Healing captured non-dwarven prisoners?

I had previously used lethal weapons to attempt capturing elven merchants, and it always ended up with them missing some limbs. I noticed that after a while, some elven corpses would end up in my refuse pile because they apparently died in the cage (at least I think so since there were no other elven bodies around).

I've since switched to using unarmed combat only, to ensure survival rates of the captured elves, but now they tend to end up with broken limbs and mangled facial features.

Can I somehow heal these non-dwarven prisoners (ie, goblins, humans, etc...) back to full health while they are in cages and/or restrained by chains?