Articular and internal remodeling in the human otic capsule.

Abstract

AbstractA comprehensive histologic study of the human otic capsule is presented demonstrating the interrelations between cartilage, bone, blood vessels and soft tissue throughout life. Remodeling occurs through continual degeneration of chondrocytes within the uncalcified articular surfaces of the stapediovestibular joint and through continual degeneration of cartilage about the cochlea and semicircular canals. Degenerated chondrocytes are removed by macrophages and new endochondral bone forms from adjacent osteogenically active blood vessels. The cartilage surfaces of the footplate and oval window are constantly replenished by new cartilage formed by mesenchymal cells of the annular ligament. Within the otic capsule, new cartilage forms from mesenchymal cells lining the labyrinth. Cartilage foci continually undergo partial replacement by endochondral bone with remnants of uncalcified cartilage matrix remaining, forming globuli ossei and interglobular spaces. In addition to continual endochondral bone formation partially replacing the continually forming and degenerating cartilage, chondroid bone forms by direct transformation of some cartilage to bone. These chondroid bone areas are cellular in young age groups, but become pale and relatively acellular with age. These processes occur throughout life, regardless of age or sex.