Biomechanics of lumbosacral spinal fusion in combined compression-torsion loads

Sai Wei Yang, Noshir A. Langrana*, Casey K. Lee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


The current study investigates the stabilizing effects of three different types of spinal fusion to the juxta-free motion segments and to the fused segment of the lumbosacral spine under combined compression-torsion loads. Sixteen fresh human cadaver lumbosacral spines were tested under a simulated physiologic loading condition. The relative movements of the motion segments, as well as the angular rotations and the center of rotation were then computed and analyzed. The average torsional stiffness of the unfused three-motion segment was found to be 2.35 nm/degree. After fusion, the torsional stiffness did not increase significantly. Under the compression-torsional load, the anterior and bilateral-lateral fusions provided adequate stabilizing effect on the fused segment. The posterior fusion provided the least amount of stabilizing effect. These findings are similar to the results of the compres- sion-bending experiment. Whereas the compression- bending loads produced significantly increased stress at the juxta-free segments, the compression-torsional loads did not produce any significant amount of increase in torsional stress at the juxta-free segments.

Original languageEnglish
Pages (from-to)937-941
Number of pages5
Issue number9
StatePublished - Nov 1986


  • Adjacent segment
  • Biomechanics
  • Compression-torsion loading
  • Lumbar spine fusion


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