A Mechanical Approach in Approximating the In Vivo Conditions of the Human Spine

Chronic low back pain (CLBP) is one of the most common health problems in humans. To better understand the mechanics and dynamics of the spine, six thoracolumbar spines (T12 - Pelvis) were mounted into a custom mechanical testing apparatus, which closely approximated in vivo conditions.  This testing apparatus was mainly composed of three components: a torso plate (where dead weights are added to simulate the upper torso weight); a hip simulator (where the pelvis is attached to create a fixed posture); and four torque motors that simulated and digitally controlled three major muscle groups which are the, erector spinae, rectus abdominus, and finally, right and left deep lumbar multifidus.  This testing apparatus allowed the thoracolumbar spines to undergo a wide range of postures, such as, neutral (standing-sitting), flexion-extension (stability pertubations), and axial rotation.  Data was collected using infrared markers inserted into the spine’s vertebral bodies to measure the relative motion in response to a physiologic boundary condition.  Currently, the testing apparatus is being used to quantify the contribution of the active components (simulated muscles and tendons) versus the passive components (ligaments, discs, and vertebral bodies). Furthermore, this novel apparatus is investigating the impact of muscle atrophy on lumbar lordosis and spine stability in the presence of small perturbations. The goal of this research is to provide greater insight into the contribution of deep muscle groups have on the spine to better understand CLBP.