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Best Practices for Human-Centric Design of Medical Devices

Best Practices for Human-Centric Design of Medical Devices
Digital engineering and simulation are delivering results—yet physician and patient input remain critical to realizing successful product development.

Medical devices designed to accommodate human variability present a growing opportunity for the healthcare and life sciences industries. Historically, medicine has solved many of the “simple” issues first: how to fix a broken leg has been known for centuries! But today we have treatments that didn’t even exist a generation ago, such as the use of stents and replacement valves for heart disease. These devices address a more limited cohort of people and are most successful when designed to be patient-specific. The cohorts themselves must also be further defined to account for differences in things like age and gender.

Splinting broken bones reliably relieves suffering, but more sophisticated techniques are essential for delivering many of the advanced medical solutions available today. For the device manufacturer, the path to best practices has become smoother: computer-aided engineering and simulation are shortening product design and development cycles, enabling more precise patient customization and accelerating submission and approval.

FDA is now strongly supportive of applications that include simulation data documenting efficacy and durability, while the ASME V&V 40 committee and ISO continue to fine-tune and align requirements to ease the path through verification and validation of computer models. Many of the medical devices that are currently being regulated, and particularly those with in-vivo durability questions around them, were developed with the help of computer simulation. Coronary stents, aortic heart valves, mitral valve replacements—as well as hip, knee, and spinal implants—all have robustly defined fatigue characteristics that were developed using digital design tools ahead of bench and animal testing, regulatory approvals, and patient trials.

Even more innovative designs, ones that straddle the line between medical devices and lifestyle, are already in the pipeline. Wearables that alert patient and doctor of an oncoming heart attack are in use today. In the future, pediatric heart implants will be made from material that “grows” and adjusts to a child’s changing biology so repeat surgeries can be avoided. Often AI-linked, such “smart devices” and implants will require sophisticated, embedded sensors—ones that need to be designed to adapt during use, as well as verified for function and durability.

Why Digital Design?

Such advances are simply not possible without digital tools, which deliver efficiency as well as innovation. The ability of computer simulation to compress the product-design cycle can provide significant cost savings over traditional physical prototyping and bench testing.

Using simulation forces the design engineer to think about their product in ways that might not have occurred to them when working with CAD modeling alone. Physical testing of a prototype device can provide answers to such questions as how to hold it properly, how far it can be bent before it breaks, and how many times it can be operated before wearing out. However, the time required to accumulate enough data can be weeks or months, and any subsequent design changes must repeat back through lengthy development cycles.

Digital simulation, on the other hand, virtually guides such inquiries throughout a product’s design, enabling innovation on the fly and ensuring its quality. Able to represent the physical characteristics of the very material from which the device is made, simulation predicts how the product will behave under whatever multiphysics are present in the environment in which it must function, thus revealing the full range of loading that’s possible as it’s used with different body types.

The clincher is that digital engineering can deliver hundreds and thousands of simulated tests in a matter of hours or even minutes, incorporating whatever parameters the designer wants to optimize in the final design. With simulation, you can interrogate every design challenge throughout your device, contemplate problems more deeply, and address things not visible that might happen beneath the surface.

While simulation is always an approximation, it’s highly reliable. The accuracy of current simulation software has been demonstrated across a wide range of industries. Real-world testing must always follow the digital, but the device put into the test rig will already be far closer to optimal when it’s been designed with the help of digital tools.

Patient Specificity, Innovative Implants

Patient data is clearly an important input for many medical-device simulations and essential for customization of devices. When accommodating human variability is the goal, patient scan data (CT, MRI) can be incorporated into digital models to provide highly accurate quantification and prediction of the interaction of a specific living body with a medical device. Through digital manipulation of such models, the design engineer can virtually try out every alternative in an automated product design and development workflow and arrive at patient-specificity in just hours.

Above: Patient-specific simulation of implantation of a hip-replacement device. Image courtesy Thornton Tomasetti Life Sciences

Capable of producing robust, end-use parts, industrial additive manufacturing (AM), also known as 3D printing, has been of particular benefit to the medical device industry. Among the most visible examples of this are sophisticated lattice structures that reduce implant weight and support osseointegration for joint, spine, and skull-plate implants. Advanced computational engineering software that enables generative design and topology optimization can now communicate the extremely complex geometry of such designs to additive manufacturing machines that have reached an astounding level of precision and quality control.

