Patent Description:
A perianal fistula is an artificial tunnel that, in the majority of cases, develops from an infection that begins within a blocked anal gland. If the infection cannot be cleared from the anal gland an abscess forms and the infection burrows though the sphincteric muscles and exits at the buttocks integument. Patients experience pain associated with the tract and associated abscesses and suffer faecal and blood discharge from the fistula tract. Perianal fistulas may also result from gastrointestinal diseases such as Crohn's disease, ulcerative colitis, colorectal cancers and their associated treatment and complications due to rectal fissures and trauma.

The global incidence of perianal fistula is <NUM> per <NUM>,<NUM> population. Over <NUM>,<NUM> fistula procedures are performed between the United States and Western Europe each year. Thirty percent of the procedures performed are reoperations due to treatment failure contributing to a significant preventable cost to the healthcare systems.

Given the inadequate treatment options and poor surgical outcomes there is a defined clinical need for a more effective perianal treatment device.

There is currently no single "gold standard" technique that a surgeon can perform to effectively cure a perianal fistula and not render the patient incontinent. A common fistula treatment is a fistulotomy procedure. A fistulotomy involves the dissection of the sphincteric muscles and the laying open of the fistula tract. Fistulotomies have a relatively high cure rate, however, this procedure results in a high risk of faecal incontinence.

From a patient's point of view, many are happy to assume the risk of incontinence in order to resolve the painful fistula tract. However, this is obviously not an ideal treatment pathway and for many patient population groups the secondary outcome is far from acceptable.

Another commonly used fistula treatment methodology is the use of a seton. Setons are used as a sphincter sparing technique and is simply a suture or vascular strap that is passed through the tract of the fistula and the rectum and tied in a loop. The seton maintains tract patency allowing the infection in the fistula tract to drain, help the tract constrict in length and may cure the tract. If the tract is not cured by the seton the physician can perform a fistulotomy. This approach of trying to preserve the sphincter with setons has been used for over <NUM> years and is still the preferred method used by surgeons today.

In an effort to provide a non-destructive perianal fistula treatment various glues and plugs have been developed and introduced to colorectal surgeons in the past <NUM> years. However, these techniques are not very successful and their use is not widespread. Such glues which are injected into the fistula tract generally become brittle and are not able to occlude the tract for a long enough period to fully heal, faeces re-enter the tract resulting in abscess formation and refistulisation. Physicians often attempt to treat perianal fistulas with glues and plugs even though there may only be a <NUM> percent chance of effectiveness because it is a sphincter sparing technique and they can always resort to a seton and eventual fistulotomy if all fails.

Attempts have also been made to use plugs to occlude perianal fistula tracts. For example, <CIT> describes a plug-like fistula closure device with an attached flexible application string which also serves to evacuate liquids out of a fistula. However, generally the plugs fail because they become extruded from the tract, allowing faeces to enter the tract resulting in reinfection, abscess formation and refistulisation.

There is therefore a need for an improved method and device for the treatment of perianal fistulas. <CIT> describes a surgical fastener for fastening material such as a mesh used in hernia repair to tissue.

<CIT>, Fig. <NUM> and paragraphs <NUM>-<NUM>, teaches a conical, helical closure element to repair a fistula.

According to the invention there is provided a perianal fistula treatment system as set out in claim <NUM>. Various features of the treatment system are set out in appended claims <NUM> to <NUM>.

The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:.

The device is capable of one or more of the following:.

The perianal fistula treatment device ensures sparing of the sphincter, occluding of the fistula tract internal opening, and promotion of drainage and tissue healing.

The device consists of a head with anchoring and sealing mechanisms which is secured in the tissue tract and prevents re-infection of the wound. A tail section provides seton-like drainage and prevents re-abscessing due to premature closure of the skin site.

The anchoring and sealing mechanism of the device consists of a tapered coil. The coil geometry is designed to pull tissue together as is it deployed into the sphincter muscle complex, resulting in a strong anchor but also, importantly, an effective compressive seal preventing reinfection of the fistula tract and close tissue approximation to enhance tissue healing.

The perianal fistula treatment device preserves sphincteric and anatomical conditions and functions, prevents re-fistulisation, and improves healing time over the current treatment methods. The device consists of a tapered coil and a drainage seton. There may be a centering alignment feature. A delivery mechanism is also described. The coil may be led into the fistula tract by the drainage seton and centered into the tract by means of the centering feature. The larger diameter of the tapered coil is abutted against the tissue surface, surrounding the internal opening of the fistula tract with adequate margin. The delivery mechanism rotates the coil until it is just submucosal positioned. The coil closes the fistula internal opening by compressing the tract's surrounding tissue inwardly such that the tissue is brought within close approximation creating a seal impermeable to foreign materials and promoting tissue growth across the closely approximated fistula tract. The drainage seton provides a conduit to drain any abscess and remaining or newly formed exudate and fluids from the fistula tract throughout the time of the healing process. The centering feature insures the coil device is placed easily into the fistula tract and the outer coil is placed within the adequate margins surrounding the fistula tract and acts as a securing mechanism for the drainage seton.

The following numerals are used in the drawings:.

