Legacy Device Equivalence Reassessment: Why the MDR Bar Is Higher Than MDD

The equivalence route looks the same but the bar has moved

Many legacy devices were certified under MDD on the basis of equivalence — demonstrating that the device under review was similar enough to a predicate device that clinical data from the predicate could be used to support the safety and performance conclusion. Under MDD, this was a reasonably accessible path. Under MDR, the conceptual framework is the same but the practical requirements have tightened substantially in ways that disqualify many MDD-era equivalence claims.

The three-dimensional equivalence test — technical, biological, and clinical similarity — was present under MDD too. The change under MDR is the level of evidence and documentation required to demonstrate each dimension, and the addition of a specific access requirement for devices not made by your own company. If your legacy CER relied on equivalence, your first task in MDR transition is not updating the document — it is reassessing whether the equivalence claim can be sustained at all.

Technical equivalence: what "similar design" now requires

Under MDD, technical equivalence was often established by a narrative comparison of device characteristics — dimensions, materials, coating, mode of operation — supported by a brief review of technical documentation. Under MDR, the technical similarity demonstration needs to be more rigorous. You need to show that the devices use the same materials in contact with the same biological tissues, that the design produces the same physical or physiological effect, and that the technical operating principles are the same.

The key test is whether any technical differences between your device and the predicate could influence the clinical performance or safety profile. If there are differences — and there almost always are between device generations — you need to explicitly address whether those differences are clinically meaningful. A difference that is "minor" from an engineering standpoint can still be clinically significant. Many MDD equivalence claims were built on comparisons that would not survive MDR scrutiny because the differences were acknowledged but not analysed for clinical impact.

Biological equivalence: materials are not interchangeable

Biological equivalence under MDR requires that the devices use the same materials, or that materials in contact with the same human tissues be demonstrably equivalent in terms of biocompatibility profile. "Equivalent grade" materials that are technically different — a different polymer formulation, a different surface treatment, a different coating composition — require biocompatibility data to support equivalence, not just a material specification comparison.

This is where legacy devices that have had component changes over time often run into trouble. If your device has had a material substitution since the predicate was characterised — even a substitution that was handled as a minor change under MDD practice — the biological equivalence leg of your MDR claim needs to address that change explicitly. If biocompatibility testing was done for your own device under ISO 10993, use that data to establish your own clinical basis rather than claiming equivalence via the predicate's biological profile.

The third-party equivalence problem

The change that closes the equivalence route for most manufacturers dealing with competitor predicates is Article 61(5) and (6) of MDR. For devices not manufactured by your own company, demonstrating equivalence now requires a formal contract between your company and the other manufacturer that explicitly grants you access to their technical documentation. Without this contract, the equivalence claim cannot be substantiated under MDR, regardless of how similar the devices are.

Most manufacturers of equivalent competing devices are not willing to enter into such contracts. The contract would give a competitor structured access to their confidential technical file — something that carries obvious commercial risk. As a result, the third-party equivalence path is effectively closed for the vast majority of devices where the predicate is a competitor's product. If your legacy CER relies on equivalence to a competitor's device, this is a hard block, not a documentation gap.

The exception is where you own both devices — a common situation where an acquired product relies on equivalence to a device from the acquiring company's portfolio, or where an own-brand and a co-manufactured OEM version reference each other. In these cases, contract access is achievable and equivalence can be maintained under MDR.

Deciding your path forward

Once you have assessed whether your equivalence claim is technically, biologically, and documentarily sustainable under MDR, you have three practical options.

Sustain the equivalence claim — if your predicate is your own device or a device from your own company's portfolio, and the technical and biological similarities hold under MDR scrutiny, the equivalence path remains open. You will need to rebuild the equivalence documentation to MDR depth, update the clinical data comparison, and confirm that the PMCF plan addresses any remaining questions about performance gaps between the devices.

Pivot to own-device data — if your device has been on the market for several years, you likely have post-market surveillance data, complaint data, and possibly registries or published literature on your specific device. Many legacy devices have enough accumulated clinical experience to support an MDR clinical evaluation without equivalence — the CER can be restructured around your own device's data rather than a predicate comparison. This route requires a more substantial clinical data package but avoids the equivalence access problem entirely.

Initiate a PMCF study — if your device does not have enough post-market data to support an MDR clinical evaluation independently, and equivalence is not available, the path forward is to design and initiate a PMCF study that generates the clinical evidence you need. This is the longest path and has the most direct timeline impact. If this is the route for any of your legacy devices, it needs to be built into your transition plan with realistic timelines — a PMCF study that follows patients for a clinically meaningful duration adds two to four years to your evidence generation timeline, not six months.

Where this fits in your transition programme

Equivalence reassessment is not a step you can defer to the end of your MDR transition. It is the decision that gates everything else in your clinical workstream. If equivalence is not available and your own data is thin, you need to know that early enough to initiate a PMCF study while your MDD certificate still gives you time to collect data. Discovering an equivalence block six months before your transition deadline is a situation with no good options. Map your equivalence status across your full portfolio early and treat any devices with uncertain equivalence as requiring immediate attention.