Patent Publication Number: US-2009222031-A1

Title: Adjustable gastric band

Description:
This present invention relates to an inflatable, adjustable implantable band for encircling an anatomical passageway to create an artificial stoma. The band is of the kind comprising a flexible band shapeable to a ring and means for adjusting the internal diameter of the ring. 
     In particular the invention relates to a gastric band for encircling the stomach for the control of obesity. 
     Gastric bands have provided an effective alternative to gastric bypass, resections and other irreversible surgical weight loss treatments for the morbidly obese persons. The volume of the stomach is reduced in a surgical procedure in which a gastric band is arranged around an upper portion of the patient&#39;s stomach. A stoma is formed that is less than the normal interior diameter of the stomach. The stoma restricts food passing from the upper portion to a lower portion of the stomach and the digestive tract, so that food held in the upper portion of the stomach provides a feeling of fullness that discourages overeating. The patient will feel comfortably full with a small amount of food. And because of the slow emptying, the patient will continue to feel full for several hours reducing the urge to eat between meals. 
     European patent application EP 1547549 A2 relates to a mechanically adjustable gastric band of the non-inflatable kind. This known gastric band is composed of contractable and extendable mesh-formed elements with the object of being able to generate finite adjustments of the band. In the surgical procedure the surgeon heats the elements by application of electrical energy selectively to one or more of the elements, and in order for the elements to be operated individually in that way, the elements are electrically isolated from each other inside a surrounding band. Since cooling cannot be made by means of application of electrical energy the contractable and extendable elements are shape set to either tighten or loosen the gastric band. The band is complicated to operate and involve the risk of local heat spots. The electric current may damage both the surrounding band, the isolation between the contractable and extendable elements, and in worse case the surrounding tissues, with the risk of rupturing the encircled organ. 
     Other gastric bands are known from European patent applications EP1491167 and EP1303237, and from U.S. patent application US2005192531. 
     A feature common to all known gastric bands is the need of latching means. Respective mating latching components or sutures are provided at each end of the gastric band and used for providing the band with the shape required for forming a stoma suitable for the patient&#39;s need. 
     When latching and/or suturing the above known rings the surgeon must be very careful to avoid injuring the application site, e.g. the stomach wall. The tissue section of the stomach wall, between the mating latching components being drawn together by the surgeon for strapping the band, is at great risk being trapped and squeezed between said components. Blood supply is cut off, the tissue section degenerates and necrosis and infection are triggered. A further risk of damaging the tissue at the application site comes from the various surgical tools required for approaching the mating latching components into coupling relationship. 
     An inflatable balloon or cuff is often used for final adjustment of the diameter of the closed ring to the correct stoma size. However, the prior art gastric bands are not entirely circular in the closed stage, and as a result the balloon kinks during inflation. Areas of tissue are easily trapped at the kink and necrosis develops resulting in weakening of the stomach wall and even ulceration. 
     Adjustable gastric bands are intended implanted for very long periods of time including lifelong implantation in the human body. To operate the implant from outside most devices are provided with a subcutaneous fluid injection access port in communication with the adjustable gastric band. The shape and internal diameter of the band is adjusted using a needle for injecting a fluid through a silicone septum of the injection access port. Once the needle is removed, the septum seals against the hole by virtue of compressive load generated by the septum. Such injection access ports are known to the person skilled in the art and are not objects of the present invention. 
     In a first aspect according to the present invention is provided a surgically implantable band of the kind mentioned in the opening paragraph, said band being without sharp edges and being laparoscopically implantable and removable. 
     In a second aspect according to the present invention is provided a surgically implantable band of the kind mentioned in the opening paragraph having an adjustable internal diameter and is able to maintain a ring-shape without latching means. 
     In a third aspect according to the present invention is provided a surgically implantable band of the kind mentioned in the opening paragraph which provides an evenly distributed contact pressure to the stomach wall. 
     In a fourth aspect according to the present invention is provided a surgically implantable band of the kind mentioned in the opening paragraph which does not chafe, cut or clamp adjacent tissue. 
     The novel and unique feature whereby this is achieved according to the present invention is the fact that the flexible band, shapeable to a ring, is comprised of a flexible tube having a first lumen enclosing at least one band or wire of a material having a thermal shape memory. 
