CA1068052A

CA1068052A - Prosthetic devices and implants with porous systems in a soft tissue environment

Info

Publication number: CA1068052A
Application number: CA268,132A
Authority: CA
Inventors: David C. Macgregor
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-12-22
Filing date: 1976-12-17
Publication date: 1979-12-18

Abstract

PROSTHETIC DEVICES AND IMPLANTS WITH POROUS
SYSTEMS IN A SOFT TISSUE ENVIRONMENT
ABSTRACT OF THE DISCLOSURE

Prosthetic devices and implants for incorporation into various soft tissue environments comprise a porous surface and a network of interconnected interstitial pores below the surface in fluid flow communication with the surface pores. Soft tissue grows into the pores to incorporate the prosthetic device or implant permanently into the body.

Description

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, This invention relates to prosthetic devices and implants placed in a soft tissue environment.

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Many prosthetic devices and implants are known and used for replacement of diseased or damaged body parts and to assist in the proper functioning of body organs. Many such devices are used in soft tissue environments and are difficult to secure permanently in such environments.
Usually the devices have a smooth surface which does not allow the secure bonding of the device to the surrounding body tissue, which may give rise to infection in the area between the smooth surface and the body tissue, or to dis-:. . , lodgment from its desired body location.
In U.S. Patent No. 3,855,638, there is describedan implant and prosthetic device exclusively designed for bone replacement in which overall strength re~uirements of the device are a major consideration. The implant or prosthetic device of this prior art is constructed of ;
metal and consists of a solid metal substrateand a porous sintered metal coating in which the average interstitial pore size i9 greater than 50 microns to ensure bone tissue ingrowth for incorporation of the device into the bone.
Additionally, various porosity and thickness re~uirements ~ are to be adhered to if the necessary strength properties `
; are to be provided.
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,,, In accordance with the present invention, there is provided a prosthetic device or implant suitable for permanent incorporation into a soft tissue environment of

- 2 '' ~ ~: ' ~068052 a human body, constructed of a material substantially inert to hody fluids having a surface adapted to engage the soft tissue. The surface is porous and is in fluid flow communi-cation with a network of interconnected pores in a sub-surface, so that the soft tissue may grow through the surface pores and into the sub-surface network when located in the soft tissue environment to incorporate the prosthetic device or implant into the body.

In soft tissue environments, the strength of the bond between the surrounding tissue and the prosthetic device or implant is a less important factor than in the .. , ~
osseous environment where the bond is subjected to greater ~-stress. Therefore, the parameters considered essential for osseous tissue ingrowth and the provision of a satisfactory device do not necessarily apply in the so~t tissue environ-ment.
The parameters of the porous surface for use in the prosthetic devices and implants of this invention, therefore, - 20 may vary widely and those chosen depend somewhat on the particular end use of the pro~thetic device or implant.
The interstitial surface pore size may vary widely, generally from about 1 to about 1,000 microns with pore sizes of about 20 to about 300 microns being preferred.
Larger pore sizes generally are preferred to allow for ,., vascular ingrowth.
The sub-surface network generally is provided with the s~me interstitial pore size as the sur~ace, although may be varied, if desired. The porosity of the network also may vary widely, generally from about 8% upwards.
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Pre~erably, a poros:;ty in the ran~e of about 10 to about 50% is preferred.
The prosthetic device or implant of the invention may be wholly porous or in the form of a composite with a porous coating overlying a dense, coherent substrate, the form depending upon the intended end use of the product.
The composite structure is the most useful form of the invention.
However, several important products may be provided using the wholly porous embodiment of the invention.
Where the invention takes the form of a composite article consisting of a porous coating on a coherent sub-strate, the thickness of the coating may vary widely, generally from about 1 to about 10,000 microns. The minimum thickness is that necessary to establish an interconnected pore network and varies, depending on the material of con- i~
; struction and the interstitial pore size of the particular coating. Usually, the coating has a thickness of about 20 ; ;~
to about 1,000 microns, preferably about 20 to about 150 microns.
The prosthetic devices and implants of this invention may be formed of a variety of materials of construction, such as, metal, including alloys, flexible or rigid plastics .
and other non-metallic systems, such as ceramics and carbon materials. The materials utilized must, however, be inert to body fluids to prevent degradation or corrosion once incorporated into the body.
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Mixed systems involving 2,3,4 or more differing materials may be used, for example, a metal substrate with ~ non-metallic porous coating, or a metal substrate with various non-~etallic porous coatings on different portions of the substrate.

