Patent Application
20090177288
The present invention relates to stents and particularly to the treatment of diseases in the urethra of men.
Almost all available stents are so called permanent stents e.g. they are designed to be inserted in occluded vessels and organs to permanently support the vessel and keep it open.
The majority of the permanent stents are cylindrical and expandable from a small diameter to facilitate insertion through a small access. In general such stents have the openings in the walls to enhance overgrowth and ingrowth of tissue. Therefore the removal of expanded stents designed for permanent implantation is difficult and risky.
The golden standard for the treatment of benign prostate hyperplasia, BPH is transurethral resection TURP, which is surgery and means several days of hospitalisation and often results in severe side effects. It also means carrying an indwelling catheter during weeks and sometimes more.
Thermotherapy, such as heat treatment of the prostate with microwaves, interstitial radio frequency and hot balloons are interesting alternatives to TURP because it is less invasive and have less side effects. It is accomplished by heating the prostate to temperatures above 50-60°, which leads to decrease in the swelling of the prostate, as the prostatic gland.
A great problem connected to different kind of thermotherapy is however that the prostatic gland temporary also swells in response to the burn so that at higher temperatures and more efficient treatment there is a great risk for acute blockage of the urethra. A similar reaction happens at irradiation of prostatic cancer.
During the healing process of the prostate and the urethra the damaged tissue will partly be reabsorbed and partly slough off. The healing takes several weeks and because of the acute swelling it is therefore necessary to catheterise the patient during several weeks, which is a drawback to this kind of therapy. A long catheterisation time means not only a discomfort for the patient but also a risk for infections. Thermotherapy will therefore hardly replace TURP unless the catheterisation can be reduced to a few days or totally replaced.
It is therefore a need for a temporary stent to keep the urethra open allowing the patient to urinate during the healing. Such a stent must have an appropriate length and be precisely placed between the bladder neck and the outer sphincter to eliminate the risk for blockage by the swelling prostate on unsupported parts of the urethra or incontinence if a part of the stent protrudes into the sphincter. Such a temporary stent must also be easy to take out after the healing or in case of dislocation.
A commonly used material for stents is a so called memory or recovery metal such as Nitinol®, which is an alloy based on nickel and titanium. Such alloys undergo a transition between a strong austenitic state and a soft martensitic state at certain temperatures. They have been subject to a great deal of interest due to the extraordinary “memory” they possess.
An expanded memorized shape can be set into such recovery metals by heating them while they are constrained in the desired expanded configuration. The forming temperature for setting the initial austenitic shape is typically around 500° C. After cooling the alloy to its martensite state it can be mechanically deformed to a second, smaller configuration, which is suitable for introduction in the organ to be stented. After placement is the alloy heated to its transition temperature, and expands to its austenite, strong state and recover its initial memorized configuration.
For replacement of indwelling catheters in urology particularily for the treatment of BPH, a stainless steel coil was introduced by Fabian 1980 followed by several similar stents for temporary use such as Prostakath™. A drawback with this type of non-expandable stents is that they often migrate.
Memokath®, Engineers and Doctors, Denmark was developed to overcome the shortcomings of Prostakath™. It is a cylindrical coil stent made up of a single wire of a Nitinol® alloy. The material has a transition temperature of about 45° C. and becomes soft at 10° C. Because of the memory capability the stent is given a primary shape where one or more segments has a diameter which is considerably larger than the rest of the stent and a secondary shape where the segment with the larger diameter has been reduced to the same smaller diameter as the rest of the stent, WO 93/13824 and “From Prostakath® to Memokath®”, Nordling et al. in “Stenting the Urinary System”, pp. 285-290, Oxford Isis Medical Medica Ltd, 1998.
In the commercial configuration the Memokath® stent has in its cylindrical non-expanded secondary shape an inner diameter of 6.7 mm and an outer diameter of 8.0 mm. In the primary shape is only the proximal part adjacent the sphincter shape expanded to a bell shape with tightly coiled wires. The expansion is activated by the injection of water at 50 to 60° C., expanding the proximal part to an outer diameter of about 13 mm locking the stent in the urethra. The expansion is fast and starts by the unwinding of the proximal coil end and then coil by coil successively until the expansion is accomplished. The expansion to 13 mm is only for locking the stent to reduce the risk for migration. The inner diameter of 6.7 mm of the cylindrical part of the stent is sufficient to obtain a good flow.
