This is a very difficult questions to answer. Success means very different things to different people and circumstances. For example, success to a patient with impending paralysis may simply be avoidance of being confined to a wheelchair for the rest of their life. Success to most people means pain relief and restoration of normal activities. This is achieved usually in over 90% of patients who have disc replacements and successful fusions. Success rates drop off in patients who have complications of surgery, patients who have unrealistic expectations, patients who are dependent on strong painkillers, patients who are under the jurisdiction of workers compensation schemes or litigation, patients with osteoporosis or who are frail and medically unwell.