Mechanical analysis of the human cadaveric thoracic spine with intact rib cage.

The goal of this study was to characterize the overall in-plane and basic coupled motion of a cadaveric human thoracic spine with intact true ribs. Researchers are becoming increasingly interested in the thoracic spine due to both the high prevalence of injury and pain in the region and also innovative surgical techniques that utilize the rib cage. Computational models can be useful tools to predict loading patterns and understand effects of surgical procedures or medical devices, but they are often limited by insufficient cadaveric input data. In this study, pure moments to ±5 Nm were applied in flexion-extension, lateral bending, and axial rotation to seven human cadaveric thoracic spine specimens (T1-T12) with intact true ribs to determine symmetry of in-plane motion, differences in neutral and elastic zone motion and stiffness, and significance of out-of-plane rotations and translations. Results showed that lateral bending and axial rotation exhibited symmetric motion, neutral and elastic zone motion and stiffness values were significantly different for all modes of bending (p<0.05), and out-of-plane rotations and translations were greater than zero for most rotations and translations. Overall in-plane rotations were 7.7±3.4° in flexion, 9.6±3.7° in extension, 23.3±8.4° in lateral bending, and 26.3±12.2° in axial rotation. Results of this study could provide inputs or validation comparisons for computational models. Future studies should characterize coupled motion patterns and local and regional level biomechanics of cadaveric human thoracic spines with intact true ribs.