Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis

• Published in: Bioengineering (Basel) Vol. 10; no. 4; p. 451
• Main Authors: Pan, Jo-Hsi, Chen, Chen-Sheng, Liu, Chien-Lin, Chou, Po-Hsin
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.04.2023; MDPI
• Subjects: Analysis; Back pain; Bioengineering; Biomechanics; CAD; Computer aided design; Contact force; Contact stresses; Defects; Degenerative disc disease; Dynesys stabilization system; Finite element analysis; Finite element method; finite element models; Fixation; Fractures; Intervertebral discs; lumbar spondylolysis; Motion stability; pedicle screw; Pedicle screws; Physiological aspects; Polyethylene terephthalate; posterolateral fusion; Segments; Skin & tissue grafts; Skull; Spinal cord injuries; Spine (lumbar); Surgery; Titanium alloys; Vertebrae; W-type rod fixation; Taiwan; United States > US; pedicle screw; posterolateral fusion; lumbar spondylolysis; W-type rod fixation; finite element models; Dynesys stabilization system
• ISSN: 2306-5354; 2306-5354
• DOI: 10.3390/bioengineering10040451

Lumbar spondylolysis involves anatomical defects of the pars interarticularis, which causes instability during motion. The instability can be addressed through instrumentation with posterolateral fusion (PLF). We developed a novel pedicle screw W-type rod fixation system and evaluated its biomechanical effects in comparison with PLF and Dynesys stabilization for lumbar spondylolysis via finite element (FE) analysis. A validated lumbar spine model was built using ANSYS 14.5 software. Five FE models were established simulating the intact L1-L5 lumbar spine (INT), bilateral pars defect (Bipars), bilateral pars defect with PLF (Bipars_PLF), Dynesys stabilization (Bipars_Dyn), and W-type rod fixation (Bipars_Wtyp). The range of motion (ROM) of the affected segment, the disc stress (DS), and the facet contact force (FCF) of the cranial segment were compared. In the Bipars model, ROM increased in extension and rotation. Compared with the INT model, Bipars_PLF and Bipars_Dyn exhibited remarkably lower ROMs for the affected segment and imposed greater DS and FCF in the cranial segment. Bipars_Wtyp preserved more ROM and generated lower stress at the cranial segment than Bipars_PLF or Bipars_Dyn. The injury model indicates that this novel pedicle screw W-type rod for spondylolysis fixation could return ROM, DS, and FCF to levels similar to preinjury.