High precision manufacture of polyurethane products such as spinal disc implants having gradual modulus variation

• US 20070050037A1
• Filed: 08/17/2006
• Published: 03/01/2007
• Est. Priority Date: 10/08/2002
• Status: Abandoned Application

• Current Assignee: Ranier Limited
• Original Assignee: Ranier Technology Limited
• Inventors: Johnson, Scott, Snell, Robert, Andrews, Geoffrey, Cable, Martin
• Application Number:
  US11/505,632
• Publication Number:
  US 20070050037A1
• Time in Patent Office: Days
• US Class Current: 623/17.160
• CPC Class Codes: A61F 2/30756 Cartilage endoprostheses A61F2/3603 takes precedence
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2002/30014 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2002/30133 kidney-shaped or bean-shaped
• CPC Class Codes: A61F 2002/30807 Plurality of blind bores
• CPC Class Codes: A61F 2230/0015 Kidney-shaped, e.g. bean-shaped
• CPC Class Codes: A61F 2250/0018 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2310/00365 Proteins; Polypeptides; Degradation products thereof
• CPC Class Codes: A61F 2310/00796 Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: B29C 41/20 incorporating preformed parts or layers, e.g. moulding inserts or for coating articles
• CPC Class Codes: C08G 18/0895 Manufacture of polymers by continuous processes C08G18/0838 takes precedence
• CPC Class Codes: C08G 18/40 High-molecular-weight compounds C08G18/2805 takes precedence
• CPC Class Codes: C08G 2120/00 Compositions for reaction injection moulding processes

Abstract

A process for making a polymeric product having a gradual variation in modulus through at least a portion of the product is disclosed together with an artificial spinal disc formed using the process.

Claims

1. A method of forming a polymeric article comprising:

injecting a first polymeric material having a first stoichiometry into a mold;

injecting a second polymeric material having a second stoichiometry into the mold; and

molding a polymeric material article having a pre-determined portion exhibiting a gradual variation in Young'"'"'s modulus.

2. A method according to claim 1, wherein the first polymeric material is a first polyurethane and the second polymeric material is a second polyurethane.

3. A method according to claim 2, wherein the first and the second polyurethanes are formed by reacting at least a multifunctional isocyanate and a polyol.

4. A method according to claim 2, wherein relative amounts of the multifunctional isocyanate and the polyol that react to form the second polyurethane are different than relative amounts of the multifunctional isocyanate and the polyol reacting to form the first polyurethane.

5. A method according to claim 2, further comprising mixing at least the multifunctional isocyanate and the polyol to form a first reactive mixture and mixing at least the multifunctional isocyanate and the polyol to form a second reactive mixture.

6. A method according to claim 5, further comprising intensively mixing at least the multifunctional isocyanate and the polyol to form a first reactive mixture and intensively mixing at least the multifunctional isocyanate and the polyol to form a second reactive mixture.

7. A method according to claim 5, further comprising introducing the first reactive mixture into an extruder and introducing the second reactive mixture into an extruder.

8. A method according to claim 7, comprising introducing the first reactive mixture into a first extruder followed by introducing the second reactive mixture into the first extruder.

9. A method according to claim 7, wherein polymerization reactions that form the first polyurethane and the second polyurethane occur in the extruder.

10. A method according to claim 1, comprising forming the article in the mold.

11. A method according to claim 1, comprising injecting the first polymeric material into the mold followed by injecting the second polymeric material into the mold.

12. A method according to claim 1, wherein the first polymeric material and the second polymeric material are injected simultaneously into the mold.

13. A method according to claim 1, wherein the first polymeric material and the second polymeric material are injected into the mold at different injection rates.

14. A method according to claim 1, wherein different amounts of the first polymeric material and the second polymeric material are injected into the mold.

15. A method according to claim 1, wherein polymerization reactions continue in the mold.

16. A method according to claim 15, wherein polymerization reactions between the first polymeric material and the second polymeric material occur in the mold.

17. A method according to claim 1, wherein the first polymeric material and the second polymeric material are formed in the same apparatus.

18. A method according to claim 1, wherein the first polymeric material and the second polymeric material are formed in different apparatus.

19. A method according to claim 1, further comprising arranging a first end plate in the mold and forming the article including the first end plate bonded to a surface of the article.

20. A method according to claim 19, wherein a second end plate is bonded to a surface of the article.

21. A method according to claim 20, wherein the first end plate and the second end plate are covalently bonded to polymeric material at surfaces of the article.

22. A method according to claim 1, wherein the article is an implant.

23. A method according to claim 22, wherein the article is a spinal disc.

24. A method according to claim 1, wherein the article includes a nucleus region and an annulus region.

25. A method according to claim 24, wherein the nucleus region surrounds the annulus region.

26. A method according to claim 24, wherein a Young'"'"'s modulus of the nucleus region is less than a Young'"'"'s modulus of the annulus region.

27. A method according to claim 26, wherein the pre-determined portion is between the nucleus region and the annulus region.

28. A method according to claim 1, wherein the Young'"'"'s modulus varies continuously across the portion of the article.

29. An artificial spinal disc according claim 24, wherein the pre-determined portion comprises a polymeric material having a gradual variation in stoichiometry.