By Sean Fenske, Editor-in-Chief

MRI has become one of the fastest-expanding diagnostic technologies in modern healthcare, with a compound annual growth rate of around 5% in recent years. Installations of MRI across Organisation for Economic Co-operation and Development (OECD) countries have increased significantly over the last decade, and demand continues to surge as imaging capabilities advance and accessibility improves. At the same time, the world’s population is ageing—22% of people are expected to be over 60 by 2050—a demographic shift that is closely tied to an increased need for orthopedic implants and advanced imaging.

Consequently, more patients with orthopedic implants are entering MRI environments than ever before. This makes MRI safety a rapidly growing priority and a strategic opportunity for orthopedic device manufacturers.

To address what companies need to keep in mind when developing devices to ensure safety and compatibility with MRI, Thomas Eigentler, Dr.-Ing., Senior Product Specialist MRI Safety at TÜV SÜD, took time to respond to a series of questions. In the following Q&A, he speaks to the concerns and opportunities involved, material considerations, and best practices for development.

Sean Fenske: Can you please explain the general concerns regarding an MRI and orthopedic devices and implants? What are the MR classifications for devices?

Dr. Thomas Eigentler: Non-active orthopedic implants interact with all three MRI field types (i.e., static magnetic field, gradient field, and radiofrequency field). Considerations can be divided into two categories for non-active orthopedic implants: mechanical hazards and heating hazards. Mechanical hazards include magnetically induced force, torque, and gradient‑induced vibration. Heating hazards include RF‑induced heating and gradient‑induced heating.

When it comes to orthopedic devices, it is of pivotal importance to consider all device combinations to fulfill the intended purpose (e.g., plate-screw combinations). While the combination of devices is important for all hazards, the heating hazards provide a critical element in providing evidence for hazard control due to their non-linear and, often, unpredictable behavior. Due to the potentially high number of combinations, metrological testing of each combination is often economically not feasible. Hence, a worst-case device identification or representative (artificial) model may be used as a step to reduce the number of metrological tests. This worst-case device identification or representative model is integral to the documentation of evidence required for market access globally.

Devices are labelled according to ASTM F2503 to communicate use with MR Safe, MR Conditional, or MR Unsafe, with orthopedic implants almost always falling under MR Conditional because their safety depends on specific scanning conditions. From a regulatory perspective, MR labeling forms part of the device’s safety information and must be consistent with the risk management process and instructions for use in accordance with applicable regulatory frameworks (e.g., EU MDR or FDA requirements).

Fenske: How would a patient know if their device or implant could cause a problem during an MRI?

Dr. Eigentler: Patients should be informed about this before an implantation procedure to enable them and their physicians to select the most appropriate device and avoid withholding any imaging modalities in the future. Often, time passes between implantation and the MRI examination, so the patient’s knowledge plays an essential role in risk mitigation in the radiology department. Standard operating procedure in radiology departments is usually to ask the patient if they have any implants. If the answer is affirmative, an MRI scan is usually contraindicated, unless otherwise indicated. To overrule the contraindication, documents are supplied by the manufacturers and may include a patient information card directing the radiologist or prescribing physician to the device instructions for use, and in some cases, to an MR guideline.

In summary, knowledge of the presence of an implant is currently primarily in the patient’s hands. Nevertheless, there are new and promising developments in detector systems and even communication elements, enabling improvements in patient safety.

Fenske: Are certain metals or materials the source of a concern more so than others? Are there safe orthopedic implant metals (with regard to MRI)?

Dr. Eigentler: Generally speaking, the answer is “no.” By definition, metallic implants cannot be rated as MR Safe. However, there are certainly considerations that apply to the design and development process to reduce the risks as much as possible. Ideally, non-metallic materials would be used, but this is often not possible due to other mechanical concerns. Therefore, the focus should be on devices that are as weak as possible regarding the magnetic properties. Additionally, it should demonstrate low electrical conductivity to reduce heating interactions through electrical fields. In terms of materials alone, titanium alloys tend to interact less with MRIs (i.e., mechanical and heating) than cobalt chromium and stainless-steel alloys.

However, the design of the device with respect to its contours is of equivalent importance, and in most cases, it is even more important. A good approach is to avoid sharp edges and RF-wavelengths (in tissue) size dimensions to reduce RF heating effects. Furthermore, large electrically conductive surfaces and volumes to reduce gradient heating effects should be avoided whenever possible. Of course, this is not always possible, as the device requires certain dimensions, but breaking up electrical pathways might be feasible in the device design process without undermining the intended purpose.

Fenske: Can you explain what category gradient-induced interaction means? How can this impact the implant/MRI encounter?

Dr. Eigentler: Gradient-induced interactions stem from time-varying gradient magnetic fields of the MRI system, which are essential for spatial encoding. According to Faraday’s law, changing magnetic fields induce electrical fields and currents within conductive implants. This can lead to vibrations or mechanical oscillation of the implant, as well as gradient-induced heating, particularly in larger metallic components.

