Wow, frankenstein thoughts... am I the only one who had the following running through my head:
"Urist McSurgeon has created The Hammer of Fondness, a microcline left foot!"
And in some formerly-invalid dwarf's profile:
"(artifact name), attached to lower left leg"
Moods from surgeons I figured, would at their best, help crippled dwarves get back in the workforce (maybe even make them more capable! I'm sure that enemies would be hard pressed to damage a prosthetic made of something tougher than dwarven flesh.) For a fell/macabre mood, it'd be interesting to see that the guy drags an unwilling dwarf screaming into the hospital, hacks off his arm, and and creates the new prosthetic as the dwarf mercifully passes out from the pain. (If said dwarf is pale or faint, they might not survive the blood loss, and your surgeon might go insane, failing the project because of the dwarf's death)
Of course, I imagine that prosthetics would have limits... you can't replace a hand with a fully functional prosthetic hang, only something like a hook or crude appendage which would have a much less effective grip on stuff (especially since it can't actually grab)... but would serve as an effective melee weapon for soldiers. They're more or less stiff and lifeless... like, one step up from pirate hooks and peg-legs.
I imagine it'd be hard to code in how these actually WORK and count as special bodyparts for the dwarves (as well as figuring out how many bodyparts that item encompasses, in the case that your dwarf's lost his entire left arm and not just a hand), but it's probably no harder than the 'sewing other hands onto your body' idea suggested above.
But imagine the kickass stories we'd be getting when dwarves find themselves with a false arm made of obsidian (that menaces with spikes of nickel silver, and is encircled with bands of rough topaz).
tl;dr version:
- Moody surgeon seeks out a crippled dwarf with a missing limb
- Moody surgeon brings dwarf to hospital
- Moody surgeon designs an artifact prosthetic and attaches it to dwarf in hospital (bringing dwarf back if he's left for some reason, or maybe just seeking him out again)
- Artifact restores limited functionality to previously-crippled dwarf