Ipsofactoj.com: International Cases [2001] Part 2 Case 14 [Ch.D]



McGhan Medical UK Ltd

- vs -

Nagor Ltd


28 FEBRUARY 2001


R.M. Fysh, QC


  1. This is an action for the infringement of patent no. 2 225 016 ("the Patent") which stands by assignment in the name of the claimant, McGhan Medical UK Limited ("McGhan") the latter being the United Kingdom subsidiary of a US company. The Patent is entitled 'Silicone foam covering and method for making it' and claims a priority date of 12 October 1988. The title would not perhaps suggest the principal purpose of the articles which are to be made by the method claimed, namely prostheses for implantation into the human body. The alleged infringement is in fact a textured breast implant which is made by the first defendant and sold by the second under the trade mark NAGOTEX. There is for present purposes no distinction between the cases of the first and second defendants, to whom I shall collectively refer as "Nagor". Nagor deny infringement and counterclaim for revocation of the Patent on three statutory grounds under the Patents Act 1977 ('the Act').

  2. All three claims of the Patent are alleged to be infringed and it stands admitted that if claim 1 is infringed so also are claims 2 and 3. Furthermore, independent validity of these claims is not maintained. In what follows I need therefore consider only the case on claim 1, which is a method claim.


  3. Though introduced and claimed in general terms ('Silicone foam covering...'), the Patent is directed to silicone prostheses for implantation within the human body. In fact, both parties' experts (and indeed counsel) introduced the case as if the Patent was almost entirely concerned with breast implants. Strictly speaking, it is not. Nonetheless, since the evidence relating to the general and technical background was directed largely to breast implants, what follows must necessarily record in synopsis evidence relating to that particular aspect.

  4. Implanted prostheses replace parts of the body which have become damaged or diseased. They are also used for altering the appearance of parts of the body, such as the breast. Prosthetic implants have been used for some 50 years before the priority date of the Patent and for this, use has been made of a wide variety of materials: metals for hips, textiles for arteries and a range of plastics materials for blood-carrying devices and shunts, chronic catheters and for mammary implants. Among the plastics materials used for prostheses, silicone elastomers, also known as silicon rubber or silicones, have been particularly favoured as they combine flexibility with chemical and thus physiological inertness. Being long-chain polymers which require cure, the properties of silicones may be adjusted from those having rubber-like properties to those having mobile characteristics, such as silicone gels. The Patent is concerned with both. It seems that silicones having various physical characteristics had been used in making prostheses for many years before the priority date of the Patent.

  5. The early breast implants were made of a shaped silicone elastomer shell filled with silicone gel or occasionally with saline – the so-called Cronin breast implants. By the late 1960's two particular problems with such prostheses had begun to appear: 'implant displacement' or 'migration' and 'capsular contracture' or 'hard encapsulation'. Take the first problem: migration. After implantation, it is important for a prosthesis to remain stable in situ. But this does not always happen. A breast implant for example, has a natural tendency to become displaced within the proximate area of implantation. However, nature counterbalances this by a process of 'anchoring' since, when an implant is placed in soft tissue, the patient's immune system responds: connective tissue in the form of the protein collagen accumulates as fibres to surround the implant tending to 'anchor' it. This process is termed 'fibrosis' or 'encapsulation'; it provides a 'capsule to wall off the foreign body' as the claimants' expert, Professor Alan Roberts put it. But with large, smooth prostheses such as Cronin implants, this does not always occur to a satisfactory extent and the implant may still lack stability. On the other hand, by fibrosis, the body can lay down too much fibrous tissue which, particularly as it matures, tends to contract causing compression of the implant and associated pain and discomfort. This is capsular contracture or 'hard' encapsulation and may lead to the need for further surgical intervention so as to remove the implant, sometimes together with associated soft tissue. Professor Roberts summarised the situation as follows:

    A fine balance must be achieved: the tissue ingrowth must be sufficient to anchor the implant in place, that is, the tissue must be captured. However, the tissue ingrowth must not be so deep as to lead to problems .... the tissue should not be 'integrated' into the implant .... an ideal breast implant prosthesis might be considered to be one which promotes tissue capture but not tissue integration.

  6. So as to achieve a better balance of properties, workers looked at both the materials from which breast prostheses were made and at how the surfaces of implants might be modified. As Professor David Williams, the defendants' expert put it:

    It was postulated that if the implant had a porous surface, that would encourage the connective tissue to grow into the surface, thereby stabilising the prosthesis.

    To the same effect was the evidence of Prof Roberts:

    .... fixation has been achieved by the use of prosthesis materials with surface structures into which tissue can grow.

    And so in the 1970's, the first prostheses with 'roughened' surfaces were introduced. Such prostheses were roughened either overall or in patches or were porous. This stabilised the implant and at the same time disrupted the build-up of excessive collagen around it. Many such implants were made of a polyurethane foam outer layer bonded to the conventional filled silicone shell. This polyurethane foam had an 'open cell' structure; it had cavities which interconnected with one another. In other words, it was like a bath sponge which lets air or water pass from cell to cell. I shall return to the question of foams having an open cell construction.

  7. However, prostheses made of polyurethane foam were not without problems of their own. Briefly, these problems were associated not with the 'mechanical' performance of such prostheses in situ but with the chemical and physical characteristics inherent in the use of polyurethane as an implant material. Polyurethane it appears, oxidised and/or disintegrated causing foam particles to separate and collect around the implant. These secondary foreign bodies then became a potential source of infection. The experts were not in agreement as to whether recognition of this problem arose in the early or late 1980's, but again this detail may be unimportant. What is relevant is that problems with the use of polyurethane foams were well recognised at the priority date of the Patent; a polyurethane covering was not always an ideal replacement for the Cronin breast implant. Indeed this problem is the entrée for the teaching of the Patent.


  8. The Patent opens thus:

    This invention relates to the manufacture of a silicone foam covering and especially to such a foam covering which is useful for the surface of implants for implantation in the human body.

    There follow passages which those involved in this case, witnesses and counsel, read as being directed essentially to breast implants, even though there are only two explicit references to such implants (pp 1 and 6).

  9. First, in a review of the prior art, it is said that because of their inert character, medical grade silicones are "the preferred material of construction" for such implants. However, such implants with smooth surfaces have the tendency to become

    Encapsulated in a hard encapsulation developed by the body when it recognises the implant as a foreign body.

    I have already referred to this 'hard' encapsulation. The Patent then moves to the availability of 'a line of prosthesis' having a 'roughened' surface to cover the earlier smooth implants and mentions in particular, the use of a polyurethane 'open cell foam' layer 'cleanly cut to make this surface texture' for this purpose. Such foams have, it says,

    .... a wealth of cavities and fibrous structures.

    The narrative continues (p.2):

    It would be preferred to use a silicone foam for this purpose, but known methods used to provide silicone foam have not provided a foam structure which the inventor herein regards as suitable.

    [my emphasis]

    Silicone foams like polyurethane foams were evidently known for prosthetic use. The reader is not however informed as to why the inventor was of the view that that silicone foams made by the known methods were not 'suitable'.

  10. The Patent continues with an important definition: 'foam' (p.2):

    The terms 'foam' and 'sponge' are used interchangeably herein to donate [sic] an open cell construction wherein cavities in the material interconnect with one another.

    This definition is consistent with other passages in the specification and probably also with Figs. 2-4. It is in my judgment clear that the reader is being told that the silicone foams made by the method proposed in the Patent are structurally no different in any material respect from the prior art open cell foams mentioned on page 2 which were made of both polyurethane and silicone; both in other words, were of open cell construction.

  11. So what is the problem for which the invention is said to provide a solution? The object of the invention is stated to be the provision of a silicone foam (as defined) and more particularly, a method of making it (p.2)

    .... and especially to form it on the surface of a continuous substrate so the resulting covering construction has an inherent and continuous outer roughened surface region ....

    The resultant surface is said to contain 'cavities and fibrous material' (to which reference has been made in connection with the prior art polyurethane foam) since this is what is 'important to surrounding tissue'. By that expression, I think what the writer means is 'having the capability of encouraging the growth of tissue without hard encapsulation' or as Mr. Tappin counsel for McGhan put it, 'tissue capture'. This 'cellular' construction occurs only on the surface; it does not extend all the way through the material since a depth of about one millimetre is said to be all that is needed for proper functioning. Deeper cellular construction 'can itself lead to problems of tissue growth'.

  12. A method for preparing such silicone foam coating for 'an article' is proposed. This is the consistory clause to claim 1. In essence, the method consists of embedding finely divided crystalline material having particular characteristics into the uncured 'fluid' silicone surface of the article to be coated, curing the silicone thereafter and then dissolving out such crystalline material. This leaves a porous skeletal structure on the surface of the substrate. At trial, this was referred to as the 'washout technique'; I shall also use this phrase in the same way.

