Biomechanical Evaluation of Novel L-Shaped Side-Locking Plate with OLIF Across Bone Densities

Overview

This finite element study demonstrates that the novel L-shaped side-locking plate (NLSLP) significantly enhances segmental stability in OLIF procedures, especially in sagittal plane motion, across normal, osteopenic, and osteoporotic bone conditions. The NLSLP reduces range of motion more effectively than traditional two-screw lateral plates and maintains biomechanical stability while minimizing endplate stress and risk of cage subsidence.

Background

Oblique lateral interbody fusion (OLIF) is a minimally invasive surgical technique for lumbar degenerative diseases that preserves posterior spinal structures and facilitates indirect decompression. However, cage subsidence remains a significant complication, particularly in osteoporotic patients, often necessitating supplemental fixation. Traditional bilateral pedicle screw fixation provides strong stability but compromises OLIF's minimally invasive advantages, while conventional lateral plates offer limited sagittal plane control. To address these limitations, a novel L-shaped side-locking plate (NLSLP) was developed to improve biomechanical stability without sacrificing the benefits of OLIF.

Data Highlights

Key Findings

• The NLSLP significantly reduces range of motion at the L4-L5 segment, with over 85% reduction in lateral bending and axial rotation.
• Compared to traditional two-screw lateral plates (LP-2), the NLSLP provides 17.85%–18.22% greater restriction in sagittal plane motion, enhancing flexion-extension stability.
• In osteoporotic bone models, the NLSLP maintains biomechanical stability with ROM reductions exceeding 65%, indicating suitability for compromised bone quality.
• The NLSLP reduces stress on the L5 superior endplate under all loading conditions compared to stand-alone OLIF, potentially lowering the risk of cage subsidence.
• Stress on internal fixation components in the NLSLP system remains well below material fatigue and yield thresholds, suggesting favorable durability and safety.
• All surgical models, including NLSLP, increase stress in adjacent intervertebral discs, with the NLSLP showing a 39.86%–45.12% increase in lateral bending stress.

Clinical Implications

The NLSLP offers a promising adjunct fixation method for OLIF, providing enhanced sagittal plane stability without compromising the minimally invasive and single-position advantages of the procedure. Its biomechanical performance in osteoporotic bone suggests it may reduce cage subsidence risk in high-risk patients, potentially decreasing revision surgery rates. Surgeons may consider the NLSLP as an alternative to bilateral pedicle screw fixation to balance stability and invasiveness.

Conclusion

The novel L-shaped side-locking plate effectively improves biomechanical stability in OLIF across varying bone densities, particularly enhancing sagittal plane control while preserving minimally invasive benefits. This design represents a viable fixation option to mitigate cage subsidence and improve surgical outcomes.

References

1. Silvestre et al. 2012 -- Introduction of OLIF technique
2. Abe et al. -- Cage subsidence rates in OLIF
3. Hu et al. -- High cage subsidence rates post stand-alone OLIF
4. Wang et al. -- Biomechanical limitations of two-screw lateral plates
5. Heller et al. -- Bicortical fixation improves screw pull-out strength
6. Giordano et al. -- L-shaped screw configurations enhance shear and rotational resistance