GB2270264A

GB2270264A - Palliative stent and insertion device therefor

Info

Publication number: GB2270264A
Application number: GB9317993A
Authority: GB
Inventors: Julian Garth Ellis; Peter William Butcher
Original assignee: ELLIS DEV Ltd
Current assignee: ELLIS DEV Ltd
Priority date: 1992-09-02
Filing date: 1993-08-31
Publication date: 1994-03-09
Anticipated expiration: 2013-08-31
Also published as: GB9317993D0; GB2270264B

Abstract

The stent, which is self-expanding, is in the form of a tube which can be compressed for insertion into the human or animal body to relieve blocking of the oesophagus or other hollow viscera by tumours or other disorders. It is formed as a single or double conical helix or as a straight tube with cut slots allowing the tube to expand to different diameters along its length, so holding itself in place. A knitted or other tube is used to hold the stent in its compressed shape for insertion. A ratchet system may be provided on one or both surfaces of the collapsed tube so that once extended it will not collapse again. <IMAGE>

Description

PALLIATIVE STENT AND INSERTION DEVICE This invention relates to devices for the palliation of strictures of the oesophagus and other hollow viscera.

A number of hollow viscera are susceptible to narrowing or blockage, often by the growth of malignant or benign tumours. The present invention is intended to improve the condition of patients suffering from such problems. For example, the management of patients suffering from dysphagia (inability to swallow) caused by malignant oesophageal tumours has long been difficult. Usually the patient starts off by being unable to swallow solid food, and then, as the narrowing due to the tumour gets worse the patient loses the ability to swallow liquids and then eventually the ability to swallow his own saliva. The treatment of radiotherapy which can be applied to one type of tumour (squamous carcinomas) often makes the situation worse for a short while, because before the tumour begins to respond there is a lot of tissue swelling associated with the high dose of X-rays.

The conventional approach to this type of problem is to palliate the swallowing difficulty by inserting a medical prosthesis in the form of a flanged circular tube which sits across the narrowed area and keeps the lumen open. A popular device is known as The Atkinson Tube or the Nottingham Tube as described in British Patent GB2069339. However this approach has a number of problems. Some tubes fall out of the narrowed region. In other cases either the bougie used to extend the oesophagus prior to inserting the device, or the device itself, can split the gullet with disastrous consequences. It is therefore desirable to reduce or eliminate the need for such a device.

In most cases the patient has to have a general anaesthetic to have the tube inserted and this in itself can be a cause of problems, particularly in the elderly.

A number of self-expanding stainless steel mesh devices have been devised, notably for other obstructions of hollow viscera, such as the bile duct or arteries.

There are limitations to this technique, one being that, after being allowed to expand, the foraminous nature of the mesh is retained. If the tumour continues to grow, the duct may once more become blocked, requiring a further operation.

The present device is designed to overcome these difficulties. It consists of a self-expanding solid walled tube. One embodiment of the device is most easily described as a substantial circular cross-section tube which has a longitudinal slit, so that one longitudinal edge can be arranged so that it comes inside the wall of the tube on the opposite side of the cut. The tube may be reduced in diameter by the use of forces that cause the inner wall of the tube to slide internally against the outer wall. This can be seen by referring to Figure 1. Alternatively the slit may be in a helical form, so that the appearance of the tube is such that it may have the form of a strip of material wound into a helical spring tube whereby succeeding layers of the helix overlap the previous layer (Figure 2). The tube may be reduced in diameter by the application of torsional forces.The diameter of the tube is reduced to facilitate Insertion of the tube into the lumen of the section of the oesophagus or other hollow viscus which is partially or completely strictured.

In order that the device is retained in a collapsed form during insertion of the device, it may be enclosed in an inserter, which may be in the form of a tube. The inserter may be "rigid", perhaps as a paper or cardboard tube such as is used for the insertion of a tampon, or it may be made from a sheet material such as polythene sheeting, or it may made from an elastomeric material or it may be soluble. The device might be inhibited from expanding by cooling to a low temperature which will reduce the elastic recovery characteristics of the material from which the stent is formed. An example of a soluble device is a knitted tube of polyvinyl acetate or polyvinyl alcohol or alginate which will melt or dissolve away after insertion. A knitted insertion tube may be removed slowly by unroving the knitting, by pulling at one end of the knitted fabric.An inserter may alternatively be in the form of an gripping device external to the prosthesis in its reduced diameter. When the gripper is withdrawn by pushing the gripper away from the exterior of the device, the device expands. The insertion assembly may then be withdrawn through the lumen of the expanded tube.

The device may be assisted in its expansion by the application of a force such as the expansion of an olive, the force usually being transmitted through part of the insertion instrumentation.

The device may be made from a number of raw materials which are non-toxic and are sufficiently resilient to withstand the particular conditions encountered within the body. Thus if used in the oesophagus the material must be resistant to the stomach acids, and a polyester based material may be satisfactory, but in the bile duct the material will need to be resistant to the bile salts and the alkaline resistant properties of nylon are more suitable. Other materials may be found useful, and might include carbon fibre, polyamide, polyester, glass, aramid, cotton, viscose, natural or synthetic elastomers, derivatives of polyvinyl, ceramic, polyurethane, polyolefin, polycarbamide, steel, titanium, beryllium-copper alloy, or other material alone or in combination.

The exposed edges of stents may be chamfered on the inside and/or the outside edges so as to minimise entrapment internally and tissue damage externally. The stents may be made including a radio-opaque material so as to facilitate its positioning within the body using x-ray or other imaging techniques.

One or both surfaces of the collapsed tube may be arranged so that the device has a ratchet system, so that once it has extended, the tube will not collapse again. A tendency to collapse may be induced by movement of the patient, or by further growth of the tumour.

