(CNN)Zion Harvey was the world's first.
In 2015, the Baltimore boy made history as the first child to successfully receive a double hand transplant. Now, at 10 years old, Zion can use his new hands to perform everyday tasks that other children might take for granted, such as reading and writing, making his lunch and gripping a baseball bat.
"He was able to grip a baseball bat, which was something he wanted to do, by about a year, but now he can do it more powerfully with more coordinated motion between the right and the left hand," said Dr. Sandra Amaral, medical director of the hand transplant program at Children's Hospital of Philadelphia, who was involved in Zion's care.
"Most of his functional outcomes or progress have been really related to doing things more efficiently and effectively," she said. "A few new things that he can do: zip his pants, rip open a granola bar by himself and manipulate it to eat it."
Additionally, Zion can go to the bathroom without any help, said Dr. L. Scott Levin, surgical director of the hand transplantation program at Children's Hospital of Philadelphia, who led the surgery.
"He really has gained tremendous independence, which is what we all strive for in our personal lives," Levin said. "We have restored, even in this little boy, a sense of personal dignity."
Levin, Amaral and 28 other doctors and researchers co-authored a paper describing Zion's history-making surgery and recovery, published in the journal The Lancet Child & Adolescent Health on Tuesday.
While Zion has not achieved any new significant milestones since last summer at the one-year anniversary of his surgery, the authors of the paper wanted to document in the scientific literature that his surgery was a success. Zion and his family were unavailable to comment on the new paper and his progress at the time of publication for this article.
Zion's hands and feet were amputated when he was 2 years old due to a life-threatening sepsis infection that resulted in the failure of multiple organs.
Then, at 8, he underwent a complicated 10-hour surgery in which the hands of a donor were surgically connected to his arms and became his own.
"This isn't the first amazing thing that he's done. He's been doing amazing things since he's been sick. I don't know many adults that can handle half of his life on a day-to-day basis," Pattie Ray, Zion's mother, said in 2015 before his surgery.
Fast-forward to about 18 months later, and "for our case report, he was actually able to write out his name for me to provide photo release consent," Amaral said of the new paper.
The paper reinforces that hand transplantation in a child can be surgically, medically and functionally successful under certain circumstances -- and even life-changing for a family, Levin said.
He said there's one moment immediately after Zion's surgery that he will always remember.
"I spoke to Zion's mom, Pattie Ray, and I said, 'Your little boy has two new hands,' and she just started to hug me and got teary-eyed," Levin said.
"I think (Zion) was a pioneer and his mom was courageous enough to allow us to engage our team to transplant his hands, and the end result, two years later, is a wonderful outcome thus far," Levin said.
After Zion's bilateral hand transplantation surgery, Levin said, his team closely monitored the boy's brain, using MRI and other imaging techniques to assess the progress of his hand function. After all, since Zion was 2, his brain had been used to functioning with no hands. After his surgery, that suddenly changed.
"When we gave him hands and connected his nerves to his new hands, those areas of the brain (that are responsible for hand function) woke up," Levin said, adding that it took only a few months for those brain regions to light up in the brain images.
Zion's bilateral hand transplantation procedure now holds clues to how such surgeries could be performed in other children, something that Levin said is being explored at Children's Hospital of Philadelphia.
Another possible hand transplant candidate is being evaluated, he said.
"So the program is continuing," Levin said. "This kind of transplant is here to stay."
Zion knows that his surgery and recovery have helped doctors prepare for future transplant candidates, and he has been eager to help others, Amaral said.
"He lets us videotape him, and he lets us study his brain, and lots of these tests take hours and hours of time, but he never puts up a fuss about that," she said. "We've talked a lot about how he's kind of the first, but hopefully, there'll be more, and so I think that he's mindful about making sure we get as much information to help others."