TBS in early postmenopausal women with severe vertebral osteoporosis

Severe vertebral osteoporosis is a rare condition in early postmenopausal women. We seek to determine whether Trabecular Bone Score (TBS), which is a new bone texture measurement, could be of additional value in evaluating trabecular bone properties in this population.

Lumbar spine (LS) and femoral neck (FN) bone mineral densities (BMDs) and TBS were measured in 105 early postmenopausal women (group 1: "cases", mean age: 53.1 ± 2.6 yrs.) with severe vertebral osteoporosis defined as a vertebral BMD T-score ≤ 3, as well as in 105 healthy postmenopausal women matched for age (group 2) and 105 older osteoporotic women matched for vertebral BMD (group 3, mean age: 63.9 ± 4 yrs.). None of the women had a secondary cause for osteoporosis. Correlations between TBS values and BMD were calculated after controlling for clinical characteristics.

The women in group 1 (cases) were significantly smaller and thinner and had a history of more fractures than the age-matched controls (p < 0.05). Mean LS and FN BMD values were significantly lower in the cases than in the age-matched controls (0.770 ± 0.05 vs 1.106 ± 0.11 g/cm² and 0.700 ± 0.07 vs 0.872 ± 0.12 g/cm², for LS and FN, respectively; p < 0.001). The mean TBS value was also significantly lower in the cases than in the age-matched controls (1.24 ± 0.08 vs 1.37 ± 0.07, p < 0.001) but significantly higher than in the older osteoporotic controls (1.20 ± 0.07, p < 0.05). After adjustment for vertebral BMD, the difference in TBS values between the cases and the age-matched controls was no longer significant although it remained significantly higher than in the older osteoporotic controls. This would suggest that in group 1, osteoporosis is rather the consequence of a low peak bone mass than of further bone degradation while the greater decrease in TBS value in elderly osteoporotic controls is more likely to reflect additional damage in bone microarchitecture associated with aging. In a multivariate analysis including age, vertebral and femoral neck BMD, height and weight (R² = 0.60, p < 0.0001), TBS was found to be negatively and independently associated with age (r = -0.31 p < 0.0001) and height (r = -0.20 p < 0.001). The FRAX score was significantly higher in group 1 and group 3 women than in the healthy control women (group 2). There were no changes in the results after adjustment for TBS.

Women presenting with severe vertebral osteoporosis at the beginning of menopause have TBS values that are, first and foremost, proportional to their BMD. Whether this indicates that osteoporosis in this population is the consequence of a low peak bone mass remains to be determined and further studies are required. Nevertheless, the value of measuring TBS in addition to BMD appears to be relatively negligible in early postmenopausal women with severe vertebral osteoporosis.