A doctor who performed the world's first double-hand transplant on a child says the operation has seen an "outstanding early result".

Zion Harvey (8) underwent the intricate 11-hour operation in July.

A 40-person surgical team used steel screws and plates to fuse together Zion's old and new bones before delicately reconnecting his muscles, nerves, tendons, veins and arteries.

His hands and feet had to be amputated when he was a toddler, after he contracted a serious bacterial infection.

But with the help of prosthetic legs, the schoolboy is able to walk, run and jump like his friends.

He has also learned how to write using his forearms, and was already able to feed himself and play video games before his transplant at The Children's Hospital of Philadelphia.

Zion will need to take drugs which suppress the immune system for the rest of his life - ensuring that the body does not reject his new limbs.

Doctors believed he was an ideal candidate for the operation because of how he was already taking the anti-rejection drugs for a kidney transplant.

"He already had his muscles in his forearm, that once we attach a hand can activate the joints, and the wrist and the fingers and so forth", lead surgeon Dr Scott Levin told the Pat Kenny Show.

"Zion is...a quadrimembral amputee - meaning he had no hands and no legs below the knee - he lost all four limbs to infection".

"This is a historic event because we've demonstrated success in adults - this is the first time this has been attempted with a child, and with an outstanding early result".

On whether Zion will have use of his new hands, Dr Levin said: "I think it's too early to tell".

Dr Scott Levin was the lead surgeon, and is also the director of hand transplantation programme at The Children's Hospital of Philadelphia.

He told the Pat Kenny Show here on Newstalk that Zion is showing great promise.