WO2017149322A1

WO2017149322A1 - Lumen constriction band

Info

Publication number: WO2017149322A1
Application number: PCT/GB2017/050579
Authority: WO
Inventors: James Matthew CORDEN; Gordon CARLSON; Ian James Hardman; Keith Patrick Heaton; Andy ALDERSON; David ASQUITH; Ahmed Shakeel
Original assignee: Salford Royal Nhs Foundation Trust
Priority date: 2016-03-03
Filing date: 2017-03-03
Publication date: 2017-09-08
Also published as: GB201603698D0

Abstract

Herein described is a lumen constriction band configured for constricting a lumen. The band is generally annular and is moveable from a first position in which the band is unexpanded to a second position in which the band is expanded so as to increase the a dimension of an aperture defined therein. Also described is method for joining bowel segments and an applicator for applying a lumen constriction band to a tissue segment. The applicator comprises a plurality of supporting members for supporting the band thereon, said supporting members being configured to move between a first position and a second position and a pusher operable to displace the lumen constriction band from said band supporting members.

Description

Lumen Constriction Band

Field of the Invention The present invention relates to a lumen constriction band configured for constricting a lumen. The present invention also relates to an applicator for applying a lumen constriction band to a lumen. The present invention further relates to a method which can be used to re-join bowel segments. Background of the Invention

Colorectal (or bowel) cancer is the third most common cancer in the UK, with approximately 35,000 new cases diagnosed each year. The majority of these colorectal cancers are caused by colonic polyps, small growths on the inner lining of the colon, which are extremely common, especially in the over 60s. Polyps are often harmless but can progress from benign to malignant growths, if left untreated.

Surgery is the main form of treatment for colorectal cancer, with approximately 80% of patients undergoing surgery at some point. This may be accompanied by chemotherapy and/or radiotherapy before and/or after surgery.

The type of surgery undertaken will depend on the stage of the cancer and where in the colon the tumour is located. If the cancer is at a very early stage (and therefore small in size), it may be removed using a colonoscope. In such surgery, a colonoscope is passed into the colon via the rectum and the tumour located. The tumour can then be excised and withdrawn from the colon. If the cancer is more advanced and is present in the large bowel, surgery usually involves removing a portion of the colon, and possibly also local lymph nodes. This type of surgery is known as a colectomy. Alternatively, where cancer is present in the rectum, an anterior resection may be used, in which all or part of the rectum is removed, usually with part of the sigmoid colon. An anterior resection also involves removal of the blood vessels and lymph nodes in this section of the bowel.

Traditionally, an anterior resection is performed via an incision made in the abdomen. Prior to removal of the bowel segment, the bowel is closed by linear stapling below the target section of bowel. The tumour and bowel segment are then removed and, if possible, the rectum and colon are re-joined to create an anastomosis. The anastomosis is either hand sewn or stapled using medical devices such as circular or linear staplers. Circular staplers generally consist of a staple 'gun' having two sections: an upper 'umbrella' head portion which is sutured into the upper bowel, and the lower 'gun' head portion which is inserted through the rectum. The lower head portion has a spike which is pushed through the rectal or lower bowel segment and inserted into the upper umbrella head portion. The spike is then retracted and in doing so the upper bowel segment is drawn to the lower bowel or rectal segment. Once the upper and lower segments of the bowel are positioned next to one another, the gun is activated to fire a circular staple line to join the two sections.

Anterior resection of the rectum accounts for 30% of all bowel cancer surgery and, as mentioned above, these operations are usually performed using stapling technology. However, there are a number of problems associated with this type of surgery. Firstly, the pelvis is a very narrow, confined space in which to work and suturing by hand can therefore be very difficult, especially if the tumour is positioned lower in the bowel. Secondly, the use of stapling technologies results in an increase in the occurrence of "dog ears".

Dog ears occur when stapling the rectum to the colon following removal of the tumour. As mentioned above, prior to removal of the tumour, the rectum is stapled using a linear stapler, often a double row linear stapler. When the tumour and bowel portion have been removed, a circular stapler is then used to the join the rectum with the colon. Dog ears, which are protrusions of rectal bowel tissue from the join, result from the joining of a cylindrical intestinal portion with a linearly stapled rectal portion.

Dog ears are associated with a number of complications. First, there is a mechanical weakness between the rectum and colon, as part of the rectal tissue has not been stapled to the colon. This results in an increased risk of failure of the staple line connecting the rectum and colon. Secondly, the tissue outside the staple line (the dog ears) may have an insufficient blood supply, which can result in the tissue becoming fragile and more susceptible to damage. Both of these problems are associated with an increased risk of anastomosis leaks, where bowel contents leak out of the bowel. Such leaks, which occur in 5-20% of stapled anastomosis, have a significant detrimental effect on the health of the patent and may result in increased mortality rates and increased length of hospital stays. Although leaks can sometimes be managed through use of antibiotics and/or a drain, if the leak is larger and peritonitis develops, a further surgical intervention may be required. Ileostomies or permanent colostomies are often required in such patients.

During surgical procedures there is often a need to constrict lumen other than the lumen of bowel, such as lumen of an artery or vein for example. When constricting such lumen (including the lumen of bowel segments) it is important that the constricting means can be stretched sufficiently to apply it to the portion of tissue defining the lumen and that once in position, it can apply a strong holding force to adequately constrict the lumen. It is an object of the present invention to obviate or mitigate one or more of the abovementioned disadvantages.

Summary of the Invention

According to a first aspect of the invention there is provided a lumen constriction band configured for constricting a lumen. The band is generally annular and in use is moveable from a first position in which the band is generally unexpanded to a second position in which the band is expanded to increase a dimension of an aperture defined by the band to allow application to a lumen.

The geometry and/or material properties of the band may be configured to allow the band to expand sufficiently to allow application to the lumen.

There are surgical procedures in which the constriction of a lumen, for example the lumen of a bowel segment, may be necessary. It will be appreciated that if a lumen is to be constricted during surgery, the constricting means should be easily applied and in addition, should provide a strong holding force, once in place. The present inventors have undertaken extensive experimentation to develop lumen constriction bands (in particular embodiments, bowel constriction bands) which can be stretched sufficiently for application to a segment of tissue, for example bowel tissue, and which exhibit a strong holding force once in place. As will be appreciated, it is advantageous if the constricting means remains in place and does not become disengaged from the segment of tissue during surgery as this may increase the risk of complications. By selecting appropriate band geometry and/or specific material properties of the lumen constriction band, the band may be sufficiently stretched to allow application to the tissue and, in addition, may exert a strong holding force on the tissue and may not be displaced or disengaged from the tissue segment.

In embodiments, the band has an aspect ratio of at least around 0.5. In developing the lumen constriction bands of the present invention, the inventors have found that bands having a particular aspect ratio surprisingly provide a lumen constriction band having improved gripping properties, improved holding strength on the bowel segment and an improved stretch during application.

The aspect ratio is defined by: r

Aspect Ratio =—

F Ri where r is the radius of the band and Ri is the inner radius of the band (see Figure 7A). Preferably the aspect ratio is between around 0.5 and around 1 .3, more preferably around 1 .2.

As will be appreciated by the skilled person, the lumen constriction bands according to the present invention could have any suitable cross section, for example a rectangular, square or triangular cross section. In embodiments, the band according to the abovementioned aspects of the invention is rectangular or square in cross section. During development of the lumen constriction bands of the present invention, it was surprisingly found that bands having a rectangular or square cross section provided the greatest grip on the tissue, for example a bowel segment, and exhibited the greatest resistance to rolling or flipping off the tissue. Therefore, by providing bands with such cross sections, the performance of the bands when on the tissue may be improved.

