Biomechanical considerations for dorsal-lumbar and lumbar sagittal spine disorders

Lower back pain is one of the most important socioeconomic diseases and one of the most important health care issues today. On an average, 50-90% of the adult population suffers from lower back pain and lifetime prevalence of lower back pain is 65-80%. The causes of lower back pain often remain unclear and may vary from patient to patient. It is estimated that 75% of such cases are associated with lumbar degenerative intervertebral disc disease. As dysmorphisms or sagittal disorders of rachis it is meant its back (kyphosis) or front (lordosis) phatological deviations, irreducible in various measure, resulting from structural disk-ligament and vertebral alterations of various etiology. Three numerical model of dorsal-lumbar spine, respectively a physiological one, a ipolordotic one and a kyphotic one, have been realized considering bone, disks and ligaments with their specific mechanical characteristics. For the load and boundary conditions chosen, joint facets and intervertebral disk stresses and disk bulge have been compared for the three spine situations. When it has been possible, obtained results has been validated with data available in literature regarding both experimental studies and computational ones. In conclusion it can be assumed that dorsal-lumbar and lumbar sagittal spine disorders can determine premature disks and joints alterations. In particular it seems that the dorsal-lumbar kyphosis, more than the lumbar ipolordosis, can expose joint facets and disks to non physiological loads. Also if it is acknowledged the genetic role of disk degeneration, it is probable that the correction, in precocious age, of sagittal spine imbalance, can prevent or slacken the disk-joint lumbar-sacral degenerative phenomena. The obtained results agree with the clinical experience