An in vitro biomechanical comparison of single-rod, dual-rod, and dual-rod with transverse connector in anterior thoracolumbar instrumentation

Chandan G. Reddy, Michael Magnetta, Nader S. Dahdaleh, Matthew Demmer, Kingsley Abode Iyamah, Tae Hong Lim, James C. Torner, Patrick W. Hitchon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

BACKGROUND: After thoracolumbar corpectomy, standard anterolateral instrumentation may consist of dual rods with cross-connectors. However, when the vertebral bodies are small or involved with disease, only 1 rod may be possible. OBJECTIVE: To compare the biomechanics of an in vitro L1 corpectomy model using 1 rod, 2 rods, or 2 rods with 2 cross-connectors. METHODS: Eight fresh frozen human cadaveric spines were potted from T9 to L3. Pure moments of 1.5, 3, and 4.5 Nm were applied, and the motion of the spine was measured using 3 infrared cameras. Loads were applied in flexion and extension, right and left lateral bending, and right and left axial rotation. Each spine was first tested in the intact state. After performing an L1 corpectomy and replacement with a carbon fiber reinforced polymer cage, 3 constructs were tested: single rod (1R), dual rod (2R), and dual rod with 2 transverse connectors (CC). RESULTS: Analysis of variance suggests significant main effects of load (P <.0001), axis (P =.022), construct (P =.0019), and individual spine (P <.0001). Overall, the single-rod construct is significantly less rigid than the intact spine in axial rotation. There is no significant difference between the intact spine and either the dual-rod construct or the dual-rod cross-connector construct. CONCLUSION: In our in vitro model of anterior spinal stabilization after corpectomy and grafting, a single-rod construct is significantly less rigid than the intact spine. Addition of a second rod returns the rigidity of the spine to the intact state. A dual-rod cross-connector construct is significantly more rigid than a single-rod construct.

Original languageEnglish (US)
Pages (from-to)1017-1023
Number of pages7
JournalNeurosurgery
Volume70
Issue number4
DOIs
StatePublished - Apr 1 2012

Keywords

  • Anterior fixation
  • Biomechanics
  • Corpectomy
  • Thoracolumbar spine

ASJC Scopus subject areas

  • Clinical Neurology
  • Surgery

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