Low back pain is one of the main public health problems worldwide. When physiotherapeutic treatments fail to resolve the symptoms, a spinal fusion surgery can be the solution. In order to relieve the pain, this surgery aims to stabilize and fuse the vertebrae in the affected region by means of an implant. This thesis presents new insights into the importance of the progression of fusion early after surgery and how these early fusion rates can be improved with biomechanically optimized implants and synthetic bone grafts. The application of these new technologies in the future is expected to result in improved treatment of low back pain with accelerated healing and fewer complications.