Biomaterial calcification: Mechanisms and prevention

Pathologic calcification of implants is a detrimental condition that can severely impact device performance and ultimately lead to implant failure. Although calcification affects a wide variety of medical implants, both synthetic and biologically derived, the pathogenesis of the disease is not well understood. In biologically derived implants, such as bioprosthetic heart valves, the major mechanisms of and factors contributing to calcification are chemical crosslinking, cellular damage, extracellular matrix composition, patient factors, and mechanical stress on the device. However, in synthetic-material implants, for example, intraocular lenses, pacemakers, and vascular replacements, calcification is largely due to surface conditions, such as material porosity, surface defects, and protein adsorption. This chapter investigates the mechanisms of implant calcification and discusses anti-calcification strategies, using specific medical devices as examples.