Abstract:
A device, including an implant for placement within a hollow body organ. The implant includes a member having an undeployed shape for delivery within a hollow body and one or more deployed shapes for implantation therein. The member has sufficient rigidity in its deployed shape to exert an outward force against an interior of the hollow body so as to bring together two substantially opposing surfaces of the hollow body. The device includes a means for changing the deployed shape of the member while implanted within the hollow body. The means includes an antenna configured to wirelessly communicate with an external device. The external device is configured to communicate telemetrically with the member. The device further includes at least one means to limit rotational movement of the antenna relative at least one of the member and the external device.

Description:
FIELD OF INVENTION 
       [0001]    The present application relates to methods and devices for fixing antenna orientation in a distension system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Obesity is a growing global concern, as the number of individuals classified as overweight, obese, or morbidly obese continues to increase every year. Obesity is associated with several co-morbidities, including hypertension, type II diabetes, and sleep apnea. Morbid obesity, defined as when a person is 100 pounds or more over ideal body weight or having a body mass index (BMI) of 40 or greater, poses the greatest risks for severe health problems. Accordingly, a great deal of attention is being focused on treating patients with this condition. One proposed method of treating morbid obesity has been to place a distension device, such as a, spring loaded coil inside the stomach. Examples of satiation and satiety inducing gastric implants, optimal design features, as well as methods for installing and removing them are described in commonly owned and pending U.S. patent application Ser. No. 11/469,564, filed Sep. 1, 2006, and pending U.S. patent application Ser. No. 11/469,562, filed Sep. 1, 2006, which are hereby incorporated herein by reference in their entirety. One effect of the coil is to more rapidly induce feelings of satiation defined herein as achieving a level of fullness during a meal that helps regulate the amount of food consumed. Another effect of the coil is to prolong the effect of satiety which is defined herein as delaying the onset of hunger after a meal which in turn regulates the frequency of eating. By way of a non-limiting list of examples, positive impacts on satiation and satiety may be achieved by an intragastric coil through one or more of the following mechanisms: reduction of stomach capacity, rapid engagement of stretch receptors, alterations in gastric motility, pressure induced alteration in gut hormone levels, and alterations to the flow of food either into or out of the stomach. 
         [0003]    One problem that can arise is giving stability to various housings in a distension system, such as an antenna housing for communicating with an external device. Specifically, it can be difficult to provide orientational stability to an antenna housing once it is implanted as the stomach does not provide a flat surface for mounting and the housing may shift locations as the patient loses or gains weight, or even during movement by the patient. As a result, it can be difficult to align an external device with the antenna housing to enable wireless communication. 
         [0004]    Accordingly, there remains a need for improved methods and devices for substantially fixing the orientation of an antenna housing implanted in the stomach. 
     
    
     
         [0005]    The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0006]      FIG. 1A  is a schematic diagram of one embodiment of a stomach distension system; 
           [0007]      FIG. 1B  is perspective view of an implantable portion of the stomach distension system of  FIG. 1A ; 
           [0008]      FIG. 2A  is a perspective view of a distension device of the distension system of  FIG. 1A ; 
           [0009]      FIG. 2B  is a perspective view of the distension device of  FIG. 2A  implanted in the stomach 
           [0010]      FIG. 3  is a perspective view of an injection port housing of  FIG. 1A ; 
           [0011]      FIG. 4  is a perspective view of the implantable portion of the stomach distension system of  FIG. 1A  showing a cross-sectional view of an antenna housing; 
           [0012]      FIG. 5  is a perspective, partially transparent view of the antenna housing of  FIG. 4 ; 
           [0013]      FIG. 6  is a perspective view of one embodiment of a constraining element disposed around at least a portion of the injection port housing and antenna housing of  FIGS. 2B and 4 ; 
           [0014]      FIG. 7  is a perspective view of the constraining element of  FIG. 6 ; and 
           [0015]      FIG. 8  is a perspective cross-sectional view of the constraining element of  FIG. 6  showing a lumen extending therethrough. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. 