  13. The nature of the crystalline material used in this method is regarded by the patentee as being important. The crystalline material must comprise particles of varying diameter. Furthermore, none of the particles may have a diameter greater than the thickness of the uncured fluid layer. In addition, the use of crystals 'all of substantially the same size' results in a 'less useful' foam because particles of equal size pack together to form a matrix of relatively low percentage of volume - or low 'packing ratio'. Therefore, the sizes of the crystalline material used must tend to increase the 'packing ratio' of the crystalline particles as a group. In this way, after washout, the resultant cured silicone surface has an increased 'roughness' (p.4) and contains 'the maximum number of interconnecting interstitial cavities for tissue ingrowth' (p. 3). The latter are also referred to as 'open cavities' or as being 'open-cellular' (pp. 4 and 5) and as a 'construction with many cavities, tendrils, walls and fragments of walls' (pp. 5-6).

  14. The embedding of the soluble crystals is effected by 'incorporating' them or 'pressing [them] into the upper surface' to a chosen depth, the depth of the resultant foam being established as a distinct layer by controlling the depth to which the crystals 'extend' prior to washout. They must not however be embedded throughout the entire depth of the silicone (p. 4): see para 11 above. Significantly, as a group, the crystals 'are embraced by the liquid silicone' (p. 5). The preferred crystals are common salt crystals and the preferred solvent is water.

  15. No working examples are given. On the question of salt crystal sizes however, the patentee identifies the US manufacturer of two 'useful' sizes of salt crystal, the sizes being defined by ranges – between 30 and 50 mesh (i.e. common table salt) and between 16 and 40 mesh (KD Fine Solar Salt). These may be mixed in about equal proportions for good results.

  16. The Patent contains four schematic cross-sectional drawings which are said to illustrate the method of making the foam substrate at various stages.

    IV. CLAIM 1

  17. Claim 1 is a method claim which reads as follows, the words the meaning of which were in dispute at trial being underlined:

    The method of preparing a silicone foam covering for an article comprising:

    1. forming a fluid layer of uncured silicone on the surface of said article,

    2. embedding a finely divided crystalline material into said fluid layer, said finely divided crystalline material comprising a plurality of particles of varying diameter, none of said particles having a diameter greater than the thickness of said fluid layer,

    3. curing the fluid layer of silicone

    4. dissolving said crystalline material with a solvent which does not dissolve the cured silicone

    5. the crystalline material including particles having a plurality of sizes

    6. thereby to increase the packing ratio of the crystalline particles as a group, and

    7. whereby to produce a structure of said cured silicone having the maximum number of interconnecting interstitial cavities for tissue ingrowth.

    Integers (e), (f) and (g) have been set out as separate integers for the purposes of this judgment. It will be seen that the claim is not limited to prostheses, let alone to breast implants. It will also be noted that no numerical qualification to the range of sizes of the crystalline material is prescribed; any range will evidently be suitable subject to the fulfilment of integers (e), (f) and (g). There is neither a numeric nor a relative limit either to the depth of the 'embedding' - or to that of the fluid layer.


  18. The claimants called Professor Alan Roberts who is currently a consultant clinical scientist and is also director of research for Bradford Hospitals NHS Trust. He is based at St Luke's Hospital, Bradford where he has been head of the Biomaterials Laboratory in the Department of Plastic and Maxillo-facial surgery since 1960. He has held the appointment of Honorary Professor of the University of Bradford since 1998. In addition, since 1993 he has been Professor of Biomaterials in Surgery at the Academic Surgical Unit of the School of Medicine at the University of Hull. As Exhibit ACR-1 to his Report shows, Professor Roberts has had a distinguished career both professionally and in the armed services. He has received numerous awards for his work and is the author and co-author of many papers in the field of internal, external and dental prosthetic reconstruction and in the field of plastic surgery - particularly in facial reconstruction. He has had experience with the use of silicones. For example, his thesis for Membership of the Institute of Biology was entitled "Silicone Polymers in Reconstructive Surgery" (1970). His expertise in the field of prosthetics with particular emphasis on soft tissue reconstruction covers some 45 years. His Report concludes thus:

    I have been predominantly involved in the field of soft tissue implants and a large amount of my work has been dedicated to research into silicone elastomers and their application as breast implant materials.

  19. The defendants called Professor David Williams. Professor Williams is at present Pro Vice Chancellor and Professor of Clinical Engineering at the University of Liverpool. He too has had a distinguished career and has been given a number of impressive awards. Professor Williams' background and early work was in the field of physical metallurgy and 'bio-materials'. He has worked and taught in the field of prostheses, biomaterials and implantable medical and dental devices for some 30 years. He is co-author of the first comprehensive textbook in the bio-materials field, "Implants in Surgery" (1973). He has knowledge of breast implants both through his own work and as a result of being involved as a consultant to industry. In view of the issues which arise in this case on infringement, I shall quote a sentence from paragraph 6 of his Report:

    I am familiar with and use on a regular basis, instruments for examining biomaterial surfaces, including the scanning electron microscope ("SEM") and have published studies that have involved the use of this equipment.

  20. Though they were not from industry, both experts were obviously men of considerable experience and distinction within the general field of medical and dental prostheses going back many years. Both men were in my assessment, witnesses of candour.

  21. There is however one aspect of the experts' evidence which needs to be raised at the outset and that is, which witness had the greater experience of working with scanning electron microscopes and, more important, which had the greater expertise in interpreting the photographic images of materials examined by SEM. As will be seen, this has a major bearing on the question of infringement which in this case, depends almost entirely upon the proper interpretation of SEM photographs of sections of Nagor's alleged infringements. Mr. Hacon, counsel for Nagor, submitted that on the evidence, Prof. Williams had substantially more 'hands on' experience with SEMs and the interpretation of SEM photographs than had Prof Roberts. Mr. Tappin for McGhan submitted that there was no significant difference in their expertise.

  22. The dispute between the experts on the SEM protocols and techniques adopted in this case was well developed by the time of exchange of the supplementary reports. Prof Roberts had arranged for the relevant work to be carried out for him by the School of Materials of the University of Leeds. Those responsible made SEM photographs of cross-sections of NAGOTEX material by 'snapping' it after immersion in liquid nitrogen and examining the fracture. This was criticised by Prof Williams on the basis that since the line of fracture will follow the path of least resistance, an unrepresentative cross-section may result. The appropriate technique he said, would be to incise the material with a sharp scalpel – and this indeed was done for Nagor's own SEM photographs. There were in addition, criticisms of McGhan's angle of view and of the magnification used. I shall return to this. Not surprisingly, the experts were asked a number of questions about the protocols and techniques used to obtain these SEM photographs and on the interpretation of the photographs which were taken. Some answers given by Prof Roberts led me to ask both witnesses about their personal involvement with SEMs at the conclusion of their respective re-examinations. The answers given by Prof. Roberts may be compared with those of Prof Williams. Prof Williams had I feel, a greater, personal and routine experience with SEMs, with sample preparation and with the interpretation of SEM photographs than had Prof Roberts. Where the evidence of the two witnesses conflict on the interpretation of the SEM photographs, I prefer that of Prof Williams. In addition, I should record that having observed both witnesses giving evidence on this topic that of Prof Williams was I consider, given with more conviction and authority than that of Prof Roberts.


  23. Next, the identity of the addressee of the Patent must be established. This notional person is deemed to possess the common general knowledge of the subject matter in question. It is through the eyes of the skilled addressee that the Patent will fall to be interpreted. And it is by the standards of this person that the question of inventive step is to be judged when this topic is addressed in the counterclaim.

  24. A patent is addressed to persons who are likely to have a practical interest in its subject matter or to act on the directions given in it for it to be put into practice. The addressee is deemed to be unimaginative and uninventive but is equipped nevertheless with a reasonable degree of intelligence and with a wish to make the directions in the patent work. The qualification of such a person will of course depend on the subject matter in issue and such a 'person' may where necessary, be regarded as a team, particularly in cases where more than one discipline is involved. All this is settled law.

  25. In this case, there was no serious issue on the characteristics of the notional addressee. Both parties saw the addressee to be a team working within a company manufacturing breast implants which comprised a bio-engineer and a graduate with experience of polymers. Prof Roberts also added a clinician to the team having familiarity with post-operative problems associated with breast implants. In the end, this addition was I think, accepted by Prof Williams. In my judgment, Prof. Roberts' team best approximates to the notional addressee with the qualification that his clinician is not to be regarded as a person of professional seniority. I would add that neither expert was put forward as fulfilling this role.


  26. In order properly to construe the Patent and to assess the significance of the cited prior art, it is necessary to establish the common general knowledge which the notional addressee is deemed to possess at the priority date. The correct approach to assessing the proper level of common general knowledge has been established in the judgment of Sachs LJ in the General Tire v Firestone Tyre [1972] RPC 457 case as elaborated by later cases such as Beloit v Valmet. In this case, no issue on questions of principle arose.

  27. In Section B above, 'General and Technical Background to the Patent', I considered some breast implants which were in use immediately before the priority date of the Patent and in summary form, set out the current thinking of clinicians and others with regard to such products. This in my judgment suffices to epitomise the common general knowledge which would be possessed by the skilled addressee at the time, with the following additions and qualification.

