Shores said Marrocco has already been trying to use his hands, although he lacks feeling in the fingers, and he's eager to do more as the slow-growing nerves and muscles mend.
"I suspect that he will be using his hands for just about everything as we let him start trying to do more and more. Right now, we're the ones really kind of holding him back at this point," Shores said.
The infantryman was injured by a roadside bomb in 2009. He is the first soldier to survive losing all four limbs in the Iraq War.
Marrocco also received bone marrow from the same donor to minimize the medicine needed to prevent rejection. He said he didn't know much about the donor but "I'm humbled by their gift."
The 13-hour operation on Dec. 18 was led by Dr. W.P. Andrew Lee, plastic surgery chief at Hopkins.
Marrocco was being released from the hospital Tuesday but will receive intensive therapy for two years at Hopkins and then at Walter Reed National Military Medical Center in Bethesda.
After a major surgery, human nerves regenerate at a rate of an inch per month, Lee said.
"The progress will be slow, but the outcome will be rewarding," he added.