Mineralization of connective tissue surrounding implanted devices.

Calcification and ossification of soft tissues occurs as a response to a variety of injuries such as atherosclerosis, myositis ossificans, and caseous necrosis. These injuries and others have as a unifying characteristic persistent necrotic tissue elements. Normal tissues may calcify under conditions of hypercalcemia or hyperphosphatemia. The initial mobilization of Ca and P following injury is rapid, as observed in calcergy. The mitochondria of cells, normally a storehouse of Ca, become preferential sites of precipitated Ca when cells are irreversibly injured, and act as foci of progressive calcification. Collagen fibers undergo calcification directly, principally when they are located within devitalized sites such as prosthetic heart valves, and direct calcification of collagen may predominate generally in dystrophic calcification. VArious porous sponges act as foci for calcification and ossification, and the utilization of porous implants may provide for the development of therapeutically useful calcifying and ossifying biomaterials.