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1(1 6~052 Further, ce~ain combinations of different metals may be provided for the su~strate and coating, for example, a porous coating of "Stellite" (Trademark) on a platinum/
iridium alloy base, for use in a heart pacemaker electrode.
The precise form of the prosthetic device or implant of the invention depends on the material of construction and the method used for the formation thereof. The essential property of the device is that throughout at least part thereof there is a network of interconnected passageways to allow soft tissue to grow into the device and become interlocked in the sub-surface by growth in the passageways.
The growth of soft tissue in this way results in incorporation of the prosthetic device or implant into the body and the permanent fixation of the device at the location ;
of incorporation, preventing accidental migration within the body. No gap is left between the surface of the prosthetic j device or implant and the adjacent tissue so that' the possibility of infection is decreased.
In some cases, it may be necessary to provide secure-ment of the prosthetic device or implant at the desired loca-tion to allow time for tissue ingrowth. Temporary or permanent securement may be provided, as desired, and suitable devices to achieve such securement include sutures, staples, clamps, clips or biocom~atible adhesives.
The manner of formation of the prosthetic devices and implants of the invention depends to a large extent on the material of construction. For example, where the prosthetic devices and implants are of the composite type consisting of a metal coating on a metal substrate, a sintering technique may be used, the particular sintering procedure depending to _ .

106~305Z

some extent on the size o~ the particles from which the porous coating is formed.
Metal particles suitable for formation of porous metal coatings generally are particles of alloys although some pure metals also may ~e used. One suitable material is the cobalt alloy that is known by the trade mark "VITALLIUM". Metal particles, from which the porous coating is formed, generally fall~ into one of four categories, namely ~500 mesh (less than about 20 microns~, -325+500 mesh ~ ~ -(about 20 to about 50 microns), -100+325 mesh (about 50 to ~ -about 200 microns) and ~100 mesh (greater than about 200 microns). The term "mesh" used herein refers to the U.S.
standard sieve mesh size.
Certain metals which otherwise are suitable for the formation of prosthetic devices and implants for soft tissue uses are pyrophoric at the particle sizes required. ;~
One such metal is pure titanium, which is an attractive prosthetic device or implant construction material owing to its inert character and light weight.
A porous structure of titanium having a network of ;~
interconnected pores substantially uniformly distributed throughout the structuxe may be formed on a coherent titanium or other metal substrate by thermal decomposition of titanium ~``
hydride particles on the metal substrate. This procedure also may be used to form a wholly porous structure.
This technique for the formation of a porous metal structure may be used with particles of any thermally decomposable metal compound or a mixture of such compounds.
Whether the metal itsel~ or a metal compound is used, roughly equivalent techniques may be utilized.

