A comparative biomechanical analysis of spinal instability and instrumentation of the cervicothoracic junction: an in vitro human cadaveric model

Stabilization of the cervicothoracic junction is challenging but commonly required in patients with traumatic, neoplastic, congenital, and postlaminectomy conditions. Although extensive research has been performed on stabilization of the cervical spine, there remains a paucity of published data on instrumentation at the cervicothoracic junction. Using 2-column, 3-column, and corpectomy instability models, a biomechanical analysis was performed on the effects of increasing the number of posterior segmental fixation points and/or anterior column reconstruction at the cervicothoracic junction. Multidirectional flexibility testing was performed utilizing a 6-degree-of-freedom spine simulator and 7 fresh-frozen human cadaveric spines (occiput-T6). After intact spine analysis, each specimen was destabilized and reconstructed as follows: (1) C7/T1 2-column injury with posterior instrumentation; (2) C7/T1 3-column injury with posterior instrumentation; (3) C7/T1 3-column injury with anterior interbody cage/plate and posterior instrumentation; and (4) C7/T1 3-column injury plus C7 corpectomy with anterior cage/plate and posterior instrumentation. All reconstruction groups were tested with posterior instrumentation (screws connected by dual-diameter rods) from C5-T1, C5-T2, and C5-T3. For 2-column injuries, there were no statistically significant differences in flexibility (P>0.05), although there was a trend toward reduced flexibility with increasing levels of thoracic fixation. For 3-column injuries, posterior fixation alone resulted in excessive flexibility in flexion/extension even with instrumentation to T3 (P