I might be a little behind, but I had to study the spinal cord a lot with the last few years, it's one of the major subjects on the Higher Level Biology course. It's a relatively quick operation, but there are an amount and a half of possible side effects and risks with having the operation.
My uncle had to have a similar operation about three years ago, the risk included bad reaction to the anaesthetic, the usual risks with having an operation (infection, super bug, prolonged hospital stay...ect) but also seemed it concerned the spinal cord and a lot of nerves there were also the risks of nerve damage, leading to possible facial disfiguration, problems with mobility. Just a lot of crazy risks that made you wonder did the ends really justify the means.
My uncle went through it, took a good few weeks for him to recover, but he's fine now. I hope Yoshiki takes the time he actually needs to heal. There's not really much point in going through an operation like this with it's risks and evident discomfort and pain, just to rush back into anything and end up back at square one again.
Forget about lives, forget about concerts. Take time out to look after yourself.