Hi! I'm so happy to see your post, because I have just returned from my best workout yet since surgery. To answer your question quickly before explaining, it is SO WORTH IT to get back surgery. Not only would the scoliosis cause increasing body imbalance and impact your workout routine anyway, but it didn't really get in the way of me maintaining my fitness post surgery. I'm not sure about the 40 lb max after recovery. I am planning on going kayaking soon and could definitely do it now, and I love to hike, though I can't probably put much weight on my back. My surgeon talks like I can do mostly anything after a year, and I've specifically asked about power lifting. I also ran across a power lifter who does his dead lifts, etc, after surgery.
The long version following will explain. Before surgery, I made sure I got in the best shape of my life. I lifted like crazy and ran my head off, and made sure my muscles were big so that when I was recovering and barred from that kind of activity, my body would have more muscle to lose and more cardio fitness to lose, if that makes any sense. After the fact, I read that you should make sure your back muscles aren't huge because they can get in the way during surgery and they just get rearranged and put back in anyway. Oh well.
Anyway, my surgeon was insanely impressed with how well my body recovered and how fast (guaranteed because of my fitness beforehand). He didn't put me in physical therapy because I was already asking about the gym and eager to work out, and he felt confident I could handle it on my own...some people probably think this is a sign of a bad surgeon, but it's rare he recommends this...I say this to stress the importance of being in the best shape of your life before going in because it pays off IN MONTHS AND MONTHS of early recovery. I'm not going to lie--the hospital stay SUCKED. It was really hard to sleep without waking up every 30 min and either throwing up or having to rely on the nurses to turn me, the catheter was yucky, and I was going stir crazy feeling stuck to a bed. Part of this terrible experience is because my body was too small to handle the extreme dosage of pain meds. The next three weeks sucked because of the pain meds literally would not let me hold any food down. But, after three weeks, I went to the doc and he said I shouldn't still be taking pain meds if they were making me throw up, so I stopped, and the throwing up stopped, after some minor withdrawal symptoms. I could definitely deal with the pain at home and could walk around just fine.
My doctor let me go back into the gym at 4ish weeks after surgery to walk at a faster pace, to bike, and I was allowed to do lunge movements and other things I felt my back could handle. At three months, I could do some leg exercises with the ten lb dumbells, lunges, walking lunges.
It's been less then seven months (wow...I just realized this) and I've been doing one-legged lunges and walking lunges with the 20-25 lb dumbbells. I've also been doing leg extensions with limitless weight, calve raises on the leg press machine, and split leg lunge jumps. In February, the surgeon said I could do upperbody lifting with 10 lb. weights max. I've found, though, that bench press doesn't hurt my back no matter what weight I do (100), probably because I'm laying down and not using my back at all. Also, I can finally do overhead tricep extensions (I tried them for the first time again today), dumbbell presses, curls, and I just tried tonight to do pull-ups and dips. No problems there.
Cardio I can do high intensity, but I'm still not cleared to run. I found that the EFX or cross training machine that allows you to up the incline and the resistance is the best workout for me, followed by walking at a very fast pace at the max incline.
For abs, I absolutely cannot do a situp now...it's weird, but my favorites before were the ones I can still do now anyway--the alphabet (where you lie down, put your legs together, put your hands underneath your butt or hold onto something behind your head, and use your abs to move your legs into giant alphabet letters--works wonders) and the plank holds.
I still can't do squats at all nor can I do power cleans or romanian deadlifts (or reg. deadlifts), no big power lifting, but my body looks and feels like it's in shape.
Truth be told, the loss in body fat really made me look like I was in great shape with the muscle mass I put on before surgery. I did lose a lot of muscle--I weighed 20 lb less after surgery and a few weeks at homel, but I've put at least 8 or 9 of it back on. My flexibility isn't too compromised. I can bend past the parallel-to-floor- point and I can touch my toes standing and sitting, but I can't bend as much as before surgery. I don't really notice a HUGE, huge difference though and am still more flexible than some other people around.
I am hoping that my surgeon lets me run this June 1 when I go back even though it's before the year mark by 5 months; we'll see. I know that the fusion needs to be complete before really pushing it.
Sorry for the novel length response. Bottom line: your back will tell you what you can do and when--I can feel what will hurt and what won't before I do it or after I try one rep (like a squat). I hope I answered your question somewhat. I'd be more than happy to discuss anything further. I think getting this surgery is the best thing I've done, even though I miss my old lifts, I can see that I'm almost back there.
Best of luck! I say, go for it! If you love lifting and you are in good shape, you'll be able to lift again, and probably more than 40 lb. Please let me know of any other questions you might have!