The Memokath® stent mainly used as a stent for long term placement can be taken out by using an endoscope with graspers. The endoscope has to be introduced via the meatus through the external sphincter. Ice-water is then injected softening the stent material allowing the stent coil to be partly stretched. By grasping the proximal stent end inside the sphincter, which sometimes can be difficult, can the stent then be taken out as a partly stretched wire by pulling the endoscope.
There is another stent, Horizon™ based on Nitinol for implantation in the prostatic urethra and where the fixation also is based on a bell shaped proximal part of the stent with the larger opening adjacent to the sphincter. In this case the transition temperature is low, about 37° C., and the expansion is performed by the heat from the body.
Stents like Memokath™, Horizon™ have less tendency to migrate compared to non-expanding stents if they are implanted to open up obstructions in the urethra. Clinical trials have showed however that such stents are not suitable to use as replacement for an indwelling catheter after thermo-therapy such as the Wallterm™ procedure as they show high migration rates of the stents into the bladder.
A reason seems to be that the thermal treatment first causes the urethra to widen before the prostatic gland starts to swell and thereby shrinks the urethra, which can create obstruction of the same type as described earlier.
If a stent of for ex type Memokath™ or Horizon™ is implanted in the widened urethra will the expanded, large bell shaped opening create strong outward forces of the sphincteric tissue counteracting the closing of it. If the urethra is widened the non-expanded part becomes loose and can be rejected into the bladder by the movement of the sphincter.
It is thus an object of the present invention to produce a stent which can be precisely implanted in a diseased organ and have a low risk form migration, which is easy to implant, and to later remove in the case of a temporary stent, and which in general at least to some extent overcomes the disadvantages described above in relation to known stents.
Throughout this application a diseased organ may be e.g. an oesophagus being compressed due to a tumour, or obstructions in the urethra caused by BPH, temporary swelling of the prostatic gland after thermotherapy, irradiation or strictures.
The above object is achieved according to one aspect of the present inventive concept by means of a stent for use in a tubular organ of a body, comprising a first part to be positioned in a diseased part of the organ and acting as a stentbody therein, and a second part to be positioned in a non-diseased part of the organ and acting as an anchoring element, said two parts being designed as tubular members interconnected at the ends facing one another by a flexible, axially rigid connecting part, at least said second part having memorized therein a capacity to expand radially after an increase in temperature, thereby providing anchorage of the stentbody at a determined distance away from the diseased part of the organ. What is achieved is a stent which has a distinct stenting part, the first part, to keep the diseased organ open, and a distinct anchoring element, the second part, to anchor the stent in place in the non-diseased part. This anchoring works against migrations in both axial directions of the stent. The axially rigid connecting part is also serving this purpose of keeping the first part away from the surrounding organs, since the axial rigidity thereof transfers the anchoring from the second part to the first part. This way the first part is kept in position and is prohibited from migrating in either direction. However, the connecting part is not rigid in the transversal direction since it may need to follow the axial direction if the organ is not straight, or the movements of the organ.
Furthermore, by separating the stenting function and the anchoring function, each part may be thoroughly adapted to the circumstances under which it operates, i.e. each part may be adapted to restrictions in diseased or non-diseased parts or organs. For instance may the first part be given a diameter suitable to keep the diseased organ open, and the second part given another diameter for the anchoring function. A non-diseased part is in general less sensitive to extraordinary circumstances in comparison to a diseased part. Still, the unexpanded stent may be given the same features such as diameter all along. According to an embodiment of the present inventive concept the stent may be used in the urethra, wherein said first part is adapted to be positioned in the prostatic urethra, and said second part is adapted to be positioned in the bulbar urethra on the opposite side of a sphincter, wherein said connecting part has a length equal to or larger than the axial extension of the sphincter. What is achieved is a stent which has a distinct stenting part, the first part, to keep the diseased prostatic urethra open to allow a good urine flow, and a distinct anchoring element, the second part, to anchor the stent in place. This anchoring works in two directions, both anchoring against migration of the first part into the bladder, but also against migration towards the sphincter. The axially rigid connecting part is also serving the latter purpose, since the axial rigidity thereof transfers the anchoring of the second part to the first part. The anchoring against and the hindrance of migration towards the sphincter of the stent is in this embodiment an advantage since any hindrance of the normal movements of the sphincter may be inconvenient for the patient.
