I am training for my first marathon (I have done a half and several triathlons) and I have 2 rods to correct my s-curve. I had sciatica this summer which was pain in my hip/lower back area, with a numbing sensation down my leg. This was because I had slacked off on running and started sitting in the lazy boy too much!, and ended up with an inflamed disc pushing on a nerve. The main thing that help with the pain was about once an hour I would lie on my stomach and push up with my hands, keeping my hips as close to the floor as possible (arching the lower vertebraes that were not fused) and relax my buttox. I also received other core strengthening exercises I'm supposed to continue such as crunches and plank, and I use a gym ball. Anyway, it all helped, and now I have no pain, and I never had to stop running to fix it.
Earlier this year I got a bad case of achilles tendonitis and would get shooting pains around my calf and heel, you may want to do a search on that to see if it describes your symptoms more. In both cases I took a mild anti-inflamatory (like alleve) for about 2 weeks and the pain subsided.
As far as the lungs, I haven't felt the caving in, but I do feel like I am limited on how much air I take in...I have trouble taking deep breaths sometimes. But I do feel a lot of pressure between my shoulder blades, where there is also a hook and screw. My pt said some movements can cause a rubbing. I think with mine, it is some muscles getting stronger that I don't usually use, so hopefully the core strengthening will help.
Hopefully this helps! Good luck.
Harrington Rods in 1991 at age 15
Surgery at Scottish Rite in Dallas, TX
Fused from T-4 to L-3