     The shape memory effect describes the process of restoring the original shape of a plastically deformed sample. 
     A material, which is both highly deformable and able to recover a pre-selected basic shape, e.g. a ring-shape, can be introduced through a very small incision in a laparoscopic procedure or other minimal invasive procedure. A flexible ring-shaped band or wire of memory shape material is easy to straight out. The straightened out tube-surrounded band or wire is applied adjacent a prearranged chosen zone of e.g. the stomach and allowed to recover its basic ring-shape in order to encircle the chosen zone and provide a stomach zone of reduced cross-section, the stoma. The zone is encircled in an instant. The upper portion of the stomach constitutes the new stomach reservoir of reduced size. After recovery of its basic ring-shape the memory shape material has the same diameter as before deformation and makes up the rigid backbone of the implantable band. The tube enclosing the memory shape material advantageously protects the stomach wall from being injured during shape recovery. Because the memory shape material is a thermal memory shape material and the band at the same time is inflatable, e.g. by means of hot or cool liquid, the three-dimensional shape can be affected and altered in an easy manner without the current risk of damaging the surrounding tissue as with the known gastric bands using electric current. Preferably, the at least one band or wire is a continuous band or wire extending along substantially the entire length of the flexible tube, so that the gastric band is self-supported at all temperatures. No additional means are needed for obtaining the ring shape other than the band itself and the thermal application. Due to the continuousness of the band or wire the gastric band is able to hold its entirely circular geometry and shape in the closed stage. 
     This unique property is further improved if the continuous band or wire is solid and non-perforated. 
     In juxtaposition to the first lumen, along the internal diameter of the ring, the flexible tube can be provided with an inflatable/deflatable second lumen for precision adjustment of the internal diameter of the ring-shaped implantable band. When the second lumen is inflated the internal diameter can be further reduced if desired. This situation arises if the weight loss has been insufficient or is smaller than expected. The second lumen exerts a radial gentle, equally distributed pressure on the stomach wall. All angular segments of the annulus are subjected to substantially the same radial force. 
     Another situation arises if the pressure on the annulus is to be relieved. If this situation arises the second lumen of the flexible tube can be deflated to increase the diameter of the ring. The negative pressure inside the second lumen advantageously reduces the pressure on the stomach wall. 
     The medium used for inflating the second lumen is typically a liquid such as saline or water. If hot saline is introduced into the first lumen the application of heat to a cooled band or wire will trigger said band or wire to recover its basic shape. The heat transfer is especially effective if the second lumen is the first lumen, since more fluid can be supplied to the flexible tube in less time. However, in this embodiment it can be problematic to control the radial pressure on the stomach wall. 
     A much better control of the radial pressure is obtained if the second lumen is put in fluid communication with the first lumen. Upon inflation, first the first lumen is inflated with warm fluid to allow the straightened out ring to recover its shape. Second, the internal diameter of the ring-shaped adjustable implantable band is adjusted, by filling the second lumen to the desired and required extent. However, since the two lumens communicate the process is very fast. 
     Access to the first and second lumens of the flexible tube can in a preferred embodiment be obtained via an inlet catheter and an outlet catheter having first ends coupled to an implantable fluid access port and second ends coupled to an inlet port and an outlet port, respectively, in the wall of the flexible tube. The fluid access port, which is subcutaneous implanted, is known to persons skilled in the art and will not be described further. 
     The inventors of the present invention have found that if a medical grade binary Nitinol alloy is selected as the material having a thermal shape memory excellent results are achieved. 
     Nitinol, which is an acronym for NIckel TItanium Naval Ordnance Laboratory, is a family of intermetallic shape memory materials exhibiting unique memory shape behaviour. Nitinol contains a mixture of app. 55% wt. nickel. The rest are titanium or titanium with an admixture of other elements, which are added to adjust or tune the material properties. 
     The exceptional properties of Nitinol are a result of a crystalline phase change known as “thermoelastic martensitic transformation”. Below the transformation temperature, the alloy is soft and martensitic. Heating the material converts the material to its high strength, austenitic condition. The transformation from austenite to martensite (cooling) and the reverse cycle from martensite to austenite (heating) do not occur at the same temperature. There is a hysteresis curve for every Nitinol alloy that defines the complete transformation cycle. The shape memory effect is repeatable. [“Shape Memory Alloys”, Edited by Hiroyasu Funakubo, Gordon and Breach Science Publishers, 1987, ISBN 2-88124-136-0]. 
