This book has become necessary as a consequence of the rapid expansion of the surgical procedures and implants available for spinal surgery within the "AO Group". We have not attempted to write an in-depth book on spinal surgery, but one which will help the surgeon in the use of AO concepts and implants. We con sider the practical courses held all over the world essential for the teaching of sound techniques so that technical complications and poor results can be avoid ed for both the surgeon and, in particular the patient. This book is a practical manual and an outline of what is taught in the courses. It is intended to help the young spinal surgeon to understand the correct use of AO implants. The indi- tions given will aid the correct use of each procedure. . It must be strongly emphasized that surgery of the spine is technically de manding. The techniques described in this book should only be undertaken by surgeons who are trained and experienced in spinal surgery. Certain techniques, in particular pedicle screw fIxation and cages, have not yet been fully approved by the FDA in the United States. However, throughout the rest of the world, the use of pedicle screws has become a standard technique for the spine surgeon, since it has been shown to improve fIxation techniques and allow segmental correction of the spine. The use of cages has become more and more popular, specifIcally as a tool of minimally invasive spinal surgery.