Judges: Rader, Schall, Prost (per curiam)

[Appealed from C.D. Cal., Judge Taylor]

In Cross Medical Products, Inc. v. Medtronic Sofamor Danek, Inc., No. 05-1415 (Fed. Cir. Mar. 20, 2007), the Federal Circuit reversed the district court’s finding that the modified surgical screw of Medtronic Sofamor Danek, Inc. (“Medtronic”) infringed the claimed seat means limitation under the DOE, and affirmed the district court’s grant of SJ of noninfringement on a claimed anchor seat.

In claim 5 of U.S. Patent No. 5,474,555 (“the ’555 patent”), Cross Medical Products, Inc. (“Cross Medical”) described a fixation device for stabilizing vertebrae comprising at least two anchors, an anchor seat means, an elongated stabilizer, and a securing means. The seat means included “a vertical axis and first threads which extend in the direction of said vertical axis toward said lower bone interface to a depth below the diameter of the rod . . . .” Claim 7 of the ’555 patent recited an “anchor seat including external threads . . . said threads extending toward the rod contacting surface to a thread run-out, the distance between the rod [contacting] surface and the thread run-out being less than the diameter of the rod, . . . .” Cross Medical sued Medtronic for infringement of the ’555 patent based on Medtronic’s polyaxial screw design. The district court granted SJ of infringement and validity of claim 5 to Cross Medical and issued a permanent injunction. Medtronic appealed despite ongoing district court proceedings. While that appeal was pending, Medtronic redesigned its polyaxial screws to replace the threading with an undercut. However, Cross Medical asserted that the redesigned screws also infringed claim 5 and that both the original screw design and the redesigned screw infringed claim 7 of the ’555 patent. Without the benefit of the Federal Circuit’s guidance in the first appeal, the district court issued a second permanent injunction based on its finding that the redesigned screws also infringe claim 5.

The district court found that Medtronic’s redesigned screws did not infringe claim 7 of the ’555 patent. Medtronic filed a second appeal, which is the basis for this action.

After Medtronic filed its initial brief in the second appeal, the Federal Circuit issued an opinion in the first appeal, overturning the first permanent injunction. The parties agreed that the second permanent injunction could not stand in view of the decision in the first appeal; however, the parties contended that various issues remained for resolution in the second appeal. In addressing the remaining contentions, the Federal Circuit affirmed the finding regarding no infringement of claim 7; however, the Court did not review the district court’s analysis of infringement of claim 7 by Medtronic’s original screw design because the Court concluded in the first appeal that genuine issues of material fact remained unadjudicated. As a result, the Federal Circuit vacated and remanded the district court’s finding of SJ of infringement and validity of claim 7 for reconsideration in light of the first appeal. Upon reviewing the district court’s finding of infringement, the Federal Circuit first considered whether Medtronic’s redesigned polyaxial screws literally infringed claim 5 of the ’555 patent. Cross Medical argued that the groove in Medtronic’s redesigned screws was effectively a thread because the groove could act as a root of a thread. The Federal Circuit agreed with the district court’s conclusion that Cross Medical’s argument stretched the meaning of “thread” too far. As the Federal Circuit reasoned, “[s]imply because the undercut appears adjacent to a thread form does not convert that independent structure into a thread.” Slip op. at 8. Accordingly, the Federal Circuit affirmed the district court’s finding of no literal infringement of claim 5. Having found no literal infringement, the Federal Circuit then reviewed the district court’s finding of infringement under the DOE.

During prosecution of the ’555 patent, claim 5 was rejected for lack of antecedent basis, lack of written description support, and for double patenting. Cross Medical amended claim 5 to describe first threads “which extend in the direction of said vertical axis toward said lower bone interface to a depth below the diameter of the rod when it is in the rod receiving channel, . . . .” The district court concluded that this amendment did not trigger prosecution history estoppel under Festo because, as Cross Medical argued, the reason for this amendment was no more than tangentially related to the accused equivalent.

Specifically, the district court reasoned that the rationale behind the amendment was to describe and enable the claimed device and not to overcome prior art using an undercut. In the district court’s opinion, the amendment did not relate to an undercut. The Federal Circuit disagreed.

Under Festo, a narrowing claim amendment, whether to overcome prior art to satisfy 35 U.S.C. § 112 or to better describe the invention, can give rise to a presumption that prosecution history estoppel bars the patentee from recapturing the surrendered subject matter. The patentee can overcome this presumption by showing one of three things: (1) that the alleged equivalent was unforeseeable when the amendment was made; (2) that the alleged equivalent was tangential to the purpose of the amendment; or (3) that there was a reason why the patentee could not have described the insubstantial substitute in question.

When considering whether Cross Medical’s narrowing amendment was tangential to the undercut present in Medtronic’s screws, the Federal Circuit considered the applicant’s statements as to why the amendment was made. The applicant explained that the amendment was made “to define the anchor seat means having a channel and threads which cooperate with the securing means . . . so as to capture the stabilizer between the channel and the securing means since the [anchor] seat threads extend toward the channel to a depth below the top of the stabilizer . . . .” Based on this explanation, the Federal Circuit surmised that the thread depth limitation was added to capture the way in which the stabilizer operated, thus overcoming the § 112 rejections. With this rationale in mind, the Court concluded that the accused equivalent, which did not have threads that “extend . . . to a depth below the top of the stabilizer,” did not “capture” this aspect of the invention.

Cross Medical also argued that the alleged equivalent was not foreseeable at the time the amendment was made. The Federal Circuit also rejected this argument, noting that in its argument to support literal infringement, Cross Medical admitted that an undercut was known in the art to act as a thread. Thus, the Federal Circuit found that Cross Medical did not overcome the Festo presumption under either exception, and reversed the district court’s finding of infringement of claim 5 under the DOE.