eeeek horses legs and skin , yes i know about that LOL (not personally but from vet rounds)
I've seen a couple of VERY expensive horses although nothing as fancy as skin grafts, just mulitple weekly vets visits for a couple of months and getting the skin to gradually grow over whilst applying stuff to deter granulation tissue from growing over as that isnt good on the leg in horses apparently
I also seen on tv a few months back fantastic treatment on a tendon injury where they took bone marrow, spun it down to retrieve stem cells and injected them into the tendon, the stem cells grow as they tissue type around them so in this case tendon cells and the injury totally healed whereas had it not had that fancy treatment its competition and possibly riding life was over. Amazing what they can do