As someone who has back issues myself I didn't like the way he was moving in the last week of the Giro, some of the shots of him walking after the stages was painful to see. That moment when, after following a bunch of stop-start attacks he was suddenly gone and suffering to me looked like he had tweaked something or had a spasm, even if it was later explained as going into the red/bonking in various media pieces (perhaps more about not admitting the extent of the problem to competitors). It wasn't a suprise to see how he handled the rest of the Giro, just following Martinez at a constant pace rather than going with any sudden accelerations.
If it's true that he has scoliosis (in his case with a leg-length differential too, apparently) then anyone who has had a similar diagnosis can probably guess at what he's been advised: work on core strength, focus on retaining what mobility he still has. Of course the "nuclear" option is spinal fusion of a couple of vertebrae which provides stability at the cost of a permanent loss of some movement, which is what Tiger Woods eventually had but I doubt that's on the table at this point - or what impact it would have on a pro cyclist. I'd assume that he will have to manage this for the rest of his career and it will always hamper him to some extent, sadly, with some periods allowing better performance than others.