Measuring bone mineral density and predicting the biomechanical strength of a patient’s femur can help diagnose the risk for osteoporosis. By using a special algorithm with CT, researchers found that they can better calculate fracture risk.Dual-energy x-ray absorptiometry is the standard for predicting proximal femur fracture risk. However, the procedure cannot differentiate cortical bone from trabecular bone, which is known to be metabolically more active and therefore shows larger changes related to osteoporosis. Markus B. Huber from the University of California, San Francisco, and his colleagues decided to use CT’s ability to distinguish between the two types of bone to try and better quantify fracture risk. They created a special algorithm for CT that segments trabecular bone at the proximal femur and that determines the trabecular bone mineral density and bone mineral content in the head, neck and trochanter of the femur. As reported in the May issue of Radiology, the researchers tested 178 proximal femurs from human cadavers with both CT and dual-energy x-ray absorptiometry scans. Then they tested the amount of load the femur could handle and correlated these values with the bone mineral density findings.The investigators discovered that the CT density data correlated best with femur failure load in the head (r = 0.77) compared with the trochanter (r = 0.59) and the neck (r = 0.53). Similar correlations were found with bone mineral content. Values ranged between 0.77 and 0.80 for correlations between dual-energy x-ray absorptiometry bone mineral density and femur failure load, and between 0.73 and 0.82 for bone mineral content. However, they found that when they used a multiple regression model that combined both dual-energy x-ray absorptiometry and quantitative CT measurements, correlations with failure load increased to up to 0.88. They conclude that the best way to quantify fracture risk is to use a combination of both measuring techniques.