Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Patent
1995-09-07
1998-05-12
Isabella, David
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
623 12, 606194, 606198, A61F 204
Patent
active
057499195
DESCRIPTION:
BRIEF SUMMARY
This invention concerns an elastic prosthesis for widening a conduit in a living being, in particular a blood vessel, the prosthesis being generally of an elongated and substantially cylindrical shape.
The invention also concerns a method for manufacturing such a prosthesis.
This type of prosthesis is frequently known by the American term "stent" and can be used in particular, but not exclusively, in blood vessels presenting stenosis, the coronary arteries in particular. As the natural internal diameter of the vessel is reduced in the stenosed region, angioplasty is increasingly being used and consists of widening this diameter by means of an inflatable balloon arranged on a catheter, and then of replacing this balloon by a permanent elastic prosthesis whose the rest diameter is larger than that of the vessel, so that the prosthesis presses permanently against the internal wall of the vessel. In order to put the prosthesis in place it is compressed to reduce its diameter and to insert it in the extremity of a tube which is fed to the desired location, then it is pushed out of the tube so as it dilates due to its inherent elasticity.
Publications EP-A-O 183 372 and WO 83/03752 describe prostheses of this type consisting of a trellis of elastic filaments which are plaited or woven together. Furthermore, the deformations and movements during use of the prosthesis create friction between the wires at the points at which they cross and this prevents the use of metal wires provided with special coatings designed to prevent deposits. These prostheses are relatively expensive. A simpler prosthesis, described for example in WO 83/00997, comprises a single wire wound round in a configuration similar to that of a helical spring. In order to put this prosthesis in place, its diameter can be reduced by twisting it and by fixing it thus on an instrument which serves to feed it into the conduit or the vessel to be widened. However, prostheses of this type have proved susceptible to longitudinal movement by snaking due to the constraints placed on them by the vessel, especially in the region where the natural diameter of the vessel is reduced. This phenomenon is produced by the wire sliding longitudinally along its helical trajectory. The main resistance to this movement, apart from the friction on the walls of the vessel which is relatively minimal, comes from the extremity of the wire which tends to attach itself to the wall of the vessel; this resistance is quite low compared with the widening force applied to the vessel in the stenosed region.
The object of this invention is to avoid the disadvantages mentioned above by creating a prosthesis which can be manufactured at little cost and which applies a relatively strong force in the region of the conduit or vessel which has to be widened and which presents a low risk of snaking after it has been implanted.
To this end, an initial aspect of the invention concerns a prosthesis of the type described above, characterised in that it comprises several segments of elastic wire having a configuration of helical spirals where the direction of the spirals is the same for all the segments of wire, and in that outside the zones of extremity of the prosthesis, the segments of wire are intercalated without crossing in order to form the said substantially cylindrical shape.
In this way it is possible to select the number of segments of wire for the prosthesis in order to confer upon it the desired mechanical characteristics and in particular sufficient expansion forces without its design being costly, as all the segments of wire are similar and do not need to be attached to one another. If necessary, each segment of wire may have a free extremity at each extremity of the prosthesis, so that the longitudinal attachment of the prosthesis in the conduit is improved. In other cases the segments of wire may be interlinked at each extremity of the prosthesis, although they may still form several points of attachment at each extremity.
In a particularly advantageous embodiment the spirals o
REFERENCES:
patent: 4300244 (1981-11-01), Bokros
patent: 5171262 (1992-12-01), MacGregor
patent: 5575818 (1996-11-01), Pinchuk
Black John M.
Isabella David
Microfil Industries S.A.
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