Medthin™ coatings to minimize cobalt release from orthopedic and spine implants

Leaching of cobalt ions into the human body is a risk with medical implants made of CoCrMo. Ionbond’s Medthin™ coatings reduce cobalt ion release by more than 98%, substantially increasing implant safety. In addition, Ionbond also has Medthin™ coatings optimized for other implant materials.

Medical implants for long-term use in the human body have demanding requirements regarding load-bearing properties, biocompatibility, and corrosion resistance. CoCr₂₈MO₆ (better known as CoCrMo) has long been the material of choice in implant designs.

However, new labeling for CoCrMo indicates that this material can be carcinogenic, mutagenic, and reprotoxic (CMR cat 1B) [1], making it highly desirable to reduce exposure of the human body to this material. The main risk is metal ions leaching from the implant material and being released into the human body, particularly cobalt ions.

Figure 1: Ion concentration of fluids collected after 5m cycles in ISO 14243-simulator test.

Short-term preventive solutions

Immediately stopping the use of all CoCrMo implants, with no proven alternatives, is not in patients’ best interest. Instead, fully encapsulating the CoCrMo substrate material with a coating is a workable solution. Ionbond’s Medthin^™ coatings are capable of reducing the cobalt ion release into the human body by more than 98% [2,3]. With a 15-year successful track record, Ionbond has used and improved the physical vapor deposition (PVD) technology to efficiently block cobalt ion release.

Definitive solution replacing CoCrMo implants

Complete replacement of CoCrMo as a substrate material by a material without the CMR label, however, is the ultimate and most desirable strategy. Many implant OEMs have started R&D programs, using alternative materials for implant designs, such as titanium, stainless steel and zirconium niobium alloys. These alternative metals and alloys are less hard and less scratch resistant than CoCrMo. From a substrate material perspective, this new starting point needs to be taken into account when selecting or engineering a coating architecture.

Ionbond’s Medthin^™portfolio includes coatings to improve surface hardness and wear resistance of these newer generations of implants. In particular, the Generation III Medthin^™ coatings, deposited with hybrid PVD/PACVD technologies, are smoother and denser than the prior generation. These latest Medthin^™coatings further improve wear resistance and further reduce cobalt ion release from implants.

Figure 2: UHMWPE wear measured during knee simulator test according to norm ISO 14243-1.

[1] – labelling according to ISO 15223-1, section 5.4.10, part 1 page 21
[2] – Reich J, Hovy L, Lindenmaier HL, Zeller R, Schwiesau J, Thomas P, Grupp TM. Präklinische Ergebnisse beschichteter Knieimplantate für Allergiker. Orthopäde. 2010 Mai;39(5): 495-502.
[3] – Ionbond sponsored wear simulator tests used for Ionbond’s FDA master file MAF n. 1413 which supported various 510K - Test fluid samples obtained from ISO 14243-1 after 5 million cycles.

Would you like to know more about Ionbond’s Medthin™ coatings for your application? Contact Dr. Antonio Santana, Global Segment Manager Medical & Food. Antonio and his team would be happy to discuss the best options for your needs.