Intellectual Property

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Focus: Medical patent fatally wounded by 'fundamental' lack of clarity

21 September 2011

In brief: In a 'rare case' in patent law, a fundamental lack of clarity concerning the performance and function of an aspect of the claimed invention doomed the relevant claims of the patent to invalidity. Partner Sarah Matheson (view CV), Senior Associate Tom Reid and Law Graduate Courtney McLennan report on this recent case. 

How does it affect you?

  • The decision underscores the importance of ensuring that a patent sufficiently and accurately describes the invention and that each element of the invention actually functions as described.
  • It also serves as a warning to patentees against inserting an integer into patent claims for the sake of expediency where the integer in fact has no meaning or scientific basis.

The decision

Justice Dodds-Streeton's decision in Wake Forest University Health Sciences v Smith & Nephew Pty Ltd (No 2)1 was, in her Honour's own words, a 'rare case'2 where an integer present in the relevant claims of the patentees' patent was so lacking in clarity that it rendered the cited claims invalid.

The patent claimed a method and apparatus for treating wounds that operates by suction. The patentees, Wake Forest University Health Sciences and KCI Medical Australia Pty Ltd (collectively, KCI), sued industry rival, Smith & Nephew Pty Ltd (S&N) for infringement. S&N cross-claimed for revocation on a number of grounds.

Launched globally in 1996, KCI's product, the VAC Therapy System (the VAC product), is a variant of negative pressure wound therapy and the commercial embodiment of the patent. Negative pressure wound therapy works by applying negative pressure to wounds to promote healing. The VAC product includes a foam dressing that is placed in the wound. 98 per cent of KCI's annual sales turnover was attributable to the VAC product.

Eleven years after the launch of the VAC product, S&N, Australia's largest wound-care company, launched two negative pressure wound therapy kits named VISTA and EZCARE. While these kits first included gauze dressings, foam dressings were introduced in about late 2008. It was the kits including foam dressings, marketed under the brand name RENASYS, that KCI alleged infringed its patent.

The principal asserted claim of the patent required a 'screen means...sufficiently rigid to prevent wound overgrowth' (ie the foam dressing), which the court referred to as the 'screen rigidity integer'. Reference to that claim, or to the screen rigidity integer, was echoed throughout the 13 other claims in suit.

S&N submitted that the 14 asserted claims were invalid on a number of grounds, including lack of novelty, lack of inventive step, manner of manufacture, lack of fair basis, insufficiency, failure of the claims to define the invention, and lack of clarity of the claims. S&N was ultimately successful in proving invalidity on the last three of these grounds.

S&N's primary focus was a 'fundamental attack' on the screen rigidity integer. S&N contended that the screen rigidity integer was added to the combination claims for the sole purpose of avoiding lack of novelty on the basis of the prior art and criticisms by the Examiner.

At trial, expert evidence was led regarding the function of this integer. Experts for KCI gave evidence that the foam dressing functioned to modulate the growth of tissue in the wound and prevent 'wound overgrowth', construed by the court to mean hypergranulation, a rare condition where tissue grows above the level of healthy skin around the wound. Experts for S&N pointed out, however, that the effect of the invention was to stimulate the growth of tissue; there was no scientific evidence that the foam dressing had any ability to halt that growth once the tissue reached the level of the surrounding skin. S&N's experts testified, and KCI's experts admitted, that when using KCI's kits, they in fact addressed the issue simply by ceasing use of the kit once the desired level of tissue growth had been reached.

Justice Dodds-Streeton devoted a part of her judgment to a discussion of whether the screen rigidity integer was an essential integer of the asserted claims. Having determined that it was, her Honour found (favouring S&N's expert evidence that the foam dressing did not have the function described in the patent) that the person skilled in the art would attribute no meaning to it. The consequence of that finding was that S&N could not infringe the patent (because its products could not possess the meaningless integer), and that the asserted claims were invalid on the following grounds.


The Patents Act 1990 (Cth) (the Act) requires that the complete specification of a patent describe the invention fully.3 In finding that the invention was not fully described, the court referred to the screen rigidity integer's 'meaningless nature', and the associated failure of the patent to provide the skilled reader with sufficient guidance on how to select or construct a 'screen means' that would achieve the promised result of preventing wound overgrowth. The court noted that, had the screen rigidity integer not been present, it would have been satisfied that the specification sufficiently described the invention.

Failure of the claims to define the invention

The Act requires that the specification end with claims defining the invention.4 As the screen rigidity integer, in the court's words, 'lacked inherent meaning', it failed to define the monopoly claimed. Again, had the screen rigidity integer not been present, the court concluded that the claims would otherwise have satisfied this requirement.

Lack of clarity

The Act requires that the claims be 'clear and succinct' 5 The screen rigidity integer failed this fundamental requirement, as it lacked clarity. In her Honour's opinion, the 'obscurity and uncertainty' of the integer to the skilled addressee could not be remedied by reading the specification as a whole, where the same deficiencies of meaning were present.

Prospect of appeal

To date, the case has been hard fought. At an earlier stage, S&N successfully appealed6 the granting of an interlocutory injunction7 in favour of KCI to the Full Court of the Federal Court. It is possible, therefore, that KCI will seek to continue the case by appealing the trial judgment. Its avenues for doing so may, however, be limited by the fact that Justice Dodds-Streeton's findings as to invalidity appear substantially to have been based on a weighing of the evidence given by the parties' respective expert witnesses as to the scientific basis of the screen rigidity integer (or the lack thereof), rather than on any appealable interpretation of a point of law.


Justice Dodds-Streeton's repeated acknowledgment that a single baseless integer effectively sealed the patent's fate is a stark lesson. Ultimately, her Honour found (albeit obiter) that, absent the screen rigidity integer, with one exception8 the asserted claims would not have been invalid on any of the other grounds raised by S&N, including lack of novelty and lack of inventive step. To the extent, therefore, that KCI had added the screen rigidity integer in an effort to avoid the prior art and the Examiner's objections (as S&N contended), not only was it unnecessary for KCI to have done so, but the addition of that integer ultimately brought the relevant claims of the patent undone. The judgment therefore serves as a warning to patentees against inserting an integer into patent claims for the sake of expediency where the integer in fact has no meaning or scientific basis.

  1. [2011] FCA 1002.
  2. Wake Forest [3].
  3. Section 40(2)(a) of the Act.
  4. Section 40(2)(b) of the Act.
  5. Section 40(3) of the Act.
  6. Smith & Nephew Pty Ltd v Wake Forest University Health Sciences & Anor [2009] FCAFC 142.
  7. Wake Forest University Health Sciences & Anor v Smith & Nephew Pty Ltd [2009] FCA 630.
  8. Her Honour found, again obiter (but following a finding made by the Full Court in the appeal of KCI's interlocutory injunction application), that one of the 14 asserted claims was invalid as a 'mere collocation of integers' and thus not a 'manner of manufacture' as required by the Act.

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