Abstract:
An implant with a surface structure on at least a portion of a surface of the implant, wherein the surface structure is selected to facilitate, improve and enhance ingrowth characteristics of the implant. A method of providing an implant with a selected surface structure is encompassed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application is a continuation of International Application No. PCT/CH02/00461, filed on Aug. 23, 2002, which claims priority to German Application N. 101 42 637.2, filed on Aug. 31, 2001, the contents of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND  
       [0002]     The present invention relates to medical technology, including implantable devices. More particularly, it relates to an implant with a surface structure, in particular to a transcutaneous implant with an orientated structure on a surface thereof, which improves the ingrowth characteristics of the implant, and to a method for producing such an implant.  
         [0003]     Implants are known which are inserted completely or partially into a body, wherein—for example in the case of an inserted port body—a region or portion of the port body protrudes out from the surface of the skin. This often results in problems with the surrounding skin growing onto the port body. Inflammations often form in the border region between the surrounding skin and the port body, which spread along the inserted port body into a patient&#39;s body. This is at least unpleasant for a patient, and leads to the port body being badly fitted and to a high risk of infection for the patient.  
         [0004]     A device for promoting wound healing is known from U.S. Pat. No. 5,833,641, which consists of a biologically tolerable material and is bio-degradable. This device is used on a wound for wound healing and comprises a surface structure which serves to orientate a desired cellular growth and can be bio-degraded during or after the application, i.e. absorbed by the patient.  
       BRIEF SUMMARY  
       [0005]     It is an object of the present invention to provide an implant which, once inserted, is more tolerable for a patient. Furthermore, it is an object of the present invention to provide a method for producing said implant.  
         [0006]     In one embodiment, the present invention comprises an implant with a surface structure on at least a portion of a surface of the implant, wherein the surface structure is selected to facilitate, improve and enhance ingrowth characteristics of the implant. A method of providing an implant with a selected surface structure is encompassed.  
         [0007]     One embodiment of an implant in accordance with the present invention is a transcutaneous implant, i.e., an implant which is not completely inserted into a body, such that after the implant has been inserted or implanted, at least a part of it protrudes out from the surface of the skin. An example of such an implant involves a port body which serves to introduce a substance into a subcutaneous tissue.  
         [0008]     In accordance with one embodiment of the present invention, a surface structure is provided on at least one surface region of an implant, said surface structure improving the ingrowth characteristics of the implant. The surface structure is orientated such that the growth of cellular tissue around the implant is promoted and/or is assisted in one or more directions, including a preferred direction or preferred directions. The surrounding tissue can, for example, be skin cells, muscle cells or blood vessels. If skin cells are orientated in a uniform direction by such a surface structure of a transcutaneous implant, then the cellular arrangement arising—thus promoted by the surface structure—leads to an accelerated healing of the wound and an improved connection between the surrounding tissue cells and the implant wall, in particular in the structured region of the surface of the implant. Such an improved connection between the surrounding tissue cells and the implant also leads to improved protection from bacteria and undesirable matter, such that the risk of infection and inflammation when and after the implant is inserted is reduced. Using a suitable surface structure, the surface of the implant can be more densely populated by the surrounding tissue, thus improving cell adhesion to the implant wall.  
         [0009]     In some embodiments, an implant in accordance with the present invention is preferably produced at least partially from a suitable durable, non-absorbable material such as metal, plastic or a combination thereof, such that the implant is not degraded after it has been inserted.  
         [0010]     Advantageously, one embodiment of an implant in accordance with the present invention exhibits a suitable surface structure in the region where it penetrates the skin, wherein the surface structure particularly preferably runs roughly parallel to the surface of the skin when and after the implant is inserted.  
         [0011]     Providing a surface structure which promotes the growth of cellular structures, in particular blood vessels, parallel to the available tissue, i.e., for example, parallel to the surface of the skin, leads to the blood vessels accumulating mainly parallel to the surface of the skin around the implant and away from the implant, and substantially not reaching deep along the implant wall. Such an arrangement of the blood vessels around the implant leads to better blood circulation in the surrounding tissue and is furthermore advantageous since infections which may occur on the surface of the skin cannot easily spread along the implant wall to deeper regions. Infections can therefore be more effectively controlled by the body&#39;s own defences and may be recognized earlier by the patient.  
