Postural Biomechanical Stability and Gross Muscular Architecture in the Spine

Abstract

Consider a ligamentous thoracolumbar spine specimen, sacrum-T1, fixed at the sacrum and carrying a load at T1. It has been determined experimentally that such a spine buckles when the load reaches a critical value of about 20N. Or consider a lumbar spine specimen, sacrum-T1, its critical load is less than 90N. On the other hand, we have a world class weight lifter who can carry more than 3000N without damaging the spine. Simply stated, the difference between the two behaviors is the spinal muscles. The same is true in another example. Compare a healthy normal person and polio patient. The latter, with the back muscles paralyzed, cannot even hold his/her own trunk in the upright position. The important role of the muscles as the stabilizers of the spine is unquestioned and essential for its function. A deficiency in either muscle function or bony ligamentous function eventually lead to disabling clinical problems