Bone Abstracts

Context: Previous impact microindentation studies have demonstrated that osteoporosis patients exhibit impaired bone material strength, which may contribute to skeletal fragility. Whether the impact differs between subtypes of fractures has, however, not been evaluated yet.

Objective: To test whether impaired bone material properties differ between different subtypes of osteoporotic fracture and assess how this property relates to fracture severity.

Methods: We measured bone material strength index (BMSi) by impact microindentation in 60 normal controls and 74 women with osteoporosis with or without fractures. Bone mineral density by DXA and markers of bone turnover were also assessed. Vertebral fracture severity was determined by semi-quantitative (Q3) grading of lateral X-rays of the spine from the DXA-scanner.

Results: BMSi was found to be significant lower in subjects with osteoporotic fractures than in controls (77±7.1 vs 71.2±6.5 P<0.001). Moreover, a significant negative correlation was observed for BMSi on fracture Q3 severity, which remained significant after adjusting for age and total hip BMD (r²=0.19, P=0.008). Each incremental decrease of one standard deviation in BMSi was associated with a 4.5-fold increased risk of fracture, after adjustment for age, weight and height (OR 4.45; 95% CI 1.07, 19.21 P=0.04). The receiver operator curve (ROC) area under the curve (AUC) for BMSi for patients with vertebral fracture, hip fracture and non-vertebral non-hip fracture were 0.758 (0.648–0.868); 0.712 (0.576–0.848) and 0.668 (0.527–0.809), respectively.

Conclusion: Impaired bone material properties constitute an independent risk factor for all important osteoporotic fractures (vertebrae, hip, non-vert-non-hip) and is also related to the severity of vertebral fractures.