Cross Medical asserted 5,474,555 against Medtronic for its polyaxial screws. After losing at trail, Medtronic tried to design around, only to be caught up in a DOE scrape brought by Cross Medical.

The technical issue was one of thread depth. Thread depth wasn't part of the original claims, nor covered in the specification, and the examiner rejected the claim for obviousness type double patenting.

Notably, this thread depth requirement was not in the '555 patent's original application. Rather, the originally filed claim simply called for a "seat means including a vertical axis and first threads" without any particular limitation about the extent of the threading. The Examiner rejected this original claim, however, for lack of antecedent basis and lack of support in the specification (35 U.S.C. § 112, ¶¶ 1-2), for obviousness type double patenting over U.S. Patent No. 5,360,431, and for anticipation (35 U.S.C. § 102(b)) over U.S. Patent No. 4,805,602 (the '602 patent). In response, the Applicant amended the claim...

In the same filing, the Applicant also amended the specification to address the 35 U.S.C. § 112, ¶ 1 rejection and submitted a terminal disclaimer to address the double patenting rejection. Thereafter, the Patent Office allowed the claim.

Presumed prosecution estoppel was the apparent basis for Medtronic's design-around. But the district court didn't buy Medtronic’s argument that a Festo presumption barred application of the doctrine of equivalents. The district court ruled that a Festo estoppel was inapplicable, as the narrowing of the claim (5) was only tangentially related to the accused equivalent.

The CAFC preamble on prosecution history estoppel prohibiting a doctrine of equivalents infringement finding, and escape clauses:

Prosecution history estoppel prevents a patentee from recapturing under the doctrine of equivalents subject matter surrendered during prosecution to obtain a patent. See Festo, 344 F.3d at 1365 (citing Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 741 (2002) (Festo VIII)). Indeed, by surrendering subject matter, a narrowing amendment classically invokes the doctrine. In this case, the patentee narrowed claim 5 to address a § 112 rejection. An amendment made to comply with § 112 may give rise to estoppel. Honeywell Int'l Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131, 1142 (Fed. Cir. 2004) (en banc) ("[I]f a § 112 amendment is necessary and narrows the patent's scope—even if only for the purpose of better description—estoppel may apply. A patentee who narrows a claim as a condition for obtaining a patent disavows his claim to the broader subject matter, whether the amendment was made to avoid the prior art or to comply with § 112."). Although these circumstances create a presumption of estoppel under Festo, the patentee may still rebut that presumption. Rhodia Chimie v. PPG Indus. Inc., 402 F.3d 1371, 1382 (Fed. Cir. 2005) ("The patentee may rebut that presumption by showing that the alleged equivalent was unforeseeable at the time the amendment was made, that the alleged equivalent was tangential to the purpose of the amendment, or that there was some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question."). In this case, the district court determined that Cross Medical successfully overcame the Festo presumption by demonstrating that the amendment bore no more than a tangential relationship to the equivalent.

Cross Medical argued the claim as amended with regard to DOE was not because of the rejection, that the relationship between the rejection and the scope of the claim limitation under which DOE would apply to thread depth was merely tangential. The CAFC didn't buy it, reversing the district court ruling.

On appeal, Cross Medical argues that the amendment to claim 5 was tangential or, in the alternative, that it was unforeseeable. This court reaffirms the principle that the tangential relation criterion for overcoming the Festo presumption is very narrow and finds that neither the narrow tangential rebuttal principle nor the foreseeability principle applies to this case.

As discussed in the Festo opinion, the tangentially related criterion requires a patentee to demonstrate that "the rationale underlying the narrowing amendment [bore] no more than a tangential relation to the equivalent in question." Festo VIII, 535 U.S. at 740, 122 S. Ct. 1831. In other words, this criterion asks whether the reason for the narrowing amendment was peripheral, or not directly relevant, to the alleged equivalent.

Festo, 344 F.3d at 1369 (quoting Festo VIII, 535 U.S. at 740). The Festo court further stated: "Although we cannot anticipate the instances of mere tangentialness that may arise, we can say that an amendment made to avoid prior art that contains the equivalent in question is not tangential; it is central to allowance of the claim." Id. Finally, the court observed that the inquiry into whether a patentee can rebut the Festo presumption under the "tangential" criterion focuses on the patentee's objectively apparent reason for the narrowing amendment and that the reason "should be discernible from the prosecution history of record, if the public notice function of a patent and its prosecution history is to have significance." Id.

In this case, the prosecution history of the '555 patent shows a narrowing amendment that also "contains the equivalent in question." Id. The '555 patent Applicant explained to the Examiner that:

the claims have . . . been amended to define the anchor seat means having a channel and threads which cooperate with the securing means (i.e., the nut) so as to capture the stabilizer between the channel and the securing means since the ancor [sic] seat threads extend toward the channel to a depth below the top of the stabilizer when it is in the channel.

In other words, the prosecution history explains that the thread depth limitation was added to capture the manner in which the stabilizer aspect of the invention operated and thereby overcome the 35 U.S.C. § 112 rejections. Thus, the accused equivalent, which does not include threads extending "to a depth below the top of the stabilizer" and correspondingly does not capture this aspect of the invention relates to the amendment as shown even by the applicant's own statements. For this reason, the district court erred in reliance on the tangential rebuttal principle to avoid the doctrine of equivalents.

