Biomechanical Epidemiology — Biomechanics of Vertebral Fractures

 Fractures occur when the load applied to a bone exceeds its ability to resist that load. This ratio of skeletal loading to bone strength is referred to as the factor-of-risk, and our group has shown previously that factor of risk explains much of the age- and sex-specific patterns of wrist and hip fractures. We are now working to apply the factor-of-risk concept to understand the unique pathophysiology of vertebral fractures. This project brings together expertise in epidemiology, biostatistics, biomechanics and 3D-imaging, as well as a diverse set of collaborators, including the Institute for Aging Research at Hebrew Senior Life and the Framingham Heart Study.

More specifically, we are using 3D quantitative computed tomography scans from the population-based Framingham Heart Study to determine the effects of age, sex, and spinal location on vertebral body strength and its determinates, as well as on trunk muscle morphology in the lumbar and thoracic spine. We are also using the high-resolution imaging data to build subject-specific biomechanical models of the spine and estimate vertebral loading during various activities of daily life. The model currently incorporates subject-specific muscle morphology, and we are working to incorporate subject-specific spinal curvatures as well as subject-specific muscle quality parameters. We are also assessing muscle quality by measuring CT attenuation of trunk muscles, and plan to incorporate this information into our models. Our generic male thoracolumbar spine model is pubically available through the OpenSim community.

The findings from this project will provide a better understanding of the interaction between spinal loading and the determinants of vertebral strength. This may improve diagnostic sensitivity and specificity, and lead to therapeutic interventions for prevention and treatment of vertebral fractures that are targeted to specific biomechanical deficiencies. Ultimately such an approach will contribute to cost effective use of therapy. Altogether, the findings will have important implications for clinical management of individual patients at risk for osteoporosis and for public health policy.

This work is funded by NIH R01AR053986, R01AR/AG041398, R44AR052234, T32 AG023480, and the National Heart, Lung, and Blood Institute (NHLBI) Framingham Heart Study (NIH/NHLBI Contract N01-HC-25195).

Recent Publications:

Bruno AG, Bouxsein ML, Anderson DE. Development and validation of a musculoskeletal model of the fully articulated thoracolumbar spine and rib cage. J Biomech Eng 2015; 137(8). PDF

Kim YM, Demissie S, Eisenberg R, Samelson EJ, Kiel DP, Bouxsein ML. Intra-and inter-reader reliability of semi-automated quantitative morphometry measurements and vertebral fracture assessment using lateral scout views from computed tomography. Osteoporos Int. 2011. PDF (in press, Jan 27, 2011)

Samelson EJ, Christiansen BA, Demissie S, Broe KE, Zhou Y, Meng CA, Yu W, Cheng X, O’Donnell CJ, Hoffmann U, Genant HK, Kiel DP, Bouxsein ML. Reliability of vertebral fracture assessment using multidetector CT lateral scout views: the Framingham Osteoporosis Study. Osteoporos Int. 2011; 22(4):1123-31. PDF

Iyer S, Christiansen BA, Roberts BJ, Valentine MJ, Manoharan RK, Bouxsein ML. A biomechanical model for estimating loads on thoracic and lumbar vertebrae. Clin Biomech (Bristol, Avon). 2010; 25(9):853-8. PDF

Christiansen BA, Kopperdahl D, Kiel DP, Keaveny TM, Bouxsein ML. Contributions of cortical and trabecular bone to age-related declines in vertebral strength are not the same for men and women. J Bone Miner Res. 2011; 26(5):974-83. PDF

Christiansen BA and Bouxsein ML Biomechanics of vertebral fractures and the vertebral fracture cascade. Curr Osteoporos Rep 2010; 8(4):198-204. PDF