<FIG> illustrates an anal fistula tract <NUM>, which is an abnormal connection between the rectum <NUM> and the integument of the buttocks <NUM>. The internal opening <NUM> of the fistula is located at the mucosal surface <NUM> of the rectum <NUM>. The fistula tract <NUM> may generally originate at the dentate line <NUM> and pass through the sphincteric muscle complex which consists of the internal sphincter muscle <NUM> and external sphincter muscle <NUM>. The external opening <NUM> of the fistula tract <NUM> is located at the integument surface of the buttocks <NUM>.

<FIG> shows the device consisting of a tapered coil <NUM>, drainage seton <NUM>, and delivery mechanism <NUM> being drawn through the fistula tract by means of tension applied to second end of drainage seton <NUM>.

The tapered coil <NUM> is brought into apposition to the mucosal tissue wall of the rectum <NUM> as shown in <FIG>. The coil is centered on the internal opening of the fistula tract <NUM> at the dentate line <NUM> via tension applied to the second end <NUM> of the drainage seton <NUM> and the support of the bioabsorbable mechanism <NUM> interface <NUM>.

The driver mechanism <NUM> delivers the coil <NUM> through the mucosal lining <NUM> of the rectum <NUM> via rotatory or other means (<FIG>). The distal tip <NUM> of the coil <NUM> punctures through the musocal lining surface <NUM> and engages initially with the internal sphincter muscle <NUM> surrounding the internal opening <NUM> of the fistula tract <NUM>.

<FIG> illustrates the system component parts. The delivery mechanism interface feature <NUM> of the coil <NUM> is attached to the delivery mechanism member <NUM> of the delivery mechanism <NUM>. The drainage seton <NUM> is attached to a coil centering feature <NUM> via the seton attachment feature <NUM>.

<FIG> illustrates the coil <NUM> completely delivered through and past the mucosal surface <NUM> and into the sphincter complex consisting of the internal <NUM> and external <NUM> sphincter muscles. The delivery mechanism interface <NUM> located distally on the delivery mechanism member <NUM> detaches from the tapered coil <NUM> and the delivery mechanism <NUM> is removed from the surgical field.

The mechanism of action of the delivery of the tapered coil results in sphincter muscle complex tissue being drawn into the centre of the coil <NUM> construct. The mechanism of action is illustrated in <FIG>.

<FIG> illustrates a plan view of an internal opening <NUM> of a fistula tract <NUM> located at the surface of the musical lining of the rectum <NUM> at the dentate line <NUM>. <FIG> shows the closure coil <NUM> being brought into apposition to the musical surface <NUM> and being centred on the fistula tract <NUM> internal opening <NUM>. As the closure coil <NUM> is delivered through the mucosal surface <NUM> and into the internal sphincter muscle <NUM> the sphincter muscle tissue begins to be gathered into the centre of the closure coil <NUM>. <FIG> illustrates further delivery of the closure coil <NUM> resulting in an increased mass of sphincter muscle tissue being gathered internally in the coil. <FIG> illustrated complete delivery of the closure coil <NUM> entirely past the mucosal surface <NUM> and completely into the sphincter muscle complex including the internal <NUM> and external <NUM> sphincter muscles. The complete delivery of the coil <NUM> results in closure of the internal opening <NUM> of the fistula tract <NUM> by mechanism of gathering and compression of sphincter muscle tissue. This mechanism as described allows both the sphincter muscle tissue to knit together, and the mucosal surface to remodel to cover the site of delivery over a period of time, eventually resulting in complete resolution of the sphincter muscle defect associated with the internal opening of the fistula tract.

Referring to <FIG> there is illustrated a tapered coil <NUM> which has a leading end <NUM> and a trailing end <NUM>. The coil is in this case conical and decreases in lateral extent between the leading and trailing ends.

The implant is a coiled body structure. The leading end of the implant is the largest coil and initially surrounds the tissue defect with appropriate margin. As the implant is advanced the leading end provides a large surface area to effectively anchor the implant. Each subsequent coil provides (adds to) the anchoring and compression function. The smallest coil towards the trailing end provides the highest amount of tissue compression. As the implant is turned into the tissue each coil further compresses the captured tissue toward the center of the tissue defect, thus effectively completely compressing the surrounding tissue inwardly. The close approximation of tissue allows for the tissue to heal together. This compression provides an effective seal against the pressures generated in the rectum and prevents entering of passing faeces into the fistula tract thus preventing re-infection. The smaller diameters of the implant coils retain the captured tissue from separating and prevents the breakdown of the healing process or foreign material from entering the tissue defect. This is a major advantage over sutures and suture based surgical techniques such as the advancement flap (dermal flap) and the LIFT procedures.

The compression ensures close approximation of tissue throughout the center of the implant. At the most proximal surface the close approximation of tissue provides support to the healing mucosal lining of the rectum over the implant and tissue defect. Thus the healing tissue is fully supported by the implant during the healing process and is capable of surviving pressures of 150mmHg and upwards of 200mmHg which can be generated in the rectum.

The coil is delivered submucosal (at a predetermined depth) below the surface of the mucosa. This is to ensure that there is a full mucosal seal at the rectal mucosa surface to provide for a bacterial seal barrier. With the implant just below the surface the tissue is drawn inwards for complete compression and supports the mucosa healing process.

As the implant is turned into the tissue the compression becomes greater along the depth of the coil (progressive compression) and the length of the tract captured internal of the implant is compressed completely. This close approximation of tissue aids in the healing process.

Referring to <FIG> it will be noted that in this case the tapered coil <NUM> has a pointed tissue insertion tip <NUM>. The coil <NUM> also has a delivery mechanism interface feature <NUM>.

