IMPROVED ASSESSMENT OF LUMBAR VERTEBRAL BODY STRENGTH USING SUPINE LATERAL DUAL-ENERGY X-RAY ABSORPTIOMETRY

Clinical and biomechanical investigations indicate that assessment of vertebral body bone mineral density (BMD) by anteroposterior dual-ener gy x-ray absorptiometry (DXA) is a useful index of vertebral body stre ngth and fracture risk in osteoporosis. However, inclusion of non-forc e-bearing and small-force-bearing mineralized structures, such as the posterior elements and aortic calcifications, in the measurement of an terior BMD obscures the assessment of vertebral body mass by this tech nique, Indeed, such interference is particularly severe in the presenc e of posterior element degeneration or previous spinal surgery. Recent anatomic studies illustrate that the lateral view provides unobstruct ed visualization of the L3, L4, and possibly L2 vertebral bodies, sugg esting that supine lateral BMD may more accurately assess vertebral bo dy fracture risk, We evaluated this hypothesis in a blinded study usin g human cadaver spines to compare the value of supine lateral and ante roposterior BMD in assessing vertebral body fracture force, average co mpressive stress, maximum stored strain energy, and strain at failure. Both measures of BMD significantly correlate with these biomechanical measures. However, statistical comparison of the methods using multip le and stepwise regression reveals that supine lateral BMD provides a better assessment of the vertebral body fracture properties than anter oposterior BMD. The enhanced predictive value of supine lateral BMD oc curs because of the variable contribution of posterior element mineral to the anteroposterior BMD measurement. Evaluation to test the utilit y of supine lateral BMD for the assessment of fracture risk and a frac ture threshold in patients with osteoporosis is therefore recommended.