JP2008543470A - Artificial transplant tube - Google Patents

Abstract

A method of making an artificial graft tube is disclosed. The method provides a helical mandrel having a substantially spiral centerline, providing a tubular wall having a longitudinally extending cavity, wherein the longitudinally extending cavity is substantially spirally centerline. Placing a helical mandrel in the tubular wall to hold the tubular wall in a shape comprising a helical cavity extending at least partially in the longitudinal direction. Another method provides a mandrel having a substantially spiral groove and provides a tubular wall having a spiral longitudinally extending cavity, wherein the longitudinally extending cavity follows a substantially spiral. Placing the tubular wall in the groove to have a centerline and holding the tubular wall in a form at least partially comprising a longitudinally extending helical cavity.

Description

  The present invention relates to a method of making an artificial graft tube method and a graft tube made by the method.

Conventional technology

  We have previously shown that intra-arterial flow patterns, including spiral patterns caused by the non-planar shape of the arteries, inhibit the growth of vascular diseases such as thrombosis, atherosclerosis, and intimal hyperplasia. Proposed to work.

  It is known from WO 95/09585 to provide an artificial blood vessel that has openings at both ends and is a hollow tube over its entire length, including a non-planar curved portion and causing a swirling flow in blood flowing through the curved portion. ing. As explained in that publication, swirl flow caused by oblique flow of blood flow in a non-planar bend improves flow characteristics and builds up deposits including intimal hyperplasia and vascular system Reduce the potential for illness.

  How the non-planar shape of the tube prevents flow instability is described by Caro et al. (1998) J. MoI. PHYSIOL. 513P, 2P. A further aspect of how swirl is beneficial is R. SOC interface (2005) 2, 261-266.

  A flexible tube is wrapped around the mandrel to form the tube so that the longitudinally extending cavity inside the tube has a spiral centerline, and then the tube at least partially It is known from WO 2004/082534 to make an artificial helical graft tube by thermosetting the tube to hold it. In one method shown in FIGS. 12A-12E of the publication, the mandrel consists of a rigid rod and is formed in a spiral. In another method shown in FIGS. 13A and 13B, the mandrel consists of a straight steel bar around which a steel wire is spirally wound and secured. In either case, because the graft tube material is soft and flexible, it is necessary to support the flexible tube during wrapping around the mandrel and maintain the cross-sectional shape during this process. It has been proposed to place a support consisting of a silicone rubber tube within a flexible graft tube. This method therefore requires additional components in addition to the mandrel outside the flexible tube. In addition, care must be taken to ensure that the flexible tube is in the correct shape so that the final graft tube has the intended helical pitch and amplitude. The initial winding of the flexible tube around the mandrel must be done accurately and then the flexible tube must be held in place along its length during the thermosetting process.

  According to a first aspect of the invention, a method of making an artificial graft tube is provided. The method provides a spiral mandrel having a centerline that follows a spiral path; provides a tubular wall having a longitudinally extending cavity; and spirals such that a longitudinally extending cavity has a centerline that follows a spiral path Placing the tubular mandrel within the tubular wall; holding the tubular wall at least partially in the form of a longitudinally extending helical cavity.

  Such a mandrel is useful, for example, in properly forming the necessary helical shape that the tubular wall forms with respect to helical angle and amplitude. The tubular wall in effect automatically follows the predetermined shape of the mandrel.

  Such mandrels can also retain the desired cross-sectional shape of the longitudinally extending cavity. A snug fit of the mandrel within the tubular wall can ensure, for example, a fit where the diameter of the mandrel is at least 90 percent, more desirably 95 percent of the inner diameter of the tubular wall.

  In general, the tubular wall has a shape that changes from its basic initial shape, and is preferably changed from a substantially cylindrical shape to a spiral by placing it on a mandrel. Thus, the pre-existing tubular wall is modified by a mandrel whose shape is placed inside. An “inner” mandrel is made, for example, by sintering stainless steel with a rapid prototyping laser or by cutting, for example, a stainless tubular rod.

  Implants made with the methods disclosed herein are suitable for in vivo use in humans or animals. The graft tube is suitable for use as a prosthesis for carrying a body fluid, for example a blood stream. For example, a transplant tube can be used as an artificial blood vessel. Transplanted tubes are also used for tube access transplants of the type that are punctured with a needle to draw blood back and, for example, for dialysis. Thus, the tube can carry body fluid directly against its inner wall.