According to an embodiment of the present inventive concept at least said second part is in its non-expanded state designed as a wound tubular spiral. The second part may thus easily and cheaply be produced and also easily made expandable.
According to an embodiment of the present inventive concept, in the expanded state of said stent, said second part at least at one portion along its axial length has a diameter that is larger than the diameter of the first part. In general, a diseased part is more vulnerable for irritation than a non-diseased part, and even though the stent is implanted in a patient for treatment of a disease, it is normally advantageous for the diameter of the first part to be smaller than of at least portions of the second part. Further, a diseased and treated part should not be expanded further, it should be kept open for a good urine flow, but it has been found that anchoring may still be achieved in non-diseased parts. According to an embodiment of the present inventive concept, in the expanded state of said stent, the second part at least at one portion along its axial length has a diameter that is at least 1.5 times the diameter of the first part. In certain organs, such as in the urethra when the stent is implanted on opposite sides of the sphincter, the non-diseased part may also under normal conditions be somewhat larger in diameter than the part which is to be treated. The bulbar urethra is, as the name implies, wider than the prostatic urethra, and it is thus advantageous to expand the second part to a diameter that is at least 1.5 times as large as the first part.
According to an embodiment of the present inventive concept said second part has a proximal end section and a distal end section, wherein said capacity to expand radially is memorised into at least one of said end sections.
According to an embodiment of the present inventive concept each axial expansion of said end sections forms a flaring flange.
According to an embodiment of the present inventive concept each flaring flange is facing away from the second part. Thus the second part is securely anchoring the stent in both axial direction.
According to an embodiment of the present inventive concept said capacity to expand extends axially all along the stent, whereby the whole stent may be expanded and given a suitable diameter in relation to both the diseased and the non-diseased parts. Especially if the pathway into the diseased part is tight, it may be painful for the patient unless the stent is made as small as possible until it is expanded to its treatment diameter. According to an embodiment of the present inventive concept a distal end of said second part is adapted to expand radially at expansion so as to be released from a catheter onto which the stent is mounted at implantation thereof into a patient. When the distal end of the second part, by the expansion of the stent, is expanding radially, the distal end is given a somewhat larger diameter than the catheter and catheter shaft. Also, the diameter of the second part becomes somewhat larger than a stop ring on the catheter that otherwise would keep the second part in place. Thus the second part may be passed over the stop ring and the catheter may be removed from the urethra.
According to an embodiment of the invention at least said second part is made of a memory or a recovery metal. This way the capacity to expand is easily incorporated into the stent.
According to an embodiment of the invention at least a proximal end of said second part is designed so as not to rotate during expansion thereof.
According to an embodiment of the present inventive concept a thread is attached to the proximal end of said stent. The thread may be used to facilitate the removal of the stent by pulling it or by stretching it to prevent displacement of the stent when inserting an endoscope there through for inspection. To use ordinary graspers to grasp the wire end for removal of the stent is difficult and there is a risk that the wire end protrudes and causes damage to the patient at removal. Since the proximal end is not rotating, the thread will not be wound around the catheter shaft. Furthermore, when the thread is attached to the proximal end of the stent, the end of the stent will place itself in the longitudinal direction of the urethra when the thread is pulled for removal of the stent from the organ, the risk of scratching the organ will be reduced.
According to an embodiment of the present inventive concept said second part is divided into an even number of pairwise arranged sections wound in opposite directions, the change in direction between adjoining two sections being obtained by a turn or fold, said sections being of substantially equal length. This way, not only the distal end of the second part will stay fixed during the expansion as it is kept by the catheter, but also the proximal end, while the expansion takes place by rotation of the central part. Another advantage is that each rotating section, between the turns or folds, becomes shorter than if the second part would have been one long section. During rotation of one such section, of either length, the material of each section generates friction against the underlying catheter and the surrounding urethra. The shorter each section, the less friction is thus generated against the catheter, and the easier it is to expand the stent and later remove the catheter from the stent and urethra.
