This is a procedure which aims to join two or more vertebrae together with solid bone. The reason is usually to treat or prevent deformity and to treat back pain.
Implants of screws, rods and cages may be used to stabilise the bone while fusion takes place but the fusion process is a biological one which depends on patient factors as well as technical ones. If implants are used for the surgery they act like scaffolding while fusion takes place. If fusion fails to occur then the metalwork may fail causing increased pain. The success of this surgery depends on whether it is being performed for sciatica, leg pain, or back pain. Most surgeons quote a 70% chance of being 70% better with regards to back pain. The chance of improvement of leg pain is likely to be much higher.