The process of senescence in the human vertebra uncomplicated by pathological endocrine disturbances is characterized by three histological reactions. Only one of these is directly physiological; the other two are the products of extraneous influence.

The fundamental characteristic is loss of trabecular substance clue to the failure of formation of collagen while its normal, or possibly accelerated, absorption continues.

A second manifestation, which may start many years earlier and is often but not necessarily present, is that of osteophytosis about the periphery of the cephalic and caudal margins of the vertebral body. This is particularly prominent along the line of the anterior longitudinal ligament. It is a prolifeiative reaction of suhchondral bone to the wear and tear of the articulating cartilaginous surfaces.

The third histological characteristic is to some extent always apparent. One or more small areas of localized avascular necrosis oi infarct spread through the spongiosa. These may be quite numerous in aged specimens, but have not been seen to coalesce and therefore do not apparently become large enough to cause gross collapse of the vertebrae.