BIOMECHANICAL COMPARISON OF ANTERIOR CASPAR PLATE AND 3-LEVEL POSTERIOR FIXATION TECHNIQUES IN A HUMAN CADAVERIC MODEL

Traumatic cervical spine injuries have been successfully stabilized wi th plates applied to the anterior vertebral bodies. Previous biomechan ical studies suggest, however, that these devices may not provide adeq uate stability if the posterior ligaments are disrupted. To study this problem, the authors simulated a C-5 teardrop fracture with posterior ligamentous instability in human cadaveric spines. This model was use d to compare the immediate biomechanical stability of anterior cervica l plating, from C-4 to C-6, to that provided by a posterior wiring con struct over the same levels. Stability was tested in six modes of moti on: flexion, extension, right and left lateral bending, and right and left axial rotation. The injured/plate-stabilized spines were more sta ble than the intact specimens in all modes of testing. The injured/pos terior-wired specimens were more stable than the intact spines in axia l rotation and flexion. They were not as stable as the intact specimen s in the lateral bending or extension testing modes. The data were nor malized with respect to the motion of the uninjured spine and compared using repeated measures of analysis of variance, the results of which indicate that anterior plating provides significantly more stability in extension and lateral bending than does posterior wiring. The plate was more stable than the posterior construct in flexion loading; howe ver, the difference was not statistically significant. The two constru cts provide similar stability in axial rotation. This study provides b iomechanical support for the continued use of bicortical anterior plat e fixation in the setting of traumatic cervical spine instability.