Finite element analysis could aid patients with fragility fractures

Applying finite element analysis to high-spatial resolution 3-T MR images of proximal femur microarchitecture can enable detection of lower elastic modulus in subjects with fragility fractures, according to a study published online April 2 by Radiology.

The advent of in vivo three-dimensional bone microarchitecture imaging methods has been crucial for clinical assessment of osteoporosis. Bone biomechanics have additionally improved, as fine element analysis (FEA) can determine the geometry, shape, and microarchitecture of bone. The mechanical engineering method also offers output metrics of bone mechanical competence or strength.

Lead author Gregory Chang, MD, of the University of Pennsylvania School of Medicine in Philadelphia, and colleagues sought to determine the feasibility of applying FEA to in vivo high-spatial-resolution 3-T MR images of proximal femur trabecular microarchitecture for detection of lower elastic modulus in subjects with clinically defined osteoporosis compared with control subjects.

The researchers included 22 postmenopausal women with fragility fractures and 22 without in their study. All subjects were matched for both age and body mass index. They underwent standard dual-energy x-ray absorbitometry and images of proximal femur microarchitecture were gathered with a high-spatial-resolution three-dimensional fast low-angle shot sequence at 3-T.

Once FEA was applied to the images in order to calculate strength in the femoral head and neck, Ward triangle, greater trochanter, and intertrochanteric region, findings indicated that the patients with fractures exhibited lower elastic modulus than the control subjects in all proximal femur regions.

Those with fractures had elastic moduli of 8.51 to 8.73 GPa in the femoral head versus a range of 9.32 to 9.67 GPa in the control group. For the Ward triangle, the patients with fractures had a range of 1.85 to 2.21 GPa versus 3.98 to 4.13 GPa. In the intertrochanteric region the patients with fractures demonstrated 1.63 to 2.18 GPa versus 3.86 to 4.47 GPa in the control group. Lastly, the greater trochanter presented findings of 0.65 to 1.21 GPa in the group with fractures in comparison to scores between 1.96 to 2.62 in the control group.

No differences were observed in bone mineral density T scores. Additionally, there were weak relationships between elastic moduli and bone mineral density T scores in patients with fractures but not in the control subjects.

“Because osteoporosis is a disease of compromised bone strength, the ability of FEA to noninvasively provide an additional, quantitative marker of bone strength in vivo without the use of ionizing radiation in a critically important osteoporotic fracture location such as the hip could have important future implications for both osteoporosis research and clinical care,” wrote Chang and colleagues. “In addition to its use as a tool to study the effects of microachitectural adaptations on proximal femur strength (in patients with disease or after intervention), this method also could be adapted as an additional clinical care tool to assess patients’ risk of fracture and to determine whether therapy should be initiated.”