Fixation and fusion

Spinal fixation represents the gold standard for the surgical treatment of a variety of diseases, including degenerative conditions, deformities, traumas, and tumors. The overall aims are to stop the degenerative process, to provide pain relief through stabilization, and often to promote a solid bony fusion. Fixation and fusion can be achieved by using a variety of approaches and devices, and understanding and managing the biomechanics behind each technique are crucial in determining a clinical treatment’s outcome. This chapter is divided into three sections that deal with pedicle screw fixation, posterolateral fusion, and fusion with intervertebral cages and bone grafts, in that order. In each section, the surgical technique is initially introduced with an explanation of its advantages and their clinical implications; an in-depth description of its biomechanical consequences follows with a discussion of each approach’s effect on spinal stability, kinematics, and load sharing. The state-of-the-art treatments are reviewed to provide a solid basis for understanding how the field of biomechanics is involved in the surgical treatments of degenerative disorders.