Assessment of trabecular bone score (TBS) in the prediction of vertebral fracture in postmenopausal osteoporosis

The study aimed to evaluate the role of trabecular bone score (TBS) as determinant in the risk for vertebral fracture (VF) and define specific TBS threshold/s in women with postmenopausal osteoporosis.

We studied 107 women with postmenopausal osteoporosis characterized by L1-L4 T-score ≤ −3.0 with (group 1) and without (group 2) VF, or L1-L4 T-score ≤ −1.0 and ≥ −2.4 and multiple vertebral fractures (VF) (group 3). We assessed 30 postmenopausal women with L1-L4 T-score ≤ −1.0 and ≥ −2.4 and no VF as controls (group 4). We measured L1-L4, femoral neck and total hip areal bone mineral density (aBMD) by dual X-ray absorptiometry (DXA) (QDR 4500; Hologic, Waltham, MA) and calculated TBS from de-identified DXA L1-L4 scans by the TBS iNsight software (Medimaps, Geneva, Switzerland). The assessment of VF was performed by means of anteroposterior and left lateral standardized radiographs of the thoracic and lumbar spine. We calculated the FRAX® value in all subjects for the assessment of 10-year fracture risk for major and hip fractures.

Forty-two subjects with L1-L4 T-score ≤ −3.0 had at least one VF (group 1), while 41 have no VF (group 2). Twenty-four subjects had L1-L4 T-score ≤ −1.0 and ≥ −2.4 and at least 3 VF (group 3). We observed significantly lower TBS values in group 1 and group 3 compared to group 2 (p < 0.001) and group 4 (p < 0.05). L1-L4 aBMD and TBS values were not significantly associated in all groups. Interestingly, TBS values were independently associated with the presence of VF (log odds ratio − 8, p < 0.001) but not with the number of VF by the stepwise regression analysis. Furthermore, when we applied the cut-off value of TBS associated with degraded microarchitecture and elevated fracture risk (< 1.23), only 52 % of the subjects had VF. The cut-off value of TBS below which VF could be predicted was calculated by the receiver operating characteristic curve analysis and was 1.13.

Our study demonstrates an independent association between altered trabecular microarchitecture, assessed by TBS, and the occurrence of VF in postmenopausal women with osteoporosis. This association is significant for values of TBS lower than those reported by population-based studies. Cut-off values of TBS need further evaluation by specifically designed studies assessing disease- specific thresholds for fracture risk.