Absolute But Not Indefinite: Court Upholds Outcome-Oriented Patent Language

In a recent decision that may surprise patent drafters and litigators alike, the Northern District of Illinois held that a patent claim using flexible, outcome-oriented language was not invalid for indefiniteness. In Xodus Medical Inc. et al. v. U.S. Surgitech, Inc., the court granted summary judgment in favor of the plaintiff, rejecting the defendant's argument that certain claim language in surgical room slippage reduction patents was too vague to be enforceable. The ruling highlights an important and sometimes counterintuitive lesson: a term can be qualitative and still sufficiently definite if it provides an understandable boundary tied to a practical result.

The dispute centered on claim language requiring a component to move “sufficiently slow to maintain a depression for a desired period.” The accused infringer argued that phrases such as “sufficiently slow” and “desired period” were inherently subjective and failed to inform a skilled artisan of the invention's scope with reasonable certainty. Patent law requires claims to define the invention clearly so others can understand what is covered and what is not. If a claim is too ambiguous to determine its boundaries, it is invalid as “indefinite.”

The court disagreed that this language crossed the line into impermissible vagueness. It distinguished the phrase from open-ended comparative terms like “better” or “improved,” which lack a baseline for comparison. In this case, the claim did not compare two different things. Instead, it set a clear, though qualitative, requirement tied to a functional outcome: maintaining a depression for as long as needed. The “desired period,” the court explained, would be understood by a skilled user as the time necessary to keep a patient stable during a position change or procedure. That duration might vary from case to case, but variability alone does not make a claim indefinite. The key question is whether the claim, read in context, provides reasonable certainty, not mathematical precision.

This decision offers an unexpected insight: flexibility does not automatically equal fatal ambiguity. Many practitioners assume that without numerical boundaries or bright-line metrics, a patent claim is vulnerable. But the court emphasized that patent law does not demand exact quantification where the technology or real-world use does not require it. Instead, courts consider whether the claim language, viewed through the eyes of a skilled person and in light of the patent specification, conveys a clear functional standard. An outcome-driven limitation, such as maintaining stability for the necessary duration, can be sufficiently concrete if it meaningfully guides application of the invention.

For businesses and litigators beyond the patent bar, the case offers a broader lesson about drafting and risk assessment. Language that appears flexible or context-dependent is not automatically unenforceable. Courts will examine whether the language provides a workable boundary in practice, not whether it eliminates all discretion. For patent owners, this decision reassures that practical, user-centered claim language may withstand indefiniteness challenges. For accused infringers, it is a reminder that challenging qualitative terms requires more than pointing to variability. In short, precision matters, but context matters too.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.