US RE39335 E1
A tubular graft/stent includes a tubular sheath (10) having at intervals along its length a plurality of ring-like rigid members (11), which are attached to the sheath around their respective circumferences and are made of a shape memory material, so that when the members (11) change shape the sheath (10) adopts a new cross section in conformity with them along its whole length. The members may be discontinuous to allow the adoption of a contracted shape in the martensitic phase and an expanded shape in the austenitic phase. A graft may also have a side tube (14) which can be inverted so as to be housed within the sheath.
1. A tubular graft/stent comprising:
a tubular sheath that is graft/stent; and
an integral branch tube having an end fixed to the tubular sheath at an opening in a side wall of the tubular sheath, wherein the branch tube is a graft/stent along its entire length, the branch tube comprising a plurality of rigid ring-like members being of progressively smaller size in the direction progressively away from the tubular sheath, and the branch tube being sufficiently flexible to be fully inverted along its entire length so as to be fully housed within the tubular sheath during an insertion operation in a human or animal body, and to be redeployed as a branch after insertion operation.
2. A tubular graft/stent according to
3. A tubular graft/stent according to
4. A tubular graft/stent according to
5. A tubular graft/stent according to
6. A tubular graft/stent according to
7. A tubular graft/stent according to
8. A tubular graft/stent according to
9. A tubular graft/stent according to
10. A tubular graft/stent according to
11. A method of inserting a graft/stent having a tubular sheath which is a graft/stent and an attached integral branch tube that is also a graft/stent along its entire length, the method comprising:
fully inverting said branch tube along its entire length to place said branch tube fully within said tubular sheath for insertion in a body;
inserting said graft/stent into said body; and
pulling said branch tube out of said tubular sheath in said body, wherein pulling said tubular branch tube re-inverts said branch tube and leaves said branch tube attached to said tubular sheath.
12. The method of
engaging a cord on a distal end of said branch tube; and
pulling said cord to deploy said branch tube within said body.
13. The method of
14. The method of
15. The method of
16. The method of
This application is a continuation of International (PCT) Patent Application Patent Application PCT/GB96/02212 filed 6 Sep. 1996.
This invention relates to a graft/stent system for use in human or animal surgery. One example of this type of graft/stent is disclosed in EP 0326426A, which describes an artificial blood vessel in the form of a tubular sheath having a ring-like member located at each of its ends. Another example, disclosed in EP 0461791A, is an aortic graft with one of its tubular ends divided into two branches.
According to an aspect of the present invention, there is provided a tubular graft/stent as specified in claim 1.
According to another aspect of the present invention, there is provided a tubular graft/stent as specified in claim 9.
The invention proposes a medical tubular graft stent which comprises a tubular sheath having at intervals along its length a plurality of ring-like members, wherein said members are attached to the sheath around their respective circumferences and are made of a shape memory material, so that when said members change shape, the sheath adopts a new cross-section in conformity with them along its whole length.
Preferably, this provides a compliant tubular sheath, into which a series of open rings are integrated. The rings act as rigidising members and are capable of being radially compressed by mechanical forces in the martensitic phase so as to reduce the diameter, and of then returning in the austenitic phase to a memorised, larger diameter by a thermal effect.
In a further aspect, the invention proposes a tubular graft comprising a tubular sheath having a branch tube which is sufficiently flexible to be inverted so as to be housed within the sheath during an insertion operation in a human or animal body, and to be redeployed as a branch after said operation. The sheath and/or the branch tube may employ annular rigid members of a shape memory material, as explained above. In all cases, the members are preferably discontinuous, e.g. a ring with a break so as to facilitate compression and re-expansion.
In order that the invention shall be clearly understood, several exemplary embodiments thereof will now be described with references to the accompanying drawings, in which:
An exemplary general arrangement is shown in
The compliant tube 10 can be generated by fabrication methods, or an “open” tube could be made by using flat sheets whose shape is established by the shape memory alloy rings. The tubular form might also use sheets of dissimilar materials. The cube may be produced in continuous lengths and cut off as needed.
The shape memory alloy rings can be retained by casting a suitable compliant material around the ring, by adhesive bonding, sewing or by generating a series of pockets within which the rings may be held by welding, sewing, mechanical fixation or adhesive bonding. In the embodiment shown, the rings 11 are in a single piece, but could be in two or more accurate sections.
