When medical devices cause injury, the legal theory underlying a patient's claim depends on what went wrong with the product. Understanding the three categories of product defects—design defects, manufacturing defects, and warning defects—helps injured patients and their attorneys identify the strongest basis for pursuing compensation against device manufacturers.
Design Defects: When the Product Concept Is Flawed
A design defect exists when the fundamental specifications for a medical device make it unreasonably dangerous, regardless of how carefully individual units are manufactured. Every device built according to a defective design shares the same flaw. This category of defect has given rise to some of the largest medical device litigations in history.
The metal-on-metal hip implant litigation illustrates classic design defect claims. These devices used metal ball and socket components that ground against each other with normal movement, releasing cobalt and chromium particles into surrounding tissue. The resulting metallosis caused tissue death, bone destruction, and systemic metal poisoning in thousands of patients. The problem was inherent in the design—every metal-on-metal hip using this configuration posed similar risks.
Courts evaluate design defects using either a consumer expectations test or a risk-utility analysis, depending on jurisdiction. Under consumer expectations, a device is defective if it fails to perform as safely as an ordinary consumer would expect. Risk-utility analysis weighs the product's benefits against its dangers, considering whether a safer alternative design was feasible. Manufacturers may be liable even when devices receive FDA clearance if the design poses unreasonable risks that a safer alternative could have avoided.
Manufacturing Defects: When Production Goes Wrong
Manufacturing defects arise when specific devices deviate from their intended design due to problems during production. Unlike design defects that affect all units, manufacturing defects may impact only certain devices, batches, or lots. A device can be perfectly designed yet become dangerous if manufacturing processes introduce flaws.
Common manufacturing defect scenarios include contamination during production that introduces harmful substances, improper sterilization allowing bacterial growth, substandard materials substituted for specified components, assembly errors that compromise device function, and quality control failures that allow defective units to ship.
Manufacturing defect claims do not require proving that the overall design was flawed—only that the specific device implanted in the plaintiff did not conform to design specifications and caused injury as a result. The manufacturer is strictly liable for such defects without regard to whether reasonable care was exercised during production.
Warning Defects: The Failure to Inform
Even properly designed and manufactured devices can give rise to liability when manufacturers fail to provide adequate warnings about known risks. Medical device companies have a duty to inform healthcare providers and, in appropriate circumstances, patients about dangers associated with their products. When companies possess safety information but fail to communicate it effectively, injured patients may recover under failure to warn theories.
In the medical device context, the learned intermediary doctrine often applies, meaning manufacturers typically satisfy their warning obligations by adequately informing prescribing physicians rather than patients directly. However, this doctrine has exceptions, and manufacturers cannot hide behind it when they fail to provide doctors with complete risk information or when direct-to-consumer marketing occurs.
Warning defect claims frequently arise when manufacturers knew about risks from clinical trials, adverse event reports, or post-market surveillance but downplayed or omitted this information from product labeling. The fact that FDA later required enhanced warnings often supports claims that earlier labeling was inadequate.
Proving Defect and Causation
Regardless of defect category, plaintiffs must prove both that a defect existed and that it caused their injury. Expert witnesses play crucial roles in medical device litigation, with engineers testifying about product specifications and failure analysis while medical experts address injury causation and treatment. Thorough documentation of the device involved, including lot numbers and explant analysis when available, strengthens claims substantially. Patients who believe they were harmed by defective medical devices should consult with attorneys experienced in product liability litigation to evaluate which defect theories best apply to their circumstances.