<FIG> illustrate another tapered coil <NUM> which also has a pointed tissue insertion tip <NUM> and a delivery mechanism interface feature <NUM>. In this case the coil also has a centering feature <NUM>. The centering feature <NUM> passes through the centre of the fistula tract and allows attachment of the drainage seton. The centering feature <NUM> allows centering of the coil in a concentric fashion to the fistula tract internal opening.

It will be appreciated that a coil device with a centering feature such as the centering feature <NUM> illustrated in <FIG>, with or without an attached seton, may be used to close fistula openings that may commonly occur in other areas of the body, such as: biliary (created during gallbladder surgery, connecting bile ducts to the surface of the skin), cervical (either an abnormal opening into the cervix or in the neck), craniosinus (between the space inside the skull and a nasal sinus), enterovaginal (between the bowel and vagina), faecal or anal (the faeces is discharged through an opening other than the anus), gastric (from the stomach to the surface of the skin), metroperitoneal (between the uterus and peritoneal cavity), umbilical (between the navel and gut). These fistulas may be:- blind also known as a sinus (open on one end only, but connects to two structures); complete (has both external and internal openings); horseshoe (connecting the anus to the surface of the skin after going around the rectum); or incomplete (a tube from the skin that is closed on the inside and does not connect to any internal structure).

<FIG> illustrates a coil device with a centre seton feature <NUM>. In this embodiment the coil, centre feature and drainage seton are constructed from a single continuous monolithic structure.

<FIG> illustrates a coil which has a centre feature <NUM> with a seton attachment feature <NUM> at the distal end. A drainage seton <NUM> is attached to the feature <NUM>.

It will be appreciated that the tapered coil may be of any suitable shape in transverse cross section. Some examples are illustrated in <FIG>. For example, the coil may be round, oval, triangular, multifaced or ribbon-like. In some cases the coil may be hollow.

The coil may be intended for subsequent removal or may be bioabsorbable.

A bioabsorbable tapered coil would be beneficial to treatment of perianal fistulas due to the body's natural tendency to reject foreign materials.

The system of the invention also comprises a delivery device for the perianal fistula treatment device.

The delivery device may comprise a hollow element such as illustrated in <FIG> through which the tapered coil is delivered. The hollow delivery element may comprise a coil. <FIG> illustrates a solid coil to be delivered by a hollow delivery element of <FIG> and <FIG> shows the hollow delivery element with the solid coil in place.

The system consists <FIG> of a hollow delivery element <FIG> that contains (houses) the implantable element <FIG>. The implantable element <FIG> is housed in the delivery element <FIG> during the rotational delivery process. Once the delivery element <FIG> has reached the desired delivery position, it is uncoupled from the implantable element <FIG> and then rotated in the opposite direction of the direction of delivery (most commonly counter clockwise), leaving the implantable element <FIG> in place of the tissue bulk.

It will be appreciated that the system may be reversed with a hollow coil delivered over a solid delivery element.

In some cases the delivery device comprises a rail for the tapered coil. The rail and the coil may have interengagable features. Some examples are illustrated in <FIG>.

The rail system <FIG> consists of an outer implantable coil element <FIG>, and an inner support rail element <FIG>. The two elements interlock. The system <FIG> is rotated (most commonly in a clockwise direction) to the desired tissue depth. Upon the system <FIG> reaching the desired tissue depth, the elements are uncoupled <FIG> and the inner support rail is reversed out of the tissue bulk by rotation opposite in direction to insertion (commonly counter clockwise), leaving behind the outer implantable coil element <FIG> in place surrounding, compressing and closing the fistula tract.

It will be appreciated that the system may be reversed with an inner implantable coil delivered over an outer support rail.

The centre feature may have a ball feature along the shaft to aid in anchoring a seton that may be tied or looped around the centre feature. The ball provides a back stop where the knotted or looped seton will not detach from the centre feature.

The centre feature may have a hook feature along the shaft to aid in anchoring a seton that may be tied or looped around the centre feature. The hook provides a back stop where the knotted or looped seton will not detach from the centre feature.

The centre feature may have a cleat feature along the shaft to aid in anchoring a seton that may be tied or looped around the waist of the cleat feature. The cleat provides a back stop where the knotted or looped seton will not detach from the centre feature.

The centre feature may be hollowed as in <FIG> and the seton may be placed in the hollowed portion. It may be glued or heat staked as shown in <FIG> or crimped as shown in <FIG>.

The seton may be attached by a butt joint as shown in <FIG>. The centre feature and seton are inserted into a tubular element with opposite ends facing each other as in <FIG>. The three components may be joined by heating, glue as shown in <FIG>, or by crimping/swaging as shown in <FIG>. The join may have multiple crimp points along the tubular element to securely attach the seton and centre feature.

The seton and centre feature may be thermally bonded / joined together as in <FIG>, where both materials are made of a material with similar glass transition temperatures (Tg) and brought to their Tg and allowed to flow together creating a secure junction.

It will be appreciated that the embodiments of this system may also incorporate features such as previously described, including, but not limited to, a centre feature, a seton attachment feature, an integrated drainage seton and an integrated sharp tip located on the drive rail.

The seton <NUM> is used as a guidance and positioning mechanism and once the device is implanted serves as a means of fistula tract drainage. The seton <NUM> may be constructed of bioabsorbable materials, tissue healing enchantment properties, infection control agents and be constructed of part or composite of these materials.

