Disc height and signal intensity of the nucleus pulposus on magnetic resonance imaging as indicators of lumbar disc degeneration

Study Design. A cross-sectional magnetic resonance imaging (MRI) study of d egeneration of the lumbar spine. Objectives. To compare the usefulness of disc height and that of T2-weighte d signal intensity as indicators of disc degeneration. Summary of Background Data. Disc height and signal intensity have been used as indicators for disc degeneration. Their relation to each other and to e arly degeneration has not been well documented. There is evidence that phys ical load can affect disc height. Methods. Forty-one machine operators, 41 construction carpenters, and 46 of fice workers, aged 40-45 years, and 22 students aged 18-20 years were exami ned with sagittal magnetic resonance imaging. All study participants were m en. The mean value of the anterior and posterior disc height and the relati ve T2-weighted signal intensity of the nucleus pulposus of discs L2-L3 to L 5-S1 were measured. Results. Young men showed the lowest disc height but the highest relative s ignal intensity. Disc height showed an increasing trend from the office wor kers (sedentary) to blue-collar workers (more physical work) at all disc le vels but L5-S1. Relative signal intensity showed a decreasing trend for the se same worker types at all levels. In generalized linear modeling, signal intensity and the occupations, in reference to the young students, showed a significant effect on disc height. Conclusions. Relative signal intensity was lower in the middle-aged men tha n in the young men, indicating agerelated disc degeneration. Despite the ge neral positive association between disc narrowing and decreased relative si gnal intensity, disc narrowing may behave unexpectedly in relation to signa l intensity and age. Signal intensity may be a more sensitive measure of di sc degeneration. The validity of disc height as an indicator of early degen eration seems questionable.