Porous Material for Use as Implant, Bone Replacement and in General as Material

• US 20080319547A1
• Filed: 06/07/2005
• Published: 12/25/2008
• Est. Priority Date: 06/07/2004
• Status: Active Grant

• Current Assignee: Boneartis AG
• Original Assignee: Zow AG
• Inventors: Draenert, Klaus
• Granted Patent: US 8,814,936 B2
• Time in Patent Office: Days
• US Class Current: 623/16.11
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• 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 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30205 conical
• CPC Class Codes: A61F 2002/30224 cylindrical
• CPC Class Codes: A61F 2002/30245 Partial spheres
• CPC Class Codes: A61F 2002/30263 cubical
• CPC Class Codes: A61F 2002/30266 wedge-shaped parallelepipeds
• CPC Class Codes: A61F 2002/30273 pyramidal
• CPC Class Codes: A61F 2002/30276 frustopyramidal
• CPC Class Codes: A61F 2002/30289 helically-coiled
• CPC Class Codes: A61F 2002/30291 spirally-coiled, i.e. having a 2D spiral cross-section
• CPC Class Codes: A61F 2002/30677 Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30952 using CAD-CAM techniques or NC-techniques
• CPC Class Codes: A61F 2002/30957 using a positive or a negative model, e.g. moulds
• CPC Class Codes: A61F 2002/30968 Sintering
• CPC Class Codes: A61F 2210/0004 bioabsorbable
• CPC Class Codes: A61F 2230/0065 : toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2230/0067 : conical
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0071 : spherical
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2230/0084 : cubical
• CPC Class Codes: A61F 2230/0086 : Pyramidal, tetrahedral, or wedge-shaped
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• 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: A61F 2310/00131 : Tantalum or Ta-based alloys
• CPC Class Codes: A61F 2310/00203 : containing alumina or aluminium oxide
• CPC Class Codes: A61F 2310/00293 : containing a phosphorus-containing compound, e.g. apatite
• CPC Class Codes: A61F 2310/00353 : Bone cement, e.g. polymethylmethacrylate or PMMA
• CPC Class Codes: A61F 2310/00365 : Proteins; Polypeptides; Degradation products thereof
• CPC Class Codes: A61L 27/44 : having a macromolecular matrix
• CPC Class Codes: A61L 27/56 : Porous materials, e.g. foams or sponges

Abstract

Implants and methods for producing same are described, the implants featuring an adjustable porous shell, the inside being continuously interconnectingly adjustably porous and which can be sintered net shaped; these implants exhibit a high compression stability and show, when being combined with filler materials with or without active agents, different chemical, physical-mechanical, biomechanical or also pharmacological properties. The essential features of the manufacturing process are described in FIG. (1) and comprise expandable shaping elements, deformable elastic tools, the application of defined negative pressures, temperatures during defined application periods in combination with combined materials, which can be separated from each other physically, chemically or mechanically and removed.

Claims

1. An implant body comprising:

a porous implant body including a shell having a surface, penetrated by pores having an adjustable diameter, and further including an inner structure comprising a cavity or a conglomerate of cavities surrounded by ball-shaped shells, and shell framing that encompasses a connected cavity system made of hollow balls or ball-shaped cavities, which is continuously interconnected by means of a pore system in the shell framing, the pore system having an adjustable diameter.

2. The implant body of claim 1, shaped as a cuboid or cube, cylinder, cone or disc, half shell or halfball, ball segment, ball cut, wedge or ring or disc ring, pyramid or frustrum of pyramid, spiral or screw.

3. The implant body of claim 1, configured such that the outer shell is structured in the shape of circular or radial, longitudinal, oblique or helical, parallel or crossing extending contractions, channels or bulges or both, singular or in a plurality thereof, or in the shape of single or plural elevations, recesses, or pins.

5. The implant body of claim 1, configured such that the pore of the outer shell has a diameter smaller than the diameter of the cavity connected therewith, namely in the ratio of 1:

5 to 1;

1.5, in average 1;

2 to 1;

3.