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.. . . , - , -In each cas~, the smooth coherent substrate is first roughened, for example, by blasting with abrasive material.
The coating of metal or metal compound particleq then is formed on the roughened surface. The metal in the substrate and coating usually are the same, but different metals may be used.
In one procedure, a binder for the metal or metal compound particles first is sprayed on the roughened surface and the device then is suspended in a flu~ized bed of powder, metal or metal compound particles to form a coating on the roughened surface. The coated body is withdrawn from the fluidized bed and the binder allowed to dry.
In an alternative procedure, the powder, metal or metal compound particles are mixed with the binder to form `
a fairly viscous slurxy which is spray aEplied to the roughened surface ;
to form the coating thereon which then is allowed to dry. i~
In a further procedure, the metal or metal compound particles and binder are slurried and the roughened surface is dipped into the slurry. Excess material is allowed to run off and the coated body is dried.
When the metal particles are used, the ~eform of dried coating and substrate is sintered to cause metal fusion interconnection of the metal particles, one with another and with the roughened substrate surface to pxovide a rigid porous structure having a network of interconnected pores substantially uniformly distributed throughout the coating.
In the case of the metal compound particles, after the ~ormation of the dried coating on the substrate, the ;`
preform is heated to an elevated temperature to cause ~-, - . .- - - : . ~ - - - :
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~068052 :
thermal decomposition of the titanium hydride and the forma~
tion of a porous coating of titanium metal particles which are connected together at their points of contact with each other and the substrate to define a network of inter-connected pores substantially uniformly distributed through-out the coating. The heating is generally carried out under a vacuum to remove the hydrogen formed in the decomposition.
It is possible to ~uild up any desired thickness of porous coating on the coherent substrate by presintering or preheating the dried coating to provide some green strength thereto and then repeating the coating and presintering or preheating operation for as many cycles as is required to build up the desired thickness. When the desired thickness has been achieved, the composite is sintered or heated to provide the required particle-particle and particle-substrate adhesions. ;
Following formation of the porous coating, it may be machined and refined, if desired, to improve its surface characteristics. The metal and metal compound particles generally are substantially spherical, although other geometrical shapes and mixtures of shapes may be used.
A porous metal coating also may be formed by rolling a fine mesh screen on a solid tube and securing the same thereto with the mesh openings being partly offset one from another.
Where the pro~thetic device or implant is constructed wholly or in part of polymeric material, a similar variety of techni~ues may be employed. Wholly porous polymeric products or composites of porous polymeric coatings on coherent substrates may be provided.

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106~052 The porous p~Lymer structure may be formed by uniformly dispersing solven~elutable particles in a continuous or discontinuous polymer phase, forming a coherent-shaped article from the dispersion having solvent-elutable particles substantially uniformly dispersed throughout the continuous solid polymer phase, and eluting the solvent~lutable particles from the article to provide a porous shaped polymer product having interconnected pores therein.
The microporous polymer structure may be provided in a wholly porous form or in a lamination with one or more coherent solid rigid or flexible polymer substrates by in-corporating a suitable lamination step in the above pro-cedure, or into the specific procedures described below.
A number of specific procedures may be utilized to carry out the above-described process, the particular one chosen depending on the shape of product desired, the nature of the polymer used and the form of product desired. One such procedure involves pulverizing the polymer to the required particle slze, mixing the powder with solvent-elutable particles and compressing the mixture at pressure~
below about 100 psi and at a temperature in the range of about 20 to about 350F. The compressed mixture may be molded or extruded to the desired shape and the resulting coherent-shaped article is leached to remove the solvent-elutable particles.
Another specific proceduxe which may be used involves blending together a moldable and/or extrudible, flexible polymer material and solvent- elutable particles in sufficient ~uantities to provide a continuous phase of polymer and a _ g - ~