     The preferred material for the flexible tube is a medical grade silicone polymer. Such silicone polymers have been used for years and is recognized as biological acceptable. Silicone polymers have a very smooth surface and are not susceptible to ingrowth of tissue and leakage of encapsulated fluid. 
     The flexible band is manufactured so that at body temperature the basic shape is a substantially closed ring. The composition of the memory shape material is carefully chosen to comply with this condition. 
     In a first embodiment the inflatable adjustable, implantable band can be designed so that a first end of the flexible band at least partly overlaps a second end of the band. As it may be both the memory shape material and the flexible tube overlaps or only the ends of the flexible tube overlaps. For example the ends can overlap at an interfacial angle. 
     In a second preferred embodiment the inflatable adjustable, implantable band can be designed so that a first end and a second end of the flexible band of the band abut each other to form a complete enclosure. 
     In a third preferred embodiment the inflatable adjustable, implantable band can be designed so that an interstice or small gap is left between a first end and a second end of the flexible band, thereby leaving the option of further closing the implantable band at a later stage. 
     In all embodiments the ring is open. The inflatable inflatable, adjustable, implantable band is designed to resist a load of at least 5 kg at body temperatures between approximately 35-40°. If the stoma is in risk of being occluded by e.g. a lump of food, the 5 kg upper limit eventually will be exceeded and the flexible ring yields to allow passage of the lump. 
     The inflatable adjustable, implantable band according to the present invention can be used as a gastric band or as an oesophageal band, for e.g. variceal ligation. 
     The invention also relates to a method for application of the band, including transforming and adjusting the three-dimensional shape of the inflatable adjustable, implantable band according to the present invention. 
     The method comprises changing the crystalline phase of the implantable initially ring-shaped band including thermal shape memory material according to the present invention by cooling at or below a first temperature T mar  to provide a martensitic low temperature phase in which the band is straightened out, locating the martensitic straightened out ring at the application site, optionally during sustained cooling in a period, subjecting the martensitic ring to thermal application at or above a second temperature T aus  to provide an austenitic temperature phase in which the band recovers its ring-shape. 
     The austenitic temperature T aus  can be reached by simply flushing the first and/or the second lumen with a fluid having a temperature above T mar . The first temperature T mar  of the implantable band in which the band is straightened out can be obtained by pre-cooling on ice or storing in a freezer. Sustained cooling can be obtained by flushing the first and/or the second lumen with a fluid having a temperature below T ma . 
     Another way of reaching the austenitic temperature T aus  is upon contact with the application site of body temperature. Thermal conduction will promptly trigger recovery of the basic ring shape and the surgeon much take care that the implantable band not unintentionally is applied on the wrong application. It is therefore preferred in this embodiment to continuously supply cold fluid to the lumens. 
     Supply of fluid in at least the second lumen is made as described above using a subcutaneous implanted access port to adjust the internal diameter of the ring. Furthermore, via said access port the second lumen can be deflated or inflated to change the pressure in said second lumen, and accordingly adjust the radial pressure on the stomach wall, e.g. to avoid chafing. 
    
    
     
       The invention will be explained in greater detail below, describing only exemplary embodiments with reference to the drawing, in which 
         FIG. 1  shows schematically a side view of an adjustable implantable gastric band according to the present invention installed around the stomach of a patient, 
         FIG. 2  is a perspective view of a first embodiment of an adjustable implantable gastric band according to the present invention. 
         FIG. 3   a  is a sectional view taken along the line III-III of  FIG. 2 , illustrating the flexible band without pressure application of the second lumen, 
         FIG. 3   b  shows the same applied with a positive pressure, 
         FIG. 3   c  shows the same applied with a negative pressure, 
         FIG. 4  corresponds to  FIG. 3   a  but the three adjacent memory shape metal rings are substituted with a flat memory shape band, 
         FIG. 5  is a perspective view of the first embodiment shown in  FIG. 2 , without the fluid access port, but cooled and straightened out ready for application in a patient, 
         FIG. 6  shows schematically a cross-section of the flexible ring taken along the line VI-VI in  FIG. 2  of the inflated adjustable implanted band shown in  FIG. 3   b,    
         FIG. 7  is a perspective view of a second embodiment of an adjustable implantable gastric band according to the present invention, and 
         FIG. 8  a perspective view of a third embodiment of an adjustable implantable gastric band according to the present invention. 
