, said material irradiated in an atmosphere with no more than 1% oxygen in the absence of a free radical generation catalyst to form free radicals in the material and using heat to form cross-links between free radicals in neighboring polymeric chains in an atmosphere having no more than 1% oxygen at a temperature of at least 25° C. for a sufficient time to inactivate any residual free radicals by producing cross-links therebetween.
Claim 3
Dependent Claim
19 words
The medical implant of claim 1 wherein said free radicals include peroxy and hydroperoxy groups on the polymer chains.
Claim 4
Dependent Claim
15 words
The medical implant of claim 1 wherein said atmosphere comprises inert gas or a vacuum.
Claim 5
Dependent Claim
80 words
A medical implant comprising a formed olefinic polymeric material having a molecular weight of 400,000 to 10,000,000, said material irradiated while in an atmosphere having no more than 1% oxygen in the absence of a free radical generation catalyst and heated in an atmosphere having no more than 1% oxygen for a sufficient time and at a temperature of between 25° C. and the melting point of said olefinic material to form cross-links between free radicals in neighboring polymeric chains.
Claim 6
Dependent Claim
80 words
A medical implant comprising a formed olefinic polymeric material having a molecular weight of 400,000 to 10,000,000, said material irradiated while in an atmosphere having no more than 1% oxygen in the absence of a free radical generation catalyst and heated in an atmosphere having no more than 1% oxygen for a sufficient time and at a temperature of between 25° C. and the melting point of said olefinic material to form cross-links between free radicals in neighboring polymeric chains.
Claim 7
Dependent Claim
19 words
The medical implant of claim 4 wherein said free radicals include peroxy and hydroperoxy groups on the polymer chains.
Claim 8
Dependent Claim
15 words
The medical implant of claim 4 wherein said atmosphere comprises inert gas or a vacuum.
Claim 9
Dependent Claim
81 words
A medical implant made of an olefinic material having a molecular weight of 400,000 to 10,000,000 comprising polymeric chains having a free radical concentration of less than 1×10 17 /g achieved by a combination of irradiating said material in the absence of a free radical generation catalyst and heating said material to a temperature greater than 25° C. for at least about four hours in an atmosphere having no more than 1% oxygen prior to the oxidation of said free radicals.
Claim 10
Dependent Claim
81 words
A medical implant made of an olefinic material having a molecular weight of 400,000 to 10,000,000 comprising polymeric chains having a free radical concentration of less than 1×10 17 /g achieved by a combination of irradiating said material in the absence of a free radical generation catalyst and heating said material to a temperature greater than 25° C. for at least about four hours in an atmosphere having no more than 1% oxygen prior to the oxidation of said free radicals.
Claim 11
Dependent Claim
15 words
The medical implant as set forth in claim 7 wherein said polymeric material is polyethylene.
Claim 12
Dependent Claim
80 words
A medical implant comprising a formed olefinic material having a molecular weight greater than 400,000 and having improved properties resulting from first creating free radicals in the material by irradiating the material in the absence of a free radical generation catalyst in an atmosphere with no more than 1% oxygen and forming cross-links between said free radicals using heat while said material is in an atmosphere having no more than 1% oxygen at a temperature of at least 25° C.
Claim 13
Dependent Claim
80 words
A medical implant comprising a formed olefinic material having a molecular weight greater than 400,000 and having improved properties resulting from first creating free radicals in the material by irradiating the material in the absence of a free radical generation catalyst in an atmosphere with no more than 1% oxygen and forming cross-links between said free radicals using heat while said material is in an atmosphere having no more than 1% oxygen at a temperature of at least 25° C.
Claim 14
Dependent Claim
19 words
The medical implant of claim 9 wherein said free radicals include peroxy and hydroperoxy groups on the polymer chains.
Claim 15
Dependent Claim
15 words
The medical implant of claim 9 wherein said atmosphere comprises inert gas or a vacuum.
Claim 16
Dependent Claim
13 words
The medical implant of claim 11 wherein said irradiating is electron beam irradiation.
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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) | 2001-03-16 | 2001-09-15 | 2002-03-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-03-16 | 2005-09-15 | 2006-03-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-03-16 | 2009-09-15 | 2010-03-17 | $7700.00 | Window Closed / Lapsed |