~' -dispersed phase of ,~lvent-elutable particles in the blend.
Thereafter, the blend is molded or extruded to the desired shape and contacted with solvent to remove the solvent-elutable particles and leave an open network of inter-connected pores throughout the body.
In a modification of this procedure, the polymer may be provided as a solution into which the polymer particles are mixed.After removal of the solvent, the molding or extruding and leaching operations are carried out.
Yet another specific procedure for forming the microporous polymer product involves initial formation of beads of polymer having a core of solvent-elutable material by polymer solution coating of the core material, compression molding or extruding of the beads to the desired shape and ~-product leaching to remove the solvent-elutable material.
A further specific procedure for the formation of a microporous polymeric product includes forming a viscous casting solution of the polymer, dispersing the solvent- ;
elutable particles in the solution~ casting the solution on to a casting surface and, after removal of solvent, eluting the solvent-elutable particles from the casted material. -The solvent-elutable particles and the elution solvent used in the above described procedure should be non-toxic in nature so that any residual material in the porous structure is not harmful to body tissues or blood in use. Typically, solvent-elutable particles are water-soluble, for example, sodium chloride or sodium carbonate particles, and solvent elution is achieved using water.
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The particle size of the particles to a large degree dictates the pore size in t~e polymer body, although irregular pore shapes generally result. Pore sizes from about 10 to over 100 microns are possible, using particles in the range of about -500 to +100 mesh.
The pore size, volume and shape of the product may be controlled by varying the size, shape and distribution of the solvent-elutable particles and the weight ratio of the polymer.
Another procedure for the formation of a porous polymeric material is to cast the polymer around a lattice-work which then may be rolled or formed into the desired shape.
A further procedure for formation of a porous poly- ; -meric material involves providing a powdered solid polymer ;~
phase and a solvent phase including a solvent for the polymer. The liquid monomer phase is drawn rapidly through the polymer particles so as to allow dissolving of polymer at the surface of the polymer particles only and to cause the formation of particle-to-particle joints.
The wholly porou~ product formed in this latter pro-cedure may be combined with a rigid polymeric member to form a composite structure, if desired.
The invention may be used to provide numerous prosthetic devices and implants for use in soft tissue environments, in each case the prosthetic device or implant `
having a poxous zone allowing soft tissue ingrowth.
Prosthetic devices or implants may be provided for cardiovascular use, for example, heart pacemaker pulse generators, heart pacemaker electrodes, components of heart valve prostheses including the sewing ring to allow fixation 1068052 :
of the Yalve to the surrounding tissue, a~ energy storage devices and~or transducing devices, including energy trans- . -ducing devices receiving energy coupled into the body from :~
an outside energy source, used to power intracorporea~ `
blood pumping devices or other artificial internal organs.
Prosthetic devices or implants according to the ~.
invention may be used at interfaces of either intracorporeal or extracorporeal blood pumps with blood vessels.and surrounding soft tissue, including arteries, veins and vascular ~rafts, inside or outside the body to allow bonding .
of the natural vessels to the artificial blood conduits.
The invention may be used for the fixation and in-corporation of artificial blood vessel implants at the external surface of the implants, including shunts for haemodialysis. ~-Prosthetic devices or implants may be provided for use 1 -in plastic surgery for r~storing form, contour and/or bulk to soft tissue, including artificial breast implants, skull plates, facial rebui.lding implants, and body wall support systems.
The invention also finds use in the respiratory tract, allowing the provi~ion of an artificial trachea or bronchus and permanently-positioned tracheostomy tubes.
A further soft tissue environment wherein the inven- :
tion finds use is the genitourinary system, examples being artificial ureters a.nd fallopian tubes.
Devices also may be provided for the gastro-intestinal system, including an artificial esophagus and an artificial bile duct.
In the central nervous system, the invention may be ~068052 used to provide cerebrospinal fluid shunts.
The invention may ~e used in various body access devices, including haemodialysis shunts and transcutaneous introduction of conduits and wires fox mass and/or energy transfer to and from the body.
The invention may be used in orthopaedics to secure tendons, muscle and other soft tissue to bone, to obtain internal fixation and transcutaneous passage of artificial -limbs.
A further application of the invention is in endocrine devices to provide an interface for sampling from the surrounding interstitial fluid of one or more substances following the sensing of its or their concen-trations, to also provide an interface for releasing one or more substances into the surrounding tissue to be disseminated throughout the body.
The invention may also provide the tissue interface for a depot release device for releasing a drug or hormone ~`-or other substance into the surrounding tissue to be disseminated throughout the body, for example, the slow release of estrogen and/or progestigen for birth control, or the slow release of antibiotics. -In the ear, nose and throat region of the body, the invention may be used as an implantable hearing aid in the mastoid, a middle ear prosthetic, for example, for the -fixation of the stapes, and an artificial larynx with im~
proved fixation and/or improved transmission of sound.
The invention also may be used in various dental applications for the securement of dental prostheses to gingival tissue.