According to an embodiment of the present inventive concept its three parts are integrally formed in order to make the stent easy and cheap to produce.
According to another aspect of the inventive concept a catheter is disclosed for the implantation in a tubular organ of the body of a stent having a first part acting as a stentbody, a second part acting as an anchoring element and there between a connecting part, said catheter comprising a catheter shaft with a handle and stent expansion means at its proximal end and a stent holding part at its distal end, wherein said stent holding part is divided into a distal stentbody holding part, a proximal anchoring element holding part and there between holding means for releasable holding of said connecting part of the stent when said stent is mounted on said catheter. The stent is firmly held by the stent holding part, by said holding means, which may be important since the organ is sometimes not only tight but also not straight, such as the urethra. Thus a flexible and gentle catheter and stent is of importance to the patient. The usability and easiness of mounting of the stent on the catheter and its release are likewise important for the production and for the operator.
According to an embodiment of the present inventive concept said holding means is constituted by a sleeve enclosing said catheter shaft and provided with an axially extending slit along its length, said slit accommodating said connecting part when a stent is arranged on said catheter. The slit enables easy mounting and release of the stent from the catheter.
According to an embodiment of the present inventive concept said stent expansion means comprise connecting means at the proximal end of the catheter shaft for the introduction of a warm liquid into channels within the wall of said catheter shaft, which channels are interconnected with outlet openings at the stent holding part for said warm liquid, wherein said outlet openings are provided at least at the anchoring element holding part. No extra parts are thus needed for the introduction of warm liquid into the urethra for the expansion of the stent at implantation.
According to an embodiment of the present inventive concept, it further comprises a positioning balloon attached at the distal end of said catheter shaft and connected via the catheter shaft to a source of a pressure medium for the purpose of expanding the balloon when positioned in the urinary bladder during implantation. The exact location of the bladder neck, and thus the adequate position for the stentbody at the bladder neck if so desired may be easily found.
According to an embodiment of the present inventive concept said stent expansion means comprise a cylinder having wire locking means in its distal end and a operating element at its proximal end, said cylinder and operating element being rotationally and concentrically arranged around said catheter at said handle, wherein said cylinder, when a stent is arranged on said catheter, is adapted to control the expansion of the stent. This way there is a further means for controlling the expansion of the stent provided on the catheter. It may for the operator be advantageous to exactly know how and where the stent is expanding and by this feature also the speed of expansion may be controlled.
According to an embodiment of the present inventive concept said holding means is provided with at least one inspection opening through which the position of the proximal end of the stentbody in relation to the sphincter can be accurately determined by an endoscope introduced through a passage in the catheter shaft in use of said catheter. An endoscope is a standard instrument kept at hand by each urologist.
According to an embodiment of the present inventive concept said inspection opening extends somewhat into the proximal end of the part of the catheter shaft embraced by the stentbody when a stent is arranged on said catheter. If needed, the endoscope may be used to reduce the flexibility of the distal end of the catheter during implantation.
According to an embodiment of the present inventive concept said catheter is adapted for implantation of a stent according to any one of the earlier disclosed embodiments of the present inventive concept.
According to an embodiment of the present inventive concept, after expansion of said stent, said connecting part is arranged approximately at a centre line along the axial direction of said stent. Thus the connecting part is also provided approximately at the centre of the sphincter, causing less discomfort for the patient.
According to yet another aspect of the present inventive concept a method is disclosed for the implantation of a stent in a urethra using a catheter comprising a catheter shaft onto which a stent according to any one of the earlier disclosed aspects of the present invention is arranged, said method comprising the steps of: inserting the catheter carrying said stent into said urethra; positioning the catheter so as to place a stentbody of said stent within said urethra with an end thereof in close proximity of a sphincter; releasing the capacity to expand radially of at least an anchoring element of said stent; allowing at least said anchoring element to expand so as to provide anchorage of the stent in said position; and releasing said stent from said catheter shaft and withdrawing same from said urethra leaving said stent in position.
According to an embodiment of the present inventive concept the capacity to expand is released by an increase in temperature caused by a warm liquid.