After the fistula tract preparation, the seton <NUM> is attached using standard surgical technique to the existing surgical probe, suture, or seton already in place in the fistula tract. Once the seton <NUM> is attached, the system is pulled through the fistula tract proximally (towards the physician) until the coil device is adjacent to the tissue wall (rectal wall). The seton <NUM> ensures that the outer leading coil is centred around the outside of the fistula tract. Tension may be applied to the seton <NUM> as the coil is advanced into the tissue to aid in advancement and to maintain a centred position around the fistula tract.

The seton <NUM> is attached to the central portion of the coil <NUM>. With the coil knitting together the sphincteric muscle and closing the fistula tract's internal opening the seton <NUM> maintains the proximal portion of the fistula tract's patency to facilitate drainage of any abscess, pus, and new accumulation of bodily fluids to prevent infection occurrence. The seton <NUM> prevents the tract from closing in on itself proximal of any fluid accumulation and acts as a conduit allowing material drainage between the wall of the tract and the outer wall of the seton <NUM>. The seton <NUM> may also have a central lumen with tangential drainage holes entering from the external wall of the seton <NUM>. The seton <NUM> may be constructed with a multi surface external wall to create channels and optimize the fluid drainage and prevent the fistula tract wall from occluding drainage around the seton. The seton <NUM> may be constructed of part or all elements as described and illustrated in <FIG>.

The seton <NUM> is constructed of materials that are strong enough to allow for surgical placement in the fistula tract. The seton <NUM> may be constructed of materials that are non-absorbable and meant to be removed at a later time. Alternatively, the seton <NUM> may be made of materials that bioabsorb throughout and upon completion of the fistula tract healing processes (examples include magnesium, PLA, PLGA). The seton <NUM> may be constructed of or include anti-infection agents to prevent infection of the fistula tract (silver ions, antibacterial agents). The seton <NUM> may be constructed of materials that aid in tissue growth (stem cell, collagen matrix). The seton <NUM> may be constructed of part or all elements as described.

The seton may be of any suitable shape in cross section such as round, oval, cross shape, star or braid as illustrated in <FIG> and <FIG>, <FIG>. In all cases the seton may be hollow as illustrated in <FIG>, <FIG>, <FIG> to further enhance drainage. The seton may have peripheral holes as illustrated in <FIG> and <FIG> to provide for increased drainage effectivity. The holes allow additional surfaces of drainage, by increasing drainage surface area/channels the fluid drains more quickly and reduces the chance that any of the channels will become occluded and prevent fluid drainage at the same moment in time.

<FIG> illustrates the delivery of the system through the fistula tract prior to deployment of the coil. The seton, attached to the centre feature allows the coil to be drawn into apposition against the mucosal wall, and located concentric to the fistula tract internal opening.

<FIG> illustrates the position of the coil prior to deployment and demonstrates the effect of the centering feature in combination with the seton in positioning the coil concentrically around the fistula tract internal opening. (Dimensions 'x' being equal).

As noted above, one or other or both of the coil and seton may comprise bioabsorbable materials.

Synthetic bioabsorbable materials may include PLA and PLGA (poly (lactic-co-glycolic acid)) (PLGA, PCL, Polyorthoesters, Poly(dioxanone), Poly(anhydrides), Poly(trimethylene carbonate), Polyphosphazenes), and or natural bioabsorbable materials may include fibrin, collagen, chitosan, gelatin, Hyaluronan are bioabsorbable polymers and would be a material of choice as they are commonly used bioabsorbable materials and have been well studied and used in medical products for over <NUM> years.

For example, companies such as Ethicon market a number of such products with different absorption rates such as http://www. com/healthcare-professionals/products/. Absorbable polymer materials are also available from medical material companies such as Zeus, see http://www. com/advanced-products/absorv-bioabsorbables.

Typical materials for the seton include:.

In one case both the coil and the seton are bioabsorbable, and the seton degrades prior to the degradation of the coil. This may be achieved in a number of different ways, such as the seton being of a different bioabsorbable material to the coil.

For example the coil implant may be constructed of PLLA which degrades slowly, typically within <NUM> to <NUM> months depending on formulation, cross section, and surface modifications, and the Seton drain may be constructed of PLGA (<NUM>/<NUM>) which typically degrades "faster" in <NUM> to <NUM> months depending on formulation, cross section, and surface modifications.

Another method of altering the time of degradation (degradation (absorption) properties) is by providing a reduced cross sectional area, more porosity, less crystallinity, more reactive hydrolytic groups in the backbone, more hydrophilic end groups, and/or more hydrophilic backbone.

In one case, the seton begins to absorb <NUM> weeks post-surgical implantation. This is variable depending upon the healing time of the patient, with full healing usually occurring within a <NUM> to <NUM> week period. By way of example the coil implant may remain for a period of at least <NUM> weeks after healing and may degrade over a <NUM> to <NUM> month time period from the date of implantation.

Advantageously, the closure mechanism of the device is maintained during the entire healing process. In some cases the coil remains in situ to withstand rectal pressures and maintain closure of internal tract opening for at least <NUM> weeks to prevent re-opening of the tract.