Cross Medical also argued that Medtronic's screw infringed because it was a variation that was unforeseeable at the time of prosecution, hence DOE applied. The district court hadn't bought that argument, and the CAFC concurred with "hooey"; the workaround was old hat, and thus prosecution estoppel applied.

As an alternative, Cross Medical argues that the alleged equivalent was unforeseeable at the time of the amendment and thus the Festo presumption could be overcome with this rebuttal criterion. See Festo, 344 F.3d at 1365 (commenting that the presumption can also be overcome "by demonstrating that 'the equivalent [would] have been unforeseeable at the time of the [amendment]'" (quoting Festo VIII, 535 U.S. at 740-41)). To the contrary, the evidence of record clearly demonstrates that the use of an undercut or recess, the alleged equivalent here, is an old and well known fundamental of basic machining that was entirely foreseeable at the time of the amendment to one of ordinary skill in the art. See, e.g., John R. Walker, Machining Fundamentals, Fundamentals Basic to Industry, at 185-86 (1981); U.S. Patent No. 5,129,900; U.S. Patent No. 5,190,543.

See Freedman Seating Co. v. Am. Seating Co., 420 F.3d 1350, 1361 (Fed. Cir. 2005) (citing Sage Prods., Inc. v. Devon Indus., Inc., 126 F.3d 1420, 1425 (Fed. Cir. 1997)) ("[A]s between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the cost of its failure to seek protection for [a] foreseeable alteration of its claimed structure."); SmithKline Beecham Corp. v. Excel Pharm., Inc., 356 F.3d 1357, 1363 (Fed. Cir. 2004) ("Usually, if the alleged equivalent represents later-developed technology (e.g., transistors in relation to vacuum tubes, or Velcro® in relation to fasteners) or technology that was not known in the relevant art, then it would not have been foreseeable. In contrast, old technology, while not always foreseeable, would more likely have been foreseeable."); Glaxo Wellcome, Inc. v. Impax Labs., Inc., 356 F.3d 1348, 1353 (Fed. Cir. 2004) (same).

In concurrence, Judge Radar rubbishes the tangential rebuttal principle, as drawing a muddy line, contrary to the intent of patent law for clear demarcation of claim scope.

In my view, the tangential rebuttal principle exacerbates the policy deficiencies of the doctrine of equivalents. Upon invoking tangentiality, the patentee has already admitted that the equivalent falls within the scope of surrendered subject matter. Further, if the case permitted, any patentee would invoke the primary "foreseeability" rebuttal factor. Thus, an invocation of "tangentiality" often admits that the equivalent was both within the scope of the surrender and foreseeable at the time of prosecution. In other words, the patent drafter could have claimed the surrendered and foreseeable technology, but declined to do so.

Furthermore, the tangentiality rebuttal principle, by its nature, undermines principles of public notice. This rebuttal principle operates because the patentee has expounded very different purposes for its narrowing amendment than those applicable to the tangential equivalent. The prosecution record thus does not address this "tangential" equivalent (which nonetheless was surrendered and was known and claimable during prosecution). In other words, the patentee gets a reward—coverage under the doctrine of equivalents—precisely because its explanations did not give the public any notice of the unclaimed and surrendered subject matter. The public might have believed it could practice technology that the patentee surrendered in prosecution. Moreover, the public might have reasonably undertaken to practice that foreseeable technology because the patentee could have claimed it but declined to do so. Even beyond these principles, the public might have consulted the prosecution history and learned that the patentee gave no explanation for its surrender of this foreseeable technology. Thus, a diligent study of the patent and its prosecution history would give the public every reason to believe that the "tangential" subject matter would fall outside the scope of the invention and within the public domain. The basic principles of public notice would suggest these unclaimed and surrendered "tangential" technologies have no conceivable basis to expect patent protection.

This case is a classic example of the tangentiality principle running counter to principles of public notice. Medtronic had suffered an injunction. It deliberately sought to design around the patented technology—a response that patent law encourages. State Indus. Inc. v. A.O. Smith Corp., 751 F.2d 1226, 1236 (Fed. Cir. 1985) ("One of the benefits of a patent system is its so-called 'negative incentive' to 'design around' a competitor's products, even when they are patented, thus bringing a steady flow of innovations to the marketplace."). It undoubtedly consulted the patent and adjusted its technology with reference to the claim language and prosecution history of the patent. Then, after it adopted unclaimed technology that the patentee had deliberately surrendered to the public, it finds itself again subject to an injunction. Tangentiality thus, as in this case, can defeat principles of notice and proper procedures for designing around patented technology. Medtronic's situation illustrates the difficulties of a broad application of tangentiality.

This "tangential" rebuttal principle becomes even more difficult in practice. What neutral standard makes some surrendered and unclaimed technologies infringing equivalents while others enjoy no protection? This tangential concept has no analogue in patent law. How tangential does it have to be?

In any event, this case reaffirms that the tangential rebuttal principle remains very narrow.