Abstract:
A multi-section stent includes a connecting structure that allows the stent sections to move and flex relative to one another. For deployment and positioning, the connecting structure connects the multiple stent sections and holds the stent sections substantially stationary relative to one another. Following deployment, the connecting structure allows the multiple stent sections to move relative to one another. Movable stent sections enable flexure of the stent upon deployment within a body lumen. This flexing structure allows better conformance of the stent to the shape of the body lumen, and exerts less overall pressure against the lumen wall, reducing the potential for trauma. Upon deployment, the multiple stent sections may be completely detached from one another. Alternatively, the stent sections may remain partially connected in a manner that allows substantial independent movement. The connecting structure can be manufactured to separate upon deployment, for example, by breaking or degrading within the body lumen in which the stent is positioned.

Description:
TECHNICAL FIELD 
     The present invention relates to medical prostheses and, more particularly, to intraluminal medical stents. 
     BACKGROUND 
     Medical stents are used within the body to restore or maintain the patency of a body lumen. Blood vessels, for example, can become obstructed due to plaque or tumors that restrict the passage of blood. A stent typically has a tubular structure defining an inner channel that accommodates flow within the body lumen. The outer walls of the stent engage the inner walls of the body lumen. Positioning of a stent within an affected area can help prevent further occlusion of the body lumen and permit continued flow. 
     A stent typically is deployed by percutaneous insertion of a catheter or guide wire that carries the stent. The stent ordinarily has an expandable structure. Upon delivery to the desired site, the stent can be expanded with a balloon mounted on the catheter. Alternatively, the stent may have a biased or elastic structure that is held within a sheath or other restraint in a compressed state. The stent expands voluntarily when the restraint is removed. In either case, the walls of the stent expand to engage the inner wall of the body lumen, and generally fix the stent in a desired position. 
     SUMMARY 
     The present invention is directed to a multi-section stent. The stent incorporates a connecting structure that permits the multiple sections to move relative to another, promoting flexibility and conformance of the stent to a body lumen. For deployment and positioning, the connecting structure holds the stent sections substantially stationary relative to one another. Following deployment, however, the connecting structure allows the multiple stent sections to move relative to one another. 
     The connecting structure can be made to separate or relax such that the stent sections are able to move relative to one another. The connecting structure can be made to separate or relax by the use of a material that breaks or degrades. Movement of the stent sections may refer to axial movement, lateral movement, tilting, pivoting, rotation, and the like, all of which promote flexibility of the overall stent structure. 
     Movable stent sections enable flexure of the stent upon deployment within a body lumen. This flexing structure allows better conformance of the stent to the shape of the body lumen, and exerts less overall pressure against the lumen wall, reducing the potential for trauma Following separation or relaxation of the connecting structure, the multiple stent sections may be completely detached from one another. Alternatively, the stent sections may remain partially connected in a manner that allows substantial independent movement. 
     The connecting structure can be manufactured to separate, e.g., by breakage, tearing, rupture, etc., thereby disconnecting at least portions of adjacent stent sections to allow increased flexibility. Alternatively, the separable connecting structure can be made from a degradable material that dissolves or otherwise degrades within the body lumen. As a further alternative, the connecting structure may connect the stent sections in a non-rigid manner, allowing movement while retaining interconnection between the stent sections. In any of the above cases, adjacent stent sections become more movable relative to one another, allowing the stent to flex and adapt to the body lumen. Each of the individual stent sections may settle into a substantially fixed position, however, and heal into the luminal wall. 
     A separable connecting structure can be made responsive to intra-luminal forces or external forces applied upon deployment. To promote separation by breakage, a continuous stent structure can be weakened, e.g., by thinning, perforation, scribing, or pre-stressing, at selected intervals along the length of the stent. Alternatively, discrete connecting members can be formed between stent sections to provide a series of connected stent sections. The connecting members are manufactured to separate under intraluminal forces, thereby disconnecting the stent sections. To promote early separation or breakage, the deployment technique may involve forcibly breaking at least some of the connecting members. In many cases, however, gradual separation or breakage under intraluminal forces will be sufficient. 
