Method of manufacturing an acetabular component

Patent metadata

Field	Value
Publication number	US-9718241-B2
Application number	US-201414156726-A
Country	US
Kind code	B2
Filing date	Jan 16, 2014
Priority date	Jan 30, 2008
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

An orthopedic component having multiple layers that are selected to provide an overall modulus that is substantially lower than the modulus of known orthopedic components to more closely approximate the modulus of the bone into which the orthopedic component is implanted. In one exemplary embodiment, the orthopedic component is an acetabular shell. For example, the acetabular shell may include an outer layer configured for securement to the natural acetabulum of a patient and an inner layer configured to receive an acetabular liner. The head of a femoral prosthesis articulates against the acetabular liner to replicate the function of a natural hip joint. Alternatively, the inner layer of the acetabular shell may act as an integral acetabular liner against which the head of the femoral prosthesis articulates.

First claim

What is claimed is:

1. A method of manufacturing an orthopedic component for implantation into a bone and defining an acetabular shell configured for use in a hip replacement surgery, the orthopedic component having a porous bone contacting layer, an interdigitation layer, and an inner layer, the method comprising:
determining an elastic modulus of the bone;
selecting a thickness of at least one of the porous bone contacting layer, the interdigitation layer, and the inner layer based on the elastic modulus of the bone; and
molding the inner layer to the porous bone contacting layer to form at least one of the porous bone contacting layer, the interdigitation layer, and the inner layer to have the selected thickness;
wherein the inner layer is formed from an antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene having a thickness of less than six millimeters, the inner layer being configured to receive a femoral component, and the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene being prepared by a process that includes:
combining ultrahigh molecular weight polyethylene with an antioxidant to form a blend;
processing the blend to consolidate the blend, wherein the consolidated blend has a melting point;
preheating the consolidated blend to a preheat temperature below the melting point of the consolidated blend; and
irradiating the preheated consolidated blend while maintaining the preheated consolidated blend at a temperature below the melting point of the consolidated blend;
wherein the antioxidant is substantially uniformly distributed throughout the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene; and
wherein the interdigitation layer is defined by a distance over which the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene of the inner layer infiltrates pores of the porous bone contacting layer.

2. The method of claim 1 , further comprising, after selecting a thickness, selecting a thickness of another of at least one of the porous bone contacting layer, the interdigitation layer, and the inner layer based on the elastic modulus of the bone.

3. The method of claim 1 , wherein the porous bone contacting layer comprises a porous metal.

4. The method of claim 1 , wherein the inner layer comprises a polymer.

5. The method of claim 1 , wherein the acetabular shell has an effective stiffness between 0.1 GPa and 15 GPa.

6. The method of claim 5 , wherein the acetabular shell has an effective stiffness between 0.1 GPa and 10 GPa.

7. The method of claim 6 , wherein said acetabular shell has an effective stiffness between 0.3 GPa and 1.5 GPa.

8. The method of claim 1 , wherein the porous bone contacting layer has an elastic modulus between 0.1 GPa and 15 GPa and said antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene has an elastic modulus between 0.1 GPa and 15 GPa.

9. The method of claim 1 , wherein the porous bone contacting layer includes a metal.

10. The method of claim 1 , wherein said porous bone contacting layer includes a reticulated vitreous carbon foam substrate coated with a biocompatible metal by chemical vapor deposition.

11. The method of claim 1 , further including forming a substantially hemispherical liner from a liner material, wherein the liner is configured for receipt within said acetabular shell.

12. The method of claim 11 , wherein the liner material includes ultrahigh molecular weight polyethylene.

13. The method of claim 1 wherein the inner layer further includes an integral locking feature.

14. The method of claim 13 , wherein the integral locking feature includes a groove configured to receive a snap ring or a spring ring.

15. The method of claim 14 , wherein the integral locking feature includes a Morse taper.

16. The method of claim 11 , wherein the liner and the shell are prevented from substantial relative translation by an integral locking feature.

17. The method of claim 1 , wherein the process to prepare the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene includes injection molding polyethylene to the porous bone contacting layer.

18. A method of manufacturing an acetabular component configured for use in a hip replacement surgery and implantation into a bone, the acetabular component having a porous bone contacting layer configured to contact and interface with the bone when the acetabular component is implanted, an interdigitation layer, and an inner layer, the method comprising:
determining an elastic modulus of the bone;
selecting a thickness of at least one of the porous bone contacting layer, the interdigitation layer, and the inner layer based on the elastic modulus of the bone; and
molding the inner layer to the porous bone contacting layer to form at least one of the porous bone contacting layer, the interdigitation layer, and the inner layer to have the selected thickness;
wherein the inner layer is formed from an antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene having a thickness of less than four millimeters, the inner layer is configured to receive a femoral component, and the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene being prepared by a process that includes:
combining ultrahigh molecular weight polyethylene with tocopherol to form a blend having between 0.1 and 3.0 weight percent tocopherol;
processing the blend to consolidate the blend, wherein the consolidated blend has a melting point;
preheating the consolidated blend to a preheat temperature below the melting point of the consolidated blend; and
irradiating the preheated consolidated blend with a total irradiation dose of between 90 kGy and 1000 kGy while maintaining the preheated consolidated blend at a temperature below the melting point of the consolidated blend, wherein the consolidated blend is secured to the porous bone contacting layer prior to irradiation;
wherein the tocopherol is substantially uniformly distributed throughout the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene;
wherein the porous bone contacting layer has a porosity of at least 55 percent;
wherein the interdigitation layer is defined by a distance over which the antioxidant stabilized crosslinked ultrahigh molecular weight polyethylene of the inner layer infiltrates pores of the porous bone contacting layer; and
wherein the acetabular component has an effective stiffness of between 0.3 GPa and 1.5 GPa.

19. The acetabular component of claim 18 , wherein the inner layer exhibits no visible deformations after undergoing 5 million cycles of uniaxial lading under at least 1,000 pounds of force.

Assignees

• Zimmer Inc

Inventors

• Case Kirt
• Popoola Oludele O
• Kissling Robby
• Mimnaugh Brion R
• Newsome Archie
• Panchison Clarence M
• Pletcher Dirk
• Schlemmer Randy
• Fang Zhibin
• Vivanco Juan
• Rufner Alicia
• Knight John

Classifications

• A61F2002/30495

  using a locking ring · CPC title

• A61F2/3094

  Designing or manufacturing processes · CPC title

• A61L27/50

  Materials characterised by their function or physical properties {, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials} · CPC title

• A61F2220/0025

  Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements · CPC title

• B29C45/14

  incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles {(B29C45/1671 takes precedence)} · CPC title