Investigation of Reaction Forces in the Thoracolumbar Fascia during Different Activities: A Mechanistic Numerical Study.

Spinal instability remains a complex phenomenon to study while the cause of low back pain continues to challenge researchers. The role of fascia in biomechanics adds to the complexity of spine biomechanics but offers a new window from which to investigate our spines. Specifically, the thoracolumbar fascia may have an important role in spine biomechanics, and thus the purpose of this study was to access the mechanical influence of the thoracolumbar fascia on spine biomechanics during different simulated activities. A numerical finite element model of the lumbar spine inclusive of the intra-abdominal and intra-muscular regions as well as the thoracolumbar fascia was constructed and validated. Four different loading scenarios were simulated while deformation, stress, pressure, and reaction forces between the thoracolumbar fascia and spine were measured. Model validation was accomplished through comparison to in vivo and ex vivo published studies. Force transmission between the thoracolumbar fascia and the spine increased 40% comparing kyphotic and squatting lifting patterns. Further, the importance of reciprocating paraspinal and intra-abdominal pressures was demonstrated. It was also found that tension in the thoracolumbar fascia remains even in a simulated prone position. This numerical analysis allowed for an objective interpretation of the loads conveyed through the thoracolumbar fascia in different positional or lifting scenarios. Based on validation studies, it would appear to be a viable experimental platform from which insight can be derived. The loads in the thoracolumbar fascia vary considerably based on simulated tasks and are linked to the pressures in the paraspinal and intra-abdominal regions.