6. The implant body of claim 1, preferably having the shape of porous balls or ball-shaped structures of a size between 0.8 mm and 12 mm in diameter, in average between 1-2 mm and 3-6 mm in diameter, and an interconnected inner pore system having diameters of the pores between 80 mm and 1500 mm, preferably 150 mm to 600 mm.

7. The implant body of claim 1, configured such that a conglomerate of individual implants is formed, preferably of ball shape, being connected to each other through bridges having adjustable widths and encompassing a cavity system being interrelated as such, which enables that the preferably ball-shaped implant bodies may be encompassed by the bones in a manner that a physiological sponge bone framing is generated, the passages of which through the connecting bridges of the implant bodies are predetermined.

8. The implant body of claim 1, configured such that the frame material is a phosphorite, especially tri-calciumphosphate (TCP) or tetra-calciumphosphate, a hydroxyapatite, a calcium carbonate or calcium-sulfate-composition, or also an aluminium oxide ceramic, a collagen, a polyaminoacid or any other absorbable polymer, but also an acrylate or derivate thereof, a polymethyl-methacrylate or a copolymer thereof, with or without phosphate, calcium sulphate or calcium carbonate as filler material, or a metal, preferably a CoCrMo alloy, titanium or tantalum or an alloy thereof.

9. The implant body of claim 1, configured such that the cavity system is filled or coated completely or partially with an absorbable or non-absorbable organic or inorganic filler material, having dampening or reinforcing properties, in a manner that the inner filling is restricted to the inside of the implant body or completely fills same, but does not extend beyond the outer shell, or regularly or irregularly wells out of the pores of the outer shell and forms drop-shaped and/or ball-shaped or similarly shaped elevations over the outer shell, to prevent them completely or nearly completely from being regularly or irregularly distributed over the surface, micro-movements of plural identical or similar implant bodies, for example in one fill.

10. The implant body of claim 9, configured such that as the filler material, an absorbable polymer, e. g. poly-amino acid, a polylactide, polyglactine, glycoside or similar material, generally polyacetals, poly-acid amides or polyester, but also not absorbable polymers such as polymethylmethacrylate or similar polymers, agarose gels or mixtures of agarose gels and a calciumphosphate or a calcium carbonate is used.

11. The implant body of claim 1, configured such that exclusively the center or the center axis or the cavities along the center axis, interrelated or individual distributed cavities or groups of cavities are filled with a material according to claims 9 and 10, said material comprising an active agent which is released fast or slowly, momentary or retarded and centrifugally distributes by diffusion over the free implant surface.

12. The implant body of claim 1, configured such that said implant body includes at least one of an active agent, a growth factor, a bone morphogenetic protein or combinations thereof, or comprises an antibiotic or a hormone, an immunosuppressive drug, a zytostaticum or a mixture of growth factors and an antibiotic or a combination of different agents.

13. The implant body of claim 12, configured such that Gentamycin, Clindamycin, Streptomycin or any other bacteriostatic or bactericide agent is used as the antibiotic.

14. The implant body of claim 1, configured such that wide and narrow cavity systems are formed therein and that are arranged interrelated or interrupted, individual or in groups or also along an axis and have interconnections of different widths, and that the cavities therewith can be filled more easily or less easily with filler materials or agents or combinations thereof.

15. The implant body of claim 1, configured such that cavities of different size are structured with an interconnecting framing of an other absorbable or non-absorbable material, to include a large cavity having a shell-shaped wall made of hydroxyapatite having a shell-shaped structured framing made of an easily absorbable tri-calciumphosphate, wherein a continuously combined implant body comprising hydroxyapatite and tri-calciumphosphate is generated.

16. An implant body of claim 1, having differing porosity, with or without filler material with or without an active agent, partially or completely filled in its cavity system.

17. An implant device of claim 1, comprising a first implant body and a second implant body mechanically inserted in said first implant body, said implant device composed of a porous or solid material with or without an active agent and is either absorbable or non-absorbable.