In embodiments, an edge of the band is bevelled thereby promoting controlled rolling or flipping of the band on application to the tissue, for example the bowel segment. As will be understood by the skilled person, the bevel should not encourage uncontrolled rolling or flipping of the band since the band must remain in position on the tissue to constrict the lumen. Rather, the bevel should allow the band to be rolled or flipped once. In lumen constriction bands which are made of different material types (see below) or where the geometry of the band differs such that different forces are applied in different configurations, the rolling or flipping of the band, aided by the bevel may enable a particularly strong holding force to be imparted on the tissue by the band when rolled.

In embodiments, the band is formed from at least two materials, the at least two materials exhibiting differing elastic properties. The present inventors have found that by developing a band formed of at least two materials with differing elastic properties, a band may be applied to the tissue with relative ease and in addition, exhibit a strong holding force once in place.

As will be appreciated by the skilled person, the term "at least two materials" includes embodiments where the at least two materials may be of the same type (but must exhibit differing elastic properties). For example, two polyurethane materials may be used which may have different elastic properties. Alternatively, the at least two materials may be chosen from different polymer types such as a polyurethane polymer and a silicon based polymer. In yet another embodiment, the at least two materials may be a first mixture or blend of polymers, for example, and a second mixture or blend of polymers.

The skilled person will appreciate that the term "elastic properties" is used to refer to a number of properties of the band, for example, elongation, tear resistance and tensile strength and/or Young's modulus.

In embodiments of the invention, the at least two different materials exhibit differing Young's moduli. For example, if the lumen constriction band is formed of two materials, one of the materials may have a greater Young's modulus than the other. As will be appreciated by the skilled person, Young's modulus, also known as elastic modulus, is a mechanical property of linear elastic solid materials and defines the relationship between stress and strain in a material. The Young's modulus, E, of a material can be calculated as follows:

_ tensile strength σ F/A₀ FL₀

extensional strain ε AL/L₀ A₀AL where E is the Young's modulus;

F is the force exerted on an object under tension;

A₀ is the original cross-sectional area through which the force is applied;

ΔΙ is the amount by which the length of the object changes; and

L₀ is the original length of the object.

For example, a first material of the band could have a low Young's modulus and a second material could have a high Young's modulus, the first material therefore demonstrating greater elasticity than the second material.

In embodiments, the band may comprise annuli of the at least two different materials running generally in parallel. In embodiments where the band comprises annuli of two different materials, the bevel (discussed above) may promote the band rolling or flipping once following application to the tissue such that an annuli of a first material faces outwards on application and an annuli of a second, different material faces outwards once in place on the tissue. The first outer-facing annuli may be formed of a material with an increased Young's modulus compared to the second inner annuli of material thereby permitting stretching of the band to increase the circumference of the aperture therein during application. This band may then be rolled or flipped once following application so that the material with a higher Young's modulus is positioned on the outer surface of the band. The band therefore exhibits a stronger holding force in this configuration.

As will be understood by the skilled person (and as mentioned above), the bevel should not encourage uncontrolled rolling or flipping of the band since the band must remain in position on the tissue to constrict the lumen. Rather, the bevel should allow the band to be rolled or flipped once to change the configuration of the materials, to enable a strong holding force to be imparted on the tissue by the band.

In an alternative, the band may comprise discrete sections of the at least two different materials. In such an embodiment, the stretching of the band may be performed in a certain direction such that only the material with increased elasticity (and lower Young's modulus) is stretched. A second material having a reduced elasticity (and a higher Young's modulus) then provides a strong holding force once the band is positioned on the bowel segment.

Also provided is a lumen constriction band configured for constricting a lumen wherein the band is generally annular and in use is moveable from a first position in which the band is generally unexpanded to a second position in which the band is expanded to increase a dimension of an aperture defined by the band so as to enable application to a bowel segment; and wherein the band is formed from a liquid crystalline elastomer. LCEs combine the self-organisational property of liquid crystals with the large strain elasticity of polymeric elastomers to allow controllable and reversible shape/dimensional change in response to various external stimuli (for example temperature, electric field, light). For example, as a nematic LCE cools, the initial random coil conformations of the polymer chains in the isotropic phase become aligned in the nematic phase such that the material increases in length. Depending on the architecture of the LCE, change in length up to 400% can be achieved during the shape transition. Using such an LCE, a bowel constriction band could be applied to the bowel in an extended state at a low temperature and would then contract to a shorter state at body temperature, thereby providing an improved hold once in place on the bowel segment.

As will be appreciated, in embodiments the band may comprise annuli of at least two different materials running generally in parallel. In such embodiments, one of the annuli may be an LCE, for example with a second annuli being a non-LCE elastomer. For example, an outer annuli may be formed on an LCE and an inner annuli may be formed by a non-LCE elastomer. Such a band may be applied at low temperatures, when the band may be more easily extended and once in position (at body temperature) would apply a strong gripping/holding force. In other embodiments the band may comprise multiple annuli of LCEs, the LCEs having differing elastic properties.

Also provided is a lumen constriction band configured for constricting a lumen wherein the band is generally annular and in use is moveable from a first position in which the band is generally unexpanded to a second position in which the band is expanded to increase a dimension of an aperture defined by the band so as to enable application to the lumen; and wherein the band defines a generally circular aperture having radius Ri and a generally circular cross section of radius r; and wherein the band has an aspect ratio of at least around 0.5, wherein the aspect ratio is defined as Preferably the aspect ratio is between around 0.5 and around 1 .3, more preferably around 1 .2.

As mentioned above, during development of the bands of the present invention the inventors surprisingly found that developing bands with a particular aspect ratio resulted in an improved holding strength when positioned on the tissue and improved stretching during application.

In embodiments, the band according to the abovementioned aspects of the invention is textured. For example, the band may comprise a textured surface (for example, created during moulding of the band) or may have an additive within the material from which the band is fabricated to increase the surface roughness of the material. This may prevent unwanted movement of the band once positioned on the tissue and may increase a coefficient of friction between the band and the tissue to which the band is applied.

As mentioned above, the lumen to be constricted could be a lumen of a bowel segment, in which case the lumen constriction band is a bowel constriction band. Alternatively, the lumen could be that of an artery or vein, for example.

In embodiments, the bands according to the abovementioned aspects of the invention are configured for use with the applicator as described in the third aspect of the invention.

There is also provided a method comprising constricting a lumen defined by a section of tissue; resecting a portion of tissue adjacent the constriction to form a first segment of tissue having a closed end thereof, and a second segment of tissue having an open end; guiding a projecting member through the lumen of said constricted portion of the first segment of tissue such that said projecting member projects out of the closed end of the first segment of tissue;

applying a lumen constriction band around said first segment of tissue to gather a portion thereof that is adjacent said closed end around said projecting member;

fastening said first and second segments of tissue to one another; and removing said resected tissue and said lumen constriction band from said tissue.

The skilled person will appreciate that the tissue may be bowel tissue or tissue of an artery or vein for example.

According to a second aspect of the invention there is provided a method comprising: constricting a lumen of a bowel;

resecting a portion of the bowel adjacent the constriction to form a first bowel segment having a closed end thereof, and a second bowel segment having an open end; guiding a projecting member through the lumen of said constricted portion of the first bowel segment such that said projecting member projects out of the closed end of the first bowel segment;

applying a bowel constriction band around said first bowel segment to gather a portion thereof that is adjacent said closed end around said projecting member;

fastening said first and second bowel segments to one another; and

removing said resected bowel tissue and said bowel constriction band from said bowel. As will be appreciated by a person skilled in the art, the order in which the above steps are recited does not necessarily correspond to the order in which the steps must be performed.

The method of the present invention can be used to re-join bowel segments, for example during anastomosis surgery. By gathering the stapled or sutured bowel tissue around the projecting member using a bowel constriction band (which, as described herein, have been shown to be particularly beneficial) the shape of the first bowel segment may be generally complimentary to the shape of the second bowel segment. As a consequence, when the two bowel segments are fastened to one another, the formation of dog ears may be avoided.

