The present decision concerns an appeal filed by the patent proprietor after the Opposition Division (OD) had revoked its patent.
The Board rejects the main request on file because it comprises undisclosed subject-matter (A 100 c)/A 123(2)). It then deals with the first auxiliary request which contains two independent claims:
1. An implant for use within a body, said implant being made of a crosslinked ultrahigh molecular weight polyethylene having a polymeric structure of less than 45% crystallinity after irradiation sterilization as measured by DSC, so as to increase the wear resistance of said implant within the body.
8. A method of producing an implant with improved wear resistance, comprising the steps of: crosslinking a polyethylene to produce a crosslinked ultrahigh molecular weight polyethylene having a polymeric structure characterized by less than 45% crystallinity after irradiation sterilization as measured by DSC, and annealing the crosslinked ultrahigh molecular weight polyethylene to preshrink and stabilize its size before making it into an implant.
The Board finds these claims to comply with the requirements of A 123(2). It then considers whether the claims, and in particular claim 8, are sufficiently disclosed.
Interpretation of Claim 8
[4.1] The process of Claim 8 comprises the step of “crosslinking a polyethylene to produce a crosslinked ultrahigh molecular weight polyethylene having a polymeric structure characterized by less than 45% crystallinity after irradiation sterilization”.
One way of achieving the desired crystallinity of less than 45% after irradiation sterilisation is to crosslink the polymer in a first step and to irradiate the crosslinked polymer in its solid state at a sterilisation dose in a second step (Claim 4 as filed). The crosslinking of the polymer in the first step is not carried out by irradiating the polymer in the solid state but by a method selected from (a) irradiation crosslinking of the polymer in the molten state, (b) photocrosslinking and (c) crosslinking with a free radical generating chemical (Claim 5 as filed). The first step reduces the crystallinity of the starting UHMWPE enough so that after sterilisation by irradiation (which inherently increases the crystallinity) the crystallinity is below 45%. This embodiment is clearly described in the application as filed, something that was not disputed by the parties.
However, the process of Claim 8 is not restricted to this embodiment, but includes the possibility that crosslinking and sterilisation by irradiation are carried out in one and the same step, namely in the solid state. In fact, both the proprietors and the [opponent] insisted that the process of Claim 8 also includes this embodiment. This implies that Claim 8 covers process variants in which a UHMWPE is sterilised by irradiation in such a way that a crosslinked polymeric structure with less than 45% crystallinity is obtained.
[4.2] Claim 8 is directed to a process which is defined by a result to be achieved, namely the provision of a crystallinity of less than 45%. Though decisions T 435/91 and T 409/91 deal with cases in which the result to be achieved is part of a product claim, the board takes the view that these decisions equally apply to process claims. This is confirmed by the statement made in T 435/91 [2.2.1, 3rd §] where it was held that
“the criteria for determining the sufficiency of the disclosure are the same for all inventions, irrespective of the way in which they are defined”.
As follows from these decisions (T 435/91 [2.2.1, § 5 and 6] and T 409/91 [3.5, § 2), in order for an invention claimed by means of a result to be achieved to be sufficiently disclosed, the available information must enable the skilled person to achieve the envisaged result over the whole ambit of the claim without undue difficulty.
As is explicitly set out in T 409/91 [3.4, penultimate paragraph], the presence of one way of carrying out the invention therefore does not automatically imply that the invention is sufficiently disclosed.
Examination of sufficiency of disclosure over the whole ambit of claim 8
[4.3.1] Based on the principles established in T 435/91 and T 409/91, it has to be analysed whether or not the specification discloses a technical concept fit for generalisation which makes available to the skilled person the host of variants encompassed by the functional definition given in Claim 8, in particular those in which the desired crystallinity is achieved via crosslinking by means of irradiation sterilisation.
[4.3.2] The opposed patent contains only one embodiment which could be considered to represent an embodiment of a process where crosslinking and sterilisation are carried out simultaneously by irradiation. This is the first experiment of Example 1 […]. In this example, a UHMWPE specimen with a crystallinity of 49.2% […] is irradiated with γ-rays at a sterilisation dose of 3.4 Mrad […]. However, the crystallinity obtained by this process variant is not within the range cited in Claim 8, but significantly above the upper limit of this range (55.8% versus less than 45%). Consequently, it is evidenced by the opposed patent itself that purely applying irradiation sterilisation to crosslink a UHMWPE as covered by Claim 8 does not suffice to obtain the desired result of Claim 8.
