Israeli researchers refine coating process for metal orthopedic implants

A Tel Aviv University (TAU) research team has developed an electrochemical process for coating metal implants that may improve their functionality, longevity and integration into the body.

Noam Eliaz, PhD, of the TAU School of Mechanical Engineering, presented the findings at the 215th Meeting of the Electrochemical Society in San Francisco. In addition, a new 12-week implantation study, recently published in the journal Acta Biomaterialia, favorably compared the performance of the Tel Aviv University coatings to those of current commercial coatings.

In joint replacement cases, implants are often coated with synthetic hydroxyapatite in order to better integrate the new implant to the adjacent bone. The hydroxyapatite is similar to the main inorganic constituent of enamel, dentin and vertebrate bone. The properties of this coating are crucial to the function and life of the implant in the body.

Eliaz’s advance is in the application technique of the coatings rather than the elements used in the coatings themselves. Instead of plasma-spraying the coating onto the metal, the metal implant is placed into a bath of electrolyte solution and an electric current is applied, according to the press release.

Eliaz said a good coating is crucial to the stable fixation of the implant in the surrounding bone. Since human bones naturally contain apatite, covering the implant with a synthetic version allows the body to register the implant as similar to a real bone. This ensures integration and fixation of the implant, and also prevents poisonous materials from leaking from the metal of the implant into the bloodstream, he said in the press release.

Eliaz discovered that the electrochemical process allows synthetic hydroxyapatite to more closely mimic the real material. Examined under a microscope, it is virtually indistinguishable from the body’s own material, which helps the body accept a new implant, he noted.

The next-generation coating will include nanoparticles to reinforce the coating. It will also have the potential to incorporate biological material or drugs during the process itself.

“We can incorporate biological materials because the electrochemical process works at lower temperatures,” Eliaz said in the press release. “The reinforcement of nanoparticles will improve the mechanical properties and may also improve the biological response. Drug incorporation may reduce the risk of postsurgery infection and even catalyze the growth of the bone.”