Reaching a given BMD level is considered a treatment target. Bone quality is the other key component of bone strength. In patients on long-term oral bisphosphonates (LTB) we explore if bone quality, measured by microindentation, is associated with absence of fracture while on treatment (FWOT) and can be a treatment target. Cross-sectional study of osteoporosis patients on active LTB (>4 years) with good adherence and healthy volunteers. Other bone drugs or secondary osteoporosis cases were excluded. Local ERB approved the study. Microindentation with an Osteoprobe® (Active Life Scientific, Santa Barbara, CA) was performed in the anterior midtibia after local anaesthesia, measuring Bone Material Strength index (BMSi) as previously described (Bridges 2012). Multivariate logistic regression was used to study the association between BMSi and FWOT amongst long-term OBP users. Area under ROC curve (AUCROC) was used to study discriminatory ability of BMSi and BMD for FWOT identification. Seventy-four subjects were included: 40 LTB (4 to 14 years exposure) users (18 no fracture WOT, 22 FWOT), and 34 controls. In univariate analysis, controls showed (mean, 95%CI) significantly higher BMSi (87.6 (85.1, 90.2)) than LTB without FWOT (81.6 (78.5, 84.8)), with fracture cases having significantly lowest BMSi (72.2 (67.8, 76.5)). Similar trend (but no significant differences) were observed for spine and hip BMD. In multivariate models including only OBP users, higher BMSi was associated with reduced risk of FWOT, even after adjustment by age, years on BP, BMI and total hip BMD (adjusted OR 0.78/unit [0.640.94]; p=0.011). Conversely, BMD was not significantly associated with FWOT. BMSi had an AUCROC of 82.3%, compared with BMD (69.9% to 63.9% at different sites). In conclusion, better bone quality as measured by BMSi is inversely associated with FWOT amongst LTB users. Bone tissue quality levels, measurable by microindentation may be a treatment target although prospective validation studies are required.
Disclosure: ADP speaker or advisor for Lilly, Amgen, Pfizer, Active Life Scientific. Supported in part bt Instituto Carlos III (RETICEF) Spanish Ministry of Economy and Competitivity.