  28. By October 1988, the priority date of the Patent, the problems of migration and hard encapsulation were very well known to clinicians and to those employed by manufacturers of breast implants. The skilled man would thus be well aware of these problems and of the fact that they presented most difficulty with smooth-surface breast implants. It was also appreciated how these problems arose and that they had been alleviated if not in many cases, overcome by the use of polyurethane foam as a covering for the older smooth-surface implants. In the words of the Patent, the polyurethane foam provided 'a wealth of cavities and fibrous structures'; this enabled the surrounding tissue to get a grip on the implant ('ingrowth') without encouraging it to lay down too much collagen to generate hard encapsulation.

  29. I consider that the skilled man would also have been aware that these polyurethane foams possessed an open cell structure and that purely from the 'mechanical' point of view, this structure in any material was likely to promote improved tissue capture in situ within the patient.

  30. The skilled man would have been aware of the fact that by that time, some concern had arisen over the use of polyurethane as a foam material for this purpose and that the cause of concern lay in the nature of the polymer itself rather than its initial physical structure. Articles in clinical literature were put to the experts in cross-examination, mainly by McGhan with an eye no doubt to meeting Nagors' case on obviousness (i.e., to lay a basis for a 'long felt want' argument) to show that problems concerning the use of polyurethane foam as an implant material were being voiced as early as the 1970's. No doubt this is true, but I am not convinced that the knowledge which can properly be accredited to the skilled man would cover the contents of such articles. The evidence was not comprehensive as to the degree, extent or effect of these concerns; this seems at the time rather to have been an area of personal opinion. In the end I am inclined to agree with Prof Williams that "Not everybody thought it was a problem". I do not for example believe that by the priority date, the skilled man would have regarded the use of polyurethane foams for breast implants as being unacceptable – as Mr. Tappin put it to Prof Williams.

  31. The skilled man would I think have been aware that of all potential candidates for use as breast implant material, silicones were the most desirable, principally because of their physiological inertness.

  32. The skilled man would have been well aware that the standard way of creating foams in polymers in general was by chemical means, that is by using blowing agents and a catalyst so as to create the required cellular structure. This for example, was how both the polyurethane and silicone foams were made before the priority date. In my judgment, the reference in the Patent to 'known methods to provide silicone foam' (see para 9, above) would be understood to refer to just such chemical methods.

  33. Though not perhaps an item of common general knowledge of the art, the question of the skilled worker's awareness of product liability claims for defective breast implants was raised in the cross-examination of Prof Williams.


    Product liability was not a concern before 1986?


    It was a minimal concern, primarily because of the way in which medical devices were regulated in the United States and the whole question of product liability of breast implants became significant in the mid-1980's. This was primarily because of some concerns and suggestions that the FDA may wish to re-classify breast implants at this time.

    It seems to me possible but not perhaps essential to add such knowledge to that of the skilled addressee who after all, is deemed to be the employee of a breast implant manufacturer which would be likely to be adversely affected by such a claim.



  34. I detected no particular issue between the parties as to the correct approach to construction of the Patent and for that reason I have no need to dwell at any length upon the principles of law to be adopted.

  35. In brief, the aim of the process of interpretation of a patent is to combine fair protection for the patentee with a reasonable degree of certainty for third parties: The Protocol on Interpretation of Article 69 EPC as applied by the Patents Act 1977, s. 125. This has in fact always been the approach of the courts in England: Catnic v Hill & Smith [1982] RPC 183. In this case, the House of Lords held that a patent and its claims must be construed in a purposive manner, through the eyes of the worker skilled in the art in question, its purpose being ascertained from reading the document as a whole. In this context, the so-called Improver[a] questions were formulated so that what has been called 'immaterial variants' to a claimed invention, should nevertheless be regarded as falling within the monopoly. Construction is a matter for the court but words having a technical meaning in context may properly be the subject of expert evidence. The court will therefore construe the patent objectively whilst adopting the mantle of the notional addressee to whom it is directed and in the light of the common general knowledge which he is assumed to possess. Specific prior art which does not form part of the common general knowledge is disregarded for this purpose as is knowledge of the alleged infringement. The patent will be construed as of its application date: Biogen v Medeva [1997] RPC 1 at 53-54.

    CLAIM 1

  36. In part D above, I set out claim 1 dividing it into convenient integers and putting in italics the words and phrases which now require consideration.

    (a) Foam covering

  37. 'Foam' is of course an ordinary English word the significance of which hardly seems to demand exegesis. We are however in the world of materials science and so, as will be seen, the matter must be looked at more closely. This is a key word in this case.

  38. First, in describing foams, the materials scientist draws a distinction between 'closed cell constructions' and 'open cell constructions'. The distinction was explained by Prof Williams in a passage with which Prof Roberts agreed:

    Foams and sponges come in two types: open and closed cell constructions. The foam on the top of beer would be an example of a closed cell construction. It is made up of cells which do not connect one with the other. On the other hand, a bath sponge is an example of an open cell construction. The cells are connected so that air or water can pass from cell to cell .... there must be cells each in the form of an enclosed cavity.

    In his Report, Prof Roberts helpfully exhibits a photograph of a magnified portion of polyurethane (Exhibit ACR-3) which he describes as having an 'open cell' structure. The Patent is only concerned with foams (including the prior art foams) having this construction.

  39. In the context of the Patent, 'foam' is qualified by the adjective 'silicone' which undoubtedly is a technical word. The phrase 'silicone foam' should obviously be looked at in the light of the rest of the specification and if necessary, of evidence as to any special meaning of which the court should be aware. As already noted (para 10 above), the Patent defines 'foam' (p 2):

    The terms 'foam' and 'sponge' are used interchangeably herein to denote an open cell construction wherein cavities in the material interconnect with one another.

    That is also the way the experts understood the term 'open cell foam' in the context of materials science; it also accords visually with Prof Roberts' photograph ACR-3. Significantly, in the Patent, the word 'foam' is used in just the same way to describe both the prior art polyurethane and silicone foams, the former being said to possess "a wealth of cavities and fibrous structures". A little further down page 2, the silicone foams produced in accordance with the method proposed are also said to possess 'cavities and fibrous material'. It is clear that both the prior art polyurethane and silicone foam and the silicone foam of the invention have been put forward as having generally the same sort of structure.

  40. I would add three further observations at this juncture: first, the purpose of providing this open cell structure in both polyurethane and silicone foams is to encourage a satisfactory degree of tissue engagement into the outer surface of the implant so as to stabilise it without totally integrating it. It also has the effect of disrupting collagen build up which is responsible for 'hard' encapsulation. As I read the evidence, from the structural point of view, polyurethane foams were not to be faulted for failing to achieve these ends; the vice with such foams was the chemical instability of the polyurethane of which they were made which over a period of time, sometimes resulted in structural breakdown of the foam and site infection in the patient. It is the evident intention of the patentee to retain the structural benefit of such polyurethane foam while making use of "medical grade silicones which are the preferred material of construction" for prostheses (p. 1).

  41. As for the prior art silicone foams mentioned by the patentee, one is not told what the patentee's problem was other than the 'foam structure' made by 'known methods' was in some way 'unsuitable', even though it was by definition, of the same general open cell construction. Moreover, the evidence in the case provides no enlightenment as to this either. For example, no structural or other problems are identified in the literature tendered in this case associated with the use of silicone foams for implants. In the end, I confess to having been somewhat puzzled by this aspect of the McGhan proposal.

  42. Secondly, with reference to 'surface', the term 'roughness' is used from time to time in the Patent (see for example, pp 2 and 4). I do not consider that this attribute is relevant to whether or not a 'foam' is present on the surface of a particular prosthesis; the term seems to have been used to contrast the smooth surface of the Cronin implants. That was also the view of the experts. Rather, one must look to see whether this open cell porosity in the surface silicone layer has been created by the claimed method.

  43. The third observation concerns the effect of the word 'covering' in 'foam covering'. McGhan submitted that the claims are not limited to the case in which the surface of the implant is entirely made of 'foam'. This is true as a matter of language. But 'covering' must be given a purposive construction. The foam of claim 1 must in my judgment continuously cover at least the parts of the 'article'/substrate in question which are in contact with tissue – which in practice must mean virtually the whole item. The teaching of the specification as a whole leaves no scope in my judgment for a 'patchy' or intermittent foam, a covering in other words which is within the claim over one part of the article because it is indeed a 'foam' but not in another because say, it consists of pits and surface craters. The same open cell foam structure must exist over all the 'covering' to promote the necessary 'tissue capture'.

    (b) Fluid layer

  44. Again, these are ordinary English words. To a materials scientist, fluidity is a matter of degree and thus the word 'fluid' can in practice have a spectrum of meaning. Since the Patent does not prescribe a standard, how fluid is the 'fluid layer' to be? What is its purpose? The phrase falls to be construed in relation to the condition of the surface of the silicone layer on the substrate before curing. When it is in that condition, what is it required to do? It is required to be in a sufficiently fluid state to be able to receive and 'embed' tightly packed crystalline material before the layer is cured and the crystals subjected to washout, so as to leave a multitude of open cells. In this way the silicone foam is created and for this reason, 'foam' and 'fluid layer' are functionally interrelated. In my judgment, 'fluid layer' is used in that sense. I shall next consider the word 'embed'.

