Finite element analysis for comparison of spinous process osteotomies technique with conventional laminectomy as lumbar decompression procedure

Purpose: The purpose of this study was to evaluate and compare the biomechani­cal behavior of the lumbar spine after posterior decompression with the spinous process osteotomy (SPiO) technique or the conventional laminectomy (CL) tech­nique using a finite element (FE) model. Materials and Methods: Three validated lumbar FE models (L2‒5) which represented intact spine and two decompression models using SPiO and CL techniques at the L3‒4 segment were developed. In each model, the ranges of motion, the maximal von Mises stress of the annulus fi­brosus, and the intradiscal pressures at the index segment (L3‒4) and adjacent seg­ments (L2‒3 and L4‒5) under 7.5 Nm moments were analyzed. Facet contact forces were also compared among three models under the extension and torsion moments. Results: Compared to the intact model, the CL and SPiO models had increased range of motion and annulus stress at both the index segment (L3‒4) and the adjacent segments under flexion and torsion. However, the SPiO model dem­onstrated a reduced range of motion and annulus stress than the CL model. Both CL and SPiO models had an increase of facet contact force at the L3‒4 segment under the torsion moment compared to that of the intact model. Under the exten­sion moment, however, three models demonstrated a similar facet contact force even at the L3‒4 model. Conclusion: Both decompression methods lead to post­operative segmental instability compared to the intact model. However, SPiO tech­nique leads to better segmental stability compared to the CL technique.