Medical Device Daily Washington Editor

WASHINGTON – At present, materials scientists have not come up with “load-bearing ceramics just yet, and that's the Holy Grail” of orthopedic science, according to Erik Erbe, PhD, chief science officer at Orthovita (Malvern, Pennsylvania).

Erbe was one of the presenters at a session last week hosted by the Congressional Research & Development Caucus and the Federation of Materials Societies (Washington), the gathering intended to offer insights into the new uses, and potential uses, of ceramic and bioceramic materials in healthcare and orthopedics.

Erbe told attendees that in the orthopedics space load-bearing ceramic materials will have to develop from “a formulation that is safe, effective, biocompatible and deliverable by surgeons.” And as with many other breakthrough products in med-tech, such a material, he said, will probably make it to market in Europe prior to arriving in American clinics.

Erbe reviewed aspects of his company's major products, Vitoss (described in Friday's Medical Device Daily article on the meeting) and Cortoss.

Erbe told MDD that Cortoss is “a bit more than half way (62%) through the enrollment of 243 patients in the FDA-approved IDE pivotal clinical trial” using polymethyl methacrylate (PMMA) for vertebral compression fractures brought on by osteoporosis. He said that the trial enrollment should be wrapped up by the end of this year, adding that this will likely be filed as a 510(k) rather than as a PMA.

“Cortoss has been used in Europe for five years,” Erbe said of the injectable, high-strength bioceramic/polymer composite.

Cortoss binds by means of ionic interaction with surrounding tissue. The company manufactures the substance in blocks to be shaped by the surgeon and in smaller pieces that can be fitted into an opening. The substance exhibits 90% interconnected porosity.

Erbe stated that in vertebroplasty applications, Cortoss is injected into the vertebrae, but that “such injections can be problematic” due to “marginal control over where the material flows, so you must inject under fluoroscopic control.”

Any substance that “polymerizes around or in [vertebrae] in a way that compresses these structures could trigger pain and/or paralysis.” He said that such incidents have occurred with the use of PMMA, but that Cortoss “has had no neuro or cord problems as it is easier to see and less viscous so even if it does leak it does not compress nerves.”

Erbe observed that stem cells may offer healing powers for even relatively inert tissue like bones, but that such promise was not quiet yet on the horizon.

“The orthopedic industry is evolutionary, not revolutionary,” he remarked, and stem cell research seems unlikely to supplant synthetic osteoplastic materials anytime soon.

Michael Hawkins, PhD, vice president of Warsaw Research (Warsaw, Indiana), discussed other clinical applications of bioceramics, the word ceramics derived from the Greek keramikos, or burnt material.

He reminded the audience that calcium phosphate is one of the base materials of bone, but that synthetic materials intended to replace bone are often easier to work with. “You can control the chemistry and configuration properties of synthetics much more easily” than natural bone, he said.

Ceramics are distinguished from metals and polymers by their combined ionic and covalent atomic binding, whereas the metals largely depend on so-called metallic bonding and polymers on carbon-covalent bonding. More than one kind of material is available for implants, and the traditional metal-on-metal joint replacement, while serving admirably as other materials matured, created at least one problem: “Some people are allergic to metal,” Hawkins noted.

And he underlined what has become a key market metric in the orthopedics space. “Orthopedic implants are going into younger and younger people” as a result of these converging trends, and the consequence of their use in younger patients is that “we're beating these devices to death.”

This means that in addition to the ever-expanding market for replacement parts in older people, younger people will more frequently need replacement of their replacement parts.

Hawkins described how, when joint replacements wear over time, they inevitably throw off particulate matter from the grinding action of movement.

Hawkins' chart indicated that a cobalt-chrome/polyethylene joint may throw off as much as 200 microns per year, opening the door to toxic effects. Metal-on-metal joints, despite the potential for allergic reaction, throws off only about 10 microns per year, but ceramic/ceramic joints can restrain particulate matter precipitation to less than one micron per annum.

He remarked that air bags in automobiles are a tremendous life-saving device, but that “one of the downsides is that we suffer from more severe injuries as a result,” especially to the legs.

Hawkins also noted that the expanding girth of the typical American is also putting tremendous pressure on the skeleton.

The meeting's sponsoring group, the Federation of Materials Societies (FMS; Washington), describes itself as an umbrella organization whose eight member societies, and their affiliates, represent the professional societies, universities and National Research Council organizations involved with materials science, engineering and technology. FMS constituent societies have more than 700,000 individual members.