By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated
The following animation contains sequences that are intended to help support expert witness testimony regarding one of the causes of failure of certain types of knee prostheses (such as the Zimmer NexGen knee prosthetic).
The animation focuses on the cementless cobalt-chromium-molybdenum (CoCrMo) alloy prosthesis. It compares how new bone normally fuses with a prosthesis versus how ions emitted from the CoCrMo alloy inhibit osteoblasts (cells that are responsible for bone formation) from forming new bone. Fibroblasts (cells responsible for fibrous tissue formation, such as collagen) are less inhibited by the CoCrMo ions; therefore, the fibroblasts form fibrous tissue between the bone and prosthesis. This weak and inadequate fusion allows movement and loosening between the femur and prosthesis resulting in prosthesis failure.