During middle and older age, there is an overall decrease in bone density and strength, particularly centrally within the vertebral body. Consequently, the articular surfaces gradually bow inward so that both the superior and inferior surfaces of the vertebrae become increasingly concave (Fig. B4.9A), and the IV discs become increasingly convex. The bone loss and consequent change in shape of the vertebral bodies may account in part for the slight loss in height that occurs with aging. The development of these concavities may cause an apparent narrowing of the intervertebral “space” on radiographs based on the distance between the margins of the vertebral bodies; however, this should not be interpreted as a loss of IV disc thickness.
Aging of the IV discs combined with the changing shape of the vertebrae results in an increase in compressive forces at the periphery of the vertebral bodies, where the discs attach. In response, osteophytes (bony spurs) commonly develop around the margins of the vertebral body (along the attach