Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1993-09-30
1996-11-05
Shay, Randy C.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 228
Patent
active
055711855
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a process for the production of a bone implant made from metal or plastic, in which a positive moulding is produced from a member of moulding material, which at least in sections possesses an open-pore or open-cell structure on the surface comprising a predetermined porous structure made from moulding material, the positive moulding is embedded into a ceramic embedding compound filling the pores of the open-pore structure to form a core, the moulding material is removed by the use of heat which produces, spaces in the remaining core, which spaces were previously occupied by the moulding material the spaces are filled by casting or centrifuging with the metal or plastic, and subsequently the core material is removed to form the implant.
The invention also relates to a bone implant.
A process is known for example from German Patent Specification 31 06 917 or from German Patent Specification 32 24 265, in which an open-pore plastic moulding member, for example an open-pore or open-cell natural or synthetic sponge, is used as the positive moulding. The open-pore surface of the positive moulding results in the production of an implant having an open-pore surface structure, whereby the open pores of the cells in each case should be the same size or larger than the spongy trabeculae of a natural bone, so that the ingrowth of the osseous tissue with subsequent bone formation begins immediately after implantation. However as the pore size occurs statistically distributed within predetermined limits in the plastic member used as the positive cast, and as the pores are also at random, an implant surface is produced in which the pores are locally distributed at random. The ingrowth of spongiosa trabeculae, which in the adjacent osseous tissue possess a naturally ordered structure, is impeded by the arbitrary distribution of the pores on the implant surface.
The object of the invention is therefore to provide a process for the production of a bone implant possessing an open-pore surface structure covering comprising a predetermined pore structure.
A further object of the invention is also to provide a bone implant having an open-pore surface structure which facilitates the ingrowth of the adjacent osseous tissue in comparison to known structures.
The object is achieved in accordance with the invention by an implant which made of metal or plastic, processing an open-pore surface structure and which is characterised in that the pore size and/or pore density on the surface of the implant has a local distribution which corresponds to the trabecula structure of the bone environment in which the implant is attached.
The advantages of the invention lie particularly in the fact that implants having an open-pore surface structure can be produced which, with respect to their local distribution of the pore size and density, correspond to the spongiosa trabecula structures present at the implant site to an extent hitherto not achieved. This adaption of the pore distribution with respect to size, density and depth is possible according to the invention on the surface of an implant and allows the pore and cell sizes to be adapted to the spongiosa trabecula structure of the surrounding osseous tissue so that many spongiosa trabeculae also encounter a correspondingly large number of pores arranged according to the natural conditions. As the distribution of the spongiosa trabeculae in the bone are ordered with respect to their size, density and with respect to their local position, a corresponding arrangement of the surface pores of the implant produced in accordance with the invention can improve the anchoring quality.
In the process according to the invention the local distribution of the pore size and/or pore density of the structural covering applied to the positive moulding is reproduced on the surface of the bone implant produced. Therefore a distribution of the pore sizes and/or density is particularly preferably chosen so that this distribution roughly corresponds to the structure of the sp
REFERENCES:
patent: 4492577 (1985-01-01), Farris et al.
patent: 5042560 (1991-08-01), Ahlers
Eska Implants GmbH
Shay Randy C.
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