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~068052 The inventi~n, there~ore, has an extremely wide applica~ility and may be used to advantage in any soft tissue environment of the body to allow soft tissue in-growth into the particular prosthetic device or implant for incorporation of the same into the soft tissue environment.
The invention is illustrated by the following examples:
Example 1 .

This example illustrates the formation of a prosthetic ~ -device or implant of the invention.
A "V~TALLIUM" (Trade Mark) rod of 1/4 inch diameter was degreased and cleaned. An aqueous Vitallium powder slurry was made up containing 74 parts by weight of -500 mesh powder, 25 parts by weight of an aqueous solution of 1 percent methyl-cellulose, 1 part by weight of a 2 1/2 percent aqueous solution of dioctyl sodium sulfosuccinate i with 0.25 parts by weight of ammonium hydroxide.
The slurry was applied from an aerosol dispenser on to the rod which had first been roughened. After drying and sintering at 2050 to 2100F in a dry ~ydrogen atmos-phere for 10 to 15 minutes, a second coating was applied to provide a total thickness of about 50 microns. Following drying of the further coating, the coated rod was sintered at 2050 to 2100~ for about 1 hour. The product was cooled in the hydrogen atmosphere.
Examination of the product indicated that the powder particles had fused at each contact point between themselves and the rod and an interior uniform pore structure was formed with pore sizes ranging up to 20 microns.

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- ~ , 10680~2 Example 2 This example illustrates an alternative procedure for formation of a prosthetic device or implant according to the invention.
The surfaces of two titanium metal rods were roughened, ultrasonically cleaned and coated with a binder. -~
Titanium hydride particles which sized 100% -325 mesh, 85% -500 mesh, were applied to the surface from a fluidized bed to a thickness of about 100 microns.
One of the rods was heated for half an hour at about 1100C under a vacuum of 1 to 2 x 10 5 Torr to form a porous titanium metal coating. The other of the rods was heated for half an hour at about 1200C under a vacuum of 10 5 to 10 6 Torr to form a porous titanium metal coating.
Microscopic examination of sections of the coated rods revealed particle-to-particle fusion, fusion to the substrate and uniform distribution of interconnected pores throughout the porous coating. The coating porosity was estimated to be about 30 volume %.
The coating of the first mentioned coated rod ;
exhibited a shear strength of greater than about 1500 psi while the coating of the second mentioned coated rod exhibited a shear strength of greater than about 2000 psi. `

Exam~le 3 ;
This example illustrates the use of the present ~nvention in a soft tissue environment.
A prosthetic heart valve metal cage was totally coated with a porous coating formed from -500 mesh powder -following the procedure of Exa~ple 1.
~0 The coated heart valve ca~e was positioned in the ~ - . . : : .; .. . :

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heart of a dog for a two-month period. At the end of this period, a firm bond had developed between the ring of the valve and the surrounding soft tissue. Where struts of the valve were in contact with the heart wall, they were totally incorporated into the tissue.
Considerable force was necessary to separate the heart valve from the tissue and, after tearing the tissue from the heart valve, a scan using a scanning electron microscope showed tissue still embedded in the porous coating, indicating shearing at the coating/tissue interface.
Exam~le 4 This example illustrates the use of the present in~
vention in another soft tissue environment.
Stainless steel discs were coated with "Stellite"
powder of -500 mesh to a thickness of about 100 microns with a coating porosity of about 30% and embedded in the soft tissue of the chest wall of dogs. The dogs were sacrificed at varying periods from 3 weeks to 2 years and pull-out tests were conducted to determine the strength of the bond of the tissue to the coating.
The results are summarized in the following Table:
Table Time Pull Out Pressure _e

