Adaptable stem for endoprosthesis

• US 5,376,123 A
• Filed: 04/30/1993
• Issued: 12/27/1994
• Est. Priority Date: 12/07/1989
• Status: Expired due to Fees

• Current Assignee: AO Forschungsinstitut Davos
• Original Assignee: AO Forschungsinstitut Davos
• Inventors: Klaue, Kaj, Chareire, Jean L.
• Primary Examiner(s): Isabella, David
• Assistant Examiner(s): BRITTINGHAM, DEBRA
• Application Number:
  US08/054,832
• Time in Patent Office: 606 Days
• Field of Search: 623/16, 623/17, 623/18, 623/19, 623/20, 623/22, 623/23
• US Class Current: 623/23.19
• CPC Class Codes: A61B 17/7098 wherein the implant is permeable or has openings, e.g. fenestrated screw hollow surgical screws A61B17/864
• CPC Class Codes: A61B 17/8802 Equipment for handling bone cement or other fluid fillers
• CPC Class Codes: A61B 17/8841 Tools specially adapted to engage a prosthesis
• CPC Class Codes: A61F 2/30721 Accessories
• CPC Class Codes: A61F 2/30723 Plugs or restrictors for sealing a cement-receiving space tools for inserting plugs A61F2/4614; sealing collars for use during cementing A61B17/8808
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/30907 Nets or sleeves applied to surface of prostheses or in cement
• CPC Class Codes: A61F 2/30965 Reinforcing the prosthesis by embedding particles or fibres during moulding or dipping
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2/367 Proximal or metaphyseal parts of shafts trochanteric devices connected to said proximal parts A61F2/30739
• CPC Class Codes: A61F 2002/30067 Coating or prosthesis-covering structure made of thermoplastic material
• CPC Class Codes: A61F 2002/30125 elliptical or oval
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30566 Helical springs
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30583 filled with hardenable fluid, e.g. curable in-situ
• CPC Class Codes: A61F 2002/30586 having two or more inflatable pockets or chambers
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/3082 Grooves
• CPC Class Codes: A61F 2002/30917 for avoiding direct contact between bone and implant, e.g. extensible membrane for preventing contamination or for easy removal
• CPC Class Codes: A61F 2002/30919 : Sleeves
• CPC Class Codes: A61F 2002/3694 : with longitudinal bores
• CPC Class Codes: A61F 2002/4631 : the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2210/0085 : hardenable in situ, e.g. epoxy resins
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0008 : elliptical or oval
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

A stem for an endoprosthesis to be anchored in a bone (3) comprises a chamber (4) which surrounds the stem periprosthetically, which can be sealed in a pressure tight manner and which can be expanded with a thermoplastic or thermostable filling material (16). The rigid stem (1) of the endoprosthesis is connected mechanically to the bone (3) via the expandable chamber (4) by means of the filling material (16). The filling material is isolated from the bone (3), however, by the wall of the pressure-tight chamber (4). This makes it possible to ensure that the outer wall of the chamber (4) adjacent to the bone is extremely biocompatible.

Claims

1. A stem assembly for an endoprosthesis to be anchored in a bone comprising a stem;

means defining at least one expansible chamber (4) having a first wall sealed to said stem in a pressure-tight manner and a second wall at least partly enclosing said stem (1) and being expandable to contact an interior surface of said bone;

a viscous liquid filler; and

valve means for selectively introducing said filler into said chamber for expanding and substantially permanently pressurizing said chamber with hydrostatic pressure.

2. A stem assembly according to claim 1 wherein said filler is a fluid.

3. A stem according to claim 1 or 2 wherein said chamber (4) is periprosthetic.

4. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall made of silicone.

5. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall comprising braid impregnated with silicone.

6. A stem according to claim 5, wherein said braid includes two mutually crossing series of fibers (42) evincing a slope of about 45°

relative to the stem axis (43).

7. A stem according to claim 6 wherein fibers of said braid are made of a material selected from the group consisting of carbon, polyester and polyamide.

8. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall having a thickness of less than 0.5 mm.

9. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall of said chamber (4) having more tensile strength in a proximal region (41) and in a distal region (7) than in a central region.

10. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes an outside surface coated with hydroxy-apatite particles.

11. A stem according to claim 1 wherein said valve means in said chamber (4) includes a one-way valve (9).

12. A stem according to claim 1 or 2 wherein said means defining said at least one chamber (4) includes means for affixing said at least one chamber to said prosthesis stem (1) such that said stem when implanted is capable of limited axial displacement relative to said bone and said chamber is axially immovable relative to said bone.

13. A stem according to claim 1 or 2 wherein said means defining said at least one chamber (4) includes, at least at the surface facing the bone (3), a biocompatible material.

14. A stem according to claim 1 or 2 wherein said means defining said at least one chamber (4) is formed, at least at the surface facing the bone (3), with a carbonaceous textured surface.

15. A stem according to claim 2 wherein said filler (16) comprises a liquid thickened with filler particles of carbon.

16. A stem assembly according to claim 8 wherein said wall has a thickness of less than 0.25 mm.

17. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall made of polyurethane.

18. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes a wall comprising braid impregnated with polyurethane.

19. A stem according to claim 1 or 2 wherein said means defining said at least one chamber includes an outside surface coated with carbon particles.

20. A stem according to claim 1 wherein said chamber is expansible to occupy substantially all space in said cavity between said stem and said bone.

21. A stem according to claim 20 wherein said chamber is collapsed and is tightly against said stem during insertion and is subsequently expanded.