According to an embodiment of the present inventive concept the capacity to expand is released by an increase in temperature caused by the body into which the catheter and stent is implanted. There is thus no need for any further step for releasing the capacity to expand.
According to an embodiment of the present inventive concept the release of the stent from the catheter shaft is caused by the radial expansion of said anchoring element. There is thus no need for any further equipment or step for releasing the stent from the catheter.
According to an embodiment of the present inventive concept said catheter comprises in its distal end a balloon, wherein during positioning of the catheter with said stentbody within said prostate the distal end of the catheter is inserted into the bladder, said balloon is inflated within the bladder, and the catheter is retracted until the balloon is lying against the bladder neck, thereby defining the position of the stentbody at the bladder neck. A simple concept of implanting the stent may be used for the stent of the present inventive concept.
According to an embodiment of the present inventive concept said catheter is provided with at least one inspection opening enabling direct vision with an endoscope, wherein during positioning of the catheter with said stentbody within said prostate the inspection opening with the endoscope is inserted into the prostatic urethra; and finding via direct vision in the endoscope the distal end of the sphincter, thereby defining the position of the proximal part of the stentbody. Instead of as when implanting the stent with a balloon catheter implanting it by determining its position in relation to the bladder neck, it is in this embodiment possible to determine the position of the proximal part of the stentbody in relation to the distal part of the sphincter. If, in the balloon catheter positioning, the stentbody is chosen too long due to an incorrect measurement, the proximal end of the stentbody might end up into to the sphincter and cause incontinence. When instead using the method according to the present embodiment, the accuracy of the measurement of the prostatic urethra is of less importance. It is fully acceptable if the distal end of the stentbody penetrates somewhat into the bladder compared to the consequences when the proximal end thereof penetrates into the sphincter. Another advantage is that by using this technique, the number of different stent-lengths to keep in stock may possibly be reduced to as few as two or three.
According to an embodiment of the present inventive concept said stent is made at least partly of a material having memory capacity, wherein said method further comprises the step of introducing a liquid at a temperature below a material softening point at the parts of the stent to be softened, thereby softening at least parts of the stent material. The stent, or the parts of the stent made of the memory capacity material, may thus be easily removed from the urethra. The operator is merely introducing the cooled liquid and softened parts may thus be withdrawn, almost in the shape and state of a long thread. If not softened, the stent would have to be removed in its expanded state, which could cause the patient some discomfort.
According to an embodiment of the present inventive concept the liquid is introduced only into the bulbar urethra. This way the stent may be fully made of a material having memory capacity, but still only the part thereof that is situated within the bulbar urethra is made soft by said liquid. Thus the sphincter does not need to be penetrated as is necessary in prior art with less discomfort for the patient and easier handling for the operator as a result.
According to an embodiment of the present inventive concept the method further comprises the step of grasping the proximal end of said stent and withdrawing said stent from the urethra.
According to an embodiment of the present inventive concept the method further comprises the step of grasping a thread which is attached to the proximal end of said stent and withdrawing said stent from the urethra. It is simpler to grasp a thread which is lying slack within the urethra instead of trying to grasp the more rigid proximal end of the stent. The thread may have a length such that it almost ends up at the meatus of the penis, making it even simpler to grasp.
a-11b are perspective views of different embodiments of the expanded anchoring element,
a is a partial longitudinal section of the region around the prostate having an expanded stent according the
b is a partial longitudinal section of the region around the prostate having a stent implanted and the softened anchoring element partly removed there from,
c is a partial longitudinal section of the region around the prostate when the softened anchoring element and the softened stentbody are partly removed there from by pulling the thread and the partially straightened wire,
a-15d are side views of alternative embodiments of expanded anchoring elements of a stent according to the present invention,
e-15f are perspective views of alternative embodiments of expanded anchoring elements of a stent according to the present invention,
In the claims and throughout this description the term axial direction is meant to be understood as a direction along the length of the urethra of a patient, and at the same time as a direction along the extension of a stent, between its proximal and distal ends, which is to be implanted within said urethra. The terms proximal and distal ends respectively are similarly meant to be understood as seen from the view point of the operator.
