In a significant decision for medical device patent litigation, the Federal Circuit vacated and remanded a district court’s ruling that had invalidated key claims in a patent dispute between Teleflex and Medtronic. The case centered on guide extension catheter technology used in cardiovascular procedures, with the core issue being whether the term “substantially rigid portion/segment” was indefinite. The ruling provides important guidance on claim construction, functional limitations, and indefiniteness under patent law.

Background of the Case

Teleflex, along with its affiliates, sued Medtronic in the District of Minnesota for infringing seven patents related to guide extension catheters, which help deliver interventional devices into arteries. The patents describe a coaxial guide catheter with a substantially rigid portion that enables controlled movement within a standard guide catheter.

The dispute boiled down to the meaning of “substantially rigid portion/segment”—a key term appearing in multiple claims across Teleflex’s patents. Medtronic argued that the term was indefinite because its boundaries varied across claims, making it impossible for a skilled artisan to determine its precise scope.

The district court agreed with Medtronic, ruling that the inconsistency in claim boundaries made the term indefinite, effectively invalidating all asserted claims. Teleflex appealed, arguing that the court misapplied the law on claim construction and indefiniteness.

Key Issues Addressed by the Federal Circuit

1. Can the Boundary of a “Substantially Rigid Portion” Vary Across Claims?

The district court ruled that all claims must define the substantially rigid portion in a consistent way, and since some claims included a side opening in the rigid portion while others placed it separately, the claims were “mutually exclusive” and thus indefinite.

The Federal Circuit rejected this logic, clarifying that:

• Independent claims do not need to define terms in exactly the same way across a patent.
• Claim drafting often involves describing the same invention in different ways to cover variations in implementation.
• The fact that some claims place the side opening within the rigid portion while others place it distal to it does not automatically create indefiniteness.

2. Functional Claiming and the Meaning of “Substantially Rigid”

Teleflex argued that “substantially rigid” should be interpreted as a functional limitation—meaning the portion of the catheter that is rigid enough to perform a specific function (i.e., advancing within the guide catheter).

The Federal Circuit agreed, stating:

• The term can be defined by its function rather than requiring an exact material or structural boundary.
• Functional claiming is valid as long as it provides reasonable certainty about the claim’s scope.
• The district court erred in insisting that all claims must define rigidity with the same fixed boundary.

3. Role of Claim Construction in Indefiniteness Analysis

The court emphasized that indefiniteness is a high standard and that:

• A claim is only indefinite if it fails to inform skilled artisans with reasonable certainty about the scope of the invention (Nautilus, Inc. v. Biosig Instruments, Inc.).
• Since experts and the Patent Trial and Appeal Board (PTAB) were able to interpret and apply the claims, the term could not be considered “insolubly ambiguous”.

Thus, the Federal Circuit vacated the indefiniteness ruling, instructing the district court to reassess claim construction without treating the claims as inherently conflicting.

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Impact of the Decision

This ruling has significant implications for medical device patents and functional claim drafting:

• Claim Variability is Not Fatal: The decision reinforces that patent claims can define the same invention in different ways without necessarily being indefinite.
• Functional Claiming Remains Viable: The court validated the use of functional limitations, allowing claims to describe components by what they do, rather than only by their structure.
• Higher Bar for Indefiniteness: The ruling underscores that courts must apply a high standard before declaring a patent claim invalid due to indefiniteness.

For patent litigators and medical device companies, this case serves as a reminder that precision in claim construction matters, but reasonable flexibility is allowed when defining key terms.

By Charles Gideon Korrell

Here’s a prior article written on the Nautilus case.