Effects of slip severity and loading directions on the stability of isthmic spondylolisthesis: a finite element model study.

Study Design: Using a validated finite element model, the biomechanical effects of pars defect in a lumbar segment with and without different degrees of slip (up to 50% slip) were studied.

Objectives: To study the effects of slip severity and loading parameters on the stability of the lytic and adjacent motion segments. Better knowledge of the biomechanics of spondylolisthesis may help formulate treatment strategies such as bracing or spinal implants.