Prosthesis component and a method of producing it

• US 5,554,190 A
• Filed: 10/21/1994
• Issued: 09/10/1996
• Est. Priority Date: 04/24/1992
• Status: Expired due to Term

• Current Assignee: Thurgauer Kantonalbank
• Original Assignee: Klaus Draenert
• Inventors: Draenert, Klaus
• Primary Examiner(s): Milano, Michael J.
• Application Number:
  US08/325,350
• Time in Patent Office: 690 Days
• Field of Search: 623/16, 623/901, 623/22, 378/18, 378/57, 378/56, 378/207, 364/474.24, 364/413.14, 364/413.15, 364/413.16, 364/413.19, 364/468
• US Class Current: 128/898
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• CPC Class Codes: A61F 2/30942 for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2002/30014 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2002/30131 horseshoe- or crescent- or C-shaped or U-shaped
• CPC Class Codes: A61F 2002/30952 using CAD-CAM techniques or NC-techniques
• CPC Class Codes: A61F 2002/4631 the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2230/0013 Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped
• CPC Class Codes: A61F 2250/0018 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2310/00017 Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: Y10S 623/901 Method of manufacturing prosthetic device
• CPC Class Codes: Y10S 623/914 Bone

Abstract

The present invention relates to a prosthesis component for anchoring with or without using bone cement and to a method of producing it. The prosthesis component, which can be produced by CAD and image-analysis methods, provides for the largest possible surface for the transmission of forces, and its mass and rigidity can be adapted to the individual properties of the bone.

Claims

1. A method of producing a prosthesis component for anchoring with using bone cement and also for anchoring without using bone cement, in a bony bed in the epiphyseal, metaphyseal or diaphyseal portion of a bone, the bone having outer and inner contours, the prosthesis component produced thereby providing a surface for transmission of forces between the bone and the prosthesis component, the prosthesis component having a mass and a rigidity, the method comprising the following steps:

three-dimensionally reconstructing the bony bed from a series of sections of the bone;

producing a contour model of the bone including the outer and inner contours;

determining mean density of the bone in individual bone sections; and

adapting the prosthesis component to the bony bed by determining a material property of the prosthesis component to correlate with the mean density in the individual bone sections.

2. The method according to claim 1, wherein the prosthesis component is adapted such that the material property is proportional to the mean density of the individual bone sections.

3. The method according to claim 1, wherein the sections are sections obtained by a method selected from the group consisting of:

CT scan, nuclear spin tomography, and histology.

4. The method according to claim 1, wherein, in the reconstruction of the bony bed, stacked images of individual sections are digitized and electronically stored subsequently processed to the contour model.

5. The method according to claim 1, wherein the prosthesis component comprises a shaft, and wherein a shape of the shaft is adapted to the contour model.

6. The method according to claim 1, wherein a ratio between a cross-section of the prosthesis component and a cross-section of the bony bed is determined in each individual bone section to correlate to the mean density per unit area determined in the individual bone section.

7. The method according to claim 6, wherein the bone density per unit area, compared with a specific density per unit area of a corresponding normal bone, results in a factor which is used as correlation factor for the determination of the ratio between the cross-section of the prosthesis component and the cross-section of the bony bed.

8. The method according to claim 7, wherein the prosthesis component is for use with cement, and wherein the cross-section of the inner contour of the contour model is reduced by 20 to 50% according to the correlation factor to determine the cross-section of the prosthesis component.

9. The method according to claim 1, wherein an area of a cross-section of the prosthesis component is between 30 and 90% of an area of a corresponding cross-section of the bony bed.

10. The method according to claim 1, wherein the prosthesis component is for use with cement, wherein cross-sectional circumference of the prosthesis component is constantly 60 to 80% of cross-sectional circumference of the inner contour of the bony bed.

11. The method according to claim 1, wherein the prosthesis component is implanted with bone cement in a cement sheath, wherein a cross-section of the prosthesis component is determined from the mean density of individual bone sections such that thickness of the cement sheath is approximately inversely proportional to the mean density of the individual bone sections.

12. The method according to claim 1, wherein data of the contour model of the prosthesis component are transmitted to a computer design system and processed such that the prosthesis component can be implanted along an implantation axis.

13. The method according to claim 1, wherein the material of the prosthesis component is selected from a group consisting of:

CoCrMo alloy, titanium, titanium ally, steel, plastics, and composite material.

14. The method according to claim 1, wherein the material property is mass of the prosthesis component.

15. The method according to claim 1, wherein the material property is rigidity of the prosthesis component.

16. The method according to claim 7, wherein the prosthesis component is for cement-free use, and wherein the cross-section of the inner contour of the contour model is reduced by 1 to 20% according to the correlation factor to determine the cross-section of the prosthesis component.

17. The method according to claim 1, wherein the prosthesis component is for cement-free use, wherein cross-sectional circumference of the prosthesis component is constantly 70 to 95% of cross-sectional circumference of the inner contour of the bony bed.

18. A prosthesis component produced by the method comprising the following steps:

three-dimensionally reconstructing a bed from a series of section of a bone;

producing a contour model of the bone including the outer and inner contours;

determining mean density of the bone in individual bone sections; and

adapting the prosthesis component to the bony bed by determining a material property of the prosthesis component to the bony bed by determining a material property of the prosthesis component to correlate with the mean density in the individual bone sections.