Two years later, Zion continues to adjust well to his new hands. The boy's progress was noted in an article published Tuesday in the Lancet Child & Adolescent Health, the first medical journal report about the surgery, which took place in July 2015.
The report documented the first 18 months of Zion's progress and noted that he is now able to write, feed and dress himself independently.
Within days of the operation, which took more than 10 hours, Zion was able to move his fingers using ligaments from his residual limbs, according to the report.
With “extensive rehabilitation,” Zion tackled one milestone after another. By six months, he could move the newly transplanted muscles in his hands and feel touch; it was around then that he learned to feed himself and hold a pen. By eight months, he could use scissors and crayons.
And within a year, he had achieved one of his original goals: gripping and swinging a baseball bat with both hands.
“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,” Sandra Amaral, medical director of the hand transplant program at Children's Hospital of Philadelphia and the lead author of the Lancet report, told CNN.
“Most of his functional outcomes or progress have been really related to doing things more efficiently and effectively. A few new things that he can do: zip his pants, rip open a granola bar by himself and manipulate it to eat it.”
His progress hasn't come without hurdles. Zion's body has tried to reject his new hands eight times, including “serious episodes” four and seven months after the transplant, according to the report. Zion continues to take four immunosuppression drugs, though doctors hope to reduce those as needed.
Last summer, the hospital released a video marking the first anniversary of Zion's surgery. The 2016 film, “This Is Zion: One Year Later,” included footage of Zion singing, measuring cups of flour in a kitchen and celebrating his ninth birthday with a group of friends at a large party — where he served slices of cake using his own hands.
L. Scott Levin and Benjamin Chang, the two surgeons who led Zion's transplant team, both said last year that they continued to marvel at Zion's emotional maturity, in addition to the physical progress he had made.
“I think from an emotional standpoint, he remains a remarkable young man because here, we've had weeks of hospitalization, a daily request for him to interact, to do therapy, to undergo testing, to interface, and again, there's never been one iota of resistance,” Levin said in the video last year.
At the time, even small movements — holding objects, scratching his nose, shaking hands goodbye — were early indications that Zion's transplant was successful.
“His brain is communicating with his hands. His brain says for his hands to move, and they move,” Levin said in the video. “And that in and of itself is remarkable because, for six years of his life, that part of his brain, if you will, was asleep. There were no hands to activate.”
Zion's transplant and exuberant personality made him a minor sensation after the surgery, when he and his mother, Pattie Ray, appeared on numerous national talk shows. But Zion insisted a year after his surgery that he was “still a kid” whose friends treated him the same as they had before his surgery. The only difference was that he had gained some independence.
“The only thing that's different is, instead of having no hands, I have two hands, and everything else is the same,” Zion said in the 2016 video.
“Now I can get myself dressed without anybody helping me. Now, I can get a snack out the refrigerator without anybody helping me. I can heat up a sandwich and a piece of pizza all by myself. So it feels like I'm there already.”