24. The method for producing an implant body according to claim 1, comprising the steps of:

the outer mould of the implant body having definite masses is multiplied with a shrinking factor of the material of the supporting frame and produced mechanically, or by an impression method or by CAD/CAM,

producing a silicon mould in a tool with silicone using a casting method, said mould representing the implant body except for the lid,

filling the silicone tool with the shaping elements and closed with a silicone lid;

Filling the tool through the lid with a malleable mass of the supporting frame, including a mixture of agar agar and hydroxyapatite;

subsequently, the tool with the shaping elements, surrounded by the mass of the supporting frame, is charged with a negative pressure in a closed chamber and cooled-down, subsequently, the removal from the mould and the removal of the shaping elements, including the foamed polystyrene balls in acetone occurs,

after the stepwise dehydration in the acetone, the implant body in the freezer is dried slowly in air and subsequently further dehydrated in the exsiccator by applying phosphorpentoxide,

the thus dried implant body, e.g. consisting of an agar agar/hydroxyapatite or also an agar agar/TCP mixture, is burnt in a sintering furnace;

the thus gained porous implant body features a continuous porosity including its complete surface and is true to size and free of cracks.

25. The method of claim 24 for producing porous ball-shaped implant bodies according to claim 1, comprising the following modifications:

the silicone print is produced by a monolayer of steel or polyamide balls which are moulded in by ⅘ and

which are subsequently removed mechanically from the elastic material,

the resulting cavity system is filled with smaller shaping elements, e.g. foamed polystyrene balls, by using a filler tool having a perforated silicone bottom, and subsequently closed with a perforated lid having a perforated silicone deposit;

bottom and lid comprise boreholes for being filled with the framing mass or for venting,

the tool is filled with the mass of the supporting frame, e.g. a mixture of agar agar and HA or tri-calciumphosphate, subsequently charged with negative pressure in a closed chamber and cooled-down,

the thus solidified implant bodies are pushed carefully from the mould and the shaping elements are removed, e.g. the foamed polystyrene balls in acetone, dehydrated and subsequently burnt at 1000°

C. to 1300°

C., e. g. in a zirconium pot.

26. Producing of an implant according to claim 1, as a result of the following method steps:

producing an elastically or plastically deformable tool, e.g. with an injection moulding method, according to a CAD/CAM design or any other technical design, or with a printing or casting method of a direct template, in any case in consideration of the shrinking factor and configured such that it can be filled with shaping elements and closed again, e.g. as a sandwich or as a nearly closed body having an opening and a lid and venting means on the opposite side;

filling of the deformable tool with shaping elements, e.g. expandable polystyrene balls or directly with Styrofoam®

balls, or other shaping materials in ball shape or any other shape, being easily removable, e.g. sugar or salt balls, gelatine or any other material being easily removable;

injecting into a filling tool, e.g. a main tool in an injection die casting machine, or an other filling device for the framing material;

filling by injecting or suctioning of the framing material with or without defined negative pressure;

cooling of the tool, together with the implant, in the vacuum chamber by applying a defined negative pressure and over a defined period of time;

removing the implant, together with the shaping elements, and physically or chemically dissolving of the shaping elements;

burning of an e.g. ceramic implant at 900°

C. to 1400°

C. in a sintering furnace.

4. The implant body of claim, configured such that the inner structure corresponds to a bowl-shaped sponge bone or cancellous bone.

18. A method for producing implants comprising the following steps:

filling of shaping elements in a mould having a perforated bottom and lid, such that the shaping elements cannot fall out, by use of a filter grid, the bottom and lid being arranged relative to each other such that the shaping elements can be retained in close contact,

intrusion of the mould with the shaping elements being retained in shape into a key form, which receives the mould in a flush manner, filled with hot wax having a melting temperature between 60°

C. and 90°

C., as a rule 80°

C., and curing the wax,

extracting the mould with the cured wax framing which comprises the shaping elements, and releasing and removing the shaping elements, such as by dissolving of air-containing polystyrene balls as the shaping elements in acetone or dissolving of sugar balls in water or a similar removing of other physically or chemically removable shaping bodies, which does not affect wax framing,

filling of the cavity system generated with smaller shaping elements, e.g. sugar balls in a trickling method with the help of a vibraxer or Styrofoam®

balls in a suction method comprising a suction means and a filter lid, in order to avoid the sucking through of the shaping elements,

