Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-04-13
2001-03-20
Millin, Vincent (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023560, C623S023580, C623S901000, C501S082000
Reexamination Certificate
active
06203574
ABSTRACT:
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates to a prosthetic bone filler and a process for the production of the same.
2. Description of the Related Art
Recently, when a lacking site was produced in a bone due to bone diseases, injury and other causes, an artificial prosthetic material or prosthetic filler is embedded in the lacking site of the bone. The lacking sites of the bone to which the prosthetic filler is applied include a wide variety of bone sites such as cranium, vertebra and articulate. Furthermore, the materials used as a prosthetic filler include ceramic materials such as alumina or hydroxyapatite, metallic materials such as Ti or Co—Cr alloy, and resinous materials such as polymethyl methacrylate or high density polyethylene. Among these prosthetic fillers, the fillers made of alumina, hydroxyapatite and other ceramic materials have less flexibility than the bone itself, because they are solely made from the ceramic material. Due to less flexibility when only a small amount of bone surrounds the site in which the ceramic filler is embedded, the bone surrounding the filler can be sometimes destroyed when an external mechanical force or load is applied to the body having the embedded filler. To solve this problem, use of the prosthetic filler produced by mixing a ceramic material with a resinous material has been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 5-237180 discloses a bone bonding device including a core material, produced upon extrusion molding of a mixture of hydroxyapatite, a biologically degradable polymer, and a melt-molded coating of polylactic acid. However, due to lack of porosity, the bone bonding device does not exhibit ventilation properties, and hence, lacks bio-compatibility. Further, Japanese Unexamined Patent Publication No. 7-8547 discloses a prosthetic filler including a porous block of sintered calcium phosphate compound having impregnated in an inner and surface portion thereof a biologically absorbing polymeric substance. However, the prosthetic filler also does not exhibit bio-compatibility; and the mechanical characteristics substantially depend upon the ceramic material used, i.e., a calcium phosphate compound instead of a polymeric substance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a prosthetic bone filler having excellent bio-compatibility, and good flexibility.
Another object of the present invention is to provide a production process suitable for the production of such a prosthetic bone filler.
In an aspect of the present invention, there is provided a prosthetic bone filler which includes ceramic granules for use in a living body, the ceramic granules being bonded to each other with a polymeric substance, and having ventilation pores produced due to gaps between the adjacent the ceramic granules.
Preferably, the polymeric substance bonding the ceramic granules includes finely divided ceramic particles having a particle size smaller than that of the ceramic granules.
Preferably, the polymeric substance is able to be absorbed in a living body.
According to another aspect of the present invention, there is provided a production process for a prosthetic bone filler including ceramic granules for use in a living body, the ceramic granules being bonded to each other with a polymeric substance, and having ventilation pores produced due to gaps between the adjacent granules. The production process includes: adding the polymeric substance to the ceramic granules in portions, after the polymeric substance is divided into two portions, in a bonding process of the ceramic granules with the polymeric substance.
Preferably, the polymeric substance added as the first portion to the ceramic granules is mixed with the ceramic granules after heating to make the ceramic granules adhesive; subsequently the polymeric substance is added as the second portion in the form of solid particles to the ceramic granules; and subsequently the ceramic granules are heated after being mixed with the polymeric substance.
Preferably, the polymeric substance as the first portion has a particle size of less than one half of the maximum particle size of the ceramic granules, and the polymeric substance as the second portion has a particle size of at least twice the minimum particle size of the ceramic granules.
Preferably, finely divided ceramic particles having a particle size smaller than the ceramic granules to be bonded with the polymeric substance are further added to the polymeric substance as the second portion.
The present disclosure relates to subject matter contained in Japanese Patent Application No.10-120139 (filed on Apr. 14, 1998) which is expressly incorporated herein by reference in its entirety.
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Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Koh Choon P.
Millin Vincent
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