    (c) Embedding a ... crystalline material into the said fluid layer ...

  45. One can embed something in something else either wholly or partially. A fossil fly can for example be entirely embedded in amber and on the other hand, a boulder can be embedded in the side of a hill, part of it being visible. There are intermediate usages too. Thus, microscope specimens are embedded in fixing agents prior to sectioning. Here, though the specimen does not emerge from the surface of the fixing agent, it is nonetheless exposed. It was agreed that 'embed' is not a term of art. To 'embed' is in my view a verb which draws meaning from its context.

  46. Nagor's submission was that the phrase should be given a comprehensive meaning i.e. so as to cover all the aforementioned situations. It was met so they argued, when the crystalline material was retained in the fluid layer in either a wholly or a partly submerged condition. I do not consider this to be correct as it ignores the context. A key sentence to the contextual meaning of this phrase is to be found on page 5 of the Patent:

    The crystals become embedded in the silicone...As a group, [the crystals] are embraced by the liquid silicone.

    [my emphasis]

    In my judgment, this language does not allow for protuberant bits of crystal or for partial embedding. This is not I believe, what the patentee had in mind when proposing as it were, approximately (and certainly functionally) to replicate in silicone, the open cell construction of polyurethane foams. In my judgment, this integer requires that the crystalline material should penetrate and actually be submerged under the liquid silicone layer. This is the construction for which McGhan contend. In his cross-examination of Prof Williams, Mr. Tappin put it well when he suggested that in order to achieve the foam proposed in the Patent, one has to arrange matters so that the crystals should become the cast for the foam being made.

  47. The terminal phrase to integer (b) of claim 1 (which will be considered next)

    none of the said particles having a diameter greater than the thickness of the said fluid layer

    also supports this construction in that a maximum crystal size should be chosen so as to ensure that individual crystals shall never stand proud of the surface of the fluid layer into which they are received.

    (d) None of said particles having a diameter greater than the thickness of said fluid layer

  48. This integer was added by the patentee during prosecution and is the basis of a specific challenge to validity under s. 72 (1) (d) of the Act. I shall deal with that aspect at a later stage. Though there was no doubt as to what this integer means, there was some debate as to the purpose of this limitation and it will be convenient to record my finding on that at this juncture.

  49. On the basis of my earlier findings on construction, if an open cell foam is to result from the method claimed, inevitably the crystals used must be of a less diameter than that of the fluid layer. If that condition were not met, they would protrude from the surface – and as Nagor point out, cause surface-to-bottom craters in the cured foam layer. This would be inconsistent with a 'foam' as defined. Mr. Hacon however went further. He submitted that the meaning of the phrase cannot simply be merged with the requirement for complete crystal submersion in the silicone layer, as that would render it otiose. A phrase in a claim should not, as he put it, be 'airbrushed' out: Horne Engineering v Reliance Water Controls [2000] FSR 90 at 100 per PumfreyJ. following Step v Emson [1993] RPC 513:

    It must always be assumed that claims are in the form they are for good reason.

    There is he submitted, a plain purpose to the phrase which is to take out of the scope of the claim, craters which in the cured product, owe their origin to 'jumbo' or outsize crystals. In other words, the overall contribution of this integer is to guarantee an open cell structure by excluding a potential source of irregularity. I consider this submission to be well founded.

    (e) Plurality of sizes thereby to increase the packing ratio

  50. I have already noted that neither the crystal size range nor the packing ratio are defined with particularity. Furthermore, there is no requirement that the size distribution ratio should be chosen such that the packing ratio is mathematically maximised. In so far as this phrase was still in issue at the end of the trial I would record that I agree with Prof Roberts' technical assessment of the integer when he said:

    It is plain that the patent envisages the use of a range of crystal sizes which is greater than that provided by a single grade.

    (f) 'Interconnecting interstitial cavities': 'Interstitial'

  51. The adjective 'interstitial' is to be found nowhere in the specification but in claim 1. The normal sense of 'interstitial' is 'a small space between things in a larger body' but in the context of an open cell foam (which is nothing but small spaces between spaces), the phrase struck me when I first read it, as being otiose. Moreover, since there is even no contextual striking point in the body of the Patent for the use of this word, its presence appears something of a mystery. I would add that there was no such problem concerning 'interconnecting cavities'.

  52. Though 'interstitial' is a term of art in metallurgy and crystallography, neither of the experts could ascribe any concrete meaning to the word. Prof Williams said [D2, page 258]:

    .... I have no idea why the patentee used this word 'interstitial'. I found it utterly confusing in this patent.

    Prof Roberts was of the view in his Report [ para 51] that the phrase was intended to mean 'small cavities between large cavities'. In cross-examination, when chased by Mr. Hacon as to whether the phrase had any technical meaning at all, he changed his position somewhat, believing that it might be a hole between cavities: Day 1 page 117-120. I recollect at the time gaining the sure impression that Prof Roberts was simply guessing and re-reading the relevant passages of cross-examination in the transcript, rekindled that impression. In truth Prof Roberts was I think, as puzzled as Prof Williams as to whether this limitation had technical significance at all. I hold that neither expert could throw any light upon any technical meaning which could be ascribed to this limitation in claim 1. Counsels' submissions on the topic were brief and again, I am unpersuaded by either of them that in truth, the word has any functional significance. It could either be the draftsman's licence or his error.

  53. The difficulty facing the court is that as noted in paragraph 49, in approaching construction, one cannot just 'airbrush' an integer out of a claim; the assumption is that however arcane its significance, it is there for a purpose. In this instance however, I am unable to make any finding on the evidence or in the light of counsel's argument or as a result of my own thinking, as to a sensible meaning for this adjective in the above-captioned phrase. I reluctantly conclude that the integer makes no sensible contribution to the claim either positive or negative, and I shall henceforth have to ignore it.

    (g) Maximum number of interconnecting interstitial cavities for tissue ingrowth

  54. Ignoring the word 'interstitial' for the reasons given, and omitting for the moment the phrase 'for tissue ingrowth', my view of the proper meaning of this phrase has actually been articulated by Prof Roberts: Report, para 54. I shall borrow his wording. He said:

    I do not think that 'maximum' can be quantified in terms of a percentage figure, but rather as a relative expression .... the inventor simply means that the use of a plurality of crystal sizes will increase the packing ratio and lead to the interconnecting .... cavities which are a consequence of that particular packing ratio resulting from the use of that plurality of crystal sizes.

    In my judgment, the latter part of claim 1, that is integers (e), (f) and (g), stand together, being interdependent. They arise only as a result of the choice of a crystalline material which includes 'particles having a [unspecified] plurality of sizes'.

  55. 'Ingrowth' in the phrase 'for tissue ingrowth' is the in vivo consequence of the structure of the open cell structure of the silicone foam. The tissue fibers must be able to grow into the surface layer of the cells and via those cells, into cells situate further from those surface cells. I would add that it is a term which occurs in a number of the articles put to the experts in cross-examination and that it occurs in both the prior art citations relied upon by Nagor. In these cases it is used in the general sense of permitting tissue to follow and become associated with and into the contours and geometry of the surface upon which it is growing.

  56. Overall, claim 1 is a method claim and in the view I take as to construction, all its integers are interrelated. They are all intended to secure the making of a silicone foam (as defined) as a consequence of the crystalline material becoming embedded under the uncured silicone layer when it is in a fluid state. In relation to the next topic, infringement, it is therefore not surprising that the main issue was whether or not the NAGOTEX product had a silicone 'foam' covering in the sense called for by the Patent.



  57. In most cases where patent infringement is the issue, consideration is given to the so-called 'Protocol questions' that is, to the question of 'variants' to a particular word or phrase: see Catnic v Hill & Smith [1982] RPC 183 and Improver Corp v Remington Consumer Products [1990] FSR 181 at 192. Although mention was made of both these authorities in argument, no significant question actually arose which required any detailed consideration of their application to the facts. I need not therefore devote time to the principles involved, which are in any event, settled law.

  58. Under this head, I would however mention that in my assessment of the facts I have been mindful of the following points of law:

    1. The fact that a defendant uses an invention inefficiently is not a defence to infringement: Union Carbide v BP [1999] RPC 409.

    2. There is no shifting onus, the burden of proving infringement to the usual civil standard remains with the claimant: see per Stuart-Smith LJ in ICI v Montedison [1995] RPC 449 at 473.

    3. Since the dispute on infringement centred largely on the interpretation of the parties' SEM photographs, it is particularly appropriate that I quote the following salutary observations of Lord Reid in van der Lely v Bamfords Ltd [1963] RPC 61 at 71, though the authority was not in fact cited.