The stentbody 8, as well as the anchoring element 10 and the connecting part 9, could be made of the same memory material such as Nitinol, but the stentbody 8 and the connecting part 9 could also be made of different materials. It is however important that the anchoring element 10 is expandable for the anchoring of the stentbody 8. The stentbody 8 and the anchoring element 10 are in this embodiment designed as wound cylindrical spirals made of a wire of the memory metal Nitinol. When the stentbody 8, the anchoring element 10 and the connecting part 9 are all made of the same wire and thus of the same material, the production thereof will be particularly simple and thus cheap, and as will be demonstrated below, will be very easy to remove from the patient if so desired.
The expanded form of the anchoring element 10, or of any one of the parts of the stent that should be expandable, has been given thereto by winding a Nitinol wire around a tool of the desired expanded configuration. The wound anchoring element 10 (or other part(s) to be expandable) in this way form a package. The package has then been heated at the forming temperature to set the initial shape as earlier described. After cooling to the martensite state the softened material has been wound around a shaft to the cylindrical configuration, as is shown in
The connecting part 9 goes through the opening of the sphincter 5 without imparting the sphincter's 5 capability to fully close. In this embodiment the connecting part 9 is merely a wire around which the sphincter 5 can close and seal off the urethra at this point. Even though the connecting part 9 may in some embodiments of the stent be positioned not fully in the centre of the sphincter 5 when implanted in the body due to the manner in which the stent has been wound and memorised, the sphincter 5 still has the capacity to pinch and fully close the urethra. The connecting part 9 may for instance be somewhat flexible so that the closing of the sphincter 5 is pressing the connecting part 9 towards the centre of the sphincter 5 and thereby allowing symmetric closure of the sphincter 5. The connecting part 9 may also be preformed to get a curvature making it pass through the centre of the sphincter 5 and thereby reaching the same result. See further
As shown in
The anchoring element 10 with the flanges 15 and 16 have thus expanded in the bulbar urethra 6 which due to its tubular form is more suitable for anchoring than the diseased prostatic urethra 2. Another advantage is that the anchoring element 10 can be positioned on a preselected distance from the sphincter 5 avoiding interference with the sphincter's 5 movement. The double flanged anchoring element 10 also offers excellent resistance against migration of the stent in both of its axial directions in contrast to the prior art.
In order to be able to work efficiently and smoothly at implantation, it is desirable that the outer diameter of the stent is approximately 8 mm as a larger diameter can be painful for the patient. If the diameter it is very much smaller the flowrate will be reduced. It is generally contemplated that an expansion of approximately 1.5-2 times is the most that is recommended and conceivable. However, the stentbody 8 could be made somewhat smaller than 8 mm diameter at implantation in order to lessen the discomfort for the patient. If the stentbody 8 furthermore is made of a memory metal and is given an expanding feature, the stentbody 8 after implantation, at expansion, could expand up to the desired 8 mm diameter. The effect of increasing the diameter of the urethra is thus met.
With an unexpanded stentbody 8 of 8 mm diameter—and possibly also the whole unexpanded stent having a similar diameter, the wire is preferably approximately 0.65 mm in diameter and the inner diameter of the stentbody 8 thus approx. 6.7 mm. The outer diameter of the catheter suitably has an outer diameter of 6.3 mm leaving a clearance in relation to the stent of 0.2 mm on each side which is enough for the catheter to be easily removed from the stent, even if the stentbody 8 is not expanded. The inner diameter of the catheter is suitably 4.5 mm which will give a clearance of about 0.25 when using a standard endoscope of 4 mm in diameter.
As can be understood of earlier description the different parts of the stent are fixed in the axial direction, so for example is the stentbody 8 fixed between the balloon 13 and distal edge 33 of the tubular holding means 11, and the anchoring element 10 between the proximal edge 34 of the holding means 11 and the stop ring 23. Furthermore, the connecting part 9 is positioned in the slit 26 and therefore the mounted stent and its different elements can not rotate in relation to the catheter 12. This is particularly important during the introduction of the stent when manipulations in different directions are necessary in order to get the stent into place.