filling of the remaining cavity system around the shaping elements with a liquid material, such as including a mixture of agar agar and a calciumphosphate, as tri-calciumphosphate or hydroxyapatite that use capable of flowing and curing, such as polymethylmethacrylate (PMMA) or a copolymer thereof,

solidifying the material being capable of flowing around the shaping elements in the wax framing, including cooling the agar/calciumphosphate mixture, or including self curing of a PMMA material and subsequently removing of the shaping materials and removing of the wax framing by an appropriate method, including dissolving of sugar balls or salts being crystallized out from a PMMA frame in water, or dissolving of air-containing polystyrene balls from an agar-calciumphosphate mixture in acetone and subsequently dissolving of the wax in an appropriate solvent, including methyl cellulose solve acetate, or burning the wax during the sintering in a sinter oven at temperatures between 900°

C. and 1400°

C.

19. The method of claim 18 wherein:

sugar or salt balls between 300 mm and 15 mm are used as shaping elements and are dissolved in water, and generated pores of the wax framing are filled with smaller sugar or salt balls or air-containing polystyrene balls or other soluble air-containing or solid plastics which are subsequently surrounded by a framing material and subsequently again removed by means of water or solvent or also heat.

20. The method of claim 18 further comprising the step of:

air-containing shaping elements in the pores of the wax framing are exposed to a defined negative pressure in a temperate vacuum-sealed chamber and simultaneously cooled through a coolable setting plate, which results in the fact that the air-containing shaping elements, when expanding, displace soft wax into the ball clearances and wider contact bridges form between the elements, in particular in the boundary zone towards the wax;

the result thereof is, after suctioning of the framing material and its curing, a porous structure of the implant body being adjustable and having a definable interconnection and surface porosity due to the extent and duration of an acting vacuum.

21. The method of claim 20 comprising the method steps described in claim 18, modified in the following method step:

air-containing shaping materials in the pores of the wax framing are surrounded by a framing material capable of flowing and completely filled;

the implant body is subsequently placed into a vacuum chamber, e. g. being tempered by a setting plate, together with the air-containing, mostly foamed, shaping elements and the framing material surrounding same, and charged with a defined negative pressure at 40 to 60°

C., preferably 50°

C.;

in this context, it may also be advantageous to operate with a cooled setting plate at 4°

C. to 12°

C. and increased negative pressure;

same results in an expansion of the shaping elements and therefore directly influences the macro porosity and the passages (interconnections), but in particular also the surface pores;

the vacuum is exactly adjustable between 800 mbar and 150 mbar absolute pressure and also adjustable temporally by a time switch, the temperature in the container can be cooled-down fast, e.g. through a setting plate made of metal, such that the achieved result is retained by the stiffening of the wax framing.

22. The method of claim 18 comprising the following modifications:

filling of shaping materials, e.g. sugar balls, into a tool and injection-moulding of the ball filling with polystyrene foam, which cures subsequently,

if necessary, intermediate storage in a defined humid chamber, a process which results in an etching of the sugar balls in the interface to the framing material and in flowing bridges between the shaping elements, a process which can be distributed equally throughout the implant by a regular relocating of the implant body, subsequently drying in a drying furnace and removing of the shaping bodies with water or heat, without the step of intermediate storage in a humid chamber, the removal of the shaping sugar or also salt elements, e.g. as balls, occurs immediately in the water,

filling the cavities in the foamed polystyrene framing with shaping elements and proceeding as described in claim 18.

23. The method of claim 18 comprising the following modification:

as the framing material, a castable and self-curing silicone is used, which is surrounded, e.g. by ⅘

, by sugar balls or also air-containing polystyrene as shaping elements, or solid metal or plastic balls or shaping elements, which can be removed subsequently either chemically, physically or also carefully mechanically,

the filling of the pores of the silicon framing with smaller shaping elements can be performed e.g. with sugar balls, but also with foamed polystyrene balls, which is performed in the first case by a trickling method and in the second case preferably by suctioning through a filter grid,

in case the pores and gap system is, as described in claim 18, filled e.g. with an agar/hydroxyapatite mixture and subsequently exposed to a defined negative pressure in a vacuum chamber, passages and boundary porosities are formed due to the deformability of the tools and the expansion of the shaping elements.