The method of the present invention utilises the projecting member as a guide around which the bowel can be gathered. The use of the projecting member as a guide may allow the bowel to be gathered evenly, which may assist the surgeon or medical practitioner during surgery. As will be appreciated by the skilled person, the projecting member is guided through the constricted lumen of the bowel. The projecting member may not be positioned entirely though the lumen. For example, the projecting member may be guided through the lumen and may pass through or pierce a small portion of bowel tissue. However, it is to be understood that the guiding of the projecting member so that it passes through or pierces bowel tissue should be avoided where possible, since if bowel tissue is pierced by the projecting member, this may result in an increased risk of bowel tear. Preferably, the projecting member is guided through the lumen such that the projecting member does not pierce bowel tissue. In embodiments, the method may further comprise attaching a second projecting member to said second bowel segment such that said second projecting member projects out of said open end of said second bowel segment. The attaching of the second projecting member may include gathering a portion of the second bowel segment adjacent said open end around said projecting member.

In embodiments said first and/or second projecting members further comprise generally complementary shaped guiding plates. In embodiments, the guiding plate(s) may be generally circular.

The presence of generally complementary guiding plates may further assist the surgeon in producing two bowel segments of complementary shape for re-joining. This may further limit the formation of dog ears. In embodiments, said first and second projecting members (and/or guiding plates) comprise portions of a circular stapler. The skilled person will be well aware of suitable circular staplers as are used during such surgery. As discussed below, the inventors utilised a number of different sized circular staplers during development of the method of the present invention.

In embodiments, the method further comprises locating said first and second bowel segments adjacent one another prior to the step of fastening said first and second bowel segments to one another. Said locating of said first and second bowel segments adjacent one another may be achieved by engagement of said first and second projecting members. For example, in embodiments where the first and second projecting members form part of a circular stapler, the skilled person will appreciate that the two projecting members are engagement and, once engaged, can be used to draw the two bowel segments together for fastening. In embodiments of the invention, said step of constricting the lumen of the bowel comprises stapling or suturing the bowel, optionally linearly stapling the bowel. Linear stapling may offer the advantage of quickly and securely constricting the lumen of the bowel therefore enhancing surgical efficiency and reducing the risk of leaks during the procedure. In embodiments, said step of resecting a portion of bowel adjacent the constriction comprises resecting a portion of bowel above said first bowel segment. The first bowel segment may be a lower rectal bowel segment. For example, in surgery to produce anastomosis, the lower portion of bowel, which is in communication with the rectum, is constricted by stapling or suturing (or by other means, for example cauterisation). The skilled person will appreciate that a rectal bowel segment does not need to be a bowel portion located adjacent to the rectum, but rather, a segment of bowel in communication with (and not resected from) the rectum. In embodiments, the fastening of said first and second bowel segments together comprises stapling said first and second bowel segments together. In embodiments, the stapling is performed by a circular stapler. As will be appreciated, the stapling of said first and second bowel segments may allow a strong join to be formed between the two bowel segments. This may reduce the risk of post-operative complications through failure of or leaking at the join, for example. Stapling of the first and second bowel segments is also much quicker than suturing, for example, therefore improving the efficiency of the procedure.

The method may further comprise withdrawing said first and second projecting members from the bowel.

In embodiments of the method said bowel constriction band may be in accordance with the lumen constriction band of the abovementioned aspects of the invention. As described above, the lumen constriction bands of the present invention have been developed by the inventors for use in the constricting of tissue segments, particularly for use in re-joining bowel segments, for example during surgery to create anastomosis.

According to a third aspect of the invention there is provided an applicator for applying a lumen constriction band to a lumen, the band defining an aperture therein for receiving a tissue segment. The applicator comprises a plurality of band supporting members. In use the band supporting members are received within the aperture defined by the band, said supporting members being moveable between a first position in which the band supporting members are close together and a second position in which the band supporting members are further apart such that the aperture defined by the band is expanded to increase a dimension of the aperture. The applicator further comprises a pusher operable to displace the lumen constriction band from said band supporting members. The applicator of the present invention has been developed by the present inventors to apply a lumen constriction band to a lumen, in particular a bowel constriction band to a portion of a bowel segment during surgery, for example during anastomosis surgery. The band supporting members being moveable from a first to a second position allows the band to be inserted into the body in an unexpanded state before being stretched within the body. The band can be inserted into the body with the band supporting members in the first position and the band therefore being under little or no stress. When the band supporting members move to the second position, a dimension of the aperture defined by the band increases so that the band can be applied around a bowel segment more easily. For example, if the band is generally circular, a circumference of the aperture may increase. In addition to reducing the amount of time that the lumen constriction band is under stress, the presence of a first position, in which the band is generally unexpanded allows the applicator, when inserted into the body, to occupy less space (since when in the second position, the band supporting members may be more splayed to enable the band to stretch, therefore occupying more space). This can reduce the risk of damage when inserting the applicator. Once the lumen constriction band is positioned around the tissue, a pusher is operated to displace the lumen constriction band from the band supporting members. As will be appreciated by the skilled person, the pusher may be operated while the band supporting members are in the second position. Alternatively, the band supporting members may be in the first position when the pusher is operated. The presence of the pusher allows the lumen constriction band to be removed from the applicator without the insertion of additional instruments into the surgical working area.

In embodiments, said supporting members are arranged to pivot between said first and second positions. For example, the supporting members may be elongate and may be arranged to pivot around one or more pivot point at one end of the supporting members. Alternatively, the entirety of one or more of the supporting members may move to the second position through translational motion. The applicator may comprise a plurality of said pushers, each of said pushers being supported on a corresponding band supporting member. The presence of a pusher on each band supporting member may improve the control in removing the lumen constriction band form the band supporting members, for instance preventing the band from springing off one supporting member while still firmly supported by another.

In embodiments, the pusher or pushers are moveable between a resting position and an actuating position wherein the pusher or pushers are arranged such that movement from said resting position to said actuating position results in the pusher displacing a lumen constriction band from said band supporting members. For example, the pushers may be located within a groove, and may be slideable within that groove from the resting position in which the pushers do not impart a pushing force on the band (when in use) to the actuating position in which the pushers impart a pushing force on the band and thereby displace the band from the band supporting members.

The pusher or pushers may be biased towards resting position. The pusher or pushers may be biased towards the resting position by a resilient element. The resilient element may be a spring, for example a coil spring, gas spring, volute spring or stack of Belleville washers. In a preferred embodiment the pusher or pushers are biased by a coil spring. Alternatively or in addition, the pusher or pushers may be biased towards the resting position by a different type of resilient member such as an elastomeric tube, rod or block.

In preferred embodiments, the spring or other resilient member may be arranged to be compressed. However, the skilled person will understand that in other embodiments the resilient member may be arranged to be stretched or to undergo torsional strain.

Each pusher may be moveable between its resting and actuating positions independently of the other pushers. The ability to move the pushers independently may allow the surgeon or medical practitioner to manipulate the various portions of the band supported on different band supporting members independently, which may allow for more precise positioning of the band on the bowel segment. Such independent movement of the pushers may also allow for improved controllability when positioning the band on the bowel segment. Alternatively, the movement of each pusher from the resting position to the actuating position may be coordinated. For example, the pushers may be connected to a single rod or other component which when moved by a surgeon or medical practitioner results in movement of the pushers.

In embodiments, each band supporting member has a shoulder against which said band is locatable. The presence of the shoulder on each band supporting member may allow the lumen constriction band to be precisely positioned on the band supporting member and may prevent unwanted movement of the band along the band supporting member in use. The supporting members may be elongate. In such embodiments, the shoulder may be positioned at a distal end of said elongate supporting member.

In embodiments the applicator comprises only two band supporting members. As will be appreciated by the skilled person, the movement of the band supporting members from the first position to the second position, which increases a dimension of the aperture defined by the band, results in an increased volume occupied by the applicator. By having only two band supporting members, the increase in volume is reduced compared to an applicator with three band supporting members, for example. This may reduce the working space required in the body whilst still allowing the aperture of the band to be increased for placement around the bowel portion.

