Biomechanical stability of lateral lumbar interbody fusion with minimally invasive posterior intrafacet fixation

Introduction: Lateral lumbar interbody fusion (LLIF) is increasingly employed to address spinal degeneration and deformity. While supplemental fixation with posterior pedicle screws and rods (PSR) enhances stability and reduces hardware failure, it also increases surgical time and invasiveness, stays. An alternative approach is intrafacet fixation using cages, which stabilize spinal facet joints with minimal disruption. Although initially designed for cervical use, preliminary evidence suggests efficacy in the lumbar region. This study proposes a biomechanical cadaveric model to investigate intrafacet fixation stability versus PSR in single-level LLIF.

Methods: Eight human cadaveric L1-Sacrum specimens were used in the study. Intact specimens were instrumented with bilateral pedicle screws at the L2-L5 vertebrae, followed by baseline testing to establish stability. LLIF procedures were then performed at the L2-3 and L4-5 disc levels. Stability was assessed under various conditions:

1. Standalone LLIF at the L2-3 and L4-5 levels.
2. LLIF with Posterior Spinal Rods fixing the L2-3 and L4-5 segments.
3. LLIF with Facet Cages inserted bilaterally at the same levels.
4. Combination of LLIF, facet cages, and posterior spinal rods.

Three-dimensional motion tracking were conducted using pure moment testing (7.5 Nm flexion-extension, left-right lateral bending, left-right axial rotation) across all conditions. Data were statistically analyzed (RM ANOVA, SNK post hoc, p< 0.05) to compare stability across the different configurations.

Results: LLIF with posterior facet cage fixation was found to have statistically similar biomechanical stability to LLIF with posterior pedicle screw and rod in all ranges of motion at both L2-3 and L4-5 (all p > 0.84). Both conditions were found to have superior biomechanical stability to standalone LLIF at L2-3 in the extension condition (facet cage; p = 0.0047, posterior spinal rod; p = 0.0084).

Conclusion : In this study, LLIF with posterior facet cage fixation exhibited biomechanical stability comparable to the traditional approach of LLIF with posterior pedicle screw and rod fixation. This suggests that posterior facet cage fixation offers surgeons a less invasive alternative for achieving supplemental posterior stabilization in LLIF constructs, compared to percutaneous pedicle screw fixation.