     A connecting structure incorporating a degradable material can be selected to dissolve within the body fluids present within the body lumen in which the stent is positioned. Early degradation can be promoted by pretreating the material, e.g., with a solvent, just prior to deployment. Also, an agent may be introduced into the body to accelerate degradation. If the connecting structure comprises a collagen coating, for example, an enzyme dosage can be administered to the patient to promote degradation. Gradual degradation will be sufficient in most applications, however, simplifying preparation. With degradable materials, therapeutic substances can be added for release into the body lumen as the materials degrade. 
     As an alternative, the stent can be covered with a brittle or degradable laminating coat that covers at least a portion of the stent, forming a housing for the stent sections. This housing can provide a substantially rigid but separable interconnection of the stent sections. Upon deployment, the housing breaks or degrades to permit greater flexibility among the stent sections. Another alternative is the use of a housing in the form of a breakable or degradable netting or cage that holds the sections together. Upon deployment, the netting or cage can be made to break or degrade, and thereby release the stent sections relative to one another. 
     Separable connecting portions, whether degradable or breakable, can be selected and manufactured to minimize the risk of releasing larger particles or fragments into the body lumen that could lead to embolism or other serious problems. The stent sections may be completely separated, i.e., disconnected, following breakage of the connecting structure, forming a series of discrete stent sections that extend along the body lumen. Alternatively, the stent sections may remain partially connected, but still provide improved flexibility. For example, material joining adjacent stent sections may remain partially intact to allow flexibility but limit movement. 
     As further alternatives, the stent sections can be connected with interlocking links, such as loops or chain-links, that allow the stent sections to move, but serve to restrict the overall extent of movement. In some embodiments, the interlocking links may overlap, with degradable or breakable material filling the overlap area to hold adjacent stent sections in a substantially fixed manner and at a substantially fixed distance relative to one another. Following degradation or breakage of the material in the overlap, the links allow at least some degree of movement of the stent sections. In this manner, the length of the stent may increase following deployment, and occupy a greater extent within the body lumen. 
     In one embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a connecting structure that connects the first and second stent sections, the connecting structure allowing the first and second stent sections to move relative to one another upon deployment of the stent within a body lumen. 
     In another embodiment, the present invention provides a stent comprising a first stent section, a second stent section, a first link extending from the first stent section, a second link extending from the second stent section, wherein the first and second links interlock and define an overlap region, and a material formed in the overlap region to hold the first and second stent sections in a substantially fixed relationship, wherein the material is separable upon deployment of the stent within a body lumen, thereby enabling the first and second stent sections to move relative to one another. 
     In a further embodiment, the present invention provides a stent comprising a first stent section, a second stent section, a first link that interlocks with a second link in the first stent section and a third link in the second stent sections, thereby connecting the first and second stent sections, wherein the first link defines a first overlap region with the second link and a second overlap region with the third link, and a material formed in the first and second overlap regions to hold the first and second stent sections in a substantially fixed relationship, wherein the material is separable upon deployment of the stent within a body lumen, thereby enabling the first and second stent sections to move relative to one another. 
     In an added embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a connecting member that connects the first and second stent sections, the connecting member holding the first and second stent sections in a substantially fixed relationship, wherein the connecting member relaxes the connection between the first and second stent sections following deployment of the stent within a body lumen, thereby enabling flexure of the stent. 
     In another embodiment, the present invention provides a stent comprising a first stent section including a first spring coil, a second stent section including a second spring coil, a first spring arm extending from the first stent section, a second spring arm extending from the second stent section, and a material that connects the first and second spring arms, the material being breakable, thereby at least partially disconnecting the first and second stent sections and allowing the first and second stent sections to move relative to one another. 
     In a further embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a housing that encloses at least portions of the first and second stent sections, wherein the housing is breakable upon deployment, thereby allowing the stent sections to move relative to one another following degradation of the housing. 
