Article
Biomechanical comparison of posterior cervicothoracic instrumentation techniques after one level laminectomy and facetectomy
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Published: | September 16, 2010 |
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Outline
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Objective: Posterior instrumentation is the preferred method of fixation in the unstable cervicothoracic junction (CTJ). Several posterior rod constructs of different diameters and configurations are available for instrumentation across the cervicothoracic junction. The objective of this study was to compare the biomechanical stability of various posterior instrumentation techniques that cross the CTJ after a two column injury by complete removal of the posterior elements at C7.
Methods: Eight fresh frozen human cadaveric spines (C3–T4) were used. After the intact spine analysis, each specimen was destabilized (C7 laminectomy and bilateral facetectomies) and reconstructed as follows: Group 1-Posterior instrumentation C5–T2 with a 3.5 mm rod. Group 2- Posterior instrumentation C5–T2 with a transitional rod (3.5 mm to 5.5 mm). Group 3- Posterior instrumentation C5–T2 with side to side rod connector (3.5 mm to 5.5m). All reconstructed groups were tested with posterior instrumentation using the Cervifix system (Synthes Inc. West Chester, PA, USA). We hypothesized that group 2 is the most stable.
Results: Following laminectomy, facetectomy and application of the instrumentation, there was a decrease in range of motion for all the treatment groups compared to the intact spine. This trend was observed in all three planes of motion, but was only significant in right/left lateral bending and flexion (for transitional rod only). Although, the instrumented spines were stiffer than the intact spine in right/left axial rotation, flexion and extension, these differences did not reach statistical significance. Based on observation during the testing, it was evident that in the implanted spines, the majority of the motion that did occur was localized at the segments adjacent to the instrumented levels.
Conclusions: Based on the results of this investigation, the biomechanical stability of the transitional rod, side to side connector ("wedding band") and 3.5 mm rods appear to be similar.