  Alternatively, the tube can be placed on a natural tube of the human or animal body, eg, outside the blood vessel. As a result, the tube can operate as a sheath or stent outside the natural tube that carries fluid flow. When the graft tube is used outside of a natural tube, it is sometimes desirable to cut the graft tube longitudinally during deployment to facilitate insertion of the natural tube material. Medically speaking, the cut is repaired by sewing or the like.

  Desirably, the tubular wall is thermoset that at least partially retains its shape with a longitudinally extending cavity. Since an internal mandrel is used, the tubular wall can be evenly exposed to external heating conditions during thermosetting.

  In a preferred embodiment, the tubular wall is made of ePTFE. In this case, thermosetting is used to hold the spiral. In order to spiral the tubular wall by heat curing, it is heated to a temperature in the range of 340-380 ° C., more preferably 350-370 ° C., for 10-30 minutes, more preferably 15-25 minutes. In the most preferred method, the tubular wall is heated to 360 ° C. for 20 minutes.

  It is known to provide a cylindrical PTFE graft tube that is supported from outside by a helically wound polymer filament. The purpose of such support is, for example, to reduce the possibility of twisting when the implantation tube is implanted across the joint. The helical angle of such externally supported graft tube filaments (ie, the angle relative to the longitudinal axis of the graft tube) is on the order of 80 ° or more. We have found that this type of transplant is a suitable starting material for carrying out the method of the invention. Thus, desirably, the tubular wall can include a spirally wound support. Desirably, support is provided outside the tubular wall. Desirably, the helical angle of the spirally wound support is at least 70 °. The spirally wound support can be in the form of a tape or wrap.

  In one preferred method, the elongated member is used to extend longitudinally into the tubular wall when the tubular wall is supported by the mandrel. Such elongate members are provided to help reduce the tendency of the helical implant to be straightened and reduce the reduction in helical amplitude. Such a tendency to straighten is due to the internal pressure of the fluid, eg, arterial pressure, or due to axial stretching when the graft is used near the joint, or alternatively these two are It is generated by combining. A further cause of straightening is in “stretching” and deploying the graft tube.

  In the process described in WO 2004/082534, such a helical reinforcement to resist straightening is applied to the tube before the tube is in a tubular state and is deformed and heat-cured. Is done. However, it may be difficult to accurately apply the helical reinforcement portion to the initial cylindrical tube, especially when it is made of a relatively flexible material. A similar method is described in WO 2004/082520 in connection with the manufacture of a tube placed outside a conduit through which a body fluid such as a blood vessel flows.

  However, in an embodiment of the invention that uses a reinforcing elongated member, it is easy to apply the elongated member to the tubular wall because the tubular wall is supported from the inside by the mandrel. The inner mandrel allows the elongate member to apply pressure to the tubular wall without causing deformation.

  The elongate member can be a strip, bead, thread, filament or similar shape. It can have a wide or narrow width (ie a dimension in the circumferential direction of the tubular wall). More than one elongate member can be provided to provide additional resistance to graft extension.

  The elongated member can be applied to extend substantially only in the longitudinal direction of the tubular wall. This means that the elongated member is effectively only on one “side” of the tubular wall. If it lies outside the tubular wall, it will all be visible along that side without hiding behind the tubular wall. The elongate member preferably has a surrounding element as well as a longitudinal element. Thus, in a preferred embodiment, the elongated member is stretched both circumferentially and longitudinally around the tubular wall. The elongate member will then have a pitch corresponding to its own helix angle. It is generally desirable that the helical angle of the elongate member is not so great. This is because the greater the helix angle, the less resistance to the axial extension of the graft tube provided by the elongated member. Desirably, the helix angle is about 70 when measured relative to the overall axial direction of the graft tube (ie, relative to the axis about which the helical centerline of the longitudinally extending cavity rotates). It is less than °. For example, the spiral angle can be about 30 ° to 40 °.

  Extend the elongate member helically along the tubular wall at a pitch that is slightly larger than or approximately equal to the pitch of the longitudinal centerline of the cavity (i.e., with a helix angle smaller than the helix angle of the helix centerline). It is desirable.