         [0012]     In some embodiments, including preferred embodiments, the structure on the surface of the implant is advantageously 1 to 10 mm wide, particularly preferably 4 to 5 mm wide, such that when the implant is inserted, surrounding tissue along this width of the surface structure can be orientated to a depth of 1 to 10 mm, preferably 4 to 5 mm, and can grow orientated onto the implant.  
         [0013]     In some embodiments, the surface structure is advantageously arranged encircling at least a partial region of the implant, embodied for example—if the implant has a circular or oval cross-section—in the region where it passes through the surface of the skin, as a groove structure encircling the implant. In some embodiments, said groove structure preferably exhibits a uniform orientation, i.e., the individual grooves are generally parallel to each other.  
         [0014]     In some preferred embodiments, the surface structure is particularly preferably embodied as a groove structure, for example as an encircling, spiral or helical groove or plurality of grooves. However, in some embodiments, the surface structure can be provided only on particular regions of the implant, other surface regions of the implant not comprising a surface structure, such that, for example, only individual grooves or groove structure sections are provided on the surface of the implant and are interrupted by a smooth surface of the implant. These embodiments are particularly useful if, for example, a desired orientation of cellular growth is only desired in or adjacent to a selected region of the surface of the implant.  
         [0015]     In some embodiments, the depth of the grooves is preferably in the range of 0.1 to 10 times—particularly preferably, in the range of 0.3 to 5 times—the average width of the type of cell which is to grow onto or into the groove, wherein the average width of the type of cell is understood as the width when the cell is placed onto a flat surface.  
         [0016]     In some embodiments, the depth of one or all of the grooves is advantageously in the range of 1 to 10 μm, preferably in the range of 3 to 4 μm, and the width of a groove is advantageously in the range of 1 to 10 μm, particularly preferably in the range of 4 to 5 μm.  
         [0017]     In some embodiments, the groove distance, i.e., the distance from the centre of a groove to the centre of another groove, is advantageously in the range of 2 to 20 μm and is preferably 10 μm.  
         [0018]     In some embodiments, the ratio of the width of the groove to the depth of the groove is advantageously in the range of 0.5 to 2, preferably substantially 1:1.  
         [0019]     In some embodiments of the present invention, preferably at least two, more preferably three to ten or more, regions or areas on the surface of the implant are provided with a different surface structure, such that, for example, a first surface structure is provided in the region near the surface of the skin after the implant is inserted, in order to enable skin cells to grow, and one or more other surface structures are provided beneath this first surface structure, to promote the growth of subcutaneous cellular structures such as, for example, blood vessels or the like.  
         [0020]     Advantageously, in some embodiments, a lower holding structure is provided on the implant and is inserted into the tissue. In one embodiment, this lower holding structure is a ring encircling the underside of the implant and protruding from the implant, in order to help hold the inserted implant. Advantageously, in some embodiments, passages or holes can be provided at one or more points on the encircling ring, through which tissue can grow in order to help better fit the implant. A recess, for example a groove, can advantageously be provided in the attachment region of the encircling ring, and surrounding tissue can grow into said recess, such that the fit of the implant is further improved.  
         [0021]     In some embodiments, the implant is preferably a transcutaneous implant, such as a port body, and comprises a suitable connecting structure, such as a thread or other suitable holding elements such as recesses with protrusions, in the upper region, the region which protrudes out of the tissue when the implant is inserted. In some embodiments a connecting element can be attached to said connecting structure in order to be able to introduce a substance from an external source into the tissue through the port body, wherein the port body can for example have an opening on its underside through which a substance introduced from the upper side enters the tissue.  
         [0022]     In accordance with another aspect of the present invention, a method for producing an implant as described above is provided, wherein a surface structure which improves the ingrowth characteristics of the implant is produced on at least a partial region or area of the surface of the implant.  
