Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-06-01
2001-09-11
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S018110, C623S022110
Reexamination Certificate
active
06287342
ABSTRACT:
The invention relates to a prosthetic part to be implanted into the end of a thighbone adjacent to the hip joint.
A prosthetic part of this type is described in DE 37 07 518 A1.
After such a prosthetic part has been implanted, spongy substance grows between the anchorage pillars of the cage structure, as a result of which the anchorage section of the prosthetic part is dynamically and firmly connected to the end of the thighbone. After they have healed into the bone, prosthetic parts of this type which can be implanted without the use of cement are so firmly connected to the bone that removal which may possibly become necessary often necessitates opening of the sections of the cortical substance of the bone adjacent to the anchorage section.
By means of the present invention a prosthetic part is to be developed further in such a way that removal of the prosthetic part from the thighbone is possible without removing parts of the cortical substance.
In accordance with the invention this object is achieved by means of a prosthetic part having the features specified in claim
1
or
6
.
In the case of the prosthetic part according to the invention, passages are present or can easily be created by removing webs of material located beneath indentations or by drilling the supporting plate free, through which passages a chisel or a slender milling cutter can be guided. In this way a slit can be produced in the section of the spongy substance adjacent to the cortical substance, as a result of which the cohesion between the spongy substance that has grown into the cage structure and the cortical substance is weakened. The bridges of spongy substance leading to the cortical substance that cannot be removed by the chisel or by the milling cutter can then be broken up by mechanical loading of the prosthetic part (e.g., impact and/or twisting, with application of considerable force). After this, the prosthetic part can be taken out of the bone.
Advantageous further developments of the invention are specified in the subordinate claims.
In the case of a prosthetic part the volume of spongy substance that has grown in is separable from the cortical substance of the bone on the two principal surfaces.
The further development of the invention permits an incision to be produced in the volume of spongy substance which may extend practically over the entire surface of contact with the cortical substance. In this way it is possible for the prosthetic part to be removed in a straightforward manner.
The further development of the invention is advantageous with regard to particularly rapid opening of the depression, whereby a secure and load-bearing connection of the edge of the plate section to the interior of the plate section is guaranteed by virtue of the depressions that have only slight depth. In the depressions having only slight depth the web of material can be removed by means of a milling cutter, whereby the walls of the depression may serve as a guide for the milling cutter.
The further development of the invention permits the setting angle of the chisel or milling cutter which is introduced into an opening or into an opened depression to be varied.
In the case of a prosthetic part a drill for drilling free the points of attachment of the anchorage pillars pertaining to the cage structure can be simply and precisely aligned with the axis of an anchorage pillar.
REFERENCES:
patent: 4770660 (1988-09-01), Averill
patent: 4888022 (1989-12-01), Huebsch
patent: 4904262 (1990-02-01), Bensmann
patent: 4904268 (1990-02-01), Alvarado
patent: 5002578 (1991-03-01), Luman
patent: 5002579 (1991-03-01), Copf et al.
patent: 5092899 (1992-03-01), Forte
patent: 5163964 (1992-11-01), Lazzeri et al.
Copf Franz
Holz Ulrich
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