         [0017]    Various methods and devices are provided for substantially fixing the orientation of a housing, such as an antenna housing, within tissue. In one embodiment, a distension system is provided having a first housing with a reservoir formed therein for receiving fluid. The first housing can be configured to be anchored to tissue. The system can also include a second housing spaced apart from and in fluid communication with the first housing. The second housing can have an antenna therein configured to wirelessly communicate with an external device. The system can also include a distension device in fluid communication with the first and second housings and adapted to cause distension in the stomach, and a constraining element coupled to the first and second housings and configured to limit rotational movement of the first and second housings relative to one another and possibly, relative to the distension system. In an exemplary embodiment, the constraining element is configured to substantially prevent rotation of the first and second housings along an axis extending between the first and second housings. In all cases, the distension device may be adjustable. Exemplary non-limiting examples of adjustable implantable distension devices (e.g., satiation and satiety inducing gastric implants), optimal design features, as well as methods for installing and removing them are described in commonly owned and pending U.S. patent application Ser. No. ______, filed on even date herewith and entitled “Devices and Methods for Adjusting a Satiation and Satiety-Inducing Implanted Device” [Atty. Docket No. END6514USNP], which is hereby incorporated herein by reference in its entirety. 
         [0018]    The constraining element can have various configurations. In one embodiment, the constraining element can be substantially rigid in a first plane of motion and flexible in a second plane of motion that differs from the first plane of motion. For example, the constraining element can be a sheath disposed around at least a portion of the first and second housings. In one embodiment, the sheath can be sealed with a hermetic coating. The system can also include a connector, such as a catheter, extending through the constraining element between the first and second housings. The connector can be configured to allow fluid flow therethrough between the first and second housings. Alternatively, the constraining element can include a lumen extending therethrough and configured to allow fluid flow between the first and second housings. The constraining element can also include other features, such as an outer layer formed from a compliant material, such as keratin and silicone. 
         [0019]    In another embodiment, a distension system is provided having a fill port with a needle-penetrable septum and a reservoir formed therein and configured to receive fluid. An antenna housing can be coupled to the fill port and it can have an antenna therein configured to wirelessly communicate with an external device. The system can also include a constraining element extending between the fill port and the antenna housing. The constraining element can be substantially rigid in a first plane of motion and flexible in a second plane of motion that differs from the first plane of motion. For example, the constraining element can prevent rotation between the antenna housing and the fill port. The constraining element can have various configurations, as discussed above. 
         [0020]    Exemplary methods are also provided for constraining movement of a housing in tissue, and in one embodiment the method can include implanting a first housing in tissue. The first housing can have a second housing spaced apart from but coupled thereto. A constraining element coupled between the first and second housings can substantially prevent rotational movement of the second housing relative to the first housing about an axis extending therebetween such that the second housing is maintained in a substantially fixed orientation in the tissue. The method can also include positioning an external device above in a lumen, and activating the external device to communicate with an antenna disposed within the second housing. In one embodiment, implanting the first housing in tissue can include anchoring the first housing to tissue. The first housing can contain fluid therein and the constraining element can include a lumen extending therethrough such that the fluid can flow between the first and second housings. The fluid can also flow through a catheter extending through the lumen in the constraining element. The method can also include implanting a distension device coupled to at least one of the first and second housings. The distension device can cause distension in the stomach. In a further embodiment, the second housing can include a sensor that measures the pressure of fluid in the distension device. 
         [0021]    Various exemplary methods and devices are provided for limiting movement of an antenna housing associated with a distension system to allow for alignment and communication with an external device. In certain exemplary embodiments, the antenna housing is constrained relative to another housing, such as an injection port  30 , that is anchored to tissue. In particular, a constraining element can be coupled to the housings and it can limit or substantially prevent movement of the housings relative to one another, preferably in at least one plane of motion. Since housings tend to shift once implanted in tissue, the ability to control movement between the housings can be particularly advantageous to allow for effective wireless communication with an external device. 