The applicator may further comprise an actuating member arranged to effect movement of said supporting members from said first position to said second position. In embodiments, rotation of the actuating member may cause the band supporting members to move from said first position to said second position. The actuating member may be spaced from said band supporting members. The presence of an actuating member spaced from the band supporting members may allow the surgeon or medical practitioner to operate the band supporting members quickly and easily, externally of the patient's body, while the band supporting members are located within the body. For example, in one embodiment (described more fully below) the applicator may consist of an elongate cylindrical housing having band supporting members located at a first end and an actuating member located at a second end, the second end being located outside the body during use. The skilled person will appreciate that the actuating member need not be entirely outside the body during use but may be located towards the outside of the body such that operation of the actuator by the surgeon or medical practitioner is less difficult.

In embodiments in which the actuating member is spaced from the band supporting members there may be provided a drive mechanism located between said actuating member and said supporting members. The drive mechanism may comprise an elongate rod. In such embodiments, the elongate rod may threadedly engage the actuating member and co-operatively form a lead screw mechanism. As mentioned above, the applicator may comprise an elongate cylindrical housing. In such embodiments, the main body may have a width of around 15 mm or less. Such a size is suitable for insertion into a port made in the body during surgery.

In embodiments, at least a portion of the applicator may be fabricated from stainless steel. For example, the elongate cylindrical housing may be fabricated from stainless steel.

According to a further aspect of the invention there is provided a kit of parts comprising an applicator according to the third aspect of the invention and a lumen constriction band according to the invention.

According to a yet further aspect of the invention there is provided a kit of parts for the applicator according to the third aspect of the invention. According to a yet further aspect of the invention there is provided the use of a lumen constriction band according to the invention in joining resected bowel segments.

There is also provided the use of an applicator according to the third aspect of the invention in the application of a lumen constriction band according to the invention to a bowel segment.

Detailed Description of the Invention

The present invention will now be described with reference to the following non-limiting examples and figures, which show: Figure 1 : Stages in a prior art method of removing a portion of bowel tissue and rejoining bowel segments; Figure 2: Stages in a method of re-joining bowel segments according to an embodiment of the present invention;

Figure 3: Stages in a method of re-joining bowel segments according to an embodiment of the present invention;

Figure 4: Bowel constriction bands, some being embodiments of the present invention;

Figure 5: Stages in testing methods for bowel constriction bands. A: Schematic showing rolling testing protocol. B: Schematic showing pull-through testing protocol;

Figure 6: Bowel constriction bands according to embodiments of the present invention;

Figure 7: A: A segment of a bowel constriction band used for simulation. Surface regions marked with numbers are used to apply forces on the band. B: Loading and boundary conditions used during simulation;

Figure 8: A deformed cross-sectional shape of bowel constriction band of Figure 7A showing displacement calculation; Figure 9: A plot showing the correlation between hoop stress and radial stretch ratio for a range of aspect ratios of bowel constriction band;

Figure 10: A plot showing the correlation between hoop stress and stretch ratio for aspect ratio of 0.757 for a bowel constriction band;

Figure 11 : A bowel constriction band in accordance with an embodiment of the present invention;

Figure 12: An applicator for applying a bowel constriction band to a bowel segment, in accordance with an embodiment of the present invention; Figure 13: An applicator for applying a bowel constriction band to a bowel segment, in accordance with an embodiment of the present invention; Figure 14: An applicator for applying a bowel constriction band to a bowel segment, in accordance with an embodiment of the present invention; and

Figure 15: An applicator according to an embodiment of the present invention being used to apply a bowel constriction band to a bowel segment during anastomosis surgery.

Referring now to Figure 1 , there is depicted a prior art method of removing a portion of bowel tissue and subsequently re-joining the bowel segments. A tumour 1 is present on a portion of the bowel 3 of a patient (not shown) (Figure 1A). During surgery to remove the tumour 1 , a linear stapler 5 is used to close the lumen (not shown) of the bowel 3 beneath the tumour 1 (Figure 1 B). A target section 7 of the bowel 3 containing the tumour 1 is removed by dissection with a scalpel 9, for example (Figure 1 C). An upper 'umbrella' portion 1 1 of a circular stapler is sutured into the upper bowel segment 13 (Figure 1 D). A lower gun portion 15 of the circular stapler is inserted into the stapled rectal segment 17 and a spike portion 19 of the circular stapler which is attached to the lower gun portion 15 is inserted through the stapled rectal segment 17 (Figure 1 E). The spike portion 19 of the circular stapler is inserted into the umbrella head 1 1 of the circular stapler (Figure 1 F) and the umbrella head 1 1 is then drawn into the lower gun portion 15, thereby bringing the upper bowel segment 13 and the lower rectal segment 17 together (Figure 1 G). The circular stapler is then activated to staple the upper and lower segments 13, 17 together. Once the two segments 13, 17 have been stapled, a circular blade within the lower gun portion 15 cuts the tissue within the staple lines, thereby creating an unobstructed lumen. The end result is a circular stapled bowel and rectum. However, since the linear staple line of the rectum is longer than the diameter of the circular cutter and staple line, two segments of tissue 21 , 23 remain outside the join (Figure 1 H); these are known as 'dog ears'.

As discussed above, dog ears are associated with a number of complications. First, there is a mechanical weakness between the rectum and colon, as part of the rectal tissue has not been stapled to the colon. This results in an increased risk of failure of the staple line connecting the rectum and colon. Secondly, the tissue outside the staple line (the dog ears) may have an insufficient blood supply which can result in the tissue becoming fragile and more susceptible to damage. Both of these problems are associated with an increased risk of anastomosis leaks, where bowel contents leak out of the bowel. Such leaks, which occur in 5-20% of stapled anastomosis, have a significant detrimental effect on the health of the patent and may result in increased mortality rates and increased length of hospital stays. Although leaks can sometimes be managed through use of antibiotics and/or a drain, if the leak is larger and peritonitis develops, a further surgical intervention may be required. Ileostomies or permanent colostomies are often required in such patients.

Referring now to Figure 2, there are shown images of prototype testing of a method of re-joining bowel segments according to an embodiment of the present invention. During testing of the method of the present invention, a double-layer silicon bowel (purchased from Limbs & Things) was used. The bowel is 30 mm in diameter and has a thickness of approximately 2.5 mm. Similar to the prior art method shown in Figure 1 , the lower rectal segment 17 of the Limbs and Things bowel was stapled to create a linear staple line 25 (Figure 2A). Such linear stapling seals the lower rectal segment 17 of bowel. A spike portion 19 (or projecting member) of a Covidien EEA Circular Stapler (31 mm diameter; not shown) was then guided through the staple line 25 (Figure 2B). Once the spike portion 19 was in place a bowel constriction band 27, for example a bowel constriction band according to the present invention, was applied to circumferentially surround the lower bowel segment 17 and to cinch or constrict the bowel around the spike 19 (Figure 2C). In this way, the spike 19 acts as a guide around which the bowel is gathered.

In this testing protocol, an upper bowel segment was not used. However, similar to the prior art method shown in Figure 1 , if an upper bowel segment were present, an umbrella portion 1 1 of the circular stapler would be sutured into the upper bowel. In this testing protocol, the umbrella portion 1 1 is not inserted into an upper bowel segment but the spike portion 19 of the circular stapler is inserted into the umbrella portion 1 1 of the circular stapler (Figure 2C). The umbrella portion 1 1 is then drawn into the lower gun portion (not shown) thereby bringing the umbrella portion 1 1 (which in use would be attached to an upper bowel segment) and the lower rectal segment 17 together (Figure 2E). As can be seen in Figure 2D, due to the constriction of the bowel 17 with the bowel constriction band 27, no dog ears protrude radially outward of the umbrella portion 1 1 unlike when the method shown in Figure 1 is used.