Specific embodiments of the invention will now be described with reference to the accompanying drawings in which:-: Figure 1 is a plan view of a tube according to the invention Figure 2 is a view of an alternative embodiment of a tube according to the invention, the tube shown in the diagram having been flattened out.

Figure 3 is a side elevation of an alternative embodiment of a tube according to the invention.

Figure 4 is a view similar to that of figure 1 of an alternative embodiment according to the invention.

Example 1 A tube is manufactured from carbon fibres impregnated with epoxy resin, the length of the tube being 10 cms approximately, and the outer diameter 22 mm. The wall thickness of the tube is less than 1 mm. A longitudinal slit is made in the tube, so that it can be compressed when one side of the cut is allowed to slide under the opposing side of the slit, as shown in Fig 1. Transverse slits may be placed in the tube at I cm intervals along the tube, the slits covering 3/4 of the diameter of the tube, leaving a spine of 1/4 the circumference of the tube diagonally opposite the longitudinal slit. This is illustrated diagrammatically in Fig 2.

The completed tube is compressed circumferentially, and may be encapsulated within a net manufactured by knitting using a poly(vinyl acetate) yarn. The assembly is inserted within the oesophagus of the patient, and the enclosing net dissolved with a warm water lavage. Removal of the capsule permits the tube to spring open, and the outward pressure of the tube gently presses the tumour outwards, so that after an interval the lumen of the oesophagus is enlarged by the device. If a diameter of 15mm or greater is maintained the passing of fluids and even solid foods through the oesophagus and stent to the stomach may resume. Slits (a) are included the stent allowing the stent to expand more above and below the constriction, so that its cross sectional area may become greater than at the point where the tumour is largest, giving the device an approximately double conical shape.This shape will hold the stent more securely in place, minimising risk of downward displacement during swallowing or upward displacement during patient movement or if a violent reflux occurs. Ratchets (b) in Fig 3 may be included in the inner wall of the device to prevent collapse of the tube after insertion.

Example 2 Sheet polyester material preferably between 0.3 mm and 2.0 mm thick is cut into a strip approximately 30 mm wide. It is then helically wound around a former, with each layer overlapping the previous layer. The tube is placed within an oven at 1500C for up to 3 minutes to heat-set the polyester in the helical configuration as shown in Fig 4.

After cooling, the completed tube is twisted to reduce the diameter of the tube, and may be inserted in a manner similar to that described in Example 1 above. By changing the shape of the strip from which the stent is formed it is possible to cause the ends of the helical tube to be flared outwards so as to contribute to holding the stent into position in the oesophagus. The upper or proximal end of the device has ffiis funnel like formation to assist in the direction of food through the tube and to avoid the likelihood of food becoming lodged above the tube.

Example 3 The palliative stent is encased in a flexible plastic tube which holds it in its compressed state. The outer sleeve is fed through the centre of the stent, passing through itself as illustrated in Fig 5. When the device and sleeve is placed in position the sleeve may be removed by pulling it through the centre of the stent as shown in Fig 6 and Fig 7, leaving the stent in situ.

Example 4 The tube in its compressed form is enclosed in a knitted tube composed of a multifilament or monofilament yarn as shown in Fig 8. When the tube has been placed in situ the sleeve may be steadily unroved by pulling on an attached tag (c) or other end marking device as shown in Fig 9. The last length of the yarn may be marked with a coloured indication so as to confirm that all the sleeve has been withdrawn, as shown in Fig 10.

These examples are provided by way of illustration only: there are other applications for this invention including the palliation of obstructions in humans and animals, including obstructions of the blood vessels and the bile duct.

Claims

1. A stent for implantation within the human or animal body, comprising a tube which may be placed within the body whilst in a reduced diameter, and when in place allowed to expand.

2. A stent, as described in Claim 1 where the stent is in the form of a rigid tube, with a single longitudinal slit, where one edge of the slit tube may be allowed to slide within the outer diameter of the tube, so allowing the diameter to be reduced.

3. A stent, as described in claim 1 and claim 2 where there are extra slits in the tube approximately at right angles to the longitudinal slit, allowing the expanded diameter of the stent to be greater in some parts of its length than others.

4. A self-expanding stent as claimed in claim 1 which is in the form of a helix

5. A self-expanding stent as claimed in claims 1 and 4 which expands to have a cone at one or both ends.

6. A self-expanding stent as claimed in Claims 1, 4 and 5 which is formed from a strip material with one or more of the layers comprising the strip overlapping each other.

7. A self-expanding stent as described in claims 1 to 6 whereby one or more surfaces are shaped to form a ratchet to prevent the reduction of the diameter of the stent after it has been allowed to expand.

8. A stent as described in claims 1 to 7 whereby the stent expands by the application of forces applied externally to the device after insertion within the body.

9. An insertion device for a self-expanding stent as claimed in claims I to 8 comprising a tube made from a textile or sheet material to contain the compressed stent, which tube can be pulled off, dissolved or unroved to allow the stent to self-expand.

10. A self-expanding stent as claimed in any of the claims 1 to 8 which is formed from a radio-opaque material.

11. A self-expanding stent as claimed in any of the claims 1 to 8 which is formed from a polyester polymer or co-polymer.

12. A self-expanding stent as claimed in any of the claims 1 to 8 which is formed from a nylon polymer or co-polymer.

13. A self-expanding stent as claimed in any of the claims I to 8 which is formed from a metal or metal alloy.

14. A self-expanding stent as claimed in any of the claims 1 to 8 which is formed from a metal or metal alloy with a coating of a polymeric material.

15. A stent and insertion system as claimed in claims I to 14, substantially as herein described.