Foraminal encroachment syndrome in true lumbosacral spondylolisthesis: a preliminary report.

The source of pain in isthmic spondylolisthesis is uncertain. Some authors believe that spondylolysis and/or spondylolisthesis is not a predisposing factor to low back pain and that the mere presence of isthmic spondylolisthesis may, indeed, not be the cause of low back pain in the patient. This study explores a possible source of biomechanical dysfunction as an origin of pain in isthmic spondylolisthesis. One hundred and twenty lumbar intervertebral disc angles were measured, 60 of which had spondylolisthesis and the remaining 60 without spondylolisthesis for comparison of the effect that spondylolisthesis has on intervertebral disc angulation of the lumbar spine. The results reveal that the L4-L5 joint has the greatest biomechanical stress placed upon it by virtue that it had the highest intervertebral disc angulation when the component of spondylolisthesis was a factor at L5-S1. Therefore, due to increased intervertebral disc angles at L4-L5, a biomechanical stressing and resulting hyperextension of the facet articulation at L4-L5 may represent a source of symptomatology in isthmic spondylolisthesis of L5-S1.