I will disagree with my perpetual friend (who usually has good posts),
Here at Case, we get a lot of spine. I hate spine, so I'd venture to say we get too much. So much so that I think I could fumble my way through an ACDF, ACCF, and do a good job with most posterior lumber cases (decompressions, discectomies, and PSF with instrumentation). Give me about 18 hours and I truly think that I could drop a lung and do an anterior thoracic disk. . . .no promises that the patient could walk post-op though. There are times when one particular attending makes us fumble through cases to the point where I want to give the kerison up just so we can get the case done so I can go home. Ask some of our PGY-2's that have done ENTIRE cervical corpectomies. . . .skin to skin!!!! But spine is one of the things that we're known for.
So there are programs where you can do boat loads of spine. I think most of our Chiefs come out of here being able to do a good job at bread and butter spine. We get 3 fellows/year here and you can tell which ones had a good spine experience in residency. These guys are off an running from day one (i.e. Jefferson guys). With that said, fellowships aren't for doing the simple stuff. You do fellowship to learn how to do the big wacks (complex deformity, traumatic spine, etc.)
In closing, don't be too set on one particular subspecialy going into residency. Pick your residency based on the place that's going to get you the best OVERALL training. The rest will take care of itself. Hope this helps.