The distribution of calcific deposits in intervertebral discs of the lumbosacral spine.

The incidence of intervertebral disc calcifications (IVDCs) was examined in 52 lumbosacral spines obtained sequentially at autopsy. The presence of calcific deposits was detected by fine-grain roentgenograms. The nature of these deposits was determined by wide-angle x-ray diffraction, and histologic observations were made. A high prevalence of IVDC, 18 spines of 52, some with multiple deposits, was noted. Calcium pyrophosphate dihydrate (CPPD) deposits were found in 3% of the spines and accounted for 29% of the 42 deposits analyzed. The CPPD deposits occurred at multiple disc levels (an average of four per spine), were diffuse, and involved a major portion of the disc (nucleus pulposus, annulus fibrosus, and endplate) but were not generally associated with histologic disc degeneration. Hydroxyapatite (HA) deposits occurred in 12% of the spines, most often in the nucleus pulposus and endplate. The HA deposits appeared as small punctate radiodensities. Roentgenographic evidence of degenerative changes, i.e., disc space narrowing, endplate disruption, desiccation, and osteophyte formation, were present in all but one of the spines containing HA deposits. An additional 19% of the spines had deposits that could not be characterized by x-ray diffraction but were very similar in roentgenographic appearance to HA deposits. No conclusions could be drawn on the relationship between the presence of HA or CPPD and collagen or hexosamine content.