The coil implant may remain in place longer to allow full healing of the internal opening of the fistula tract. The seton drain may degrade at a faster rate compared to the coil implant so long as the seton drain is in place for a long enough time for all remaining abscess and infection, to drain from the fistula tract and any side branches. It is advantageous that the seton drain absorbs faster than the coil so that the patient does not have any visually remnant feature of the device or thoughts of fistula. The seton is not needed for as long a period as the coil implant, with the seton drain absorbing faster than the implant, the patient will not have to return to the surgeon for removal during the internal opening healing process.

Also, the implant remains in place for a long enough period of time (e.g. greater than <NUM> week) to allow remodelling of the defect in the mucosa and formation of a mucosal layer. This mucosal layer acts as a bacterial seal preventing reinfection of the tract from entering of fasces. The reformation of the musical layer in conjunction with the sphincter muscle closure mechanism prevents fasces entering the tract.

The implant coil and draining seton may be doped or loaded with healing and antimicrobial agents (such as stem cell, silver ions, silver particles, antibiotics, antibacterial agents and the like).

The seton may be of differential bioabsorption wherein the seton is absorbed at a different rate along its length.

The seton may be of differential bioabsorption wherein the distal portion of the drain absorbs more quickly than the proximal portion. This differential absorption of the seton results in the seton remaining attached to the coil via the proximate portion until fully absorbed. Advantageously, this allows for the external opening to close and remove the chance of the seton being pulled out through the external opening.

The seton may also be of differential bioabsorption wherein the proximal portion of the seton absorbs more quickly - in this case the anchoring mechanism of the closure device with relation to the seton could be broken at an earlier time than the full seton absorption allowing the seton to be removed (by the patient or doctor or naturally fall out) through the external opening.

In both differential absorption embodiments, the entire seton would have to remain in place for full healing (and drainage) time of the tract (e.g. <NUM> weeks).

The bioabsorbable materials used in the construction of the implant coil, or drainage seton, or both, can be both natural or synthetic polymers such as those listed below.

The selection of the material used can be made whilst taking the following factors into account.

The implant coil of the invention may be delivered by a number of techniques. In accordance with the present invention the coil is delivered by a coil delivery mechanism. In this case, the implant coil may have an interface region for interfacing with the delivery mechanism.

A perianal fistula treatment according to the present invention comprises an implant coil having a tapered portion which is configured for insertion into bulk tissue surrounding a fistula. The implant coil has a driver interface portion which is configured for engagement with a driver implement for rotation of the coil to draw tissue surrounding a fistula inwardly. The advantages of such an implant coil are:.

One such implant coil <NUM> is illustrated in <FIG> and comprises a tapered section <NUM> and a driver interface portion which in this case is provided by straight coil section <NUM> which has a substantially uniform lateral extent along a length thereof. The implant coil <NUM> has a leading end <NUM>, a transition region <NUM> and a trailing end <NUM>. The tapered portion <NUM> of the coil extends from the leading end <NUM> to the transition region <NUM> and the driver interface portion <NUM> extends from the transition region <NUM> to the trailing end <NUM>. It will be noted that, as described in other embodiments, the tapered portion of the coil decreases in lateral extent between the leading end <NUM> and the transition region <NUM>. The leading end <NUM> may have a pointed tissue insertion tip as illustrated, for example, in <FIG>.

The compression ensures close approximation of tissue throughout the center of the implant. At the most proximal surface the close approximation of tissue provides support to the healing mucosal lining of the rectum over the implant and tissue defect. Thus the healing tissue is fully supported by the implant during the healing process and is capable of surviving pressures of 150mmHg (<NUM> kPa) and upwards of 200mmHg (<NUM> kPa) which can be generated in the rectum.

The coil is delivered submucosal (at a predetermined depth) below the surface of the mucosa. This ensures that there is a full mucosal seal at the rectal mucosa surface to provide for a bacterial seal barrier. With the implant just below the surface the tissue is drawn inwards for complete compression and supports the mucosa healing process.

In this and other embodiments the implant body is in the form of an open tapered coil body (for example, without a cross bar or other centering feature) in which the leading edge, (into the muscle) is of a larger diameter than the trailing edge, (rectum surface). The trailing portion is of smaller diameter than the leading portion. The coil is of open form, therefore there is no inward protrusion at either the proximal nor distal end of the body. This open form factor enables the implant to be driven into the tissue body to a pre-determined depth (depending on the taper) which results in progressive tissue compression.

At least the driver interface portion of the implant coil is solid and in some cases all of the implant coil is solid. Alternatively, as described above and below, the implant coil or at least part thereof may be hollow.

In this embodiment, preferably the treatment device also includes a seton of the type described above. In some cases the seton is not mounted or attached to the implant coil during delivery but may be attached so as to extend from the coil when the coil is in situ. In some cases the seton may be embedded in the sphincter muscle complex and lead so that the end of the seton protrudes through the external opening of the fistula tract.

The implant is delivered using any suitable delivery device as described. In one case the delivery device comprises a driver implement which interfaces with the implant coil and is used to rotate the coil to draw tissue surrounding a fistula inwardly. The driver implement preferably interfaces with the driver interface of the implant coil.

In some cases the driver implement comprises a driver coil which is configured for engagement with the driver interface of the implant coil. The driver coil may have a substantially uniform lateral extent along a length thereof for engagement with the corresponding driver interface portion of the implant coil.

In one embodiment as illustrated in <FIG> a driver coil <NUM> is hollow for interfacing with the interface portion <NUM> of the implant coil.

