I had a spinal fusion a decade ago now and it was one of the worst experiences of my life but absolutely needed as I had a very severe curve (60-70degree S curve at 12).
I was a kid and couldn't advocate for myself. If it is something you want or need, please know the potential side effects as well. I'm in constant pain, I developed torticolitis (head tilt) due to overcompensation for the pain and my doctor refusing to brace me. I lost all flexibility- even outside of my back, lost most of my muscle mass and theres more than just this. I ended up needing PT after as my muscles were looser on one side than the other (didn't help) as I was curling my entire body to the left to try to ease my pain. I was recommended to have a second surgery a year later by my surgeon and at 15, by a surgeon I went to get a second opinion from, as my lower spine, which wasn't touched, flipped. It causes severe nerve pain that will never go away, even if I had had the surgery. That second surgeon also informed me told me I'm likely to develop a limp later in life from it. But a limp was far more worth the risk than the risk of paralysis touching the lumbar spine can cause.
I also have moments where my breathing will cut out which I learned later is because of my spinal fusion. Climate also effects your spine more prominently. I got in a pool the summer (and I live in a warm climate) after my surgery and started to violently shiver as I'd gotten in the shady deep in, not expecting it to make me so, so cold. There's also the fact that the rods can break and you'd have to have the surgery again if you're not careful with what you carry or do.
The recovery is also miserable but know the older you are the worse it will be. So, if you want or need this, sooner is better than later. My grandfather was in his 50s when he had his and his recovery took a lot longer than mine did at 13. It was more painful. It was harder for him to move. And it's already hard to move post-op.
Needless to say, do your research and make the decision you need to make for yourself. This surgery is not one to take lightly. It's hard and can disable people- it did me. It can cause far more issues than I've listed here, admittedly more for just me, but I'm well aware that it was something I needed to do. Had I left my spine to continue curving and twisting into puberty my spine would've started to press more against my heart and lungs. Likely causing heart issues and asthma complications. My biggest piece of advice in regards to this, or any doctor really, is to advocate for yourself. Had I been able to advocate for myself more I'm pretty positive I wouldn't have as many musculoskeletal issues as I do today. I'd still be in pain but not ad much.
I'm sorry if this all sounds scary but as someone who had a surgeon who did me so, so wrong on a surgery as serious as this- I want you to be educated on what it can do as I wasn't.