Orthopedics covers a wider technology range than ever before. New materials are improving outcomes while some implant designs are tapping into consumer electronic technologies. There are also external devices that hold off the need for total joint replacement. This article will take a look at some of the latest and greatest development in each of these areas.

 

New materials raise the odds

A titanium-based anterior lumbar interbody fusion (ALIF) device by Titan Spine (titanspine.com), Mequon, WI, was developed to improve the body’s acceptance of spinal implants. “Most spinal implants are manufactured using polyetheretherketone (PEEK),” says CEO Peter Ulrich. “PEEK predominately generates fibrous tissue rather than the desired bony tissue.

“Our macro surface functions as an anti-expulsion surface without damaging the vertebral end plates,” continues Ulrich. That allows the implant to resist migration. The next level is at the micron scale, which is 10-6 m. It gives cells a place to grow into the implant. The most important level is at the sub-micron scale, or 10-9 m. This actually triggers the cells to differentiate into osteoblasts and begin the bone formation process. This is all triggered by the topography of our implant surface.”

Ullrich says Titan Spine’s research indicates that about 90% of bone growth will be complete within six weeks. “We have had spinal implant patients go back to manual labor in six weeks. This was unheard of before.”

Amedica Corporation (amedica.com), Salt Lake City, UT, is also devoted to the development of a unique orthopedic implant material. CTO Bryan McEntire says that they explored a range of materials for potential use in spinal implants before focusing on silicon nitride (Si3N4).

Amedica’s transforaminal lumbar interbody fusion (TLIF) devices provide mechanical stability to the spine. “In spinal fusion surgery a damaged disc is removed and replaced with an implant, which provides a vertical space between the upper and lower vertebrae, eliminating the pressure on the nerve roots. In time, the two segments of the spine grow together, fusing in and around the implant,” says McEntire.

“Unlike PEEK, surgeons can place silicon nitride implants very precisely because its X-ray transmission characteristics are similar to bone, making it easy for the surgeon to see,” explains McEntire.

Silicon nitride is not only biocompatible, it is also “biofriendly,” says McEntire. “Bone likes to grow right up to it. In a porous form, the bone will grow right into the device. Another significant benefit of silicon nitride is that it has inherent antimicrobial action that resists the formation of surface biofilm. Infection-related problems in spinal surgery range from two to as high as 16% and can be alleviated using silicon nitride implant material.

“Amedica’s interbody fusion devices have proven safe and effective in more than 11,000 surgeries at this point. We are in the early stages of developing silicon nitride hip and knee implants,” says McEntire. “Silicon nitride has a very hard and wear-resistant surface. We believe it will provide improved longevity over materials that are presently used for these devices.”

Implant innovation improves movement

As many as 20% of knee-replacement patients are not completely satisfied with their knee replacements, according to Hannah McEwen, worldwide director for knee product development at DePuy Synthes Joint Reconstruction, a division of DePuy Orthopaedics, Inc (depuysynthes.com), Warsaw, IN

Such outcomes prompted DePuy to embark upon its largest-ever R&D project. Collaborating with industry leaders such as the University of Kansas and the University of Denver, DePuy made discoveries about the interaction between how the knee is designed and how it affects motion and stability.

“By observing patients, we could see how their total knee replacements were behaving and then we used cadavers to test different designs and do computational models,” says McEwen. “We were able to identify how changes in implant curvature could lead to unstable motion. As a result, our Attune Gradius Curve technology,has a gradually reducing radius, similar to that of a seashell. The design provides optimum conformity throughout the range of motion to achieve anterior and posterior stability.”

McEwen adds, “We discovered that even a single millimeter in size, shape, or thickness has an impact on the stability and motion of a knee implant.”

The Attune knee is designed to be used with the DePuy Intuition instruments. McEwen says using composite material made these instruments light weight, and also allowed for the use of high-contrast marking to indicate positioning and sizing.

“We currently have more than 8,000 Attune implants in patients in countries around the world, and have been receiving positive clinical feedback regarding recovery, stability, and motion.”

‘Smart’ implants coming soon

Much of the innovation at OrthoSensor (orthosensor.com), Sunrise, FL, has to do with advances in consumer electronics. CEO Jay Pierce explains that OrthoSensor’s  first step in developing a smart, single-use device was to build a core technology platform. Then it selected Stryker Orthopaedics (stryker.com), Mahwah, NJ, to test the device.       

“Stryker gave us the geometric designs and CAD files for their reusable plastic tibial insert and we developed an intelligent disposable device to their specifications,” says Pierce. “All of the microelectronics and sensors are packaged in a polycarbonate shell. We put in the PCB and sensors on the medial and lateral side, packaged it, sterilized it and Verasense was born.

“Verasense feeds information to a graphic user interface (GUI) on an iMac computer, giving the surgeon the data needed to correctly balance and align both the leg and the knee implant for optimum success,” says Pierce. “The same technology platform will be our basis in building intelligent implants.”

“The ASIC (Application Specific Integrated Circuit) is what enables low power miniaturization with multiprocessing,” explains Pierce. “For a truly intelligent future implant, first comes the design of the smart chip that will be able to measure all post-operative loads. An RF chip will wirelessly move data from sterile field in surgery and link it to a database. We want to eventually take data from a patient’s smart knee, move it out of the patient’s home wirelessly, and integrate it into the Cloud.

“Integrating advanced sensors into implant material needs a lot of testing to make sure that nothing has a negative impact on the implant itself. We are now deciding which type of implant to go with first; in 12 to 18 months we will be doing clinical studies.”

Keeping patients in the race      

The biggest challenge with any external brace is getting people to wear it. That challenge was addressed by DJO Global’s (djoglobal.com), Bracing & Support business unit, Vista, CA.  President Steve Ingel explains that his company’s OA Nano functional osteoarthritis (OA) knee brace relieves patients’ pain by offloading stress and providing stability to the damaged joint. The OA adjuster technology, he says, allows patients to customize their braces for their unique conditions.”

The OA Nano is made of a new material called nanoMAG  – a TTMP (Thixomolding Thermal Mechanical Processing) material – that is as light as magnesium, but as strong as aircraft grade aluminum alloys. “It weighs only 14.2 ounces,” says Ingel, who claims it’s the lightest such knee brace worldwide. “Patients say they feel as if they are not wearing a brace, which means they actually wear it. It is the fastest-growing product in our history.”

Two other DJO products complement the OA Nano. Empi Phoenix is a prescription electrical stimulator, and the recently introduced, Flex OA shoe is clinically proven to offload the knee by 20%, providing better alignment between the knee, hip, and foot.

 “Using a combination of our technologies helps keep knees and muscles healthy to avoid surgery. After a knee implant, the Phoenix works to strengthen the quad and aid in the healing process. But helping to put off total knee replacement as long as possible is one of the biggest benefits we offer.”

Ever-growing market

The Academy of Orthopedic Surgeons predicts that the demand for total knee replacement will jump 673% by 2030, and total hip replacement by 174%. Also, by 2030, an estimated 25% of the projected total adult population will have
doctor-diagnosed arthritis, accordig to the US Department of Commerce.

Stats such as these will continue to help drive innovation in what appears to be an ever-growing market for the foreseeable future.

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