i do very focused 3/4 deads on the smith machine...........that bottom part of the movement that this excercise excludes is really where you get hurt...........when your feet are being driven into the floor and jackign your back trying to get it off the ground...........that part of the movement is all ass and legs anyway........i do legs on legday...........the top part of the deadlift is they part that works the thickness of your back, and that what 3/4s on teh smith machine with a focus on the squeeze at the top do
You can do rack pulls for this effect too.
I hurt my back a lot doing deadlifts and switched to rack pulls but now I'm trying to get back into full deadlifts. I feel like they are more effective, especially for my erectors. Using the trap bar is also a good solution. It's easier than a regular deadlift, especially if you use the high handles.
I think a lot of people just don't know how to do deadlifts correctly. You have to keep a neutral spine, or at least very close to it. Moving through a deadlift motion with a neutral spine is tricky for some, natural for others. I'm STILL learning how to do it properly.