Discrete Geometric Based Stress Analysis of the Lumbar Soft Tissues From In Vivo Kinematics

Back pain in the region of the lumbar spine has become an increasingly significant problem among individuals in the United States and is a leading cause of disability and missed work days. At present, efforts focused on treating both the symptoms and causes of low back pain have proven to be difficult, and researchers and clinicians still do not fully understand the most effective means for treating the symptoms. Utilizing a biomechanics approach, it is assumed that lower back pain is, at least in part, associated with an increased localized stress.

Current models used to determine stresses are typically based from a spine simulator data where pre-prescribed motion or forces are used; however, this does not allow for patient specific motions. The muscles in the back responsible for the motion or force are either neglected due to imputed forces or optimized out with the input of motion. The objective of this study was to determine the stresses in the intervertebral discs using the 3D motion with computed tomography bone models. This allows for patient specific stress to be calculated using material properties of the disc and the motion of the disc space. Furthermore, motion of the vertebra during this in vivo motion will allow for stress calculations of the ligaments and muscles as well. The materials prescribed to the soft tissues will be a combination of existing techniques in order to represent the tissue as close to how it actually is. From these stress results, correlations can be made between the different groups collected: normal, low back pain, degenerative, and surgical patients. This will hopefully provide insight into why people have low back pain without sign of degeneration, how degenerative discs effect stress, and if stress are higher at the adjacent disc after surgery.