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Inventor testimony regarding intent during patent prosecution irrelevant to claim construction
September 29, 2008

In a recent decision, the Federal Circuit vacated a stipulated judgment of noninfringement on claim construction grounds. The construction issue dealt with the significance of a limitation that applied to an "at least one" element. Specifically, the relevant claim required "at least one condylar element," where "the condylar element" had certain features. The district court held the requirement applied to all condylar elements present in an apparatus, as it was undisputed that either one or two could be used. Under this construction, it was undisputed there could be no infringement.

The Federal Circuit reversed. The court held the features described for "the condylar element" could be infringed even if only one of two condylar elements had the claimed features. The court noted that at least some of the objectives of the invention would still be met if one one of two elements had the claimed features. The court also rejected an inventor's testimony to the contrary, noting such testimony "is still limited by the fact that an inventor understands the invention but may not understand the claims, which are typically drafted by the attorney prosecuting the patent application." The court held such testimony as to the subjective intent of the inventor "is irrelevant to the issue of claim construction."

Howmedica Osteonics owns a patent relating to technology used in artificial knee joints. Claim 15 is the only independent claim at issue, and covers (emphases added):

15. In a knee prosthesis for replacing the natural knee, the knee prosthesis having a femoral component and a tibial component, the tibial component including a bearing member and the femoral component including at least one condylar element for confronting and engaging the bearing member to accomplish articulation of the knee prosthesis throughout a range of flexion, including a primary range of flexion between a hyperextended position and a flexed position, the engagement between the condylar element of the femoral component and the bearing member of the tibial component ordinarily taking place at a contact area along articular surface areas of the condylar element and the bearing member, the improvement comprising:anterior-posterior surface profile contours along the condylar element and the bearing member, the anterior-posterior surface profile contour along the condylar element having an essentially constant anterior-posterior articular radius throughout the articular surface area of the condylar element which contacts the bearing member during articulation throughout the primary range of flexion, the anterior-posterior articular radius having an origin lying generally along a line extending laterally between the medial and lateral collateral ligament attachment points on the femur of the natural knee.

A natural femur has two rounded projections called condyles that engage the upper end of the tibia. A replacement knee joint claimed may use either one or two condyles; the claim contemplates this by use of "at least one condylar element."

Howmedica sued Wright Medical for infringement of this patent. The district court construed the claim to require each condylar element to meet the specified geometric limitations, rather than just requiring one of two meet the limitations in the case of a bicondylar prosthetic. Under this construction, the parties agreed infringement could not be found, so the district court entered a stipulated judgment of noninfringement. Howmedica appealed.

The Federal Circuit reversed. While noting it was a "close case," the court held the claim could be infringed if a single condylar element met geometric limitations of the claim, even if the other condylar element did not. The court noted that if the inventors wanted both condyles to have to meet the geometric limitations, the "more natural way of drafting the claim language to achieve that result would be to require 'each condylar element,' rather than 'the condylar element,' to conform to the constant-radius geometry." Further, if only one condylar element in a bicondylar prosthetic met the geometric limitation, some of the objectives of the invention would still be achieved.

In addition, the court rejected the district court's reliance on a letter from the prosecuting attorney and the applicant regarding the examiner's position after an interview. The letter indicated the examiner's position was that "the claims could be worded more clearly to bring out the act that the constant radius in the present device does extend along enough of each condylar element to cover the range of articulation." The court noted that this letter was not part of the prosecution history. Accordingly, it was extrinsic evidence, and further it did not either "educate the court regarding the field of the invention" or "help the court determine what a person of ordinary skill in the art would understand claim terms to mean." As a result, the court held the letter was "of no value to the construction of the disputed claim language."

The court also rejected testimony from one of the inventors as requiring a contrary result. The inventor testified that it was his intent that the geometric limitation cover each condylar element present in a device. The court rejected reliance on this testimony, noting inventor testimony "cannot be relied on to change the meaning of the claims," and that "inventor testimoy as to the inventor's subjective intent is irrelevant to the issue of claim construction."

As a result, the court reversed the district court's claim construction and associated judgment of noninfringement.

Judge Prost dissented, and would have affirmed the district court's construction. In her opinion, the geometric limitations are worded as limitations on "the condylar element" as defined in the claim's preamble. The parties agreed that "the condylar element" was short for "the [at least one] condylar element." Accordingly, according to Judge Prost, the two should be coextensive in scope. Further, she observes the specification never indicates the two condylar elements may have different characteristics. As a result, Judge Prost would have affirmed the district court's judgment.

To read the full decision in Howmedica Osteonics Corp. v. Wright Med. Tech., Inc., click here.

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