      Lawyers are expected to be experts in the English language but we are not experts in the reading or interpretation of photographs. The question is what the eye of the man with the appropriate engineering skill and experience would see in a photograph, and that appears to me to be a matter for evidence. Where the evidence is contradictory it is for the judge to decide. But the judge ought not in my opinion, to attempt to read or construe the photograph himself; he looks at the photograph in determining which of the explanations given by the witnesses appears to be the most worthy of acceptance.

      The photograph must be looked at through the eyes of the typical addressee of the .... specification – the kind of person who would be expected to make a machine of this kind ....


  59. Nagor have served a process description from which it appears that Nagor manufacture and sell two NAGOTEX products, one in which the outer shell is made from dimethyl silicone and the other Room Temperature Vulcanised ("RTV") silicone. The processes differ in detail but seem to me to be fundamentally the same. I was also provided with a confidential video recording of the defendants' process together with a transcript of the commentary thereto. I viewed the video in advance of the trial. Both parties made a number of SEM photographs of the NAGOTEX materials. At trial, the infringement issue was largely concerned with a lengthy examination of these photographs, enlarged and annotated copies of which became available during cross-examination. These enlarged photographs were most helpful.

  60. Turning first to Nagor's process description, I shall merely pick out a few topics from the twelve page document. The NAGOTEX product is broadly made by the washout technique using salt as the crystalline material. Prior to being sprayed with salt crystals

    .... the outer layer [of the future implant] in a tacky condition. At this stage some degree of solvent evaporation has occurred so that the silicone of the outer layer no longer flows .... the outer layer remains sufficiently soft so that salt crystals sprayed onto it .... can form craters in the layer in which the crystals are retained.

    The salt crystals are sprayed evenly onto the top half of the future implant.

    About 98% of the salt crystals used have a diameter smaller than 1mm but larger than 0.125mm.

    This fact was established by random mesh tests. The results of the tests are given (e.g. 0.14g out of 100g of salt crystals had a diameter of bigger than 1 mm down to the 1.51g which had a diameter smaller than 0.125 mm). Some salt crystals adhere to the shell surface only and some bounce off leaving in some cases, indentations. The description asserts that the crystals which do not bounce off sit proud of the tacky silicone and that they do not become completely submerged in it. The resulting product is cured and the salt is dissolved out in a bath of warm water leaving 'a single layer of craters'.

  61. The salt used by Nagor, to take the words of claim 1, is in my judgment clearly a 'finely divided crystalline material' comprising a plurality of particles of varying diameter'. But if Nagor's description is correct, their silicone surface is not a 'fluid layer' within the claim and thus the resulting surface of the implant should not be a foam as claimed.

  62. From the start, the central (on one view, only) issue on infringement was thus whether the NAGOTEX product had as a surface covering, a foam within claim 1: see paras 37-43 above. The implant has a rough feel to its surface but the actual structure of the surface covering is invisible to the naked eye. Hence the need for both parties to produce the SEM photographs. It is difficult adequately to describe the appearance of the surface as captured in the claimants' sixteen SEM photographs. They differ, but all give the initial visual impression of a lunar surface, craggy, pitted and cratered in varying degree. All these SEMs show constellations of craters and some (but not all) appear to show deep surface craters. Others seem to show occasional cavities, and pockets immediately below the cratered surface. Occasionally, what may be an interconnection between craters is visible.

  63. Happily, this case contained no evidence of statistical analysis. Nonetheless, I was (and remained) concerned from the outset as to how representative of the whole the claimants' SEM photographs really are. Though Prof Roberts' Exhibit ACR 7 contained sixteen SEM photographs, he only gave evidence on ten of these. Indeed, several of the photographs in this exhibit (SEM 1 and 2 for example) upon which he offered no comment were, as the Professor agreed, devoid entirely of features of the kind which he found to be of relevance in the photographs upon which he did give evidence: D2, p. 170. Yet he says:

    As far as I am aware, there is no reason to suspect that the results are not representative of the whole sample.

    Presumably then the photographs upon which he led no evidence are just as representative as those upon which evidence was led. For the defendants, after criticising the claimants for snapping rather than cutting their samples in order to obtain sections to photograph (see below), Prof Williams said that for that reason,

    That cross-section may not be representative of the material as a whole.

    Having earlier said:

    .... a sharp incision is likely to produce a more representative cross-section and one that is less susceptible to artefacts.

    Overall and on this same question, I am also concerned that I am unaware of how many SEM photographs either side took in order to obtain the photographs which were finally tendered. It will be recalled that earlier in this judgment, what I called 'patchy' foam is not contemplated by claim 1; the foam must be of substantially open-cell structure throughout the operative area: see para 43. Areas having a surface structure corresponding to the sort of cross-section which is to be seen in SEM 1 and SEM 2 photographs would therefore make the covering 'patchy' overall and thus without the claim.

  64. In fact, McGhan have recognised their difficulty. They have had to invoke Union Carbide v BP (supra, para 58) to justify the proposition that a foam which would be unlikely to promote efficient tissue ingrowth or capture, was still within the claim. Their submission was that the invention had been used but, tellingly, not as efficiently as it might have been. I would add that there was no evidence that the NAGOTEX product was in any way unsatisfactory in use.

  65. I am not satisfied that McGhan have discharged the burden of showing that the SEM photographs upon which they rely are representative of the entire surface of the alleged infringement. I shall next turn to the question of the interpretation of the SEM photographs themselves.

  66. The basic position of the parties on the question of interpretation of the SEM photographs is as follows. McGhan assert through Prof Roberts that the NAGOTEX product has an outer layer replete with closely packed interconnected cavities of varying size below the surface and that these are due to a plurality of particle sizes of the salt used. This is denied by Nagor who by Prof Williams' evidence challenge Prof Roberts' conclusion on two bases. First, they challenge the propriety of the technique used for preparing his samples for SEM analysis – which it will be recalled, was left by Prof Roberts for others to see to. They also challenge Prof Roberts' interpretation of the photographs. The evidence on these topics is lengthy and difficult to epitomise.

  67. First, as to technique, McGhan's sample preparation was criticised on three main bases. In order for sample cross-sections to be made a specimen had first to be immersed in liquid nitrogen. Thereafter McGhan's samples were snapped rather than being cut with a scalpel and according to Prof Williams, this resulted in a line of fracture representing the line of least resistance.

    This is important in a material that has cavities since the path of the crack, and hence the cross-section revealed and studied, will be determined by the geometry of the cavities. In other words, this method selects a cross-section that has more and / or larger cavities.

    On the other hand,

    When a sample is cut using the method the defendants use, the ..cross-section depends solely upon the position of the blade. Assuming the positioning of the cut is largely arbitrary, the cross-section revealed can be regarded to be representative of all sections through the material.

  68. The other criticisms related to the angle at which the SEMs were taken and to the level of magnification used, thus, so it was said, giving a false three-dimensional impression.

  69. Needless to say, the experts were cross-examined on these topics and both adhered to their original positions. I regard the first criticism, snapping versus cutting, if proved, to have substance. In his cross-examination, Prof Williams demonstrated to my satisfaction a conviction on this issue, born of personal experience with other materials. I therefore prefer his evidence on this point. In my judgment Nagors' first criticism is valid.

  70. The experts' cross-examinations on the SEM photographs was lengthy and detailed. A good deal of time was spent on the possible origin of features such as deep craters and holes which are indeed visible in some of McGhan's photographs. The case put to Prof Roberts was that such deep craters might be due to the presence of dissolved but once protuberant crystals. He refused to accept this possibility relying on each occasion on 'his interpretation' of what he saw. The following is I hope, a fair example of the debate. The Professor was being asked questions about SEM 5 (D 2, p 187):


    What tells you that that must be the very edge of the cavity and marks the point where the crystal ended?


    It is my interpretation that that is the fracture line and that crystal was embedded in that area, in that plane.


    But you cannot point to any basis for that interpretation?


    It is just my interpretation

    Similar sequences can be exhibited from the cross-examination of Prof Williams. The high water mark of McGhan's case was perhaps this (D2, p. 337):


    Would you accept that there is evidence here of cavities below that surface?


    No I would not


    In fact there is no way you say, of telling ?


    You are asking me for evidence. I see no evidence.


    I suggest that these SEMs show evidence of interconnections between cavities.


    I think we have said that there was one interconnection and I have said that in other cases it was possible but I do not see any evidence of substantial connection between craters or any other features.

  71. On the face of it, there was an uncompromising entrenchment of positions between the experts, both adamantly sticking to their positions. I must however record yet again that in this conflict I felt that Prof Williams held the higher ground not just because of his confidence, experience or demeanour but because he was able to furnish plausible bases for many of his interpretations and also, that at times, he was prepared to make admissions. Having reviewed all this evidence, I look at the SEM photographs, bearing in mind the requirement that there should be a continuous open cell structure. I am not persuaded that the identification of one and possibly a few other interconnecting cavities is enough to enable the claimants to succeed. I have come to the conclusion that what one sees is simply not a foam within claim 1. Similarly, on my construction of the phrase, there was never present in Nagor's process a 'fluid layer' within the claim. Finally, I have come to the conclusion independently of the concern earlier stated, that the SEM photographs upon which Prof Roberts gave evidence may not represent a fair picture of the cross-section of NAGOTEX overall or that on the 'snapping versus slicing' issue, cutting is more likely to yield a useful dividend.