<FIG> illustrate an assembly <NUM> in which a solid implant coil <NUM> is delivered by a straight hollow delivery coil <NUM>. The coil implant <NUM> has a straight profile section <NUM> and a tapered section <NUM>. The straight profile section <NUM> fits within the internal channel of the delivery coil <NUM> up to the interface <NUM>, whereby the hollow coil <NUM> is rotated which in turn rotates the implant coil <NUM> for delivery.

The hollow sections of the delivery coil in all cases may comprise a single turn, multiple turns or part thereof or the entire construct.

<FIG> illustrate an assembly <NUM> in which a hollow implant coil <NUM> is delivered by a straight solid delivery coil <NUM>. The coil implant <NUM> has a straight profile section <NUM> and a tapered section <NUM>. The straight solid delivery coil <NUM> fits within the internal channel of the hollow coil implant <NUM> up to the interface <NUM>, whereby the solid delivery coil <NUM> is rotated which in turn rotates the hollow coil implant <NUM> for delivery.

The straight sections of the coil in all cases may comprise a single turn, multiple turns or part thereof.

The hollow sections of the implant coil in all cases may comprise a single turn, multiple turns or part thereof or the entire construct.

The delivery system has the following advantages:.

These delivery mechanisms may be coupled to a manually operated, trigger operated user interface or similar.

In current techniques for treating a fistula a surgeon identifies the external opening of the fistula tract and carefully inserts a probe through the external opening, through the fistula tract and through the internal opening of the fistula. The probe is then extended back through the rectum and a localisation seton or suture is attached to the end of the probe which is then drawn back through the rectum and the fistula tract until it exits through the external opening of the fistula tract. The localisation seton loop is then tied off.

The implant and delivery system of the invention is compatible with this known current technique. In the invention the probe or the localisation seton may be used to guide the leading end of the implant coil and/or the drainage seton.

The implant body in some cases is in the form of an "open" tapered coil body in which the distal edge (leading edge, into the muscle) is of a larger diameter than the proximal edge (trailing edge, rectum surface), the proximal portion is of smaller diameter than the distal portion. The coil is of open form, therefore there is no inward protrusion at either the proximal nor distal end of the body. The open form factor enables the implant to be driven into the tissue body to a pre-determined depth (depending on the taper which results in progressive tissue compression).

The open coil design allows for the mucosal layer to heal over the top of the implant, and the implant supports the healing of the mucosal layer, by preventing the pressure from opening the tract, and compromise freshly healed mucosa layer. With the implant below the mucosa it does not interfere with external rectal surface and interact with faeces that may drag the implant out of its purchase or lend to tract infection along its body. Thus, the implant is suitable for submucosal delivery which facilitates the formation of a continuous mucosal surface over the site of implantation.

The implant in some cases has anti-movement (anti-rewind) features to prevent the rotational movement of the implant in the counter-clockwise motion. Typically, the implant is driven into the tissue body in a clockwise motion consistent with the usual direction of driving fixation medical devices. However, it will be appreciated that the implant may also be driven into the tissue in the counter clock-wise direction. The anti-rewind features facilitate the forward driving motion into the tissue body in a clock-wise motion to be effortless during delivery but provide resistance to prevent the implant from working itself out or unwinding during the course of natural wound healing and normal physiological forces experienced day to day of the patient's life.

The anti-rewind features may include one or more of:.

In addition, the driver coil surface <NUM> may be constructed so as to have a lubricious nature (e.g. by means of a coating or surface treatment or other) in order to minimise the torque requirement associated with the tissue friction during delivery of the implant coil and during retraction of the delivery coil.

The coiled section of the delivery coil may include features to temporarily lock or fasten to the implant prior to and during implant delivery. This provides a positive interface between the implant and the delivery mechanism, to prevent premature implant detachment and related delivery issues.

When the implant has been delivered to the correct location and depth the delivery mechanism detaches / disengages from the implant and is removed from the anatomy.

The driver coil may have an interface to the implant which allows positive (interlocking) when the driver coil is turned in a clockwise direction and negative (i.e. disengagement) interaction when the driver coil is turned in an anti-clockwise direction (or vice versa). Thus when the implant has been delivered to the tissue by means of a clockwise driver coil motion, the driver coil may then turn in an anti-clockwise direction, disengage from the implant, and exit (or `back out') from the tissue.

The implant may be attached to the delivery coil by a mechanism that prevents the implant becoming dislodged from the delivery coil prior to complete delivery. Thus, the implant coil is prevented from prematurely detaching from delivery coil.

The internal support structure of the implant coil may have a positive feature (peak) that locks into a negative (valley) feature on the implant. There maybe be several features of this type to enhance the locking grip.

The inverse of this arrangement may also be implemented in which a positive feature is provided on the implant and a negative feature is a part of the driving mechanism.

Alternatively or additionally, the implant may be attached to the internal opening of the implant driver by friction / interference fit / surface roughness. The driver coil may be hollow and accept a solid implant or the driver may be solid and inserted into the hollow portion of the implant.

The cross section of the driver coil may be a channel or slot rather than closed circular. A coil with such a cross section may be more easily manufacturable. It may also allow the incorporation of internal (to the driver coil) locking features to interface with the implant.

The implant is interfaced to the driving mechanism such as a driver coil. In one case the interface comprises a flare or step that abuts against the driving mechanism. One such flare or step <NUM> is illustrated in <FIG>. Such a flare provides the push point of the implant and transfer of force to drive the implant into the tissue body.