  The elongated member can be applied to the tubular wall in a variety of ways. For example, a suitable adhesive can be used or sewn. The elongate member can be intermittently attached to the tubular wall, providing a sufficient number and density of attachment points or regions for the elongate member to help the tubular wall hold the helix. Desirably, the elongate member is attached over the entire length of the tubular wall. Most desirably, the elongate member is bonded to the tubular wall, for example by a heating step. To this end, heat-activatable adhesives can be used, or materials that form a tubular wall and / or elongated member that softens and welds during heating may be used.

  As a suitable method, one end of the elongate member is secured to a mandrel or tubular wall and then tensioned longitudinally while being helically applied to the tubular wall to ensure the degree of contact pressure between the elongate member and the tubular wall. To.

  The elongated member can be applied after the initial heat curing step and a further heating or deposition step is performed to adhere the elongated member to the tubular wall. Desirably, a single heating step that simultaneously bonds the elongate member to the tubular wall and at least partially retains the shape of the cavity extending in the longitudinal direction by thermally curing the tubular wall. Can do. Thus, a graft tube that cannot be relatively expanded by a single heating step can be made.

  A suitable method is to place a helical mandrel in a tubular wall to form a helical tubular wall, where the tubular wall is helical and the tubular wall is supported by the helical mandrel. When the elongate member is applied to the tubular wall as it is stretched in the longitudinal direction of the tubular wall, the helical mandrel, the tubular wall and the elongate member are heated to heat cure the tubular wall and bond the elongate member to the tubular wall .

  In one preferred embodiment, the tubular wall and the elongated member are made of ePTFE. In order to heat cure the tubular walls into a helical shape and adhere the elongated members thereto, for example, they are heated to a temperature in the range of 330-350 ° C. for 10-15 minutes. Preferred values are 340 ° C. and 10 minutes.

  It is considered independent and patentable to apply an elongated member to the tubular wall after the shape of the tubular wall has been changed to a spiral. Thus, according to a second aspect of the invention, there is provided a method of making an artificial graft tube, wherein a tubular wall having a longitudinally extending cavity is provided; the longitudinally extending cavity has a center line that follows a spiral Forming a tubular wall, holding the tubular wall in a shape comprising a spiral cavity extending at least partially in the longitudinal direction, and then applying an elongated member to the tubular wall to extend in the longitudinal direction. A method comprising comprising is provided.

  By applying the elongate member to the tubular wall once the tubular wall is helical, the tubular wall can better receive the elongate member.

  Since the elongated member extends in the longitudinal direction of the tubular wall, it tends to reduce the axial extension of the graft tube. If the length of the transplant tube is increased, the amplitude of the spiral center line of the cavity extending in the longitudinal direction is decreased, and the pitch of the corresponding spiral is increased. Such straightening is reduced by providing an elongated member.

  The step of holding the tubular wall at least partially helical may be by heat curing it. Thus, one preferred method includes a first heating step that heat cures the tubular wall in a helical fashion and a second heating step that bonds the elongated member to the tubular wall after the elongated member is applied to the tubular wall. Desirably, the temperature at which the tubular wall is heated in the first heating step is lower than that at which it is heated in the second heating step.

  There are many ways to form a tubular wall such that its longitudinally extending cavity has a spiral centerline and is not necessarily limited to the use of internal mandrels. In one suitable method, the tubular wall is formed by wrapping it around a mandrel. Such a mandrel is located “outside” of the tubular wall. The mandrel for making the tubular wall can be quite soft and flexible, but in that case, for example, when the tubular wall is wrapped around a cylindrical mandrel, it is difficult to maintain the cross-sectional shape of the tubular wall itself. is there. Thus, desirably, the mandrel has a helical groove that at least partially receives the tubular wall. Such a groove serves as a support for the tubular wall both during the initial shaping step of spiraling the tubular wall and during the step of causing the tubular wall to retain at least a partial spiral. The groove can also provide support during the step of applying the elongated member to the tubular wall (if the tubular wall remains on the mandrel during that step).

  The spiral groove desirably provides some support on the opposite side of the tubular wall. It is desirably formed to correspond to a portion of the outer surface of the tubular wall that contacts the groove. This is beneficial in minimizing tool marks left on the tubular wall by the mandrel. In the case of a tubular wall with a circular cross section, the groove can thereby be provided so that it has a partial circular cross-sectional shape. The groove can have a set of sidewalls separated by a base wall. In the latter case, the tubular wall is properly supported in engagement with the first side wall, the base wall, and the second side wall. The side wall and the base wall can be curved or straight.

