Correlation between bone mineral density and intervertebral disc degeneration.

STUDY
DESIGN: Intervertebral disc area, disc bulge ratio, and bone mineral density were measured in 86 postmenopausal women and the data analyzed.
OBJECTIVE: To examine quantitatively the correlation between intervertebral disc degeneration and bone mass. SUMMARY OF BACKGROUND DATA: In results of previous studies, an inverse correlation between osteoporosis and spondylosis has been reported. In these studies, only radiographic findings were used to evaluate spondylosis; changes in the intervertebral disc itself were not investigated.
METHODS: To determine bone mass, total-body bone mineral density, lumbar bone mineral density, and age-matched control values of bone mineral density were measured by dual-energy X-ray absorptiometry in all cases. To evaluate intervertebral disc degeneration, disc area and disc bulge ratio (calculated by measuring the areas protruding from lines connecting the middle points of the anterior and posterior borders of the vertebral bodies) were obtained from four discs, using magnetic resonance images of the lumbar spine. The correlation between bone mass data and disc area data was analyzed.
RESULTS: Bone mineral density showed a significant decrease with increasing age. Disc area and disc bulge ratio had no relation to age. There was a negative correlation between total-body bone mineral density, lumbar bone mineral density, and age-matched control values versus disc area, and a positive correlation between all bone mineral density data and the disc bulge ratio.
CONCLUSIONS: According to the results of the analysis by disc morphology and bone mass, especially total body bone mineral density, bone mass has an inverse correlation to intervertebral disc degeneration--i.e., reduction and disc bulge--which is important when considering degenerative spinal diseases and osteoporosis.