The device described is suitable for a number of minimally invasive surgical techniques or may substantially reduce trauma associated with the introduction of implanted medical devices within a living organism. A single, plain tube (known as a tubular graft) with integrated expandable contractible rings (known as stents) as described is inserted into a occluded fluid carrying vessel or a vessel that has a structure. When appropriately positioned via the catheter, heat from the human body (or a heated fluid introduced) will cause the latent geometry of the shape memory alloy to be re-called. Under these circumstances the rings will expand to a pre-determined position as seen in
This device may find applications in surgical repair or maintenance procedure for the human body or other animal species. Gastro-intestinal system connections, oesophageal cancer, aneurysms, coronary by-pass connections and other vascular by-pass or shunt procedures could employ the stent/graft device.
The dynamic properties of the rings expand the graft/stent within the body to effect an opening of constricted or occluded vessel. The outer graft stent would assist in preventing occlusive material from once again entering the vessel. The complaint sheath will also exclude tumorous growth, maintaining luminal patency.
The tubular graft with in integrated shape memory alloy rings may be a simple tube-like form as described or could be a manifold system having a main tube 13 from which one or substantial numbers of connections 14 may be made, as seen in
A graft of the type described might be simply bifurcated or may have numerous smaller or larger tubes of similar construction, attached to the main tube body. The branches attached to the body of the device may have a similar shape memory alloy ring configuration. Each branch 14 can be inverted so as to fit within the main tube. Under these conditions, the whole assembly can be radially compressed, the manifold system now appearing as a single tube for initial insertion via a catheter. A suitable cord to 15 is connected to the inverted branch enabling it/them to be re-inverted by pulling the cord, as shown in FIG. 5. Preferably, the rings nearer to the main tube are largest and are progressively smaller towards the end, to allow the inversion to occur.
When warmed, the shape memory alloy rings will expand to a pre-determined position. If employed in a surgical repair, forces exerted by the shape memory alloy rings will be of sufficient magnitude to open an occluded vessel thus enabling appropriate fluid flows to continue.
The compliant outer sheath would enable radial or axial movement of the vessel to occur. This might be the case if the stent/graft were positioned in an osophagus that had radially disposed tumours. Peristalsis effects used to assist transportation of food and liquids in the human body would need to be maintained in oesophageal dysfunctional problems. The covered or sheathed stent system would exclude tumorous in-growth and still enable peristalsis to occur.
The compliant could be 0.050 mm polyurethane, polyester or polythene. The shape memory material may be a metal alloy with this property, or alternatively certain mouldable plastics materials such as homopolymers of lactide or glycolide, or copolymers of lactide and glycolide.
The invention is also considered to include a graft with a side tube which does not employ stents of shape memory material. Thus in addition to shape memory materials, the ring-like rigid members 11 can also be fabricated from elastic materials such as stainless steel or the super-elastic forms of nickel-titanium alloys. In this case the implant is constrained within in outer sheath after whose removal the graft will expand to adopt its final shape.
In the embodiment of
The overlap 20 can be designed to have one of three properties:
1) The overlap can be left to slide freely over itself, permitting the graft assembly to be contracted by muscles in the vessel or to allow pressure pulses in arterial blood, arising from the heartbeat, to be transmitted to the artery wall. The action of pressure pulses is involved in maintaining the vasomotor tone in blood vessels.
The mating surfaces of the overlapping part of the sheath can be coated to reduce friction and wear with materials such as PTFE or diamond-like coatings.
2) As shown in
3) As shown in
The ratchet-like mechanism can be incorporated onto the walls of the sheath by moulding, machining, or attaching ratchet components. Alternatively, the ratchet mechanism can be formed in the ends of the ring-like member and can be either permanently present or deployed by the action of thermal memory.
An implant can be assembled which incorporates a combination of all three types of overlap mechanism so that for instance, the distal ends of the graft can use ratchet expanding rings to lock the device in place, while the main body of the graft uses alternating sliding and diameter-limiting rings to allow limited transmission of pulsatility while restricting the maximum diameter of the graft.
The benefit of the graft can be increased by incorporating coatings onto its inner or outer surfaces. These coatings can be biomimetics such as phosphorylcholines and proteins, organic biocompatibles such as hydrophilic plastics and inorganic coatings, such as diamond-like carbon. The coatings can be used to be thrombus-resistant, encrustation resistant or to promote cellular ingrowth. In addition, the coatings can be used to release locally acting pharmacological agents and they can be multiply layered.
Deployment of the inverted segment 14 can be achieved by adding a short handle, tab or strip to the distal end of the side branch which can be engaged by a snare, forceps or similar engagement means.