         [0022]    While the present invention can be used with a variety of distension systems known in the art,  FIG. 1  illustrates one exemplary embodiment of a stomach distension system  10 . As shown, The system  10  generally includes an implantable portion  10   a  having an adjustable gastric coil  20  that is configured to be positioned around the upper portion of a patient&#39;s stomach  40 , and an injection port  30  that is fluidly coupled to the adjustable gastric coil  20 , e.g., via a catheter  50 . The injection port  30  is adapted to allow fluid to be introduced into and removed from the gastric coil  20  to thereby adjust the size of the coil, and thus the pressure applied to the stomach. The injection port  30  can thus be implanted at a location within the body that is accessible through the tissue. Injection ports may be positioned in the stomach of the patient, attached to the gastric distention device. The implantable portion  10   a  can also include an antenna housing  60  configured to communicate wirelessly with an external device. 
         [0023]      FIG. 2A  shows the gastric coil  20  in more detail. While the gastric coil  20  can have a variety of configurations, and various gastric coils currently known in the art can be used with the present disclosure, in the illustrated embodiment the gastric coil  20  has a generally elongate shape with a support structure  22  having first and second opposite ends  20   a,    20   b  that can be formed in a C-shape. Various techniques can be used to keep the ends  20   a,    20   b  in relative proximity to one another. In the illustrated embodiment, the fluid bladder pressure may be varied to control the proximity of the ends relative to each other. The gastric coil  20  can also include a variable volume member, such as an inflatable balloon  24 , that is disposed or formed on one side of the support structure  22  and that is configured to be positioned adjacent to tissue. The balloon  24  can expand or contract against the outer wall of the coil to form an adjustable size coil for controllably restricting food intake into the stomach. 
         [0024]    A person skilled in the art will appreciate that the gastric coil can have a variety of other configurations. Moreover, the various methods and devices disclosed herein have equal applicability to other types of implantable coils. 
         [0025]      FIG. 2B  shows the adjustable gastric coil  20  applied in the stomach of a patient. As shown, the coil  20  at least substantially distends the stomach  40 . After the coil  20  is implanted, it may be deployed. A person skilled in the art will appreciate that various techniques, including mechanical and electrical techniques, can be used to adjust the coil. 
         [0026]    The fluid injection port  30  can also have a variety of configurations. In the embodiment shown in  FIG. 3 , the injection port  30  has a generally cylindrical housing with a distal or bottom surface and a perimeter wall extending proximally from the bottom surface and defining a proximal opening  32 . The proximal opening  32  can include a needle-penetrable septum  34  extending there across and providing access to a fluid reservoir (not visible in  FIG. 3 ) formed within the housing. The septum  34  is preferably placed in a proximal enough position such that the depth of the reservoir is sufficient enough to expose the open tip of a needle, such as an endoscopic Huber-like needle, so that fluid transfer can take place. The septum  34  is preferably arranged so that it will self seal after being punctured by a needle and the needle is withdrawn. As further shown in  FIG. 3 , the port  30  can further include a catheter tube connection member  36  that is in fluid communication with the reservoir and that is configured to couple to a catheter (e.g., the catheter  50 ). A person skilled in the art will appreciate that the housing can be made from any number of materials, including stainless steel, titanium, or polymeric materials, and the septum  34  can likewise be made from any number of materials, including silicone. 
