Moving Beyond BMD

Osteoporosis and Fragile Bone Strength. According to the Bone Health & Osteoporosis Foundation and the International Society for Clinical Densitometry, BMD testing for osteoporosis is recommended for all women over age 65, all men over age 70, younger patients if there are relevant risk factors, and to monitor treatments. However, it is now recognized that osteoporosis is substantially underdiagnosed by current BMD testing. Too few people are tested and the clinical-standard DXA test fails to identify most who eventually fracture.

VirtuOst BCT — Biomechanical Computed Tomography analysis — now offers a comprehensive alternative by providing CT-based measurements of both BMD and bone strength. The BMD measurements at the hip provide DXA-equivalent T-scores that can be used following traditional guidelines; the BMD measurements at the spine are equivalent to those from quantitative CT for vertebral trabecular bone, which are unaffected by typical degenerative changes at the spine. In addition, reflecting state-of-the-art bone strength assessment of the hip and spine in clinical research, VirtuOst uses the engineering-based finite element analysis technique to provide a virtual stress test of a patient's bone to measure its breaking strength. This measurement accounts for such important strength characteristics as: 1) the size and three-dimensional shape of the patient's bone; 2) the internal spatial distribution of bone mass including the relative amount of cortical and trabecular bone; 3) the biomechanical properties of bone tissue; and 4) the external loading conditions associated with fracture. Indeed, fracture-outcome studies have consistently demonstrated that older people with very low levels of either BMD or bone strength are at high risk of a future fracture. Importantly, many high-risk patients with such fragile bone strength do not have BMD-defined osteoporosis.

For spine CT scans, VirtuOst VFA — Vertebral Fracture Assessment — identifies any existing vertebral fractures, which can be used to identify patients at high risk of a future fracture regardless of the BCT measurements. Patients who test positive for both BCT and VFA are considered to have severe osteoporosis.