     In another embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a housing that encloses at least portions of the first and second stent sections, wherein the housing is degradable upon deployment, thereby allowing the stent sections to move relative to one another following degradation of the housing. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B are side views of a multi-section stent having a separable connection structure incorporating v-shaped grooves; 
     FIG. 1C is a perspective view of a multi-section stent as shown in FIG. 1A; 
     FIGS. 2A and 2B are side views of a multi-section stent having a separable connection structure incorporating square grooves; 
     FIGS. 3A and 3B are side views of a multi-section stent having a separable connection structure incorporating perforations; 
     FIGS. 4A and 4B are side views of a multi-section stent having a separable connection structure incorporating discrete breakable connecting members; 
     FIG. 4C is a perspective view of a multi-section stent as shown in FIG. 4A; 
     FIGS. 5A and 5B are side views of a multi-section stent having a separable connection structure incorporating discrete breakable connecting members; 
     FIGS. 6A,  6 B, and  6 C are side views of a multi-section stent having a separable connection structure incorporating interlocking links; 
     FIGS. 7A and 7B are side views of another multi-section stent having a separable connection structure incorporating interlocking links; 
     FIGS. 8A and 8B are side views of a multi-section stent having a spring coil structure with separable connecting members; 
     FIGS. 9A and 9B are perspective side views of a multi-section stent with connecting loops; 
     FIGS. 10A and 10C are side views of a multi-section stent with a degradable housing; and 
     FIG. 10B is an end view of the multi-section stent of FIG.  10 A. 
     Like reference numbers and designations in the various drawings indicate like elements. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1A and 1B are side views of a multi-section stent  10  having a separable connection structure that facilitates enhanced flexibility. FIG. 1C is a perspective view of multi-section stent  10 . In the example of FIGS. 1A-1C, multi-section stent  10  includes five stent sections  12 ,  14 ,  16 ,  18 ,  20 . Stent  10  may include a lesser or greater number of stent sections, however, depending on the application. For example, stent  10  may include as few as two stent sections in some applications. Each stent section  12 ,  14 ,  16 ,  18 ,  20  has a ring-like structure with an inner wall  22 , an outer wall  24 , and a central aperture  26 . Stent sections  12 ,  14 ,  16 ,  18 ,  20  are arranged coaxially and in series to form the longitudinal extent of stent  10 . Stent sections  12 ,  14 ,  16 ,  18 ,  20  define an inner channel  28 , indicated by dashed lines  30 ,  32  in FIG. 1A, that extends along the length of stent  10 . 
     Upon deployment, inner channel  28  is sized to accommodate flow within a body lumen. Outer wall  24  of each stent section  12 ,  14 ,  16 ,  18 ,  20  is sized, upon deployment, to engage the inner surface of the body lumen, and thereby resist further occlusion. In this manner, stent  10  is effective in restoring or maintaining the patency of a body lumen, such as ablood vessel. The dimensions of stent sections  12 ,  14 ,  16 ,  18 ,  20  may vary depending on the application. In many applications, the diameters of inner wall  22  and outer wall  24  will be the same for all stent sections  12 ,  14 ,  16 ,  18 ,  20 . Similarly, each of stent sections  12 ,  14 ,  16 ,  28 ,  20  may have the same axial length. For some applications, however, variation in the inner and outer diameters and lengths of individual stent sections  12 ,  14 ,  16 ,  18 ,  20  is conceivable. 
     Connecting members  34 ,  36 ,  38 ,  40  connect adjacent stent sections  12 ,  14 ,  16 ,  18 ,  20  to one another in a substantially fixed relationship. Connecting member  34 , for example, forms a connection between adjacent stent sections  12  and  14 . In the example shown in FIGS. 1A-1C, connecting members  34 ,  36 ,  38 ,  40  are not discrete components. Instead, connecting members  34 ,  36 ,  38 ,  40  are formed integrally with the body of stent  10 . Stent  10  can be formed as a continuous structure, e.g., by molding, casting, lamination, deposition, or other known manufacturing processes. Each connecting member  34 ,  36 ,  38 ,  40  can be formed by thinning, perforating, pre-stressing or otherwise weakening portions of stent  10  between adjacent stent sections  12 ,  14 ,  16 ,  18 ,  20 . 
     As shown in FIG. 1A, for example, connecting members  28 ,  30 ,  32 ,  34  may take the form of v-shaped grooves  42 ,  44 ,  46 ,  48  that are spaced axially along the length of stent  10  between adjacent stent sections  12 ,  14 ,  16 ,  18 , 20 . Each groove  42 , 44 , 46 , 48  extends circumferentially about stent  10 . The minimum diameter of each groove  42 ,  44 ,  46 ,  48  is sized larger than that of inner channel  22 , but significantly smaller than that of stent  10 . In this manner, grooves  42 ,  44 ,  46 ,  48  produce a thinned area that serves to weaken, and promote breakage of, stent  10  at selected positions. In particular, grooves  42 ,  44 ,  46 ,  48  preferably are designed to promote breakage of stent  10  in response to intra-luminal forces, either immediately following deployment or over an extended period of time. Upon breakage, stent sections  12 ,  14 ,  16 ,  18 ,  20  are separable from one another. 
