• Chandan G Reddy, Michael Magnetta, Nader S Dahdaleh, Matthew Demmer, Kingsley Abode Iyamah, Tae-Hong Lim, James C Torner, and Patrick W Hitchon.
• Department of Neurosurgery, University of Iowa, Iowa City, Iowa, USA.
• Neurosurgery. 2012 Apr 1;70(4):1017-23; discussion 1023.

BackgroundAfter 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.ObjectiveTo compare the biomechanics of an in vitro L1 corpectomy model using 1 rod, 2 rods, or 2 rods with 2 cross-connectors.MethodsEight 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).ResultsAnalysis 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.ConclusionIn 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.

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