Referring now to Figure 3, there is shown images of prototype testing of a method of re-joining bowel segments according to an embodiment of the present invention. During this testing protocol, 1 m of porcine bowel tissue from a 28 kg pig (from the Royal Veterinary College, University of London) was used. The bowel tissue included both the rectum and fatty tissue. Part of the bowel was excised from the remainder and the umbrella portion 1 1 of a 25 mm circular stapler was sutured into this "upper segment" 13 of bowel using a purse suture (see Figure 3A). The "lower segment" 17 of the bowel was linearly stapled (not shown) using an Ethicon Proximate Linear Stapler. The gun portion (not shown) of the circular stapler was inserted through the rectum and into the bowel, and a spike portion (or projecting member) 19 advanced through the staple line (Figure 3A). A bowel constriction band 27, for example a lumen constriction band according to the present invention, was applied over the linear staple line around the spike portion 19, thereby constricting or cinching the bowel 17 around the spike portion 19. As is shown in Figure 3A, the bowel constriction band 27 cinched the bowel 17 evenly, and the bowel 17 was forced over the edge 29 of the circular stapler, thereby creating an even stapling surface.

The umbrella portion 1 1 of the circular stapler was then connected to the spike portion 19 (Figure 3B) and the spike 19 retracted to bring the upper and lower portions of the bowel 13, 17 together (Figure 3C). The circular stapler was deployed to join the bowel segments 13, 17 together. When the upper and lower portions of the bowel 13, 17 were joined, the bowel formed a smooth joint surface with no dog ears (Figure 3C).

Following stapling of the two bowel segments 13, 17 together, a cutter (not shown) on the circular stapler was used to cut through the bowel tissue within the circular staple line. This resulted in production of a 'doughnut' of bowel tissue 31 along with the bowel constriction band 27 (shown in Figure 3D) which was removed from the re-joined bowel with the circular stapler, thereby opening the lumen of the bowel.

During development of the methods and bands of the present invention, the inventors performed testing of various band geometries, materials and surface properties. A number of band profiles were manufactured for testing (shown in Figure 4). A selection of polyurethane rubbers and silicon were selected and the band profiles shown in Figure 4 manufactured from these materials. The components material properties and performance of the bands was tested and the results are shown in Table 1 .

Table 1 - Material Selection Test

Following assessment of the material properties and performance, the inventors proceeding with further testing using Polytek 74-29 flexible PU rubber which provided the best combination of elongation, tear resistance and tensile strength.

The ability of the bowel constriction bands to constrict and remain on the bowel during surgery is dependent upon a number of variables including the cross sectional profile of the band, the dimensions of the band (e.g. internal diameter and thickness), the bulk material properties of the band (e.g. tensile strength and elongation), and the surface material properties of the band (e.g. surface hardness, texture, tackiness and the coefficient of friction between the band and the bowel). The inventors undertook testing to evaluate which cross section of band results in the greatest resistance to rolling and which band provides the greatest resistance to axial movement of the bowel through the band.

Test 1: Evaluation of resistance to rolling

A cone C manufactured from acetal, a polymer with a very low coefficient of friction, was produced to test the various bands' resistance to rolling (which is undesirable in bowel constriction bands as it can allow the band to roll out of position). A suspended tufnol plate P with a 15 mm tapered hole H was used and the cone C fitted into it (see Figure 5A). The cone C was retained in the plate P using a bowel constriction band B. A force meter was then used to press on the cone tip to force the cone C through the band B until it fell through the plate P. At this point the maximum pushing force was recorded. Each band was tested three times. The results are shown in Table 2.

Table 1 - Resistance to Rolling Testing

The test results show that the profile demonstrating the highest resistance to rolling was the rectangular cross section (band profile E), followed by the square (C) and circular (A) cross sections. The success of the rectangular cross section is likely due to the aspect ratio of the band (ratio of height to diameter) which will reduce the propensity of the band to flip inside out, and the increased surface area of the band in contact with the bowel compared to other cross sections. These factors could be further optimised by increasing the stiffness of the band in its axial direction and increasing the depth of the band (although this would ultimately be limited by the space available within the circular stapler to accommodate the band).

Test 2: Evaluation of pull through force

A second test was designed to evaluate which band provided the greatest grip on the bowel. Using the same plate P, a bowel substitute S was fed through the hole H with the band B placed around the bowel, above the plate P. The bowel was pulled from below using a force meter with the intention of dragging the bowel through the band until released from the plate (see Figure 5B). The band was placed over the bowel such that there was always 25 mm of bowel substitute extending above the band. It was anticipated that this would distinguish between movement due to the band simply rolling off the end of the bowel (as tested in Test 1 ) and movement due to the bowel sliding through the band. The maximum pulling force was recorded and each band was tested three times. The results are shown in Table 3. Table 3 - Pull Through Testing

When comparing the mean forces to pull the bowel through the bands, it can be seen that the square profile (C) and the tall rectangular profile (E) performed the best with 15.80 N and 15.98 N average maximum forces respectively. Interestingly there was little difference between them in this test compared to test 1 where the tall rectangular profile was significantly better. Test 3: Evaluation of resistance to rolling

Next, the inventors sought to compare the effect of the internal diameter of the rings. Bands of the same general shape as profile E but with varying internal and external diameters were manufactured (see Figure 6) and the testing repeated to determine whether a difference in band performance was observed. To test the roll of force of the bands, the same methods as used in Test 1 were adopted. Band profile E was used as a control due to different climate conditions. The results are shown in Table 4.

Table 4 - Resistance to Rolling Testing

Comparing the average maximum pushing between the different band sizes, it can be seen that the 2 mm wall section bands of the 012x8 (E1 ) 010x6 (E3) performed the worst, closely followed by the 010x4 (E4) band. The poor performance of this band is likely due to the fact that it is necessary to expand the band by a higher proportion compared to the other bands, due to its smaller original internal diameter. It can therefore be concluded that the wall thickness has a direct effect on the gripping of the band on the cone. With a greater wall thickness, there is more material to apply a 'spring' force to resist rolling of the band.

The highest average pushing force was withstood by the original 014x8 (E) band, closely followed by the 012x6 (E2) band. Both of these bands have a 3 mm wall thickness.

Test 4: Evaluation of pull through force

To test the pull through force of the bands, the same methods as Test 2 were adopted. Due to the warmer climate conditions, the original E band was tested as a control. The results are shown in Table 5.

Table 5 - Pull Through Testing

The highest average maximum pulling force was withstood by the original 014x8 (E) band. The difference between the pulling forces was not particularly large and considering the other variables such as potential variation in the bowel substitute and the manual pulling of the bowel, this is not a difference that enables selection of one band size over another.

Test 5: Evaluation of textured bands

To determine whether there is any benefit to having textured additives to the band material, a polyurethane mix of Polytek 74-29 Flexible PU Rubber and coarse sand was produced. E-E5 Bands were manufactured with this material and the pull through test described above was conducted. The results are shown in Table 6. Table 6 - Pull Through Testing with sand additive

The introduction of an abrasive additive into the polyurethane mix generally increases the average maximum pulling force that a band can withstand. The bands with the sand grains embedded provided a higher resistance to dragging against the bowel substitute. This is an expected result as the sand increases the surface coefficient of friction.

Numerical simulation for bowel constriction bands

In further studies, the effects of cross-sectional geometry and mean diameter on the potential clamping strength of polymeric bands was modelled. A quarter model of a circular band was simulated, the boundary conditions being selected to be representative of the conditions experienced during application of the band.

Two matrices of geometries were used: one with a varying aspect ratio and one with a fixed aspect ratio. The rubber band was modelled in Ansys, taking advantage of the band's two planes of symmetry which allowed its geometry to be reduced to a quarter, as shown in Figure 7A. The aspect ratio is defined by: r

Aspect Ratio =—

F Ri where r is the radius of the band and Ri is the inner radius of the band (see Figure 7A). In Figure 7A dimension H is used to imprint the surfaces of the rubber band to create surface segments which are selectable for applying force. The value of H is varied so that the ratio ^ is always constant. This ensures that the areas where the force is applied always bear a constant ratio with diameter of the rubber band.