As the end of the wire 43 will stay fix, the thread 42 will not be wound around the catheter at expansion as it would have been if a similar thread had been attached to the corresponding wire end in the embodiment according to
The possibility to attach a thread to the proximal part of the anchoring element 40 has many advantages. For example can a long thread 42 be left after implantation floating in the bulbar urethra with the end close to the meatus. After injection of cooled down water as described earlier the end of the thread may easily be grasped and the softened stent be pulled out. See in particular
a and 11b illustrate different embodiments of the stent in which the connecting parts 9 have been differently designed when compared to one another. In both figures the expanded stent has been left in the urethra and the catheter is withdrawn. Also, both stents are made in one piece of one wire of memory metal. The parts of the wire making up the connecting parts 9, and approximately half a turn on each side thereof, i.e. half a turn at the proximal parts of the anchoring element 10 and half a turn of the distal parts of the stent bodies 8, have been ground to become somewhat thinner in diameter. Thereby the axial stiffness is maintained while the bending stiffness is lessened. In the embodiment illustrated in
a-13c also illustrate one embodiment of the present invention, implanted within the prostatic urethra 2, in which the whole stent is made of a material with memory capability. The stentbody 8, the connecting part 9 and the anchoring element 10 are thus made integrally in one piece of a memory material such as Nitinol. The stent will assume the martensitic state when cold water is flowing over it. This means that an operator has to inject cold water not only into the bulbar urethra, but also to pass the sphincter 5 to let the water flow within the prostatic urethra 2. After the stentbody 8, the connecting part 9 and the anchoring element 10 have been treated with cold water to soften, they will in general keep their initial state until the operator starts pulling them out. This is shown in
Another advantage by using a thread 42 is that by grasping the thread 42 the stent can be held so that a Foley catheter can be inserted through the stent in case of acute retention eliminating the risk for migration by pushing the anchoring element 10 and the stentbody 8.
a-f show some alternative embodiments of expanded anchoring elements 10′ within the scope of the invention. In
In order for the stent to be released from the catheter, the whole anchoring element 10, 40 and 10′ must at least expand somewhat. Otherwise it may not be passed over the stop ring 23.
As mentioned it is desirable that the stentbody 8 at implantation covers as much as possible of the prostatic urethra 2 from the bladder-neck 4 to the sphincter 5 without disturbing the function of the sphincter 5.
In the catheter shaft an opening 54 is arranged (broken line) together with an opening 55 in the holding means 53 creating an opening extending at least to the distal end of the holding means 53. An endoscope or telescope 56 is positioned within the catheter shaft 51 and can be moved axially along the shaft 51.
In
An advantage with this method in contrast to the method of positioning the stent starting from the bladder-neck 4 using a positioning balloon 13, is that the operator can select a stentbody 8 which is somewhat longer than the measured needed length between the bladder-neck 4 and the sphincter 5. If there is an excess in length of the stentbody 8 after the precise placement going out from the sphincter 5 side, this excess will protrude somewhat into the bladder which will not harm.
Alternatively, the catheter shaft 51 inside the stentbody 8, can be made very short. This way it will only protrude a very short distance into the stentbody 8, possibly only a few millimetres. The most part of the stentbody 8 is thus not supported by the catheter shaft 51 and will be very flexible. In order to be able to implant the stent, the endoscope however will have to be pushed forwards towards the distal part of the stentbody 8 for keeping it supported, at least before and during the implantation.
It is suitable to produce stents having stentbodies 8 of different lengths in order for the operator to be able to chose an appropriate length for each patient. The stents to be implanted using a catheter with a positioning balloon 13 need preferably to come in 5 mm incremental stentbody 8 lengths, such as 25, 30, 35 mm etc. The stents to be implanted using a catheter with an endoscope 56 need however preferably to come in only 10-15 mm incremental stentbody 8 lengths, such as 40, 50, 60 mm. The difference between the two methods is that since the endoscopic method is going out from the position of the sphincter 5, the stent may penetrate somewhat into the bladder. However, in the balloon-method, the position of the bladder-neck 4 is decisive for the position of the stentbody 8, and if this is too long it will penetrate into the sphincter 5, which is negative for the sphincter performance. It should also be remembered that the initial measurement of the length of the prostatic urethra 2 is not exact, but involving a certain amount of uncertainty, making the choice of stentbody 8 length somewhat difficult to begin with. At least when the stent is used as a temporary stent, it is not harmful for the patient of the stentbody 8 penetrates into the bladder. Thus, when using the endoscopic method, the operator needs to have in store only half as many stents, or two to three different lengths, as if instead the balloon-method would be used, saving both money and storage capacity.
