The invention relates to an element for con¬ trolled growth of tissue into surgically intervened regions, e.g. for implant passageways, such an el¬ ement being used to fix a prosthesis in the body or forming such a prosthetis itself.

When an element is to be incorporated into a tissue or is to be implanted in such a way that it must pass through several tissues, i.a. in case of passage through the skin or through a mucous mem¬ brane, it is required that the element should be biocompatible, i.e. it must be accepted by the tis¬ sue, and the problem arises how to achieve a reli¬ able retention of the element in the surrounding tissue to avoid a purely mechanical dislocation of the element. Unsatisfactory biocompatibility as well as insufficient retention leads to tissue irrita¬ tion, possibly followed by tissue rupture at the el¬ ement. This means formation of reactive zones of connective tissue with a more or less pronounced streak of inflammation leading to the element no longer being harmoniously incorporated in the tissue region; the element starts to wander and loses its function. Furthermore, tissue irritation at implant passageways leads to downgrowth of epithelium around the element and, as a consequence thereof, finally to rejection.

In order to solve these problems, the element according to the invention has obtained the charac¬ teristics of claim 1.

For explanation of the invention in more detail reference is made to the accompanying drawings, wherein

Fig 1 shows a cylindrical implant element hav¬ ing peripheral grooves and a central passage.

Fig 2 illustrates an outer socket having through holes of the same levels as the grooves of the cylinder of fig 1,

Fig 3 shows the cylinder and the socket pressed

10 together to form a unit providing a tunnel and/or canal network within the periphery of the implant element, and

Fig 4 is an illustration similar to fig 3 but with a diametrically wider flange on the upper end _l5 portion of the cylinder.

In the illustrated embodiment, the element 10 is tubular and can comprise e.g. an implanted con¬ duit for peritoneal dialysis (abdominal dialysis) . The conduit can be rigid or flexible. It forms a

20 number of tunnel and/or canal networks 11, which are separated from the passage 12 through the element by a solid wall 13 and from the exterior surface of the element by an ingrowth zone 14, the openings of which are indicated at 15 and form circular aper¬

25 tures. The connective tissue, which is indicated at 16, grows into the tunnel and/or canal network 11, matures and attains a structural organization re¬ sulting in the epithelium 17 being prevented from growing down along the surface of the element and infiltrating the layer of connective tissue next to

30 the element to enclose eventually the element 10, which leads to rejection of the element. The tissue ingrowth into the tunnel and/or canal network 11 should be such that the connective tissue inside the

3_5_ tunnel and/or canal network 11 becomes complete and

attains full maturity, i.e. the tunnel and/or canal network 11 should be sufficiently large to allow the connective tissue cells as well as the blood-vessels necessary for the maintenance of the connective tis¬ sue to grow thereinto, thus creating conditions for the generation of connective tissue fibres and ma¬ trix by the connective tissue cells and for the maturation of the components of the connective tis¬ sue and normal renewal thereof, requiring that no part of the tunnel and/or canal network 11 should have a diameter less than 30 ^~ m.

According to the invention, the surfaces of the element 10, which are exposed to the surrounding tissue, consist of a biocompatible material, tita¬ nium being an excellent material of this kind. The element 10 as a whole can consist of titanium, but preferably the element 10 is coated on said sur¬ faces, i.e. the exterior surface of the element in¬ side the tunnel and/or canal network 11, with tita¬ nium by a thin layer thereof being deposited on a substrate by vacuum evaporation. This substrate can be rigid or flexible and can consist of e.g.silicone rubber, polyester or polytetrafluoro ethylene. In the illustrated embodiment, the openings 15 of the tunnel and/or canal network have sharp edges, but the edges can be formed in another way, e.g. as beveled edges on the outside of the element or inside the tunnel and/or canal network 11, or they can be rounded.

When an implant passageway is implanted in the body tissue in the way which has been described, the connective tissue has the opportunity to mature ad¬ jacent to the surface of the element 10 and inside the tunnel and/or canal network 11 in order to achieve a reliable and permanent retention of the

element by preventing the epithelium from growing down around the element at the implant passageway.

The portion of the surface of the element 10, located immediately above the uppermost tunnel and/or canal opening 11 provided in the wall of the element, which is exposed to the epithelium layer 17, therefore should be suitably profiled, e.g. widened as in fig 4. This arrangement further pre¬ vents downgrowth of epithelium along the surface of the element during the time required for the granu¬ lation tissue of the wound region to mature into a firm, structured connective tissue.

The tunnel and/or canal network 11 can be con¬ structed in several different ways, e.g. as a labyr- inth system.