     Stent sections  12 ,  14 ,  16 ,  18 ,  20  can be coated or impregnated with therapeutic materials such as heparin. The materials can be selected to dissolve upon deployment within the body lumen. For example, the materials can be incorporated in body-soluble sugars that dissolve within a blood vessel. Alternatively, the materials can be dissolved in response to introduction of a dissolving agent into the body. Collagen coatings, for to example, can be selected to dissolve upon ingestion or injection of a particular enzyme dosage. As a further alternative, temperature-sensitive materials can be selected for coating or impregnation in stent sections  12 ,  14 ,  16 ,  18 ,  20 . When heated to body temperature following deployment, the materials can dissolve to deliver desired therapeutic materials. Also, breakage could be further promoted by coating stent sections  12 ,  14 ,  16 ,  18 ,  20  with a material that swells upon absorption of fluid within the body lumen. Such a material could be selected to become more rigid upon absorption, thereby exerting a force against connecting members  34 ,  36 ,  38 ,  40  to induce breakage. 
     Stent  10  can be constructed from a variety of different materials. Examples include metals such as gold, silver, platinum, stainless steel, tantalum, titanium, shape-memory alloys such as nickel-titanium alloys referred to as Nitinol, as well as synthetic polymers and biological materials such as natural fibrin. Such materials can be selected or coated to provide radio-opacity, if desired. Nitinol may be particularly advantageous in light of its memory properties. With Nitinol, stent  10  can be initially formed with a given configuration, and then deployed in a substantially flexible state. Stent  10  can be processed to provide connecting members  34 ,  36 ,  38 ,  40 , which present weakened areas of the stent body. Upon deployment, the Nitinol can be heated, e.g., electrically or by exposure to body temperature, and thereby transformed to a more rigid state. In the process of transformation to a rigid state, the Nitinol exerts a force that promotes breakage of connecting members  34 ,  36 ,  38 ,  40 . 
     In some embodiments, stent  10  can be formed by processing a substantially continuous starting material to provide connecting members  34 ,  36 ,  38 ,  40 . A substantially continuous, material can be formed by molding or casting. Grooves  42 ,  44 ,  46 ,  48  can be formed in initial manufacture or by subsequent processing. If stent  10  is formed by molding or casting, for example, grooves  42 ,  44 ,  46 ,  48  can be made during stent formation. Alternatively, the molding or casting operation may merely provide a blank for further processing. In this case, grooves  42 ,  44 ,  46 ,  48  can be formed, for example, by mechanical scribing, laser etching, chemically etching, or mechanical milling or lathing the stent to form the groove. As a further option, grooves  42 ,  44 ,  46 ,  48  could be thermally stamped or embossed, particularly if stent  10  is formed from a polymeric material. To further promote breakage, a series of perforations could be formed along grooves  42 ,  44 ,  46 ,  48 . In any event, grooves  42 ,  44 ,  46 ,  48  should be formed at a depth sufficient to promote breakage over time, but retain enough thickness to keep stent  10  substantially intact during deployment. Thus, determination of the depth of grooves  42 ,  44 ,  46 ,  48  may require a trade-off between ease of breakage and structural integrity during deployment. 
     The depths of grooves  42 ,  44 ,  46 ,  48 , i.e., the degree of thinning of stent  10 , can be the same. Stent sections  12 ,  14 ,  16 ,  18 ,  20  may be subject to different stresses due to their relative positioning along the length of stent  10 , and the contour of the target site within the body lumen. As a result, some of connecting members  34 , 36 ,  38 , 40  may break more easily than others. Accordingly, for some applications, it may be desirable to form grooves  42 ,  44 ,  46 ,  48  with different depths to produce more uniform breakage characteristics despite different stresses existing at each connecting member  34 ,  36 ,  38 ,  40 . Alternatively, other methods, such as perforation, pre-stressing, etching, scribing, milling, or lathing, may be used to weaken individual connecting members  34 ,  36 ,  38 ,  40  in a differential manner. Uniform breakage may be desirable for some applications, but does not imply that connecting members  34 ,  36 , 38 ,  40  need to break at precisely the same time. 
