A new diagnostic score to detect osteoporosis in patients undergoing lumbar spine MRI

Signal intensity of lumbar-spine at magnetic resonance imaging (MRI) correlates to bone mineral density (BMD). Our aim was to define a quantitative MRI-based score to detect osteoporosis on lumbar-spine MRI. After Ethics Committee approval, we selected female patients who underwent both lumbar-spine MRI and dual-energy X-ray absorptiometry (DXA) and a reference group of 131 healthy females (20-29 years) who underwent lumbar-spine MRI. We measured the intra-vertebral signal-to-noise ratio in L1-L4. We introduced an MRI-based score (M-score), on the model of T-score. M-score diagnostic performance in diagnosing osteoporosis was estimated against DXA using receiver operator characteristic (ROC) analysis. We included 226 patients (median age 65 years), 70 (31 %) being osteoporotic at DXA. MRI signal-to-noise ratio correlated to BMD (r = -0.677, P < 0.001). M-score negatively correlated to T-score (r = -0.682, P < 0.001). Setting a 90 %-specificity, an M-score threshold of 5.5 was found, distinguishing osteoporosis from non-osteoporosis (sensitivity 54 %; ROC AUC 0.844). Thirty-one (14 %) patients had a fragility fracture, with osteoporosis detected in 15 (48 %) according to M-score and eight (26 %) according to T-score (P = 0.016). M-score obtained on lumbar spine MRI is a quantitative method correlating with osteoporosis. Its diagnostic value remains to be demonstrated on a large prospective cohort of patients. M-score is a quantitative score potentially screening osteoporosis on lumbar-spine MRI; This method showed good intra- and inter-reader reproducibility; M-score may be used for identifying patients who should undergo DXA.