The flare may also act as a barb or anti-rewind feature allowing only one way (e.g. clockwise) motion which in one case is forward motion (clockwise motion driven into the tissue body) and prevents the implant from moving in a backwards motion (unwinding/counter clockwise).

Such a barb feature may be achieved by having the flare surface area greater than the driving coil interface surface area.

The flare may be positioned anywhere along the implant body that is optimal for the implant driving force, driver attachment coupling, and/or anti motion control (anti-rewind can be clockwise or anti clockwise).

It will be appreciated that as an alternative to such locking features on the implant coil similar features may be provided on the engagement surfaces of the delivery coil.

The implant is in some cases in the form of a coiled body structure. The distal end of the implant is the largest coil, and the distal end initially surrounds the tissue defect with appropriate margin. As the implant is advanced the distal portion provides a large surface area to effectively anchor the implant (each subsequent coil provides (adds to) the anchoring and compression function). The smallest proximal coil provides the highest amount of tissue compression. As the implant is turned into the tissue each coil further compresses the captured tissue toward the centre of the tissue defect, thus effectively completely compressing the surrounding tissue inwardly. The close approximation of tissue allows for the tissue to heal together. This compression provides an effective seal against the pressures generated in the rectum and prevents entering of passing faeces into the fistula tract thus preventing re-infection. The smaller diameters of the implant coils retain the captured tissue from separating and prevents the breakdown of the healing process or foreign material from entering the tissue defect. This is the advantage over sutures and suture based surgical techniques such as the advancement flap (dermal flap) and the LIFT procedures.

The compression ensures close approximation of tissue throughout the centre of the implant. At the most proximal surface the close approximation of tissue provides support to the healing mucosal lining of the rectum over the implant and tissue defect. Thus the healing tissue is fully supported by the implant during the healing process and is capable of surviving pressures of <NUM> kPa (150mmHg)and upwards of <NUM> kPa (200mmHg) which are generated in the rectum.

Preferably, the coil is delivered submucosal (at a predetermined depth) below the surface of the mucosa. This ensures there is a full mucosal seal at the rectal mucosa surface to provide for a bacterial seal barrier. With the implant just below the surface the tissue is draw inwards for complete compression and supports the mucosa healing process.

As the implant is turned into the tissue the compression becomes greater along the depth of the coil (progressive compression) and the length of the tract captured internal of the implant is compressed completely, the close approximation of tissue aids in the healing process.

The implant and delivery system is compatible with current surgical technique.

Upon completion of the surgeon preparing the tissue tract, the device drain is attached to the rectal end of the fistula probe or seton/suture that was used to localize the tract.

The probe /seton is pulled toward the surgeon through the fistula tract out of the external opening until the large distal portion of the implant is abutted against the rectal wall. The Implant coil is aligned to be concentric to the internal tract opening.

The device drain is tied to the fistula probe or localization seton.

In one embodiment the drain seton runs distal of the implant and through the length of the handle and may be anchored in the proximal potion of the drive shaft or handle.

At the interface of the implant and driver a cutting mechanism (such as a snip, guillotine or the like) may be provided to automatically cut the drainage seton once the implant is delivered. The handle/delivery system may then be readily removed from the surgical field.

In another embodiment the drain seton is locked to the handle/driver mechanism during implantation (delivery of implant) to maintain traction. Once the implant is fully implanted the handle is decoupled (automatically or manually) from the drain seton. The excess drain seton material may be trimmed at the external surface of the closed tissue tract site at the surface of the rectum.

Referring to <FIG> and <FIG>, a seton <NUM> is held in a fixed position along the length of the tissue tract <NUM> due to the compression at the internal opening <NUM>. The implant opening <NUM> compresses the tissue opening <NUM> around (onto) the drain seton <NUM>, locking it into place. The drain seton may have a specialty designed / located compression zone and may have corresponding features to facilitate the anchoring of the seton in this zone <NUM>.

The drain is fixed in place due to the compression forces of the internal tissue tract being compressed inwardly by the radial forces applied by the implant.

To further enhance fixation of the drain seton and prevent the drain seton from moving out of the tract distally or proximally the drain seton may be constructed with locking features <NUM> along the entire length, partial length, and defined/predetermined compression zone at the site of the implant tissue compression, or any combination of these.

Referring to <FIG>, knots <NUM> may be implemented along the length of the drain seton <NUM> or at a specific location such as that of the implant compression zone.

Referring to <FIG>, spheres, cylinders, triangles and other multifaceted shapes <NUM> may be provided such as by moulded over along the length of the drain seton <NUM> or at a specific location such as that of the implant compression zone.

Referring to <FIG>, enhance the anchoring of the drain seton barbs <NUM>, <NUM> may be incorporated along the length of a drain seton <NUM> or at a specific location such as that of the implant compression zone. The barbs may face in both the external <NUM> and internal opening directions <NUM> to prevent motion in either direction.

To enhance the anchoring of the drain seton quills such as <NUM>,<NUM>,<NUM> (<FIG>) may be incorporated along the length of the drain seton <NUM> or at a specific location such as that of the implant compression zone. The quills may face in both the external <NUM> and internal opening direction <NUM> to prevent motion in either direction.

The drain seton maybe be constructed to act purely as a drain and/or as a scaffold to enhance tissue healing.

