Radiographic and histopathologic changes in the spinal column of the aging beagle dog

A subgroup of 14 dogs has been radiographed since birth in an effort to more fully document the pattern of radiographic changes of aging within the spine. Tissue from dogs after death was examined with high-detail radiographic and histologic methods. A developing pattern of change involving the disk space and surrounding vertebrae was detected. The pathogenesis of change was one of anular degeneration with fibrillation and splitting of the fibers. Shifting of nuclear material occurred with preservation of the outer anular fibers. Vertebral osteophytosis, end-plate sclerosis or destruction, and disk space collapse followed. Invasion by granulation tissue into the herniated disk material was followed by endochondral ossification. Thus two separate patterns of response to degenerating disk occurred: one that stimulated new bone formation in the form of vertebral osteophytes ventrally and laterally and a second pattern located on the floor of the spinal canal characterized by haphazard endochondral bone formation. 5 tables