Degenerative lumbar spondylolisthesis: Anatomy, biomechanics and risk factors

Degenerative spondylolisthesis (DS) is a major cause of spinal stenosis and is often related to low back and leg pain. We reviewed the anatomical and biomechanical predisposition of lumbar DS and discuss possible predictors and risk factors for this condition. Spinal segment L4-L5 is most vulnerable because of the great forces in this region and the increased mobility of this segment due to the specific anatomy of quadratus lumborum muscle and iliolumbar ligament. A high pelvic incidence and lumbar lordosis increase the forces on the low spinal segments and probably raise the risk for DS. Individuals with relatively more sagittal orientation of the lumbar facets have a higher probability of developing DS because such joints have less ability to resist the shearing forces. Disc degeneration is not an important predisposing factor for DS. Reduced disc space caused by disc degeneration increases the facet joint articulation overlap and together with osteophyte formation and ossification of spinal ligaments, can be seen as a part of the restabilization process. Deep abdominal and paraspinal muscles, most likely, play an important role in dynamic lumbar stability. Factors found to be associated with lumbar DS include age > 50, female gender, pregnancy, African American race, and generalized joint laxity.