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“Tangentiality” Not Available Unless Demonstrated In Prosecution History


A per curium Federal Circuit panel decision in Cross Medical Products, Inc. v. Medtronic Sofamor Danek, Inc., et al. (No. 05-1415, March 20, 2007) finds that factual circumstances appropriate for invoking “tangentiality” to overcome a presumption that estoppel applies to a claim amendment remain very narrow and must appear in the prosecution history.

During litigation, Medtronic had focused on the prosecution history in attempting to design around one of the claims at issue by altering its original screw design to terminate threads at a position above a rod diameter. In response to indefiniteness rejections made during prosecution before the patent examiner, the applicant had amended that claim, which as originally written, did not have any particular limitation about the extent of the threading, to recite that threads extend to a depth below the diameter of the rod. The district court still found infringement by Medtronic’s redesigned screws under the doctrine of equivalents, concluding that the rationale behind the claim amendment was “no more than tangentially related to Medtronic’s new screw design.” Medtronic’s reliance on the doctrine of equivalents as barred was rejected.

Following issuance of a permanent injunction and Medtronic’s appeal, the Federal Circuit panel reverses, concluding that summary judgment of non-infringement of all asserted claims should have been entered for Medtronic with respect to the redesigned screws. The prosecution history explains that the thread depth limitation, i.e. that the “anchor seat threads extend toward the channel to a depth below the top of the stabilizer when it is in the channel,” was added to capture the manner in which the stabilizer aspect of the invention operated and thereby overcome the indefiniteness 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.

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