It's been a month since the Boston Marathon bombing killed three people and severely injured about 180. Nearly two dozen survivors lost limbs and are working on a road to recovery. Mayo Clinic plastic and reconstrucive microsurgeon, Brian Carlsen, M.D., says relatively few doctors in the U.S. will ever see patients with blast injuries. He says it takes a team of specialists working together to repair the shattered bones and preserve blood supply, as well as nerve and muscle functions. But even for those whose severe limb trauma is successfully treated, very difficult decisions may lie ahead.