  72. Nagor's process uses salt as the crystalline material, the crystals of which span a spectrum of sizes. Prof. Williams said that crystals having a plurality of sizes necessarily had the effect of increasing the packing ratio but since Nagor's salt is not 'embedded', this is irrelevant to the point. I need not consider the remaining integers of claim 1 seriatim, since in the end, they all relate back to whether or not a foam which is within the claim and arises by embedding, is present in the NAGOTEX product. In the result, I have come to the conclusion that McGhan have not proved their case on infringement.



  73. By section 72(1)(a) of the Act, a patent may be revoked if 'the invention is not a patentable invention'. Patentable inventions are defined by section 1(1), sub-sections (a) and (b) of which are relevant to the counterclaim and provide:


    that the invention must be new, and


    that the invention must involve an inventive step.

    These conditions are commonly spoken of in the negative, in terms of 'lack of novelty' and 'obviousness'. Both are in issue in this case. In addition, the Patent is attacked under section 72(1)(d) in that the matter disclosed in the specification of the patent extends beyond that disclosed in the application for the patent as filed. This objection is commonly referred to as 'added matter'. The onus is of course on Nagor to make good these objections.

  74. In relation to the alleged lack of novelty, the attack is based on a single instance of an alleged prior use of the method of claim 1 before the priority date at a factory in Minnesota, USA and by the alleged prior oral disclosure of that process by a worker at that factory. In relation to obviousness, in addition to this prior use and prior disclosure, Nagor rely upon two prior publications:


    A post-conference article by Feldman and Estridge entitled Factors affecting soft tissue ingrowth into Porous Implants. This was published in the USA in 1984 and will be referred to as 'Feldman & Estridge', and


    US Patent no 3 700 380 ("Kitrilakis"). This patent was published in 1972.


    (a) The Law

  75. There was no dispute as to the principles of law applicable in deciding whether a claim is anticipated by a prior disclosure. This being the case, I need do no more than indicate in summary my understanding of the matter. The principles are set out in the now classic judgment of Sachs LJ in General Tire v Firestone Tyre [1972] RPC 457 at pp 485-486 and in the earlier authorities referred to therein. There must be clear and unambiguous directions in the prior disclosure to do or make something which falls within the claim under attack. If however the prior disclosure consists of a direction which is capable of being carried out in a way which would fall within the claim under attack but which would be at least as likely to be carried out in a manner which did not do so, the patentee's claim will not have been anticipated.

  76. In this case, the prior disclosures which were pleaded included an alleged prior use and a prior oral disclosure relating to that use. In such cases (in contrast to the more common situation of prior disclosure in a document), there is further guidance as to the correct approach. First, it must be established that the act relied on was an enabling disclosure of the invention; that is, that it enables a person skilled in the art to perform the method of the claim under attack: Lux v Pike [1993] RPC 107 at 133-134. It must further be established that there was "no bar of confidentiality restricting the use or dissemination" of the relevant information: Quantel v Spaceward [1990] RPC 83 at 127. Put another way, the relevant information must have been "made available to at least one member of the public who was free in law and equity to use it": PLG v Ardon [1993] FSR 197 at 225-226 and Lux (supra) at 132. In this case, since Nagor's witness to the prior use (and disclosure) was an employee of a third party at the relevant time, Mr. Tappin also drew my attention to the judgment of the Court of Appeal in Lancashire Fires v Lyons [1996] FSR 629 at 665-675.

    (b) The Facts

  77. The particulars of this pleading first allege that prior to the priority date, a company in Roseville, Minnesota USA, Bio-Manufacturing Inc used a process to manufacture silicone breast implants which fell within claim 1 of the Patent. The pleading and the witness statement of a Mr. Kwao Amegashie (who was at the time an employee of Bio-Engineering Inc but who is now a US lawyer) furnish details of the process alleged to have been used. In brief, a top layer of silicone was laid on a silicone 'shell' and then dried until it became 'tacky'. This artefact was then immersed in a container which contained table salt from which the 'bigger grains' had been removed using a steel strainer. The salt crystals were apparently pushed (or 'pounded') with a paint brush into the tacky surface. The shell was taken from the container, cured and the adhering salt dissolved out. The result, so Nagor alleged, was an article which fell within claim 1 of the Patent- on their interpretation of it. Mr. Amegashie also gave evidence to the effect that before the priority date he personally disclosed his employer's method of manufacture to persons outside the company, such as to friends, to individuals who made deliveries to the factory and to visitors. Needless to say, all this was the subject of cross-examination by Mr. Tappin.

  78. In giving evidence, Mr. Amegashie was under a considerable handicap as the most important events about which he was being asked detailed questions, took place principally during 1988. I think the witness did his best to assist the court. Save that it is inevitable that personal recollection of detail becomes hazy after that length of time, I have no particular comment to make about Mr. Amegashie's reliability as a witness; I believe that the events about which he gave evidence did indeed take place at approximately the time put forward. But the recollection of events and roughly when they happened is not enough in my judgment to make good this objection; the devil is in the detail.

  79. First, no contemporaneous documentation or sample of the implant made by Bio-Manufacturing was produced in evidence. Secondly, as already noted, one cannot tell by either visual inspection or feel anything relevant to the structure of the surface of the finished implant. The effect of pounding salt onto or into the 'tacky' surface of the artefact will depend upon how 'tacky' the surface is and how vigorous the 'pounding'.

  80. The evidence of Mr. Amegashie was that from time to time prior to the priority date, a variety of visitors came to the factory at Roseville. In his words, a number of visitors were told " This is what we make, this is where it is made and this is the process". Even assuming that these visitors were notional skilled workers in the field, that evidence is still not enough for an enabling disclosure to have taken place. I very much doubt for example whether a visitor would have been able to observe the extent (if any) to which the salt crystals penetrated into this 'tacky' silicone layer. Indeed I very much doubt whether the salt crystals were 'embedded' so as to create the foam of claim 1 after washout since to do so requires an appreciation in the mind of the observer that mere surface adhesion is not enough. At best the evidence shows that what was seen could have been any one of the following:

    1. mere surface adhesion of the salt crystals and subsequent cratering of the cured surface after washout, or

    2. some surface adhesion together with some penetration into the tacky surface to an unknown degree yielding possibly some sub-surface cells after washout, or

    3. full immersion of the salt under the tacky surface of the silicone as (in my finding) is required of the method of claim 1 of the Patent.

    As noted, I regard the latter as being most unlikely to have been observed. On authority, the co-existence of these three possibilities is insufficient to justify a finding of lack of novelty.

  81. Mr. Tappin also drew my attention to the question of the absence of evidence as to particle size in relation to the table salt which was used. There is evidence that table salt does not contain crystals of one particular size so I doubt whether that point is a good one; after all, the Patent says 'crystalline material including particles of varying diameter'. Nonetheless, for the reasons stated, in my judgment this was not an enabling disclosure to the factory visitors. Furthermore, I am unconvinced that Mr. Amegashie's memory as to dates is sufficiently reliable.

  82. There are in fact further aspects to this site disclosure which reinforce this finding. First, at the factory premises at least, there is no evidence that any oral disclosure took place other than in circumstances where a bond of confidence would be implied. Mr. Amegashie said that he himself would not have been free to disclose the process to a competitor: D3, p 356. I also bear in mind that:

    1. Mr. Amegashie was not aware whether the visitors to the factory with whom he spoke were themselves under an obligation of confidence express or implied, and

    2. the process used was unusual in that it had been specially developed in-house by Bio-Manufacturing for manufacturing its only product.

  83. Another incidence of alleged prior disclosure was relied on: that of Mr. Amegashie's himself to his friends outside the factory. It seems that reject breast implants were much in demand in Roseville, Minnesota before the priority date:

    The company has no problems with us taking it [i.e. reject breast implants] home, giving it to friends or whatever. So when friends find out that I am working with this company, the first thing they want is a sample and I give it to them. Generally that leads to a description of the process. When delivery men come in...and see what we are making they of course want samples. It generally leads to conversation as to "How is this made?"....

    No question of confidentiality was alleged to arise among Mr. Amegashie's friends in relation to these disclosures. I was puzzled nevertheless as to why reject breast implants should have become such recherché items in Roseville and was prompted to ask Mr. Amegashie about this at the conclusion of the cross-examination. The following sequence ensued:

    The Court:

    These reject implants that you, as I understand it, say were given to friends?



    The Court:

    Why did they want them?


    It is a male thing. It is usually the males; they want samples. People use them as paperweights and others for various reasons. I cannot speculate.

    It is in my judgment, in the highest degree improbable that ordinary folk in Roseville, Minnesota on being handed a reject breast implant by Mr. Amegashie as a present for use as a paperweight, would be remotely interested in the details of the process whereby it was manufactured.

