DePuy Synthes Revamps Approach to New Knee Design

Many of the changes in the medical device industry are incremental, iterative in nature. They happen slowly over time. Small changes are made as knowledge is gained about how devices work in practice, and then companies tweak designs year after year. That’s one of the numerous ways the medical device industry distinguishes itself from its cousins in the pharmaceutical arena–fewer blockbusters but more consistent, ongoing new product development and launches.

That’s all well and good, unless you’re on the team involved in new knee product development in the DePuy Synthes Joint Reconstruction division of Warsaw, Ind.-based DePuy Orthopaedics Inc.

During this year’s annual meeting of the American Academy of Orthopaedic Surgeons (AAOS) in Chicago, Ill. (held March 19-23), the DePuy Synthes booth was buzzing with news of the company’s latest release, the Attune total knee replacement system. Officials were on hand to walk the press, physicians, industry analysts and other invited guests through a special four-room display that included presentations about the effort undertaken to create Attune.

“Given that studies show 10 to 20 percent of knee replacement patients aren’t completely satisfied with their knee replacement, we dedicated a significant amount of resources to designing a knee that would help to address these concerns. The Attune knee is the result of our largest research and development project ever,” said Hannah McEwen, worldwide director for Knee Product Development, DePuy Synthes Joint Reconstruction. “To date, more than 3,500 patients have received an Attune knee as part of a limited launch and we’ve received positive feedback regarding patient recovery, stability and motion.”

It wasn’t hyperbole when McEwen noted that this was one of the company’s largest R&D undertakings. The project took more than six years and carried a price tag of approximately $200 million. The goal, according to McEwen and others, was to address unmet patient and surgeon needs. The new knee is designed to provide better range of motion and address the “unstable” or “wobbly” feeling some patients report during everyday activities, such as bending, going down stairs, or even something as routine as getting out of a car, officials said.

To achieve an improved feeling of stability for patients, the team at DePuy had to throw out convention and come up with a new implant that might at first glance appear to be the same as other knee replacement technology, but upon closer inspection differs from previous generations of devices in shape, form and function. It’s a tall order in a crowded market, with new knee implant offerings released at AAOS by competitors such as Zimmer Holdings Inc. and Smith & Nephew plc.

Through research collaboration with the University of Denver in Colorado and the University College Dublin (Ireland), researchers evaluated current knee designs to assess how implant geometry aids in maintaining stability through patients’ daily activities. An implant with a new shape employing what the company calls the “Gradius Curve” was the result.

The research—with a team of surgeons and industry experts from around the world working on the project—led to more than 19 patents for Attune as well as its related instrument technology. For example, the research and design teams spent more than 10,000 hours working with surgeons in different settings to get feedback and record data, McEwen said. That included ethnological research with doctors—filming them, studying movements and behaviors, and even looking for operating room efficiencies. Other research activities included X-rays of patient movement, extensive tests with cadaver knees and computer simulations.

Tim Czartoski, director of marketing at DePuy Orthopaedics, told Orthopedic Design & Technology during an interview at AAOS along with McEwen, that the effort to create Attune “mobilized the best talent in the organization and partnered with outstanding outside research organizations” to solve problems highlighted by research teams, patients and doctors.

“The process started with a blank page—no boundaries and no limits on what we knew from the past. It was really a new attitude and culture we had to create,” Czartoski added. “If we really didn’t make a difference, then why bother? Speed to market and quick revenue weren’t our first priorities. It was about creating game-changing technology and, as a result, better outcomes for patients.”

“We brought together a huge group of engineers and scientists and cross-functional teams that partnered with external research groups. Let’s understand the natural knee; let’s understand current total knee devices; let’s understand the science of how we can make the design changes,” McEwen added.

A lot of the process in creating Attune and its related instruments was about “taking the theory and the science and marrying it with with the feel, experience and art of the surgeon,” Czartoski said. “And so we’d see if our research assumptions played out, and we assessed the outcome. If they didn’t, we went back and started again. That was a three- to four-year period. There are lot of products out there today that are only designed with the surgeon experience without all the other in-depth research and development. We wanted to get beyond that.”

A number of patented technologies resulted from the research into the Attune knee. Attune’s Gradius Curve is described as a “gradually reducing radius” that is designed for improved conformity throughout the range of motion, providing better anterior/posterior stability. The Sofcam Contact is an S-curve designed to provide smooth engagement for stability through flexion, while reducing stresses placed on the implant. The Logiclock tibial base is a locking design intended to improve kinematics while reducing wear to what the company claims is “the lowest reported levels in the industry.” The Logiclock feature also gives surgeons the options to choose the best size and fit for each patient from a range of sizes, according to DePuy Synthes. The system’s Glideright Articulation is designed to accommodate patient variation and soft tissue interaction, while optimizing patella tracking.

As part of its many hours of Attune research and development, DePuy Synthes also developed a line of instruments branded Intuition. Like the knee itself, the design of the instruments also went back to the drawing board to make them—as the name suggests—more intuitive. The tools include lighter weight composite materials, color-coded technology, and easier-to-see gauges and measurements. Single-layer instrument cases are lightweight with fewer instruments, reducing weight by 51 percent as compared to previously available instruments. The instruments also minimize the number of cases in the operating room while maintaining durability.

When asked to pick some of the key lessons or surprises learned after going though this six-year process, Czartoski and McEwen agreed that “millimeters matter.” Small changes to the geometry of the knee design led to significant changes in outcomes.

In addition, Czartoski noted that the systematic process that was created to tackle the knee redesign was perhaps even more impressive than the knee itself.

“Our industry and our society so want to point one thing and say it makes all the difference. And, of course, Gradius is a big part of that for us. However, the other discovery that I believe we made is that you have to have an systematic approach that is integrated,” he explained. “So, the Logiclock leads to the matching of the insert to the femur, which leads to kinematics that match the Gradius, which leads to the box size, which leads to the patella femoral kinematics. When you have all these pieces working together, that’s synergy.”

Going forward McEwen and her time will use the lessons learned with Attune and apply them to upcoming projects.

“All good organizations are learning organizations and we’ll take the things we’ve learned here and apply it to new projects,” she said. “The tools we’ve developed will help us leverage the science and technology we’ve developed.”

In addition to the U.S. introduction (U.S. Food and Drug Administration approval and clearances were granted for the various parts of the Attune system throughout 2011 and 2012), DePuy Synthes plans to release Attune in select international markets later this year.

By Christopher Delporte, Editorial Director, ODT Magazine