Biomechanical Comparison of a Novel Facet Joint Fusion Fixation Device With Conventional Pedicle Screw Fixation Device: A Finite Element Analysis.

Purpose: The biomechanics of a novel facet joint fusion device is unknown. The objective of this study is to analyze and compare the biomechanical properties of a novel facet joint fusion device integrated with oblique lateral interbody fusion (OLIF) to those of a conventional pedicle screw fixation device, employing finite element analysis.

Methods: A comprehensive three-dimensional finite element model of the L3-S1 lumbar spine was developed and validated. Based on this model, three surgical groups were created: OLIF combined with the bilateral facet joint fusion fixation (BFJFF + OLIF), unilateral pedicle screw fixation (UPSF + OLIF), and bilateral pedicle screw fixation (BPSF + OLIF), focusing on the L4-L5 level. A torque of 7.5 Nm was applied to simulate vertebral activities under six conditions: flexion, extension, lateral bending (left and right), and axial rotation (left and right). The maximum displacement at the L4-L5 segment was then calculated. The maximum stress values were recorded at the L4-L5 interbody fusion cage and the L3-L4 and L5-S1 segments.

Results: When compared to the other two models, the BFJFF + OLIF model exhibited the smallest maximum displacement value at the L4-L5 segment across all six working conditions. The BFJFF + OLIF model also demonstrated the lowest maximum stress value at the L4-L5 segment interbody fusion cage under flexion, as well as left and right lateral bending and axial rotation conditions when compared with the other models. However, under the extension condition at the L4-L5 interbody fusion cage, the BPSF + OLIF model showed the lowest maximum stress value. At the adjacent L3-L4 segments, the BFJFF + OLIF model registered the lowest maximum stress value during flexion and left lateral bending conditions. At L3-L4, under extension and right lateral bending conditions, the UPSF + OLIF model exhibited the lowest maximum stress value. Under left axial rotation at the L3-L4 segment, both the BFJFF + OLIF and UPSF+OLIF models demonstrated the smallest maximum stress values. Under right axial rotation at the L3-L4 segment, the BPSF + OLIF model recorded the smallest maximum stress value. Concurrently, at the L5-S1 segment, the BFJFF + OLIF model presented the lowest maximum stress value under conditions of flexion, as well as left and right lateral bending and axial rotation. In the L5-S1 segment during the extension condition, the UPSF+OLIF model exhibited the lowest maximum stress value.

Conclusions: This study demonstrates that the novel device, when combined with OLIF, achieves 360° lumbar fusion by fusing the lumbar facet joints, thereby enhancing spinal stability post-fusion. Concurrently, stress on adjacent segments was diminished. The findings suggest that this device may serve as a novel internal fixation method. It may provide a new option for the surgical treatment of patients with low back pain in the future.