     
    
    
     Below, the invention is described by way of example on the assumption that the memory shape material is medical grade nitinol and the tube material is medical grade silicone. However, the invention is not limited to these specific materials and other materials having similar or identical physical, mechanical and chemical characteristics may be used without departing from the scope of the present invention. 
       FIG. 1  teaches how the adjustable implanted band  1  according to the present invention is installed on the stomach  3  of a patient  2 . The band  1  divides the stomach  3  in an upper portion  4  and a lower portion  5  intercommunicating via the stoma  6 . Opposite the stoma  6  the upper portion  4  extend into the oesophagus  7 , and the lower portion  5  extend into the small intestine  8 . 
     Immediately after completion of the surgical implantation the upper portion  4 , now being the new stomach, has a volume of approximately 15 ml, said volume expanding to approximately 60-80 ml. 
     An enlarged perspective view of a first embodiment for a band  1  is shown in  FIG. 2 . 
     The band  1  has a flexible band  9  consisting of a silicone tube or sleeve  10  surrounding a nitinol ring  11  (indicated in dot-dash line). The flexible band  9  has a first end  12  with a protruding end part  13  and a second end  14  with a protruding end part  15 . The protruding parts  13 , 15  have complement shapes enabling said protruding end parts  13 , 14  to both radially and circumferentially overlap each other to form a complete ring  9  or annulus for encircling the stoma  6 . No latching means is provided nor required for holding the ring-shape. 
     An inlet catheter  16  and an outlet catheter  17  constitute fluid conduit means between a fluid access port  20  and the flexible band  9 . The catheters  16 , 17  have first ends  18 , 19  connected to the fluid access port  20  and second ends  23 , 24  connected to the wall  27  of the silicone tube  10  via inlet port  25  and outlet port  26  to allow access to the lumens of said tube  10 . A fluid such as saline is introduced via a self-sealing septum  21  of the fluid access port  20 . Opposite the septum  21  the port  20  has a fixation face  22  provided for subcutaneous fixation by means of sutures at a distance from the stoma  6 . The septum  21  is accessible and penetratable from outside the patient by means of a needle. The length of the catheters  16 , 17  is determined by the location of the fluid access port  20  and the application site of the band  1 , taking in consideration that the implant must not cause any inconvenience to the patient at all. 
     The internal design of the flexible band  9  is more clearly understood from  FIGS. 3   a ,  3   b , and  3   c.    
       FIG. 3   a  shows a sectional view of the flexible band  9  composed of the silicone tube  10  and three nitinol rings  11   a , 11   b , 11   c . The nitinol rings are enclosed in a flushable, first lumen  28  of the tube  10 , said first lumen  28  extends along the exterior wall  27   a  in the ring condition of the flexible band  9 . A flushable second lumen  29  is defined concentric with and in fluid communication with the first lumen  28   a  along the interior wall  27   b  in the ring condition of the flexible band  9 . In  FIG. 3   a  the second lumen  29  is empty and no pressure is applied to the interior wall  27   b  of the tube  10 . 
     In  FIG. 3   b  the second lumen  29  is inflated as a balloon with e.g. saline to reduce the internal diameter of the flexible ring  9 . Due to the elasticity of the wall  27  of the silicone tube  10 , especially the interior wall  27   b , the balloon expands to a certain degree over the entire internal circumference without kinking. For the same reason, and because the band  1  is substantially closed, the inflating pressure is distributed evenly along the entire annulus. No tissue is trapped and the expanded band  1  does not chafe the stoma  6 . 
     Should relaxation of the applied pressure be needed, the condition of  FIG. 3   b  is reached by deflating the second lumen  29 . A negative pressure is used to alleviate stress and load, and prevent erosion of the stomach tissue around the stoma  6 . 
