The first child in the world to undergo a double hand transplant has been able to fulfil his dream of swinging a baseball bat.
A Lancet study reveals that the global first has been classed as a success.
Zion Harvey, who underwent the radical surgery at the age of eight, was able to write, feed and dress himself within 18 months of the procedure, researchers found.
And the American child - who lost his hands and feet at the age of two due to a life-threatening sepsis infection - is continuing to receive daily therapy, which could result in further advances.
Before undergoing the 11 hour operation, the young boy was unable to dress, feed and wash himself. Zion told doctors that his ambition was to one day swing a baseball bat.
After achieving this, the child, from Baltimore in Maryland said: "Here's the piece of my life that was missing. Now it's here, my life is complete."
Within days of the US surgery, which involved four medical teams, working simultaneously, the child was able to move his fingers.
By six months, he could move the transplanted hand muscles, and soon after was able to use scissors and crayons, doctors found.
And 12 months after undergoing surgery, the boy was able to fulfil his dream of swinging a baseball bat, using both hands.
The medical report of the case, published in The Lancet Child and Adolescent Health journal, also details a series of setbacks.
On eight occasions, the transplant began to be rejected, which was managed with immunosuppression drug.
The child also suffered minor infections and impairment to his transplanted kidney, the anonymised report notes.
"Our study shows that hand transplant surgery is possible when carefully managed and supported by a team of surgeons, transplant specialists, occupational therapists, rehabilitation teams, social workers and psychologists," said Dr Sandra Amaral, of the Children's Hospital of Philadelphia.
"18 months after the surgery, the child is more independent and able to complete day-to-day activities.
"He continues to improve as he undergoes daily therapy to increase his hand function, and psychosocial support to help deal with the ongoing demands of his surgery."
The surgery took place in July 2015 at Children's Hospital of Philadelphia in collaboration with Penn Medicine.
Researchers said that caution must be taken when assessing the benefits and harms of such surgery, given the need for immunosuppression medication which carries risk for other conditions.
"While functional outcomes are positive and the boy is benefiting from his transplant, this surgery has been very demanding for this child and his family," Dr Amaral said.
In July last year, Chris King became the first person in the UK to have a double hand transplant in a pioneering operation at Leeds General Infirmary.