3 weeks

4 weeks o.s 2 months 1.3 3 months 2.8 2 years 3,0 : . -The results of the above Table show an increasing bond strength up to 3 months and then only a minor increase thereafter. The strengths involved are considerahly less than those involved in bone ingrowth (typically greater than 1000 psi~.
Examination of the porous surface of the pulled-out discs by scanning electron microscopy revealed shearing to have occurred at the tissue-coating interface and ingrown tissue to be present in the coating.
10 Example 5 -This example contains further illustration of the use of the present invention in a soft tissue environment.
Heart pacemaker electrode tips were formed by coating platinum-iridium alloy with "Stellite" powder of `, two sizes. The first size was -325+500 mesh and was coated to a thickness of about 300 microns with a coating porosity of about 30%. The second size was -100+325 mesh and was coated to a thickness of about 500 microns with a coating porosity of about 30~. ;
Two samples of each different electrode tip were ;
implanted in the right ventricle of dogs for a three-month period. After sacrifice of each dog, a heart section was taken through the tip and heart muscle. Examination re-vealed tissue ingrowth into the porous surface in each case.
Example 6 :
This example illustrates the formation of a vascular graft and the use thereof in a soft tissue environment.
A 30% solution of a hydrophilic polyurethane con-sisting of urea interlinked blocks of polyether and chain extended polyurethane in dimethyl fbrmamide was mixed with sodium chloride crystals of average size -200~300 mesh in a 1~68052 1:1 weight ratio of sodium chloride to polymer to form a viscous solution. The solution was positioned in a glass tube and a pervious woven Dacron fabric tube was positioned in the solution.
The tube was allowed to pass a conically-shaped plumb ball of maximum diameter approximately 4 mm attached to the lower end of a string to cast a reinforced polymer tube inside the glass tube. -Aftex drying under an infra red heating lamp, the reinforced polymer tube was removed from the glass tube by immersion in water and annealed by boiling in the water.
The operations of immersion and annealing also resulted in leaching the sodium chloride from the tube to a wholly porous fabric reinforced microporous tube.
The resulting tube of S cm length was used as a vascular graft in a dog. After 1 month of implantation, the graft was found by light microscopy to be patent and the exterior surface showed tissue ingrowth.

The present invention, therefore, provides novel prosthetic devices or implants for 90ft ti~sue uses which allow soft tissue ingrowth. Modifications are possible within the scope of the invention.

Claims

The embodiments of the invention in which an exculsive property or privilege is claimed are defined as follows:

1. A prosthetic device or implant suitable for permanent incorporation into a soft tissue environment of a human body, constructed of a material substantially inert to body fluids selected from the group consisting of metal , polymeric materials, ceramic, carbon and combinations of two or more of such materials, said device having a porous outer surface region adapted to contact said soft tissue and in fluid flow communication with a network of interconnected pores in a subsurface, said network of interconnected pores having a porosity greater than about 8% and the interstitial pore size is about 1 to about 1000 microns, whereby said soft tissue may grow through said surface pores and into said subsurface network when located in said soft tissue environment to incorporate said prosthetic device or implant into said body and render the tissue surface interface more resistant to infection.

2. The device or implant of claim 1 wherein said porosity is about 10 to about 50%.

3. The device or implant of claim 1 wherein said inter-stitial pore size is about 20 to about 300 microns.

4. The device or implant of claim 1 which is wholly porous.

5. The device or implant of claim 1 wherein said surface and subsurface are provided by an adherent porous coating adhered to a dense coherent substrate surface.

6. The device or implant of claim 6 wherein said coating has a thickness of about 1 to about 10,000 microns.

7. The device or implant of claim 1 wherein said surface and subsurface are provided by a porous coating consisting of a plurality of small discrete particles bonded together at their points of contact with each other to define a plurality of connected interstitial pores uniformly distributed throughout said coating and said coating is adhered to a dense coherent substrate surface, said coating having a porosity of about 10 to about 50%, and a thickness of about 20 to about 1000 microns and the interstitial pore size being about 20 to about 300 microns.

8. The device or implant of claim 1 constructed of titanium.

9. The device or implant of claim 1 wherein the porous structure is formed by thermal decomposition of titanium hydride particles.