     Within the scope of the present invention the memory shape ring  11  can be made with a plurality of cross-section. and be composed of one or more continuous, concentric elements, as is clear from  FIG. 4 . 
       FIG. 4  corresponds substantially to  FIG. 3   c . The only difference is that the three nitinol rings  11   a , 11   b , 11   c  are substituted by a flat nitinol band  30 . 
     In  FIG. 5  the temperature T of the adjustable implantable band  1  has been reduced to below martensitic temperature T mar , e.g. a T mar  of 4°-6° C., to provide the flexible ring-shaped band  9  shown in  FIG. 2  with an elongated three-dimensional martensitic phase shape  9 ′, which allows the band  1  to be implanted through a very small abdominal incision. As long as the temperature T is kept below T mar , the elongated three-dimensional arc shape is maintained. 
     As an example a 2 mm thick nitinol ring [55.66 w % nickel, ≦0.05 w % carbon, ≦0.05 w % of the components cobalt, copper, iron, molybdenum, niobium, silicon and wolfram, the rest is titanium], which has a basic medium diameter of app. 42 mm. The ring opens at 5° C. into an elongated arc, in which the radius of a circle including said arc has a diameter of app. 100 mm. 
     To illustrate the fluid communication between the first lumen  28  and the second lumen  29  references are now made to  FIG. 6  showing a cross-section of an inflated fluid-filled, flexible ring taken along the line VI-VI in  FIG. 2 . including the inlet port  25 . 
     Saline at a temperature of app. 40° C. has been injected through the inlet port  25 , as indicated by the arrow A. The saline flows through the first lumen  28  as shown with dot-arrows to heat the nitinol ring  11  to trigger self-closing of the flexible martensitic band  9 ′ to provide the ring-shape as shown. The first lumen  28  communicates with the second lumen  29  and the injected saline continues into the second lumen  29 , which is expanded until the desired final internal diameter d is reached. The thickness of the internal wall  27   b  of the silicone tube  10  can be designed with various degrees of material thickness so further ensure that kinking is avoided. 
     The inflated implantable adjustable band  1  has an external diameter D when implanted. 
     It is also possible to extract saline after implantation, preferably until a negative pressure is created inside at least the second lumen  29 . In this condition the load on the internal stoma wall  27   b  is reduced. As a result, the risk of pathological conditions such as chafing, irritation, inflammation, erosion, necrosis and ulceration are most unlikely to happen. Moreover, the risk of the patient feels the band  1  is considerable reduced. 
       FIG. 7  shows a very simple second embodiment  31  of the adjustable implantable band according to the present invention. The band  31  corresponds substantially to the first embodiment  1  and for like parts are used same numerals. 
     In the second embodiment  31  the first end part  34  either abuts the second end part  35 , or leaves a small gap  36  open between the end parts  34 , 35 . The second embodiment is very simple to manufacture and is often preferred if the memory shape material is the continuous band  30  shown in  FIG. 4 . 
       FIG. 8  shows a third preferred embodiment  32 , which corresponds substantially to the first embodiment  1  and for like parts are used same numerals. 
     In the third embodiment  32  the end parts  37 , 38  overlap at complement slanting end faces  39 , 40  to define a perfect ring, which is able to flex against pressure and still be closed. 
     Common to the embodiments shown the flexible tube is a double lumen tube in which the nitinol band or wire  11  is enclosed in the first lumen  28 , and the second lumen  29  is inflatable from outside the patient to final adjustment of the internal diameter d and to a certain extent also the external diameter of the flexible ring  9 . Within the scope of the present invention the first and second lumens can be one and the same lumen enclosing the band or wire  10 . 
     Modifications and other uses of the above adjustable implantable bands according to the present invention are within the scope of the appended set of claims. 
     During load and stress tests the bands have been subjected to over 200.000 load contributions of 5 kg. No permanent deformation, metal fatigue, brittleness or leakage from the lumens of the tube have been observed. 
     The adjustable implantable band according to the present invention is seen by the present inventor to be superior to known bands. They are more easy to implant and more comfortable to the patient. Controlling and adjusting the internal diameter is very easy to perform, and just by adding cold saline or water to the lumens the ring will straighten out in an instant to be removed using any appropriate surgical keyhole procedure.