Above: 3D-printed medical devices on an additive manufacturing machine build platform: spinal ALIFs, tibial trays, and acetabular cups. Image courtesy nTopology and Tangible Solutions

Of course, less-complex devices that can be produced in quantity via more traditional manufacturing methods still demand flawless design as well. Today an existing product can be improved with a minor change that can be validated with simulation without the need for new clinical trials. Digital engineering can also provide an essential toolkit for analyses such as multiphysics flow simulation studies that identify the optimum syringe-needle design to reduce injection pain, or the analysis of the effects of stress and temperature on the function of an electromagnetic heart pacemaker.

Above: Three-dimensional model of needle penetrating skin simulates the body’s reaction at the entry point of an injection of fluid via syringe. Image courtesy Thornton Tomasetti Applied Sciences.

Benefits to Patients and Manufacturers Alike

There are many benefits that can accrue to a medical device manufacturer that makes the move into digital design tools.

When product design goes well, it’s the best of all worlds, and patients and manufacturers benefit. But if a device fails, even in the pre-clinical stage, the manufacturer is already falling behind. Errors aren’t identified until the last minute, without much insight as to what went wrong in early development. Identifying how something fails is critical toward solving the problem so that it doesn’t fail in the future. Proving out an innovative design idea early in development, away from any patient, is advantageous on many levels.

An additional benefit is the ease with which digital data can be captured and stored. When you work in a digital environment, your knowledge accumulates throughout product development, and it can be shared from one study to another, from one experiment to another, much more efficiently.

Interestingly, these advantages accrue to large and small medical device companies equally; we’re already seeing instances where smaller, agile startups are becoming capable of competing with the big guys in certain specialties. The advent of affordable, high-performance computing resources now allows the user at any size company to efficiently run the very latest digital tools on a single desktop—or collaboratively with a team on the cloud. Such methodologies make human-centric design more affordable for device manufacturers and patients alike.

Communication with Physicians

It’s important to keep in mind that the final proof-of-worth of widespread computer-simulation technology in the medical device industry is physician acceptance of the value of these digital tools. Challenges remain here: There is inertia in the system of scientific advancement that favors sticking with historical, experimental testing protocols. Resistance to a perceived shift to an “all-digital” world remains.

But the idea that it’s an all-or-nothing, digital-versus-experimental choice is a false dichotomy. The digital design-and-development cycle still needs to be fed with clinical data—and physician insight. Doctor and patient experience must both be integrated into the complete digital vision. Communicating this truth to medical professionals is greatly enhanced when medical-device salespeople have the visual tools, provided by “realistic simulation” software, that demonstrate device function to highly tactile people like surgeons.

Physicians who’ve then been convinced to “cross the chasm” to explore and embrace digital tools are finding new resources that bolster their diagnostic and treatment powers. One highly experienced surgeon, after viewing a Living Heart computer simulation, was heard to say that it made him look at his own decades-old operating-table techniques with fresh eyes. He was better able to teach his medical students the fine points of cardiac structures and disease when they were looking at an animated, 3D model of a beating heart. Software modeling also helps the physician explain to the patient which course of treatment will best treat their ills.

Resources for Device Manufacturers

Medical-device companies may need support with this kind of critical physician communication—as well as their own challenges with bridging the gap between older, less efficient design-and-manufacturing resources and the newer, more powerful ones. Here’s where experienced, software-agnostic consulting companies, which provide access to every digital-tool brand available, can bring to bear the full range of expertise needed to achieve a smooth transition to the digital product-development universe. Remote or on-site training can teach device makers how to best employ those visually compelling 3D onscreen displays of their device designs in action to spur acceptance and build sales.

The major engineering software vendors have created platforms that promise to deliver complete packages, many of which are excellent, but may still have a significant learning curve. And some device makers already have their own favorite tools and want to retain their independence and flexibility or to turn to specific, open-source solutions. This is where independent engineering consultancies can help tailor the optimum, integrated mix of available digital tools fine-tuned to a company’s specific needs. While there is much value in the leading platforms, and all software has grown increasingly user-friendly, it still helps to have specialists on board who can help imagine—and then realize—the applications that will optimize medical-device development for each company, from design, simulation, and data management, to regulatory submission.

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