At the mounting of the stent on the catheter before implantation, the anchoring element 10 which is in a soft martensitic state, has been attached to the cylinder 60 and stretched and been given its cylindrical shape by rotating the wheel 62 and then been locked in place to the catheter by locking means not shown.
A telescope 56 is in a well known manner concentrically arranged inside the cylinder 60 in order for it to be slidable axially. A space (not shown) is created between the telescope 56 and the cylinder 60, allowing rinsing water flow from the inlet 63 along the telescope to keep the lens of the telescope 56 clean.
The implantation of the stent in the urethra 2, 6 takes place as earlier described in connection with
When the operator finds that the stentbody 8 is correctly positioned he can let the anchoring means 10 expand by turning the wheel 62 in opposite direction to the earlier mounting direction of the wound spiral. The distal end of the anchoring means 10 will be released by the expansion from the holding means 53. The proximal end of the anchoring means 10 can also be released automatically because of the axial shortening of the anchoring means 10 when expanding.
The method of producing the stent according to the present invention may thus be summarised in the steps of winding a wire of a material having memory capability around a tool having the shape of the expanded stent. Thereafter the material is heated up to its forming temperature. Then the wire is cooled down to its martensite state and rewound to correspond to the unexpanded shape and in which it may be placed around a catheter 12 prepared for implantation. When the stent has been arranged on the catheter 12 it is ready to be implanted into the body by inserting it via the urethra.
The method of implanting the stent and catheter into the urethra in begun by measuring the length of the prostatic urethra 2, for instance with an endoscope and a scale, in order to chose a stentbody 8 of a correct length. An anaesthetic agent is then spread in the urethra. Thereafter the implantation of the stent via the urethra 6 takes place. If the stent is implanted with the aid of a catheter according for example
In both of the above described alternative embodiments of the method of placing the stent within the urethra, hot water is now injected into the channels 32 and out through the outlet holes 24. Under normal circumstances the hot water should be spread through the outlet holes 24 simultaneously. When the hot water meets the memory metal parts of the stent, especially the anchoring element 10, these parts within almost no time at all expand to its expanded state. Now the catheter is released and be pulled out with the endoscope, leaving the stent implanted. If the patient needs the be examined within the urethra or the bladder, or needs a Foley catheter to be implanted, such catheters or endoscopes may still be passed through the stent since it does not block the passage way into the bladder. The thread 42 could be stretched with a grasper to prevent that the stent will be pushed forwards.
When and if the stent should be removed again from the patient, ice-water is inserted into the urethra at the areas where the stent should be softened. The treating doctor or nurse may then grasp the thread 42 and simply and gently pull out the stent.
When using the stent and catheter of
The catheters for the different embodiments of the inventive concept can be made very cheaply, particularly the one using the endoscopic method, and can therefore be used as disposables. Thus catheters with different stent body lengths can be mounted directly upon production. The operator consequently only has to select the suitable stent body length. He or she is thus released from the task to mount the stent on the catheter.
It is to be understood that various modifications, alterations and adaptations may be made by those skilled in the art without departing from the spirit and scope of this invention. The manifestations of the form in the figures of the implant insertion devices according to the present invention are only schematic representations. For instance is it not necessary that the stent according to the present invention is a temporary stent, but it could also successfully be used as a permanent stent. Furthermore, the stent may be used not only in combination with thermotherapy of the prostate, but as a stent for keeping the prostatic urethra open with or without the preceding thermotherapy. Also, the stent may be used in the treatment of strictures in the bulbar urethra, in which case the anchoring element 10 instead would be implanted within the prostatic urethra 2 and the stentbody 8 would be implanted within the bulbar urethra 6. The stent may be used in any method of keeping a tubular organ of the body open for passage, such as the oesophagus.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2005/011617 | 10/29/2005 | WO | 00 | 2/20/2009 |