         [0027]    As indicated above and as shown in  FIG. 4 , The system can also include an antenna housing  60  having an antenna  62  therein that is configured to communicate wirelessly with an external device to allow power and/or data to be transferred between the antenna and the external device. The antenna  62  can be, for example, a TET/telemetry coil for inductively coupling with a TET/telemetry coil in an external device (e.g., a device external to the patient&#39;s body). The antenna  62  can be coupled to various components disposed within the antenna housing  60  or elsewhere within The system  10 . For example, in one embodiment the antenna  62  can include or be coupled to a pressure measuring device that is in communication with the closed fluid circuit and that is configured to measure a fluid pressure that corresponds to the amount of distension applied by the adjustable gastric coil to the patient&#39;s stomach. Measuring the fluid pressure enables a physician to evaluate the distension created by a coil adjustment. In an exemplary embodiment, the pressure measuring device can be in the form of a pressure sensor  63 , which can be unitary with the antenna  62  or a separate component, that can be disposed within the housing  60 . The pressure measuring device can, however, be disposed anywhere within the closed hydraulic circuit of the implantable portion, and various exemplary locations and configurations are disclosed in more detail in commonly-owned U.S. Publication No. 2006/0211913 entitled “Non-Invasive Pressure Measurement In a Fluid Adjustable Restrictive Device, filed on Mar. 7, 2006, which is hereby incorporated by reference in its entirety. Optionally, the pressure sensing system can further include a temperature sensor (not shown). The sensing system can also be configured to measure a variety of other parameters, for example, pulse count and pulse width. In general, as shown in  FIG. 4 , the illustrated housing  60  includes an inlet  60   a  and an outlet  60   b  that are in fluid communication with the fluid in The system. The sensor can be disposed within the housing  60  and it can be configured to respond to fluid pressure changes within the hydraulic circuit and convert the pressure changes into a usable form of data. As shown in more detail in  FIG. 5 , the pressure sensing system can also include a motherboard  64  that can serve as at least a portion of a hermetic container to prevent fluid from contacting any elements disposed within the housing  60 , except as discussed for the sensor. The housing  60  can be made from any biocompatible material appropriate for use in a body, such as a polymer, silicone, ceramic, glass, biocompatible metal, and other similar types of material. Furthermore, the housing  60  can be made from any one or more of transparent (as shown in  FIG. 5 ), opaque, semi-opaque, and radio-opaque materials. The motherboard  64  including, among other elements, a microcontroller  65  (e.g., a processor), can also be disposed within the housing  60  to help process and communicate pressure measurements gathered by the sensor, and also possibly other data related to the coil  20 . As further discussed below, the motherboard  64  can also include a transcutaneous energy transfer (TET)/telemetry coil and a capacitor. Optionally, a temperature sensor can be integrated into the motherboard  64 . The microcontroller  65 , the TET/telemetry coil and/or antenna, the capacitor, and/or the temperature sensor can be in communication via the motherboard  64  or via any other suitable component(s). As indicated above, the TET/telemetry coil and/or antenna and capacitor can collectively form a tuned tank circuit for receiving power from the external portion  10   b  and transmitting pressure measurements to an external device, e.g., the reading device  70 . The microcontroller and capacitor can be in communication via the motherboard or via any other suitable component(s). The antenna  62  disposed in the housing  60  can have a variety of configurations, but in the illustrated embodiment is in the form of a planar coil on the motherboard  64 . The antenna  62  can be configured to emit field lines directed along an axis extending between superior and inferior surfaces of the housing  60 . This can allow for optimal communication between the antenna  62  and an external device as it is preferable for the antenna  62  to be maintained in a position substantially parallel to a tissue surface. Additionally, the antenna may take advantage of the configuration and orientation of the gastric coil as a support frame. In such a configuration, the antenna may be made very large relative to one such as could be achieved if implanted subcutaneously. The larger antenna would allow greater transmission distance for information and greater coupling efficiency for transcutaneous energy transfer (TET). Alternatively, if properly tuned, the gastric coil may itself be the antenna. If the structure of the coil is a single piece of metal such as a shape memory alloy, or a spring steel, it may be a single piece antenna. Alternatively, if the coil is a multi part structure, a single wire may be stretched along the components of the coil to form the antenna. 
         [0028]    Various pressure sensors known in the art can be used, such as a wireless pressure sensor provided by CardioMEMS, Inc. of Atlanta, Ga., though a suitable MEMS pressure sensor may be obtained from any other source, including but not limited to Integrated Sensing Systems (ISSYS), and Remon Medical. One exemplary MEMS pressure sensor is described in U.S. Pat. No. 6,855,115, the disclosure of which is incorporated by reference herein for illustrative purposes only. It will also be appreciated that suitable pressure sensors may include, but are not limited to, capacitive, piezoresistive, silicon strain gauge, or ultrasonic (acoustic) pressure sensors, as well as various other devices capable of measuring pressure. 
