Applying well-settled principles of claim construction, the U.S. Court of Appeals for the Federal Circuit has held that the use of the term "a" in connection with the restrictive clause "consisting of" describes a singular claim element. Norian Corp. v. Stryker Corp., Case No. 05-1172 (Fed Cir. Dec. 6, 2005) (Bryson, J.).
Norian Corp.’s patent describes a kit for preparing rapid-setting calcium phosphate compositions for use in medical and dental procedures. The claim in issue describes "[a] kit for preparing a calcium phosphate mineral, said kit consisting of: at least one calcium source and at least one phosphoric acid source free of uncombined water as dry ingredients; and a solution consisting of water and a sodium phosphate …."
Norian argued the claim term "a sodium phosphate" should be construed to mean a "mixture of multiple types of sodium phosphates as well as a single sodium phosphate" (pointing out that multiple sodium phosphates break down into the same ions once they are placed in water). The district court held the term required the subject solution be made from only a single type of sodium phosphate and granted summary judgment of noninfringement. Norian appealed.
The Federal Circuit affirmed. It agreed with the district court that the term "a," when used with the restrictive term "consisting of," refers to one-and-only-one of the substance recited in the limitation. The Court noted the first portion of the claim used the language "at least one" to describe calcium and phosphoric acid sources. It also noted the same language could have been used in place of the term "a" in the second portion of the same claim if the applicant had been meant to contemplate multiple sodium phosphate types. The Court also found support for its restrictive construction in case law that interpreted the term "a" in a singular manner when used with "consisting of," as well as in the specification of the patent-in-suit, which referenced the use of only a single solute. Finally, the Court also relied on the prosecution history, which showed that Norian narrowed the claim at issue by switching the claim’s preamble from "comprising" to "consisting essentially of" to "consisting of."
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