         [0023]     In one embodiment, the selected surface structure can, for example, be achieved by mechanically producing a groove structure on the surface, wherein for example a spiral groove is produced directly on the surface of the implant, such that the groove leads spirally around, for example, a cylindrical implant wall. The spiral groove can be produced in a turning method process using a specially ground steel shape. It is advantageous, once the groove has been produced, to polish the implant along the groove or grooves produced, such that the surface is substantially smooth. This rounds but nonetheless maintains the grooves. The implant can then advantageously be anodised or eloxed, wherein an oxide layer is formed which also extends over the structured region of the implant.  
         [0024]     It is equally possible to use an etching method to produce a desired surface structure, for example by means of an applied etching template. In this way, surface regions which are not to be etched are protected by an acid-resistant layer. Using an etching method, a multitude of different surface structures can be produced in one process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  depicts one embodiment of an implant in accordance with the present invention, with an enlarged partial region of the surface;  
         [0026]      FIG. 2  depicts one embodiment a port body inserted in a tissue, the port body having a surface structure in accordance with the present invention; and  
         [0027]      FIG. 3  is an enlargement of a partial region of the port body shown in  FIG. 2 .  
     
    
     DETAILED DESCRIPTION  
       [0028]      FIG. 1  shows an implant  1  which on a region of the implant wall  4  comprises a structured surface region  2  in the form of encircling grooves. If the implant  1  is inserted in the tissue such that the grooves  2  are in the region of the surface of the skin and are substantially parallel to the surface of the skin, then the encircling grooves promote the growth of skin cells in a direction along the grooves and thus help the tissue to grow in better and the implant to be held more securely.  
         [0029]      FIG. 2  shows a port body  1  inserted into a tissue, with an encircling surface structure  2  in the form of an encircling spiral groove. As can be seen in particular from  FIG. 3 , tissue cells  3 —such as for example skin and muscle cells and also blood vessels  6 —accumulate along the orientated groove structure  2 , which enables the tissue  3  to densely populate the surface  4  of the port body, parallel to the surface of the skin. Such a dense tissue cell population leads to an improved connection, i.e., to the tissue  3  growing into the port body  1  better, which enables the port body  1  to be more securely and firmly held. The cellular structure, thus orientated by the encircling groove structure  2 , also stimulates the blood vessels  6  to orientate themselves parallel to the available tissue  3 , such that the blood vessels  6  predominantly run mainly parallel to the surface  5  of the skin, around the port body  1 . This promotes the blood circulation in the tissue region surrounding the port body  1 , and largely prevents infection from spreading deep into the tissue.  
         [0030]     Beneath the structured surface  2  of the port body  1 , an implant wall  4  is formed which is substantially smooth on the surface, wherein surrounding tissue simply grows onto or lies on said implant wall  4 , as in implants known from the prior art. A protruding ring  7  which encircles the underside of the port body  1  ensures that the inserted implant  1  is held better in the tissue  3 . The ring  7  is interrupted by a number of holes  8  through which tissue can grow in order to further improve how the port body  1  is held or anchored in the tissue  3 . On the attachment region of the ring  7  on the port body  1 , a groove is provided which the tissue  3  can grow into.  
         [0031]     The portion or region of the port body  1  protruding out from the tissue on the surface  5  of the skin comprises a connecting structure (not shown), to which a connecting element  10  can be attached, in order to introduce a substance from an external storage container through the implant body  1  into the tissue  3 . The port body can comprise an opening (not shown) on its underside through which the substance is dispensed from the port body  1  into the surrounding tissue.  
         [0032]     As used herein, the phrase “surface structure” is intended to encompass, without limitation, suitable surface characteristics, textures, constructions, patterns, knurling, degree of roughness or smoothness, and the like. Suitable surface structure or structures in desired areas or regions of the surface of an implant or implantable device may be provided or produced by using any suitable method, for example, by casting, molding, cutting, abrading, laminating, coating, etching and the like. Suitable surface structure or structures may be formed integrally with an implant, eroded into the implant, and/or added, attached or connected thereto.  
         [0033]     In the foregoing description, embodiments of the present invention, including preferred embodiments, have been presented for the purpose of illustration and description. The embodiments were chosen and described to provide the best illustration of the principals of the invention and its practical application, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth they are fairly, legally, and equitably entitled.