     Upon breakage of stent  10  along grooves  42 ,  44 ,  46 ,  48 , as shown in FIG. 1B, the adjacent stent sections  12 ,  14 ,  16 ,  18 ,  20  are disconnected and separate from one another. The disconnected stent sections  12 ,  14 ,  16 ,  18 ,  20  remain positioned proximate one another within the body lumen, but are able to move independently. Consequently, stent maintains the patency of the body lumen while affording greater flexibility. In particular, depending on the contour and conditions of the target site, the disconnected stent sections  12 ,  14 ,  16 ,  18 ,  20  may be able to pivot, tilt, rotate, and move longitudinally within the body lumen relative to one another. Instead of presenting a rigid tube, stent  10  is better able to conform to the shape of the lumen. 
     Stent  10  ordinarily will be sized or biased such that the inner wall of the body lumen exerts significant force radially inward against outer wall  24 . This radial force will tend to restrain stent sections  12 ,  14 ,  16 ,  18 ,  20  against excessive longitudinal movement. Given the radial force, outer wall  24  of each stent section  12 ,  14 ,  16 ,  18 ,  20  should have a surface area sufficient to prevent axial “tumbling” of the stent section, i.e, a collapse such that the circular cross-section of stent section moves away from a perpendicular position relative to the body lumen wall. If a stent section  12 ,  14 ,  16 ,  18 ,  20  is extremely short in length, relative to the longitudinal extent of the body lumen, tumbling can be a problem. With sufficient length, interaction between outer wall  24  and the inner wall of the body lumen will tend to anchor stent sections  12 ,  14 ,  16 ,  18 ,  20  against excessive movement. Eventually, stent sections  12 ,  14 ,  16 ,  18 ,  20  will settle into a generally stationary position and heal into the wall of the body lumen. 
     A separable connecting structure, as described herein, can be applied to a variety of different stent structures. Stent  10  can be fabricated from an elastomeric material or spring biased, for example, to allow compression for deployment. Instead of having a solid, or substantially continuous body, stent  10  can be fabricated by wrapping a sinusoidally shaped wire in a series of turns about a form to provide a tube-like shape. Adjacent wire turns can be partially cut or otherwise weakened to promote breakage at connecting members  34 ,  36 ,  38 ,  40 . Upon release from a delivery catheter, sleeve, or other restraint, stent  10  is able to voluntarily expand radially outward to fill the body lumen. Stents of this type are often referred to as self-expandable. 
     As an alternative, stent  10  can have an assisted expansion structure. Expansion can be assisted, for example, by inflating a balloon disposed within the stent. Self-expandable and balloon-expandable stent structures are well known in the art. Optionally, the breakable connecting structure can be made to break upon expansion of the stent, thereby disconnecting the stent sections. As a further option, stent  10  may have a structure that enables the delivery of a variety of therapeutic substances to the body lumen. For example, stent  10  can be constructed with a mesh or cellular material loaded with one or more therapeutic substances that are released over time. 
     FIGS. 2A and 2B are side views of a multi-section stent  50  having a breakable connection structure incorporating square grooves  52 ,  56 ,  58 ,  60 . Stent  50  substantially conforms to stent  10  of FIGS. 1A-1C, and includes five stent sections  12 ,  14 ,  16 ,  18 ,  20 . Instead of a v-shaped groove for each connecting member  34 ,  36 ,  38 ,  40 , however, stent  50  makes use of square grooves  52 ,  54   56 ,  58 . Specifically, each groove  52 ,  54 ,  56 ,  58  has a substantially square or rectangular cross-section. 
