Mr Justice Arnold ruled on 12 November 2010 that Abbott’s eight coronary stents did not infringe any of Medinol’s three patents, EP(UK) 0 846 449, 1 181 901 and 1 181 902. The 449 and 902 patents were found valid (the 902 in amended form) and the 901 invalid. There were 13 issues relating to construction (two discussed here), novelty over two documents and obviousness over one, as well as added matter and insufficiency, resulting in a judgment of 268 paragraphs. The first interesting issue of construction related to “meander patterns” and the second to whether “loops” widen longitudinally upon expansion of the stent.

Claim 1 of the 449 and 902 patents used the term “meander patterns”, which was defined in the patents as “a periodic pattern about a center line”. The dispute arose over whether this meant that the meander patterns found in the stents had to be about a line of symmetry. Abbott argued in the affirmative whereas Medinol initially asserted that it referred to the direction that the meander pattern traverses the stent. When asked to clarify their position during closing submissions Medinol stated that the term referred to a line which runs approximately through the centre of the meander pattern with approximately equal parts of the pattern on either side. Not surprisingly the meander pattern of the Abbott stents, shown below in blue, was not symmetrical.

Click here to view the picture.

This issue was considered not only by the UK court, but previously by courts in the US, German and the Netherlands. Each court considered the purpose of the meander patterns and in particular the requirement that it be “about a center line”, with Abbott asserting that the purpose of symmetrical patterns was to assist in the uniformity of expansion of the stent. Medinol instead asserted that the skilled person would understand that the purpose was to define the direction of the meander pattern and hence ensure that the first and second meander patterns have different directions. Arnold J agreed with Abbott noting that Medinol’s argument was flawed in that such an explanation did not require the pattern to have a centre line at all. The courts in the Netherlands and the US previously came to the same conclusion as Arnold J. The Dutch court noted that Medinol’s interpretation stripped the words “center” and “about” of virtually all meaning. The German court, which heard the case after the Dutch decision, disagreed. There was no indication in the patent description that symmetry was of essential significance and, the court concluded, symmetry was not necessary to provide a flexible stent that contracts minimally during expansion in a longitudinal direction. Although Arnold J agreed that symmetry was not necessary to achieve uniform expansion, he held that, regardless, the skilled person would conclude from reading the patents that symmetry was required as symmetry has an apparent technical advantage. Arnold J was further persuaded by the fact that if choosing Medinol’s construction one is left uncertain about whether an approximately equally distributed meander pattern about a centre line would infringe.

The second issue relating to construction that impacted on infringement was the question of whether the loops of Abbott’s stents widened longitudinally upon expansion of the stent. Arnold J held that the loops did not widen noting that it was Medinol’s burden to prove this point and that Medinol had adduced no positive evidence despite having in-house specialist testing that could be used to test the loops of the stent during expansion. Arnold J was left with conflicting expert evidence and although the photographs and measurements adduced by Abbott’s expert could not be relied on as positively proving the point, they were at least consistent with the evidence.  

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