10. The device or implant of claim 1 in the form of artificial cardiovascular members having said porous surface provided on soft tissue engaging surfaces thereof.

11. The device of claim 10, wherein said artificial cardiovascular member is selected from the group consisting of heart pacemaker pulse generators, heart pacemaker electrodes, components of heart valve prostheses and energy storage and/or transducing devices.

12. The device or implant of claim 10, wherein said artificial cardiovascular member is provided at the interfaces of intracorporeal or extracorporeal blood pumps with blood vessels and surrounding soft tissue.

13. The device or implant of claim 10, wherein said artificial cardiovascular member is an artificial blood vessel implant.

14. The device or implant of claim 1 in the form of a plastic surgery device for restoring form, contour and/or bulk to soft tissue and having said porous surface provided on the soft tissue engaging surfaces thereof.

15. The device or implant of claim 14, wherein said plastic surgery device is selected from the group consisting of artificial breast implants, skull plates, facial re-building implants and body wall support systems.

16. The device or implant of claim 1 in the form of an artificial respiratory tract member having said porous surface provided on the soft tissue engaging surfaces thereof.

17. The device or implant of claim 16, wherein said artificial respiratory tract member is selected from the group consisting of an artificial trachea, an artificial bronchus and a tracheostomy tube.

18. The device or implant of claim 1 in the form of an artificial genitourinary system member having said porous surface provided on the soft tissue engaging surfaces thereof.

19. The device or implant of claim 18, wherein said genitourinary system member is selected from artificial ureters and artificial fallopian tubes.

20. The device or implant of claim 1 in the form of an artificial gastrointestinal system member having said porous surface provided on the soft tissue engaging surfaces thereof.

21. The device or implant of claim 20, wherein said gastrointestinal system member is selected from the group consisting of an artificial esophagus and an artificial bile duct.

22. The device or implant of claim 1, in the form of a cerebrospinal fluid shunt having said porous surface provided on the soft tissue engaging surfaces thereof.

23. The device or implant of claim 1 in the form of a body access device having said porous surface provided on the soft tissue engaging surfaces thereof.

24, The device or implant of claim 23, wherein said body access device is selected from the group consisting of haemodialysis shunts and transcutaneous conduits and wires for mass and/or energy transfer to and from the body.

25. The device or implant of claim 1 in the form of an orthopaedic device adapted to engage soft tissue and having said porous surface provided on the soft tissue engaging surfaces thereof.

26. The device or implant of claim 25, wherein said orthopaedic device is selected from securement devices for securement of tendon, muscle or other soft tissue to bone and on artificial limbs.

27. The device or implant of claim 1 in the form of an endocrine device having said porous surface provided on the soft tissue engaging surfaces thereof.

28. The device or implant of claim 27, wherein said endocrine device is one having a surface for the sampling from the surrounding interstitial fluid of one or more substances following the sensing of the concentration thereof.

29. The device or implant of claim 27, wherein said endocrine device is one having a surface for releasing one or more substances into the surrounding soft tissue to be disseminated throughout the body.

30. The device or implant of claim 1 in the form of a depot release device having said porous surface pro-vided on the soft tissue engaging surfaces thereof for release of a substance into the surrounding soft tissue for dissemination throughout the body.

31. The device or implant of claim 30 wherein said depot release device contains a substance for dissemina-tion selected from the group consisting of estrogen, progestogen and mixtures thereof and antibiotics.

32. The device or implant of claim 1 in the form of an artificial device for use in the ear, nose and throat region of the body and having said porous surface provided on the soft tissue engaging surfaces thereof.

33. The device or implant of claim 32, wherein said device is selected from the group consisting of an implantable hearing aid, a middle ear prosthesis and an artificial larynx.

34. The device or implant of claim 1 in the form of a dental prosthesis having said porous surfaces provided on the gingival engaging surfaces thereof.

35. The device or implant of claim 1 in the form of a pacemaker electrode tip comprising a coherent metal sub-strate and a porous metal coating constituting said surface and subsurface.