To provide enhanced drainage, the seton may have a plurality of peripheral holes and may include (pores). The shape of the seton in cross section may be selected from one or more of round, oval, star and cross. The drain/seton is constructed to be bioabsorable.

An example of potential materials include: PLA and PLGA (poly(lactic-co-glycolic acid)) (PLGA, PCL, Polyorthoesters, Poly(dioxanone), Poly(anhydrides), Poly(trimethylene carbonate), Polyphosphazenes), and or natural bioabsorbable materials may include fibrin, collagen, chitosan, gelatin, Hyaluronan are bioabsorbable polymers and would be a material of choice as they are commonly used bioabsorbable materials.

The shape is designed to enhance the drainage of the residual tract. The shape may also act as a scaffold to improve/enhance the healing of the tract.

The plurality of peripheral holes / pores enhance drainage of the tract to prevent the drain/seton from blockage.

To enhance scaffolding, the plurality of peripheral holes / pores may serve as a structure of a scaffold that enhances tissue integration and improves wound healing of the tract.

A variety of materials may be used as a tissue scaffold that enhance and improve tissue wound healing. Many of these materials are bioabsorable polymers or natural tissue materials. An example of potential materials include: PLA and PLGA (poly(lactic-co-glycolic acid) ) (PLGA, PCL, Polyorthoesters, Poly(dioxanone), Poly(anhydrides), Poly(trimethylene carbonate), Polyphosphazenes), and or natural bioabsorbable materials may include fibrin, collagen, chitosan, gelatin, Hyaluronan are bioabsorbable polymers and would be a material of choice as they are commonly used bioabsorbable materials.

The invention also provides a mechanism to stabilise the tissue during the delivery of the implant to prevent bunching and twisting of the mucosal layer during delivery of the implant. By preventing such tissue interaction, the delivery forces may be reduced and a more reliable and repeatable depth of delivery may be achieved.

One mechanism of stabilising the mucosal tissue is achieved by utilising a hollow `trumpet, cone, shield or pyramid' type element that is attached to the delivery mechanism and surrounds the undelivered implant. One such stabiliser <NUM> is illustrated in <FIG> and <FIG>.

The `trumpet' interfaces onto the surface of the mucosal lining and may stabilise the tissue prior to and during the delivery of the implant using one or more of the following mechanisms:.

Modifications and additions can be made to the embodiments of the invention described herein without departing from the scope of the invention. For example, while the embodiments described herein refer to particular features, the invention includes embodiments having different combinations of features. The invention also includes embodiments that do not include all of the specific features described.

The invention is not limited to the embodiments hereinbefore described, which may be varied in construction and detail within the scope of the claims. to rotate the coil to draw tissue surrounding a fistula inwardly. The driver implement preferably interfaces with the driver interface of the implant coil.

In accordance with the present invention, the driver implement comprises a driver coil which is configured for engagement with the driver interface of the implant coil. The driver coil may have a substantially uniform lateral extent along a length thereof for engagement with the corresponding driver interface portion of the implant coil.

The implant body in some cases is in the form of an "open" tapered coil body in which the distal edge (leading edge, into the muscle) is of a larger diameter than the proximal edge (trailing edge, rectum surface), the proximal portion is of smaller diameter than the distal portion. The coil is of open form, therefore there is no inward protrusion at either the proximal nor distal end of the body. The open form factor enables the implant to be driven into the tissue body to a predetermined depth (depending on the taper which results in progressive tissue compression).

Alternatively or additionally, the implant may be attached to the internal opening of the implant driver by friction / interference fit / surface roughness. The driver col may be hollow and accept a solid implant or the driver may be solid and inserted into the hollow portion of the implant. The cross section of the driver coil may be a channel or slot rather than closed circular. A coil with such a cross section may be more easily manufacturable. It may also allow the incorporation of internal (to the driver coil) locking features to interface with the implant.

The implant is interfaced to the driving mechanism which is a driver coil. In accordance with the present invention, the interface comprises a flare or step that abuts against the driving mechanism. One such flare or step <NUM> is illustrated in <FIG>. Such a flare provides the push point of the implant and transfer of force to drive the implant into the tissue body.

The compression ensures close approximation of tissue throughout the centre of the implant. At the most proximal surface the close approximation of tissue provides support to the healing mucosal lining of the rectum over the implant and tissue defect. Thus the healing tissue is fully supported by the implant during the healing process and is capable of surviving pressures of 150mmHg (<NUM> kPa) and upwards of 200mmHg (<NUM> kPa) which are generated in the rectum.

Claim 1:
A perianal fistula treatment system comprising a driver and an implant coil (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the implant coil having:
a tapered portion (<NUM>) which is configured for insertion into bulk tissue surrounding a fistula and which is configured for progressive tissue compression, the implant coil having a leading end (<NUM>) and a trailing end (<NUM>), the implant coil decreasing in lateral extent between the leading and trailing ends; and
a driver interface portion (<NUM>, <NUM>, <NUM>) which is configured for engagement with the driver for rotation of the coil to draw tissue inwardly,
characterized in that,
the implant coil having an anti-rewind feature (<NUM>), said driver comprises a driver coil and the implant coil is interfaced to the driver coil, and in that
the implant coil comprises an interface (<NUM>) comprising a flare or a step that abuts against the driver coil, said flare or step providing a push point of the implant coil for transfer of force to drive the implant into a tissue body.