Failed back surgery syndrome (also called "failed back syndrome") is a term some doctors use to mean that a person still has pain or other symptoms after they have recovered from back surgery.
There is no surgery that works 100 percent of the time, and surgery on the back is no different. Sometimes the pain is not all gone after surgery, or it even comes back later. Many people who continue to have pain after one surgery will be offered more surgical procedures. The risk of failure of these other procedures is quite high. Before having more surgery, it's a good idea to get a second opinion.
There is no single reason a back surgery is not successful, so there is no specific treatment. Your doctor will work with you to try to find treatments that will help you manage your symptoms and be as active as you can.