Manufacturing orthopedic parts using supercritical fluid processing techniques

• US 6,506,213 B1
• Filed: 09/08/2000
• Issued: 01/14/2003
• Est. Priority Date: 09/08/2000
• Status: Expired due to Term

• Current Assignee: Ferro Corporation
• Original Assignee: Ferro Corporation
• Inventors: Wang, J. Don, Mandel, Frederick S.
• Primary Examiner(s): Isabella, David J.
• Application Number:
  US09/658,250
• Time in Patent Office: 858 Days
• Field of Search: 424/93.1, 424/424, 424/425, 424/426, 424/443, 523/444, 523/342, 264/121, 623/18.11, 623/16.11, 623/66
• US Class Current: 623/16.11
• 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 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2/4644 Preparation of bone graft, bone plugs or bone dowels, e.g. grinding or milling bone material bone material A61F2/28; disintegrating or milling devices B02C
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30065 thermoplastic, i.e. softening or fusing when heated, and hardening and becoming rigid again when cooled
• CPC Class Codes: A61F 2002/30957 using a positive or a negative model, e.g. moulds
• CPC Class Codes: A61F 2210/0071 thermoplastic
• CPC Class Codes: A61F 2310/00293 containing a phosphorus-containing compound, e.g. apatite
• CPC Class Codes: A61L 27/427 of other specific inorganic materials not covered by A61L27/422 or A61L27/425
• CPC Class Codes: A61L 27/50 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: B29C 44/348 by regulating the temperature and/or the pressure, e.g. suppression of foaming until the pressure is rapidly decreased

Abstract

Orthopedic parts are manufactured using supercritical fluid processing techniques in which starting materials and a process medium are mixed in a reactor to form a supercritical fluid slurry. The starting materials include a source of calcium ions and a polymer matrix for the calcium ions. The process medium preferably is carbon dioxide which is supplied to the reactor in a supercritical state or which is heated and pressurized in the reactor to attain a supercritical state. A conduit connects the reactor to a mold that has a cavity of a desired shape for an orthopedic part. A flush valve interconnects the bottom of a reactor and the conduit. When the flush valve is opened, the slurry is directed through the conduit into the mold where solidification occurs very rapidly. The resultant product is a strong, porous structure that simulates autogenic

Claims

1. A method for manufacturing an orthopedic part, comprising:

providing a reactor having a mixer;

providing a mold that has a cavity of a shape suitable to form an orthopedic part;

providing a conduit that connects the reactor and the mold;

charging the reactor with starting materials that include a source of calcium ions and a matrix for the calcium ions;

providing supercritical fluid in the reactor;

mixing the starting materials and the supercritical fluid in the reactor for a period of time sufficient to form a supercritical fluid slurry;

transferring the slurry from the reactor into the mold through the conduit; and

permitting the slurry to solidify in the cavity.

2. The method of claim 1, wherein the supercritical fluid is selected from the group consisting of carbon dioxide, water, nitrous oxide, methane, ethane, ethylene, propane, pentane, benzene, methanol ethanol, isopropanol, various fluorocarbons such as cholrotrifluoromethane and monofluoromethane, toluene, pyridine, cyclohexane, decalin, cyclohexanol, o-xylene, and tetralin.

3. The method of claim 1, wherein the step of providing supercritical fluid in the reactor is accomplished by charging a liquid into the reactor, and thereafter heating and pressurizing the reactor contents so that the liquid attains a supercritical state.

4. The method of claim 3, wherein the liquid is carbon dioxide.

5. The method of claim 4, wherein the carbon dioxide is heated to a temperature within the range of 32-133°

C. and is pressurized to a pressure within the range of 72-400 bar.

6. The method of claim 1, wherein, during the step of mixing, the reactor is maintained at a temperature below the melting point of the starting materials.

7. The method of claim 1, wherein at least a portion of the supercritical fluid is vented from the mold as the step of transferring is occurring.

8. The method of claim 1, wherein the source of calcium ions is selected from the group consisting of calcium hydroxy apatite, tri-basic calcium phosphate, calcium salts of condensed phosphates, calcium sulfate, gypsum hemi-hydrate, gypsum dihydrate, monovalent, divalent, and multivalent complexes of salts of calcium acetate and other organic calcium salts, calcium edetate and other chelated complexes of calcium.

9. The method of claim 1, wherein the matrix for the calcium ions is a thermoplastic polymer, a thermoset polymer, or a combination of thermoplastic and thermoset polymers.

10. The method of claim 9, wherein the matrix is selected from the group consisting of hydroxy-methyl cellulose and its derivatives, polylactide-co-glycolide, polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, polyethylene-vinyl acetate, polyenol-ketone, polyacrylic acid, polycarbophil, polyacrylamides, poly-N-isopropyl acrylamide, polyacrylates, polyethylene glycol, polyglycolic acid, polylactic acid, poly-ε

-caprolactone, poly-3-hydroxybutyrate, polyortho esters, polyanhydrides, polyamino acids, pseudo-polyamino acids, polyamide-enamines, polyamido amines, polyurethanes, azopolymers, polydimethylsiloxane, and polyphosphazenes.

11. The method of claim 1 further comprising the step of providing an orifice in the conduit.

12. The method of claim 11, wherein the orifice has a diameter within the range of about 0.0254 centimeter to about 0.254 centimeter.

13. The method of claim 1, further comprising the step of providing a nozzle having multiple openings in the conduit.

14. The method of claim 13, wherein the openings in the nozzle have a diameter within the range of about 0.0524 centimeter to about 0.254 centimeter.

15. The method of claim 1, wherein the step of mixing is accomplished by a blade or helical mixer.

16. The method of claim 15, wherein the mixer is rotated at a speed within the range of 1-150 rpm.

17. An orthopedic part produced by the method of claim 1.