Loading and Boundary Conditions

Boundary conditions play an important role in FE simulation. Figure 7B depicts differing boundary conditions. Two frictionless supports have been applied to depict the two planes of symmetry in the model. The most important boundary condition (as shown in Figure 7B) is the displacement boundary condition which restricts displacement of the mid-plane inside edge (E) along the z-axis. Constraint E helped in simulation convergence by eliminating unrealistic displacement in the z direction. Force is applied on six circumferential segments, marked in circles of Figure 7A. Figure 7A shows three circle faces, the other three being located symmetrically below the mid- plane inside edge.

The recommended element type for hyperelastic materials is tetrahedrons. Some mesh improvement around the boundary edges at the point of force application was seen and helps convergence of the simulation but otherwise has little effect on the results.

Three mesh sizes exist in Ansys: coarse, medium and fine. Changing mesh size from coarse to medium results in improvement of the results without increasing simulation run time greatly. However, use of a fine mesh significantly increases run time without significant improvement in results. The medium mesh size was therefore use for all simulations.

Results

As the force has to be applied on a portion of surface so that the Ansys model can be converged, there are minimum and maximum displacements on the model. These are shown in Figure 8. Maximum displacement values are used throughout and the results are described below. The graphs are plotted as hoop stress vs stretch ratio, stretch ratio being defined as follows: AR_C + R_c

Stretch ratio, λ =

Stretch ratio is equivalent to radial or diametric strain. AR_C is the average stretch at a particular stress level. Two sets of results were obtained: one in which the aspect ratio of the bowel constriction band was varied and another in which the aspect ratio remains constant and the band radius r and inner radius Ri are increased.

Three positions of the bowel constriction band are defined: a) Neutral position: When the rubber band is not in use;

b) Application position: When the rubber band is stretched and is ready to be applied to the bowel;

c) Holding position : Final position when the rubber band is holding the bowel portion closed.

The application and holding positions are shown in the results described below.

Test 6: Effect of aspect ratio on hoop stress and stretch ratio

Table 7 shows the variation of aspect ratio used during testing.

Table 7 - Variation of aspect ratio with radius of bowel constriction

As shown in Figure 9, increasing the aspect ratio of the bowel constriction band from 0.520 to 1 .213 surprisingly increases the holding load by 94% and the application load by 28%. There is therefore a benefit in using higher aspect ratio bowel constriction band. Test 7: Effect of band dimensions on hoop stress and stretch ratio

Table 8 shows the various band dimensions used during testing.

Table 8 - Variation of bowel constriction band dimensions

As shown in Figure 10, using a rubber band of increased r and Ri improves the characteristics of the band in the application and holding positions. Materials Investigation

The bowel constriction bands should be formed of a material that has a low modulus of elasticity when stretched linearly, with the circumferential neutral axis of the band being able to withstand strains in excess of 200%, and a high modulus of elasticity when stretched radially, with the circumferential neutral axis of the band being able to withstand strains in the range of 10 to 40%. These requirements point towards the use of elastomeric materials.

As described above, testing of bowel constriction bands formed of polyurethane rubbers and silicon has been undertaken. Liquid crystalline elastomers (LCEs) represent another potential material which could be used for the production of the bowel constriction bands according to the invention. LCEs combine the self- organisational property of liquid crystals with the large strain elasticity of polymeric elastomers to allow controllable and reversible shape/dimensional change in response to various external stimuli (for example temperature, electric field, light). For example, as a nematic LCE cools, the initial random coil conformations of the polymer chains in the isotropic phase become aligned in the nematic phase such that the material increases in length. Depending on the architecture of the LCE, change in length up to 400% can be achieved during the shape transition. Using such an LCE, a bowel constriction band could be applied to the bowel in an extended state at a low temperature and would then contract to a shorter state at body temperature.

The Young's moduli of LCEs are typically of the order of MPa, and this can be varied by controlling the cross-link density. For deformation over the entire band, the LCE needs to be a monodomain or have a well-defined director pattern over the whole sample.

The nematic-isotropic phase transition can also be triggered by application of an electric field.

Smectic A LCEs, having a layered or lamellar structure, possess highly anisotropic mechanical properties and display rubbery elasticity in the two directions of the layer planes and hard conventional solid behaviour in the third dimension. Smectic LCEs can display shape variation associated with the transition to the isotropic phase up to around 200%.

The use of these materials for forming bowel constriction bands would result in a band which could be stretched during application but which would also apply a strong holding force on the bowel, once positioned.

Another approach used to achieve the above desirable properties makes use of a bowel constriction band formed from at least two materials, the two materials exhibiting different properties. For example, referring to Figure 1 1 A, the bowel constriction band 33 is generally annular in shape and is formed of parallel annuli of first 33a and second 33b materials. In this example, the first material 33a has increased elasticity compared to the second material 33b. Therefore, when the bowel constriction band is stretched radially (i.e. when applying the band to the bowel segment), the increased elasticity of first material 33a allows stretching of the band 33 so that the band 33 can be more easily applied to a bowel segment. An edge of the bowel constriction band is bevelled, so that when applying the bowel constriction band to the bowel segment 'flipping' or 'rolling' of the band to the configuration shown in Figure 1 1 B is promoted. In the second configuration, the second material 33b is the outer annuli. The second material 33b is formed of a material having a reduced elasticity, and therefore, when in position on the bowel, the band is more resistant to stretching and applies a strong holding force. During testing of the methods and bands of the present invention, the present inventors performed comparative testing of a method of re-joining bowel segments using surgical cable-ties to constrict the bowel tissue of a lower bowel portion. However, unlike the use of bowel constriction bands, the surgical cable-ties did not apply an evenly distributed force to the bowel tissue which resulted in the bowel tissue gathering unevenly. As the cable-tie was tightened, a single fold in the bowel formed, rather than multiple creases, as observed when bowel constriction bands were used. This made stapling difficult, due to the thickness of the bowel tissue present. In addition, the presence of such a single fold may result in healing problems similar to those associated with dog ears. In addition, the use of cable-ties may cause difficulty during surgery, since the cable-ties are less reversible than the bands of the present invention. For example, in the case that a cable-tie is applied and does not cinch the bowel appropriately, the cable-tie must be removed by cutting the cable-tie. Such cutting may result in damage to the bowel segment.

Referring now to Figure 12, there is depicted an applicator, for applying a bowel constriction band to a bowel segment, in accordance with an embodiment of the present invention. The applicator may be used to apply a bowel constriction band as described above to a bowel segment. The applicator 35 has two band supporting members 37, 39 which, in this embodiment, are elongate. Each band supporting member 37, 39 is connected to a corresponding handle portion 41 , 43 by which the applicator 35 can be held by a medical practitioner. The two elongate band supporting members 37, 39 are pivotally connected to each other, in this particular case by a single mutual pivot point 45. Movement of the handles 41 , 43 from a first position (see Figure 12A) to a second position (see Figure 12B) results in the tips of the band supporting members 37, 39 furthest from the pivot 45 splaying apart. A bowel constriction band 47 positioned on the applicator therefore changes during this movement from a generally unexpanded state to a stretched state in which a dimension of an aperture defined by the bowel constriction band 47 expands.

Positioned on the band supporting members 37, 39 distal from the handles 41 , 43 are band adapters (in this case band supporting shoulders) 49, 51 on which a bowel constriction band 47 is located (see Figure 12C). Pushers 53, 55 are located on each elongate band supporting member 37, 39. The pushers 53, 55 are moveable between a resting position (see pusher 53) and an actuating position (see pusher 55). Movement of a pusher 53, 55 to the actuating position results in that pusher 53, 55 displacing the bowel constriction band 47 from the associated band adapter 49, 51 . Referring now to Figures 13 and 14 there is depicted an applicator for applying a bowel constriction band to a bowel segment in accordance with a further embodiment of the present invention. The applicator may be used to apply a bowel constriction band, as described above, to a bowel segment. In this embodiment, the applicator 57 comprises an elongate cylindrical stainless steel main housing 59, the housing 59 extending along an axis 59a (as depicted in Figure 13B). It will be appreciated that, in the following description, an axial direction refers to a direction along or parallel to the axis 59a of the housing 59. Similarly, a radial direction refers to a direction perpendicular to the axis and which passes through the axis 59a. The cylindrical main housing 59 has a diameter of around 15 mm so that it can comfortably fit through a port in a body of a subject, during use. The main housing 59 has a through bore extending from first end 61 to second end 63.