         [0029]    As discussed above, The system can include a constraining element coupled between first and second housings and configured to limit movement between first and second housings. This will allow the port  30 , for example, to be anchored to tissue and the antenna housing  60  to be maintained in a substantially fixed orientation relative to the port  30 . As a result, the antenna housing  60  can be maintained in a position substantially parallel to a tissue surface, thus allowing optimal communication between the antenna  62  and an external device. In an exemplary embodiment, the constraining element can be in the form of a sheath  100  extending between and optionally disposed around at least a portion of the injection port  30  and the antenna housing  60 . The sheath  100  can be constructed to limit movement, e.g., rotational/torsional movement, between the housings preferably about an axis extending therebetween. Movement can be completely prevented, or merely limited in one or more directions or planes of motion. In an exemplary embodiment, as shown in  FIG. 6 , the sheath  100  has a first portion  100   a  configured to fit around the injection port  30 , a second portion  100   b  adapted to extend between the injection port  30  and the sensor housing  60 , and a third portion  100   c  adapted to fit around the sensor housing  60 , as will be discussed in more detail below. 
         [0030]    The sheath  100  can be formed from a variety of materials, and it can be rigid or flexible, but in the preferred embodiment the sheath  100  is at least semi-rigid to limit movement between the injection port  30  and the sensor housing  60 . For example, the sheath  100  can be formed from an elastomeric material. In addition, the sheath  100  can be formed from a hermetic or near-hermetic material as the sheath  100  can also be configured to form a seal around the injection port  30  and the sensor housing  60 . This seal can be configured to substantially eliminate transport of materials both into and out of the sheath  100  in order to provide protection to the components housed within the sheath  100 , including the components housed in the injection port  30  and the sensor housing  60 . A hermetic seal can be achieved with a variety of hermetic materials, such as laser welded titanium. A person skilled in the art will appreciate that the sheath  100  can be formed from any material that has the ability to form a hermetic seal using any known technique for forming a seal, including AuSn brazing, anodic bonding, seam welding, or impulse welding. A near-hermetic seal can be achieved using a variety of near-hermetic materials to form the sheath  100 , such as materials configured to slow the ingress of moisture through the sheath. A near-hermetic seal can also be achieved through the use of a coating formed around the sheath. A person skilled in the art will appreciate that a variety of materials can form a near-hermetic seal, including but not limited to silicones, metallized LCP, parylene-C, PDMS, and PEEK. Moreover, a person skilled in the art will appreciate that a variety of technologies can be used to form a coating around the sheath  100 , including nanoreinforced moisture barrier coatings and self-aligned nano-particle engineered surfaces. In addition, the sheath  100  can also be formed from a keratin. This can be advantageous as keratin is less likely to react or be rejected by the body as it is a substance found in the body, it is less susceptible to humidity, it can be gamma sterilized, and can be injection molded to form the various components of the sheath  100 . Keratin has also been shown to accelerate tissue healing as it can cooperate with the body&#39;s healing mechanisms. A person skilled in the art will appreciate, however, that the sheath  100  can be formed from any material that can be implanted in the body and that can provide limitation of movement between the housings as described above. 
         [0031]    As discussed above, the first and third portions  100   a,    100   c  of the sheath  100  can have any configuration that allows the sheath to fit around and/or mate to the injection port  30  and the antenna housing  60 , and the sheath  100  can be formed in a variety of ways. For example, the first portion  100   a  of the sheath  100  can be overmolded to encompass a portion of the injection port  30 , but preferably not the entire injection port  30 . Specifically, at least the septum  34  extending across the injection port  30  will not be encompassed by the sheath  100  as the septum  34  is configured to provide access to the fluid reservoir formed within the housing of the injection port  30 . The sheath  100  can, however, be needle-penetrable to allow fluid to be introduced into an injection port  30  fully encapsulated by the sheath  100 . In an exemplary embodiment illustrated in  FIG. 7 , the first portion  100   a  of the sheath  100  is formed around an engagement flange  104  formed on or matable to the injection port  30 . The third portion  100   c  of the sheath  100  can likewise be overmolded to encapsulate a portion of or preferably the entire housing  60 . A person skilled in the art will appreciate that as much or as little of the injection port  30  and/or the housing  60  can be encapsulated by the sheath  100 , but preferably the sheath  100  is configured to provide enough of a seal to protect the components within the injection port  30  and the antenna housing  60  and provide enough stability to the injection port  30  and the housing  60  to limit movement therebetween. In other embodiments, the sheath  100  need not include the first and third portions  100   a,    100   c,  but rather can merely extend between the port  30  and the housing  60  without encapsulating the port  30  and the housing  60 . 