     As shown in FIG. 2A, each groove  52 ,  54 ,  56 ,  58  extends circumferentially about stent  50  at a position separating two adjacent stent sections  12 ,  14 ,  16 ,  18 ,  20 . Each groove  52 ,  54 ,  56 ,  58  defines a thinned portion of stent  50 , weakening the stent to promote breakage. As with stent  10 , grooves  52 ,  54 ,  56 ,  58  of stent  50  can be supplemented by perforation, scribing, etching, milling, lathing or other processes to further weaken the respective connecting member  34 ,  36 ,  38 ,  40 . Following breakage of connecting members  34 ,  36 ,  38 ,  40 , as shown in FIG. 2B, stent sections  12 ,  14 ,  16 ,  18 ,  20  are free to move relative to one another within the body lumen. 
     FIGS. 3A and 3B are side views of a multi-section stent  60  having a separable connection structure incorporating perforated connecting members  34 ,  36 ,  38 ,  40 . In the example of FIGS. 3A and 3B, stent  60  includes four stent sections  12 ,  14 ,  16 ,  18 . Each connecting member  34 ,  36 ,  38  is integrally formed with the body of stent  60 , but incorporate a series of perforations  62 ,  64 ,  66 , respectively, that extend about the stent. Each series of perforations  62 ,  64 ,  66  defines the junction between adjacent stent sections  12 ,  14 ,  16 ,  18 . Perforations  62 ,  64 ,  66  weaken stent  60  in the vicinity of the junction, promoting breakage under intraluminal forces. 
     Perforations  62 ,  64 ,  66  can be formed following fabrication of stent  60  by a variety of processes and mechanisms such as, e.g., mechanical needles or punches, laser ablation, or chemical etching. Alternatively, stent  60  could be molded or laminated to yield perforations  62 ,  64 ,  66 . In some embodiments, it is conceivable that perforations  62 ,  64 ,  66  need not extend entirely through the wall of stent  60 . Instead, partial penetration of the wall at a series of positions may be sufficient to weaken connecting members  34 ,  36 ,  38  for breakage. 
     FIGS. 4A and 4B are side views of a multi-section stent  68  having a separable connection structure incorporating sets of discrete breakable connecting members  70 ,  72 ,  74 ,  76 . FIG. 4C is a perspective view of multi-section stent  68 . As best shown in FIG. 4C, connecting members  70 ,  72 ,  74 ,  76  may form rod-like elements distributed about the periphery of respective stent sections  12 ,  14 ,  16 ,  18 ,  20  on a side facing adjacent stent sections. Connecting members  70 , 72 , 74 , 76  bridge adjacent stent sections  12 ,  14 ,  16 ,  18  to connect the stent sections and hold stent  68  intact for deployment and positioning within the body lumen. 
     Each connecting member  70 ,  72 ,  74 , 76  is manufactured to break under intraluminal forces, however, following deployment of stent  68  within the body lumen. For example, each connecting member  70 ,  72 ,  74 ,  76  may include a weakened portion  78  that promotes breakage. As in other embodiments, weakened portion  78  can be formed by thinning, perforating, or prestressing connecting members  70 ,  72 ,  74 ,  76 . Alternatively, stent  68  can be molded to form connecting members  70 ,  72 ,  74 ,  76 , along with weakened portions  78 . Following breakage of connecting members  70 ,  72 ,  74 ,  76 , stent sections  12 ,  14 ,  16 ,  18 ,  20  are able to move independently, as indicated in FIG.  4 B. 
     Use of rod-like elements as connecting members  70 ,  72 ,  74 ,  76  can provide the added benefit of stability to stent sections  12 ,  14 ,  16 ,  18 . In particular, the rod-like elements extend outward from stent sections  12 ,  14 ,  16 ,  18  and can engage the inner wall of the body lumen to resist axial tumbling of the respective stent section. For added stability, connecting members  70 ,  72 ,  74 ,  76  may take the form of tab-like elements that, relative to rod-like elements, exhibit greater lateral surface area for contact with the lumen wall. In either case, the resulting connecting members  70 ,  72 ,  74 ,  76  provide extensions that counteract tumbling forces. 
     FIGS. 5A and 5B are side views of a multi-section stent  78  having a separable connection structure incorporating sets of discrete degradable or physically breakable connecting members  80 ,  82 ,  84 ,  86 . As in stent  68 , connecting members  80 ,  82 ,  84 ,  86  may take the form of rod-like, or tab-like elements that bridge a gap between adjacent stent sections  12 ,  14 ,  16 ,  18 ,  20 . In the example of FIGS. 5A and 5B, connecting members  80 ,  82 ,  84 ,  86  take on a tab-like configuration. Connecting members  80 ,  82 ,  84 ,  86  thereby connect stent sections  12 ,  14 ,  16 ,  18 ,  20  and hold stent  78  intact for deployment and positioning. Each connecting member  80 ,  82 ,  84 ,  86  forms two halves, however, that can be held together with a material  90  that can be made from biodegradable or physically breakable material. 