The applicator 57 has two elongate band supporting members, 65, 67 which are pivotally attached to the housing 59 proximate to the first end 61 of the housing 59. The band supporting members pivot from a first end 65a, 67a of the band supporting members 65, 67.

As seen best in Figure 14C, the housing 59 has cutaway sections 69, on two opposed circumferential sides of the housing 59. The width of these cutaway sections 69 corresponds to a dimension of the band supporting members 65, 67. This allows the band supporting members 65, 67 to move from a first position (shown in Figure 13A) in which the band supporting members 65 extend in an axial direction to a second position (shown in Figure 13B) in which the band supporting members 65, 67 are inclined at an oblique angle to the axis 59a such that a distal end 65b, 67b of the band supporting members 65, 67 is radially outboard of the first end 65a, 67a (i.e. are splayed apart). When in the second position, the band supporting members 65, 67 extend through the cutaway sections 69. A sleeve 71 is located within the through bore at the second end 63 of the housing 59. The sleeve 71 is fixed within the bore using a suitable adhesive so that it does not move relative to the housing 59 once in position. At this second end 63 of the housing 59, distal from the band supporting members 65, 67, there is located an actuating member 73 which is rotatably coupled to the housing 59. The actuating member 73 has a handle portion 75, in the form of a knob, and a second reduced diameter portion 77 which is received within the sleeve 71 . The handle portion is economically designed so that it can be rotated easily by the surgeon or medical practitioner. The actuating member 73 also has an annular flange 79 located distal from the handle portion 75 which retains the actuating member 73 in the sleeve 71 .

An elongate rod 81 extends generally axially along the length of the housing 59 from the band supporting members 65, 67 to the actuating member 73. The reduced diameter portion 77 of the actuating member 73 has a threaded bore 83 into which a complimentarily-threaded end 85 of the elongate rod 81 is engageably received. When a user wishes to move the band supporting members 65, 67 from the first position to the second position, the user rotates the actuating member 73 using the handle portion 75. The sleeve 71 acts as a bearing surface for the reduced diameter portion 77, allowing the actuating member 73 to rotate relative to the housing 59 (and the rod 81 ) while remaining axially stationary relative to the housing 59. Since the actuating member 73 is axially constrained relative to the housing 59, rotation of the actuating member 73 results in movement of the rod 81 axially along the housing 59 though the bore. A distal portion 83 of the rod 81 is enlarged relative to the length of the rod 81 and acts as an abutment surface. As the rod 81 moves axially along the housing 59 through the bore, portion 83 abuts an upper angled portions of the band supporting members 65, 67 thereby causing them to pivot radially outward to the second position as shown in Figure 13B and 14B. This movement of the band supporting members 65, 67 to the second position results in the aperture of the band 85 positioned on the band supporting members 65, 67 being circumferentially enlarged (see Figure 14B), therefore allowing the band 85 to be placed around the bowel portion. To return the band supporting members 65, 67 to the first position in which the band supporting members 65, 67 are generally axially aligned with the housing 59, the actuating member 73 is rotated in the opposite direction using handle 75. The applicator 57 further comprises two pushers 87, 89 located on corresponding band supporting members 65, 67. The pushers 87, 89 are generally elongate and are positioned within grooves 91 (only one of which is visible in Figure 14) on the corresponding band supporting member 65, 67. The pushers 87, 89 each have an enlarged portions 93 (best seen in Figure 14C) located towards the distal ends 65b, 67b of the band supporting members 65, 67. In this embodiment, the pushers 87, 89 are retained in a retracted position (as shown in Figure 14C) by the band 85 being positioned on the band supporting members 65, 67. However, in alternative embodiments, the pushers 87, 89 may be biased towards the retracted position. Two struts 95, 97 are located within the bore of the housing 59. These elongate struts 95, 97 are located radially outwards of the rod 81 and run generally alongside it. Towards the upper end 63 of the housing 59 the two struts 95, 97 are joined by a spacer 99 which circumferentially surrounds the rod 81 . Two pins 101 , 103 extend radially outward of the spacer 99 through a cutaway sections 105 (best seen in Figure 14B) on two opposed sides of the housing 59. The cutaway sections 105 extend axially down the housing 59 to permit axial movement of the pins 101 , 103, spacer 99 and elongate struts 95, 97.

When a user applies axially downward pressure to the pins 101 , 103 the struts 95, 97 move axially downward within the housing 59 from a retracted position (shown in Figure 13A and 14C) to an engaged position (shown in Figure 13B and 14D). During movement, the pins 101 , 103 move downwards through cutaway sections 105. In the engaged position, an enlarged portion 95a, 97a of each strut 95, 97 abuts pushers 87, 89 and thereby moves the pushers 87, 89 from a retracted position (shown in Figure 13A and 14C) to an engaged position (shown in Figure 13B and 14D). In moving to this engaged position, the enlarged portions 93 of the pushers 87, 89 move the band 85 along and off the band supporting members 65, 67 and onto the bowel segment. The skilled person will recognise that in this particular embodiment, the struts 95, 97 can only abut the pushers 87, 79 when the band supporting members 65, 67 are in the first position i.e. when the band supporting members 65, 67 are generally axially aligned. However, as will be appreciated, in alternative embodiments, the struts 95, 97 could be configured to abut the pushers when the pushers are in both the first and second positions, or when the pushers are only in the second position.

A helical spring 107 is located between spacer 99 and band support members 65, 67. When a user applies axially downward pressure to the pins 101 , 103 the struts 95, 97 move axially downward within the housing 59 from a retracted position (shown in Figure 13A and 14C) to an engaged position (shown in Figure 13B and 14D) thereby compressing the helical spring 107. When the user releases pressure on the pins 101 , 103 the spring 107 returns the struts 95, 97 and pins 101 , 103 to the resting position. The struts 95, 97, in this embodiment, are therefore biased towards the retracted position. The skilled person will appreciate that in other embodiments, the pushers 87, 89 could also be biased towards the retracted position.

Referring now to Figure 15 there is depicted an applicator being used to apply a bowel constriction band to a bowel segment. As shown in Figure 15A, a head portion of a circular stapling device (not shown) is placed through a linearly stapled bowel segment 109 such that spike 1 1 1 protrudes through the staple line 1 13. A bowel constriction band 1 15 is placed onto the band support arms 1 17, 1 19 of an applicator 121 . The band support arms 1 17, 1 19 of the applicator 121 are then moved from a first position (shown in Figure 15A) to a second position (as shown in Figure 15B) where an aperture defined by the band 1 15 is expanded. As shown in Figure 15C, the band 1 15 is then placed circumferentially around the bowel segment 109 using the spike 1 1 1 as a guide. The band support arms 1 17, 1 19 are then moved back to the first position, the aperture in the band 1 15 closing around the bowel segment 109 and gathering it around the spike 1 1 1 (Figure 15D). Pushers 123, 125 are then moved from a retracted position (as shown in Figure 15D) to an engaged position (as shown in Figure 15E) where the pushers 123, 125 abut the band 1 15 thereby moving the band 1 15 along and off the band supporting members 1 17, 1 19 and onto the bowel segment 109. As can be seen in Figure 15F, using this method, the stapled bowel tissue is evenly gathered around the spike 1 1 1 . A second "umbrella" portion of a circular stapling device in then placed in a resected upper bowel segment 127 and sewn in place. The two portions of the circular stapler are then joined together as shown in Figure 15G. The upper and lower portions of bowel 109, 127 are drawn together as shown in Figures 15H and I. The circular stapler is then activated, stapling upper and lower bowel portions 109, 127 together. The bowel tissue within the circular staple line is cut using a blade, which may be integrated within the circular stapler and the tissue and bowel constriction band 1 15 removed to open the lumen of the bowel.

