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Divided Panel Affirms Finding of Motivation to Combine Implant Cross-Linking Patents

May 24, 2012

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Last Month at the Federal Circuit - June 2012

Judges: Newman (dissenting), Bryson (author), Fogel (district court judge sitting by designation)

[Appealed from: Board]

In In re Hyon, No. 11-1239 (Fed. Cir. May 24, 2012), the Federal Circuit affirmed the Board’s obviousness rejection of a reissue application after finding substantial evidence of a valid motivation to combine two prior art references.

Reissue Application Serial No. 10/643,674 (“the reissue application”) to Suong-Hyu Hyon and Masanori Oka (collectively “Hyon”) stemming from U.S. Patent No. 6,168,626 (“the ’626 patent”) is directed to the use of “Ultra High Molecular Weight Polyethylene” (“UHMWPE”) in artificial joints. Specifically, the claims at issue are directed to a method for cross-linking UHMWPE by irradiating a block of UHMWPE with a high energy radiation, the UHMWPE block having a molecular weight of not less than five million. The block would then be heated “to a compression deformable temperature below the melting point of the UHMWPE,” “subject[ed] . . . to pressure,” and then cooled.

The examiner rejected the reissue claims as obvious over U.S. Patent No. 5,030,402 to Anagnostis Zachariades (“Zachariades”) and U.S. Patent No. 3,886,056 to Ryozo Kitamaru (“Kitamaru”). Zachariades is directed to a method for producing UHMWPE having a molecular weight of three million to six million. In particular, Zachariades teaches compression deformation of UHMWPE at a temperature between 80º C and the melting point of the polymer, applying pressure during and after cooling to retain chain orientation, subjecting the final product to radiation cross-linking after unmolding, and then shaping the deformed UHMWPE into a final product.

Kitamaru discloses a method for preparing UHMWPE by first cross-linking the UHMWPE by irradiating it with ionizing radiation, then heating the cross-linked UHMWPE to a molten state at a temperature of at least the melting point of the polyethylene while it is extended or compressed under pressure, i.e., compression deformed, and then cooling the polyethylene while maintaining it in an extended or compressed state. Kitamaru teaches that its method of cross-linking before compression results in a product that has a higher melting or softening point, improved transparency, and excellent dimensional stability.

During prosecution, the examiner found that Zachariades meets each limitation of the reissue claims except for the step of cross-linking the UHMWPE, which Kitamaru discloses. The examiner further concluded that one of ordinary skill in the art would have had a reasonable expectation of success in obtaining those enhanced properties by combining the techniques taught by the two references.

On appeal to the Board, Hyon did not challenge the examiner’s findings as to what Zachariades and Kitamaru teach, but argued only that there would have been no motivation to combine the references. The Board rejected Hyon’s arguments that a motivation to combine was lacking, because both references are directed to UHMWPE. Moreover, the Board found that Kitamaru provides the reason for modifying Zachariades to cross-link before compressing—to provide improved dimensional stability and transparency at high temperatures. Accordingly, the Board affirmed the examiner’s rejection of all the claims of the reissue application, finding that the technique disclosed by the claims was nothing more than the predictable use of a prior art element, i.e., cross-linking prior to molding, according to its established function, i.e., to improve material properties such as by increasing the melting point.

On appeal to the Federal Circuit, Hyon again challenged the Board’s determination of motivation to combine. Hyon first argued that one of ordinary skill in the art would not be motivated to combine the references because Zachariades is directed to artificial joints, whereas Kitamaru is directed to films or sheets, which Hyon contended represent “fundamentally different material technologies.” Slip op. at 6-7. The Federal Circuit disagreed, finding substantial evidence to support the Board’s conclusion that both references pertain to UHMWPE.

The Federal Circuit also found substantial evidence to support the Board’s determination that the fact that Zachariades teaches cross-linking after molding does not affect the motivation to combine it with Kitamaru. The Court noted that Zachariades does not state that UHMWPE products can be made only by cross-linking after compression deformation, nor does it state or suggest that faulty or inferior products will result from cross-linking prior to compression.

The Federal Circuit further rejected Hyon’s argument that, to find motivation to combine, the Board improperly relied on the arbitrary selection of a single feature from Kitamaru (precompression
cross-linking) while ignoring the other features. In the Court’s view, the examiner and the Board selected the precompression cross-linking step because Kitamaru indicated that precompression cross-linking was responsible for the improved properties. Thus, the Court found that the Board merely selected an element emphasized by the reference, relying on the reference’s suggestion that the selected element was responsible for the improved properties. Accordingly, the Court concluded that substantial evidence supports the Board’s determination regarding motivation to combine.

Finally, the Court rejected Hyon’s claim that the references fail to teach further processing to make a final product after deforming and cooling the UHMWPE, as required by claim 84 of the reissue application. The Court concluded that substantial evidence supports the Board’s determination that Zachariades teaches postprocessing to form a final component. Thus, the Court affirmed the Board’s determination that the reissue claims would have been obvious in light of the prior art.

Judge Newman, in a dissenting opinion, explained that the motivation to combine, as well as the suggestion that the claimed method would be obvious to perform, must be supported solely by what the patent teaches. In Judge Newman’s view, “[w]hen the technologic field is mature, apparently small changes that produce unexpected results or improved properties are of heightened significance.” Newman Dissent at 8. Thus, Judge Newman concluded that “[n]othing in the record suggests that a person of ordinary skill would have foreseen that Hyon’s method of slight radiation cross-linking followed by heating and compression deformation would produce the described benefits.” Id.

Indeed, Judge Newman concluded that the Board cited no reason to expect that the Hyon method would produce a superior polyethylene artificial joint. Judge Newman also found that the “selective combination of aspects of Kitamaru and Zachariades is achieved only with hindsight knowledge of Hyon’s achievement, for nothing in either reference or elsewhere in the prior art suggests this modification.” Id. at 10.