You may find that your dissection group is grateful that there is one less person trying to get in there and cut. Frankly, it is pretty low-yield in my opinion to spend hours and hours dissecting and searching for some nerve when you can just look at it after it has been dissected by an eager scalpel-jockey.
I suggest getting a Rohens atlas, spending a LOT of time with it. Don't do any more work in the lab than you have to especially if your back needs special attention. Drift in after your group has finished the labor, and make sure you can identify everything you need to.
To make up some of the work-load to the group, you can type up outlines of things they need to know (use Chung, and a baby Moore to help with this). Come up with sample test questions for them. You can also make lists of all structures you are responsible for and quiz the group. There are plenty of things you can do so that you are participating without actually hurting your back.
Good luck.