Clinical studies have reported increased rates of disc degeneration at levels adjacent to fusion. It is believed that eliminating motion through fusion shifts the load to the adjacent levels, causing earlier disc degeneration. This study has shown that significant increases in intradiscal pressure and segmental motion occur at levels adjacent to fusion during normal range of motion. These results may partially explain the mechanism of early disc degeneration at levels adjacent to cervical spine fusion.

Results of this study suggest that it is important to preserve the endplate as much as possible to prevent graft subsidence into the vertebral body, particularly in patients with poor bone quality. It is preferable to make one central hole rather than multiple smaller holes in the endplate for vascularity of the bone graft because it reduces the surface area exposed to fracture stresses.

Chondrocytes in the intact rabbit nucleus pulposus originated and migrated from the cartilage endplate. The chondrocytes changed notochordal nucleus pulposus into fibrocartilaginous nucleus pulposus by depositing fibrocartilage lamellas and fibers in a centripetal direction.

Results of this study demonstrated that the new CaP cement can be injected and infiltrates easily into the vertebral body. It was also found that injection of the new CaP cement can improve the strength of a fractured vertebral body to at least the level of its intact strength. Thus, the new CaP cement may be a good alternative to PMMA cement for vertebroplasty, although further in vivo animal and clinical studies should be done. Furthermore, the new CaP may be more effective in augmenting the strength of osteoporotic vertebral bodies for preventing compression fractures considering our biomechanical testing data and the known potential for biodegradability of the new CaP cement.

The results of this study showed that diagonal transfixation provides more rigid fixation in flexion and extension but less in lateral bending and axial rotation in comparison with horizontal transfixation. Furthermore, greater stresses in the pedicle screws were predicted in the diagonal transfixation model. These limitations of diagonal transfixation should be considered carefully for clinical application.