While the physical nature of gradient-induced effects and RF-induced heating is analogous, their interaction differs with field frequency: RF operates in the MHz range, whereas gradients operate in the low kHz range. Although requirements regarding gradient interactions are documented in state-of-the-art standards, these considerations are often overlooked in evidence reports in market access processes. This oversight may increase the likelihood of regulatory challenges and delay the introduction of MR conditional devices into relevant markets.

Fenske: You’ve mentioned the heating concerns involved with MRI and orthopedic implants. Can you expand on this and what the concerns are?

Dr. Eigentler: Heating interactions are the most significant concern for orthopedic devices due to the material and design characteristics (e.g., metallic materials and sharp edges in screw tips as well as large conductive surfaces and volumes). Heating interactions are based on the time-varying electric fields in an MRI system. These electric fields are a physical by-product of the time-varying magnetic fields required for imaging (see Maxwell’s equations).

This electric field results in RF heating, in which the field increases near the implant and increases power deposition in the surrounding tissue, resulting in tissue heating. In this case, the medical device can be understood as an antenna system collecting the electric fields. For gradient heating, the main contributor is the electrical induction from the medical device itself, where current flows through the implant, resulting in heating due to electrical material resistance.

Fenske: Can you share a strategic approach for orthopedic device makers to ensure their products are safe during an MRI? What steps should they take and when should these take place?

Dr. Eigentler: Successful MRI safety starts early and follows a clear, structured path. In-house personnel and equipment capacities are often limited due to the highly specialized field and the relatively low number of tests compared to other device-specific test modalities. Therefore, establishing a project plan and navigating the requirements through early partnering is essential. Even pilot testing can be used in the early development stages to ensure frictionless testing and ultimately meet the go-to-market date, as every day of delay results in significant financial risk due to lost revenue and market share.

A structure of milestones with respect to MR testing might be:

• Integrate MRI considerations early in the design process—Early awareness can help to avoid costly redesigns and geometry‑driven heating risks. In this respect, a test laboratory can help with cost-efficient comparison studies, for example.
• Identify representative worst‑case configurations—For modular systems, worst‑case selection ensures economic efficiency of testing while guaranteeing the safety of the entire product family. This is potentially the most critical part of orthopedic devices, as they pose the highest risk of requiring feedback during regulator reviews and thereby jeopardizing market access timelines.
• Use modelling and simulation to refine designs—Electromagnetic simulations highlight hotspots and guide design improvements. They are also the state-of-the-art tool for identifying worst-case devices/models in cases where scientific rationales before physical testing begins are ambiguous.
• Conduct state-of-the-art aligned testing—Addressing the risks connected to the devices in an MR environment is the key to identifying the correct testing path. A test laboratory can support the identification of the correct path at a device-specific level. It is important to note that a list of tests according to the ASTM family is often insufficient and may jeopardize the market access date.
• Create clear, user‑focused MR conditional labeling—Radiologists need straightforward, actionable conditions they can apply with confidence. This information is cross-checked against the boundary conditions and results of the applied tests, and is an essential element of the regulator’s ambiguity check.
• Maintain post‑market connectivity—Vigilance obligations cover regulatory requirements as well as reducing business risks through reputational damage. Furthermore, feedback can support improvements to future products and ensure long-term MR safety.

When MRI safety is integrated as a tool to increase market positioning and relevance—thereby becoming a design specification, not a regulatory checkbox—it adds value for all market stakeholders and the manufacturer through high-value products.

Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell orthopedic device manufacturers?

Dr. Eigentler: MRI is not just a diagnostic tool; it’s one of the fastest-growing and most relied-upon imaging modalities in modern medicine. This growth directly increases the likelihood that patients with orthopedic implants will require an MRI scan, making MRI safety a strategic priority for every device manufacturer.

Today, MRI usage is extensive and still growing:

• MRI is the fastest-growing imaging modality, with a sustained CAGR of ~5% since 2019.
• Every year, the number of MRI scanners increases, with ~5,000 new systems sold worldwide.
• Some regions perform an exceptionally high number of scans—for example, the United States and Germany recorded 110 and 160 MRI exams per 1,000 people, respectively, more than double the OECD average of ~50 exams per 1,000 (data of 2021, with growing tendency).
• As the world population ages, demand is expected to increase dramatically: By 2050, 22% of the global population will be over 60, nearly doubling the percentage from 2015. This demographic shift is closely linked to higher implant prevalence and MRI utilization.

For orthopedic implant manufacturers, these trends mean one thing: Your implants will end up in the MRI environment more often, for more patients, and under more varied scanning conditions than ever before.

Patients with joint replacements, trauma hardware, or spinal implants often require an MRI scan to evaluate pain, sports injuries, neurological symptoms, cancer staging, and general age-related conditions. Globally, it is estimated that 60% of MRI scans are musculoskeletal, making orthopedics one of the most dominant use cases for MRI.

This growing demand creates both clinical responsibility and a market opportunity. Manufacturers who invest early in MRI-aware design, validated worst-case analysis, and clear labeling not only reduce regulatory risk, but also enhance product appeal and increase market share.

In today’s market, MR testing is not a burden. It’s a competitive advantage.

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