Biomechanics of spine

Spinal disease including primary and secondary tumors occurs in various tissues such as nerve root, blood vessel, spinal cord, and so on. There was about 9.7 patient with spinal tumor in every 1 million. Spine laminectomy has usually been applied in treating the spinal cord tumor. Spinal instability after spine surgery was observed with high occurrence rate, due to excision of posterior structures. Total disc replacement (TDR) is an effective surgical method as well as anterior cervical discectomy and fusion (ACDF) to decompressing neural elements and restore disc height. With regard to keeping cervical spine’s normal kinematics, TDR is more feasible and widely accepted than ACDF for treating degenerative cervical disc disease. It is important to investigate the biomechanical performances of ligament and vertebral on the spine stability in repair surgery, which would provide the theoretical suggestion to disc or cage design. In this chapter, the cervical spine (C2-C7) with lamina repair surgery was studied at C3-C6 segments. The spinal stability in the adjacent segments with posterior ligaments excised was worse than the one with posterior ligament repaired. Repairing or preserving the posterior ligaments in the lamina repair surgery is benefit to spinal integrity and stability. On the other hand, the design of disc and the placement location of it were important factors for the postoperative rehabilitation, especially for the ROM (range of motion) of flexion/ extension and the stress of implant. Therefore, reserving the range of motion and avoiding adverse problems should be taken into consideration, and more attentions also should be paid to a proper implant position along the anterior-posterior direction in ADR surgery.