     If made with a biodegradable material, material  90  dissolves or otherwise degrades upon interaction with fluids within the body lumen to a point at which connecting members  80 ,  82 ,  84 ,  86  break apart. Alternatively, if made with a physically breakable material, intraluminal forces cause connecting members  80 ,  82 ,  84 ,  86  to break apart at material  90 . In this case, the biocompatible material forming material  90  could take the form of a brittle material that is not necessarily degradable, but which readily breaks under intraluminal forces or upon expansion of stent  68 . Degradation or physical breakage yields discrete stent sections  12 ,  14 ,  16 ,  18 , which then are independently movable within the body lumen. In the example of FIGS. 5A and 5B, stent sections  12 ,  14 ,  16 ,  18 ,  20  can be fabricated as discrete components, e.g., by molding, machining, lamination, or other techniques, and bonded together using material  90 . In this case, discrete stent sections  12 ,  14 ,  16 ,  18 ,  20  are connected together to form stent  78 . Alternatively, stent  78  could be molded as an integral component, with material  90  being insert molded to connect adjacent connecting members  80 ,  82 ,  84 ,  86 . Examples of degradable materials suitable for use as material  90  include fibrin, collagen, polymers, polyurethane, sugars, polyunhydrides, and polyethyloxides. Degradable materials could be mixed with therapeutic substances, if desired, for release into the body lumen upon degradation of material  90 . Examples of breakable, biocompatible materials that could be used as material  90  include metals such as gold, silver, platinum, stainless steel, titanium, tantalum, and Nitinol, as well as any of the biodegradable materials mentioned above, i.e., fibrin, collagen, polymers, polyurethane, sugars, polyunhydrides, and polyethyloxides. 
     FIGS. 6A,  6 B, and  6 C are side views of a multi-section stent  92  having a breakable connection structure incorporating pairs of interlocking links  94 ,  96  that connect adjacent stent sections  12 ,  14 ,  16 ,  18 . In the example of FIGS. 6A,  6 B, and  6 C, each of stent sections  12 ,  14 ,  16 ,  18  takes the form of an interlocking matrix that is woven in a manner similar to a chain link fence. Stent sections  12 ,  14 ,  16 ,  18  in this embodiment can be fabricated from the same materials used for other embodiments. Again, examples of biocompatible materials that could be used include metals such as gold, silver, platinum, stainless steel, titanium, tantalum, and Nitinol. The matrix can be formed from an array of links substantially identical to links  94 ,  96 . The links in each of stent sections  12 ,  14 , 16 ,  18  define a ring-like structure. Each of links  94 ,  96  interlocks with a link in one of stent sections  12 ,  14 ,  16 ,  18  at one end, and interlocks with one another at the other end, thereby holding the stent sections together to form stent  92 . For example, link  94  extends from a first stent section  12 , whereas link  96  extends from a second stent section  14 . Link pairs  94 ,  96  can be distributed about the circumferences of adjacent stent sections  12 ,  14 ,  16 ,  18 , holding them at multiple points. 
     As shown in FIG. 6A, links  94 ,  96  can be structured to interlock with one another and form an overlap region  100 . Similarly, links  94 ,  96  may form overlap regions  102 ,  104  with the stent sections  12 ,  14 ,  16 ,  18  with which they interlock. A degradable or physically breakable material  98  can be formed in each of overlap regions  100 ,  102 ,  104  to fortify the interlock, and thereby maintain stent sections  12 ,  14 ,  16 ,  18  in a substantially fixed manner. Thus, the degradable material helps keep multi-section stent  92  intact for deployment and positioning. Also, the degradable material  98  prevents longitudinal movement of stent sections  12 ,  14 ,  16 ,  18  relative to one another, maintaining the stent sections at a predetermined spacing. Following deployment, however, the material degrades, relaxing the interlock between links  94 ,  96 , as well as the interlocks between the links and respective stent sections  12 ,  14 ,  16 ,  18 . 
