Stent Screw-Assisted Internal Fixation (SAIF) of Severe Lytic Spinal Metastases: A Comparative Finite Element Analysis of the SAIF Technique

A new stent-screw-assisted internal fixation (SAIF) minimally invasive cement-augmentation technique has been introduced to treat patients with extreme osteolytic lesions of the vertebral body. The aim of the current finite element study, employing a spine model with an extreme osteolytic defect, was to assess the effect of the SAIF technique in reducing strains in the vertebral body in comparison with a standard surgical short posterior fixation. Different finite element models of a L1-S1 spine were developed, representing an intact condition (reference configuration), an extreme osteolysis condition, and its treatment, respectively with stand-alone SAIF, SAIF and posterior fixation, and with stand-alone posterior fixation. Each model was loaded to reproduce standing and upper body bending. Principal strains were calculated on the superior endplate, anterior and posterior cortical walls. A paired Wilcoxon test with a 0.05 significance level was performed to statistically analyze the results. Median strains on the bony structures increased in the osteolysis model compared with the intact model, and the SAIF technique was effective in reducing such strains under both standing and flexion conditions. Additional posterior fixation...Continue Reading