Amorphous carbon as a bio-mechanical coating - mechanical properties and biological applications

dFor improving the bio-mechanical properties of articulated and solid implants diamond-like carbon (DLC) is a very promising coating material because it is chemically inert, extremely hard, wear resistant and biocompatible. These possibilities are reviewed. The high quality (sp(3)-fraction similar to 80%) hydrogen-free DLC coatings tested were deposited (5 mum/h per 20 cm(2)) with a filtered pulsed are discharge method. Adhesion problems were solved with proper plasma energy control and suitable intermediate lavers. With a hip simulator, loads up to 1300 kg on DLC-coated (50-200 mum) joints were used without failure. Under a 200-kg load the coefficient of friction was 0.05, 0.05 and 0.14 for DLC-coated, metal-polyethylene and metal-metal pairs, respectively. Diverse tribological tests show that the wear in DLC-coated metal joints is 10(5)-10(6) times lower than in conventional metal-polyethylene and metal-metal pairs. The wear of the plastic acetabular cup is reduced at least 10 times if the metal ball of the joint is coated with DLC. On a commonly used CoCrMo alloy 1 mum DLC decreased the corrosion rate of the substrate by a factor of 10(5) when exposed to a saline solution equivalent to the body fluid in 37 degreesC for 2 years. Preliminary animal tests indicate benign biological response. (C) 2001 Elsevier Science B.V. All rights reserved.