         [0032]    In another embodiment, the distension system may serve to maintain the fixed space relationship between the port and the housing since the geometry of the coil lies substantially in a plane. Thus, if the connecting web stabilizing the injection port and the housing is also itself stabilized by coil, the spatial relationship of the port and housing is assured. 
         [0033]    The second portion  100   b  of the sheath  100  can also have a variety of configurations. In an exemplary embodiment, the second portion  100   b  includes a lumen  102  extending therethrough that is configured to allow for fluid flow between the injection port  30  and the antenna housing  60 . In one exemplary embodiment, the lumen  102  can contain a catheter  50 , as shown in  FIG. 6 , extending therethrough to allow for fluid flow through the catheter  50  between the injection port  30  and the antenna housing  60 . This can be achieved either by forming the sheath  100  around the catheter  50 , or the catheter  50  can be routed through the lumen  102  extending through the sheath  100 . The catheter  50  can have a variety of configurations, but is preferably sized and shaped to fit within the lumen  102  of the sheath  100 . The catheter  50  can have a length that allows the catheter  50  to extend a distance between the injection port  30  to the antenna housing  60  such that the port  30  and the housing  60  are spaced a distance apart. In another exemplary embodiment, the lumen  102  of the sheath  100  can be configured to allow fluid flow therethrough without the need for a catheter  50  within the lumen  102 . The lumen  102  can have any size and shape that allows for fluid to flow between the injection port  30  and the sensor housing  60 . 
         [0034]    As previously indicated, the second portion  100   b  of the sheath  100  is also preferably adapted to limit movement between the port  30  and the housing  60 . While various techniques can be used to limit movement, in an exemplary embodiment the second portion  100   b  can be configured to provide rigidity in any or all planes or axes of movement. In one exemplary embodiment, the second portion  100   b  of the sheath  100  is configured to limit movement about an axis A ( FIG. 6 ) extending between the port  30  and the housing  60  to prevent rotational movement between the injection port  30  and the housing  60 . A person skilled in the art will appreciate that the rigidity and/or shape of the second portion  100   b  of the sheath  100  can be chosen to achieve a desired amount of constraint on movement. For example, the rigidity and/or shape of the second portion  100   b  of the sheath  100  can be selected to allow the injection port  30  and the housing  60  to be easily introduced in the body, for example, by allowing bending motion into and out of a plane containing the sheath  100 , the port  30 , and the housing  60 . However, the rigidity and/or shape of the sheath  100  can prevent torsional movement of the injection port  30  and the housing  60  about the axis A extending between the port  30  and the housing  60  to keep the antenna  62  within the antenna housing  60  in a specific orientation in relation to the port  30 , and thus the skin surface. This can be advantageous as it allows for implantation of the antenna  62  in a specific and known position and orientation in relation to the port  30  and thus the skin surface to increase the ease with which the antenna  62  can communicate with an external device positioned adjacent the skin surface. In addition, the rigidity and/or shape of the second portion  100   b  of the sheath  100  can also be selected to allow the catheter  50  to be easily routed through the lumen  102  formed in the sheath  100  in an embodiment described above in which the sheath  100  is not formed around the catheter and the catheter needs to be inserted through the lumen  102 . For example, if the injection port  30  is not placed in the same plane as the antenna housing  60 , the rotational stability provided by the sheath  100  can increase the ease with which the catheter is positioned within the lumen  102  in the sheath  100 . 
