Polymer patent invalidated by split Federal Circuit

The US Court of Appeals for the Federal Circuit has invalidated a polymer patent owned by Howmedica Osteonics, reversing an earlier decision from the US Patent and Trademark Office (USPTO) and ending the company’s long running dispute with medical device company Zimmer.

In a judgment handed down on Friday, February 26, judges Alan Lourie and William Bryson agreed with Zimmer’s challenge that claims 7-12 of US patent number 6,818,020 were invalid on the grounds that they were obvious.

The ‘020 patent covers an ultra-high molecular weight polyethylene (UHMWPE) with a superior oxidative resistance. The patent’s preamble describes its claims as being directed toward a “medical implant”.

Howmedica claimed Zimmer infringed the ‘020 patent in 2005, alongside three other patents. It filed its complaint at the US District Court for the District of New Jersey.

The district court invalidated the other three patents but stayed a decision on the ‘020 patent because Zimmer had filed an inter partes re-examination request at the USPTO. Inter partes re-examinations became inter partes reviews in 2012.

The question in the re-examination request centred on whether the term “medical implant” constituted a claim limitation.

According to the USPTO, “any terminology in the preamble that limits the structure of the claimed invention must be treated as a claim limitation”.

The USPTO concluded that claims 7-12 of the patent were not obvious.

In Friday’s decision, the federal circuit reversed the ruling.

According to Lourie, who wrote the majority opinion: “The specification’s regular use of the preamble language, ‘medical implant,’ is of no additional importance here; it reiterates that a ‘medical implant’ is one use for UHMWPE”.

However, Judge Pauline Newman dissented, arguing that the term “medical implant” in the patent specification was a limitation in the patent.

“The claim is not written in preamble form, but is explicitly directed to a medical implant, not to a polymer of varied uses whereby the product identified in the ‘preamble’ may not be limiting of either validity or infringement,” Newman wrote.

She also praised the USPTO, noting that the decision was highly comprehensive in assessing the evidence placed before it.