VIENNA – Edmund Rath, a 53-year-old from Austria, wants to do simple things such as brush his teeth and slice bread. Most people take such activities for granted but not Rath, who lost his arm just below the shoulder in a truck accident last year that ended his career as a builder. That bad luck was followed by a stroke of fortune. He was chosen by Austrian surgeons as the first person to have a single operation in May to install a click-on prosthesis that the brain controls with signals to the missing hand. The procedure, known as osseointegration (OI), involved implanting a metal rod into the bone of his residual limb.