Poster Presentation Sydney Spinal Symposium 2019

Computational analysis on the influence of facet tropism in fixation strategies and implants selection for spinal reconstructive surgery (#35)

Teng Zhang 1 , Siwei Bai 2 , Socrates Dokos 3 , Jason PY Cheung 1 , Ashish D Diwan 4
  1. Department of Orthopaedics and Traumatology, University of Hong Kong, Hong Kong
  2. Department of Electrical and Computer Engineering, Technical University of Munich (TUM), Munich, Germany
  3. Graduate School of Biomedical Engineering, University of New South Wales, Sydney
  4. Spine Service4, St George & Sutherland Clinical School, University of New South Wales, Sydney

In treating recalcitrant low back pain, extreme lateral lumbar interbody fusion (XLIF) with a large cage is reported to have better stability compared to approach of transforaminal lumbar interbody fusion (TLIF) using a small cage. In addition, bilateral pedicle screw fixation (PSF) in comparison with unilateral fixation achieved no inferior fusion rate, but with a significant reduction in operation time and blood loss. The aim of the study was to understand the mechanism underpinning the stability of lumbar interbody fusion using different cage sizes with unilateral or bilateral PSF. A computer model of human lumbar vertebrae L4 and L5 with implants was reconstructed based on CT scans and simulated in Ansys Workbench. Simulation results demonstrated that for either XLIF or TLIF cages, the maximum values of rod stress were comparable with bilateral and unilateral PSF. However, the stability was considerably reduced with unilateral PSF for TLIF due to significantly increased facet joint strain for TLIF; whereas for XLIF with left unilateral PSF, the max facet joint strain was comparable to bilateral PSF, possibly due to facet tropism of this specific subject.