When You Amend, You Can't Extend - CAFC Finds Festo Bars Equivalents

Cross Medical Products, Inc. v. Medtronic (05-1415) March 20, 2007

Cross sued Medtronic for violating their spinal implant patent and won. Medtronic appealed, and in the meantime redesigned their product to avoid infringing the Cross patent.

Medtronic based the redesign off a 112 Festo-type amendment made in the claims:

securing means which cooperate with each of said anchor seat portions spaced apart from said bone interface and exterior to the bone relative to said elongated rod, said seat means including 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

Instead of using the threads extending below the rod, Medtronic used a "groove or undercut" that lacked thread forms to secure the screw above the rod.

Cross sued Medtronic on the redesign, alleging that they infringed under the doctrine of equivalents. The district court found infringement under the function-way-result, despite the amendments:

The applicant was not attempting to overcome prior art using an undercut, and the amendment did not relate to an undercut. Therefore, the rationale was no more than tangentially related to Medtronic's new screw design, in which threads extend part of the way toward the rod and an undercut extends to a depth below the top of the rod. Medtronic's new screw design is "beyond a fair interpretation of what was surrendered."

Under Festo, 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. In other words, this criterion asks whether the reason for the narrowing amendment was peripheral, or not directly relevant, to the alleged equivalent.

The CAFC reversed the district court and ruled that Medtronic did not infringe as a matter of law. Specifically, the court found that the amendment was not tangential, since the manner in which the screw was secured was relevant towards any equivalents. Also, since using "grooves" and "undercuts" was known in the art, the Cross could have claimed these features, but chose not to.

In a concurring opinion, Judge Rader reaffirmed that the tangential rebuttal principle "remains very narrow":

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 . . . 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.