Instability Lumbar Spine

The purpose of this multi-center, randomized, clinical study is to show that the treatment of degenerative lumbar spine with high- or mid-flex rods is not inferior to the treatment with low-flex rods in terms of clinical and safety-related results. The primary aim is to compare the reduction in back pain after the treatment with high- or mid-flex rods with that after treatment with low-flex rods. Secondary, the functionality after treatment with high- or mid-flex rods will be compared to that after treatment with low-flex rods.