Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Patent
1998-06-29
1999-10-19
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
623 12, 606198, A61F 206
Patent
active
059680938
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a stent, particularly a coronary stent, as an intraluminal expansion element of the type mentioned in the generic part of claim 1, and to methods of making such a stent.
An expandable intraluminal element with at least one thin-walled, tubular member (hereinafter referred to as a stent) is known from European patents EP-B1 0 364 787 and EP-B1 335 341. The generated surface of the stent is in the form of an open network and has apertures bounded by strap-like elements of low material thickness, extending in a straight line in the axial and peripheral directions. The strap-like elements comprise the remaining wall of the tube, from which the material in the area of the apertures has been removed.
During an operation such stents are expanded by the action of outwardly directed forces, by means of a tubular dilator working with compressed gas. The stent retains its tubular shape in spite of deformation and expands the vessel which has been narrrowed by deposits.
The known stent has the drawback that expansion through deformation of the axially extending strap-like elements can only take place to a limited extent, as relatively narrow limits are set to a change in the shape of the individual strap-like elements of the stent. These limits depend on the material tensions which accompany deformation, and which may lead to breakage of one or more of the strap-like elements forming the network if the deformation becomes too great.
For safety reasons therefore deformation must normally be kept far below a possible danger range, as breakage of a strap would cause its free ends in the vicinity of the breakage point to project into the interior of the vessel provided with the stent. The concomitant danger of restenosis formation would not only put the success of the operation into question but also endanger the patient's life.
Based on the defects of prior art, the problem of the invention is to provide an expandable stent of the above type, which can be expanded as safely as possible--and thus without any risk of breakage in the vicinity of the strap-like element through tensile overloading. Shortening of the stent must also be avoided.
The problem is solved by the characterising features of claim 1.
The invention includes the technical teaching that, in the case of fragile tubular elements which are made of suitable materials, which have network-like structures and which are subject to deformation in use, critical loads on the material or even breakages of the material can be avoided, if the maximum tensions occurring in areas subject to increased deformation are limited from the outset by the design. Shortening of the stent during its expansion may also be avoided if, in addition, pairs of transversely expandable elements are directly joined at the ends longitudinally of the stent, each of the two expandable elements, in the form of a flattened ring element made up of straps, being joined transversely by a strap-like element to another transversely expandable element, which is itself not directly joined at the end to another expandable element, which is in turn joined by a strap-like element to one of the first-mentioned, transversely expandable elements, the strap-like elements each being inclined to the transverse direction at an angle such that this angle is reduced on expansion of the stent, and the non-joined adjacent ends of transversely expandable elements thus move away from each other.
This applies particularly if the strap-like elements in the non-expanded stent are at an inclination of substantially 45.degree. to the transverse direction.
Through the process of stretching the expandable elements transversely of the stent, which occurs simultaneously with the expansion of the stent, and through the alignment of the inclined joining elements in the transverse direction, the non-joined groups of expandable elements are displaced relative to each other, in such a way that that movement compensates for the shortening of the stent by extending the flat shapes of the expandable elements i
REFERENCES:
patent: 5449373 (1995-09-01), Pinchasik et al.
patent: 5591197 (1997-01-01), Orth
patent: 5810872 (1998-09-01), Kanesaka et al.
patent: 5879381 (1999-03-01), Moriuchi et al.
Biotronik Mess-and Therapiegerate GmbH & Co.
Jackson Suzette
Spencer George H.
Wells Ashley J.
Willse David H.
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