"On his right side we did an above-elbow transplant by connecting the bone, muscles, blood vessels, nerves and skin between the donor and recipient," Lee said. On Marrocco's left side, "in order to preserve the elbow joint, we transplanted the entire donor forearm muscles over his remaining tissues, then rerouted the nerves to the new muscle."

While Marrocco is doing well, his recovery will be long and risky, the doctor said. "The nerves regenerate at the maximum speed of 1 inch per month. The therapy will continue for a few years, first at Johns Hopkins, then at Walter Reed. The progress will be slow, but the outcome rewarding."

Marrocco is taking anti-rejection medication, which can lead to side effects like infection and organ damage. But he's received an infusion of the donor's bone marrow cells to further prevent rejection of his new arms. That infusion allows him to take only one anti-rejection drug instead of the usual three-drug cocktail.

Doctors call his recovery so far remarkable.

"Now, I can move my left elbow," Marrocco said. "This was my elbow, the one I had before. I can rotate a little bit. This (right) arm is pretty much not much movement at all -- not yet at least. Hopefully, we are hopeful for the future to get some pretty good function out of it, out of both of them."

Doctors said rehabilitation therapy is an integral part of the healing process. "The next two to three years, Brendan's full-time job is doing hand therapy, six hours a day, every single day, once nerves grow in," said Dr. Jaimie Shores, clinical director of hand transplantation at Johns Hopkins. "He's going to be working very hard."

Marrocco said he's up to the task. The thing he's looking forward to most? "Driving. Absolutely, driving. I used to love to drive and it was a lot of fun for me. So, I am really looking forward to getting back to that. And just becoming an athlete again. One of my goals is to hand-cycle a marathon."

Lee hopes the new anti-rejection regimen performed on Marrocco will become the new standard of care for limb and face transplants. Marrocco will participate in a anti-rejection regimen study that's being funded by the Armed Forces Institute of Regenerative Medicine.

For his family, the surgery means moving forward with their lives.

"Our lives have been on hold for the last almost four years waiting for this surgery, getting him through Walter Reed and getting to the point where he was pretty independent," said mother Michelle Marrocco. "And now he will be independent, and when he comes home, he'll be the Brendan we've all been looking for."