  In the above method of forming a tubular wall by wrapping around a mandrel, an internal support (support) can be used in the tubular wall to help it retain its cross-sectional shape. However, preferably no internal support is used.

  The helically formed tubular wall can be removed from the mandrel before the elongated member is applied. However, preferably the elongated member is applied to the tubular wall when it is supported by a mandrel. This can help to apply the elongate member correctly, for example with respect to the required helix angle. If the tubular wall is formed, for example, around a mandrel, the elongated member can be applied at the same helix angle as the tubular wall by contacting the radially outermost portion of the tubular wall with the elongated member in the wound state. . In the case of a helical mandrel inserted into the tubular wall, the mandrel provides support for the portion of the tubular wall to which the elongated member is applied. Thus, this configuration facilitates applications of elongate members that extend only in the longitudinal direction, or elongated members that are not the same helix angle as the tubular wall.

  Preferably, the elongated member is applied to the outside of the tubular wall. Thus, the elongated member has a minimal amount of influence on the cross-sectional shape of the longitudinally extending cavity. When the graft tube is used to carry a body fluid flow directly or as a natural tube sheath, it is desirable to avoid having internal ribs or grooves in it. This is because it leads to flow obstruction including flow stagnation in the area of the ribs or grooves. By applying the elongate member to the outside of the tubular wall, any internal protrusions that can be caused by the elongate member can be substantially avoided, especially in the radially inward direction acting on the tubular wall when the elongate member is applied. The pressure of is minimized.

  Various other features described herein in connection with graft tube manufacture can be used alone or in combination with others in combination with the second aspect of the invention.

  The use of a mandrel with a helical groove to make an artificial graft tube is per se considered to be patentable. Thus, according to a third aspect, the invention provides the following method of making an artificial graft tube. That is, the method provides a mandrel having a helical groove; provides a tubular wall having a longitudinally extending cavity; and aligns the tubular wall such that the longitudinally extending cavity has a centerline following the spiral path. Holding at least partially in the groove; retaining the shape comprising a spiral cavity extending the tubular wall at least partially longitudinally.

  As explained above, such a helical groove is tubular while the tubular wall is at least partially placed in the groove and while it is adapted to at least partially hold the spiral. Support the wall. Generally, the tubular wall is generally placed at least partially in a spiral groove. Thus, at least in a preferred embodiment, the centerline of the longitudinally extending helical cavity extends along the groove. Such mandrels are used with or without elongated members that help to resist longitudinal stretching.

  Various other features described herein in connection with graft tube manufacture can be used in combination with the third aspect of the invention, either independently or in combination with others.

  In all aspects of the invention, the tubular member can be made of a variety of biocompatible materials. Desirably, a woven or non-woven fabric made of a polymeric material can be used. One suitable material is extensible polytetrafluoroethylene (ePTFE), alone or in combination with other polymers or additives. Another suitable biocompatible material is polyester, for example, knitted polyester yarn such as polyethylene terephthalate known as Decron®.

  The elongated member, if provided, can also be made of various biocompatible materials as described above, for example. One suitable material for the elongated member is polypropylene.

  The tubular wall can be of the type reinforced with a number of circular reinforcements on the outside or a spirally wound reinforcement (with a very large helix angle close to 90 °). The stiffener can be shaped as a tape, strip, wrap, etc. so that it is suitable to be made as a tube access implant that can be repeatedly pierced laterally by a needle during use. Another shape of the reinforcing body is a bead or the like protruding radially outward from the tubular wall, and usually a longitudinal interval is provided between adjacent bead circles or windings. This type of tube is used, for example, in prostheses that experience external bending forces across joints such as the knee, and the beads help maintain a circular cross-sectional area. In some cases, beads etc. are used in addition to tape, strips, wraps, etc.

  Tubular walls with circular reinforcements or spirally wound reinforcements are a suitable starting point for the methods described herein, for example, using an internal mandrel to change the shape of the tubular wall. In embodiments of the invention that include such a reinforcement to which an elongated member is additionally applied, the elongated member is applied in addition to circular or helical reinforcement. A reinforcement having a relatively large helix angle (eg, 70 degrees or more) can provide properties such as the ability to be perforated cleanly or resist lateral compression or kinking. An elongate member having a relatively small helix angle (eg, less than 40 degrees) is intended to resist the axial extension of the graft tube and therefore tends to reduce the amplitude of the helix.

