Live from NASS: Solvay Advocates for Metal to Plastic Replacement in Medical Devices

Solvay S.A. has a storied history. The Belgian chemical company was founded in 1863 by Belgian chemist Earnest Solvay—though the company is now publicly traded, the founding family still has a major stake in the company, and the culture of history and family remains strong throughout the now 29,000-employee strong workforce. The Solvay Council, which first met in 1911 to discuss the “preeminent open problems” physics and chemistry, still meets today approximately every three years. The first gathering counted Marie Curie and Albert Einstein among its attendees at the International Solvay Institutes. Last year? Stephen Hawking.

The company strives to be at the forefront of science, and American subsidiary Solvay Specialty Polymers USA LLC is focused on creating single use, disposable, and/or reusable versions of surgical tools that have been traditionally made from metals.

At the North American Spine Society (NASS) Annual Meeting in San Francisco, Calif., Solvay had Hohmann style hip retractors on display made from polyarylamide (PARA), as well as a stainless steel version of the retractor for comparison. Solvay’s formulation of PARA is called Ixef, and the compound is reinforced with glass for high performance capabilities. In order to compete with metal, the material is highly rigid and flowable for ease of manufacture.

Solvay recently developed several case studies designed to demonstrate the cost and performance advantages of high-performance polymers over metals in medical devices. The Hohmann hip retractor was chosen as the sample device because it is widely used in its metal version. It also presents specific requirements such as the ability to withstand high mechanical loads.

“A major market trend has been cost reduction,” Dane Waund, specialty polymers global market manager, healthcare, for Solvay, told ODT at NASS. “There’s no question that plastic can be a good vehicle to reduce the cost of instrumentation in many ways. For instance, it can allow mass production where metals can’t. A lot of metal work is done with more of a job-shop mentality, which fits some markets, but spine and orthopedics markets typically need 200-500 parts at a time versus thousands.”

Making plastics an attractive replacement for metal in the medical field is a tall order, as the strength, rigidity, and wear resistance of metals are highly proven and trusted. As Waund described it, some surgeons view alternative materials with the same suspicion as a wine enthusiast would view drinking wine from a plastic bottle. Cost savings are certainly attractive to hospitals, but surgeons who are focused on what’s best for the patient and what they are most comfortable using need a little more convincing.

It turns out that that’s not hard to do. According to the latest data from the Centers for Disease Control, on any given day, about 1 in 25 hospital patients has at least one healthcare-associated infection (HAI). There were an estimated 722,000 HAIs in U.S. acute care hospitals in 2011. About 75,000 hospital patients with HAIs died during their hospitalizations. More than half of all HAIs occurred outside of the intensive care unit. HAIs have been on the rise. Single use devices that provide extremely significant cost savings (the stainless steel retractor rang up at $370 compared to the Ixef version’s $7.50) also remove the need for re-sterilization after use, thereby contributing to reducing the risk of HAIs from surgery.

Solvay also has a firm foothold in implantable polymers, which require the highest safety, biocompatibility, and sterilization standards. The company’s most recent success was announced on Nov. 12 at NASS: Salem, N.H.-based Thompson MIS earned 510(k) clearance for its Bonebac MIS TLIF (transforaminal lumbar interbody fusion) spacer made from Solvay’s proprietary PEEK (polyetheretherketone) material, Zeniva. Zeniva is part of Solvay’s Solviva family of biomaterials, which are used in spine, orthopedics as well as cardiovascular implants, and can withstand commercial sterilization methods such as gamma radiation, ethylene oxide and steam.

“The ability to completely fill the disc space after the device has been positioned is important for high-quality fusion,” said Dan Farley, president of Thompson MIS. “The spacer is an important element of the overall system because it empowers the adoption of minimally invasive surgery techniques by spine surgeons for TLIF.”

According to Thompson MIS, Zeniva PEEK is a comparable alternative to metals such as titanium for these intervertebral implantable devices. As well as being biocompatible, the material is also chemically inert (not a property usually associated with commercial plastics), and has shown no evidence in testing of cytotoxicity, sensitization, irritation, or acute systemic toxicity. The material also has high strength and stiffness properties, and is radiolucent, which enables X-ray procedures without interference.

“We’re excited about the commercial success of Zeniva PEEK in the spinal fusion market,” said Shawn Shorrock, global director of regulatory affairs for Solvay Specialty Polymers’ healthcare business. “The ongoing acceptance of Zeniva PEEK has validated our approach to the spinal market and we’re encouraged by the momentum we’ve generated.”

PEEK has become the most common polymer used for implants, so like metal in instrumentation, it is proven and trusted. It is commonly used in spine applications because of its similarities to cortical bone. However, in cardiovascular or neurological applications for instance, materials such as polysulfone (PSU) are better suited. Solvay’s proprietary PSU for implants is Eviva, and it offers toughness as well as transparency. French company Sophysa began using Eviva in October for its implantable brain shunt valves and access ports.

Solvay Specialty Polymers is based in Alpharetta, Ga., where most of its biomaterials are produced.