Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reissue Patent
1997-04-10
2003-04-22
Milano, Michael J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001110, C623S001310, C623S001340, C623S001380, C623S001420, C623S001500, C606S194000
Reissue Patent
active
RE038091
ABSTRACT:
The invention relates to a device with a prosthesis implantable in the body of a patient, especially in a blood vessel or other body cavity, and designed as a hollow body. The prosthesis is compressible against the action of restoring spring forces down to a cross section which is reduced relative to an (expanded) operating position. The prosthesis may be also automatically expanding to a cross section corresponding to the operating position following removal of the restraining forces effecting the compression.
BACKGROUND
Devices of this type are known, and serve for percutaneous implantation of vascular prostheses in particular. Prostheses which are introducible percutaneously and expand in the lumen are either expandable mechanically by means of a known balloon catheter from a small radius to the larger radius to hold a vascular lumen open, or they expand automatically following previous compression prior to implantation by spring force, due to spring pretensioning generated during compression.
Various systems are already known for inserting self-expanding vascular prostheses which are under spring force into the body of a patient, and to implant or anchor them in the vessel by removing the restraining force.
The commonest method, which is described in EP-A-0 183 372, consists in compressing an endoprosthesis, made in the form of a tubular hollow body, to a reduced cross section and then pushing it in the compressed state, using a so-called pusher, through a catheter previously introduced into a vessel until they are in the correct position in the vessel. However, this system suffers from the disadvantage that a considerable expenditure of force is required to push the prosthesis through the catheter because its displacement is counteracted by considerable frictional forces.
Another method (not confirmable by publications) consists in retracting a sheath covering the endoprosthesis and holding the latter together, in the vessel at the implantation site. Here again there is the disadvantage that high frictional forces must be overcome. Moreover, the tube system is quite rigid because of the sheath covering the prosthesis, making introduction into a vessel through curves very difficult.
In another system (U.S. Pat. No. 4,732,152) a woven and spring-tensioned prosthesis is held together in the compressed state by a double sheath, sealed at the distal end. This sheath is retracted from the folded prosthesis like a stocking being pulled off the foot of a wearer. To reduce the friction which then occurs, liquid can be introduced between the two sheath layers. This system, which initially appears elegant because of the reduction of the frictional resistances, is extremely cumbersome to handle however and requires two persons to operate.
On the other hand, the invention is intended to provide an especially simple and readily operable device for implantation of a prosthesis made in the form of a hollow body, with a vascular prosthesis envisioned in particular.
SUMMARY OF THE INVENTION
This goal is achieved by virtue of the fact that in the device according to the preamble of claim
1
the prosthesis is surrounded by a sheath which can be pulled off it, said sheath consisting of at least one through thread, and compressed to a reduced cross section, and by the fact that at least one drawstring is provided, said drawstring being laid so it extends away from the sheath holding the prosthesis in its radially compressed state, the thread forming said sheath being retractable.
In the invention, the prosthesis is therefore held in its radially compressed state by means of this external sheath and reaches its intended expansion position only after removal of this sheath, which is designed to be pulled off, thanks to the pretensioning force generated during compression.
The sheath can be in particular a meshwork produced by crocheting, knotting, tying, or other methods of mesh formation.
Advantageously the prosthesis, held by the sheath which can be pulled off in the radially compressed state, can be received on a probe, or a flexible guide wire, and advanced thereon. In one design of a device of this kind, implantation is accomplished by introducing the guide wire in known fashion into a vessel and then advancing the prosthesis, held in a radially compressed state, along the guide wire, said wire being advanced for example by means of a sleeve likewise advanced over the guide wire and engaging the end of the prosthesis away from the insertion end thereof.
Another improvement, on the other hand, provides that the prosthesis, held in the radially compressed state by the sheath which can be pulled off, is held in an axially fixed position on the insertion end of a probe. Specifically, this probe can be a catheter advanced over a guide wire.
Even with the axially fixed mounting of the prosthesis, held in the compressed state, on the insertion end of a probe or a catheter, implantation takes place in simple fashion with the probe or catheter being advanced together with the prosthesis mounted on the insertion end, for example under the control of x-rays, up to the implantation site, and then by pulling off the sheath, made for example as a covering meshwork, the prosthesis is exposed and implanted in the proper location by its automatic expansion.
In mounting the prostheses on the insertion ends of probes or catheters, it has been found to be advantageous for the prosthesis to be mounted on a non-slip substrate surrounding the probe or catheter, so that undesired slipping and sliding during the release of the thread material forming the meshwork cannot occur.
Advantageously, the self-expanding prosthesis can be a tube made by crocheting, knitting, or other methods of mesh formation, composed of metal and plastic thread material with good tissue compatibility, said tube being compressible radially against the action of pretensioning forces and automatically expanding into its operating position after the restraining forces are removed, and then remaining in the expanded position.
In the case of the prosthesis designed as meshwork, according to a logical improvement, successive rows of mesh can be made alternately of resorbable thread material and non-resorbable thread material. This means that within a predetermined period of time after implantation, the resorbable thread material will be dissolved and the prosthesis parts, then consisting only of non-resorbable thread material, will remain in the patient's body. These remaining components form circumferential rings of successive open loops. This avoids thread intersections which could exert undesirable shearing forces on surrounding and growing tissue coatings.
In the improvement just described, drugs can also be embedded in the resorbable thread material so that the prosthesis constitutes a drug deposit which gradually dispenses drugs during the gradual dissolution of the resorbable thread material.
An especially advantageous improvement on the invention is characterized by making the tubular meshwork holding the prosthesis in the compressed state in such a way that the mesh changes direction after each wrap around the prosthesis and when successive meshes are pulled off, the thread sections forming the latter separate alternately to the right and left from the prosthesis.
The advantage of this improvement consists in the fact that the mesh wrapped successively and alternately left and right around the prosthesis can be pulled off without the thread material becoming wrapped around the probe holding the prosthesis or a catheter serving as such, or undergoing twisting, which would make further retraction of the thread material more difficult because of the resultant friction.
It has also been found to be advantageous in the improvement described above for the loops or knots of the mesh wrapped successively around the prosthesis and capable of being pulled off, to be located sequentially with respect to one another or in a row running essentially axially.
Another important improvement on the invention provides for the drawstring to extend aw
Boston Scientific Corporation
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Milano Michael J.
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