[4.3.3] Knowing that process variants in which crosslinking is effected solely by irradiation sterilisation do not give the crystallinity as required by Claim 8, the skilled person might try to modify these process variants such that a crystallinity as cited in Claim 8 is obtained. However, as was not disputed by the [patent proprietors], the opposed patent itself does not contain any teaching at all in this respect.
[4.3.4] It remains to be examined whether the skilled person on the basis of his common general knowledge would have been able to modify the above-discussed process variants such as to obtain the desired crystallinity. The [patent proprietors] in this respect argued that it would have been trivial to select a UHMWPE starting material that had a sufficiently low degree of crystallinity such that, even after an increase in crystallinity caused by irradiation sterilisation, the obtained values would still be below the upper limit of the crystallinity range cited in Claim 8.
The [patent proprietors] in particular referred to the UHMWPE with a crystallinity of 38% as disclosed in Table I of D10 as an example of such a starting material. However, this polyethylene represents an annealed sample […]. No information on the annealing conditions is present in D10.
Furthermore, as is apparent from a comparison of the values of the polyethylenes “as received” with the values of the annealed samples in Table I of D10, the crystallinities obtained after annealing do not correlate with the crystallinities of the polyethylenes “as received”. For example, the “as received” sample with the lowest crystallinity value (54%) in Table I does not have the lowest crystallinity value after annealing.
Starting from the [patent proprietors’] assumption, the skilled person would therefore have to take several measures in order to arrive at a process variant in which crosslinking by means of irradiation sterilisation leads to a crystallinity as required by Claim 8.
In particular, the skilled person:
- would have to realise that what needs to be done is to look for starting materials with sufficiently low crystallinity, though no guidance is present in this respect in the opposed patent;
- would have to realise on the basis of D10 that in order to obtain such a starting material, the material would have to be annealed;
- in the absence of any information available in D10 about the annealing conditions and in view of the fact that crystallinity obtained after annealing does not correlate with the initial crystallinity, would have to run a variety of annealing experiments with a variety of starting materials to find out how to obtain an annealed starting material with sufficiently low crystallinity; and
- despite the general teaching of the opposed patent to reduce crystallinity, would have to apply irradiation sterilisation, which inherently increases the crystallinity of the starting material.
In conclusion, it would only have been in deviation from and even in contradiction to the teaching of the opposed patent, and after a multiplicity of thought steps in combination with a variety of experiments, that the skilled person could have arrived at process variants in which crosslinking by irradiation sterilisation leads to a crystallinity as required by Claim 8. Therefore, what the [patent proprietors] consider “trivial” in fact amounts to nothing less than setting up a new research program which deviates or even contradicts the teaching of the opposed patent. The method referred to by the [patent proprietors] would therefore not have been at the disposal of the skilled person when simply reading the opposed patent and using his common general knowledge.
In other words, on the basis of the opposed patent and common general knowledge, the skilled person applying process variants where UHMWPE is crosslinked by means of irradiation sterilisation would not be able to obtain a crystallinity as required by Claim 8.
Consequently, Claim 8 covers process variants that are insufficiently disclosed. The invention defined by this claim therefore does not meet the requirements of A 83.
[4.5] This finding is in agreement with the general legal principle that the protection covered by a patent should correspond to the technical contribution to the art made by the disclosure of the invention described therein (T 435/91 [2.2.1, § 4] and T 409/91 [3.4-5]). This principle excludes the patent monopoly from being extended to subject-matter, such as the above-discussed process variants covered by Claim 8, which, after reading the patent specification, would not be at the disposal of the skilled person.
[4.6] The [patent proprietors] argued during oral proceedings (OPs) that the burden of proof that Claim 8 covers embodiments that do not lead to the crystallinity required by this claim was on the [opponent]. As the [opponent] had not submitted any experimental data in this respect, the [opponent’s] burden of proof had not been discharged.
The board cannot agree with this view.
Additional experimental evidence does not constitute a necessary precondition for the discharge of the burden of proof. On the contrary, any such discharge of the burden of proof can be considered to have taken place as soon as evidence is available that renders a party’s position more probable than not (see T 109/91 [2.10]).
As has been set out above and as was discussed at length during the OPs, this evidence exists in the present case in the form of the first experiment of Example 1 of the opposed patent. Furthermore, this evidence was even not disputed by the [patent proprietors]. More particularly, the [patent proprietors] did not question that using a starting material with a crystallinity above 45%, such as 49.2% in Example 1 of the opposed patent, and applying irradiation sterilisation will not lead to a crystallinity as required by Claim 8. Thus, the [patent proprietors’] argument cannot succeed.
[4.7] In summary, the first auxiliary request is not allowable in view of A 83.
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