  In this specification, the amplitude of the helix refers to the lateral displacement from the mean position, and therefore for a tubular wall with a longitudinally extending cavity with a helical centerline, the amplitude is the total of the helical centerline. Half the width.

  The graft can be made with substantially the same amplitude and helix angle over its entire length. When used, the graft tube may change slightly due to expansion or contraction of the graft tube due to tensile or torsional loads. However, there may be circumstances where a graft tube with variable helix angle and / or variable amplitude is desired to suit space constraints or to optimize flow conditions. This is accomplished by appropriate custom design of the mandrel, whether external or internal type.

  For reasons of simplicity of manufacture, it is preferable to make the graft tube with a longitudinal cavity having a substantially constant cross section along its length. Again, changes may occur due to the load acting on the graft used. Desirably, the cross-sectional shape of the cavity of the implanted tube to be manufactured is circular.

  The helical tubular wall can simply form part of the total length of the graft tube, or it can span substantially the entire length of the graft tube. The helical tubular wall can be part of one complete turn, for example a quarter, half or three quarters of a turn. Desirably, the helical tube portion has at least one turn, more desirably at least multiple turns. Repeated turns of the spiral along the tubular wall tend to ensure that a swirling flow is generated and maintained.

  The invention also extends to a graft tube made by the method described herein and uses the graft tube in the human or animal body.

  Transplants made with the methods disclosed herein can be used in a variety of biomedical applications, such as various arteries (femoral, coronary, renal, etc.), veins, and digestive organs (eg, bile or pancreatic ducts), It can be used in non-cardiovascular applications such as urology (eg, ureter or urethra) or bronchi (pulmonary airways). The invention thus extends to the manufacture of transplant tubes that carry body fluids other than blood. The graft tube carries the fluid directly or is placed around a natural fluid conduit (untouched or graft).

  Several preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings.

  FIG. 1 shows a tool in the form of a mandrel 10. The mandrel is a helical stainless steel bar. In this embodiment, the mandrel was made from tubular stainless steel bar using a ball nose cutter of a CNC milling machine. Coordinates are created on the CAD / CAM system to provide the necessary helical pitch and amplitude. The mandrel is designed to be inserted into the tubular wall 6 so that the vertical cavity of the tubular wall deforms according to the shape of the helical mandrel. This can be seen in FIG.

  FIG. 3 shows a later stage when a strip-shaped elongate member 8 is applied to the tubular wall 6, where the elongate member extends longitudinally and has the same helical angle and pitch as that of the tubular wall 6.

  FIG. 4 shows the graft tube after removal from the mandrel of FIG.

  FIG. 5 shows another graft tube after removal from the mandrel of FIG. The graft tube has an external helical support tape 20.

  FIG. 6 shows a tool in the form of a mandrel 2 with a spiral groove 4 extending along its length. In this particular embodiment, the mandrel was made from a tubular stainless steel bar using a ball nose slot drill milling machine for a CNC milling machine. Coordinates are created in the CAD / CAM system to provide the required helical pitch and amplitude. The amplitude is determined by the depth of cut.

  The groove has a suitable diameter for receiving the tubular wall or tube 6 as seen in FIG. In this case, the tube is of the type made of ePTFE and customarily used as a cylindrical transplant tube. It is then formed from an ordinary elongated shape into a shape that follows the spiral groove 4 of the mandrel 2.

  In FIG. 8, an elongate member in the form of a strip 8 is applied to the tube 6. The strip 8 extends longitudinally along the tube 6 as a helix having the same pitch as the helical groove (and the tube 6 is formed by the groove).

  FIG. 9 shows a graft tube 12 consisting of a helical tubular wall with a strip 8 bonded to the outer surface. The graft tube has a longitudinally extending cavity 14 having a centerline that follows a helix. The graft tube tends to resist axial stretching, for example by a longitudinally extending strip 8, while being stretched by a surgeon or during manipulation on the human or animal body.

Example 1
A tube made of conventional cylindrical ePTFE, useful for use as an artificial blood vessel, was used. The tube has an inner diameter of about 6 mm and an outer diameter of about 7 mm. The mandrel of FIG. 1 was inserted into the tube. The mandrel has an outer diameter of 5.8 mm. The 6 mm tube inner diameter was to ensure a snug fit to the mandrel. The initial tubular tube was helically deformed as seen in FIG. The strip-flattened ePTFE filament was then wound around a tube on a mandrel. At this time, the winding strip pitch was made the same as that of the mandrel. The strip was secured to the mandrel at one end and tensioned longitudinally. As the strip was wound around the curved surface, such longitudinal tension applied a normal force (or pressure) to the strip to ensure tight contact between the strip and the graft tube (tube).

