Relationship between low back pain in post-menopausal women and mineral content of lumbar vertebrae

Until recently, chronic low back pain in post-menopausal women was commonly attributed to osteoporosis. This opinion has since been challenged on many counts, but controversy persists. The objective of this study was to examine this relationship. In 67 post-menopausal women, the mineral content of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry and the age-normalized bone mineral index (ANBMI), the Z-score, was determined. Mean ANBMI in 40 subjects who complained of chronic low back pain (Group 1) was compared with mean ANBMI in the 27 who did not (Group 2). Pain intensity and related disability were quantified using standard questionnaires. Their respective correlations with ANBMI index and age at onset of menopause were examined. Correlation coefficients and significance of group differences were examined by appropriate statistical methods. The results showed that the mean ANBMI in Group 1 subjects was 96.5 +/- 16.9%, in Group 2 subjects it was 88.6 +/- 10.0%. Neither pain intensity nor disability was correlated with ANBMI. A weak but significant positive correlation was noted between body mass index and intensity of low back pain (r=0.37; P<0.05). The occurrence and severity of chronic low back pain in post-menopausal women, and the disability thereof, appear to be unrelated to the mineral content of lumbar vertebrae.