Although it is possible to apply a bowel constriction band to a bowel segment without the use of a specifically designed applicator, the applicator of the present invention allows the surgeon or medical practitioner to efficiently place the band in position on a bowel segment. As will be appreciated, the applicator of the invention allows the surgeon or medical practitioner to place the bowel constriction band around the bowel at a distance, since the band support arms can be moved between first and second positions using a handle which may be located at a distance from the band support arms.

It will be appreciated that numerous modifications to the above described methods, applicators and bowel constriction bands may be made without departing from the scope of the invention as defined in the appended claims. Moreover, any one or more of the above described preferred embodiments could be combined with one or more of the other preferred embodiments to suit a particular application.

Optional and/or preferred features may be used in other combinations beyond those described herein, and optional and/or preferred features described in relation to one aspect of the invention may also be present in another aspect of the invention, where appropriate.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have bene shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that while the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," or "at least one," are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim.

Claims

CLAIMS:

1 . A lumen constriction band configured for constricting a lumen wherein the band is generally annular and in use is moveable from a first position in which the band is generally unexpanded to a second position in which the band is expanded to increase a dimension of an aperture defined by the band so as to enable application to a lumen, and wherein the geometry and/or material properties of the band are configured to allow the band to expand sufficiently to allow application to the lumen.

2. The lumen constriction band according to claim 1 wherein the band defines a generally circular aperture having radius Ri and has a generally circular cross section of radius r; and wherein the band has an aspect ratio of at least around 0.5, wherein the aspect ratio is defined as

3. The lumen constriction band according to claim 2 wherein the band has an aspect ratio of between around 0.5 and around 1 .3.

The lumen constriction band according to claim 2 or 3 wherein the band has an aspect ratio of around 1 .2.

The lumen constriction band according to any preceding claim wherein the band is rectangular or square in cross section.

The lumen constriction band according to any preceding claim wherein an edge of the band is bevelled thereby promoting rolling of the band.

The lumen constriction band of any preceding claim wherein the band is formed from at least two materials, the at least two materials exhibiting differing elastic properties.

The lumen constriction band of claim 7 wherein the band comprises annuli of the at least two different materials running generally in parallel.

9. The lumen constriction band according to claim 7 or 8 wherein the at least two different materials exhibit differing Young's moduli.

10. The lumen constriction band according to any one of claims 7-9 wherein a first outer annuli of material has an increased elasticity compared to a second inner annuli of material thereby permitting stretching of the band to increase the circumference of the aperture therein.

1 1 . The lumen constriction band according to claim 1 wherein the band is formed from a liquid crystalline elastomer.

12. A method comprising:

constricting a lumen of a bowel;

resecting a portion of the bowel adjacent the constriction to form a first bowel segment having a closed end thereof, and a second bowel segment having an open end;

guiding a projecting member through the lumen of said constricted portion of the first bowel segment such that said projecting member projects out of the closed end of the first bowel segment;

applying a bowel constriction band around said first bowel segment to gather a portion thereof that is adjacent said closed end around said projecting member; fastening said first and second bowel segments to one another; and

removing said resected bowel tissue and said bowel constriction band from said bowel.

13. The method according to claim 12 wherein the method further comprises attaching a second projecting member to said second bowel segment such that said second projecting member projects out of said open end of said second bowel segment, wherein said attaching includes gathering a portion of the second bowel segment adjacent said open end around said projecting member.

14. The method according to claim 12 or 13 wherein said first and/or second projecting members further comprise generally circular guiding plates.

15. The method according to claim 13 or 14 when dependent on claim 13 further comprising locating said first and second bowel segments adjacent one another prior to the step of fastening said first and second bowel segments to one another, wherein said locating of said first and second bowel segments adjacent one another is achieved by engagement of said first and second projecting members.

16. The method according to any one of claims 12-15 wherein said step of constricting the lumen of the bowel comprises stapling or suturing the bowel, optionally linearly stapling the bowel.

17. The method according to any one of claims 12-16 wherein said step of resecting a portion of bowel adjacent the constriction comprises resecting a portion of bowel above said sealed bowel segment.

18. The method according to any one of claims 12-17 wherein said sealed bowel segment is a lower rectal bowel segment.

19. The method according to any one of claims 12-18 wherein said fastening said first and second bowel segments together comprises stapling said first and second bowel segments together.

20. The method according to any one of claims 13-19 when dependent on claim 13 wherein said first and second projecting members comprise portions of a circular stapler.

21 . The method according to any one of claims 13-20 when dependent on claim 13 wherein said method further comprises withdrawing said first and second projecting members from the bowel.

22. The method according to any one of claims 12-21 wherein said bowel constriction band is in accordance with any one of claims 1 -1 1 .

23. An applicator for applying a lumen constriction band to a lumen, the band defining an aperture therein for receiving a tissue segment, wherein the applicator comprises:

a plurality of band supporting members, in use the band supporting members being received within the aperture defined by the band, said supporting members being moveable between a first position in which the band supporting members are close together and a second position in which the band supporting members are further apart such that the aperture defined by the band is expanded to increase a dimension of the aperture; and

a pusher operable to displace the lumen constriction band from said band supporting members.

24. An applicator according to claim 23 wherein said supporting members are arranged to pivot between said first and second positions.

25. An applicator according to claim 23 or 24 wherein said applicator comprises a plurality of said pushers, each pushers being supported on a corresponding band supporting member.

26. An applicator according to any one of claims 23-25 wherein the pusher or pushers are moveable between a resting position and an actuating position wherein movement from said resting position to said actuating position results in the pusher displacing the lumen constriction band from said band supporting members.

27. An applicator according to claim 26 wherein the pusher or pushers are biased towards resting position.

28. An applicator according to claim 27 wherein the pusher or pushers are biased towards the resting position by a resilient element.

29. An applicator according to any one of claims 26-28 wherein each pusher is moveable between its resting and actuating positions independently of the other pushers.

30. An applicator according to any one of claims 23-29 wherein said band supporting members are elongate.

31 . An applicator according to any one of claims 23-30 wherein each band supporting member has a shoulder against which said band is locatable.

32. An applicator according to claim 31 when dependent on claim 30 wherein said shoulder is positioned at a distal end of said elongate supporting member.

33. An applicator according to any one of claims 23-32 wherein the applicator comprises only two band supporting members.

34. An applicator according to any one of claims 23-33 and further comprising an actuating member arranged to effect movement of said supporting members from said first position to said second position.

35. An applicator according to claim 34 wherein rotation of the actuating member causes support arms to move from said first position to said second position.

36. An applicator according to claim 34 or 35 wherein said actuating member is spaced from said supporting members, and wherein a drive mechanism is provided between said actuating member and said supporting members.

37. An applicator according to claim 36 wherein said drive mechanism comprises an elongate rod.

38. An applicator according to claim 37 wherein said elongate rod threadedly engages the actuating member and thereby co-operatively forms a lead screw mechanism therewith.

39. An applicator according to any one of claims 23-38 wherein the applicator comprises an elongate cylindrical main body.

40. An applicator according to claim 39 wherein the main body has a width of around 15 mm or less.

41 . An applicator according to any one of claims 23-40 wherein at least a portion of the applicator is fabricated from stainless steel.

42. A kit of parts comprising an applicator according to any one of claims 23-41 and a lumen constriction band according to any one of claims 1 -1 1 .

43. A kit of parts for the applicator according to any one of claims 23-41 .

44. The method according to any one of claims 12-22 wherein said applying a bowel constriction band circumferentially around said sealed bowel segment utilises the applicator according to any one of claims 23-41 .