  The entire assembly was then placed in an oven at 33 ° C. for 10 minutes. This softened the ePTFE tube and strip and adhered to each other. The assembly was then cooled at room temperature. The transplant tube shown in FIG. 8 was produced.

  This process was found to allow the tube to adhere securely to the outer surface of the strip. Moreover, there were no ridges or grooves to be detected inside the transplant tube. The graft tube was essentially unstretchable as a result of the procedure. Nevertheless, the graft tube could be bent into a U-tube with a radius of curvature of about 1/3, for example.

  When the glued strip was punctured with a needle (which can occur when the graft is used to access the kidney dialysis patient's tubing), the non-extension of the graft was not reduced. Even if a hole was repeatedly drilled across the width of the strip and it was effectively cut off, it had only a localized effect and the graft tube remained generally non-extensible.

  The production of a spirally reinforced graft tube in a single heating step was accomplished as described above.

Example 2
The mandrel of FIG. 1 was inserted into the same type of tube as described in Example 1. The tube diameter was such as to ensure close contact with the mandrel. The initial tubular tube was helically deformed as seen in FIG. In this case, the strip was not wrapped around the tube. The assembly was placed in an oven at 330 ° C. for 10 minutes and then cooled. The mandrel was removed from the tube and spiraled.

Example 3
In this case, a tube made of ePTFE having an inner diameter of 6 mm was used. The tube is tubular and includes an outer helical support wrap or tape 20 wound at a helical angle of about 80 degrees. The mandrel of FIG. 1 was inserted into the tube. Initially, the tubular tube was transformed into a spiral as seen in FIG. The strip 8 (used in Example 1) was not wound around the tube. The assembly was placed in an oven at 360 ° C. for 20 minutes and then cooled. The mandrel was removed from the tube and spiraled. The resulting helical graft tube is shown in FIG. The graft tube was found to exhibit satisfactory resistance to axial elongation when a tensile load was applied to it.

Example 4
The mandrel of FIG. 1 was inserted into the same type of tube described in Example 1. The tube diameter was such as to ensure close contact with the mandrel. Initially, the tubular tube was helically deformed as seen in FIG. The tube and mandrel were placed in an oven for 1 hour at 275 ° C. and then removed and allowed to cool in air at room temperature. The same type of strip described in Example 1 made of ePTFE was applied to the tube with the same helix angle as the tube. This was done by wrapping the strip around the tube while applying a small tension to the strip to ensure tight fit, and then securing the ends of the strip with clips to maintain its position. The mandrel, tube and strip combination was heated to about 350-360 ° C. for 30 minutes. The softened ePTFE tube and strip were able to adhere to each other. A transplant tube similar to that shown in FIG. 9 was produced.

Example 5
A tube made of the same type as described in Example 1 was used. That is, a cylindrical ePTFE tube that can be usefully used as an artificial blood vessel having an inner diameter of about 6 mm and an outer diameter of about 7 mm was used. The tube was wound around a mandrel according to a spiral groove 4 having a width of about 8 mm, as shown in FIG. It was placed in an oven at 275 ° C. for 1 hour, then removed and cooled in air at room temperature. This heating step was a thermosetting step, and the shape of the tube became a spiral determined by the shape of the spiral groove.

  While the tube was still on the mandrel (within the mandrel), a strip made of ePTFE was applied to the tube. As the strips were wrapped around the tubes, a small tension was applied to the strips to ensure their tightness and to minimize the cross-sectional distortion of the tubes. The strip is placed approximately in the center of the groove and on the radial outermost surface of the tube, so it makes the same helix angle as the tube. The ends of the strip were secured by clips so that they were in place. The combination of mandrel, tube, and strip was then placed in an oven at 3-50 ° C. for 30 minutes. This softened the ePTFE tube and strip and allowed them to adhere to each other. They were then cooled in air at room temperature and removed from the mandrels. The graft tube so formed is shown in FIG. The strip 8 had a width of about 1.3 mm and a thickness of about 0.3 mm.