     Upon degradation of the material in overlap regions  100 ,  102 ,  104 , stent sections  12 ,  14 ,  16 ,  18  remain connected to one another, but are able to more freely move about the interconnection points. As shown in FIG. 6C, for example, stent sections  12 ,  14 ,  16 ,  18  are able to tilt relative to one another. Notably, in the absence of overlap regions  100 ,  102 ,  104 , stent sections  12 ,  14 ,  16 ,  18  are able to move longitudinally away from one another, at least to the extent permitted by the remaining interlock points. Consequently, as indicated in both FIG.  6 B and FIG. 6C, stent  92  is actually capable of expanding its length following deployment. At the same time, however, the length of stent  92  is constrained by the remaining interconnection of links  92 ,  94 . 
     FIGS. 7A and 7B are side views of a multi-section stent  106  having a breakable connection structure incorporating alternative interlocking links  108 . Stent  106  conforms substantially to stent  92  of FIGS. 6A-6C. However, stent  106  makes use of a single link  108 , instead of link pairs  92 ,  94 , to connect adjacent stent sections  12 ,  14 ,  16 ,  18 . Link  108  interlocks with adjacent stent sections  12 ,  14 ,  16 ,  18  at opposite ends, forming overlap regions  110 ,  112  that can be filled with a breakable or degradable material  113  to fortify the interconnection. As shown in FIG. 7B, following degradation of the material, stent sections  12 ,  14 ,  16 ,  18  are more freely movable. Moreover, upon elimination of overlap regions  110 ,  112 , the length of stent  106  can be expanded. 
     FIGS. 8A and 8B are side views of a multi-section stent  114  having a spring structure with breakable or degradable spring arms  116 . Each stent section  12 ,  14 ,  16  takes the form of a self-expandable spring coil having multiple turns  118 . Spring arms  120 ,  122  extend between adjacent stent sections  12 ,  14 ,  16  to form connecting members. A biodegradable or breakable material  124  joins spring arms  120 ,  122  to hold stent  114  together. Alternatively, spring arms  120 ,  122  may form a continuous member that is weakened, e.g., by thinning, perforation, etc., to promote breakage under intraluminal forces. Following breakage, as shown in FIG. 8B, stent sections  12 ,  14 ,  16  are detached and freely movable relative to one another. 
     FIGS. 9A and 9B are perspective side views of a multi-section stent  124  having connecting loops  126  that permit movement and flexibility of stent sections  128 ,  130 ,  132  relative to one another. As shown in FIG. 9A, each section  128 ,  130 ,  132  of stent  124  may take the form of a ring. Adjacent rings  128 ,  130 ,  132  are held together by connecting loops  126 . Loops  126  can be made from a rigid material and sized to allow play between rings  128 ,  130 ,  132 . In other words, loops  126  can be sized to permit rings  128 ,  130 ,  132  to move back and forth in a longitudinal or tilting direction relative to one another. Loops  126  preferably are sized small enough to limit axial tumbling of rings  128 ,  130 ,  132  within the body lumen. Following deployment, rings  128 ,  130 ,  132  are movable relative to one another. As a further alternative, loops  126  can be fabricated from an elastomeric material that allows rings  128 ,  130 ,  132 . In either case, stent  124  provides flexibility, allowing rings  128 ,  130 ,  132  to adapt to the body lumen in which the stent is positioned. 
     FIGS. 10A and 10C are side views of a multi-section stent  134  having a connecting structure in the form of a degradable housing  136  that binds stent sections  138 ,  140 ,  142 ,  144  together. FIG. 10B is an end view of stent  134 . Upon deployment, housing  136  is degradable, thereby releasing sections  138 ,  140 ,  142 ,  144 , and allowing them to move relative to one another. As shown in FIG. 10A, housing  136  may take the form of a continuous cylinder that is molded or formed from a sheet. Alternatively, housing  136  may be cage- or net-like, having a number of different threads that cross one another. In either case, housing  136  can be formed from any of the biodegradable materials described herein. Following degradation of housing  136 , stent sections  138 ,  140 ,  142 ,  144  are free to move and adapt to the body lumen in which stent  134  is positioned. 
     A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.