  84. In my judgment, the objection of lack of novelty fails.

  85. The Roseville disclosure is additionally relied upon in relation to the obviousness objection. However, in the light of my factual findings on this incident, particularly on the questions of dates and confidentiality, I do not consider that Nagor can profitably avail themselves of it in attacking the Patent on the additional ground of obviousness.


    (a) The Law

  86. As with lack of novelty, the parties appeared to be on common ground with regard to the proper approach to obviousness. I was reminded of the danger of the ex post facto analysis of inventions and of the unfairness to inventors which can thereby arise when inventive step falls to be assessed: British Westinghouse v Braulik (1910) 27 RPC 209 at 230 per Fletcher Moulton LJ. Similarly, Lord Diplock's criticism of the artificiality of 'step by step' cross-examination in relation to obviousness was raised by Mr. Tappin: Technograph Printed Circuits Ltd v Mills & Rockley Ltd [1972] RPC 346 at 362. It was common ground that this question should be assessed in the fourfold structured manner proposed by Oliver LJ in Windsurfing Int'l v Tabur Marine [1985] RPC 59 at 73 which for convenience may be summarised thus:

    1. Identify the inventive concept embodied in the patent in suit

    2. Assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and impute to him what was, at that date, the common general knowledge of the art

    3. identify what if any, differences exist between the matter cited as being 'known or used' and the alleged invention, and

    4. Determine whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention.

    A little earlier, Oliver LJ said (p 72):

    What has to be determined is whether what is now claimed as inventive would have been obvious, not whether it would have appeared commercially worthwhile to exploit it.

    (b) The Facts

  87. The first two stages of the Windsurfing enquiry generate answers which are of equal relevance to all the cited prior art and I shall deal with them now.

  88. First, Mr. Tappin helpfully provided an epitome of the inventive concept in opening, warning me that in so doing I must not regard it as a short cut to the claims. I have borne that admonition in mind in what follows. The inventive concept, he says, is:

    Making a silicone foam covering using the washout technique in which crystals of a plurality of sizes are embedded into the silicone.

    Mr. Tappin added the following gloss, no doubt with an eye to limiting the purpose of these foams:

    Together with the use of the plurality of crystal sizes having the effect of increasing the packing ratio so as to produce a foam having the maximum number of interconnecting interstitial cavities for tissue ingrowth.

    Since the words underlined are I believe, the key to the invention, I doubt whether this gloss adds anything significant. On this issue, Mr. Hacon reminded me that the method claimed is not limited to making breast implants; it is a method for making a foam covering for any article. Indeed Mr. Hacon stated that the method would be apt to cover articles which would be functionally useless as breast implants. The latter may be true, but in spite of the general nature of the preamble to the claim, the disclosure is plainly limited to the provision of a surface for implants 'for implantation in the human body', as Mr. Tappin suggests.

  89. I have already endeavoured to identify the common general knowledge of the art which I believe would be possessed by the skilled worker in the art: see paras 26-32 above. I shall next move to the two prior publications relied on by Nagor.


    (a) Feldman & Estridge (1984): 'Factors affecting soft tissue ingrowth into porous implants.'

  90. Mr. Tappin, referring to the third item in the factual analysis of Windsurfing, observed with some satisfaction that since over three-quarters of claim 1 of the Patent was missing from this citation, this was hardly a promising start for an attack on obviousness. Whilst the missing proportion may have been correctly stated, I do not believe that the issue can be disposed of so easily.

  91. Feldman & Estridge is evidently a précis of an address given by these gentlemen to a meeting for the Society for Biomaterials in May 1984 and is less than a page of A4 in length. Interestingly, Prof Williams actually attended the giving of this paper; it seemed to have had no enlightening impact on him at the time. In effect, it is a mini-review of earlier studies on 'porous' implants', the authors' understanding of the term including fabric and sintered materials as well as those having measurable pores. The authors say:

    Although porous soft tissue implants are very common, there is a dearth of data relating to the effect of implant porosity on tissue response.

    The authors state that there are many materials and techniques for manufacturing porous implants including


    Manufacturing a polymeric implant with salt crystals on the surface, and then dissolving away the salt




    Using a foaming agent during the processing. This causes bubbles to form and leaves pores on the surface of a ceramic as it hardens.

    [emphasis added]

    Some six 'unifying concepts' are then set out, the second of which was cross-examined upon.


    Large pores or interconnecting pores do not fill completely with tissue and can lead to infection.

    No mention is made of silicones (or of polyurethane) as material with which to make porous implants. However, having regard to the state of the common general knowledge, I doubt if this is of significance to the present enquiry. No mention is made either of breast implants but in the light of the preamble to claim 1, this is also unimportant.

  92. This paper is deemed to be read by the skilled man possessed of the common general knowledge, looking for a method of creating an implant surface having an open cell structure in silicone material. In the light of the evidence, it seems to me that his first port of call would be to think of using a blowing agent and catalyst for this purpose. He would read in this paper that a blowing agent was indeed being recommended to make a ceramic implant. Having regard however to the universal use of blowing agents to make polymeric foams, I doubt if this would have deterred him from trying. I have already referred to the silence of the patentee as to what the structural problem was with 'blown' silicone foams and what were his criteria of 'suitability'. That being so, one might suppose that the skilled man's research could stop at that juncture with a 'blown' silicone. If, like the patentee, he was for some reason dissatisfied with the result, he might indeed turn to Feldman & Estridge's fourth option and try to create a porous implant by using the salt washout technique with a polymer by putting salt on the surface during manufacture. But that means what it says, on the surface', and the consequence would be to create a pitted or cratered surface which would not be within the claim. Furthermore, I consider that the addressee would probably heed the authors' warning about 'large pores and interconnecting tissue', since, as Prof Williams said in cross-examination, large pores tend to fill with tissue exudate which is a useful medium within which bacteria can multiply. He would thus not be tempted to try to create too extensive or ample a foam.

  93. When I first read this citation I felt that it was the sort of document with which a party attacking the Patent on the ground of lack of inventive step could make relevant submissions only with the ample benefit of hindsight. Having re-read it in the light of the evidence and counsels' submissions, I am still of that view. Until the skilled reader is made aware of the method of claim 1, this is not really a pointer in its direction. In my judgment, Nagor have not made good their obviousness attack on the basis of Feldman & Elstridge.

    (b) U.S Patent no 3,700,380 (Kitrilakis-1972)

  94. By contrast, I believe that this citation would certainly have been of interest to a skilled man at the priority date of the Patent who is concerned with migration or hard encapsulation and wishes to make a more stable porous covering for a human prosthesis. The patent is entitled 'Surface or lining compatible with blood or other tissue' and is basically concerned with a surface or lining for use within the human body containing 'microcavities' or 'pockets'. The process proposed by Kitrilakis for making such devices is the washout technique wherein salt crystals are embedded in a 'tacky' polymer surface, the surface is cured and the salt is dissolved out with water.

  95. Column 3, lines 16-29 of Kitrilakis read as follows:

    .... there is provided a lining or surface containing a plurality of microcavities or pockets which is compatible with blood and living tissue and forms a tenacious base or anchor for pseudointimal growth and tissue ingrowth and yet provide normal metabolic processes to the cells. The microcavities are formed by providing particles or fibers in the base material and thereafter removing the particles or fibers, leaving microcavities.

    It is an object of this invention to provide a surface which forms a thin substrate capable of tenacious anchoring of subsequent cell deposition and ingrowth.

    A little lower in the same column, starting at line 53, Kitrilakis describes how the surface is formed by

    .... applying fibrous or particulate or granular material to the surface which is to contain the microcavities while the surface is soft, causing the surface to set up, cure or harden with the fibers or granules partially or wholly incorporated therein and thereafter using a solvent which dissolves the fibers or particles leaving a surface which contains microcavities at the location where the fibers or particles were embedded. The size and shape of the microcavities can be controlled by the selection of the size and shape of the fibers, particles or granules. The density or surface distribution of these pores or pockets can be controlled in the manufacturing process by regulating the particle distribution.

    The only manufacturing process described is in fact the washout technique. Use as a substrate on inter alia silicon rubber (i.e. silicone) and polyurethane for this purpose is indicated (Col 4 line 27) and further down, at lines 48-50, the patent describes how the 'particles or granules' may be

    salt crystals of a selected size or shape distribution.

    The passage continues:

    The embedded particles or granules may be dissolved with distilled water leaving a plurality of irregularly shaped microcavities.

    [my emphasis]

    The surface upon which the fibers etc are to be 'embedded' is described as being 'tacky': Col 4, line 11.

  96. The narrative continues in Col 5, lines 28-33, as follows:

    Thus it is seen that there has been provided an improved surface or lining and method of forming same with microcavities which are controllably spaced and interconnected ....

    The depth and size of the microcavities can be controlled by the fiber length and size or the particle size and shape. The openings are of uniform density but may be randomly angled with some holes interconnecting below the surface.

