Joe Cucolo had a long and successful career with Zimmer Holdings - one of the largest medical device companies in the world, the firm noted.
Rex chairman David Macfarlane said: "We are delighted that Joe has agreed to join the Rex Bionics Board.
"Joe's sales and marketing experience, his track record and his extensive network will be tremendously valuable to the development of our business, especially in the US. I look forward to working closely with Joe and to benefiting from his contribution to our board."
Cucolo said: "The REX Robot is impressive, cutting edge technology for which I see huge potential in the US market. It represents an opportunity to establish a completely new paradigm in neuro-rehabilitation therapy."
Last month, the group said second half sales to end March this year should exceed those in the first half.
Revenue in the six months to the end September totalled £184,000, while the half-year loss narrowed slightly from the year before, to £2.29mln versus £2.37mln.