• Daniel R Fassett, Ronal Apfelbaum, Rand Clark, Kent N Bachus, and Darrel S Brodke.
• Department of Neurosurgery, University of Utah Medical Center, Salt Lake City, UT, USA.
• Spine. 2005 Nov 15; 30 (22): 2523-9.

Study DesignA biomechanical study on a pneumatically controlled 7-axis spine simulator using Delron and human cadaveric spine models.ObjectivesTo compare the biomechanical properties of an anterior cervical extension plate with comparable-length anterior cervical plates.Summary Of Background DataAdjacent-level anterior cervical surgery next to a previously plated fusion can be technically challenging because of scarring from the previous surgery and the extensive exposure potentially required. An extension plate that attaches to an existing cervical plate could make adjacent-level cervical surgery less problematic.MethodsFlexibility and load sharing were tested in 18 delron models and 10 cadaveric spines. An extension plate (E-plate, Aesculap, Tüttlingen, Germany) at C5-C6 was attached to a single-level plate (ABC plate, Aesculap) at C4-C5 and compared with a two-level plate (ABC plate) spanning C4-C6. Segmental motion was monitored with optical tracking, and interbody graft load was measured with a load cell. Statistical analysis was performed with a Student's t test'.ResultsIn the delron models, both constructs displayed virtually 100% load sharing for the full interbody graft and subsidence models, and range of motion in flexion-extension or axial rotation was not statistically significantly different. The failure mode for the extension plate was lateral bending. In the cadaveric spines, load sharing, range of motion, and stiffness were not statistically significantly different between constructs.ConclusionsThis extension plate appears to be biomechanically equivalent to the ABC cervical plates with which it was compared in this study.

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