  97. Thus far, as Mr. Tappin mentioned on several occasions, the application of Kitrilakis' invention was primarily for making improved blood carrying devices and percutaneous leads. However, in Col.6 at line 17, the inventor reverts to use of his proposals for promoting satisfactory tissue ingrowth on implanted prostheses.

    Another application of the microcavity surface of the present invention, not shown, is as an external lining on the surface of implanted prostheses which encourages the formation of a thin adherent tissue envelope Although the tissue forming this envelope has somewhat different characteristics than skin, and subcutaneous tissue, it grows into the lining in essentially the same manner. The envelope prevents damage to surrounding organs and tissue and substantially lowers the risk of infection at the prosthesis...Such tissue encapsulation also improves fixation and support of the prosthesis and protects the same against damage.

  98. In the above passages quoted from Kitrilakis, the words and phrases in italics are my own and those underlined are words and phrases which occur in the Patent to describe the method claimed and the product made thereby. It will at once be noted that the key word which is in the Patent and not in Kitrilakis, is the word 'foam'. I would add that there was no question that the reference to the second application of Kitrilakis' proposal included use in breast implants or that 'silicon rubber' was not a silicone or that the word 'encapsulation' was the same thing as 'hard encapsulation'.

  99. Mr. Tappin, pointing to the third Windsurfing question, sought to distinguish the disclosure of Kitrilakis on two bases. First, by reference to McGhan's definition of 'foam' and secondly by reference to Kitrilakis' use of the adjective 'thin' when describing the textured layer in this citation. In fact, his argument was that the two were interrelated in a way relevant to the present enquiry. Prof Williams was cross-examined at length upon Kitrilakis, the cross-examination concluding as follows (D 2, page 283-284):


    I am going to suggest to you that this is all hindsight and that if you were standing back in 1988 with no knowledge of the McGhan patent and you were given Kitrilakis, -the ordinary skilled person would you not think-that you could adapt Kitrilakis to make a foam?


    I believe they would.


    Would you agree this? There is nothing in Kitrilakis to suggest that it would be advantageous to use foam?


    Yes I agree that. There is nothing to say that.

    The Court

    Mr. Tappin, .... Are you using [the word 'foam'] in the sense that it is being used in the Patent?

    Mr. Tappin

    Yes, and in the sense in which I believe Prof Williams is using it that is to say, open cell construction with open cavities. I do not think we have been at cross-purposes have we Prof Williams?


    I do not think so.

  100. I have no doubt that the skilled worker at the priority date reading Kitrilakis and looking for an alternative surface for a breast implant which did not suffer from either migration, hard encapsulation or chemical degradation, would be likely to carry out the washout technique in Kitrilakis using silicone as the implant material with a high expectation of success. He would think: " This gives me what I want" and would make an implant accordingly and try it out. There was no evidence that the Kitrilakis prostheses were unsuitable in use. I further believe that since the implant surface which Kitrilakis proposes would appear to be very similar to that which is alleged to infringe, it would I believe be likely to be satisfactory in use-as indeed is the NAGOTEX product.

  101. In coming to this conclusion, I have used the definition of the word 'foam' given in the Patent. I have construed the word 'embedded' in the sense for which McGhan contend so as to achieve such a 'foam' viz so that all the particles are driven below the surface of the 'fluid layer of uncured silicone' that is, as Mr. Tappin put it in his cross-examination of Prof Williams , 'buried beneath the surface'. On the basis that the sort of implant surface proposed by carrying out Kitrilakis' method would prove to be satisfactory in use, I do not see why the skilled worker would wish or need further to modify Kitrilakis' method to ensure a total embedding of particles, thus making a foam within the meaning of claim 1. The objection to validity based on obviousness in the light of the Kitrilakis disclosure accordingly fails. I should record that I have not acceded to any suggestion that there was a 'long felt want' in this case.

  102. I would however add a rider to this finding. If I should be wrong on the issue of construction ( i.e. of the words 'embed' and thus, 'foam covering'), and that Nagor's submission as to the proper meaning of the term is correct viz that the crystalline material may be 'wholly or partially embedded' in the fluid silicone layer, then it would seem that the Patent is invalid on this ground in the light of Kitrilakis. First, 'thin', the word used by Kitrilakis to describe the surface layer which he proposes, is of course a relative word. The Patent provides the following limited guidance in this respect:

    A depth of no more than about 1 mm of such texture, is of consequence. Much deeper cellular construction can itself lead to problems of tissue growth.

    [my emphasis]

    Furthermore, the thickness of the textured layer is not as such a feature of any of the claims. I have found no evidence directed to the precise point but in my judgment, the foam layer made by the method of claim 1 must also be 'thin' in relation to the silicone substrate if only to avoid the problems of tissue growth associated with 'deeper cellular construction': see para 11 above. Kitrilakis also speaks of pores, pockets and mirco-cavities in such a surface which interconnect as a result of using the washout technique to create them. There are also going to be microcavities on the surface itself. In addition, these features can be controlled in size and density by appropriate choice of particle (e.g. salt crystal) size. Silicone is proposed by Kitrilakis as an implant material and having regard to the common general knowledge, would in any event be the material of choice. The adoption of this teaching, so Kitrilakis says, leads to certain desirable physiological consequences in the end product. Were Nagor's construction of the claim to be chosen, Kitrilakis' disclosure would be an obvious starting point on the part of the addressee to use the alternatives he proposes. In fact Nagor's proposal becomes only trivially distinguishable from the disclosure of the Patent which in my judgment, would be invalid.


  103. The parties were agreed upon the principles of law to be applied. These are to be found in the judgment of Aldous J in Bonzel (T) v Intervention Ltd (No.3) [1991] RPC 553 at 574, the relevant part of which I shall quote:

    The decision as to whether there was an extension of disclosure must be made on a comparison of the two documents read through the eyes of a skilled addressee. The task of the court is threefold:


    To ascertain through the eyes of the skilled addressee what was disclosed, both explicitly and implicitly in the application.


    To do the same in respect of the patent as granted.


    To compare the two disclosures and decide whether any subject matter relevant to the invention has been added whether by deletion or addition. The comparison is strict in the sense that the subject matter will be added unless such matter is clearly and unambiguously disclosed in the application either explicitly or implicitly.

    The exercise again presses into service the attributes of the skilled addressee, on this occasion perhaps in addition, as 'officious bystander'.

  104. The matter which Nagor allege has been added is set out in the particulars to paragraph 2 of Nagor's particulars of objections and reads as follows:

    The specification of the Patent, and in particular claim 1, discloses that none of the particles (comprising the crystalline material to be embedded in the fluid layer) have a diameter greater than the thickness of the said fluid layer.

    That matter, say Nagor, was not disclosed in the application for the Patent as filed.

  105. It is not suggested that that this item was explicitly disclosed in the application for the Patent. McGhan argue however that the inventor had in mind crystals which as a group were wholly embedded in the fluid layer (which I have accepted) and that this 'of necessity' means that they must have a diameter less than the thickness of the fluid layer of silicone: Prof Roberts, Report I, para 80. Nagor's case was based upon their interpretation of the word 'embedded' viz that it includes crystals which may stand proud of the surface of the liquid layer of silicone. I have rejected this interpretation. In my judgment, the limitation is implicitly disclosed in the application. The requirement is, as I have found, that the crystals must under all circumstances be wholly 'embraced by the silicone' and must therefore have a lesser diameter than the thickness of the liquid layer of silicone.


  106. In the result, Nagor's silicone-textured breast implant product NAGOTEX does not infringe any claims of the Patent. I shall therefore dismiss the action. Furthermore, for the reasons stated, I shall also dismiss Nagor's counterclaim. I shall hear counsel on the appropriate form of order to be made in due course.


Catnic v Hill & Smith [1982]RPC 183; Biogen v Medeva [1997] RPC 1; Horne Engineering v Reliance Water Controls [2000] FSR 90; Step v Emson [1993] RPC 513; Improver Corp v Remington Consumer Products [1990] FSR 181; Union Carbide v BP [1999] RPC 409; ICI v Montedison [1995] RPC 449; van der Lely v Bamfords Ltd [1963] RPC 61; General Tire v Firestone Tyre [1972] RPC 457; Lux v Pike [1993] RPC 107; Quantel v Spaceward [1990] RPC 83; PLG v Ardon [1993] FSR 197; Lancashire Fires v Lyons [1996] FSR 629; British Westinghouse v Braulik (1910) 27 RPC 209; Technograph Printed Circuits Ltd v Mills & Rockley Ltd [1972] RPC 346; Windsurfing Int'l v Tabur Marine [1985] RPC 59; Bonzel (T) v Intervention Ltd (No3) [1991] RPC 553


Patents Act 1977: s. 125

Authors and other references

Feldman and Estridge, Factors affecting soft tissue ingrowth into Porous Implants.


Michael Tappin for the Claimant (instructed by Bristows)

Richard Hacon for the Defendant (instructed by Gouldens)


[a] Improver Corp v Remington Consumer Products [1990] FSR 181

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