Estimation of bone microarchitecture pattern from AP spine DXA scans using the trabecular bone score (TBS): an added value in clinical routine for the patient: a short review

Intrinsically it is accepted that defining osteoporosis on the sole basis of bone mineral density (BMD) reached its limit. Indeed, the multifactorial aspect of this disease encourages the current definition of osteoporosis to evolve towards a complex risk model based on Clinical Risk Factor (CRF) and BMD. Considering these CRFs along with BMD in the assessment of fracture risk, increases the sen­ sitivity of screening without sacrificing specificity. Whereas part of the limit of the current use of DXA is currently being addressed by the concomitant use of CRFs it only partially takes into account the information of bone micro-architecture. Therefore, any additio­ nal information about micro-architecture would help to reduce the overlap between fracture and non-fracture subjects. The trabecular bone score (TBS) is a novel grey-level texture measurement that is based on the use of experimental variograms of 2D projection images, and is able to differentiate between two 3-dimentional (3D) micro-architectures that exhibit the same bone density, but different trabecular characteristics. TBS measures the mean rate of local variation of grey levels in 2D projection images. The TBS is obtained after re-analysis of a DXA exam, and can be compared with BMD, since both evaluate the same region of bone. An ele­ vated TBS reflects strong, fracture-resistant microarchitecture; a low TBS reflects weak, fracture-prone microarchitecture. The added value of the TBS in bone mineral densitometry for fracture risk assessment has been documented in cross-sectional, pro­ spective and longitudinal studies. Indeed, TBS has been found: 1) to be lower in post-menopausal women with a past osteoporotic frac­ ture compared with age- and BMD-matched women without fracture; 2) to give an incremental increase in the odds ratio for spine frac­ ture when combined with spine BMD; 3) to be lower in women with (versus without) fractures, irrespective of whether their BMD met the criteria for osteoporosis or osteopenia; 4) to prospectively predict facture as well as spine BMD; 5) recapture around 1/3 of the missclassified ne therapy. The aim of this short review is to repo in the light of its current validation.