Surface Hardening of Orthopedic Implants

Abstract

Implanted biomedical prosthetic devices are intended to perform safely, reliably, and effectively in the human body for prolonged periods of time. Stability under the imposition of repetitive loading in a hostile environment places unique demands on the materials, designs, and manufacturing methods used to create the implant. Materials used for orthopedic devices should possess good biocompatibility, adequate mechanical properties, and sufficient wear and corrosion resistance, and they should be manufacturable at a reasonable cost. Titanium-aluminum-vanadium (Ti-A1-V) and cobalt-chromium-molybdenum (Co-Cr-Mo) alloys possess these unique requirements, and have found successful applications in the field of orthopedics as prosthetic and fracture fixation devices. These alloys are used extensively in hip and knee implants as an articular surface sliding against ultra-high molecular-weight polyethylene (UHMWPE). The presence of abrasive particles, such as bone, bone cement, or other foreign materials, can substantially increase wear and debris generation rates of the articulating surfaces (1). By increasing the alloy’s resistance to scratching, surface-hardened alloys can assist in reducing polymer wear.