The effect of postural changes on the inferred pressures within the nucleus pulposus during lumbar discography.

By observing the variation of intradiscal pressure occurring at different body postures, it is possible to infer a functional hydrostatic behavior of a lumbar disc. Results from such observations on normal discs are already available. However, observations on degenerate discs are largely restricted to in vitro studies. The authors are now able to report a series of recordings taken from discographically degenerate lumbar discs in patients presenting with low-back pain. In this study of twenty patients, pressure observations were made on 21 normal and 19 abnormal discs. From the results that the authors have obtained, they can reaffirm that normal discs behave predictably and as previously described. The abnormal discs, however, did not behave as a single group. They showed patterns of pressure changes in different postures often dissimilar from that shown by the normal discs both in the absolute values recorded and the sequential changes that occur during the postural change. Unfortunately, the authors were unable to correlate either the extent or character of disc degeneration with the observed variation in pressure changes.