  In a control experiment, it was found that when using the above ePTFE tube, it was difficult to apply the strip before the tube was heat cured. This is because there is a problem in contacting the tube with a certain strip required due to deformation of the tube. However, in Example 5, since the strip was applied to the tube surface, the tube does not deform so easily after the thermosetting step, making it easier to bring the strip into intimate contact with the tube. This resulted in excellent strip / tube adhesion in the second heating step. It has been found that it is not necessary to insert a support into the tube during the molding step or the step of applying the strip.

Figure 3 shows a mandrel placed in a tubular wall. ; 2 shows a tubular wall with the mandrel of FIG. 1 inserted. Figure 3 shows a tubular wall supported by a mandrel and having an elongated member applied thereto. Figure 2 shows the graft tube after removal from the mandrel of Figure 1; Figure 2 shows another graft tube made with the mandrel of Figure 1; Figure 3 shows a mandrel around which a tubular wall is wrapped. FIG. 7 shows the mandrel of FIG. 6 with the tubular wall in place. FIG. 8 shows the mandrel and tubular wall of FIG. 7 and the elongated member applied to the tubular wall. Figure 7 shows the graft tube after removal from the mandrel of Figure 6;

Claims (21)

A method of making an artificial tube:
Providing a spiral mandrel having a centerline that substantially follows a spiral;
Providing a tubular wall having a cavity extending longitudinally;
Positioning the helical mandrel within the tubular wall such that the longitudinally extending cavity has a centerline that follows a substantially spiral;
Holding the tubular wall in a form at least partially comprising a longitudinally extending helical cavity;
A method comprising that.   The method of claim 1, wherein the tubular wall is initially cylindrical.   3. A method according to claim 1 or 2, wherein the tubular wall is thermoset to at least partially retain the shape comprising the longitudinally extending cavity.   4. A method according to claim 1, 2 or 3, wherein the tubular wall comprises a spirally wound support.   5. A method as claimed in any one of claims 1 to 4, wherein when the tubular wall is supported by the mandrel, an elongate member is applied to the tubular wall to extend in the longitudinal direction thereof. A method comprising.   6. The method of claim 5, wherein the elongate member is applied to extend around the tubular wall and longitudinally.   7. The method of claim 6, wherein one end of the elongate member is fixed and tensioned longitudinally and applied to the tubular wall.   8. A method according to claim 6 or 7, wherein the elongate member is applied to extend helically along the tubular wall at a pitch substantially equal to the pitch of the helical centerline.   9. A method according to claim 5, 6, 7 or 8, wherein the elongate member is bonded to the tubular wall in a heating step.   10. The method of claim 9, wherein the heating step adheres the elongated member to the tubular wall and at least partially retains the shape of the tubular wall comprising a cavity extending in the longitudinal direction. A method that is a single heating step that serves both functions of thermosetting the tubular wall.   Providing a tubular wall having a longitudinally extending cavity; and forming the tubular wall such that the longitudinally extending cavity has a substantially helical centerline, at least partially in the longitudinal direction A method of making an artificial graft tube comprising holding the tubular wall in a shape with an extending cavity; and then applying an elongated member to the tubular wall so that the tubular wall extends longitudinally.   12. The method of claim 11, wherein the elongate member is applied to extend around the tubular wall and longitudinally.   13. The method of claim 12, wherein the elongate member is applied to extend helically along the tubular wall with a pitch substantially equal to the pitch of the helical centerline.   14. A method according to claim 11, 12 or 13, wherein the step of holding the tubular wall at least partially helical comprises thermosetting the tubular wall.   15. A method according to any one of claims 11 to 14, wherein the elongate member is bonded to the tubular wall by a heating step.   16. A method as claimed in any one of claims 11 to 15, wherein the tubular wall is formed by winding around a mandrel.   17. The method of claim 16, wherein the mandrel has a spiral groove that at least partially receives the tubular wall.   16. A method according to any one of claims 11 to 15, wherein the tubular wall is formed by placing a helical mandrel therein.   19. A method according to claim 16, 17 or 18, wherein the elongate member is applied to the tubular wall when the tubular wall is supported by the mandrel.   20. A method as claimed in any one of claims 11 to 19, wherein the elongate member is applied to the exterior of the tubular wall.   Providing a mandrel having a spiral groove; providing a tubular wall having a longitudinally extending cavity; and at least partially defining the tubular wall such that the longitudinally extending cavity has a centerline that follows a spiral. Holding the tubular wall in a shape that is located in the groove and at least partially comprises the longitudinally extending cavity.

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