Biomechanical comparison of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion performed at 1 and 2 levels

Study Design. Biomechanical laboratory study of human cadaveric spines. Objective. To determine the difference in acute stability between posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) performed at 1 and 2 levels with and without posterior fixation. Summary of Background Data. Circumferential spinal fusion with both an interbody graft and posterior pedicle screw-rod construct has been advocated to decrease pseudarthrosis rates. Both PLIF and TLIF theoretically allow for 3-column fixation and fusion. Methods. Specimens underwent either PLIF or TLIF at L2-L3 (single-level) and L3-L4 (2-level), both with and without pedicle screw instrumentation. During TLIF, an interbody allograft was placed in the anterior or middle column. Nondestructive, nonconstraining pure moment loading was applied to each specimen. Results. There were no significant differences in the range of motion after either PLIF or TLIF at 1 level. The addition of pedicle screws tended more strongly to increase rigidity after 1-level PLIF compared to TLIF. Position of the TLIF graft did not affect stability. The addition of pedicle screws to a 2-level construct significantly reduced all motions tested. Conclusions. Based on our findings, posterior fixation with a pedicle screw-rod construct is suggested for 1-level PLIF and TLIF, and is necessary to achieve stability after interbody fusion across 2 levels using either technique.