Claim 1 of the patent as maintained by the Opposition Division read (in English translation):
Implant (6) for the inter-vertebral space (25) withA) an essentially cuboid shaped body (7) with different diameters (D1, D2) between the lateral surfaces (14, 15) as well as between an upper surface (16) and a lower surface (17); wherebyB) the lateral surfaces (14, 15) between which the smallest diameter (D1) extends are mostly parallel and flat; and withC) a device (8) for grasping by a tool (9),characterized in thatD) the implant (6) presents a chamfered lenticular profile in the longitudinal section of its largest diameter (D2); wherebyE) the upper surface (16) and the lower surface (17) between which the largest diameter (D2) extends are destined to contact an adjacent vertebral body eachF) the implant (6) has a partially rounded section perpendicular to its longitudinal axis (35); andG) the implant (6) is provided with a through hole (18) having the shape of an oblong groove with parallel walls (19,20). (my emphasis)
The opponent objected that the claim was not clear because the longitudinal axis was not defined and could be, for instance, the longitudinal axis of the backbone. Moreover, the claim did not clearly state where the section was rounded. This difficulty could not be overcome by considering the description because in column 8, lines 35 to 37 it was disclosed that there was a “rounded side … on the upper edge of the front axial end” only , whereas Figures 10 and 11 disclosed that the rounded parts extended along one or two edges, respectively.
In addition to that, it was not clear what was meant by “partially rounded section” because this wording encompassed both the embodiments according to figures 2 to 6, where all edges of the section were rounded, as well as the embodiments of figures 10 to 13, where only some of the edges were strongly rounded.
Finally, the combination of features F and G generated another lack of clarity with respect to the expressions “longitudinal axis” (Längsachse) and “oblong groove” (längliche Rille). An opening that extended parallel to the longitudinal axis contradicted the embodiments shown in the figures.
*** Translation of the German original ***
 Feature F of claim 1 requires the implant to have “a partially rounded section perpendicular to its longitudinal axis”.
According to feature A the implant is an essentially cuboid shaped body. In a cuboid having, according to feature A, different lateral lengths, the longitudinal axis is well defined as the axis that is parallel to the edge of greatest length. The interpretation according to which the longitudinal axis is the longitudinal axis of the backbone is absurd and has to be dismissed, be it only because this would not be technically meaningful in connection with feature A.
The passage regarding the position of the partially rounded section on column 8, lines 35 to 37, to which the [opponent] has referred, is clearly erroneous because both figure 10, to which this passage refers, and the rest of the description show that the rounded parts are not only on the upper edge of the front axial end but extend along the whole length of the edge of the cuboid. Thus, in the light of the description, feature F is to be understood in such a way that each section is to be partially rounded.
It is true indeed that the wording of claim 1 requires a section (ein Querschnitt; the German ‘ein’ is ambiguous and could be translated by both ‘a’ and ‘one’) to be partially rounded, so that, from a purely grammatical point of view, the feature could be understood in the way proposed by the [opponent], i.e. that there is only one section with rounded parts. However, a patent has to be interpreted with the willingness to understand, and not with the willingness to misunderstand, so that technically unreasonable interpretations are excluded. However, the interpretation proposed by the [opponent] does not make any technical sense, so that feature F can only be interpreted in such a way that the rounded part(s) extend along the whole length of the implant, as also disclosed in the earlier application.
Also, in the light of the description, the expression “partially rounded section” can only be interpreted to mean that it either encompasses a section all edges of which are slightly rounded and/or a section where some of the edges are more strongly rounded. Thus feature F encompasses both the embodiment according to figures 3 to 6, as well as the embodiments according to figures 10 to 12. The fact that a claim can be interpreted in a broad way does not make it unclear.
Finally, it is clear from the entire wording of the claim that the adjective “oblong” (länglich) referring to the through hole of the implant in feature G is unrelated to the longitudinal axis (Längsachse) of the implant F but only describes the shape of the hole.
Thus claim 1 fulfills the requirements of A 84 EPC (1973).
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The file wrapper can be found here.