Few would have predicted that Tiger Woods would be playing in the P.G.A. Championship this week. He had three failed back surgeries, starting in 2014. He had taken opioids. His astonishing career seemed over.
Then he had one more operation, a spinal fusion, the most complex of all, in 2017. And last month he won the Masters, playing the way he used to.
An outcome like his from fusion surgery is so rare it is "like winning the lottery," Dr. Sohail K. Mirza, a spine surgeon at Dartmouth, said.
The idea behind spinal fusion is to remove a disk — a ring of fibers filled with a nerve-cushioning jelly that joins adjacent spine bones — and fuse the spine together, a procedure that almost inevitably means trading flexibility for stability and, the patient hopes, an existence with less pain.
That was all Woods was looking for when he decided to go ahead with fusion as a last resort — a "normal life" is how he put it. He got that and much more, including a new green blazer, though the lesson that most surgeons say Woods's experience teaches isn't that fusion surgery is a panacea but how much active rehabilitation and physical therapy the procedure requires for it to work.
"If you look at it simplistically, what does fusion do? It provides mechanical support," said Dr. Charles A. Reitman, co-director of the Spine Center at the Medical University of South Carolina. "If they are missing mechanical support and that is the pure cause of the problem, then they will get better."
People with a broken spine, for example, or scoliosis, which is severe spinal curvature, or spondylolisthesis, in which vertebrae slip out of place, tend to have terrific results, he said.
But those are a tiny minority of fusion patients. The vast majority of fusion procedures are performed on patients with one or more degenerated disks, disks that are worn out, dehydrated, stiff and friable. And when those disks move, patients' backs can ache.