         [0035]    In an exemplary embodiment, as shown, the second portion  100   b  of the sheath  100  can have a shape that allows for bending between the port  30  and the housing  60  but prevents rotation therebetween. As best shown in  FIG. 8 , the second portion  100   b  of the sheath  100  has a generally elongate substantially flat configuration that limits or prevents rotational movement between the injection port  30  and the antenna housing  60  along the axis A of the second portion  100   b  of the sheath  100 , but yet allows bending to occur along the axis A. In particular, the second portion  100   b  of the sheath  100  has a width w that is greater than a height h. The shortness of the height h is chosen to allow the port  30  and the housing  60  to bend in a first direction (i.e., in an out of a plane extending through the port  30  and the housing  60 ) while the wider width w prevents bending in a second direction that is substantially perpendicular to the first direction. In other words, the port  30  and the housing  60  can move up and down out of the plane in the direction U, D indicated in  FIG. 8 , but are prevented from moving sideways within the plane in the direction S indicated in  FIG. 8 , in addition to being prevented from rotating relative to one another along the axis. This results in the limitation of rotation about the axis A extending between the port  30  and the housing  60 . In other words, the sheath  100  can act as a spring to prevent twisting about the axis A of the second portion  100   b  of the sheath  100  (i.e., the axis A extending between the housings). The sheath  100  can also have a flat distal surface that facilitates positioning of the sheath  100  on a tissue surface during and after implantation, and a convex proximal surface that can be curved to accommodate the lumen  102  extending through the second portion  100   b  of the sheath  100 , while still maintaining a low profile. The second portion  100   b  of the sheath can also extend between the port  30  and the housing  60  between distal portions of the port  30  and the housing  60  to allow the flat distal surface of the sheath  100  to be co-planar with the distal surfaces of the port  30  and the housing  60 , and thus the sheath  100 , the port  30 , and the housing  60  can rest on a tissue surface in one plane, for example, to ease implantation and anchoring the port  30  to tissue. A person skilled in the art will appreciate, however, that the second portion  100   b  of the sheath  100  can have any configuration adapted to limit movement between the injection port  30  and the housing  60 . 
         [0036]    In another exemplary embodiment, the housings may advantageously be constrained to lie in the plane of the coil formed by the C-shape. If the coil is sufficiently distended, it will be limited in its orientation to the plane of the stomach in which lies the greater and lesser curves of the stomach. Thus, a substantial perpendicularity with the tangent to the surface of the skin above the stomach will be maintained, facilitating orientation relative to an external reader unit or TET coil. 
         [0037]    In use, the distension system  10  shown in  FIG. 1A  can be implanted using techniques known in the art. For example, the gastric coil  20  can be introduced into the patient&#39;s body and positioned in the stomach to distend the stomach, thus limiting triggering various mechanisms of satiation and satiety. The housing  60  and the port  30  can be implanted in a lumen, preferably in the stomach, and they can be coupled to the coil  20  to allow fluid communication therebetween. Preferably, the port  30  is anchored to a distension device, such that the port  30  is substantially parallel to the skin surface to allow access to the port  30 . As a result of the position of the port  30 , the antenna housing  60 , which is spaced a distance apart from the port  30  and preferably positioned on the fascia, will be limited or prevented from moving due to the constraining member. 
         [0038]    After implantation, it is necessary to be able to communicate with the distension system, for example, to transmit power to the distension system and/or communicate data to and from the distension system. Since the sheath  100  limits or prevents movement of the housing  60  containing the antenna  62  relative to the injection port  30 , an external device placed on the skin surface above the housing  60  will be aligned with and can thus communicate with the antenna  62 . For example, the sheath  100  can prevent rotational movement between the port  30  and the housing  60  along an axis extending therebetween, while allowing for bending in a plane of motion substantially perpendicular to the axis extending between the port  30  and the housing  60 . This prevention of rotational movement will allow the antenna  62  and the external device to be substantially parallel to one another as the sheath  100  prevents the antenna  62  from rotating away from the plane of the port and reader. 
         [0039]    The devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, the device can be disassembled, and any number of the particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present invention. 
         [0040]    Preferably, the invention described herein will be processed before surgery. First, a new or used instrument is obtained and if necessary cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and instrument are then placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation kills bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container keeps the instrument sterile until it is opened in the medical facility. 
         [0041]    It is preferred that device is sterilized. This can be done by any number of ways known to those skilled in the art including beta or gamma radiation, ethylene oxide, steam. 
         [0042]    Any patent, publication, application or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. 
         [0043]    One of ordinary skill in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.